Conference PaperPDF Available

Enhanced Features of Wind-Based Hybrid Power Plants

Authors:

Abstract and Figures

The objective of this paper is to review and elaborate qualitatively and quantitatively the benefits of wind-based hybrid power plant (HPP) as compared to individual wind/PV power plant. A set of analyses are performed to assess annual energy production/capacity factor, power fluctuations and ramp rates of HPP production and to identify different operating conditions to understand the benefit of combining wind with solar and energy storage in an HPP. The analyses are performed based on spatio-temporally correlated wind power and solar power time series as well as on historical market price time series. Correlation of market price with wind-solar combined time series is exploited to assess the flexibility of having storage by moving the power production to hours where market prices are high from the hours when market prices are low.
Content may be subject to copyright.
Enhanced Features of Wind-Based
Hybrid Power Plants
Kaushik Das*, Anca D Hansen, Divyanagalakshmi
Vangari, Matti Koivisto, Poul E Sørensen
Department of Wind Energy
Technical University of Denmark (DTU)
Risø, Roskilde, Denmark
*kdas@dtu.dk
Müfit Altin
Energy Systems Engineering Department
Izmir Institute of Technology
Urla, Izmir, Turkey
Abstract— The objective of this paper is to review and
elaborate qualitatively and quantitatively the benefits of
wind-based hybrid power plant (HPP) as compared to
individual wind/PV power plant. A set of analyses are
performed to assess annual energy production/capacity
factor, power fluctuations and ramp rates of HPP
production and to identify different operating conditions to
understand the benefit of combining wind with solar and
energy storage in an HPP. The analyses are performed
based on spatio-temporally correlated wind power and solar
power time series as well as on historical market price time
series. Correlation of market price with wind-solar
combined time series is exploited to assess the flexibility of
having storage by moving the power production to hours
where market prices are high from the hours when market
prices are low.
Keywords- Hybrid power plant, wind power, solar power,
energy storage
I. INTRODUCTION
The penetration rates of renewable energy sources (RES),
such as wind and solar, have drastically expanded during
the last years due to increased environmental concerns and
market acceptance [1]. At the same time, the levelized cost
of energy (LCOE) for onshore wind power and the prices
for solar photovoltaics (PV) and storage are sharply
reducing. Furthermore, the maturity of these technologies
has resulted in severe diminution of subsidies and spot
market prices, reducing revenues for renewable generations
[2].
In the last few years, combining different RES, as wind and
solar power with a storage system by leveraging their
complementary nature and operation conditions, has
become a general trend towards improvement of system
efficiency and power reliability. For example, the
variability and power fluctuations of individual RES can be
reduced which is beneficial from the grid point of view.
This facilitates the green transition by providing solutions
to integrate higher penetration of renewable energy.
Moreover, the presence of storage system makes power
curtailment – previously an unthinkable economic burden
for renewables to be a more viable scenario in the future
power systems with large share of renewables in power
grids.
Since the capacity factors of wind and solar power are
generally low, electrical infrastructures like cables,
converters, transformers remain unutilized for a large
portion of time for individual wind or solar power.
Combining wind and solar power provides the opportunity
to optimally utilize these electrical infrastructures,
increasing the annual energy production and thereby
potentially reducing the LCOE. Moreover, seen from wind
power plant developers’ perspective, the idea to combine
wind, solar and storage can enable entrance in new market
for wind power [3], facilitating possible additional revenue
streams, e.g. ancillary services. All these factors motivate
the exploitation of potentials for combining different energy
sources like wind turbine and solar PV with energy storage.
Another benefit of combining wind and solar power from
the system operator’s point of view is better utilization of
grid infrastructure and reduced congestion, thereby
improving security of supply and system stability
A combination of wind and solar power for utility-scale
hybrid power plants (HPP) has been getting global
attention. Furthermore, a global trend is that different
manufacturers are considering over-planting to increase the
use of the already existing infrastructure. Recently, several
industry members have been interested in developing HPPs.
Vestas installed first utility scale wind-solar-battery
Kennedy Energy Park Hybrid power plant in 2018 [3].
India has come out with National Wind-Solar Hybrid
Policy and intends to launch 2.5 GW auction [4]. Juhl
Energy leaded in 2017 a hybrid project in Red Lake Falls,
Minnesota, using two 2.3-116 wind turbines from GE
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
Renewable Energy’s Onshore Wind business supported by
1MW of solar power conversion equipment provided by
GE’s Current business [5]. Siemens Gamesa already
provides hybrid power solutions, which allows for the
integration of one or more renewable power generation
assets with an energy storage system. Their first
commercial On-Grid hybrid project combines a 29 MW
solar system with a 50 MW wind farm and was installed
2017 in India [6]. Vattenfall has their first Hybrid Parks in
operation (solar + wind & wind+ battery) in UK and NL
while wind / solar + battery is under development [7].
A general movement in the industry is to develop utility-
scale wind-based hybrid power plants (HPP) to maximize
the profit from different markets (i.e. capacity market,
energy market and ancillary services market through
optimal design and operation of HPP) as compared to just
minimizing the LCOE.
A plant combining wind, solar and battery energy storage is
referred in this paper, as depicted in Figure 1, as utility
scale co-located grid connected HPP, being characterised
by:
All the assets are owned by the same company so
higher controllability
Motivation is to maximize profit from different
energy markets
Control of electrical load is not of concern of the
plant owner as compared to traditional hybrid
power systems.
It operates as grid integrated power plant unit to serve the
needs of the bulk power system and energy system
environment.
Figure 1: HPP –utility scale co-located grid connected
A utility scale HPP can have the advantages as compared to
an individual technology-based power plant in terms of:
reduction in variability
increase in availability
increase in capacity factor
reduction in cost
increase in revenue
increase in ancillary service capability
increase of lifetime of the wind turbine.
Furthermore, as described in [8], an HPP is also of
providing power smoothing, production loss minimization,
and sudden power injections to help in the frequency
regulation.
However, all these capabilities and advantages are highly
dependent on cost benefit analysis, and thus on grid, market
and available resources at a given location.
To the best of authors’ knowledge, the available literature
on HPP is quite poor in different topics like assessment of
the annual energy production/capacity factor, power
production ramp rates, power fluctuations. Many questions
like, which service to prioritize, how to ensure that the
common grid connection is not overloaded in case of
overcapacity, grid code compliance, which unit should be
curtailed first, will be necessary to answer through thorough
research to enhance the HPP capabilities as attractive
sustainable energy solutions in the next few years.
II. E
NHANCED VALUE OF HPP
To understand the enhanced value of HPP different studies
in terms of capacity factors, variability, curtailment, value
of storage etc. It should be noted that the value of HPP is
enhanced when the evacuation capacity to the grid is
limited. It can be interpreted that for limited grid
connection, maximum weather resources should be used to
generate maximum power close to the evacuation capacity
to maximize revenue. However, since the capacity factor of
wind power is around 30 to 40% and that of solar power is
less than 20%; therefore, the electrical infrastructure
remains unused most of the time. Overplanting with wind
turbines and/or solar panel may be a good option to better
utilize the electrical infrastructure. Three locations in
Europe are chosen to simulate the weather conditions using
CorRES [9] to study the value of HPP over individual wind
power plant (WPP) or solar power plant (SPP). Table 1
below illustrates the capacity factors (CF) for wind and
solar power as well as their correlation for three different
locations in Europe, i.e. a location in Denmark with high
wind/low solar resources, a location in Sweden with low
wind/low solar resources and a location in France with low
wind/high solar resources. Notice the negative correlation
between wind power and solar power in Denmark and
Sweden. The stronger the negative correlation the better
regarding e.g. utilization of the grid connection & balanced
energy output.
Table 1: Capacity factor (CF) and correlation of wind and
solar power
Location Wind
Power
CF [%]
Solar
power
CF [%]
Correlation
Denmark (DK) 42 12 -0.1574
Sweden (SE) 24 10 -0.1206
France (FR) 32 16 0.0097
A. Increase in capacity factor
Increase in capacity factor can be observed when the
evacuation factor is limited, and overplanting is done. In the
following studies, evacuation capacity of 500 MW is
assumed. For different mix of wind and solar power
installed capacity, the capacity factors are calculated.
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
Table 2 Energy and Capacity Factor for different locations when the HPP is overplanted with Solar Power
Overplanting
by Solar
[MW]
Available Energy
[TWh/yr] Energy to grid
[TWh/yr] Curtailed Energy
[TWh/yr] Capacity
Factor [%]
DK SE FR DK SE FR DK SE FR DK SE FR
0 1.844 1.073 1.409 1.844 1.073 1.409 0.000 0.000 0.000 42.1 24.5 32.2
100 1.951 1.169 1.553 1.947 1.168 1.542 0.004 0.002 0.011 44.4 26.7 35.2
200 2.058 1.266 1.697 2.042 1.259 1.660 0.016 0.007 0.037 46.6 28.7 37.9
300 2.165 1.362 1.841 2.133 1.349 1.772 0.032 0.013 0.068 48.7 30.8 40.5
400 2.272 1.458 1.985 2.220 1.438 1.881 0.052 0.021 0.104 50.7 32.8 42.9
500 2.379 1.555 2.128 2.303 1.524 1.985 0.075 0.030 0.144 52.6 34.8 45.3
600 2.486 1.651 2.272 2.382 1.609 2.083 0.103 0.042 0.190 54.4 36.7 47.5
700 2.593 1.747 2.416 2.454 1.690 2.173 0.139 0.058 0.244 56.0 38.6 49.6
800 2.700 1.844 2.560 2.515 1.761 2.247 0.184 0.083 0.313 57.4 40.2 51.3
900 2.807 1.940 2.704 2.566 1.818 2.305 0.241 0.122 0.399 58.6 41.5 52.6
1000 2.914 2.036 2.848 2.608 1.867 2.352 0.305 0.170 0.496 59.5 42.6 53.7
Figure 2 CF for different locations for different mix of wind
and solar installation in an HPP
Figure 2 shows CF for different mix of wind/solar without
overplanting. There is no advantage of mixing solar to
WPP, since the CF is maximum with only wind power
(although land and economic constraints not considered).
Figure 3 CF for different locations for different mix of wind
and solar installation in an HPP with overplanting
Figure 3 shows CF for different mix of wind/solar with
overplanting by 300 MW. It can be observed that again as
expected, the value of overplanting in CF is more
pronounced if overplanted with wind power. However, it
can also be observed that when wind power is dominating
in the mix (left part of the curves in Figure 3), the increase
in CF is not linear. The reason for this is when wind
installation is high, the curtailment required (due to limited
evacuation capacity) is also high. This can be clearly
observed in Figure 4.
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
Figure 4 Available energy, curtailment and energy to grid
for a simulated HPP in Denmark with overplanting
From Figure 2 to Figure 4, it is clear that for the considered
locations it might be beneficial to utilize wind power to
generate power until evacuation capacity and henceforth, it
might be useful to overplant using solar power to minimize
the curtailment and maximum utilize the electrical
infrastructure. It should be noted that detailed cost benefit
analysis needs to be carried out to proper sizing of wind and
solar power in an HPP taking many constraints into account
such as land constraints, economic constraints, grid
constraints etc. However, these studies presented here
provides clear justification for overplanting when the
evacuation capacity is limited.
Table 2 demonstrates annual energy production, curtailed
energy and capacity factor for different values of
overplanting with solar power. It can be observed that with
increasing solar capacity, the capacity factor and annual
energy production increases monotonously. However,
curtailed energy is quite low. The reason for this
is twofold. Firstly, the CF of the solar power is low and
secondly the negative correlation between wind power and
solar power.
B. Reduction in variability
Due to their variable and fluctuating nature, individual RES
is typically challenging the power system as they are driven
by weather conditions and not by demand. The fact that
daily as well as seasonal variability are inherent to both
wind and solar resources may yield to additional stress on
the electrical grid, curtailment of renewable generators and
low or even negative power prices.
Figure 5 Ramp rate of HPP with total installed capacity =
1000 MW and evacuation capacity = 1000 MW
Figure 5 shows that the combination of wind and solar
power reduces the variability (represented by ramp rates) as
compared to individual WPP of same installed capacity.
This is possible for less variability of solar power as
compared to wind power. However, it should be noted that
the cloud covering modelling in the input time series used
for the simulation is rather simplistic and might have
impact on the results (although cloud covering is very
location specific). It can be observed, for example for 10%
of the time the wind power production has a ramp of
200MW/hour – this shows clearly that by mixing wind and
solar photovoltaic units inside an HPP, the variability of the
power is lower than the case when only wind units are
present.
Figure 6 Ramp rate of HPP with total installed capacity =
1000 MW and evacuation capacity = 500 MW
However, this advantage of reduction of variability is
diminished if there is substantial curtailment. Figure 6
shows the ramp rates when the installed capacity is 1000
MW and the evacuation capacity is 500 MW. As expected,
the variability of wind power is reduced due to curtailment.
C. Increase in availability
The availability of wind and solar energy at a given
location strongly depends on weather conditions. By
combining the daily and seasonal complementarity in
generation profiles of these technologies, a higher degree of
annual energy production (AEP) and capacity factor (CF) is
achievable by storing the excess energy production, which
would otherwise be curtailed [3].
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
D. Cost reduction and revenue increase
Combining wind and solar power provides the opportunity
to optimally utilize their electrical infrastructure and thus
reducing the cost developing an HPP infrastructure
(CAPEX). This cost can be furthermore reduced by
installing batteries and PV units in already existing wind
power plants and thus by joint usage of land, electrical
infrastructure (i.e. converters, substation, grid connection)
and the public infrastructure (i.e. access roads). However,
such overplanting by adding new generation and storage
units in already existing infrastructure can overload the
point of common connection. To avoid this, in the
development process of HPP, it is therefore crucial to have
a deep understanding of the electrical infrastructure, site
conditions, grid restrictions as well as interdependencies
and ratio between wind and solar capacity in the given
location. Besides CAPEX, the operational expenses
(OPEX) can also be reduced simultaneous maintenance.
E. Increase in ancillary services capability
The presence of the battery provides the opportunity to
access new markets, facilitating thus additional revenue
streams, such as ancillary services. However, as the value
of the subsidies for wind and solar has strongly decreased
over the years, it becomes more and more crucial for plant
operators and developers to optimize the assets to make
HPP able to participate on the ancillary services market.
Possibility to increase the revenue by providing ancillary
services in addition to the usual energy production has
become an important topic discussed in the literature [3],
[8], [10]. An HPP control and dispatch architecture for
testing enhanced ancillary services on the Lem Kær
demonstrator [1] is discussed in [3]. In [8], control strategy
for HPP is proposed to enable HPP to provide frequency
support in a system with reduce inertia, a large share of
renewable energy, and power electronics-interfaced
generation. For example in [10], it is proposed a day ahead
optimization algorithm to show that there is a potential in
providing ancillary services from all generation units in a
HPP.
However, the research and documentation within this area
is still in a pioneer stage and therefore significant
improvements in the power and revenue forecasting are
needed.
F. Increased dispatchability and flexibility using storage to
maximize revenue from market
As mentioned earlier, overplanting has value in terms of
utilization of electrical infrastructure. However,
overplanting generally will require curtailment. This
curtailment can be reduced using flexible storage
capabilities. Furthermore, the storage also allows to
optimize the dispatch schedule to maximize revenue from
the market.
For example, Figure 7 shows the curtailed power for HPP
with evacuation capacity of 500 MW; installed wind power
of 500 MW and overplanting by solar power of 500 MW.
The peak curtailment is beyond 300 MW in this case.
Figure 7 Curtailed power from HPP with installed wind
power = 500 MW, installed solar power = 500 and
evacuation capacity = 500 MW
Figure 8 Estimated cumulative distribution for curtailed
power
However, the cumulative distribution function shown in
Figure 8 shows that 90% of the time the curtailed power is
less than 20 MW in the simulated scenario. This shows that
the power rating of the storage required is quite low to
reduce the curtailment. Although the energy rating required
for reducing the curtailment is not achievable from this
curve.
Autocorrelation of the curtailment is shown in Figure 9.
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
Figure 9 Autocorrelation function (ACF) for curtailed
power
The ACF shows that the curtailed power has high
autocorrelation for 2-3 hours. This signifies that higher the
energy capacity, more curtailed energy can be captured.
Another important and interesting fact is the correlation of
the curtailed power with energy price. In this regard, the
historical market price from Nordpool market is correlated
with the simulation using historical wind and solar data
simulation. Figure 10 shows the scatterhist plot between
curtailed energy and energy price. It can be observed that
the price is low when high curtailment is done and vice-
versa.
Figure 10 Scatter plot between Curtailed Energy and
Energy price for a considered HPP location in DK
This information is very valuable for the HPP owner
because the revenue can be increased by storing energy
when the spot price is low and discharging the storage at
times of high energy prices.
G. Increase of lifetime of the wind turbine
The lifetime of the wind turbine inside an HPP might be a
relevant research area in the near future. A similar control
approach to that described in [11], could be developed
targeting to increase wind turbine lifetime by minimizing
their loads by using PV and battery whenever it is feasible.
For example, the production responsibility can be taken by
the solar and storage whenever wind turbine loads are high
and weather conditions are permitting this.
III.
CONCLUSIONS
HPPs are sustainable energy solutions in which wind
energy is complemented by solar energy and/or energy
storage. There are multitude of feature enhancements as
compared to individual wind or solar power plants. The
values become more and more pertinent with reduction of
prices for wind and solar technology. The values of HPP
not only lies in the cost reduction and revenue
maximization for HPP owner but also in providing system
services and congestion reduction for power system.
However, the research in utility scale grid connected VRE
based HPP is still in nascent phase and the more flexibility
and benefits need to be explored further.
A
CKNOWLEDGMENT
The authors acknowledge support from the Indo-Danish
HYBRIDize project for this work. This work has been
supported by Danish Innovationsfonden.
R
EFERENCES
[1] I. Lazarov, V. D., Notton, G., Zarkov, Z., Bochev, “Hybrid power
systems with renewable energy sources types, structures, trends for
research and development.,” Int. Conf. ELMA2005, pp. 515–520,
2005.
[2] Ren21 Renewables 2017 Global Status Report. Available online:
http://www.ren21.net/wp-content/ uploads/2017/06/17-
8399_GSR_2017_Full_Report_0621_Opt.pdf (accessed on 6
February 2018).
[3] Petersen et. al., Vestas Power Plant Solutions Integrating Wind,
Solar PV and Energy Storage, 3
rd
Int’l Hybrid Power Systems
Workshop 2018
[4] India to launch 2.5-GW wind-solar hybrid auction,
https://renewablesnow.com/news/india-to-launch-25-gw-wind-solar-
hybrid-auction-614196/, 2018
[5] General Electric Renewable Energy
https://www.ge.com/renewableenergy/hybrid
[6] Siemens Gamesa https://www.siemensgamesa.com/en-int/products-
and-services/hybrid-and-storage
[7] http://integrationworkshops.org/winddublin/wp-
content/uploads/sites/
18/2018/11/1_1_Vattenfall_presentation_Paulina_Asbeck.pdf
[8] Vázquez Pombo, D. Coordinated Frequency and Active Power
Control of Hybrid Power Plants—An Approach to Fast Frequency
Response; Aalborg University: Aalborg, Denmark, 2018.
[9] Koivisto, M. et. al., Using time series simulation tool for assessing
the effects of variable renewable energy generation on power and
energy systems. Wiley Interdisciplinary Reviews: Energy and
Environment, e329, 2019
[10] Ionita C., Raducu A. G., Styliaris N. Funkquist, Optimal Provision of
Frequency Containment reserve with Hybrid Power Plants, 17th
Integration Workshop, Stockholm, Oct. 2018.
[11] Kazda J., Multi-objective wind farm control, PhD report, 2019,
http://orbit.dtu.dk/en/publications/multiobjective-wind-farm-control
(ca90287c-89f7-4a3a-805a-30adbcf06d4d).html
4th International Hybrid Power Systems Workshop | Crete, Greece | 22 – 23 May 2019
... 13,16,19,20 From a power system perspective, a few studies also motivate HPPs by relieving local transmission congestion. 21,22 Although there seem to be foreseen benefits related to HPPs, there is a lack of experience about on-site integrated PV-wind HPPs. 16,21 Traditionally, most of the co-located wind and PV systems have been studied in off-grid settings where the focus is on small-scale generation units. ...
... 21,22 Although there seem to be foreseen benefits related to HPPs, there is a lack of experience about on-site integrated PV-wind HPPs. 16,21 Traditionally, most of the co-located wind and PV systems have been studied in off-grid settings where the focus is on small-scale generation units. 23,24 The purpose has often been to meet a specific demand or to use as a combined source to decrease the dependency on fossil fuel generators. ...
... Das et al. 21 Compare benefits of HPP to solely wind and PV parks. Different mixes of the respective power sources were used to assess the curtailment at different power delivery limits. ...
Article
The interest for co-located wind and solar photovoltaic (PV) parks, also known as hybrid power parks (HPPs), is increasing both in industry and in the scientific community. Co-locating wind and PV can lead to synergies in power production, infrastructure, and land usage, which may lower the overall plant cost compared to single technology systems. This review paper summarizes the existing research on power output modeling related to utility-scale HPPs and identifies knowledge-gaps. The main literature shows that there is a need for improved modeling methodologies accounting for the variability of the combined power production. There is potential for immediate improvement by combining state-of-the-art models that have been developed in separate fields and harmonizing the vocabulary across the different research fields. The study also shows that the total number of peer reviewed studies on utility-scale HPPs is limited and further research, in particular comparative studies, is needed to give a comprehensive view of the benefits and challenges of combining technologies. Other areas such as physical design, control strategies, market participation, and quantification of the possible synergies for physical implementation of HPPs also need to be studied further.
... List of system states 197 Table 8. 2 State machine description for HPP control system 198 xxi List of Tables Table 8.3 IEC 61850 message types and communication requirements [44] 201 Table 8. 4 Identified WAN communication delays between two IEDs for various network scenarios [163] 202 Table 8. 5 Energy analysis for 24-hour test scenario 209 Table 8. 6 Example of economic analysis for 20 year project life assuming permanently high RES power variability 210 Table 9. 1 Main focus points to upscale the proposed kW-scale configuration architecture towards MW-scale off-grid HPPs 219 Table 9. 2 Model parameters for production subsystems 246 Table 9. 3 Model parameters for distribution subsystem 247 Table 9. 4 Economic parameters 252 Table 9. 5 Model parameters for grid-forming inverter 265 Table 9. 6 Model parameters for grid-feeding inverter 266 Table 9. 7 Model parameters for WTG and PVS performance model 267 Table 9. 8 Model parameters for genset 268 Table 9. 9 Dominant state variables associated with critical EV λ cr for various plant operating conditions 272 Table 9. 10 Information exchange between HPP functions and components 274 Table 9. 11 Model parameters for short-circuit studies 278 - The global energy transition has reached a point where renewable energy sources (RES) start to dominate the power generation portfolio in numerous power systems. Non-negligible penetration levels of wind and solar power have stimulated discussions on combining multiple RES and energy storage to construct so-called hybrid power plants (HPP) to balance the available energy capacity and to support the stability of the power system [1,2,3,4]. ...
... List of system states 197 Table 8. 2 State machine description for HPP control system 198 xxi List of Tables Table 8.3 IEC 61850 message types and communication requirements [44] 201 Table 8. 4 Identified WAN communication delays between two IEDs for various network scenarios [163] 202 Table 8. 5 Energy analysis for 24-hour test scenario 209 Table 8. 6 Example of economic analysis for 20 year project life assuming permanently high RES power variability 210 Table 9. 1 Main focus points to upscale the proposed kW-scale configuration architecture towards MW-scale off-grid HPPs 219 Table 9. 2 Model parameters for production subsystems 246 Table 9. 3 Model parameters for distribution subsystem 247 Table 9. 4 Economic parameters 252 Table 9. 5 Model parameters for grid-forming inverter 265 Table 9. 6 Model parameters for grid-feeding inverter 266 Table 9. 7 Model parameters for WTG and PVS performance model 267 Table 9. 8 Model parameters for genset 268 Table 9. 9 Dominant state variables associated with critical EV λ cr for various plant operating conditions 272 Table 9. 10 Information exchange between HPP functions and components 274 Table 9. 11 Model parameters for short-circuit studies 278 - The global energy transition has reached a point where renewable energy sources (RES) start to dominate the power generation portfolio in numerous power systems. Non-negligible penetration levels of wind and solar power have stimulated discussions on combining multiple RES and energy storage to construct so-called hybrid power plants (HPP) to balance the available energy capacity and to support the stability of the power system [1,2,3,4]. ...
... List of system states 197 Table 8. 2 State machine description for HPP control system 198 xxi List of Tables Table 8.3 IEC 61850 message types and communication requirements [44] 201 Table 8. 4 Identified WAN communication delays between two IEDs for various network scenarios [163] 202 Table 8. 5 Energy analysis for 24-hour test scenario 209 Table 8. 6 Example of economic analysis for 20 year project life assuming permanently high RES power variability 210 Table 9. 1 Main focus points to upscale the proposed kW-scale configuration architecture towards MW-scale off-grid HPPs 219 Table 9. 2 Model parameters for production subsystems 246 Table 9. 3 Model parameters for distribution subsystem 247 Table 9. 4 Economic parameters 252 Table 9. 5 Model parameters for grid-forming inverter 265 Table 9. 6 Model parameters for grid-feeding inverter 266 Table 9. 7 Model parameters for WTG and PVS performance model 267 Table 9. 8 Model parameters for genset 268 Table 9. 9 Dominant state variables associated with critical EV λ cr for various plant operating conditions 272 Table 9. 10 Information exchange between HPP functions and components 274 Table 9. 11 Model parameters for short-circuit studies 278 - The global energy transition has reached a point where renewable energy sources (RES) start to dominate the power generation portfolio in numerous power systems. Non-negligible penetration levels of wind and solar power have stimulated discussions on combining multiple RES and energy storage to construct so-called hybrid power plants (HPP) to balance the available energy capacity and to support the stability of the power system [1,2,3,4]. ...
Thesis
Full-text available
The rapidly increasing share of variable renewable energy in power systems has actuated research and development on so-called hybrid power plants (HPP) that combine wind, photovoltaic and storage assets as a physically coupled power-generating facility. From the viewpoint of a wind power plant developer, these hybrid solutions can decrease the levelized cost of energy (LCOE) and help enter new markets for wind power to increase global renewable penetration further. Grid-integrated HPPs can enhance the capability to participate profitably in various electricity markets and to provide grid ancillary services. In rural and remote areas, the potential benefits of a consumer-directed HPP solution are related to grid investment deferral and substitution of costly diesel generation. In such off-grid HPPs, the lack of a dominant voltage source and the high level of variable renewable power and fluctuating consumption is challenging for the control system which must ensure both stable, reliable, secure as well as economical plant operation. This PhD project is focussed on investigating a configurable, scalable and modular off-grid HPP concept which includes the system architecture, control and operational strategies and real-time interoperability between assets. The specific aim is to improve existing and develop new methods for plant sizing, control design and tuning, power and energy management as well as control verification. An vital contribution to elevate the state-of-the-art is to take a holistic approach by examining the mutual effect of the various design stages, which is required to achieve a proof-of-concept on the plant control system. In the first part, a list of high-level use cases and the required functions for the operation of HPPs, in general, is suggested, according to particular business objectives. The main body of the work is devoted to off-grid HPPs that are designed for kW-scale community applications and composed of wind turbines, photovoltaic systems, battery energy storage system and diesel-powered gensets. Overall, the developed tools and methods in this thesis are intended to be suitable to larger plant capacities and modifications in asset portfolio, performance requirements or grid interface. A new methodology to configure generation and storage modules and a scalable plant layout based on the estimated load demand is proposed. The sizing algorithm incorporates both active and reactive power constraints as well as the occurring power losses. The compliance of the proposed configuration architecture with state-of-the-art overcurrent protection techniques is assessed through a post-fault analysis applied to a benchmark HPP. An essential contribution of this project is a model-based design procedure that entails the required building blocks to obtain a stable power management system. A practical guidance is given on dynamic modeling of the plant assets, which utilize state-of-the-art control mechanisms, and the modular composition to an overall HPP model. State-space and discrete-time domain models are developed in parallel to (i) verify the linearized system representation, (ii) carry out comprehensive assessment studies for both small-signal and large-signal stability, (iii) design and parameterize the voltage and frequency control system in all feasible operating states, (iv) evaluate control algorithms through accelerated offline simulations as well as real-time hardware-in-the-loop (RT-HIL) testing. An operational strategy based on the load following principle is advanced by taking into account the forecast uncertainties of renewable generation and load demand. The impact of applying various prediction intervals on the resulting system cost is evaluated. A suitable power dispatch function is developed by considering the operational schedules and the bandwidth of the voltage and frequency controller. The proposed algorithm is robust to modifications in plant layout and grid parameters. The results show its capability of compensating for the variability of renewable generation by properly sharing the active and reactive power among the available units and maintaining the battery state-of-charge within the design limits. The operational performance of off-grid HPPs during N-1 contingencies is studied. An emergency control function is designed for the central coordination of load and generation shedding to prevent system blackout. The implications of reliable plant operation on the initial system design stage are exemplified. The interoperability of the plant control system is demonstrated through a state machine-based architecture which describes the coordination between various power and energy management functions during normal and abnormal system conditions. Finally, control verification through a RT-HIL test platform examines the plant's performance in the presence of communication infrastructure. Moreover, an extended 24-hour test scenario addresses the impact of renewable power fluctuations on battery cycling, which in turn affects its lifetime and the resulting system cost.
... Another benefit of combining wind and solar photovoltaic power from the TSO's point of view is a better utilization of grid infrastructure and reduced congestion: improving security of energy supply and system stability Kaushik Das et. al. [8]. ...
... Another correlation study between DK2 and SE2 wind and solar power plants and capacity factors can be also found at: Table.1 Kaushik Das et. al. [8], where the following results are presented in Table 3 Such simulated VRE time series can be used in addressing the challenges posed by the increasing share of VRE generation. These capabilities will be demonstrated through three case studies: one about the use of large-scale VRE generation simulations in energy system analysis, and two about the use of the simulations in power system operation, planning, and analysis Matti Koivisto et. ...
Thesis
Full-text available
In this 15 ECTS master thesis belonging to the DTU Wind Energy master, a methodology is developed to bid in the day-ahead market for a wind-solar-storage based hybrid power plant with the objective to minimize variability. The input time series and forecast simulations are simulated in CorRES software for two selected regions, one in Denmark (DK2) and another in Sweden (SE2). The efficacy of the developed methodology is analysed through the assessment of hybrid power plant forecast error computation.
... To allow fast growth of VRE integration without being limited by grid reinforcement, one option could be to combine wind and solar generation to optimally utilize the grid resources. Combination of wind and solar is also logical since wind and solar resources are very loosely correlated if not negatively correlated [1]. At the same time, reduction of levelized cost of energy for onshore wind farms is reaching the minimum value. ...
... These benefits among others [1] have increased the focus on development of utility scale wind-PV-storage based hybrid power plants (HPPs) all over the world. Very recently, WindEurope has come up with a position paper on HPP listing all the HPP projects [3]. ...
... Utility-scale hybrid power plants (HPPs) have received global attention due to enhanced controllability and efficient utilization of electrical infrastructure [2]. FC methodologies that enable HPPs to provide enhanced frequency response need to be further investigated, especially since there are additional number of assets and controllers in an HPP as compared to single-technology power plants [3]. However, there is little literature addressing FC of HPPs [4], [5]. ...
Preprint
Full-text available
Frequency control (FC) enables utility-scale grid-connected hybrid power plants (HPPs) to operate in compliance with grid code requirements while to capture value streams from provision of frequency control services (FCSs). In this paper, a novel hierarchical FC approach is proposed to allow HPPs to provide three types of FCSs, namely fast frequency response (FFR), frequency containment response (FCR) and frequency restoration response (FRR). To accommodate state-of-the-art fast FC, controllers for fast FCSs, such as FFR and FCR, are implemented at asset controllers, while controllers for slow FCSs like FRR are implemented at plant controllers or the HPP controller (HPPC). Control counteraction issue, which arises across control hierarchy, is then discussed. To solve this issue, an innovative frequency response observer (FROB) is proposed. Inspired by the concept of disturbance observer (DOB), FROB at plant controllers and the HPPC accurately estimates frequency response initiated at asset controllers, and the obtained estimation is used for control compensation at plant controllers and the HPPC to avoid control counteraction. This scheme achieves robust performance even when there are system uncertainties existing in HPPs, such as parameter uncertainty, unknown control malfunction, and time-varying communication delays. The proposed approach is implemented in a power system dynamic model in MATLAB/Simulink to highlight its effectiveness and robustness.
... Furthermore, seen from wind power plant developers' perspective, the idea to combine wind, solar and storage can enable the entrance into a new potential market for wind power [1], facilitating additional revenue possibilities, i.e., ancillary services throughout the year or even create a standalone grid for dedicated demand in case of certain grid outages. These benefits, among others [2,3], have increased the focus on development of utility scale wind hybrid power plants (HPPs) all over the world. ...
Article
Full-text available
The aim of this paper is to review and compare present European and Indian grid code requirements imposed to hybrid power plants (HPPs) combining wind, solar and storage technologies. Since there are no grid codes specifically for HPPs, the paper will review grid codes for the power plant based on individual renewable technology in the HPP. European grid codes specifies ranges for parameters inside which each national transmission system operators (TSO) has to specify the set of national parameters (Danish specifications in this paper). The comparisons are performed with respect to fault-ride-through capability, frequency and voltage operation ranges, active power control/frequency support as well as reactive power control/voltage support.
... Storage allows WPP to increase the revenue through flexibility and time shifting of the power production. Benefits of dispatchability and flexibility is further pronounced in wind, PV and storage based hybrid power plants (HPPs) [1]. When more and more renewables are integrated in the power systems, the chances of curtailment also increases either from system This work is done as part of Indo-Danish project "HYBRIDize" funded by Danish Innovationsfonden (IFD) security point of view or due to overproduction compared to load. ...
Preprint
Full-text available
div>In order to participate in energy market, variable renewable energy sources need to reduce the uncertainty of forecast errors. Inclusion of storage can be a viable option not only to minimize the penalties due to forecast uncertainties but also to maximize the revenue generation. This paper presents a decision framework for respecting the market constraints and maximise the revenues of a wind and storage power plant. Wind power and price forecast are used in convex optimisation algorithm for making day ahead decisions on battery operation. This day ahead optimisation results feed to an algorithm for operating in the balancing market. Several scenarios and case studies have been simulated to assess the value of storage for revenue maximization of a wind power plant. The results show that proposed algorithms can increase the revenue by more than 10% compared to the operation of wind power plant without battery.</div
... In the case of grid-integrated HPPs, hybridization is justified by the complementarity of renewable resources (wind, solar), and hence a better use factor of the electrical infrastructure (balance of plant). Moreover, synergies in development, installation, and service, as well as enhanced grid ancillary services, lead to an increased business case certainty [1][2][3][4]. In emerging and frontier markets, significant development is predicted toward stand-alone hybrid solutions (i.e., off-grid HPPs) to ensure rural electrification and supplying remote industrial sites (e.g., mining areas) [5][6][7]. ...
Article
Full-text available
The need for simple, but accurate performance models of wind turbine generators (WTGs), photovoltaic (PV) plants, and battery energy storage systems (BESS) for various hybrid power plant (HPP) studies motivates the present work. Particularly, the development and verification stage of HPP controls requires reduced-order models to minimize the complexity and computation effort of simulation platforms. In this paper, such models are proposed, and the most essential parts of the models are validated through field measurements. The models target power system integration studies involving active and reactive power, as well as frequency and voltage regulation where detailed models, as proposed in the standards, can be cumbersome. Field measurements of two Vestas WTGs, one 1-MW PV plant, and one 1-MW/1-MWh BESS are used for model validation. The results show that the WTG and PV performance models correctly estimate the power generation variability according to fluctuations in wind speed and solar irradiance. The BESS performance model provides satisfactory results related to grid-forming control performance and estimation of state-of-charge. The presented validation work enables using the proposed performance models for power system studies and HPP control design in all model-based design stages, that is, preliminary analysis, design, verification, and validation with a high level of confidence.
Article
Full-text available
The concept of hybrid wind power plants (HWPPs) that consist of wind, solar and batteries has received a lot of attention, since HWPPs provide a number of advantages thanks to the complementary nature of wind and solar energy and the flexibility of batteries. Nevertheless, converter-based technologies, as interfaces of HWPPs to the utility grid, contribute to the reduction of total system inertia, making the system more volatile and creating additional threats to frequency stability. To address these operational challenges, the capability of supercapacitors (SCs) to provide fast frequency reserve (FFR) is explored in this paper to enhance the frequency response of the HWPP. Two topologies for integrating SCs into the HWPP are proposed: (1) connecting SC to the DC link of wind turbine (WT) via a DC-DC converter interface, (2) directly connecting SC to the DC link of WT without converter interface. Frequency controllers at the asset level are proposed for these two topologies accordingly. The idea of the proposed frequency controller is to provide frequency response by varying SC voltage in proportion to frequency deviation, namely droop-based FFR. A practical SC sizing method for FFR provision is also discussed. The simulation results have shown, that in the case of frequency event, the proposed frequency controllers for SCs in both topologies positively contribute to the frequency of the system by reducing the rate of change of frequency by at least 5% and improving frequency nadir by at least 10%, compared to the case where the SC has no contribution to FFR. However, the capacitor size requirement for directly connected SC is more demanding in order to achieve the same level of improvement. The performance of frequency support has been highly related to total system inertia and control parameters. Therefore, any change to the severity of frequency events or control parameters calls for the reevaluation of the capacitance.
Article
In order to participate in energy market, variable renewable energy sources need to reduce the uncertainty of forecast errors. Inclusion of storage can be a viable option not only to minimize the penalties due to forecast uncertainties but also to maximize the revenue generation. This paper presents a decision framework for respecting the market constraints and maximise the revenues of a wind-storage based hybrid power plant. Wind power and price forecast are used in convex optimisation algorithm for making day ahead decisions on battery operation. This day ahead optimisation results feed to an algorithm for operating in the balancing market. Several scenarios and case studies have been simulated to assess the value of storage for revenue maximization of a wind power plant. The results show that proposed algorithms can increase the revenue by more than 10% compared to the operation of wind power plant without battery.
Conference Paper
Full-text available
This paper addresses a value proposition and feasible system topologies for hybrid power plant solutions integrating wind, solar PV and energy storage and moreover provides insights into Vestas hybrid power plant projects. Seen from the perspective of a wind power plant developer, these hybrid solutions provide a number of benefits that could potentially reduce the Levelized Cost of Energy and enable entrance to new markets for wind power and facilitate the transition to a more sustainable energy mix. First, various system topologies are described in order to distinguish the generic concepts for the electrical infrastructure of hybrid power plants. Subsequently, the benefits of combining wind and solar PV power as well as the advantages of combining variable renewable energy sources with energy storage are elaborated. Finally, the world's first utility-scale hybrid power plant combining wind, solar PV and energy storage is presented.
Conference Paper
Full-text available
The article deals with the state of the art of a hybrid power systems with renewable energy sources (HSRES). These systems are classified according to different criteria. It has been made a short review of the current state of their design, modelling, simulation and optimisation. The respective analysis has been made also. In conclusion, it has been made a summary of the future trends for research and development.
Article
The increasing share of variable renewable energy (VRE) generation poses challenges to power systems. Possible challenges include adequacy of reserves, planning and operation of power systems, and interconnection expansion studies in future power systems with very different generation patterns compared to today. To meet these challenges, there is a need to develop models and tools to analyze the variability and uncertainty in VRE generation. To address the varied needs, the tools should be versatile and applicable to different geographical and temporal scales. Time series simulation tools can be used to model both today and future scenarios with varying VRE installations. Correlations in Renewable Energy Sources (CorRES) is a simulation tool developed at Technical University of Denmark, Department of Wind Energy capable of simulating both wind and solar generation. It uses a unique combination of meteorological time series and stochastic simulations to provide consistent VRE generation and forecast error time series with temporal resolution in the minute scale. Such simulated VRE time series can be used in addressing the challenges posed by the increasing share of VRE generation. These capabilities will be demonstrated through three case studies: one about the use of large‐scale VRE generation simulations in energy system analysis, and two about the use of the simulations in power system operation, planning, and analysis. This article is categorized under: • Wind Power > Systems and Infrastructure • Energy Infrastructure > Systems and Infrastructure • Energy Systems Economics > Systems and Infrastructure
Coordinated Frequency and Active Power Control of Hybrid Power Plants-An Approach to Fast Frequency Response
  • D Vázquez Pombo
Vázquez Pombo, D. Coordinated Frequency and Active Power Control of Hybrid Power Plants-An Approach to Fast Frequency Response; Aalborg University: Aalborg, Denmark, 2018.
Optimal Provision of Frequency Containment reserve with Hybrid Power Plants, 17th Integration Workshop
  • C Ionita
  • A G Raducu
  • N Styliaris
  • Funkquist
Ionita C., Raducu A. G., Styliaris N. Funkquist, Optimal Provision of Frequency Containment reserve with Hybrid Power Plants, 17th Integration Workshop, Stockholm, Oct. 2018.
Multi-objective wind farm control
  • J Kazda
Kazda J., Multi-objective wind farm control, PhD report, 2019, http://orbit.dtu.dk/en/publications/multiobjective-wind-farm-control (ca90287c-89f7-4a3a-805a-30adbcf06d4d).html