Power System Voltage Control Research Articles

Modeling of SVC Controller based on Adaptive PID Controller using Neural Networks

The Flexible AC Transmission System (FACTS) technology is a promising technology to achieve complete deregulation of power system based on power electronic devices, used to enhance the existing transmission capabilities in order to make the system flexible and independent in operation then the system will be kept within limits without affecting the stability. Complete closed-loop smooth control of voltage can be achieved using shunt connected FACTS devices. Static VAR Compensator (SVC) is one of the shunt connected devices, which can be utilized for the purpose of voltage and reactive power control in power systems. In this paper the considered structure of SVC consists of (TCR-FC) which is applied at SMIB system model, the dynamic equations for the (SMIB-SVC) model will be presented, the system equations expressed in terms of state space equations then by using MATLAB the plant of the system model will be presented under various loading conditions. A Neuro-PID controller model has been developed to improve on the response and performance of a conventional Proportional plus Integral plus Derivative (PID) controller which control the response of the plant model by developing a self-tuning/adaptive Neural-PID controller. The proposed Neuro-controller was developed using the back propagation algorithm. The ANN based PID (ANNPID) controller compared with ANN controller through MATLAB simulation results. Comparison of performance responses of ANN controller and ANN-PID controller show that ANN-PID controller has quite satisfactory generalization capability, feasibility and reliability, as well as the accuracy in the system; the superiority of the performance of ANN over PID controller is highlighted under various loading conditions.

A Hybrid Predictive Control Strategy for the Coordinated Voltage

The substation is one of the most important nodes for the power system voltage control. Its dynamic behavior is usually characterized by the interaction of dynamic load models, describing continues variables governed by differential equations, and of discrete controllers and coordinated logic, describing symbolic variables governed by discrete behaviors, logic rules and switching mechanisms. Therefore, the operation and control of the substation is a typical hybrid dynamic system. To make an effective voltage coordinated control in substation, this paper proposed a hybrid predictive control strategy. First, the discrete-time hybrid automata model was given for describing the hybrid voltage control system in substation. Then, by using the voltage-security control constrain instead of the goal of voltage-security control, the voltage coordinated control problem can be converted to a minimization cost problem on the premise of the voltage-security control, based on the technology of the MPC. And, for the discrete control characteristics and different control delays of multi-controllers, a branch and search algorithm was designed to solve the hybrid predictive control problem. This proposed algorithm is suitable for the voltage predictive control of substation, which have less control variables and different controllers’ delays. Finally, the coordinated controller was designed on Dymola. And the example of BPA test system three generations and ten buses included was given for simulation analysis and the verification by the proposed approach for substation coordinated voltage control. The results of simulation showed that the proposed control strategy in the paper is feasible.

Research on the AVC Testing Platform for the Regional Grid based on Real-Time Digital Simulator (RTDS)

The automatic voltage control (AVC) relay provides real-time automatic control for the on-load transformer tap changer (OLTC), which is widely used for power system voltage monitoring and control purposes throughout the world. However, there are no uniform testing standards for the AVC system, and the lack of on-site inspection means has stimulated the introduction of the real-time digital simulator (RTDS)-based testing platform. This paper introduces the testing platform of the AVC controller based on the RTDS. The circuit model of the regional power grid is established, and the OLTC and the reactive power compensation devices are also incorporated. The intermediate data conversion device is utilized for bi-directional data exchange of the remote meter and control signals between the RTDS and the AVC system. The principle of the AVC voltage regulation and the RTDS-based AVC testing platform are introduced, followed by the data flow of the OLTC and capacitor/inductor banks, which formulates the foundation for closed-loop testing of the AVC control system for the electric power system. DOI: http://dx.doi.org/10.11591/telkomnika.v11i1.1677

Artificial Neural Network Applied to The Problem of Secondary Voltage Control

This paper presents the design of a controller based on an Artificial Neural Network (ANN) for the problem of the Secondary Voltage Control (SVC) in Electrical Power Systems (EPS). The design is based on the concept of Optimal Power Flow (OPF) and Pilots Nodes (PN), the obtained Controller is applied to a study case in order to validate the result. Finally the influence of various parameters that make the topology of a Neural Network are analyzed.

Voltage Coordination via Communication in Large-Scale Multi-Area Power Systems. Part I: Principal

This two-part paper deals with the coordination of the control actions in a network of many interacting components, where each component is controlled by independent control agents. As a case study we consider voltage control in large electric power systems, where ever-increasing pressures from the liberalization and globalization of the electricity market has led to partitioning the power system into multiple areas each operated by an independent Transmission System Operator (TSO). Coordination of local control actions taken by those TSOs is a very challenging problem as poorly coordinated operation of TSOs may endanger the power system security by increasing the risk of blackouts. This coordination problem involves many other issues such as communication, abstraction and last but not least optimization. This first part of the paper is devoted to the principals of the coordination control, addressing some of those issues using as a case study the problem of coordination control for avoiding voltage collapse in large-scale multi-area power systems.

Voltage Coordination via Communication in Large-Scale Multi-Area Power Systems. Part II: Simulation Results

This two-part paper deals with the coordination of the control actions in a network of many interacting components, where each component is controlled by independent control agents. As a case study we consider voltage control in large electric power systems where ever-increasing pressures from the liberalization and globalization of the electricity market has led to partitioning the power system into multiple areas each operated by an independent Transmission System Operator (TSO). Coordination of local control actions taken by those TSOs is a very challenging problem as poorly coordinated operation of TSOs may endanger the power system security by increasing the risk of blackouts. This second part of the paper presents simulation results on a 12-bus 3-area test system, using the distributed model predictive control paradigm in order to design a coordinating model-based feedback controller. Coordination requires that each agent has some information on what the future evolution of its power flows to and from its neighbors will be. It will be shown that how the communication between agents can avoid voltage collapse in circumstances where classical uncoordinated controllers fail.

Power System Voltage and Reactive Power Control by means of Multi-agent Approach

In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipments are installed in optimal locations throughout the power system network and a variety of methods of voltage and reactive control are employed. The proposed system divided the traditional method to control voltage and reactive power into two sub problems: “voltage control” to adjust the secondary bus voltage of substations, and “reactive power control” to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to cooperate “voltage control” and “reactive power control”. In order to verify the performance of the proposed method, it has been applied to the model network system. The results confirm that our proposed method is able to control violent fluctuations in load.

Voltage control for static var compensator using novel optimal nonlinear PI

Static var compensators (SVCs) are used for voltage and reactive power control in power systems. In this paper, we will consider the structure of SVCs that mainly consists of Y-connection of mechanically-switched capacitor (MSC) and delta connection of thyrister-controlled reactor (TCR). First, the control model of SVC was established in this paper. Then, a novel optimal nonlinear voltage controller for SVCs is proposed. The proposed SVC voltage controller consists of a nonlinear function and a conventional PI controller. The improved simplex method (SPX) is presented to adjust and optimize the parameters of the nonlinear PI controller in real-time, and to make transient state response procedure of SVC optimum. The integration of time multiplied absolute error (ITAE) is adopted as the optimized objective function of SPX. Simulation and engineering application results show that the proposed voltage control method is able to track reference voltage value of SVC immediately. It also demonstrates that the whole SVC control system can synthetically compensate reactive power.

A Novel Hybrid Optimization Algorithm Based on Multi-Agent and Particle Swarm

A novel multi-agent particle swarm optimization algorithm (MAI'SO) is proposed for optimal reactive power dispatch and voltage control of power system. The method integrates multi-agent system (MAS) and particle swarm optimization algorithm (PSO). An agent in MAI.SO represents a particle to PSO and a candidate solution to the optimization problem. All agents live in a lattice-like environment, with each agent fixed on a lattice-point. In order to decrease fitness value, quickly, agents compete and cooperate with their neighbors. and they can also use knowledge. Making use of these agent interactions and evolution mechanism of I.SO. MAPSO realizes the purpose of' minimizing the value of' objective function. MAPSO applied for optimal reactive power is evaluated on an IEEE 30-bus power system. It is shown that the proposed approach converges to better solutions much faster than the earlier reported approaches

Reactive power optimization with artificial bee colony algorithm

Reactive power optimization (RPO) is an important issue for providing the secure and economic run of the power systems. The importance of reactive power planning on economic profit and secure running has been increasing, because of the increasing fuel costs and investment funds. It is also quite important for an electric operator to provide voltage in a specified range for the customers. As such, RPO provides voltage control in power systems. Furthermore, it is used for decreasing active power loss and making better power coefficents. In this study, multi-objective RPO was used considering voltage deviations of buses, active power losses and reactive power generator costs. In this study, a new metaheuristic optimization method, which is an artificial bee colony (ABC), was used for the optimization. However, ABC was applied on ten bus system and the results were compared with the improving strength pareto evolutionary algorithm. It was observed that the system runs more effectively and economically with the results found with ABC. Key words: Artificial bee colony, reactive power optimization, active power loss.

KOHONEN NEURAL NETWORK CLUSTERING FOR VOLTAGE CONTROL IN POWER SYSTEMS

Clustering a power system is very useful for the purpose of voltage stability control. However, the methods have developed usually have computational inefficiency. This paper presents a new cluster bus technique using Kohonen neural network for the purpose of forming bus clusters in power systems from the voltage stability viewpoint. This cluster formation will simplify voltage control in power system. With this proposed Kohonen algorithm, a large bus system will be partitioned into a small bus groups that have a coherence V, �, P and Q. The maximum number of area clusters will be formed need for voltage stability needed. The proposed technique was tested on IEEE 39 bus system by considering two contingency namely load increased and line outage by using voltage collapse analysis. This formation will be compared with the Learning Vector Quantization (LVQ) algorithm. The results showed the proposed technique produces four clusters on contingency load load increased and three clusters online outage contingency on IEEE 39 bus system as shown by the LVQ.

A Multi-agent-based voltage control in power systems using distributed reinforcement learning

In this paper we show the application of multi-agent modeling and simulation with distributed reinforcement learning to one of the major problems in power system operations, i.e. voltage control. In this research some agents in the power network work together to provide a desirable voltage profile, using a combination of multi-agent system (MAS) technology and some of the reinforcement learning approaches. In this schema, individual agents who are assigned to voltage controller devices in the power system learn from their experiences to control the system voltage, and also cooperate and communicate with each other to satisfy the whole team goals. A detailed evaluation of methods for controlling voltage in power systems, including multi-agent coordination and distributed reinforcement learning (DRL), demonstrates that this framework yields effective plans, good agent coordination, and successful implementation. In the proposed approach, agent development and communication simulation have been carried out in the Java Agent Development (JADE) framework.

Implementation of Cascade Multilevel Inverter-based STATCOM

This paper deals with the real time implementation of 11-level cascade multilevel inverter-based STATCOM using personal computer (PC) and ADD-ON cards for power system voltage control at the point of common coupling. Complete hardware and software development procedures have been explained in depth for direct as well as indirect control schemes. Experimental results are presented and it is shown that voltage control is achieved using cascade multilevel inverter based STATCOM, thus verifying the very basic purpose of STATCOM. Real time implementation using PC-based control technique has certain merits over digital signal processor based implementation, and some of these merits are high processing speed and low cost of implementation; therefore, PC-based implementation can be used in industry as well as for utility applications.

An unified external network equivalent in steady-state security assessment

The basic objective of this paper is to present the relevant methodological and practical aspects of forming the unified external network equivalent. This equivalent consistently respects the effects of primary voltage and frequency control of external power system, including the real possibilities and limitations, as well as the effects of possible action of under frequency load shedding or under frequency protection of generator. The first practical experience in the application of the equivalent has been gained on an example of the synchronous parallel operation of the 2nd UCTE Synchronous Zone. The results obtained show a very good accuracy of unified external network equivalent formed and also show the very high speed of steady-state security assessment in context of real interconnection.

Power system reactive compensation: evaluation of expansion plans taking into account electromagnetic transient restrictions

In this paper, the authors present developments regarding Power System Capacitive Shunt Reactive Compensation and Voltage Control, with respect to Expansion Activities, in an Electromagnetic Transient context. The definition of the amount and location of shunt reactive compensation to be installed in power systems considers several aspects, as reactive power optimization, short circuit calculations, voltage stability and harmonic analyses, among others. Different alternatives must be evaluated, regarding their impact (positive and negative) to system behavior, in order to select the most adequate compensation. Expansion decision process usually does not include studies about the transient impact of reactive shunt compensation caused by switching operation. Traditionally, this is done only after expansion definition, when the detailed project is elaborated, mainly to prepare equipment specifications. In this paper, it is proposed an innovative procedure to include a technical evaluation of different shunt compensation based on a preview of the overvoltage and overcurrent values caused by the corresponding capacitors bank switching. The new methodology is designed to (i) indicate the critical system buses that must be carefully investigated, considering transient behavior, and (ii) promote the adequate shunt compensation adjust. The proposed procedure is detailed and results of its application in real systems are presented.

Hierarchical Coordinated Control for Power System Voltage Using Linear Temporal Logic

The paper proposed an approach to study the power system voltage coordinated control using Linear Temporal Logic (LTL). First, the hybrid Automata model for power system voltage control was given, and a hierarchical coordinated voltage control framework was described in detail. In the hierarchical control structure, the high layer is the coordinated layer for global voltage control, and the low layer is the power system controlled. Then, the paper introduced the LTL language, its specification formula and basic method for control. In the high layer, global voltage coordinated control specification was defined by LTL specification formula. In order to implement system voltage coordinated control, the LTL specification formula was transformed into hybrid Automata model by the proposed algorithms. The hybrid Automata in high layer could coordinate the different distributed voltage controller, and have constituted a closed loop global voltage control system satisfied the LTL specification formula. Finally, a simple example of power system voltage control include the OLTC controller, the switched capacitor controller and the under-voltage shedding load controller was given for simulating analysis and verification by the proposed approach for power system coordinated voltage control. The results of simulation showed that the proposed method in the paper is feasible.

Robustness and coordination in voltage control of large-scale power systems

In this paper it is shown how the robustness and the coordination of the voltage regulation actions for the transmission grid can be improved. Simpler approaches which ensure higher robustness and performances can be used if the control objectives are pursued at two hierarchical levels of different nature. Also, this is a way to coordinate means of control of different nature with a sufficient time and methodological separation in order to avoid negative mutual influence. At the first level, called the static level, optimal reachable set-points are computed for the second control level, called the dynamic level. The static level can be combined with the shunt reactive power compensation. The system non-linearities are taken into account at the static level while the dynamic level is a linear robust predictive control which takes into account the presence of asynchronous transmission delays. The predictive control strategy is based on the separation property; the output delays are handled using an original steady-state Kalman predictor of order equal to the length of the state of the system without delays. The robustness is improved at the dynamic level against uncertain delays, parametric uncertainties (like, e.g., moderate topological errors and load variations not taken into account in the control model) and unmodelled dynamics. The two-level organisation of the control allows, on one hand, to take into account the important evolutions of the system (like, e.g., large and known topological and load changes) and, on the other hand, a coherent hybrid reactive power control: the switched control of the grid shunt compensation for the reactive power is done at the static level while the reactive power injection provided by the generators is continuously handled at the dynamic level. This is a theoretical analysis of how concepts of automatic control and voltage regulation of power systems can be combined. To be applied as a control scheme, the results presented here should be adapted to a specific context (particularities of the power system and of the organisation of the power industry). They can be used, eventually in conjunction with other improvements, to existing horizontally-organised interconnections (in which all generators of a controlled region can be easily managed since owned by the same utility) or to face specific requirements of moving to the open access in the electric power industry like, e.g., tolerating simplified models in order to cover larger regions, taking into account the interaction between regions, recalibrating set-points, assisting human operator when necessary or facilitating implementation of mechanisms for the management of the reactive power based on price signals.

New control approach for a PV-diesel autonomous power system

A new control scheme for the hybrid photovoltaic-diesel single-phase autonomous power system is proposed. The main advantage of this scheme is that the voltage control is accomplished by the interface inverter without need to the automatic voltage regulator of the diesel-driven generator. Unlike three-phase systems, frequency and voltage control in single-phase autonomous power systems imposes additional complexity. This is due to the pulsating nature of the single-phase loads instantaneous power at twice the rated frequency that may degrade the control efficacy. This obstacle is addressed in this paper and a new scheme is presented. The approach includes three control loops for maximum power tracking, voltage control and frequency control. The generator field current is held constant at its nominal value avoiding the saturation in the field circuit. A robust fuzzy logic controller is adopted for the speed control loop of the diesel engine. The dynamic performance of the system is investigated under different operating conditions.

A local demand forecast by NN method for distributed autonomous voltage and reactive power control system

AbstractThe paper describes required technological innovation for voltage control of power systems under deregulation of power supply industries and presents a new concept of an autonomous control system for the voltage and reactive power of power systems. Installation of distributed generation connected to distribution networks will significantly increase the short circuit capacity of distribution lines. Therefore, GIS underground substations in the center of a large city are required to enable replacement of circuit breakers with ones of greater capability and to reform GIS bus configurations. Furthermore, a more detailed forecast of local demand and operation data of distributed generators are required for the stable control of voltage and reactive power. This paper presents methods of on‐line autonomous forecasting for short circuit capacity and demand of local transmission and distribution lines, which are indispensable for voltage and reactive control under deregulation of electric power supply industries. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 27–37, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20450

A pooled-neighbor swarm intelligence approach to optimal reactive power dispatch

This paper presents a pooled-neighbor swarm intelligence approach (PNSIA) to optimal reactive power dispatch and voltage control of power systems. The proposed approach uses more particles℉ information to control the mutation operation. The proposed PNSIA algorithm is also extended to handle mixed variables, such as transformer taps and reactive power source installation, using a simple scheme. PNSIA applied for optimal power system reactive power dispatch is evaluated on an IEEE 30-bus power system and a practical 118-bus power system in which the control of bus voltages, tap position of transformers and reactive power sources are involved to minimize the transmission loss of the power system. Simulation results showed that the proposed approach is superior to current methods for finding the optimal solution, in terms of both solution quality and algorithm robustness.