Three-phase Four-wire Distribution Static Compensator Research Articles

DSTATCOM using model predictive control associated with LMS control

ABSTRACT In this paper, a type of variable step size LMS named weighted zero attracting variable step size (WZAVSSLMS) is equipped with the control algorithm for governing DSTATCOM. In WZAVSSLMS, the ability of zero attracting nature to a variable step size (VSSLMS) for improving convergence rate is observed. WZAVSSLMS algorithm-based fundamental extractor is developed to identify the fundamental quantity of the load current for a three-phase four-wire DSTATCOM with non-linear load in this work. This type of variable step size LMS has provided a concession for quick convergence rate and steady-state error. Precision and convergence of responses are accomplished by the learning rate control. As a result of these features over conventional LMS, the authors choose WZAVSSLMS based approach in well-known DSTATCOM system to compensate power quality issues. The fundamental extraction from the distorted load current constitutes the main divergences in the proposed study. Further, the Finite control set model predictive control (FCS MPC) of the distribution static compensator (DSTATCOM) using Weighted Aggregated Sum Product Assessment Solution (WASPAS) method is implemented.

A Nonlinear Controller for Neutral Point Piloted (T-Type) Multilevel Inverter-Based Three-Phase Four-Wire DSTATCOM

In recent times, neutral point piloted (NPP) or half-leg T-type multilevel inverter (MLI) becomes a promising topology for medium-voltage high-power applications. This T-type MLI is the best substitute for diode clamped multilevel inverter (DCMLI) due to its simple structure and absence of clamping diodes. However, the neutral point voltage control or dc bus capacitors' balance of NPP T-type MLI is a challenging task. Therefore, this paper presents a nonlinear sliding mode controller (SMC) for dc-link voltage balance and reference current control in distribution static compensator (DSTATCOM). For this, a three-level T-type MLI-based three-phase four-wire DSTATCOM is considered to eliminate current-related power quality issues such as harmonics, reactive power, load unbalance, and neutral current. The proposed NPP T-type-based DSTATCOM is compared with DCMLI and active DCMLI-based DSTATCOMs in terms of switching losses and cost. Simulation studies are carried out in MATLAB Simulink environment and further corroborated with experimental studies. Furthermore, the ability of the proposed SMC-based controller is compared with the PI controller under different operating conditions.

Intelligent Controlled DSTATCOM for Power Quality Enhancement

In this study, a three-phase four-wire distribution static compensator (DSTATCOM) is proposed to improve power quality, including the compensation of the three-phase unbalanced grid currents, the total harmonic distortion (THD) reduction of the grid current, and the power factor (PF) correction. Moreover, when different types of loads vary in the power system, the instantaneous power follows into or out of the DC-link capacitor in the DSTATCOM and results in poor transient responses of the grid current and DC-link voltage and performance deterioration. Hence, the DC-link voltage control plays a significant part in the DSTATCOM under load variation. For the purpose of mending the transient responses of the grid currents and DC-link voltage control and the performance of the DSTATCOM, the conventional proportional-integral (PI) controller is substituted with a novel online trained wavelet Takagi-Sugeno-Kang fuzzy neural network (WTSKFNN) controller in this study. Furthermore, the network structure and the online learning method of the proposed WTSKFNN controller are described in detail. Finally, the experimental results are given to certify the feasibility and effectiveness of the DSTATCOM using the proposed WTSKFNN controller for the power quality enhancement and the DC-link control improvement under load variation.

Experimental Validation of ADALINE Least Mean Square Algorithm in a Three-Phase Four-Wire DSTATCOM to Enhance Power Quality

The requirement of a robust and adaptive control algorithm in active filters is inevitable nowadays. In this paper, an ADAptive LINEar neuron (ADALINE) based Least Mean Square (LMS) control algorithm is proposed for a three-phase-four-wire (3P4W) distribution power system under unbalanced loading conditions. The proposed controller has a unique inbuilt characteristic to extract the fundamental active positive sequence component from an unbalanced load current. Particularly, the control algorithm is intended to calculate an adaptive and suitable amplitude for the three-phase reference source currents which are used for the switching pulse generation in the subsequent steps. Moreover, the Distribution STATic COMpensator (DSTATCOM) is performed to eliminate harmonic contents of supply current and harmful excessive neutral current in the system. Further, the DC-link voltage is regulated in order to reduce the power loss across the DSTATCOM, and to attain a balanced, high-quality power availability at the Point of Common Coupling (PCC). The proposed system is accomplished in the MATLAB2014a/Simulink, and a low power rated 3P4W DSTATCOM prototype incorporating with the dSPACE1104 real-time environment to verify the proposed control algorithm.

Power Quality Enhancement Using Euclidean Direction Search Based Control Technique

This paper proposes the design and control of a three-phase four-wire distribution static compensator (DSTATCOM) for elimination of several power quality (PQ) issues, namely harmonics, reactive power, load unbalancing, and neutral current. A three-phase voltage source converter (VSC) and a zigzag transformer based configuration are utilized as a DSTATCOM. The zigzag transformer is operated to provide a suitable path for load neutral current and other PQ problems are mitigated by designing a suitable control for VSC. The control of VSC is developed using Euclidean direction search (EDS) technique based adaptive control theory. This control algorithm is designed to extricate fundamental constituents from the load current and used to generate switching pulses for VSC. The improved behavior of the proposed EDS-based control is observed by comparing it with other existing controllers. Real-time performance of the EDS control is verified on a developed prototype in the laboratory using VSC and DSP (dSPACE1104 R&D controller).

Hyperbolic tangent function‐based least mean‐square control algorithm for distribution static compensator

A variable learning rate least mean-square (LMS) based on hyperbolic tangent function is used to enhance the rate of convergence and to suppress the existing noise in the system for the control of distribution static compensator (DSTATCOM) consisting of a three-leg voltage source converter (VSC) with a zig-zag transformer to eliminate the significant neutral current caused by non-linear unbalanced loads in a three-phase four-wire supply system. Simulation is made for the proposed control algorithm in three-phase four-wire DSTATCOM system and its performance is compared with the conventional Adaline-based LMS control algorithm. It is also shown that the convergence rate of the proposed control algorithm is quite faster in comparison with the conventional control algorithm. A prototype of DSTATCOM is developed and the real-time implementation of the proposed control algorithm is performed on a digital signal processor. Test results have demonstrated the satisfactory performance of DSTATCOM with the proposed control algorithm under linear and non-linear loads.

Comparison of Three leg and Four Leg VSC DSTATCOM for Power Quality Assessment

A new three-phase four-wire DSTATCOM (distribution static compensator) based on three-leg VSC (voltage source converter) and a star/delta transformer is proposed for power quality improvement. The star/delta transformer connection mitigates the neutral current and the 3-leg VSC compensates harmonic current, reactive power and balances the load. Three single phase transformers are connected as star/delta transformer for interfacing to a three phase four-wire power distribution system and the required rating of the VSC is reduced. However, a 4-leg VSC (voltage source converter) based DSTATCOM (Distribution Static Compensator) is used for the load compensation and neutral current compensation in 3-phase 4-wire distribution system. For extracting the reference source currents, Instantaneous Symmetrical Component Theory (ISCT) based control algorithm is modified for voltage regulation and used with indirect current control technique for controlling the DSTATCOM currents. The DSTATCOM is controlled for power factor correction and voltage regulation at PCC (point of common coupling). Simulations are performed for various load conditions such as a reactive linear load, an unbalanced load and a non-linear load in Power Factor Correction (PFC) mode and in Zero Voltage Regulation (ZVR) mode in MATLAB environment using SIMULINK and Sim Power System (SPS) toolbox.

Photovoltaic based distribution static compensator for power quality improvement

This paper deals with a model of photovoltaic (PV) array or battery operated DC/DC boost converter fed three-leg VSC (Voltage Source converter) with star delta transformer for power quality improvement. A synchronous reference frame theory is proposed for three-phase four-wire DSTATCOM (Distribution Static Compensator) which includes voltage source converter and a dc link capacitor. The proposed DSTATCOM provides reactive power compensation, source harmonic reduction and neutral current compensation at the point of common coupling (PCC). The PV array or battery operated boost converter is used to step up the voltage to match the DC link requirement of the three-leg VSC. The main advantage of this proposed approach is that, it will provide continuous compensation for the whole day. The star/delta transformer provides isolation to the VSC and path to the zero sequence fundamental as well as harmonics neutral current. To derive the reference current in order to generate the firing pulse to the VSC, the overall system is designed, developed and validated by using MATLAB–SIMULINK environment.

Implementation of Neural-Network-Controlled Three-Leg VSC and a Transformer as Three-Phase Four-Wire DSTATCOM

In this paper, a neural-network (NN)-controlled distribution static compensator (DSTATCOM) using a dSPACE processor is implemented for power quality improvement in a three-phase four-wire distribution system. A three-leg voltage-source-converter (VSC)-based DSTATCOM with a zig-zag transformer is used for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonic currents, and neutral current compensation at the point of common coupling. The Adaline (adaptive linear element)-based NN is used to implement the control scheme of the VSC. This technique gives similar performance as that of other control techniques, but it is simple to implement and has a fast response and gives nearly zero phase shift. The zig-zag transformer is used for providing a path to the zero-sequence current in a three-phase four-wire distribution system. This reduces the complexity and also the cost of the DSTATCOM system. The performance of the proposed DSTATCOM system is validated through simulations using MATLAB software with its Simulink and Power System Blockset toolboxes and hardware implementation.

Digital Signal Processor Implementation of Isolated Reduced-rating Voltage Source Converter Using a Zig-zag Transformer for Three-phase Four-wire Distribution Static Compensator

The proposed distribution static compensator is used to compensate the reactive power for power factor correction or voltage regulation along with load balancing, neutral current compensation, and harmonics current elimination. A zig-zag/star transformer is used to isolate the voltage source converter, and it is operated as a three-phase four-wire distribution static compensator for power quality improvement in a three-phase four-wire system. In order to reduce the current rating of the voltage source converter, the zig-zag configuration is used in the primary windings of the transformer. The voltage source converter is connected to the secondary windings of the zig-zag/star transformer, and this allows the optimum selection of voltage rating of the voltage source converter. Moreover, this transformer connection provides isolation for the voltage source converter system. The distribution static compensator is implemented using the dSPACE DS1104 R&D controller (dSPACE Inc., Wixom, Michigan, USA) and a slave digital signal processor subsystem based on the TMS320F240 digital signal processor (dSPACE Inc., Wixom, Michigan, USA) to validate the design and the developed control algorithm.

Three-Leg Voltage Source Converter Integrated with T-connected Transformer as Three-phase Four-wire Distribution Static Compensator for Power Quality Improvement

In this article, a new topology of a distribution static compensator is proposed for power quality improvement in a three-phase four-wire distribution system. A three-leg voltage source converter based distribution static compensator is integrated with a T-connected transformer for the compensation of reactive power for voltage regulation or for power factor correction, along with load balancing, elimination of harmonics currents, and neutral current compensation at the point of common coupling. The T-connected transformer is used for providing a path to the zero-sequence current in a three-phase four-wire distribution system. In order to reduce the voltage rating of the voltage source converter, the T-connected transformer is designed to have secondary windings for integrating the distribution static compensator. This transformer connection provides the selection of an “off-the-shelf” voltage source converter for this application, and it also provides isolation for the voltage source converter system. The kVA rating of the transformers in the T-connected configuration is comparable to that of a similar zig-zag transformer, and there are only two single-phase transformers required in the T-connected configuration. This reduces the complexity and also cost of the distribution static compensator system. The performance of the proposed distribution static compensator system is validated through simulations using MATLAB software with its Simulink and Power System Blockset toolboxes.

Star-hexagon transformer and non-isolated three-leg VSC based three-phase four-wire DSTATCOM

A new three-phase four-wire DSTATCOM (distribution static compensator) is proposed for power quality improvement in the distribution system. The DSTATCOM is based on a star/hexagon transformer and three-leg VSC (voltage source converter). It compensates harmonic current, reactive power and balances the load along with neutral current compensation. Each of the three single phase transformers has three windings and the secondary windings are connected in star/hexagon configuration for interfacing to a three-phase four-wire power distribution system. The IGBT (insulated gate bipolar transistor) based VSC is a capacitor supported and it is controlled for the required compensation of load currents. The DC bus voltage of the VSC is regulated even during dynamic load variations. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination and load balancing under linear loads as well as non-linear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and SimPower System (SPS) tool boxes.

Star/Hexagon Transformer Based Three-Phase Four-Wire DSTATCOM for Power Quality Improvement

A new topology of DSTATCOM (distribution static compensator) is proposed for power quality improvement in three-phase four-wire distribution systems. A three-leg VSC (Voltage Source Converter) is integrated with a star/hexagon transformer for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonics currents and neutral current compensation. The star/hexagon connected transformer provides a path to the zero sequence current in a three-phase four-wire distribution system. In order to optimize the voltage rating of the VSC, the star/hexagon transformer is designed to have a suitable voltage rating for the secondary windings for integrating the three-leg VSC. This transformer connection provides the selection of 'off the shelf' VSC for this application and it also provides isolation for the VSC system. The performance of the proposed DSTATCOM system is validated through simulations using MATLAB software with its Simulink and Power System Block set (PSB) toolboxes.

A T-Connected Transformer and Three-leg VSC Based DSTATCOM for Power Quality Improvement

In this paper, a new three-phase four-wire distribution static compensator (DSTATCOM) based on a T-connected transformer and a three-leg voltage source converter (VSC) is proposed for power quality improvement. The T-connected transformer connection mitigates the neutral current and the three-leg VSC compensates harmonic current, reactive power, and balances the load. Two single-phase transformers are connected in T-configuration for interfacing to a three-phase four-wire power distribution system and the required rating of the VSC is reduced. The insulated gate bipolar transistor (IGBT) based VSC is supported by a capacitor and is controlled for the required compensation of the load current. The DC bus voltage of the VSC is regulated during varying load conditions. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination, and balancing of linear loads as well as nonlinear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and power system blockset toolboxes.