Voltage Rise Mitigation Research Articles

Online Reconfiguration of Active Distribution Networks for Maximum Integration of Distributed Generation

This paper proposes the online reconfiguration of active distribution networks. The control of the active/reactive output power of distributed generation (DG) units combined with the control of remote controlled switches are employed in order to minimize DG curtailment, alleviate lines congestion, and mitigate voltage rise issues due to DG integration. Convex relaxations of the ac power flow equations and mixed integer linear disjunctive formulations are adopted to the optimization model in order to obtain fast and optimal solutions using standard branch and bound solvers. The computation burden of the optimization procedure is drastically reduced by exploiting the assessment of switching actions, which is performed using multiple load/generation scenarios. The effectiveness of the proposed optimization model is verified using different distribution test systems.

Consideration of Reactor Installation to Mitigate Voltage Rise Caused by the Connection of a Renewable Energy Generator

This paper describes the detailed analysis of a reactor application for a power plant to mitigate the voltage rise of a distribution line (DL) caused by the connection of distributed resources (DRs). The maximum capacity of renewable energy generators (REGs) that meets the acceptable voltage rise of a DL and the necessary capacity of the reactor to mitigate that voltage rise according to the different types of REGs are analyzed. The re-coordination of a protection relay and the loss of generation revenue as well as the installation location of a reactor are described. Finally, the ON/OFF conditions of the reactor, such as the magnitudes of the grid voltage and generator voltage, and the duration time of the voltage rise are analyzed. As the voltage rise is mitigated and self-limited in small power plants, it is confirmed that the capacity of the DRs connected to the DL can be increased through a field demonstration.

An evaluation of options to mitigate voltage rise due to increasing PV penetration in distribution networks

Australia and most other countries are adopting renewable energy generation as the dominant means of reducing dependence on fossil fuels. This has been made more feasible by the exponential take-up of solar photovoltaic (PV) systems and their concurrent production scale-up and cost decline. Rooftop solar PV, combined with battery storage, seems likely to be the dominant means of providing household electricity needs. In response to the technical challenges from rooftop PV, network utilities have implemented various low cost options to cope with PV’s impact on network voltages. However, if we want this clean energy technology to fully utilise the available roof space and eventually meet residential electricity needs, additional hardware, control and commercial options will need to be adopted by both network utilities and their customers to overcome the technical barriers, especially voltage rise. This paper presents the authors’ evaluations of options to mitigate voltage rise, including operating solar inverters with reactive power absorption (var absorbing), dependent only on solar power output or operating the solar inverters in a volt–var response mode (voltage droop control) where the inverter adjusts its reactive power (Q ) in response to changes in its terminal voltage – Q (V ). This paper also considers the fulltime Q (V ) option, where an inverter’s reactive power capacity is independent of solar conditions – statcom mode. The network utility option of using line drop compensation (LDC – used on long rural MV feeders) on urban MV feeders during daylight hours is assessed to lessen voltage rise on LV feeders with low net loading or reverse power flow due to high solar PV generation. The paper concludes that a combination of solar inverters performing fast fulltime voltage droop control outside a voltage deadband (statcom mode) and HV/MV substation transformers with slow acting daytime LDC mitigates voltage rise, whilst limiting feeder reactive power requirements.

Voltage Control with PV Inverters in Low Voltage Networks—In Depth Analysis of Different Concepts and Parameterization Criteria

In some rural and sub-urban areas, the hosting capacity (HC) of low voltage networks is restricted by voltage limits. With local voltage control, photovoltaic generators can mitigate the voltage rise partly and, therefore, increase the HC. This paper investigates the effectiveness and general performance of different reactive and active power control concepts. It presents the findings of an extensive simulation-based investigation into the effectiveness of voltage rise mitigation, additional reactive power flows, network losses, and power curtailment. The two most common implementations of reactive power control have a similar effectiveness. The voltage rise can be compensated for by up to 25% and more than 60% for typical cable and overhead (OH) feeders, respectively. By additionally using active power curtailment of up to 3% of the annual yield, the HC can be increased by about 50% and 90% for the considered cable and OH feeder, respectively (purely rural feeders).

Hierarchical controls selection based on PV penetrations for voltage rise mitigation in a LV distribution network

In recent years, the penetration level of distributed energy resources (DER) in the low voltage (LV) networks are increasing rapidly which has resulted in causing the voltage rise problem, even at the far end customer point in distribution networks (DNs). This paper presents a coordinated hierarchical controls selection method for mitigating the overvoltage problem using available resources in DNs, for example, static synchronous compensators (STATCOM) and battery energy storage (BES) systems. The proposed method recommends the installation of new control devices, such as photovoltaic (PV) smart voltage source inverter (VSI) with reactive power compensation capability, residential BES installations, and power sharing among neighboring distributed generator (DG) units depending on PV penetration levels at the LV network. The requirements of the proposed installation of the compensation devices are based on three criteria: (i) higher PV penetration scenarios; (ii) satisfying relevant standards; and (iii) economic perspectives. The interactions among standard VSI (operated at unity power factor (pf)) and smart VSI (variable pf) are also considered in the proposed method to mitigate the voltage rise problems. The results show that only after exceeding certain PV penetrations, the LV network requires a coordinated operation from STATCOM/BES and advanced compensation devices to sustain terminal voltages within permissible (±6%) limits. The proposed method is verified with extensive case studies utilizing real PV irradiance and customer loads data with nonlinear dynamic DER models connected with an urban LV network in the PSCAD/EMTDC software environment.

Voltage Rise Mitigation by Use of Customer-Owned Controllable Load in Distribution System with Large Penetration of Photovoltaic Systems

Voltage Rise Mitigation by Use of Customer-Owned Controllable Load in Distribution System with Large Penetration of Photovoltaic Systems

Reactive Power Management for Voltage Rise Mitigation in Distribution Networks with Distributed Generation: a Command Governor Approach

Abstract: High penetration of Distributed Generation (DG) in Medium Voltage (MV) power grids is usually a reason of abrupt voltage raises. In this respect critical scenarios are represented by both low demand conditions and high power production from renewable sources. In order to cope with the possibly resulting voltage limits violation, a typical adopted approach is the disconnection of the distributed generators or the curtailment of the generated power leading to several disadvantages. To address this issue an online management of the reactive power of distributed generators is presented. The approach is based on Command Governor (CG) ideas and is aimed at solving a constrained voltage regulation problem in both centralized and distributed ways. The approach foresees an active coordination between some controllable devices of the grid, e.g. distributed generators, MV/HV transformers, in order to maintain relevant system variables within prescribed operative constraints in response to unexpected adverse conditions. Simulation results show that the proposed approach is more effective than approaches suggested by the current Italian norms on reactive power compensation.

A Voltage Rise Mitigation Strategy under Voltage Unbalance for a Grid-connected Photovoltaic System

This paper analyzes the effect of unbalanced voltage on voltage rise for a grid-connected photovoltaic (PV) system, and proposes a voltage rise mitigation strategy which injects negative-sequence currents to compensate the unbalanced voltage aiming especially to reduce the voltage rise. The paper also discusses how the averaged powers related to the injected negative-sequence currents are measured by the power meter. Simulation result confirms the superior performance of the proposed strategy over the classical method which suppresses the voltage rise by adjusting the power factor.

Community Energy Storage for Neutral Voltage Rise Mitigation in Four-Wire Multigrounded LV Feeders With Unbalanced Solar PV Allocation

The traditional neutral voltage problem in low-voltage (LV) four-wire multigrounded distribution networks can be aggravated due to an unbalanced allocation of one-phase photovoltaic (PV) units. Inherent limitations restrict the performance of the traditional strategies to mitigate the combined effect of load and PV unbalance. To overcome the shortcoming of traditional approaches, a new dynamic mitigation approach using community energy storage (CES) is proposed in this paper. A power balancing algorithm is developed to perform the balancing operation while minimizing power drawn from the CES. A charge/discharge control strategy is developed that will continuously balance and dynamically adjust the power exchange with the grid in a real time, and mitigate the neutral current and neutral voltage rise. To investigate the applicability of the proposed approach under physical time delays associated with battery and PV systems, a suitable dynamic model is developed. An Australian LV distribution system is used to verify the proposed approach under daylong variations of load and PV, and also during short-term variations of PV output caused by cloud passing.

Voltage rise mitigation for solar PV integration at LV grids

Solar energy from photovoltaic (PV) is among the fastest developing renewable energy systems worldwide. Driven by governmental subsidies and technological development, Europe has seen a fast expansion of solar PV in the last few years. Among the installed PV plants, most of them are situated at the distribution systems and bring various operational challenges such as power quality and power flow management. The paper discusses the modelling requirements for PV system integration studies, as well as the possible techniques for voltage rise mitigation at low voltage (LV) grids for increasing PV penetration. Potential solutions are listed and preliminary results are presented.

A Multi-Mode Control Strategy for VAr Support by Solar PV Inverters in Distribution Networks

This paper proposes a multi-purpose VAr control strategy for solar PV inverters for voltage support in distribution networks. The proposed strategy can be applied under various PV power generation conditions. The inverters will normally operate in a dynamic VAr compensation mode for voltage support (including low PV and no PV periods). During mid-day when PV has surplus power, the proposed strategy will control the PV inverters to absorb VAr for voltage rise mitigation using a droop characteristic approach. During passing clouds, the strategy will mitigate voltage fluctuations by ramp-rate control of inverter VAr output. A dynamic model of the proposed PV inverter control has been developed to analyze its performance in terms of fast VAr control and voltage support under various PV generation conditions. The results of the analysis performed on an Australian distribution system show that the proposed VAr control strategy can mitigate voltage rise, and improve the voltage profile despite potential vast changes in the sun irradiation during passing cloud and also in the absence of PV output during the evening.

軽い常時進み定力率運転とベクトルLDC制御の併用の配電線電圧上昇緩和と省エネルギーの効果

軽い常時進み定力率運転とベクトルLDC制御の併用の配電線電圧上昇緩和と省エネルギーの効果

Voltage Rise Mitigation in Distribution Network by Collaboration of PV's Constant Leading Power Factor Operation and Vector-LDC of a Distribution Transformer.

Voltage Rise Mitigation in Distribution Network by Collaboration of PV's Constant Leading Power Factor Operation and Vector-LDC of a Distribution Transformer.

Coordinated control of automated devices and photovoltaic generators for voltage rise mitigation in power distribution circuits

A coordinating, model-centric control strategy for mitigating voltage rise problems due to photovoltaic (PV) penetration into power distribution circuits is presented. The coordinating control objective is to maintain an optimum circuit voltage distribution and voltage schedule, where the optimum circuit operation is determined without PV generation on the circuit. In determining the optimum circuit voltage distribution and voltage schedule, the control strategy schedules utility controls, such as switched capacitor banks and voltage regulators, separate from PV inverter controls. Optimization addresses minimizing circuit losses and motion of utility controls. The coordinating control action provides control set-points to the PV inverters that are a function of the circuit loading or time-of-day and also the location of the PV inverter. Three PV penetration scenarios are considered, 10%, 20%, and 30%. Baselines with and without coordinating controls for circuit performance without PV generation are established, and these baselines are compared against the three PV penetration scenarios with and without coordinating control. Simulation results are compared and differences in voltage variations and circuit losses are considered along with differences in utility control motion. Results show that the coordinating control can solve the voltage rise problem while minimizing circuit losses and reducing utility control motion. The coordinating control will work with existing PV inverter controls that accept control set-points without having to modify the inverter controls.

Optimal battery sizing in photovoltaic based distributed generation using enhanced opposition-based firefly algorithm for voltage rise mitigation.

This paper presents the application of enhanced opposition-based firefly algorithm in obtaining the optimal battery energy storage systems (BESS) sizing in photovoltaic generation integrated radial distribution network in order to mitigate the voltage rise problem. Initially, the performance of the original firefly algorithm is enhanced by utilizing the opposition-based learning and introducing inertia weight. After evaluating the performance of the enhanced opposition-based firefly algorithm (EOFA) with fifteen benchmark functions, it is then adopted to determine the optimal size for BESS. Two optimization processes are conducted where the first optimization aims to obtain the optimal battery output power on hourly basis and the second optimization aims to obtain the optimal BESS capacity by considering the state of charge constraint of BESS. The effectiveness of the proposed method is validated by applying the algorithm to the 69-bus distribution system and by comparing the performance of EOFA with conventional firefly algorithm and gravitational search algorithm. Results show that EOFA has the best performance comparatively in terms of mitigating the voltage rise problem.

Autonomous scheduling of heat-pump water heaters for mitigating voltage rise caused by photovoltaic power generation systems

For mitigating negative impacts of high-penetration photovoltaic power generation system (PVS) on electric power system, sufficient capability for adjusting the apparent load fluctuation including PVS power supply as negative load is needed. The increase in the daytime electricity consumption, which follows the change in the aggregated power supply of high-penetration PVS, would be essential measure against negative impacts.In this study, we focus on the daytime operation of a heat-pump water heater (HPWH) as one of measures, and introduce a brief idea for autonomously scheduling the daytime operation of individual HPWH so that the change in the aggregated electricity consumption by a number of HPWHs follows the irradiance change in a day.By using the electricity and hot-water consumption data for a year, we demonstrate the effect of daytime operation in terms of the voltage rise mitigation in a power distribution network caused by the reverse power flow from high-penetration PVS. The result shows that the voltage rise can be mitigated by applying the daytime operation to HPWH of a household with PVS, while the under-voltage condition due to the unnecessary daytime operation can be avoided based on the next day weather forecast.

Improvement of Local Voltage in Feeders With Photovoltaic Using Electric Vehicles

In low-voltage (LV) feeders with high penetration of photovoltaic (PV), a major issue to be solved is voltage rise due to the active power injection. If no measures are taken, this may lead to generation's interruptions and to the malfunctioning of domestic appliances due to non-standard voltage profiles. This paper proposes a storage strategy to alleviate voltage rise in feeders with PV, using coordinated electric vehicle (EV) load as the storage solution. The voltage support strategy is easy to implement practically and it is demonstrated on a test feeder emulating a household with roof-mounted PV and an EV. The results show the effectiveness of using coordinated EV load in feeders with PV to mitigate voltage rise problems.

Distributed Energy Resources Integration Challenges in Low-Voltage Networks: Voltage Control Limitations and Risk of Cascading

The integration of distributed energy resources (DER) in low-voltage networks is expected to increase significantly in the next few years. It is known that the large-scale integration of DER in conventional low-voltage (LV) networks poses many challenges such as voltage rise. To mitigate voltage rise caused by DER, utilities are defining simple voltage regulation strategies such as disconnecting DER when phase voltages rise above a defined threshold. In this paper, we model LV networks as three-phase unbalanced circuits and illustrate that such local regulation strategies may cause the cascading of the DER in a feeder. We then propose an optimal control approach to avoid cascading and optimize DER availability. Local control approaches are discussed in the context of global DER availability and their limitations are illustrated.

Coordinated Control of Distributed Energy Storage System With Tap Changer Transformers for Voltage Rise Mitigation Under High Photovoltaic Penetration

This paper proposes a coordinated control of distributed energy storage system (ESS) with traditional voltage regulators including the on-load tap changer transformers (OLTC) and step voltage regulators (SVR) to solve the voltage rise problem caused by the high photovoltaic (PV) penetration in the low-voltage distribution network. The main objective of this coordinated control is to relieve the tap changer transformer operation stress, shave the distribution network peak load and decrease the transmission and distribution resistive power losses under high solar power penetration. The proposed control method limits the energy storage depth of discharge in order to meet a more than ten-year cycle life. A benchmark distribution network model was developed in the Real Time Digital Simulator (RTDS) and the simulation results from the studied cases verified the proposed coordinated control strategy. The experimental implementation of proposed control algorithms were developed based on a power hardware-in-the-loop (PHIL) test bed with a 22 kWh ESS, a smart meter, Labview controller, and RTDS. The experimental results were consistent with those obtained from simulation study.

Distributed Reactive Power Generation Control for Voltage Rise Mitigation in Distribution Networks

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.