Reactive Power Based Fault Ride Through Control of IBR-Dominated Distribution Networks Under Low WSCR

As a promising renewable alternative, the wind power is highly expected to contribute a significant part of generation in power systems in the future, but this also bring new integration related power quality issues, which mainly consist of voltage regulation and reactive power compensation. Wind power, as a rule, does not contribute to voltage regulation in the system. Induction machines are mostly used as generators in wind power based generations. Induction generators draw reactive power from the system to which they are connected. Therefore, the integration of wind power to power system networks; especially a weak distribution networks is one of the main concerns of the power system engineers. Voltage control and reactive power compensation in a weak distribution networks for integration of wind power represent main concern of this paper. The problem is viewed from MATLAB/Simulink simulation of weak distribution network and wind power integration in this network. Without reactive power compensation, the integration of wind power in a network causes voltage collapse in the system and under-voltage tripping of wind power generators. For dynamic reactive power compensation, when, STATCOM (Static Synchronous Compensator) is a used at a point of interconnection of wind farm and the network; the system absorbs the generated wind reactive power while maintaining its voltage level.

Background: With the continuous increase in the penetration rate of distributed generation (DG) in distribution networks, the pressure on energy supply has been effectively alleviated. However, its impact on the voltage of distribution networks is gradually becoming apparent, and traditional reactive power voltage support methods are struggling to meet the requirements for fast and flexible voltage regulation in modern distribution networks with high DG penetration. Objective: To accommodate the integration of DGs with high penetration rates and enhance the voltage support capability of the distribution network, an emergency voltage support scheme is proposed. The proposed scheme takes into account the impedance properties of the distribution network and focuses on low-voltage distribution networks. Method: This paper proposes a voltage support scheme for low-voltage distribution networks, taking into account the resistive characteristics of distribution lines. Based on the distribution network impedance ratio (R/X), the optimal active and reactive current reference values are estimated. A voltage support strategy is planned according to the severity of the voltage drop, providing coordinated voltage support by simultaneously delivering active and reactive power during voltage sags and fault conditions. Result: A digital-physical hybrid experimental platform and a simulation model of the low-voltage distribution network were established to validate the effectiveness of the proposed scheme. The results indicate that the voltage support capability of the proposed scheme is superior to that of traditional reactive power voltage support methods. Conclusion: The low-voltage distribution network voltage support scheme proposed in this paper considers the distribution network impedance ratio to calculate the required injected active and reactive power, thereby providing maximum support to the voltage. In addition, the active and reactive currents are adjusted according to the severity of the voltage drop using a droop curve. The effectiveness of the proposed method on the operation of the distribution network is validated through simulations. The scheme can effectively provide voltage support during voltage dips in the distribution network, preventing voltage instability.

A two‐layer control method is proposed for voltage and reactive power control in harmonic polluted distribution network with penetration of photovoltaic (PV) systems. Optimal scheduling of load tap changer and shunt capacitors for minimising energy losses and improving the power quality simultaneously are performed using P‐particle swarm optimisation (PSO) optimisation method. Here, the minimising cost of real power losses and improving the power quality criteria have been pursued as the goals of an optimisation problem. Considering load and PVs output forecast, the first‐layer control determines the optimal reactive power and control settings for all mechanical controllers. Hourly errors of load and power forecasts and mechanical control setting of the first layer are used to estimate optimised reactive power of PV in order to achieve maximum voltage regulation, reduce network losses and total harmonic distortion (THD). These data are trained a neural network (NN) to estimate optimised PV reactive power. This NN in the second layer is used to optimise the online reactive power setting based on online PV power. For more practical applications of the proposed method, simulation is carried out in a large distorted 37‐bus distribution system. The algorithm will increase use of renewable energies, reduce voltage fluctuations, THD, and wear and tear of mechanical equipment.

With the development of science and technology, there has been growing the grid size, the growing demand for electricity and the extent of increasing the electricity market.In this paper, a mathematical morphology and genetic algorithm based dynamic reactive power optimization method for distribution network is proposed.By means of constructing mathematical morphology filter, the binary image composed by allelic genes of chromosome is filtered and the problem that deals with the action times of voltage regulating devices for compensation is turned into filtering problem of discrete binary image.With further automate scheduling, distribution automation and unmanned substation reactive power optimization of distribution line running made an urgent request.Reactive power optimization can improve the voltage passing rate, increasing the reliability of the system, the power quality, and the system runs the security and economy of the perfect combination, very broad application prospects.

In electrical distribution network, load varies over the day, with very low load from midnight to early morning and peak values occurring in the evening due to the load demand by the consumer. This variation in load demand leads to variation in reactive power because most loads are inductive especially in industries where three phase industrial motors are used. In addition, Furthermore, the variation in reactive power affects current flow through the lines, transformers, generators and cause power losses in distribution network. Hence, there is the need to ensure reliable energy distribution even in the presence of load and reactive power variations. This research paper applied shunt switching capacitor for reactive power control of electrical distribution network using 11 kV distribution network located at Monatan, Ibadan, Oyo State Nigeria as a case study. Hourly load data of the network were collected to determine the reactive power of the network for stability evaluation. Capacitor Switching Compensation was incorporated into distribution network using KCL algorithm as power flow to form Capacitor Switching Compensation Model (CSCM) to improve the reactive power of the distribution network and simulation was carried out in MATLAB environment. The results showed that reactive power of the distribution network was 3.1. The CSCM improved the reactive power to 52 %. The study showed that incorporating capacitor switching as a compensation technique enhances the stability of the distribution network. Keywords: Electrical Distribution Network, Reactive Power, Capacitor Switching Compensation Model, Power Loss, Load Data, MATLAB. DOI: 10.7176/CEIS/13-4-03 Publication date: August 31 st 2022

More and more distributed generations (DGs) access to distribution networks makes the voltage regulation becomes more and more complicated. In order to solve the over limit problem of voltage, this paper proposes a method to optimize the reactive power and voltage of the distribution network by utilizing the reactive power capacity of energy storage. First, the influence of DG access on voltage and the reactive power capacity of energy storage are analyzed. Second, the coordination method of reactive power regulating resources in distribution network is proposed. Then, a voltage optimization model with energy storage participating in is established with the aim of minimizing the node voltage deviation in the distribution network and considering the equality and inequality constraints. Finally, the simulation results show that the proposed method can utilize the reactive power of energy storage and optimize the network voltage.

With the high penetration of distributed photovoltaics (DPVs) integrated into the distribution network, the voltage problem becomes a critical problem. At present, the resources in the current distribution network hardly satisfy the requirements of voltage regulation. However, the huge amount of DPVs in the distribution network could be a potential voltage regulation resource due to the controllable active power and reactive power. In this paper, a day-ahead centralized and intraday decentralized combined voltage control method is proposed for high penetration DPVs connected distribution Networks. In the part of day-ahead control, centralized compensation of the distribution network voltage is achieved by controlling the gear ratio of the capacitor/reactor group on an hourly scale. The intraday control part consists of decentralized local control based on DPVs and centralized control based on energy storage (ES) equipment. The reactive and active power of DPVs is controlled in a decentralized way by using local priority sensitivity control based on the coordination with capacitor optimization. Finally, simulations are performed to verify the performance of the method. The results indicate that this method can effectively solve the voltage problem caused by DPVs.

Unbalanced faults pose significant risks to photovoltaic power systems, leading to unsteady conditions in DC-link voltage and photovoltaic output power. Such photovoltaic system instabilities will, in turn, cause detrimental impact on power grid security. Therefore, the fault ride through for unbalanced faults has been an emerging and challenging area of research and development. This article presents a phase-coordinates approach for computing grid-connected current references directly from phase quantities to achieve effective fault ride through to alleviate the impact from unbalanced grid faults. The novelty lies in the development and use of the vector relationship between three-phase currents and active power, which avoids the complication in adopting negative-sequence components. The method is simple to implement and shows the advantages of high reliability and computational efficiency. Tests on a distribution grid with a large-scale photovoltaic plant have verified the effectiveness of the proposed ride through strategy in dealing with unbalanced faults.

In the current scenario of larger than ever penetration of renewable energy sources (RESs) in weak distribution networks, the individual power producers are required to participate in the grid voltage support functions. In this context, a hybrid voltage regulation strategy based on a normalized maximum Versoria criterion (NMVC) is developed in this paper. It involves coordinated control operation of the microgrid power sources using power converters. The microgrid consists of a doubly fed induction generator (DFIG) based wind power source, solar photovoltaic (SPV) source and battery energy storage (BES). The microgrid connected to low voltage (LV) weak distribution network with significant line resistances, results in abrupt rise in voltages during peak power production. This strategy utilizes BES for voltage support through its active power control (APC), primary operating mode. To protect BES from overcharging, a hybridization to primary operating mode is introduced, involving grid voltage support through reactive power control (RPC), secondary operating mode. The validation of the presented NMVC based voltage regulation strategy is performed through simulations.

The article presents a new method for voltage control in medium voltage distribution networks with dispersed generation. A linear mathematical model of a distribution network has been proposed. The model makes possible to optimally select feeding voltage of a medium-voltage network as well as reactive power in dispersed power sources according to the actual load and active power generation.

We studied the reactive power control strategy of distributed energy storage in distribution systems, improved reactive power support capacity, and enhanced system reliability and new energy carrying capacity. Firstly, the principles and methods of reactive power optimization in distribution networks are studied. Then, the principles and mechanisms of distributed energy storage participating in reactive power control in distribution networks are studied. Finally, the genetic algorithm optimization method for reactive power optimization in distribution networks is studied, including parameter setting, target selection, and genetic strategy improvement, providing support for fine control of reactive power and voltage in distribution systems and efficient operation. Through simulation analysis of the IEEE33 node system, it is shown that distributed energy storage can improve the reactive voltage level of the distribution system and promote the consumption of new energy.

Voltage control in distribution networks becomes increasingly important with an increasing penetration of distributed generation (DG). As distribution networks are much more resistive than transmission networks, the conventional technique of reactive power compensation in order to control the voltage cannot be applied very well. For that reason other voltage control techniques have to be applied. In this contribution several options for voltage control in distribution networks are analyzed and related to important grid parameters such as the short-circuit ratio and the X/R ratio of the grid. For networks with a high X/R ratio reactive power can be used for voltage control. For networks with a low X/R ratio several new voltage control techniques are proposed. These techniques are voltage control with active power, inserting a controllable inductance in the grid and series compensation by DG unit converters.

The proliferation of distributed generators (DGs) and electric vehicle charging stations (EVCSs) has brought voltage regulation challenges to distribution networks. This article proposes a distributed control algorithm to dispatch surplus reactive power from EVCSs and DGs for proper voltage regulation without violating their converters' capacities or stressing conventional voltage control devices, such as on-load tap changers (OLTCs). Further, an active power curtailment strategy is proposed for DGs to properly integrate OLTCs in voltage regulation when the reactive power support is deficient. The proposed control algorithms rely on the average consensus theory and sensitivity analysis to provide optimized voltage support while satisfying the agents' self-objectives. Simulation results of a typical distribution network confirm the effectiveness of the proposed distributed control algorithms in maintaining proper voltage regulation with minimum voltage support from EVCSs and DGs, and reduced daily tap operation for OLTC.

A TSO-DSO interactive mechanism is proposed to realize coordinated voltage support of transmission network by reactive power provision, activating flexibility of active distribution networks, such as distributed generations, flexible loads, reactive power compensators, etc. The mechanism consists of four stages: i) TSO sends reactive power request to DSOs; ii) Each DSO forms its reactive power quantity-price curve and sends to TSO; iii) TSO does a global optimization to achieve a voltage support scheme, incorporating its own reactive power provision devices and reactive power quantity-price curves; iv) Each DSO re-optimizes in its local area to reach the voltage support requirement. Based on this mechanism, the specific implementation approaches of the four stages are discussed, and a four-stage distributed algorithm is proposed. The case analysis demonstrates that the proposed mechanism and algorithm can effectively and accurately realize voltage support. Also, the TSO is able to achieve a more cost-effective scheme compared with independent voltage support while the active elements managed by DSOs achieve profits from participating in the coordinated voltage support. Specifically, in the test case presented in this paper, the coordinated scheme can save more than 50% costs and 25% reactive power requirements compared with the traditional one.

Today's power systems are in transformation process to a smarter grid via integration of distributed generation and intelligent loads, where advanced information and communication technology provides more reliable and efficient communication links. For purpose of dealing with the increasing dynamic parts of the smart grid and its corresponding cyber systems, we propose a control and communication co-design framework for Voltage/Var control (VVC) in distribution network, which consists of a communication protocol and an adaptive dynamic programming (ADP) based algorithm. To minimize voltage deviation and communication cost, we extend control interval by integration of an event-triggered mechanism. The effectiveness of proposed algorithm is demonstrated by a simulation using Matlab+NS-3 co-simulation in a distribution network.