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Power Electronics Intelligence at the Network Edge (PINE) – An Approach to Interface PV and Battery Energy Storage Systems at the Grid Edge
Abstract
In this paper, a self-organizing power electronic converter with control intelligence at the edge of the distribution network is proposed. The proposed converter is called Power Electronics Intelligence at the Network Edge (PINE), it has the potential to add intelligence at the network edge to the electricity delivery system of the present and in the future. The proposed approach consists of a power electronic converter (rectifier/dclink/ inverter) termed as PINE to supply residential loads. The rooftop solar and battery energy storage system is connected to the dc-link. With the bidirectional characteristic of the PINE, the load voltage is regulated via feedback, while input distribution voltage can be allowed to vary in a range. This type of configuration allows for control of input power factor to be unity, reactive power to be injected at the grid edge to regulate the voltage and also enable energy budgeting, i.e. limit the amount of power to the residential load under disaster situations. With the PINE converter at the distribution edge that can communicate with other PINEs as well as to the distribution system operator, intelligence at the distribution edge can be established. Such a system has many advantages that are discussed in the paper. Further, impacts of increased penetration levels of PINE are shown using a test feeder based on the IEEE-37 test node feeder. Simulation and experimental results on a laboratory prototype system validate the PINE converter concept.
... In a recent study [25], a self-organizing power electronics converter ( Fig. 3) with control intelligence at the edge of the electric distribution network has been introduced. The proposed system, called Power Electronics Intelligence at the Network Edge (PINE), shown in Fig. 3, consists of three main stages: a front-end PWM converter that reduces current harmonics and maintains constant dc-link voltage, rooftop solar PV/Battery system connected to the dc-link and an output PWM converter that feeds the load. ...
... To study the behavior of multiple PINE converters connected in a distribution network (Fig. 4), an average model for an individual converter is developed. The average model is exercised on a test feeder based on the IEEE-37 test-node feeder [26], as shown in Fig. 4. A detailed study of this concept is available in the reference [25]. ...
In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.
... Integration of energy storage is typically considered at the grid-scale [9][10][11] or with a renewable generation facility. [12][13][14][15][16] However, this requires large storage capacities to effectively manage energy supplydemand fluctuations. For instance, to enable 20% renewable penetration in the grid, an estimated storage capacity of 200 GW/1000 GW h would be required to provide peak shaving capabilities. ...
Increasing renewable energy requires improving the electricity grid flexibility. Existing measures include power plant cycling and grid-level energy storage, but they incur high operational and investment costs. Using a systems...
... Likewise, [18] and [19] have explored the areas of reactive power control and harmonics mitigation. A battery-based active power curtailment and an intelligent reactive power injection are discussed in [20]. Reference [21] extends the PV-battery system for electric vehicle charging and improves the reactive power control. ...
This paper proposes a grid-tied photovoltaic (PV) inverter capable of low-voltage ride through (LVRT), reactive power support, and islanding protection. Unlike other LVRT in-verters, the proposed inverter is independent of sag severity while maintaining the maximum power-point tracking (MPPT) under normal and faulty conditions. The addition of an energy storage buffer stage mitigates the DC-link voltage surge during sags. At the same time, the inverter injects the reactive power during back-to-back sags of variable depths. The control system of the inverter generates the appropriate reference signals for normal, LVRT, and anti-islanding modes while the MPPT continues running. The salient features of the proposed inverter are: ① active power injection under normal grid conditions; ② sag-depth independent LVRT with reactive power support; ③ no DC-link fluctuations; ④ continuous MPPT mode; and ⑤ simultaneous LVRT and anti-islanding support during a grid out-age. The inverter demonstrates an uninterrupted operation and seamless transition between various operating modes. Simulations and the experimental prototype have been implemented to validate the efficacy of the proposed PV inverter. Index Terms-Low-voltage ride through (LVRT), Sag, maximum power point tracking (MPPT), single-phase photovoltaic (PV) inverter, PV-battery system.
... In this way, many DC generation RESs may be consumed flexibly by local loads, increasing the energy conversion efficiency and selfconsumption [2], [3]. Such a hybrid grid architecture is also in alignment with the intelligent power conversion and the near-zero-energy building initiatives [4], [5]. ...
This letter proposes an interlinking converter architecture, which enables flexibly integrating renewable energy into hybrid grids. The proposed converter has one AC port and two DC ports, offering a flexible solution to integrating various DC and AC sources, which can also be versatilely configured as a DC-DC converter, a DC-AC inverter, or a DC-DC/AC multiport converter. The general concept of the architecture, its common-mode voltage analysis and flexible operation modes are detailed in this letter. Experimental tests are performed on an example converter with a dedicated modulation strategy. The test results confirm the concept in terms of flexible conversion, high power density, low leakage currents as well as controllable power flow.
With the rise in global warming, distributed generators (DGs) based on renewable energy sources have become increasingly important in the power sector. Due to their small size and the capacity to 'island' while providing most of their loads during situations, microgrids provide an excellent framework to build smart grids, which increases system resilience. Given that renewable-based DGs dominate microgrids and are defined by their statistical properties and unpredictable power, sustaining load-generation balance is a significant challenge. Although microgrids are now widely used and researched, there is still considerable contention over whether they should use alternating current (AC) or direct current (DC), with the majority opinion leaning toward a combination of the two. nIn order to facilitate the flexible incorporation of renewable energy into hybrid grids, this article offers an interlinking converter design. The suggested converter may be configured as a DC-DC converter, a DC-AC inverter, or a DC-DC/AC multiport converter thanks to its one AC port and two DC ports, making it a versatile option for combining multiple DC and AC sources. Flexible conversion, high power density, low leakage currents, and tunable power flow are all features validated by the MATLAB/SIMULINK simulation results, proving the idea.
—Information generated by people and the gadgets today
has gone from deficient to abundant which has increased the
complexity of data. The challenge is how to elicitate, manage and
organize this big data. The actual thing is to find out which data is
important, what to keep and what to discard, and where to keep this
enormous amount of data. The volume of data gets expanded when
data is linked with other, resulting in data integration. Big data is
still viewed as conventional data which is not sufficient. It should
focus on what value the data can create into analytics rather than
what technology it brings. Today due to digital convergence we have
an opportunity and a challenge both to influence the creation to
facilitate later linkage and to automatically link previously created
data. This paper focuses on big data analytics, the challenges and
opportunities it accelerates and how it could be magnified to base the
analytics.
This article discusses the application of battery energy storage systems (BESSs) as power redistributors in three-phase distribution grids as an add-on functionality to typical BESS applications, such as congestion management and energy arbitrage. Combining those ancillary services into a single power unit is not yet performed in practice but may constitute an emerging business opportunity to increase the BESS revenues. The unbalanced operation of the BESS voltage source converter (VSC) leads to the circulation of low-frequency current harmonics in the dc-link through the capacitors and the battery cells. Therefore, it is particularly interesting whether relatively large 50- and 100-Hz currents can safely circulate within these components. Analytical modeling and design guidelines for the dc-link of a three-leg four-wire two-level VSC operating under unbalanced loads are detailed. Furthermore, a low-power VSC prototype is used to demonstrate the working principle of the BESS, providing power unbalance redistribution and symmetric power exchange. Additionally, the ICR18650-26F Lithium-ion cells are cycled to reach end-of-life with different current profiles and C-ratings. The analysis shows that charging with a 100 Hz ripple superimposed to the dc current leads to a 10% increment in degradation.
Smart low-voltage distribution system (LVDS) is an essential component in realizing smart electricity grids. In countries like India and other energy-deprived regions of the world, researchers are looking for a holistic approach to integrate millions of small Renewable-powered homes in the LVDS and make the system smart. Restructuring the existing distribution system to form clusters of microgrids is an important step in achieving a smart LVDS. The realization of microgrids in LVDS can take different shapes in different countries depending on the structure of the distribution grid. This article envisions a possible approach to implement microgrids in a smart LVDS with radial distribution.
This article presents the topology and control of a three-port energy gateway (EG) for hybrid ac/dc nanogrids. The simple hardware architecture allows connecting renewable energy generators, energy storage (ES) devices, such as ultracapacitors, and the utility grid through three different interface converters, which, altogether, define the three-port EG of the nanogrid. The proposed EG represents a tradeoff between circuit complexity and controls flexibility, allowing: 1) operation of the ES port over a wide voltage range; 2) control of the local dc-bus voltage at a predefined set-point; 3) multidirectional power flow; and 4) support of the local ac-bus voltage with the possibility to transition into islanded operation. A hierarchical control strategy is presented that enables flexible power exchange between the ac and dc buses. At the top of the control hierarchy, a human-machine interface is dedicated to operation mode selection and parameter preset; then, a supervisory control layer is present for system-level monitoring and control functions; the lower layer of the hierarchy is constituted by converter control functions for power flow regulation, achieved leveraging on voltage and current controllers. The flexibility and effectiveness of the proposed EG architecture, control, and implementation are demonstrated in this article in a variety of operation modes by means of experimental results.
Renewable photovoltaic (PV) energy is a primary contributor to sustainable power generation in microgrids. However, PV grid-tied generators remain functional as long as the grid voltage and the input PV source remain normal. Abnormal conditions like transient grid sags or solar irradiation flickering can make the grid-tied inverter go offline. Simultaneous shut down of PV generators residing in the distribution grid may lead to an overall grid instability or outage. Therefore, PV generators must be equipped with fault-ride-through mechanisms in order to remain connected and operational during faults. This paper presents a PV-inverter with low-voltage-ride-through (LVRT) and low-irradiation (LR) compensation to avoid grid flickers. The single-phase inverter rides through the voltage sags while injecting reactive power into the grid. The proposed control strategy ensures a steady DC-link voltage and remains connected to the grid during AC-side low voltage and DC-side low-irradiation faults. Unlike other PV inverters, the controller maintains the maximum-power-point-tracking (MPPT) in all conditions. LVRT, constant power output, and robust MPPT are the noticeable features of the proposed system. Frequency analysis, simulations, and a laboratory prototype validate the proposed control strategy.
em>Realizing a smart Low Voltage Distribution System (LVDS) is essential to realize a smart grid. Restructuring the existing distribution system into microgrids is one important requirement to achieve a smart LVDS. The realization of microgrids in LVDS can take different shapes in different countries. This article discusses the challenges and practical solutions to realize a smart LVDS for radial distribution grids, which are common in India. The network following a distribution transformer can be distinguished as a microgrid for radial low voltage distribution grids. However, this leads to many operational issues. Therefore, this article envisions replacing the Low Voltage distribution transformers with Solid-State Transformers (SSTs). This will enable the LVDS to control the power exchange between the phases within a microgrid as well as power exchange between different microgrids. The architectural design of a smart home in smart LVDS is outlined to complete the discussion. Various unique features required for smart inverters in a smart home and existing grid codes to make them compatible with smart LVDS are also reviewed. </i
em>Realizing a smart Low Voltage Distribution System (LVDS) is essential to realize a smart grid. Restructuring the existing distribution system into microgrids is one important requirement to achieve a smart LVDS. The realization of microgrids in LVDS can take different shapes in different countries. This article discusses the challenges and practical solutions to realize a smart LVDS for radial distribution grids, which are common in India. The network following a distribution transformer can be distinguished as a microgrid for radial low voltage distribution grids. However, this leads to many operational issues. Therefore, this article envisions replacing the Low Voltage distribution transformers with Solid-State Transformers (SSTs). This will enable the LVDS to control the power exchange between the phases within a microgrid as well as power exchange between different microgrids. The architectural design of a smart home in smart LVDS is outlined to complete the discussion. Various unique features required for smart inverters in a smart home and existing grid codes to make them compatible with smart LVDS are also reviewed. </i
Photovoltaic embedded generation in low voltage AC networks is quite popular, however despite its benefits there are some problems especially when Photovoltaic (PV) penetration exceeds certain thresholds. Among others, voltage violation is of prime importance. Our review of the literature focused on PV penetration limits due to voltage violations in Low Voltage (LV) networks. The review revealed that voltage violations can occur at a penetration level as low as 2.5% when a large Distributed Generator (DG) is installed at a single point. Alternatively, a Low Voltage (LV) network can host a large number of Photovoltaic Distributed Generators (PVDGs), with a penetration level up to 110% if evenly distributed over shorter lengths. However, an LV network has no rules of thumb for safe penetration limits. Penetration level calculations have been found that used numerous approaches, which we have analyzed and discussed to adopt a more rational and unified approach. Our literature review revealed that, in LVs, a very high penetration level can be achieved as compared with Medium Voltage (MV) networks. However MV voltage level control problems impose a limit for PV hosting in LV networks. There is a need to evolve strategies for robust voltage control at the MV level and to develop certain rules of thumb for PV penetration limits in LV networks independent of the MV level, to increase the PV hosting capacity.
This paper focuses on the most common PV-storage architectures that are designed for residential applications and that incorporate storage devices like batteries, hydrogen systems, supercapacitors, and flywheels. The main motivations and a comparison of the advantages and disadvantages of the architectures are presented. Moreover,some common approaches to performing intelligent power management are introduced
This paper describes development of a three-phase unbalanced distribution network test case, considering primary and secondary level distribution systems. Primary feeders, lateral feeders, and secondary feeders are modeled from the substation transformer to the house level based on the network's physical hierarchical structure. Researchers can use the developed benchmark for test case analysis and to address issues associated with integration of rooftop photovoltaics (PVs) and distributed energy resources (DER) in existing unbalanced networks, including incremental power losses, voltage violations, voltage fluctuations, volt/var control, and other power quality concerns.
This paper deals with design of a synchronous frame control strategy for single-phase inverter-based islanded distributed generation (DG) systems. Although, implementation of these regulators requires a minimum of two independent phases in the system, the required orthogonal phase is generated through the use of a first order all pass filter (APF). The essence of the proposed control strategy is to use a synchronous reference frame PI (SRFPI) controller to regulate output voltage, together with a simple inner capacitor current regulating loop to stabilize the system and a voltage-feedforward loop to improve the system robustness. A detailed design criterion for the proposed control strategy is presented base on a frequency-response approach. Finally, simulation results are presented to validate the proposed method.
The intent of the study detailed in this paper is to demonstrate the benefits
of inverter var control on a fast timescale to mitigate rapid and large voltage
fluctuations due to the high penetration of photovoltaic generation and the
resulting reverse power flow. Our approach is to formulate the volt/var control
as a radial optimal power flow (OPF) problem to minimize line losses and energy
consumption, subject to constraints on voltage magnitudes. An efficient
solution to the radial OPF problem is presented and used to study the structure
of optimal inverter var injection and the net benefits, taking into account the
additional cost of inverter losses when operating at non-unity power factor.
This paper will illustrate how, depending on the circuit topology and its
loading condition, the inverter's optimal reactive power injection is not
necessarily monotone with respect to their real power output. The results are
demonstrated on a distribution feeder on the Southern California Edison system
that has a very light load and a 5 MW photovoltaic (PV) system installed away
from the substation.
This paper presents an active decoupling technique for a dual phase output inverter with an integrated power optimizer for off-grid applications. The proposed method employs a half bridge with passive elements (L-C) to balance the output and actively compensate for twice the frequency power ripple in the dc-link. The closed loop control adjusts for varying load conditions. Further, an integrated power optimizer (PO) provides interface of solar-pv and battery to the dc-link. The PO stage (half bridge) is controlled such that maximum power point tracking (MPPT) is achieved for the connected pv-array and independent charge/discharge functions of the battery. Simulation and experimental results verify the performance of the proposed technique under balanced, unbalanced load, non-linear conditions as well as fault condition.
In this paper, an isolated bidirectional series resonant converter is proposed for transportation applications such as mid-size electrified airplanes. The proposed converter is capable of transferring the nominal power in both directions, either from the high voltage side to the low voltage side (step-down mode), or from the low voltage side to the high voltage side (step-up mode). Using time-domain analysis it is shown that the converter transfers full power over the entire range of terminal voltages with guaranteed soft switching for all the voltage and power levels. No extra components, active or passive, is used for soft switching. Effectiveness of the modulation scheme in achieving zero current switching was experimentally confirmed.
In this paper, a control strategy for power flow management of a grid-connected hybrid photovoltaic (PV)-wind-battery-based system with an efficient multi-input transformer-coupled bidirectional dc-dc converter is presented. The proposed system aims to satisfy the load demand, manage the power flow from different sources, inject the surplus power into the grid, and charge the battery from the grid as and when required. A transformer-coupled boost half-bridge converter is used to harness power from wind, while a bidirectional buck-boost converter is used to harness power from PV along with battery charging/discharging control. A single-phase full-bridge bidirectional converter is used for feeding ac loads and interaction with the grid. The proposed converter architecture has reduced number of power conversion stages with less component count and reduced losses compared with existing grid-connected hybrid systems. This improves the efficiency and the reliability of the system. Simulation results obtained using MATLAB/Simulink show the performance of the proposed control strategy for power flow management under various modes of operation. The effectiveness of the topology and the efficacy of the proposed control strategy are validated through detailed experimental studies to demonstrate the capability of the system operation in different modes.
This paper presents a family of new multiport power-sharing converter (PSC) topologies for utility-scale fuel cell (FC) power generation. The proposed system connects multiple FC sources to a medium-voltage grid via a single multilevel neutral point clamp (NPC) inverter interface with high-frequency isolation. High-voltage series-connected inputs are achieved, despite safely referencing each source to ground. Also, unique power-sharing technology decouples series-connected source currents and enables control of each FCs individual power level. Multidimensional modeling and analysis of the proposed system's PI- and PV-behavior is presented. Then, system topology and design considerations are discussed. Case study simulations show how this topology can operate four 250-kW FCs at separate power levels between 20% and 100%, while connecting to a single three-level NPC utility-interface. Correspondingly, a reduced-scale hardware prototype provides further proof of concept. Altogether, the proposed family of multiport PSC topologies realizes independent power control per source as well as increased output power, operational flexibility, thermal balancing, source availability, and cost effectiveness for utility FC power generation.
Energy and sustainability issues raise a large number of problems that can be tackled using approaches from data mining and machine learning, but traction of such problems has been slow due to the lack of publicly available data. In this paper we present the Reference Energy Disaggregation Data Set (REDD), a freely available data set containing de-tailed power usage information from several homes, which is aimed at furthering research on energy disaggregation (the task of determining the component appliance contributions from an aggregated electricity signal). We discuss past ap-proaches to disaggregation and how they have influenced our design choices in collecting data, we describe the hardware and software setups for the data collection, and we present initial benchmark disaggregation results using a well-known Factorial Hidden Markov Model (FHMM) technique.
The field of power electronics is concerned with the processing of electrical power using electronic devices [1–7]. The key element is the switching converter, illustrated in Fig. 1.1. In general, a switching converter contains power input and control input ports, and a power output port. The raw input power is processed as specified by the control input, yielding the conditioned output power. One of several basic functions can be performed [2]. In a dc-dc converter, the dc input voltage is converted to a dc output voltage having a larger or smaller magnitude, possibly with opposite polarity or with isolation of the input and output ground references. In an ac-dc rectifier, an ac input voltage is rectified, producing a dc output voltage. The dc output voltage and/or ac input current waveform may be controlled. The inverse process, dc-ac inversion, involves transforming a dc input voltage into an ac output voltage of controllable magnitude and frequency. Ac-ac cycloconversion involves converting an ac input voltage to a given ac output voltage of controllable magnitude and frequency.
A hybrid regenerative power system including photovoltaic (PV) and wind powers and combining the functions of the grid-tie system and uninterruptible power supply (UPS) for critical load applications is presented. The proposed system employs six-arm converter topology with three arms for the rectifier-inverter, one arm for battery charging/discharging and two arms for power conversion of the PV module and wind turbine generator. The operation modes include the grid-tie mode and the UPS mode depending on the grid status. A power balance control scheme is presented, which can reduce the grid power and utilise the regenerative power in the most effective way for fulfilling the two requirements of a three-stage charging of the battery and no interruption of the load. Also, the PV and wind powers can be utilised with priority in order to provide the flexibility for adapting to local circumstances. A single-phase 1.2-kW/110-V system is designed and implemented, and the effectiveness of the proposed system and control methodology are verified with some experimental results.
An extension of the DQ transformation for single-phase systems is presented in this work, since the original approach can only be applied to three-phase systems. The theoretical principle of the proposed transformation is presented. Equations about how the fundamental component and the harmonics of the variable of concern are mapped in the dq reference frame are derived. The proposed transformation is evaluated under ideal and real conditions, and with magnitude and/or phase deviations. Besides, an adequate selection of the reference generator scheme to compensate systems with harmonic distortion and reactive power is made, obtaining an optimal selection of all parameters.
A control method in the direct-quadrature (DQ) rotating frame for a single-phase inverter or PFC rectifier is proposed to provide an infinite control gain (theoretically), thus zero steady state error at its fundamental frequency to achieve superior steady state and dynamic performance. This new control method transforms the physical "real circuit", in conjunction with an "imaginary orthogonal circuit", from the stationary frame to the DQ rotating frame so that the steady state voltage/current in the DQ frame become DC variables. The new control concept is validated through a single-phase grid simulator used for utility compatibility tests, as described in IEEE P1547 draft standard, IEEE Std 929, UL 1741 and NYSIR, for single-phase distributed generators (DG), such as residential fuel cell generators or photovoltaic power conditioning systems. Experimental results in steady state with programmable simulated utility line impedance are given along with the dynamic transient response for NYSIR type test. The control concept is also applicable to zero-sequence control for three-phase four-wire systems.
This review focuses on inverter technologies for connecting photovoltaic (PV) modules to a single-phase grid. The inverters are categorized into four classifications: 1) the number of power processing stages in cascade; 2) the type of power decoupling between the PV module(s) and the single-phase grid; 3) whether they utilizes a transformer (either line or high frequency) or not; and 4) the type of grid-connected power stage. Various inverter topologies are presented, compared, and evaluated against demands, lifetime, component ratings, and cost. Finally, some of the topologies are pointed out as the best candidates for either single PV module or multiple PV module applications.
Full-bridge lossless switching converter
- steigerwald
Costs and Benefits of Conservation Voltage Reduction
- D Pinney