Shunt Capacitor Banks Research Articles

Novel Loss-Voltage Sensitivity Factor for Capacitor Placement in Radial Distribution System Using Analytical Approach

An analytical technique is proposed for allocation of shunt capacitor bank in radial distribution system. The objective is formulated to determine the size, number and location of capacitor bank for real and reactive power loss reduction, voltage profile enhancement and annual cost saving. A novel Loss-Voltage Sensitivity Factor (LVSF), has been incorporated in the technique. The value of LVSF decides the candidate bus location. The achievability of the proposed method (PM) has been demonstrated on IEEE-69 bus test system allowing comparing results with latest optimization techniques in literature. Further application of PM on 130 bus relatively large distribution system shows the effectiveness and robustness of the proposed technique. Capacitors allocated (size and location) during light loading condition simulation are forced as fixed capacitors in nominal and heavy loading simulations. This development is essential when allocated capacitors in nominal and heavy loading simulations do not include nodes of fixed capacitors.

Switching Control for Capacitor Banks in Distribution System

Objectives: A shunt capacitor bank with appropriate switching control using relay and circuit breakers is proposed to compensate reactive power in an 11kV Malaysian test distribution system with high density commercial load. Methods: Fuseless Capacitor Bank will be modelled according to IEEE standard using MATLAB. The designed switching control for the fuseless capacitor bank will perform condition checking based on the criteria of power factor and determine the best control action to be taken in order to compensate reactive power in the power system effectively. The designed system is then tested on an 11kV Malaysian test distribution system with high density commercial load. Findings: Simulation results clearly indicate that the designed system is able to react and compensate reactive power adequately in accordance to Malaysia’s utility regulations. Improvements: For future improvements, criteria focused on both voltage and power factor can be implemented to minimize power loss in the system.

Particle swarm optimization application on a micro grid for energy savings

This paper presents the effectiveness of the particle swarm optimization (PSO) to minimize the total active power loss of an island scale micro grid distribution network. In the adopted method, the co-simulation of the PSO algorithm and the Mat-power software on an island scale electrical network was proposed. The power system in Kiribati is selected as the study case. Two diesel power generation stations, one voltage regulator unit and one switching shunt capacitor bank are used to regulate the system voltage. The 24-h load flow is executed with the proposed PSO algorithm to minimize the active power loss and the annual power loss savings can be estimated. It is concluded that the proposed PSO algorithm can work well and give a satisfactory result.

Improve Distribution System Energy Efficiency With Coordinated Reactive Power Control

In the distribution management system (DMS), an essential application for the energy efficiency improvement is loss reduction. Loss reduction often involves the control of reactive power (var) resources to optimize the var flow in the network. Traditionally, most available var resources in the distribution network have been switchable shunt capacitor banks. Today distributed energy resources (DER) are becoming another significant var resource due to their increasing penetration, which brings new opportunities as well as challenges for loss reduction. This paper proposes an advanced loss reduction approach to achieve the optimal control coordination among multiple capacitors and DERs. The proposed approach and solution are developed on the basis of the detailed multi-phase distribution network modeling and the state-of-the-art optimization technology. This work also investigates the impact of the DER var control on the loss reduction improvement and voltage violation correction. The effectiveness of the proposed approach is demonstrated on practical utility distribution circuits with varying degree of unbalance and model complexity. The performance of the solution method proves the capability of online solution speed for large and complex distribution systems.

The Application of a 6% Reactor in High-Voltage Capacitor Bank Switching

The switching of capacitor banks at high voltage for power-factor improvement and voltage support can generate significant transients. Such switching transients are produced by inrush currents and transient overvoltages in systems to which the capacitor bank is connected. These switching transients can cause damage to insulation and mal-operation of protective relays. This paper presents the simulation and investigation of a switching large-shunt capacitor bank in a 230kV Thailand substation system. A computer simulation using PSCAD/EMTDC was performed to determine the peak of the transient currents, the oscillation overvoltage and the frequency of the inrush current. The transient inrush current is generated by energizing of the 4×72 MVAr, 230 kV shunt capacitor banks. Methods of inrush current transient analysis and reduction were evaluated. Limiting the transients with a 6% reactor in series was simulated. The simulations indicate that the 6% reactor can significantly reduce the magnitude of the transients.

Coordinated Voltage Control With Online Energy Margin Constraints

Based on data available from phase measurement units (PMUs), this paper proposes an energy margin constrained online coordinated voltage control (CVC) algorithm. First, the energy function model is established, which is based on detailed device models that include the effects of shunt capacitor banks, reactive power output of generators and under-load-tap-changers (ULTCs). In order to improve the computational efficiency, a Lie derivative-based method is used to map the energy change into the system trajectory along the energy manifold. Then, the change of energy margin based on the Lie derivative is used as the objective function and the reactive power margin is used as a constraint to formulate a linear programming problem. A coordinated strategy is proposed to help achieve the optimal solution when the linear programming problem is solved. In comparison with the other control modes, the proposed method improves the stability margin and the control effectiveness of voltage profile. Numerical results are provided for a three-machine system, the IEEE-30 bus system and the New England-39 bus benchmark system.

Smart grid adaptive energy conservation and optimization engine utilizing Particle Swarm Optimization and Fuzzification

This paper aims to present a novel smart grid adaptive energy conservation and optimization engine for smart distribution networks. The optimization engine presented in this paper tries to minimize distribution network loss, improve voltage profile of the system and minimize the operating cost of reactive power injection by switchable shunt Capacitor Banks using Advanced Metering Infrastructure data. Moreover, it performs Conservation Voltage Reduction (CVR) and minimizes transformer loss. To accurately weight the optimization engine objective function sub-parts, Fuzzification technique is employed in this paper. Particle Swarm Optimization (PSO) is applied as Volt-VAR Optimization (VVO) algorithm. Substantial benefits of the proposed energy conservation and optimization engine include but not limited to: adequate accuracy and speed, comprehensive objective function, capability of using AMI data as inputs, and ability to determine weighting factors according to the cost of each objective sub-part. To precisely test the applicability of proposed engine, 33-node distribution feeder is used as case study. The result analysis shows that the proposed approach could lead distribution grids to achieve higher levels of optimization and efficiency compared with conventional techniques.

An ant colony system based control of shunt capacitor banks for bulk electricity consumers

The present work focuses on the formulation of an optimization algorithm based on Ant Colony Search (ACS) technique operational from a Blackfin DSP microcontroller platform. This intelligent algorithm enables switching of appropriate Shunt Capacitor Banks (SCBs) in installations of bulk consumers of electricity to improve their power factor. The application is mainly targeted on cold storages, rolling mills, traction substation and steel plants in India, where SCBs are installed over a long period in an unplanned manner. Unawareness of the impact of energy savings coupled with the fiscal incapability of these users make them unable to install costly power electronic devices for p.f. control ACS based embedded controller is sensitive to unpredictable load changes and selective capacitors switching cause optimal VAR control with minimum stress to the system. Employing the distributed computational model based on ACS becomes an ideal tool for the combinatorial optimization problem to select a best combination within a bank of varying sizes and varying status signifying dynamically changing search space. This low cost device will reduce the penalty billing of consumers by improving the p.f. and improved metered reading. The use of this device will lead to permeation of technology to the strata which needs it most making energy management possible without any human intervention.

A new efficient BBO based method for simultaneous placement of inverter-based DG units and capacitors considering harmonic limits

In recent years, nonlinear load and inverter-based distributed generation (like photovoltaic and fuel cells) have been increasing rapidly. This type of DGs can amplify and propagate the harmonic level of network. Shunt capacitor banks and DG units allocation without considering harmonic limits will increase harmonic pollution. In this paper the biogeography-based optimization (BBO) algorithm is applied in simultaneous optimal sitting and sizing of inverter-based DGs and capacitor banks regarding multi-level and nonlinear loads. The objective of problem are reduction of active and reactive power loss, reduction of purchased energy from transmission line and improvement of voltage profile considering equal and unequal constrains. Also, effect of total harmonic distortion (THD) constraint according to IEEE 519 standard has been investigated in the objective function which is one of the main advantages of the proposed method. The proposed method is tested on IEEE 33 bus and IEEE 69 bus radial distribution systems (RDS). Comparing BBO method results with particle swarm optimization (PSO) and genetic algorithm (GA) results will indicate the high capability of the proposed method in simultaneously optimal sitting and sizing of DGs and capacitors.

Field Experiments on 10 kV Switching Shunt Capacitor Banks Using Ordinary and Phase-Controlled Vacuum Circuit Breakers

During the switching on/off of shunt capacitor banks in substations, vacuum circuit breakers (VCBs) are required to switch off or to switch on the capacitive current. Therefore, the VCBs have to be operated under a harsh condition to ensure the reliability of the equipment. This study presents a complete comparison study of ordinary and phase-controlled VCBs on switching 10 kV shunt capacitor banks. An analytical analysis for switching 10 kV shunt capacitor banks is presented on the basis of a reduced circuit with an ungrounded neutral. A phase selection strategy for VCBs to switch 10 kV shunt capacitor banks is proposed. Switching on current waveforms and switching off overvoltage waveforms with, and without, phase selection were measured and discussed by field experiments in a 110 kV substation in Chongqing, China. Results show that the operation of phase-controlled VCBs for 10 kV switching shunt capacitor banks is stable, and phase-controlled VCBs can be used to implement the 10 kV switching on/off shunt capacitor banks to limit the transient overvoltage and overcurrent. The values of overvoltage and inrush current using phase-controlled VCBs are all below those with ordinary VCBs.

Hierarchical Two-Level Voltage Controller for Large Power Systems

This paper proposes a two-level voltage controller for large-scale power systems. The aim of the controller is to maintain a near-optimal voltage profile in the transmission network by coordinating discrete reactive power (var) control devices in the system. The controller is targeted for implementation in electric power transmission utility companies where most of the voltage controls are coordinated by switching of discrete var devices such as shunt capacitor and reactor banks and transformer banks load tap changers (LTCs). By effectively dividing the controller responsibilities between local substation controls and a central coordinator at control center level, the design is aimed at voltage control of large-scale power systems. At local level, the substation controllers maintain their respective substation bus voltages by local power-flow-like computations using mostly local PMU measurements. The central coordinator computes and provides the voltage set-points to the substation controllers and also coordinates by enabling or disabling the local controllers as needed. The controller is being designed towards prototype implementation in Southern California Edison (SCE), starting with local controllers at specific substations in the first stage. It is tested on real-time dynamic models and large-scale power-flow simulations of SCE transmission network.

ANALYSIS AND CONTROL OF INRUSH CURRENT FOR A 33KV DISTRIBUTION SYSTEM

Capacitor bank switching involves not only handling capacitive currents, but also the remnant/stored energies of capacitor banks, cables and overhead lines. The interruption of a capacitive current induces dielectric problems for the switching device as well as the connected power system. The high inrush currents can cause damage to the capacitive elements of the capacitors bank and may weld the contacts of the switch together. A computer model that represents a 33kV distribution system is simulated using PSCAD software for purpose of this study and evaluates the switching currents associated with the switching of shunt capacitor banks. Various methods (use of series reactor, synchronous closing and parallel-break switching) for controlling the inrush currents are studied and a comparative analysis is made. The paper highlights and suggests use of auxiliary breaks as a reliable passive mode of control.

Transient recovery voltage analysis for various current breaking mathematical models: shunt reactor and capacitor bank de-energization study

Abstract Electric arc is a complex phenomenon occurring during the current interruption process in the power system. Therefore performing digital simulations is often necessary to analyse transient conditions in power system during switching operations. This paper deals with the electric arc modelling and its implementation in simulation software for transient analyses during switching conditions in power system. Cassie, Cassie-Mayr as well as Schwarz-Avdonin equations describing the behaviour of the electric arc during the current interruption process have been implemented in EMTP-ATP simulation software and presented in this paper. The models developed have been used for transient simulations to analyse impact of the particular model and its parameters on Transient Recovery Voltage in different switching scenarios: during shunt reactor switching-off as well as during capacitor bank current switching-off. The selected simulation cases represent typical practical scenarios for inductive and capacitive currents breaking, respectively.

Analysis and Mitigation of Resonance Propagation in Grid-Connected and Islanding Microgrids

The application of underground cables and shunt capacitor banks may introduce power distribution system resonances. In this paper, the impacts of voltage-controlled and current-controlled distributed generation (DG) units to microgrid resonance propagation are compared. It can be seen that a conventional voltage-controlled DG unit with an LC filter has a short-circuit feature at the selected harmonic frequencies, while a current-controlled DG unit presents an open-circuit characteristic. Due to different behaviors at harmonic frequencies, specific harmonic mitigation methods shall be developed for current-controlled and voltage-controlled DG units, respectively. This paper also focuses on developing a voltage-controlled DG unit-based active harmonic damping method for grid-connected and islanding microgrid systems. An improved virtual impedance control method with a virtual damping resistor and a nonlinear virtual capacitor is proposed. The nonlinear virtual capacitor is used to compensate the harmonic voltage drop on the grid-side inductor of a DG unit LCL filter. The virtual resistor is mainly responsible for microgrid resonance damping. The effectiveness of the proposed damping method is examined using both a single DG unit and multiple parallel DG units.

A robust FACTS PV-smart grid interface scheme for efficient energy utilisation

In the last two decades, wind and PV system have been increased remarkably. A novel FACTS-based PV-DC-AC interface scheme using VSI-6 pulse scheme with a switched filter compensator (SFC) scheme developed by the first author is validated for efficient energy utilisation and decoupled DC-AC interface with robust stand under normal and faults (open and short circuit) conditions. The proposed FACTS scheme enhances power quality and ensures efficient energy utilisation and stabilised interface to the smart grid. The FACTS scheme is based on a hybrid power filter-capacitive compensation scheme with SPWM-dual switching strategy using a dual series and shunt capacitor banks. The hybrid control scheme uses a modified fast acting dynamic error driven time-descaled/decoupled multi-regulation loops with an additional inter-coupled weighted controller. The proposed FACTS-scheme is tested using the MATLAB-Simulink Simulation Environment. The unified AC study system was tested under different operating/fault conditions including normal loading and open/short circuit fault conditions.

Optimal Allocation of Distributed Generation and Shunt Capacitors for the Reduction of Total Voltage Deviation and Total Line Loss in Radial Distribution Systems Using Binary Collective Animal Behavior Optimization Algorithm

This article presents a novel binary collective animal behavior algorithm to solve the problem of optimal allotment of distributed generation sets and shunt capacitors in radial distribution systems. Simultaneous sizing and placement of distributed generation units and shunt capacitors in distribution systems is a very complex optimization task, because it is a problem of combinatorial analysis with mixed-integer and binary variables and hard restrictions. With the objective of optimal allotment of shunt capacitor banks and distributed generations, a binary collective animal behavior algorithm optimizes the total line loss, or the total voltage deviation separately in a distribution system, by optimally and simultaneously allocating capacitor banks and distributed generations of optimal ratings, considering the topology of a radial distribution network. The binary collective animal behavior algorithm is applied on various balanced IEEE radial distribution networks. The results are compared to those of a conventional binary particle swarm optimization algorithm to establish the optimization superiority of binary collective animal behavior algorithm.

Optimal multi objective placement and sizing of multiple DGs and shunt capacitor banks simultaneously considering load uncertainty via MOPSO approach

This study proposes a new application of multi objective particle swarm optimization (MOPSO) with the aim of determining optimal location and size of distributed generations (DGs) and shunt capacitor banks (SCBs) simultaneously with considering load uncertainty in distribution systems. The multi objective optimization includes three objective functions: decreasing active power losses, improving voltage stability for buses and balancing current in system sections. The uncertainty of loads is modeled by using fuzzy data theory. This method uses Pareto optimal solutions to solve the problem with objective functions and constraints. In addition, a fuzzy-based mechanism is employed to extract the best compromised solution among three different objective functions. The proposed method is implemented on IEEE 33 bus radial distribution system (RDS) and an actual realistic 94 bus Portuguese RDS and the results are compared with methods of Strength Pareto Evolutionary Algorithm (SPEA), Non-dominated Sorting Genetic Algorithm (NSGA), Multi-Objective Differential Evolution (MODE) and combination of Imperialist Competitive Algorithm and Genetic Algorithm (ICA/GA). Test results demonstrate that the proposed method is more effective and has higher capability in finding optimum solutions in cases where DG and SCB are located and sized simultaneously in a multi objective optimization.

Stability Study of Grid Connected to Multiple Speed Wind Farms with and without FACTS Integration

Integration of wind power into power grid has developed several problems like lack of reactive power at point of common coupling which leads to voltage stability problems for the utility owner. Due to the weakness of shunt capacitor banks in maintaining voltage stability as well as reactive power improvement at point of common coupling and wind turbine generator bus, STATCOM and SVC as dynamic var compensators have been attached at the transmission network to support the stability of the proposed system. In this paper, three wind farms of different wind speed connected to grid with and without flexible AC transmission systems have been proposed. Simulations are carried out using Matlab/Simulink to investigate the performance of the proposed system under normal and abnormal conditions. 

Voltage Control of Static Var Compensator for a Remote System Interconnected by Long‐Distance AC Cables

SUMMARYThe voltage variation in a remote system is large when the system is connected by long‐distance AC cables due to the cable capacitance. In Japan, the longest 54‐km 66‐kV AC submarine cable interconnection between the Kyushu mainland and Goto Islands was commissioned in 2005. It was requested to mitigate the voltage variation caused by switching off and on one circuit of the two circuits in the AC cables when a fault occurs. Since the conventional voltage control methods such as transformer tap changer or shunt capacitor and reactor banks are not sufficient because of their slow response time, a static var compensator (SVC) was installed on the Goto Islands. In such an application, an SVC control method should be developed so as not to override the existing voltage control systems. This paper describes the SVC control method developed for the Goto Islands AC interconnection project, which can be applied to similar situations. The effectiveness of the control method was verified by the results of effective value simulation and of field testing, which was implemented before the SVC was commissioned in 2007. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 19–30, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22337

Optimum shunt capacitor placement in distribution system—A review and comparative study

Shunt capacitors are commonly used in distribution system for reactive power compensation. Different analytical, numerical programming, heuristic and artificial intelligent based techniques have been proposed in the literature for optimum shunt capacitor bank (SCB) placement. This paper will present a very detailed overview of optimum SCB placement techniques. Six different approaches of optimum SCB placement based on minimization of power losses, weakest voltage bus approach and maximization of system loadability will be applied on four different radial distribution test systems. The results will be compared on the basis of power loss reduction, voltage profile improvement, system loadability maximization and the line limit constraint.