Distributed Generation - Science topic

Decentralized Distributed generation is in the long run sustainable source of energy for the economic development of a nation, provided after locally meeting the demand well established connectivity is there between systems along with storage to manage perfect balance of demand and supply of electricity.

hi,

The ratio of the amount of DG energy injected into the network to the feeder capacity . Distributed Energy Resources (DER) had changed many aspects of distribution system operation, design and implementation.

Distributed Generation (DG) offers the reliable and economic source of electricity to consumers. These are connected directly to the distribution system at consumer load points. Integration of DG units into an existing system has significantly high importance due to its innumerable advantages.

As per IE rules the permissible variation of voltage at the consumer end is upto ±6%. In case of low or medium voltage i.e. upto 33 kV , the permissible variation of voltage is ±6% to ±9%. In case of high voltage supply i.e. more than 33 kV, the permissible variation of voltage is more than ±9%.

For more information kindly refer this link:

Best wishes..

Block-chain technology facilitates energy sales transactions directly, within seconds, which in other cases requires a central intermediary. The energy industry has been consistently catalyzed by innovations including rooftop solar, electric vehicles, and smart metering . Besides this, by allowing consumers to make better use of their distributed energy resources, the model makes renewable energy more accessible. Block-chain can provide consumers greater efficiency and control over their energy sources. Additionally, an immutable ledger provides secure and real-time updates of energy usage data. Various types of energy data include market prices, marginal costs, energy law compliance, and fuel prices and the use of block-chain technology can, for example, be applied to electricity recharging terminals, to allow the recording of electricity transactions and their accounting follow-up in complete transparency and without possible error. Several initiatives are currently emerging.

Hello Muhammad,

Based on the information in your question, I assume you are investigating BESS in general, or is there a specific application you are considering?

Certain battery technologies are preffered over others depending on the application. My suggestion would be to start with investigating the different types of battery technologies on the market, and if you are targeting a specific application, the battery technologies that are commonly used for that application. A good starting point for information is Original Equipment Manufacturer (OEM) websites and their application notes and technical literature. Thereafter, you can progress into the more targeted research papers/articles found in journals etc.

Best wishes with your research,

Sagadevan

I would like to give an answer if I understood correctly, you mean if you simply tune your hyperparameters on the test split they will not generalize properly?

There are two good ways to handle generalization:

1- First you can have 3 splits, training, validation for tuning, and testing for generalization checking.

2- Second You can use K-fold cross-validation, making for example 10 different splits of validation and tunning for their average results.

Please note that one of the main reasons for overfitting can be due to outliers and noise in the data, so if by partition split you mean K-fold cross-validation, then it is good. Although, it is preferable to tune one the validation and keep your testing data for the generalization test.

The cost of the system in the short term compared to the available conventional energy negatively affects the decision. I think to achieve the goal for green and clean energy, there should be government incentives or waivers for customers who develop an interest in procuring photovoltaic systems.

Also check https://www.modernpowersystems.com/features/featurewhen-things-go-wrong-identifying-combined-cycle-problem-areas/

you can find answers in this article:

The following papers can be useful

Dear Mohammad

If there is a PMU or a meter which can measure the outputs of the renewable resource, it can be easily imported to the formulation of SE problem like other real-time measurements. Otherwise, the outputs of renewable resources should be predicted based on the historical data with high level of uncertainty like 50%. In this situation, the outputs of these resources are determined using pseudo-measurement.

It should be noted that if you want to work on modeling the probability distribution function of renewable sources' output, you must use the real data to find the parameters related to the mixture normal distribution and then import it into the SE procedure.

Thomas Wolgast thanks for your response. If we have different types of energy resources (eg PV wind plants) in a distributed generation system, then the voltage fluctuates due to their intermittent nature of PVs and winds plants, that is why we need proper voltage regulation or control technique to maintain the voltage at each node/bus of the network within standard limits. So, I want to implement some evolutionary technique (ie. PSO) for optimal power flow including the voltage constraints like you mentioned in your previous comment. thanks

I think this is good researching topic, but is necessary to take into consideration about safety regulations in order to avoid any accident, because the islanding mode enter in operation when grid goes down, so the switching control system from grid to islanding mode needs to include an intelligent alert system.

Dear ;

please check the attached files :

Article Reconfiguration of power distribution systems using probabilistic reliability models Full-text available July 2011 B. Amanulla Saikat Chakrabarti S. N. Singh

Regards

Hi Andres Mazariegos

There are 2 main ways from WEKA:

1- using the KnowledgeFlow interface via "AttributeSummarizer" and "ImageSaver".

2- Install the "RPlugin". Then from the RConsole in WEKA, type R code like: plot(rdata$yourclassname).

You could also explore other options like Excel and SPSS to generate such plots.

HTH.

Dr. Samer Sarsam

Dear Kadem Mohammed you can seen the papers links as bellow:

yes, it is very important

Mankind has used and still consumes a large proportion of the planet's non-renewable energy resources such as oil, natural gas and coal to meet its energy needs. In just the past two decades, other renewable energy sources such as solar photovoltaics and wind energy have become somewhat related to generating electricity in the world.

The acceptance time depends on review time by reviewers, revise time of authors.

https://mjl.clarivate.com/search-results

The above link provides that users can search for all journal titles currently covered in Web of Science (SCI, SCIE and ESCI), updated on a monthly basis.

Thank You Sir!

What are the parameters of PQ(V) Type of DG like Active power, Reactive power equations, Slip, Reactance value?

Also how to handle PQ(V) type of DG?

Perhaps the following article will tell you the answer: Lipilin A.S. Sostoyanie i budushchee individual'noj energetiki // Mezhdunarodnyj nauchnyj zhurnal Al'ternativnaya energetika i ekologiya. Izdatel'stvo: Nauchno-tekhnicheskij centr "TATA" (Sarov). ISSN: 1608-8298. 2009. № 9(77). С. 139-152

Липилин А.С. Состояние и будущее индивидуальной энергетики // Международный научный журнал Альтернативная энергетика и экология. Издательство: Научно-технический центр "ТАТА" (Саров) ISSN: 1608-8298. 2009. № 9(77). С. 139-152

Dear Sir,

Thank You for sharing information.

but As per the literature available DG can be modeled by PV , PQ, PQ(V) & PI type as per the DG resources like solar, wind, fuel cell etc.

You can use the split DC link which includes two series capacitor in parallel with a large balancing resistor for each of them . This a simple way to provide a neutral point which its voltage clamped at half of the DC link voltage .

Special PWM generating schemes can be used for balancing of the capacitors voltages. But where the neutral current is large, it flows through the capacitors and, hence, bulky capacitors are needed to make the voltage ripple on the capacitors. Also the neutral point usually drifts and becomes unbalanced when it includes DC component. So different strategies for neutral point balancing are reported, usually using the Space Vector Pulse Width Modulation or MPC control.

A better way to provide a neutral line is to add an additional fourth leg, called a neutral leg, to the conventional three-leg converter. The neutral current can be controlled to flow through the inductor so that the neutral point is maintained at the mid-point of the DC link. This allows the phase legs and the neutral leg to be controlled independently, which means the three phases can be controlled independently as well.

Ref :

Control of Power Inverters in Renewable Energy and Smart Grid Integration https://ieeexplore.ieee.org/book/6381785

I think the Grid power should be -10 kW. have you checked the 'three phase VI measurement block' direction to measure power from/to grid? Captial letter ABC of the 'three phase VI measurement blocks' should be at the grid side.

Thank you Professor Soheil Sayyed Hosseini. I will go through your paper and if at all if I am having any doubts means I will contact you again.

Hi I'm Professor Soheil Sayyed Hosseini To solve the problem see my article on this issue of my control, which is vfc published by the University of Rochester. If it is acceptable, say I wish you well.

To make more sense, in my view, you should simultaneously find optimal locations and capacities associated with DG resources. In fact, you can mathematically model your problem and implement it in a modeling environment like GAMS. Given the objective of your problem (i.e., total cost, total loss, and so on), you can easily find the location and capacity of DGs through adding capacity constraints and binary decision variables, respectively.

Thank you for your prompt reply. All these is new to me. I will read these papers with keen interest.

Rotor angle stability literally refers to the stability of conventional synchronous generators no matter it is large-disturbance/transient stability due to lack of synchronizing torque or small-disturbance stability due to lack of damping. If there is no SG in the system, technically there should not be any rotor angle stability problem or it should not be called rotor angle stability. But in this case, does the synchronism/damping problem still exist? The answer is Yes. You must have seen a lot of papers talking about PLL stability right? (if you would like to name it rotor angle stability, you can define youself!) The 'new' synchronism/damping problem for power electronic converter-interfaced equipment mostly manifest in the form of undamped oscillations due to poor tuning of controller parameters in the lower voltage systems. When a grid has both SG and new power electronic converter-connected generation, the dynamics might be much more complex considering their interactions across a range of frequency.

Recently, there is a paper entitled 'Microgrid Stability Defintions, Analysis and Examples' provided by IEEE PES Task Force on Microgrid Stability, which might help you understand this issue better.

Please take a look to these sites

Best regards

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7874626

The following link is useful,

What are you trying to achieve here? Let's be clear by what you mean by price. Is it the price on some network, or the price paid by the consumer? Surely not the latter as that is determined solely by how much profit the reseller wants to achieve and has nothing to do with spot pricing. Since the generation cost of the electricity doesn't change from moment to moment, you are surely trying to derive, in this 'price', and economic signal on which some further decisions are based. What sort of signal, what sort of decisions do you anticipate being made? Then you will be able to determine how to generate a suitable economic signal for them. But as you can see, I am VERY sceptical about all this sort of thing; I am disgusted at finding the consumer price of electricity is likely 8 or 10 times its generation cost and has nothing to do with any spot price however derived at some point in the transmission / distribution chain.

As previously mentioned by Shah Fahad and Samundra Gurung synchronous generators have in built inertia owing to its construction and operation. On the other hand, other DGs are connected through converter stages which isolates the DG unit from the grid or the loads. Hence, a virtual inertia can impart the necessary inertia to damp any oscillations in the system response that may be caused by load fluctuations, voltage and frequency instability.

Hi there, my research area is mainly on using probabilistic methods for power system stability. Perhaps, you can use similar concept in your field. Please see the following links which may be useful for you:

https://ieeexplore.ieee.org/abstract/document/8036264

Regarding the DGs, the affect of aggregated and distributed energy storage systems on the operation.

The economical operation under service restoration

Try with Matlab documentations and examples on official site. There are many types of generators in Matlab/Simulink library with various types of regulations. It will be challenging to find optimize setup for all parameters inside regulations parameters. Nevertheless, official Matlab documentations is sufficient, and you will be able to solve your model design, and accomplish you study work.

You can find an example in this paper:

Urban Energy Hubs Economic Optimization and Environmental Comparison in Italy and Vietnam

Please take a look at these articles

I developed a model in matlab and I also used HOMER for modeling distributed electricity generation units. You might find my reports and articles helpful for your study:

Smart grids are designed to:

1) Reduce the electricity demand load on the utility grid during daily peak demand periods.

2) Support renewable energy generation via distributed energy systems (DES) wind turbine farms, solar PV, concentrated solar power (CSP), and fuel cells stations.

3) Create independence of the utility grids in remote areas.

Accordingly, I'd say that market penetration by large-scale renewable energy systems relies on the presence of smart grids as well as distributed energy storage (DES) to offset the incompetency of renewable sources such as wind turbines, solar PV, CSP, etc.

Please feel free to download my lecture notes from the "Green Energy Systems" course that I developed and taught at Yale University. You can find these lecture notes and publications under my profile in ResearchGate.net.

Hope this helps answer your question and good luck.

I have a feeling that concentration on the development and fine-tuning of financial mechanisms in order to stabilise grid voltages is missing the point. The transfer functions between prices and voltage are too complex. As Dr Holmberg suggests, a more simple mechanism such as a feeder level dynamic price might be the answer. But there has to be a dominant time lag in the system otherwise it will become unconditionally unstable.

It will easier to use the latest version of the Power System Analysis Toolbox (PSAT) for your target. Alternatively, you need to study the built-in case study of isolated operation of diesel generators. You will find some other case studies with the simpowersystems toolbox

Hello Dr. Tina,

The following chapter is helpful in the simulink-based modeling of various modules.

S. Sumathi et al., Solar PV and Wind Energy Conversion Systems,

Green Energy and Technology, DOI 10.1007/978-3-319-14941-7_2

Based on a previous meeting with Schneider electric, they constructed two separate inverters for each mode of operation. The one designed for on-grid applications synchronises its output with the grid, while the one designed for off-grid standalone solar-PV operation synchronises its output with a self-generated reference signal. Therefore, in your inverter the two capabilities should be available according to the mode of operation. I guess these options are neither available in the mathworks file exchange website, nor the above chapter.

Dear Muhammad

Please see the attachements subjects

Best regards

* Effect of distributed generation on protective device coordination in distribution system

* Reviewing the impacts of distributed generation on distribution system protection

* A novel neural network and backtracking based protection coordination scheme for distribution system with distributed generation

You have to control the power angle of one of the machines; for that the frequency has to change temporarily, either increase or decrease for the power angle to change. Once reached the desired power the frequency goes back to its nominal value. So, the controlled variable is the power angle.

Mathematically, the commonly used PR controller is not equivalent to PI controller. It can be deduced using the theory presented in the appendix of [1] that the controller in stationary frame shown in the attached figure is equivalent to a PI controller in synchronous frame.

[1] D. N. Zmood; D. G. Holmes. "Stationary frame current regulation of PWM inverters with zero steady-state error," IEEE Transactions on Power Electronics, 2003, 18(3): 814 - 822.

You can find in the attached figure that there exist coupling terms between the alpha axis-controller and the beta-axis controller. The commonly used PR controller in stationary frame does't include such coupling terms. The coupling terms come from the controller itself, not from the plant. If completely decoupled controller is required, the coupling terms generated by the plant model (e.g. the typical R-L model) should also be included.

I have done some test in matlab/simulink some time ago that such a controller performs exactly the same with the PI controller in stationary frame, if the parameters Kp and Ki have the same values.

However, in practice, the performance difference between the commonly used PR controller and PI controller may not be so obvious.

In addition, I would like to recommend the an advanced resonant controller, i.e. the vector-proportional-integral (VPI) controller. Its expression is s(Kps+Ki)/(s^2+w^2). Its numerator could be used to cancel the pole of the R-L plant. VPI controller could eliminate undesired peaks in the bode plot. According to my experience, it performs really better than the common PR controller. More information about the VPI controller could be found in [2] and other literature.

[2] Alejandro G. Yepes; Francisco D. Freijedo; Jesús Doval-Gandoy; Óscar López; Jano Malvar; Pablo Fernandez-Comesaña. " Effects of Discretization Methods on the Performance of ResonantControllers," IEEE Transactions on Power Electronics, 2010, 25(7): 1692 - 1712.

I agree with the comment of Mr. Riccardo Lama; however, four critical problems are to be considered when integrating DGs to distribution systems: (1) Voltage profile/voltage rise problems; (2) Impacts on power flow directions, and protection coordination; (3) Thermal limits of cables/line; (4) Power quality disturbances causes by the presence of electronically coupled DGs such as solar-PV generators. Of course there are some additional issues to be considered such as islanding operation and stability, reliability level, and investment costs. Therefore, in the DGs integration problem,you need to set multi-objectives including those mentioned here and by Riccardo Lama, and Jagadeesh Gunda .

As I understand the situation in Germany, the tax is a surcharge on the bill for grid supplied electricity, so it is not a tax on self generation or consumption. To make sure you don't have to pay it, simply ensure your PV system supplies all the electricity you require so you don't draw anything from the grid. However, I just cannot see how this is going to work in Europe in the winter. You just don't get enough solar.

I think this depends on the grid management and local rules. In Switzerland the PV systems with FiT have a contract with the government, which buys the whole production (autoconsumkption is not possible in these systems) at the FiT.

Only large installations can however benefit from the FiT. Small systems (less than 30 kW peak) get a fixed subsidiary at the construction, and then self consume the production. The excess is sold (at low price) to the grid management, which also provides electric energy (at normal price) when the PV system does not cover the needs.

Dear Umair,

When you talk about "optimal" there is no single best technique. It all depends on identification of associated parameters, how many parameters you are considering, which technique you are using, how you implement the algorithm, etc... Since, you've asked for a publication, i suggest that you should go through the following publications: (Please go through section 4 in this paper, which provides detailed survey on various DGs planning methodologies and their comparison.

Instead of using UML diagrams directly to design the proposed problem, you might create a UML profile to adapt this oriented modelling language for smart electric networks and customise thus the Class diagram and/or composite, deployment diagrams to support the aforementioned situation. Interestingly, many examples of UML profiles designed for different domains and platforms are proposed in literature, for instance SysML, profile MARTE, aerospace profile, UML profile for radiology, etc. Please take a look at OMG web site: www.omg.org

Thank you Jamal. I am going through this journal.

I am very grateful Luca.

The CERTS microgrid is a standard test system, which works at a nominal voltage of 480V (LV).

This book is available at the moment to purchase ???

SCADA (Supervisory Control and Data Acquisition) System . 

Depends on the the type of distributed generation (DG) incorporated. For example, the scenarios are likely to be different for PV-based and different types of wind turbine based sources. If your question is specific, only then you should expect some specific answer. In general, small disturbance stability has been an active research area. The instability mitigation process is another research area. 

You can use H=1.76 for 0.5-1 MW diesel generator.

For gas turbine, you can use H=2 - 3

Hi Ahmad,

quite an interesting and challenging question. We are dealing with microgrids at present and your question has actually many answers. My impression, based on some preliminary simplified simulation is that technologies with inverter interface may be controlled so fast that any unbalanced caused by wind/solar fluctuation can be compensated. This is for instance the case of Battery Storage, the wind itself to transfer part of blade inertia, and solar (in reduction mode only). However I can see constraints  since some aggressive operational mode can have an impact on lifetime, and economic impact since reducing RES production may require market compensation for balancing service.  

don't use transformation. check our new paper

Sanjoy Roy

What you propose is what is typically done nowadays, and for simple systems it works, skilled people do it even without simulation.

But if 5 parameters, P, I, D, low pass in D and saturation have to be chosen, there is a big chance that trial and error does not converge to the right solution. If there are resonances in filters or a DC-link with small film capacitors that add to the problem, the chances to find a solution by trial and error get very low. In practice also noise, disturbances and non-linearities can be present.

A typical non-linearity is the saturation of a controller (wind-up) but also that a control jumps from 95% duty to 100% duty ratio.

The Nyquist (or Bode) is an independent way to know if one is far away or not from what could be obtained.

My experience is that even a lot of systems get unstable at half of the switching frequency rather than the resonance frequencies.

A typical problem is that Matlab implements PWM without delay, which is true for a pure analog PWM. Most of people use that model for a digital system where there is definitely a delay between sampling and PWM compare levels.

In drives, the wind-up is eliminated by resetting the speed integrator when the torque is limiting during acceleration. If this is not done a lot of error is cumulated and will result in a big overshoot in speed.

Wind-up is one aspect, but there are many reasons why simulations do not correspond to the reality.

In theory the practice is equal to the theory, however, in practice it is not.

Alex

@ Jeremy : Please check you email.

hi

im find this link

hi

Nowadays, these renewable DG are required to equip with reactive power devices (such as static VAR compensators, capacitor banks, etc), to provide reactive power as well as to control the voltage at their terminal bus. So, the issues related to voltage control, voltage stability are no longer an issue

maybe i can help you but need more explanation what you want exactly!

I suggest PLL (Phase Locked Loop) algorithm to synchronize with power grid. A good paper to read is: http://ieeexplore.ieee.org/document/5414976

To work with lower voltage is better than to work with higher voltage, for better control and operation. For same VA capacity, with lower voltage, charging time needed would , also be less.....

hi amir

any optimization algorithm can be used to solve it

Hi Miao,

Just go through the following steps:

With best wishes.

-Sanjay

In DG placement, it is better to find the location of the DG so that its placement with the fixed injection will lead to the minimum loss than any other position. As long as, optimization techniques are concerted,  any non-linear optimization approach including heuristics can be used.  

Dear Ashraf, yes i am using droop control. Thanks for answering

Hi Ugochukwu,

Plenty such work has been reported in the IEEE Transactions.

I suggest you visit the IEEEXplore Digital Library online, and do some keyword searches on it !

Cheers !

-Sanjay

Gadaram,

I have little confidence in doing bidirectional flow for a radial system. In a radial system, power will flow in only one direction. Well, the power will flow from the side of 'generator' to the side of the 'load'. If you have only load at the end of the radial system, you cannot get the opposite flow. 

Even if you have a generator (say DG) on the load side, but if the DG size is smaller than the load, the power will flow in the same (traditional) direction (from generator to load). But if your DG size is bigger than the load which is located at the same place, then, some power will be pushed back from that DG into the grid. So, it's either the regular traditional power flow or opposite.

But, if you have a meshed network for the distribution system, the power will flow based on where your DGs are located and where you loads are.

I hope this helps!!

Regards,

Jeremy

The Anderson book on power system stability has all the generator parameters you need.

You can also use dQ/dt> detection since the most DG work with power factor (cos phi=1) or close to 1 . If  the generator is opened disconnect from network with full balance between the production and consumption Pg=PL you will still have consumption of reactive power for plant own motors , trafo etc. Then power factor decrease to 0,95 or less and you have deviation of Q-reactive power which can be detected. Such practical solution we use and it works on one biomass power plant..

Standby generator can supply power to the load, but operational constraints & equilibrium constraints should not be violated.