Coordinated Active Power Curtailment of Grid Connected PV Inverters for Overvoltage Prevention
TL;DR: In this paper, the authors discuss the use of droop-based active power curtailment techniques for overvoltage prevention in radial LV feeders as a means for increasing the installed PV capacity and energy yield.
Abstract: Overvoltages in low voltage (LV) feeders with high penetration of photovoltaics (PV) are usually prevented by limiting the feeder's PV capacity to very conservative values, even if the critical periods rarely occur. This paper discusses the use of droop-based active power curtailment techniques for overvoltage prevention in radial LV feeders as a means for increasing the installed PV capacity and energy yield. Two schemes are proposed and tested in a typical 240-V/75-kVA Canadian suburban distribution feeder with 12 houses with roof-top PV systems. In the first scheme, all PV inverters have the same droop coefficients. In the second, the droop coefficients are different so as to share the total active power curtailed among all PV inverters/houses. Simulation results demonstrate the effectiveness of the proposed schemes and that the option of sharing the power curtailment among all customers comes at the cost of an overall higher amount of power curtailed.
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TL;DR: In this paper, a simulation study was performed to investigate potential voltage rise issues in the network up to 11.25% total PV penetration in the feeder and LV transformer capacity penetration up to 75%.
Abstract: The objective of this paper is to provide an assessment on voltage profiles in residential neighborhoods in the presence of photovoltaic (PV) systems. The network was modeled in PSCAD using common feeder characteristics that Canadian system planners use in suburban residential regions. A simulation study was performed to investigate potential voltage rise issues in the network up to 11.25% total PV penetration in the feeder and LV transformer capacity penetration up to 75%. Results indicate that the PV penetration level should not adversely impact the voltage on the grid when the distributed PV resources do not exceed 2.5 kW per household on average on a typical distribution grid. Moreover, the role of feeder impedance, feeder length, and the transformer short circuit resistance in the determination of the voltage rise is quantified.
487 citations
Cites background from "Coordinated Active Power Curtailmen..."
...Residential feeders with PV systems can be considered a critical case regarding overvoltage [6]....
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TL;DR: This paper proposes a methodology based on sensitivity analysis to assess the impact of P2P transactions on the network and to guarantee an exchange of energy that does not violate network constraints, which is tested on a typical U.K. low-voltage network.
Abstract: The increasing uptake of distributed energy resources in distribution systems and the rapid advance of technology have established new scenarios in the operation of low-voltage networks In particular, recent trends in cryptocurrencies and blockchain have led to a proliferation of peer-to-peer (P2P) energy trading schemes, which allow the exchange of energy between the neighbors without any intervention of a conventional intermediary in the transactions Nevertheless, far too little attention has been paid to the technical constraints of the network under this scenario A major challenge to implementing P2P energy trading is ensuring network constraints are not violated during the energy exchange This paper proposes a methodology based on sensitivity analysis to assess the impact of P2P transactions on the network and to guarantee an exchange of energy that does not violate network constraints The proposed method is tested on a typical UK low-voltage network The results show that our method ensures that energy is exchanged between users under the P2P scheme without violating the network constraints, and that users can still capture the economic benefits of the P2P architecture
427 citations
Cites background or methods from "Coordinated Active Power Curtailmen..."
...The droop parameters of the inverters are different so that the output power losses (OPL) are shared equally among all prosumers [18]....
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...For example, PV generation can be curtailed proportionally to avoid voltage problems using a dynamic curtailment method [18]....
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TL;DR: In this article, a comprehensive overview on important issues affecting the distribution system as a result of PV penetration is presented, including voltage fluctuation, voltage rise, voltage balance, and harmonics and their effect on the system.
Abstract: The solar energy generation has grown significantly in the past years. The importance of PV penetration in power system as a major element of renewable energy source has seen it being widely used on a global scale. Despite its promising success, PV penetration presents various issues and its impact on the distribution system has to address for seamless integration in the power system. In this paper, a comprehensive overview on important issues affecting the distribution system as a result of PV penetration is presented. Pertinent issues such as voltage fluctuation, voltage rise, voltage balance, and harmonics and their effect on the system are discussed in details. The islanding issues, which are of critical importance to the stability and integrity of the system, are also thoroughly reviewed. Details on different islanding techniques – remote and local techniques and their advantage and disadvantages are shown. Therefore, this paper can provide useful information and serve as a reference for researchers and utility engineers on issues to be considered with regards to PV penetration.
403 citations
Cites background from "Coordinated Active Power Curtailmen..."
...The choice of active power curtailment has its own advantages as it does not require extensive modification in the PV's inverter and further presents the option for the system operator for the most costeffective solution [83]....
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TL;DR: In this article, the authors investigated the solar PV impacts and developed a mitigation strategy by an effective use of distributed energy storage systems integrated with solar PV units in lowvoltage distribution networks, where the storage is used to consume surplus solar PV power locally during PV peak, and the stored energy is utilized in the evening for the peak-load support.
Abstract: A high penetration of rooftop solar photovoltaic (PV) resources into low-voltage (LV) distribution networks creates reverse power-flow and voltage-rise problems This generally occurs when the generation from PV resources substantially exceeds the load demand during high insolation period This paper has investigated the solar PV impacts and developed a mitigation strategy by an effective use of distributed energy storage systems integrated with solar PV units in LV networks The storage is used to consume surplus solar PV power locally during PV peak, and the stored energy is utilized in the evening for the peak-load support A charging/discharging control strategy is developed taking into account the current state of charge (SoC) of the storage and the intended length of charging/discharging period to effectively utilize the available capacity of the storage The proposed strategy can also mitigate the impact of sudden changes in PV output, due to unstable weather conditions, by putting the storage into a short-term discharge mode The charging rate is adjusted dynamically to recover the charge drained during the short-term discharge to ensure that the level of SoC is as close to the desired SoC as possible A comprehensive battery model is used to capture the realistic behavior of the distributed energy storage units in a distribution feeder The proposed PV impact mitigation strategy is tested on a practical distribution network in Australia and validated through simulations
305 citations
Cites background from "Coordinated Active Power Curtailmen..."
...Active power curtailment [5] and reactive power consumption [6] have been proposed for voltage-rise mitigation....
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TL;DR: In this paper, a comprehensive literature review on problems associated when the intermittent PV is connected to grid and the methods of smoothing the output power fluctuation from PV is presented, also briefly discusses control strategy built for battery energy storage pertaining to this issue.
Abstract: Renewable Energy Sources (RESs) particularly photovoltaic (PV) and wind are becoming important sources for power generation. Frequently varying output of PV and wind caused by clouds movement, weather condition and wind speed make them an intermittent and unreliable sources when connected to grid. Connecting intermittent sources to grid introduces challenges in various technical aspects such as power quality, protection, generation dispatch control and reliability. In this context, leveling intermittent source׳s output is necessary inorder to maintain grid׳s stability. This paper is aimed at bringing out the latest comprehensive literature review on problems associated when the intermittent PV is connected to grid and the methods of smoothing the output power fluctuation from PV. This paper also briefly discusses control strategy built for battery energy storage pertaining to this issue.
304 citations
Cites methods from "Coordinated Active Power Curtailmen..."
...power using PV inverter control was demonstrated in [90,91]....
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...SOC-feedback control is used to limit the PV output from inverter to maintain the voltage within specified limit [91]....
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References
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TL;DR: The paper explorers the resistive output impedance of the parallel-connected inverters in an island microgrid and proposes a novel wireless load-sharing controller for islanding parallel invertes in an ac distributed system.
Abstract: In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an ac-distributed system is proposed This paper explores the resistive output impedance of the parallel-connected inverters in an island microgrid The control loops are devised and analyzed, taking into account the special nature of a low-voltage microgrid, in which the line impedance is mainly resistive and the distance between the inverters makes the control intercommunication between them difficult In contrast with the conventional droop-control method, the proposed controller uses resistive output impedance, and as a result, a different control law is obtained The controller is implemented by using a digital signal processor board, which only uses local measurements of the unit, thus increasing the modularity, reliability, and flexibility of the distributed system Experimental results are provided from two 6-kVA inverters connected in parallel, showing the features of the proposed wireless control
928 citations
01 Dec 2005
TL;DR: In this paper, a novel wireless load sharing controller for islanding parallel inverters in an ac distributed system is proposed, where the resistive output impedance of the parallel-connected inverters is explored.
Abstract: In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an ac distributed system is proposed. The paper explorers the resistive output impedance of the parallel-connected inverters in an island microgrid
718 citations
"Coordinated Active Power Curtailmen..." refers background in this paper
...In LV systems, the relationship between voltage and active power is stronger than with reactive power given the highly resistive line characteristics [4], [24]....
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TL;DR: In this paper, the authors summarized the results of some generic studies, explaining the voltage rise issue and how it may be overcome, and proposed methods to counteract voltage rise are primary substation voltage reduction, reactive power import, autotransformers installation, conductor upgrading, and generation constraints.
Abstract: There has been much interest in embedding small generators deep within distribution systems. The steady-state voltage rise resulting from the connection of these generators can be a major obstacle to their connection at the lower voltage levels. This article summarises the results of some generic studies, explaining this voltage rise issue and how it may be overcome. Methods discussed to counteract voltage rise are primary substation voltage reduction, reactive power import, autotransformers installation, conductor upgrading, and generation constraints.
660 citations
"Coordinated Active Power Curtailmen..." refers background in this paper
...In general, to address overvoltage issues one can: 1) reduce the secondary LV transformer voltage adjusting the tap [8]; 2) allow the DGs to absorb reactive power, [9]–[13]; 3) install auto-transformers/voltage regulators [8], [14], [15]; 4) increase the conductors size, reducing line impedances [8]; 5) store the power surplus for later use [16]; or 6) curtail the power of DG units [4], [7], [8]....
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...A number of different approaches [8], [17], [18] has been presented in the literature....
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TL;DR: In this paper, a distributed automatic control approach is proposed to alleviate the voltage rise caused by active power injection in distribution networks with distributed generation, where the objective is not to control bus voltage but to guarantee that generator injections alone do not cause significant voltage rise.
Abstract: This paper addresses the problem of voltage rise mitigation in distribution networks with distributed generation. A distributed automatic control approach is proposed to alleviate the voltage rise caused by active power injection. The objective of the proposed approach is not to control bus voltage but to guarantee that generator injections alone do not cause significant voltage rise: a solution in which distribution network operators (DNOs) are kept to their traditional task of voltage regulation for load demand. The approach is discussed in the perspective of effectiveness and adequacy. Its consequences to DNO control effort are evaluated. Illustration is provided for a single feeder with stochastic generation and transformer on-load tap-changing voltage regulation.
613 citations
"Coordinated Active Power Curtailmen..." refers background in this paper
...In general, to address overvoltage issues one can: 1) reduce the secondary LV transformer voltage adjusting the tap [8]; 2) allow the DGs to absorb reactive power, [9]–[13]; 3) install auto-transformers/voltage regulators [8], [14], [15]; 4) increase the conductors size, reducing line impedances [8]; 5) store the power surplus for later use [16]; or 6) curtail the power of DG units [4], [7], [8]....
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TL;DR: In this paper, a simulation study was performed to investigate potential voltage rise issues in the network up to 11.25% total PV penetration in the feeder and LV transformer capacity penetration up to 75%.
Abstract: The objective of this paper is to provide an assessment on voltage profiles in residential neighborhoods in the presence of photovoltaic (PV) systems. The network was modeled in PSCAD using common feeder characteristics that Canadian system planners use in suburban residential regions. A simulation study was performed to investigate potential voltage rise issues in the network up to 11.25% total PV penetration in the feeder and LV transformer capacity penetration up to 75%. Results indicate that the PV penetration level should not adversely impact the voltage on the grid when the distributed PV resources do not exceed 2.5 kW per household on average on a typical distribution grid. Moreover, the role of feeder impedance, feeder length, and the transformer short circuit resistance in the determination of the voltage rise is quantified.
487 citations