Mitigation of Distribution Voltage Violations Using Single-Phase Residential Static VAr Compensators

An alternative method to support the voltage at the end of a distribution feeder using residential static VAR compensators (RSVCs) is presented. The distribution feeder and the RSVCs were modeled using OpenDSS and validated by comparing the results of measured data with the output of the model. Results show that the use of RSVCs on the low side of the service transformers is an efficient way to mitigate low- and high-voltage violations in the distribution feeder. During a onemonth evaluation of the system, the results show that the use of RSVCs was able to eliminate all voltage violations below 113 V and it reduced the number of voltage violations under 114 V by 88%

Demand-Side Load Management Using Single-Phase Residential Static VAR Compensators

Distribution systems are going through a structural transformation from being radially-operated simple systems to becoming more complex networks to operate in the presence of the distributed energy resources (DERs) with significant levels of penetration. It is predicted that the share of electricity generation from DERs will keep increasing as the world is moving away from the power generation involving carbon-emission and towards cleaner energy sources such as solar, wind, and biofuels. However, the unstable behavior of the renewables resources presents challenges to the already existing distribution systems. One such problem is when the distribution feeder experience variable power supply due to the unpredictable behavior of renewable resources. Therefore, it becomes difficult to maintain end-of-line (EOL) voltages within an acceptable range of the ANSI C84.1 Standard. Moreover, electric utility companies consider Conservation by Voltage Reduction (CVR) as a potential solution for managing peak power demand in distribution feeders. Conservation by Voltage Reduction is the implementation of a distribution voltage strategy whereby all distribution voltages are lowered to the minimum allowed by the equipment manufacturer. This strategy is rooted in the fact that many loads consume less power when they are fed with a voltage lower than nominal. Therefore, by implementing CVR, the utility companies can potentially reduce the peak power demand and can delay the up-gradation of the distribution feeder assets. To maximize the benefits from CVR, the whole distribution feeder must participate in regulating power to lower the demand during hours of demand. Hence, there is a need for a local solution that can regulate residential voltage levels from the first customer on the distribution feeder until the EOL of the distribution network. Such a solution will not only provide flexibility to electric utilities for better control over residential voltages but it can also maximize the benefits from CVR. This dissertation presents the concept of a closed-loop Residential Static VAR Compensator (RSVC) that will allow electric utility companies to locally regulate the voltage across the distribution feeder. The proposed RSVC is a novel smart-grid device that can regulate a residential load voltage with a fixed capacitor in shunt with a reactor controlled by two bi-directional switches. The two switches are turned on and off in a complementary manner using a pulse-width modulation (PWM) technique that allows the reactor to function as a continuously-variable inductor. The proposed RSVC has several advantages compared to a conventional thyristor-based Static VAR Compensator (SVC), such as a quasi-sinusoidal inductor current, sub-cycle reactive power controllability, lower footprint for reactive components, and its realization as a single-phase device. The closed-loop RSVC contains two regulation control loops: the primary control loop regulates the customer load voltage to any desired reference voltage within ANSI C84.1 (120 V nominal $\pm$ 5\%) and a secondary loop adjusting the reference voltage to track the point of minimum power consumption by the loads. This approach to CVR has the merit of adapting to the nature of the customer load, which may or may not decrease its energy consumption under a reduced voltage. This local approach to voltage regulation and CVR is a radical departure from current CVR strategies that have been in existence for over 30 years but have not been widely adopted by electric utilities due to high costs and technical challenges

Planning Tools for the Integration of Renewable Energy Sources Into Low- and Medium-Voltage Distribution Grids

This chapter presents two probabilistic planning tools developed for the long-term analysis of distribution networks. The first one focuses on the low-voltage (LV) level and the second one addresses the issues occurring in the medium-voltage (MV) grid. Both tools use Monte Carlo algorithms in order to simulate the distribution network, taking into account the stochastic nature of the loading parameters at its nodes. Section 1 introduces the probabilistic framework that focuses on the analysis of LV feeders with distributed photovoltaic (PV) generation using quarter-hourly smart metering data of load and generation at each node of a feeder. This probabilistic framework is evaluated by simulating a real LV feeder in Belgium considering its actual loading parameters and components. In order to demonstrate the interest of the presented framework for the distribution system operators (DSOs), the same feeder is then simulated considering future scenarios of higher PV integration as well as the application of mitigation solutions (reactive power control, P/V droop control thanks to a local management of PV inverters, etc.) to actual LV network operational issues arising from the integration of distributed PV generation. Section 2 introduces the second planning tool designed to help the DSO, making the best investment for alleviating the MV-network stressed conditions. Practically, this tool aims at finding the optimal positioning and sizing of the devices designed to improve the operation of the distribution grid. Then a centralized control of these facilities is implemented in order to assess the effectiveness of the proposed approach. The simulation is carried out under various load and generation profiles, while the evaluation criteria of the methodology are the probabilities of voltage violation, the presence of congestions and the total line losses

Analysis of Power Quality Problems on Nigerian 330 kV Power System Using Statcom with Voltage Sensitivity Index

Transmission system is the transportation of electrical energy from generating stations to load centers. However, increase usage of non-linear loads from the consumers has led to electrical Power Quality (PQ) problems which have negative impacts on the operation of the power system especially Nigerian power system. This research analyzed the PQ problem on Nigerian 330 kV power system. Newton-Raphson (NR) iterative method was used to performed load flow analysis on Nigerian 28-bus transmission systems. Then power injection model of the Static Synchronous Compensator (STATCOM) was incorporated to modify the NR mathematical model. The suitable placement for the STATCOM in the system was determined using Voltage Sensitivity Index (VSI) and simulation was done in MATLAB/SIMULINK. The results showed that, the suitable placements of STATCOM controller in the power system were buses 5, 8, 12 and 16. The corresponding STATCOM reactive power, sag voltage and sag duration for buses 5, 8, 12 and 16 were 72.56 MVar, 0.77454 p.u, 0.7336s; 65.35 Mvar, 0.7464 p.u,  0.7419 s; 50.86 Mvar, 0.7615 p.u, 0.6512 s and  53.75 MVar, 0.7442 p.u. 0.5972 s, respectively. Therefore, the results have established the importance of STATCOM with VSI in obtaining suitable solution for PQ problems on electrical power system. Keywords: Transmission System, Electrical Energy, Non-linear Load, Power Quality, Newton-Raphson, STATCOM, Voltage Stability Index. DOI: 10.7176/ISDE/12-6-03 Publication date:October 31st 2022

High- and Low-Voltage Mitigation in Distribution Systems Using Residential Static Volt-Ampere Reactive Compensators

Power distribution systems are experiencing a fast transformation from simple one-way radial feeders to complex systems with multiple sources and bidirectional power flows. The rapid increase of Distributed Generation (DG) connected to the distribution system over the last decade, especially solar photovoltaic (PV), has been the key element to this transformation. The variable nature of PV-based DG has increased the complexity of voltage regulation in distribution systems. Electric Utilities are facing an increasing number of voltage issues in distribution systems with high penetration of DGs, leading customers to experience voltage levels outside of range A of the ANSI C84.1 standard. Electric Utilities have to expend resources, both human and economic, to mitigate the voltage issues caused by the interconnection of DG. The economic impact of voltage issues can be considerable in some cases. Conventional methods to mitigate voltage issues in distribution systems, such as the addition of voltage regulators and capacitor banks, could be ineffective in mitigating localized voltage issues caused by high levels of DG penetration. Other mitigation options, such as increasing the conductor size and the operating voltage of the feeder, are expensive. There is a clear need in the industry to locally solve voltage issues economically. In this dissertation, a new device, a Residential Static Volt-Ampere Reactive Compensator (RSVC), is proposed. The RSVC is used to mitigate low and high voltage issues by deploying them in a feeder with a high DG penetration level. This dissertation will investigate the interaction between solar inverters, voltage regulators and capacitor banks with the proposed RSVC. In order to reduce the number of buses to be analysed, the use of loss sensitivity factors will determine the candidate buses to host a RSVC. The results of this dissertation show that the use of RSVCs is able to mitigate low and high voltage conditions. Simulation results show that the RSVCs are able to control the voltage by absorbing and injecting reactive power according to the voltage seen at their terminals. Similar commercially available devices are not able to handle the injection and absorption of reactive power and are limited to handle either injection of reactive power or absorption of reactive power. The most common devices provide the capability of injecting reactive power

Impact of distributed generation on protection and voltage regulation of distribution systems : a review

During recent decades with the power system restructuring process, centralized energy sources are being replaced with decentralized ones. This phenomenon has resulted in a novel concept in electric power systems, particularly in distribution systems, known as Distributed Generation (DG). On one hand, utilizing DG is important for secure power generation and reducing power losses. On the other hand, widespread use of such technologies introduces new challenges to power systems such as their optimal location, protection devices' settings, voltage regulation, and Power Quality (PQ) issues. Another key point which needs to be considered relates to specific DG technologies based on Renewable Energy Sources (RESs), such as wind and solar, due to their uncertain power generation. In this regard, this paper provides a comprehensive review of different types of DG and investigates the newly emerging challenges arising in the presence of DG in electrical grids.fi=vertaisarvioitu|en=peerReviewed

Optimal d-statcom placement tool for low voltage grids

In low-voltage grids with a wide spread of domestic and/or small commercial consumers, mostly single-phase, problems can appear due to unbalanced power consumption between the different phases. These problems are mainly caused due to voltage unbalances between phases and the increase in distribution losses. This phenomenon occurs more frequently at the end of highly radial grids and can be stressed by the installation of renewable generators next to the consumers. Amongst the various techniques that have been proposed to solve this problem, this article explores the use of a D-STATCOM, presenting and testing a new method for the optimal location of this type of D-FACT. The developed method starts from a detailed analysis of the existing voltage unbalances in a distribution network and identifies the optimal location of the D-STATCOM (i.e., the one that reduces these unbalances while reducing energy losses). The developed method has been successfully tested for one year at four real European locations with different characteristics and different kinds of users. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Distribution network development planning with quality of supply (QOS) costing

Includes bibliographical references.The report outlines details of research in distribution network development with consideration of costs due to quality. Network planning methods are diverse with the common objective of establishing minimum cost options without violating network constraints. The selected network alternative is directed to meet customer requirements. Network planning models have evolved from consideration of simplistic models to multi variable and more realistic approaches. It is not always possible to achieve the desired outcome because planning is a difficult and complex task. There are usually uncertainties due to vague or no information available about the long-term (15-20 years) planning. The uncertainties generally result in risks, which have to be sufficiently analysed before reaching planning decisions. The recently proposed Minimum Risk Criterion is not a preferred risk resolution approach because it suggests that utilities should not establish expensive networks due to cost risk. Uncertainty modeling approaches based on fuzzy logic are proposed as the solution for analysis of uncertain conditions where very limited information is available. Costs in distribution lines are usually due to capital investment and operating costs. Distribution capital costs are primarily due to cost of conductor, s ucture and insulator. The cost of conductor and structure varies with size and type. Insulator costs do not vary significantly with variations in insulator type and properties. Quality related costs are a relatively new concept in distribution costing and are developed in the research. They are primarily due to mitigation, condition monitoring and interruptions. Quality mitigation costs are defined in the mitigation cost models in Figure 4- 8 and Figure 4- 9. The impact cost values in the models were established on the basis of assumptions, which require further research. According to CTLab [12], quality-monitoring equipment costs could vary from R50, 000 to R250, 000. Interruption costs are incurred through penalty cost and revenue losses. The penalty cost is similar to the revenue loss cost in many respects but is incurred when the standard limits are violated. Revenue loss costs are applicable whenever the frequency or voltage deviates from the nominal. It may be preferred to accept revenue losses where mitigation is expensive

Coordinated Volt-Var control in multiple smart inverters in Smart Distribution Networks for Voltage Regulation.

The inevitable growing demand for electrical power, depleting sources of conventional power generation, and world wide concern about global warming are major factors to boost the trend of renewable integration in grids. This rising trend is causing many technical and operational challenges where one of the most prominent problem is the overvoltage caused by distributed generation units, interfaced at the consumer end, and power injections at random nodes. This in contrast with predefined power flows of conventional grids gives rise to bidirectional power flows that demand for modern, coordinated and robust voltage regulation scheme with minimal communication infrastructure. A centralized, coordinated, differential evolution based Volt/VAR regulation scheme is proposed to eliminate the voltage deviations caused by excessive photovoltaic integration in distribution systems. Time step simulation utilizing OpenDSS interfaced with MATLAB on standard IEEE-123 feeder are implemented to test the effectiveness of the proposed scheme

Analysis And Mitigation Of The Impacts Of Delays In Control Of Power Systems With Renewable Energy Sources

ABSTRACT Analysis and Mitigation of the Impacts of Delays in Control of Power Systems with Renewable Energy Sources by Chang Fu Apr. 2019 Advisor : Dr. Caisheng Wang Major : Electrical and Computer Engineering Degree : Doctor of Philosophy With the integration of renewable resources, electric vehicles and other uncertain resources into power grid, varieties of control topology and algorithms have been proposed to increase the stability and reliability of the operation system. Load modeling is an critical part in such analysis since it significantly impacts the accuracy of the simulation in power system, as well as stability and reliability analysis. Traditional power system composite load model parameter identification problems can be essentially ascribed to optimization problems, and the identied parameters are point estimations subject to dierent constraints. These conventional point estimation based composite load modeling approaches suer from disturbances and noises and provide limited information of the system dynamics. In this thesis, a statistic (Bayesian Estimation) based distribution estimation approach is proposed for composite load models, including static (ZIP) and dynamic (Induction Motor) parts, by implementing Gibbs sampling. The proposed method provides a distribution estimation of coecients for load models and is robust to measurement errors. The overvoltage issue is another urgent issues need to be addressed, especially in a high PV penetration level system. Various approaches including the real power control through photovoltaic (PV) inverters have been proposed to mitigate such impact, however, most of the existing methods did not include communication delays in the control loop. Communication delays, short or long, are inevitable in the PV voltage regulation loop and can not only deteriorate the system performance with undesired voltage quality but also cause system instability. In this thesis, a method is presented to convert the overvoltage control problem via PV inverters for multiple PVs into a problem of single-input-single-output (SISO) systems. The method can handle multiple PVs and dierent communication delays. The impact of communication delays is also systematically analyzed and the maximum tolerable delay is rigorously obtained. Dierent from linear matrix inequality (LMI) techniques that have been extensively studied in handling systems with communication delays, the proposed method gives the necessary and sucient condition for obtaining a controller and the design procedure is explicitly and constructively given in the paper. The effectiveness of the proposed method is veried by simulation studies on a distribution feeder and the widely-used 33-bus distribution test system. The similar design strategy can be utilized to mitigate delay impacts in Load frequency control (LFC) as well. LFC has been considered as one of the most important frequency regulation mechanisms in modern power system. One of the inevitable problems involved in LFC over a wide area is communication delay. In this thesis, an alternative design method is proposed to devise delay compensators for LFC in one or multiple control areas. For one-area LFC, a sucient and necessary condition is given for designing a delay compensator. For multiarea LFC with area control errors (ACEs), it is demonstrated that each control area can have its delay controller designed as that in a one-area system if the index of coupling among the areas is below the threshold value determined by the small gain theorem. Effectiveness of the proposed method is veried by simulation studies on LFCs with communication delays in one and multiple interconnected areas with and without time-varying delays, respectively