Voltage Control In Distribution Systems Research Articles

Online Voltage Control in Distribution Systems With Multiple Voltage Regulating Devices

Voltage regulation in distribution systems is typically performed with the aid of multiple voltage regulating devices, such as on-load tap changer and step voltage regulators. These devices are conventionally tuned and locally coordinated using Volt/VAR optimization strategies in accordance with the time-graded operation. However, in case of distribution systems with distributed generation (DG), there could be a possibility of simultaneous responses of DG and multiple voltage regulators for correcting the target bus voltage, thereby resulting in operational conflicts. This paper proposes an online voltage control strategy for a realistic distribution system containing a synchronous machine-based renewable DG unit and other voltage regulating devices. The proposed strategy minimizes the operational conflicts by prioritizing the operations of different regulating devices while maximizing the voltage regulation support by the DG. It is tested on an interconnected medium voltage distribution system, present in New South Wales, Australia, through time-domain simulation studies. The results have demonstrated that voltage control for a distribution feeder can effectively be achieved on a real-time basis through the application of the proposed control strategy.

Guest Editorial: Special section on real-time applications of intelligent methods in sustainable power and energy systems

The 16 papers in this special section address distribution system voltage control, load management, optimization and control of wind, system voltage support through responsive demands, frequency support from wind, and elements of control of microgrid.

Decision making in fuzzy environment and multicriteria power engineering problems

This paper presents results of research into the use of the Bellman–Zadeh approach to decision making in a fuzzy environment for solving multicriteria power engineering problems. The application of the approach conforms to the principle of guaranteed result and provides constructive lines in computationally effective obtaining harmonious solutions on the basis of solving associated maxmin problems. The presented results are universally applicable and are already being used to solve diverse classes of power engineering problems. It is illustrated by considering problems of power and energy shortage allocation, power system operation, optimization of network configuration in distribution systems, and energetically effective voltage control in distribution systems.

Performance Comparison of VSC-Based Shunt and Series Compensators Used for Load Voltage Control in Distribution Systems

In this paper, the performance of voltage-source converter-based shunt and series compensators used for load voltage control in electrical power distribution systems has been analyzed and compared, when a nonlinear load is connected across the load bus. The comparison has been made based on the closed-loop frequency response characteristics of the compensated distribution system. A distribution static compensator (DSTATCOM) as a shunt device and a dynamic voltage restorer (DVR) as a series device are considered in the voltage-control mode for the comparison. The power-quality problems which these compensator address include voltage sags/swells, load voltage harmonic distortions, and unbalancing. The effect of various system parameters on the control performance of the compensator can be studied using the proposed analysis. In particular, the performance of the two compensators are compared with the strong ac supply (stiff source) and weak ac-supply (non-stiff source) distribution system. The experimental verification of the analytical results derived has been obtained using a laboratory model of the single-phase DSTATCOM and DVR. A generalized converter topology using a cascaded multilevel inverter has been proposed for the medium-voltage distribution system. Simulation studies have been performed in the PSCAD/EMTDC software to verify the results in the three-phase system.

Optimal voltage control in distribution systems using PV generators

Recently, renewable energy technologies such as wind turbine generators and photovoltaic systems have been introduced as distributed generation. The connection of large number of distributed generators causes voltage deviation beyond the statutory range in a distribution system. In this paper, a methodology for voltage control in proposed by using the tap changing transformers and the inverters interfaced with the distributed generators. In the proposed method, information of the voltage and power is collected via a communication network. Based on these information, the optimal reference values are calculated at the control center, and sent to the transformers and the inverters. The proposed method accomplishes a coordinated operation among the control equipments and reduces the voltage deviation. Effectiveness of the proposed method is verified by the numerical simulation results.

Optimal voltage control in distribution systems with coordination of distribution installations

In recent years, distributed generations based on natural energy or co-generation systems are increasing due to global warming and reduction of fossil fuels. Many of the distributed generations are set up in the vicinity of customers, with the advantage that this decreases transmission losses and transmission capacity. However, output power generated from renewable energy such as wind power and photovoltaics, is influenced by weather conditions. Therefore if the distributed generation increases with conventional control schemes, the voltage variation in a distribution system becomes a serious problem. In this paper, an optimal control method of distribution voltage with coordination of distributed installations, such as On Load Tap Changer (OLTC), Step Voltage Regulator (SVR), Shunt Capacitor (SC), Shunt Reactor (ShR), and Static Var Compensator (SVC), is proposed. In this research, the communication infrastructure is assumed to be widespread in the distribution network. The proposed technique combines genetic algorithm (GA) and Tabu search (TS) to determine the control operation. In order to confirm the validity of the proposed method, simulation results are presented for a distribution network model with distributed (photovoltaic) generation.

無効電力出力分担を考慮した配電系統の電圧制御法

無効電力出力分担を考慮した配電系統の電圧制御法

Reactive Power and Voltage Control in Distribution Systems With Limited Switching Operations

An algorithm based on a nonlinear interior-point method and discretization penalties is proposed in this paper for the solution of the mixed-integer nonlinear programming (MINLP) problem associated with reactive power and voltage control in distribution systems to minimize daily energy losses, with time-related constraints being considered. Some of these constraints represent limits on the number of switching operations of transformer load tap changers (LTCs) and capacitors, which are modeled as discrete control variables. The discrete variables are treated here as continuous variables during the solution process, thus transforming the MINLP problem into an NLP problem that can be more efficiently solved exploiting its highly sparse matrix structure; a strategy is developed to round these variables off to their nearest discrete values, so that daily switching operation limits are properly met. The proposed method is compared with respect to other well-known MINLP solution methods, namely, a genetic algorithm and the popular GAMS MINLP solvers BARON and DICOPT. The effectiveness of the proposed method is demonstrated in the well-known PG&E 69-bus distribution network and a real distribution system in the city of Guangzhou, China, where the proposed technique has been in operation since 2003.

Fuzzy multi-objective algorithm for multiple solution of distribution systems voltage control

This paper is devoted to the solution of voltage control in distribution systems, in the presence of uncertainties. The proposed solution is based on the multi-objective algorithm that takes into account active power losses, ‘soft’ voltage constraints, supply end voltage quality and variations of control resource variables. Uncertain input data and optimization criteria are specified in linguistic forms, translated to corresponding fuzzy sets. The selection and optimal setting of basic system voltage control resources is made for two mutually related time-horizons within annual operation planning and daily operation. The solution technique for the specified discrete-type combinatorial optimization problem is fuzzy dynamic programming, with the optimization criterion including the maximization of their minimum satisfaction degree and maximization of the sum of these minimums. The effectiveness and robustness of the proposed fuzzy multi-objective algorithm is verified on the test example, taken from the real distribution system of Serbia.

Application of double-layer capacitor technology to static condensers for distribution system voltage control

Static condensers may be utilized to mitigate many power quality problems in distribution systems. The condenser requires some type of energy storage such as a battery, a superconducting magnetic system, or a capacitor. The use of double-layer capacitors in static condensers is examined in this paper. These capacitors are characterized by high values of capacitance and equivalent parallel resistance and low values of equivalent series resistance. Double-layer capacitor technology is discussed and equivalent circuit models are presented. Test results for a 2.3 V, 470 F double-layer capacitor are presented to demonstrate how operation in a static condenser may affect capacitor performance. Design considerations for the use of this technology in a static condenser are discussed. Operation of a static condenser employing double-layer capacitors is illustrated using EMTP.

Distribution System Primary-Feeder Voltage Control III-Computer Program Application

Two companion papers1,2 discuss the engineering problems associated with distribution-system voltage control and describe a digital computer program for engineering investigations of alternative methods. The present paper 1. describes and evaluates the distribution-system voltage-control practices and method of primary-feeder analysis followed on the American Gas and Electric Company (AGE) System, 2. illustrates how the computer program was applied to a specific system problem, and 3. discusses possible modifications and extensions of the technique. It is concluded that the computer program may find application on the AGE System but that additional experience must be gained in its use to fully evaluate its potentialities.