Reactive Compensation Devices Research Articles

Multitime Scale Reactive Power and Voltage Optimal Regulation for Transmission Network With Wind Power Cluster Based on Model Predictive Control

In order to solve the problem of voltage fluctuation caused by the grid integration of wind power cluster, a multitime scale reactive power and voltage optimal regulation method based on model predictive control (MPC) is proposed in this paper. In the day‐ahead stage, the reduction of network active power loss is mainly achieved through the regulation of discrete reactive power compensation devices and generator units, focusing on the economic operation of the power system. In the intraday stage, considering the rapid response characteristics of continuous reactive power compensation devices, the optimal regulation aiming to minimize voltage control deviation is carried out under 15‐ and 5‐min time scale based on the MPC algorithm with the adjustment of continuous reactive power compensation devices. In the feedback correction stage, a fast calculation method considering reactive power partitioning is adopted instead of solving the 5‐min optimization model for 288 periods, avoiding excessive adjustment of reactive compensation devices. While effectively improving voltage fluctuations caused by wind power prediction deviation, it also alleviated the computational and communication burden on the system. Finally, the effectiveness of the proposed regulation method in this paper is verified with the improved IEEE‐39 test case.

Volt-Var Control for Utility-Scale Solar PV Plants to Downsize SVCs and Curtailment Effects

One way to increase solar photovoltaic penetration in the grid is the management of voltage fluctuations. This is because a photovoltaic plant cannot be interconnected to the grid if it causes voltage violations. Voltage violation is where voltage exceeds the acceptable range. Often, grid operators request photovoltaic plant owners to regulate voltage sufficiently with expensive and space-consuming static Var compensators. Unfortunately, this sometimes makes the project less feasible. This paper argues that there are better ways to regulate voltage. It also asserts that these ways must be sought before blindly procuring a static Var compensator or seeking battery storage. We simulated with a 70-MW photovoltaic plant as an addition to the grid. Without voltage regulation, voltage violations in Spring were found to be particularly significant. However, the proposed reactive power compensation removed all voltage violations smartly. Furthermore, the study results demonstrated that the operator-induced curtailment effectively reduced the necessary amount of reactive power compensation, leading to a smaller size of SVC, as it occurred specifically at certain overvoltage points. This paper argues that the economic and spatial efficiency of reactive power compensation devices is key to increasing photovoltaic penetration. It argues that one-sided bearing of the cost of reactive compensation devices is inefficient.

Optimal location and dimensioning of capacitors in microgrids using a multicriteria decision algorithm

This work presents a methodology for optimal compensation of reactive power in Electric Microgrids using a multicriteria decision algorithm based on heuristic methods. It was verified the optimal location and dimensioning of fixed capacitor banks in a microgrid with 14 buses with objective functions based on cost, efficiency and quality criteria in a maximum demand operating condition and also considering the constraints of objective variables in minimum demand scenarios. The proposed capacitance to be installed was considered as a discrete variable. The location of discretized reactive capacitances was simulated at candidate nodes analyzing the power flow in the case study, resulting in a wide solution space that was tackled by means of multicriteria optimization, using dominance elimination techniques and the weighted sum method for decision making. The variables analyzed were: cost, maximum and average deviations of the voltage profile, power factor, total losses in the lines of the system and THD. All these variables were also verified in minimum demand scenarios. The proposed solution provides significant improvements in the variables analyzed and verifies the optimal performance of the technique. The mathematical analysis demonstrates the need of addressing the reactive compensation problem by means of multicriteria decision and the proposal provides a very novel tool for calculating the location and dimensioning of reactive compensation devices in distribution systems and microgrids. The programming was done in the Matlab environment with simulations using Simulink. The case study analyzed is a very novel validated Microgrid system of which it is known the variables that take part of this analysis, as an approximation of the study of a very real Microgrid.

Optimal Location and Dimensioning of Capacitors in Microgrids Using a Multicriteria Decision Algorithm

This work presents a methodology for optimal compensation of reactive power in Electric Microgrids using a multicriteria decision algorithm based on heuristic methods. It was verified the optimal location and dimensioning of fixed capacitor banks in a microgrid with 14 buses with objective functions based on cost, efficiency and quality criteria in a maximum demand operating condition and also considering the constraints of objective variables in minimum demand scenarios. The proposed capacitance to be installed was considered as a discrete variable. The location of discretized reactive capacitances was simulated at candidate nodes analyzing the power flow in the case study, resulting in a wide solution space that was tackled by means of multicriteria optimization, using dominance elimination techniques and the weighted sum method for decision making. The variables analyzed were: cost, maximum and average deviations of the voltage profile, power factor, total losses in the lines of the system and THD. All these variables were also verified in minimum demand scenarios. The proposed solution provides significant improvements in the variables analyzed and verifies the optimal performance of the technique. The mathematical analysis demonstrates the need of addressing the reactive compensation problem by means of multicriteria decision and the proposal provides a very novel tool for calculating the location and dimensioning of reactive compensation devices in distribution systems and microgrids. The programming was done in the Matlab environment with simulations using Simulink. The case study analyzed is a very novel validated Microgrid system of which it is known the variables that take part of this analysis, as an approximation of the study of a very real Microgrid.

Using Hysteresis Band Method for the Control of Three-Phase STATCOM Connected to a Transport Network

The transit of reactive power through the electric transport lines due to the inductive loads, creates problems of instabilities on the electrical networks. Transport networks are increasingly vulnerable to instability of voltage due to industrialization and/or population growth. The managers of these networks are therefore seeking effective solutions to these problems. STATCOM is one of the devices of the family of shunt FACTS used for reactive energy compensation. It generally offers better features compared other FACTS devices and conventional reactive compensation devices. This work aims to apply the STATCOM controlled by the current control method by hysteresis bands for the maintenance of the voltage in an electric transport network. The transport network is modeled as a transport line in MATLAB/SIMULINK and its characteristics are compared to the system without STATCOM.

Using Hysteresis Band Method for the Control of Three-Phase STATCOM Connected to a Transport Network

The transit of reactive power through the electric transport lines due to the inductive loads, creates problems of instabilities on the electrical networks. Transport networks are increasingly vulnerable to instability of voltage due to industrialization and/or population growth. The managers of these networks are therefore seeking effective solutions to these problems. STATCOM is one of the devices of the family of shunt FACTS used for reactive energy compensation. It generally offers better features compared other FACTS devices and conventional reactive compensation devices. This work aims to apply the STATCOM controlled by the current control method by hysteresis bands for the maintenance of the voltage in an electric transport network. The transport network is modeled as a transport line in MATLAB/SIMULINK and its characteristics are compared to the system without STATCOM.

Study of a low voltage reactive power dynamic compensation device with continuously adjustable capacity

A dynamic reactive power compensation device with continuously adjustable capacity is designed for low voltage power grid. According to the time requirement of reactive power dynamic compensation for capacitor switching, a signal generating circuit of voltage/current zero-crossing triggering switching is designed. A capacitor combination method to improve the compensation accuracy and the control strategy to change the compensation power of capacitor by adjusting voltage are put forward. The hardware structure of compensation device, reactive power compensation control mode, capacitor switching control method and capacitor output power regulation method are designed. Using Matlab/Simulink, the simulation results show that the proposed method can realize continuous reactive power adjustment according to the set power factor.

A novel AC filter system for the line commutated converter high voltage DC transmission system

This paper proposes a novel AC filter system for a line commutated converter high voltage DC (LCC-HVDC) transmission system. Through the coordination of the hybrid active power filters (APF) and the existing reactive compensation devices, the proposed filter system can not only enhance the suppression performance for LCC-HVDC harmonics, but also optimize the AC yard layout with reduced reactive power subbanks, reducing the cost of HVDC projects. The novel filter system adopts a serial passive resonance topology obtained by careful comparison of different APFs. A proper control scheme is then designed integrating the control strategy of the APF and impedance characteristics of the HVDC system, which is able to realize harmonic suppression and dynamic reactive power support simultaneously. In addition, a novel self-adaption digital low-pass filter algorithm is presented, which is used in the APF harmonic detecting step, enhancing both high precision and fast dynamic response. On the basis of a real HVDC project, the advantages of proposed filter system in harmonic suppression, reactive power regulation, and sub-banks reduction are simulated and demonstrated.

Efficiency study of the reactive shunt compensation device in power lines

We consider the devices for reactive shunt compensation and simulated their use in a real energy facility.

Research on Emergency Control Strategy of Synchronous Condenser for Inhibiting HVDC Commutation Failure

As multi-infeed HVDC systems are integrated into power grid, the operation characteristics of power grid have changed significantly. The problems of the shortage of dynamic reactive power reserve and voltage support need the allocation of dynamic reactive compensation device such as synchronous condenser urgently. This paper researches the influence of installing synchronous condenser on system performance in multi-infeed HVDC power grid. Based on the analysis of the defects of synchronous condenser on HVDC commutation failure under existing conventional control mode, this paper presents the emergency control strategy and system architecture with synchronous condenser. In the end, the effectiveness of the proposed control strategy is verified based on the actual grid simulation.

Multi-Objective Coordinated Control of Reactive Compensation Devices Among Multiple Substations

The multi-objective reactive power coordination control model was presented in this paper to overcome the drawback that reactive power compensation devices lack in coordination and have high active power loss. In this model, the minimum bus voltage deviation and total power loss of reactive power compensation devices are taken as objective functions, by bringing the lower voltage reactors and capacitors into the static var compensator control system and considering the reactive power compensation devices interaction between different transformer substations. Due to the different sensitivity of control variables in control model and lack of the local search ability, control variables are divided into sensitive variables and non-sensitive variables. Then, the improved non-dominated sorting genetic algorithm II (NSGA-II) with secondary search ability is used to search the Pareto optimal solution set. Two substations in large power grid with strong voltage coupling are coordinated in different load level. The results obtained by proposed NSGA-II algorithm can provide a variety of optimal control strategies. Compared to the conventional NSGA-II algorithm and normal boundary intersection method, the improved NSGA-II algorithm has better convergence curve and distribution of the Pareto solution sets.

Multiobjective Dynamic VAR Planning Strategy With Different Shunt Compensation Technologies

High concentrations of induction motor loads can impose stress on transmission and distribution systems, leading to voltage instability in some situations. Properly sized and coordinated reactive power sources will provide for improved operation. We present a strategy for finding an optimal mix (type, size, and location) of dynamic shunt reactive compensation devices. The planning strategy is subject to satisfying steady-state, dynamic and transient performance criteria such as fault-induced delayed voltage recovery limits, as well as criteria related to single ( N –1) contingency and load disturbance events. Shunt reactive power compensation devices considered include mechanically switched capacitor banks, static reactive power compensators and static synchronous compensators. The proposed strategy employs a large number of multitimescale time-domain simulations suitable for use with high performance computing clusters and a genetic algorithm to solve the mixed-integer nonlinear programming formulation using parallel computation capabilities. The method is applied to a New England IEEE 39-bus system with assumed high penetration of induction motors. A comprehensive study shows that performance enhancement and significant cost reduction can be achieved using an optimum combination of various shunt compensator technologies.

Using a new modified harmony search algorithm to solve multi-objective reactive power dispatch in deterministic and stochastic models

The optimal reactive power dispatch (ORPD) problem is a very important aspect in power system planning, and it is a highly non-linear, non-convex optimization problem because it consists of both the continuous and discrete control variables. Since a power system has an inherent uncertainty, this paper presents both the deterministic and stochastic models for the ORPD problem in multi-objective and single-objective formulations, respectively. The deterministic model considers three main issues in the ORPD problem including the real power loss, voltage deviation, and voltage stability index. However, in the stochastic model, the uncertainties in the demand and equivalent availability of shunt reactive power compensators have been investigated. To solve them, we proposed a new modified harmony search algorithm (HSA), implemented in single and multi-objective forms. Since, like many other general purpose optimization methods, the original HSA often traps into the local optima, an efficient local search method called chaotic local search (CLS) and a global search operator are proposed in the internal architecture of the original HSA algorithm to improve its ability in finding the best solution because the ORPD problem is very complex, with different types of continuous and discrete constrains, i.e. excitation settings of generators, sizes of fixed capacitors, tap positions of tap changing transformers, and amount of reactive compensation devices. Moreover, the fuzzy decision-making method is employed to select the best solution from the set of Pareto solutions. The proposed model is individually examined and applied on different test systems. The simulation results show that the proposed algorithm is suitable and effective for the reactive power dispatch problem compared to the other available algorithms.

Power Systems and Railway Power Systems: So Similar, So Different [About This Issue

Railway power systems represent a special type of power system. They can include power plants, transmission and distribution grids-with their electrical lines, transformers, reactive compensation devices, and other parts-and electrical loads- with all their components, such as motors, resistors, and electronic devices. Their design and operation must ensure that the consumers (i.e., mostly the trains but also the infrastructure-stations, signaling systems, and heating systems) receive the energy with the specified characteristics (i.e., voltage, frequency, and waveform).

A novel index for identification of weak nodes for reactive compensation to improve voltage stability

In this study, a new reactive power loss index (RPLI) is proposed for identification of weak buses in the system. This index is further used for determining the optimal locations for placement of reactive compensation devices in the power system for additional voltage support. The new index is computed from the reactive power support and loss allocation algorithm using Y-bus method for the system under intact condition and as well as critical/severe network contingencies cases. Fuzzy logic approach is used to select the important and critical/severe line contingencies from the contingency list. The inherent characteristics of the reactive power in system operation is properly addressed while determining the reactive power loss allocation to load buses. The proposed index is tested on sample 10-bus equivalent system and 72-bus practical equivalent system of Indian southern region power grid. The validation of the weak buses identification from the proposed index with that from other existing methods in the literature is carried out to demonstrate the effectiveness of the proposed index. Simulation results show that the identification of weak buses in the system from the new RPLI is completely non-iterative, thus requires minimal computational efforts as compared with other existing methods in the literature.

Research and Analysis of Reliability of Power Grid SVG Master Circuit in Rural Areas

Problems such as low voltage and big line loss have long existing in the power grid in rural areas of China. In recent years, some province and cities have improved voltage and reduced line loss by installing SVG at substations in rural power grids, and the effect is remarkable.With great compensation capacity and a good variety of modes of compensation, SVG is sure to replace old reactive compensation devices in rural power grid in future, which requires evaluation and analysis of SVG reliability so as to guarantee safety and stability of the power grid. However, now no research or analysis has been made in China on SVG reliability in rural power grids, which affects wide promotion of SVG in rural power grids.Under the background of Liaoning Power Grid 10kV/±5Mvar Chain SVG, this paper analyzes the reliability of k/n (G) system model of SVG master circuit structure, improving the accuracy of system reliability estimation. The estimation matches the operation outcome, thus providing data basis for the feasibility of SVG’s wide application in rural power grid in future.

Impact of Connecting Reactor on Stable Operation of Chain SVG Device

Chain SVG device is connected to the power grid via the reactor which is also referred to as connection reactor. Compared with other reactors of reactive compensation devices, It’s not like the serial filtering reactor which simply provides a specific quantity of inductive reactive power, or parallel phase control reactor which provides continuously adjustable inductive reactive power. The connection reactor in SVG is related to the impact of SVG on the power grid, the impact of the power grid system on SVG, and in particular, the compensation capacity and effect of SVG. Therefore, during design, requirements of SVG and electrical property of the compensated system should both be considered. In this paper, the impact of the connection reactor on SVG stable operation is analyzed in detail. The design principle that when choosing the reactor parameters, the impact on power unit DC side voltage should be prioritized is proposed, and simulation verification is conducted by using of PSCAD software. A reasonable reactor is selected for a 10kV SVG based on the conclusion. The actual operation result verifies the rationality of design.

Selecting Optimal Reactive Compensation Device for Power System

Although there are many studies on application of FACTS unit, especially application of reactive power generating unit for power system to enhance voltage stability amplitude and transient stability as considered, the evaluation and selection of suitable power generating unit (STATCOM or SVC) as well as optimal compensation size in the analysis of steady and transient state is not paid attention to. This article studies the above described issues to give a solution to install reasonable reactive power generating source (kind of Var source, location, size) for the power system. The analysis will be based on the technical factors rather than economic ones. 500kV grid system in Vietnam will be used in the calculation until 2015. To deeply evaluate, the implementation plan of reactive power compensation was only studied for 500kV grid in the South, where the load demand is large and can be dramatically increased. The results of power flow calculation, the analysis of characteristics of PV, OPF, and transient stability were studied through PSS/E-30 software.

Study on Reactive Power Compensation of Single Wind Farm

With the proportion of wind turbine generation system(WTGS) in power grid is highly increasing, which produces a great effect on the security and stability of the electric power network. Considering the current condition and characteristic of wind form, we built a simulation model in the imitative situation with different wind turbine outputs and different feeder types, obtained the reactive power loss of wind farm and key node voltage, as well as the ability of fixed compensation device. By using the reactive power generated from wind turbine, it can reduce capacity of the reactive compensation device in collection station, which realizes the balance of reactive power, increases the voltage stability.

The Application of S7-200 PLC Reactive Compensation Device in Small Substation

In the present rural power grid reconstruction project ,according to the problems of capacitor reactive power compensation in rural small substation. Take a small substation for instance, according to its operation and control method, set the criterion of the capacitor bank switching. A new high reliability, flexible reactive power compensation control device based on s7-200 PLC is designed. It plays an important role in improving the power supply , guaranteeing the quality of voltage, reducing the loss of rural power gid.