Voltage Control Problem Research Articles

Experimental Implementation of a Doubly Fed Induction Generator Used for Voltage Regulation at a Remote Location

This paper presents an implementation of a doubly fed induction generator (DFIG) for a variable speed wind energy conversion system for improving the voltage profile at remote locations. Normally, the wind power generation is at far ends from the load centers. Due to predominant nature of line inductance, the voltage drop is much affected by the reactive power. This voltage control problem is addressed by the coordinated control of both the voltage source converters (VSCs) of DFIG. Control algorithms for both the VSCs are presented in detail. The prototype of this proposed DFIG is developed in the laboratory using a digital signal processor. This developed DFIG prototype is controlled in both unity power factor and voltage regulation modes. This proposed DFIG is tested under both steady state and dynamic changes in wind speeds.

Eigenstructure Assignment for Componentwise Ultimate Bound Minimization in Discrete-Time Linear Systems

This technical note presents a feedback design approach to minimise state ultimate-bounds (UBs) in linear time-invariant discrete-time systems subject to non-vanishing bounded disturbances. A target closed-loop eigenstructure is first constructed to achieve the lowest possible UBs for one or more state components of the system. Structural conditions on the system matrices are then derived to guarantee that the target eigenstructure can be assigned by state feedback. When the required structural conditions are satisfied, an eigenvector assignment procedure can be applied to simultaneously minimise multiple UBs in systems with multiple inputs. The results are illustrated by a numerical example drawn from a distributed voltage control problem in inverter-based microgrids.

A quick method to solve the optimal coordinated voltage control problem based on reduction of system dimensions

This paper presents a new method to speed up the solving process of the optimal coordinated voltage control (OCVC) problem. To this end, after occurrence of a fault, the power system is initially partitioned into interior, boundary and exterior zones by spectral graph partitioning method. Partitioning is based on the fact that voltage instability just after the fault, is a local phenomenon, therefore the variation of boundary and exterior variables is smaller than that of interior ones. Then, the equations of boundary and exterior zones are linearized, the algebraic variables and equations of exterior zone are removed and a considerable decrease in the number of power system equations is obtained which is equal to a reduction in the system dimensions. As a result the determination process of the optimal control actions is fastened. Also, based on the monotonic behavior of long-term voltages, a new method of predicting voltage trajectory is proposed, in which two points are used: the first point referring to the system state just after applying the control actions, which is called jumping point and the final one referring to the steady state of the system. In a case study on the New England 39-bus power system, it was verified that using this method a remarkable increase in calculation speed can be obtained while retaining the system precision.

Coordinated Voltage Control in Distribution Network with the Presence of DGs and Variable Loads Using Pareto and Fuzzy Logic

This paper presents an efficient algorithm to solve the multi-objective (MO) voltage control problem in distribution networks. The proposed algorithm minimizes the following three objectives: voltage variation on pilot buses, reactive power production ratio deviation, and generator voltage deviation. This work leverages two optimization techniques: fuzzy logic to find the optimum value of the reactive power of the distributed generation (DG) and Pareto optimization to find the optimal value of the pilot bus voltage so that this produces lower losses under the constraints that the voltage remains within established limits. Variable loads and DGs are taken into account in this paper. The algorithm is tested on an IEEE 13-node test feeder and the results show the effectiveness of the proposed model.

A Trust Region SQP Method for Coordinated Voltage Control in Smart Distribution Grid

This paper investigates the coordinated voltage control problem for smart distribution grid with the integration of distributed generation (DG). By actively participating in voltage control together with under-load tap changer and shunt capacitors, DG can operate more effectively in the distribution network. The objective of the proposed control method is to minimize the active power loss in the distribution system and to decrease the number of switching device operations while maintaining the grid voltage within the allowable range. Nondispatchable and dispatchable DG are both considered in the control method. To solve the mixed integer nonlinear programming problem, the trust region sequential quadratic programming method is integrated with the branch and bound approach to iteratively approximate the optimization with trust region guidance. Numerical tests on a standard 10-kV distribution system, a real 10-kV distribution system in the Sichuan province of China, and the IEEE 13-bus demonstrate the applicability of the proposed coordinated voltage control method.

Calculation and simulation of transient optimal voltage output point in wireless sensor networks

For production of transient voltage output in wireless sensor network, due to the instability of the control voltage, the traditional control method needs to introduce the feedback control, through the establishment of mathematical model for periodic monitoring of the output voltage, change control strategy once the problem is found, lead to slow control time computation, cannot obtain the optimal output voltage values. A new method for calculating transient optimal voltage output points in sensor network of two-phase rotating and stationary coordinates is proposed. Through the analysis of the mathematical model of the network transient, the repetitive controller is designed on the two axes. By calculating the mean value of maximum and minimum value of the voltage, the transient energy-saving voltage output of the sensor network is monitored in real time. The control process of output voltage quality of sensor network with nonlinear load is analyzed, and the feed forward control method of parameter on line control is put forward. Under the premise to meet the control accuracy, enhance the response speed and stability of voltage output control of sensor networks. Simulation results showed that the method presented in this paper improves the poor effect of traditional methods, solves the complex problems of network energy-saving voltage control, and control effect of energy-saving voltage output is great, and the optimal voltage output values is obtained.

Decentralized voltage control of distributed generation using a distribution system structural MIMO model

The voltage control problem in Low Voltage (LV) distribution systems is becoming increasingly important due to the presence of Distributed Generation (DG). Recently, DG units have been proposed to contribute to voltage control according to a Volt/Var law which does not realize regulation. Moreover, since the existing LV systems are operated in a decentralized way without communication links, the simultaneous response of the controllers of the DG units may result into operational conflicts and instability. To overcome these problems, the present paper illustrates a design methodology for decentralized voltage controllers that act on DG reactive power injections. The controllers are suitable for the LV systems since they ensure voltage regulation and stability by using only local measurements and without information exchanges. The design is based on a proposed structural MIMO model of the distribution system. Robust stability is also analyzed: changes in the operating conditions of the distribution system are modeled as unstructured additive uncertainties affecting the MIMO model. A case study gives evidence of the applicability of the proposed design; the performance of the controllers in terms of both stability and regulation of the nodal voltages of three DG units connected to a LV distribution feeder is tested by numerical simulations; finally, a comparison with a Volt/Var technique is performed.

Fixed-order decentralized/distributed control of islanded inverter-interfaced microgrids

This paper focuses on the problem of voltage control of islanded inverter-interfaced microgrids consisting of several distributed generation (DG) units with radial structure. The main objectives are to (i) design a decentralized/distributed voltage controller with minimum information exchange between DG units and their local controllers (ii) design a fixed-/low-order dynamic output feedback controller which ensures stability as well as desired performance of the microgrid system in spite of load parameter uncertainties. To this end, the problem is formulated as an optimization problem which is the minimization of the cardinality of a pattern matrix subject to an H∞ performance constraint. Since the problem is intrinsically non-convex, a convex optimization-based design procedure for the controller synthesis is proposed in this paper. The effectiveness of the proposed controller is evaluated through simulation studies and Hardware-In-the-Loop (HIL) verifications. The simulation and experimental results demonstrate the effectiveness of the proposed control strategy.

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The voltage control problem in Low Voltage (LV) distribution systems is becoming increasingly important due to the presence of Distributed Generation (DG). Recently, DG units have been proposed to contribute to voltage control according to a Volt/Var law which does not realize regulation. Moreover, since the existing LV systems are operated in a decentralized way without communication links, the simultaneous response of the controllers of the DG units may result into operational conflicts and instability. To overcome these problems, the present paper illustrates a design methodology for decentralized voltage controllers that act on DG reactive power injections. The controllers are suitable for the LV systems since they ensure voltage regulation and stability by using only local measurements and without information exchanges. The design is based on a proposed structural MIMO model of the distribution system. Robust stability is also analyzed: changes in the operating conditions of the distribution system are modeled as unstructured additive uncertainties affecting the MIMO model. A case study gives evidence of the applicability of the proposed design; the performance of the controllers in terms of both stability and regulation of the nodal voltages of three DG units connected to a LV distribution feeder is tested by numerical simulations; finally, a comparison with a Volt/Var technique is performed.

Nonlinear Analysis of Interconnected Power Converters: A Case Study

In this paper the nonlinear dynamics of interconnected power converters in an islanded direct current (DC) microgrid is analyzed. By using a simplified scheme based on two cascaded converters we analyze the dynamical behavior that can arise from the interconnection of these devices on a common DC bus. Furthermore, in order to address the bus voltage control problem, we propose a Sliding Mode Controller for a DC-DC bidirectional power converter to control the DC bus voltage under instantaneous constant power loads. This class of loads introduces a destabilizing nonlinear effect on the converter through an inverse voltage term that can lead to significant oscillations in the DC bus voltage. Simulation results are shown to illustrate the nonlinear analysis.

Negative Selection of Artificial Immune Applied to Voltage Inadequacy Detection in Distribution Networks

Abstract The problem of voltage control and reactive power management plays a crucial role on power system’s operations. Particularly, detecting the most effective control actions to reduce the system loss and enhance the voltage profile is of major interest. This paper deals with system voltage inadequacy detection. To address this problem, artificial immune system is employed considering its negative selection mechanism. Its purpose is to monitor system operation data entry and check if the voltage level is within its operating values. In this sense, the user may define the range of control, so the proposed methodology may be useful for normal and emergency operating conditions. Corrective actions are undertaken if necessary. The IEEE 34 nodes distribution system is used to test the proposed methodology.

Integrated PLC-fuzzy PID Simulink implemented AVR system

Abstract Improving the transient response of power generation systems using automation control in a precise manner is the key issue. We design a fuzzy proportional integral derivative (PID) controller using Matlab and programmable logic controllers (PLCs) for a set point voltage control problem in the automatic voltage regulator (AVR) system. The controller objective is to maintain the terminal voltage all the time under any loads and operational conditions by attaining to the desired range via the regulation of the generator exciter voltage. The main voltage control system uses PLCs to implement the AVR action. The proposed fuzzy controller combines the genetic algorithm (GA), radial-basis function network (RBF-NN) identification and fuzzy logic control to determine the optimal PID controller parameters in AVR system. The RBF tuning for various operating conditions is further employed to develop the rule base of the Sugeno fuzzy system. The fuzzy PID controller (GNFPID) is further designed to transfer in PLCs (STEP 75.5) for implementing the AVR system with improved system response. An inherent interaction between two generator terminal voltage control and excitation current is revealed. The GNFPID controller configures the control signal based on interaction and there by reduces the voltage error and the oscillation in the terminal voltage control process. We achieve an excellent voltage control performance by testing the proposed fuzzy PID controller on a practical AVR system in synchronous generator for improve the transient response.

Priority Control Strategy of VSC-MTDC System for Integrating Wind Power

For the obvious advantages in integrating wind power, multiterminal HVDC transmission system (VSC-MTDC) is widely used. The priority control strategy is proposed in this paper considering the penetration rate of wind power for the AC grid. The strategy aims to solve the problems of power allocation and DC voltage control of the DC system. The main advantage of this strategy is that the demands for wind power of different areas can be satisfied and a power reference for the wind power trade can also be provided when wind farms transmit active power to several AC grids through the DC network. The objective is that power is well distributed according to the output power of wind farm with the demand of AC system and satisfactory control performance of DC voltage is obtained.

Secondary voltage control system based on fuzzy logic

This paper discusses the problem of secondary voltage control in power systems. This problem is of deep interest for researchers and engineers, since it imposes serious restrictions to system's operators. In general, this problem is resolved by selecting pilot buses representative of a region. Instead, in this paper, modal analysis is used to identify a coherent group of buses to be monitored. The set of information collected by modal analysis is considered by a fuzzy logic-based algorithm, so a voltage control policy is implemented. The academic IEEE 118-bus system is employed with all its limits considered, so the results may be reproduced.

The Study on Voltage Control Based on MAS and Grid Technology

In order to build a truly open OpenDSS and enhance the complexity of decision-making DSS for solving the problem of voltage control. a new model was given based on MAS in grid environment. Making use of the intelligence of MAS and adaptive capacity, based on the reasoning mechanisms for task decomposition and resource decision-making grid matching, a new intelligent algorithm based on MAS in order to improve its control effect, and the paper uses the kind of algorithm to coordinated secondary voltage control. The simulation results show the voltage control based on the algorithm have better global best properties and coordinate voltage effectively than routine method.

Reactive Power and Voltage Coordinated Control Research of Wind Farm Adopting Doubly-Fed Induction Generators

For the wind power grid voltage control problem, this paper proposed a reactive power and voltage control strategy by coordinate the wind farm reactive power source. Considering wind internal loss and the machine voltage deviation, established a optimal control model and a objective function, using the improved particle swarm optimization (PSO) algorithm to solve the function, the control strategy can reduce the wind internal loss and stabilize the voltage of the machine on the basis of meet the requirements of PCC voltage. The example simulation proved the effectiveness and economy of the control strategy.

Development of Automatic Voltage Regulator for Low‐Voltage Distribution Systems

SUMMARYThis paper presents the development of a new type of voltage regulator that can adequately maintain the voltage supplied to customers, dealing with the problem of voltage control that accompanies the widespread use of photovoltaic power generation systems. The newly developed device is a pole‐mounted voltage regulator consisting of a step‐down transformer that converts from high voltage to low voltage and a series transformer for voltage compensation. A demonstration test conducted at the CRIEPI Akagi Test Center confirmed that the voltage control function of the proposed voltage regulator is satisfactory, based on the proposed control algorithm. Simulation analysis, under the assumption of clustered installation of photovoltaic power generation systems, confirmed that the introduction of the proposed voltage regulator allows the system voltage to be adequately maintained and makes full photovoltaic power generation possible without suppressing the output. We anticipate that our proposed voltage regulator will be effective for adequately regulating the voltage in low‐voltage distribution systems and will effectively promote even more widespread photovoltaic power generation.

Multi-objective probabilistic reactive power and voltage control with wind site correlations

This paper proposes a multi-objective probabilistic reactive power and voltage control in distribution networks using wind turbines, hydro turbines, fuel cells, static compensators and load tap changing transforms. The objective functions are total electrical energy costs, the electrical energy losses, total emissions produced, and voltage deviations during the next day. Since the wind sources and load demand have intermittent characteristics, a probabilistic load flow based on 2m + 1 point estimated method is used to investigate the objective functions. The correlation in wind speed is considered as the distances between WTs are not large in distribution systems. Furthermore, a multi-objective modified bee swarm optimization is proposed to solve the optimization problem by defining a set of non-dominated points as the solutions. A fuzzy based clustering is used to control the size of the repository and a niching method is utilized to choose the best solution during the optimization process. Performance of the proposed algorithm is tested on a 69-bus distribution feeder. The results confirm the necessity of modeling the reactive power and voltage control problem in a stochastic framework. Also, the effects of wind site correlations on different objective functions are discussed completely.

Coordination Between OLTC and SVC for Voltage Regulation in Unbalanced Distribution System Distributed Generation

This paper presents a two-stage approach for solving the optimal voltage regulation problem in unbalanced radial distribution system in the presence of photovoltaic (PV) generation. The on-load tap changer (OLTC) and static VAr compensator (SVC) have been considered as the voltage control devices in this work. The formulated voltage control problem is a mixed-integer nonlinear programming problem which remains unsolved even after 8 h due to its computational burden. However, the proposed two-stage approach can solve this problem in less than 10 min. The feasibility of the proposed approach has been demonstrated on a modified IEEE 123-bus radial distribution system.

Research on Voltage Coordinated Control of the Power Plants Connected

According to coupling phenomenon of reactive power when a power plant is connected to another power plant, reactive power can not be to achieve a reasonable distribution of each power plant,which causes the problem of voltage control. This paper describes the methods of adjusting the parameters of automatic voltage control (AVC) to realize the coordinated control between power plants connected, which makes the voltage of power system to meet the demand of power grid operation.