Neutral Current Compensation Research Articles

Analysis of a Microgrid under Transient Conditions Using Voltage and Frequency Controller

This paper presents an investigation of voltage-and-frequency-(VF-) based battery energy storage system (BESS) controller used in micro grid for analyzing the optimum capability of plant. Microgrid is formed by using three hydropower plants feeding three-phase four-wire load. The proposed controller is used for load balancing, harmonic elimination, load leveling, and neutral current compensation. The proposed BESS controller permits the selection of an optimum voltage level of battery and allows independent current control of each phase. The main emphasis is given on maintaining constant voltage and frequency within the micro grid during transient conditions. Micro grid with power plant and its controller is modeled in MATLAB/Simulink using Power System Blockset (PSB) toolboxes.

Design and Implementation of Four-Leg Voltage-Source-Converter-Based VFC for Autonomous Wind Energy Conversion System

This paper deals with the design and implementation of a voltage and frequency controller (VFC) for a three-phase four-wire autonomous wind energy conversion system (WECS). The VFC is realized using a four-leg voltage source converter and a battery energy storage system. The enhanced phase-locked loop-based control algorithm is used in the VFC. A prototype of a 3.7-kW isolated asynchronous generator-based WECS is developed to demonstrate the performance of the VFC. The obtained test results have shown that the proposed VFC functions as a load leveler, a load balancer, a neutral current compensator, and a harmonic eliminator.

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.

Zig-zag transformer for neutral current compensation in an isolated wind energy system

This paper presents a voltage and frequency controller with neutral current compensation in a stand alone wind energy conversion system (WECS) employing an asynchronous generator. The proposed controller consists of a three leg insulated gate bipolar junction transistor (IGBT)-based voltage source converter and a battery energy storage system (BESS) at its DC bus. The neutral terminal for the consumer loads is created using a zigzag transformer with an additional secondary winding. This additional secondary winding of zigzag transformer facilitates to select the optimum voltage rating of the battery system at DC bus. The control algorithm of the controller is developed for bidirectional flow capability of the active power and reactive power control by which it controls the system voltage and frequency under different dynamic conditions such as varying consumer loads and varying wind speeds. The complete system is modelled and simulated in MATLAB using Simulink and PSB toolboxes. Extensive simulation results are presented to demonstrate the capability of the controller as a harmonic eliminator, a load balancer, a neutral current compensator along with voltage and frequency controller.

Performance of Voltage and Frequency Controller in Isolated Wind Power Generation for a Three-Phase Four-Wire System

This paper deals with a new control algorithm for a voltage and frequency controller (VFC) of an isolated wind energy conversion system (IWECS) using an isolated asynchronous generator to feed three-phase four-wire consumer loads. The reference source currents are estimated for the indirect current control of a voltage source converter (VSC) using the single-phase PQ theory to control the voltage and frequency of IWECS. A three-leg VSC with a battery energy storage system is used as a VFC for an IWECS. A nonisolated star-polygon transformer is used to provide a neutral terminal for four-wire loads and to compensate the neutral current resulting in reduction in rating of VSC. The proposed VFC is implemented using a DSP. Experimental results are presented to demonstrate the additional capabilities of VFC as a load leveler, a load balancer, a harmonic eliminator, and a neutral current compensator.

Neural-Network-Based Integrated Electronic Load Controller for Isolated Asynchronous Generators in Small Hydro Generation

This paper deals with a neural-network (NN)-based integrated electronic load controller (IELC) for an isolated asynchronous generator (IAG) driven by a constant-power small hydro uncontrolled turbine feeding three-phase four-wire loads. The proposed IELC utilizes an NN based on the least mean-square algorithm known as adaptive linear element to extract the fundamental component of load currents to control the voltage and the frequency of an IAG with load balancing in an integrated manner. The IELC is realized using zigzag/three single-phase transformers and a six-leg insulated-gate bipolar-transistor-based current-controlled voltage-source converter, a chopper switch, and an auxiliary load on its dc bus. The proposed IELC, with the generating system, is modeled and simulated in MATLAB environment using Simulink and Simpower System toolboxes. The simulated results are validated with test results on a developed prototype to demonstrate the effectiveness of IELC for the control of an IAG feeding three-phase four-wire linear/nonlinear balanced/unbalanced loads with neutral-current compensation.

A Sliding Mode Control for Four-Wire Shunt Active Filter

A Sliding Mode Control for Four-Wire Shunt Active Filter The present paper deals with the sliding mode control of a three-phase four-wire shunt active filter SAF, to improve phase-current waveform, neutral current mitigation and reactive power compensation in electric power distribution system. The sliding mode is formulated using elementary differential geometry, then the control vector is deduced from the sliding surface accessibility using the Lyapunov stability. The algorithm used to establish the current references for the sliding mode controller is based on the instantaneous real and imaginary power theory for four-wire system. It will be seen that this method permits to synthesis the control vector with simple manner, and finally, the obtained simulation results confirm that the above objectives are satisfied.

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.

New control approach for capacitor supported DSTATCOM in three-phase four wire distribution system under non-ideal supply voltage conditions based on synchronous reference frame theory

A large number of single-phase linear and non-linear loads may be supplied from three phase ac mains with neutral conductor. They cause excessive neutral current, harmonics and reactive power burden and unbalance. A four wire DSTATCOM (distribution static compensator) is used for neutral current compensation along with reactive power compensation, harmonics elimination and load balancing. A novel control approach is proposed for the control of four wire DSTATCOM under non-ideal supply voltage conditions. A four-leg voltage–source converter (VSC) with a dc capacitor is used as a four wire DSTATCOM. The proposed control approach is based on synchronous reference frame (SRF) theory and an indirect current control technique. The switching signals for the voltage–source converter (VSC) of the DSTATCOM are derived from the estimated reference supply currents. The load balancing, harmonics elimination and the neutral current compensation are demonstrated along with unity power factor (UPF) and zero voltage regulation (ZVR) modes of operation. Simulation results based on MATLAB software with its Simulink and power system blockset (PSB) toolboxes are presented to validate the control strategy. The DSTATCOM is able to maintain the self-supported dc bus under various disturbances.

Instantaneous Symmetrical Component Theory Based Voltage and Frequency Controller for Isolated Small Hydropower Generation

This article deals with the design and implementation of an instantaneous sequence component theory based integrated voltage and frequency controller for an isolated asynchronous generator, which is used in constant power small hydropower generation for feeding three-phase four-wire consumer loads. The proposed integrated voltage and frequency controller is used to control the voltage and frequency of an isolated asynchronous generator in the integrated manner. This integrated voltage and frequency controller is realized using a zigzag/star transformer and a three-leg insulated-gate bipolar transistor based current-controlled voltage source converter, a capacitor, a chopper switch, and an auxiliary load on its DC bus. The proposed integrated voltage and frequency controller with an isolated generating system is modeled and simulated in MATLAB along with Simulink and simpower system (SPS) toolboxes (The MathWorks, Natick, Massachusetts, USA). The simulated results are validated with test results of a developed prototype using a 3.7-kW, 230-V asynchronous generator to demonstrate its performance for feeding three-phase four-wire consumer loads with the neutral current compensation.

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.

Electronic load controller with power quality improvement of isolated induction generator for small hydro power generation

This study deals with an implementation of an instantaneous reactive power theory-based electronic load controller (ELC) for regulating the voltage and frequency of an isolated induction generator system (IG) that can supply electricity in remote areas. This ELC provides the fundamental reactive power and compensates harmonics of load currents. The proposed ELC is a combination of voltage source converter (VSC) with a dc link capacitor, a chopper and an auxiliary load at its dc bus. It controls active and reactive powers of the small hydro plant thus regulating the voltage and frequency of IG system. This ELC also balances the currents of the IG system under unbalanced load currents and eliminates the harmonics of the load currents thereby acting both as a load balancer and a harmonic eliminator. The zigzag/star transformer optimises the dc bus voltage of VSC and acts as a neutral current compensator. The proposed IG along with its ELC is implemented on a 3.7 kW IG system.

Performance Evaluation of Three Different Configurations of DSTATCOM with Nonlinear Loads

This paper deals with three different configurations of Distribution Static Synchronous Compensator (DSTATCOM) for distribution system. Detailed analysis, modeling, design and control are discussed for each configuration of DSTATCOM. MATLAB based models are developed for improving power factor/voltage regulation and neutral current compensation. Results show a marked reduction in total harmonic distortion (THD) of supply current levels when applied to nonlinear loads. Dynamics of systems are reported with sudden load addition or removal and performance of system is demonstrated in detail.

Decoupled Solid State Controller for Asynchronous Generator in Pico-hydro Power Generation

This paper deals with a decoupled solid state controller (DSSC) for an isolated asynchronous generator (IAG), used in constant power pico-hydro power generation for feeding three-phase four-wire loads. The proposed DSSC is used to control the voltage and frequency of the IAG in the decoupled manner. This DSSC is a combination of a voltage regulator (VR) for regulating the voltage and a conventional electronic load controller (ELC) for controlling the active power to regulate the frequency. The VR is realized using a zigzag/three-single-phase transformer and six-leg insulated gate bipolar transistors (IGBTs)-based current controlled voltage source converter (VSC) with a capacitor on its DC bus and an ELC is a combination of a three-phase diode bridge rectifier with a chopper switch and an auxiliary load. The proposed DSSC with an isolated generating system is modeled and simulated in MATLAB along with Simulink and power system blockset (PSB) toolboxes. The simulated results of the IAG-DSSC system are presented to demonstrate its performance for feeding three-phase four-wire linear/nonlinear (balanced/unbalanced) loads with the neutral current compensation.

Three-Phase 4-Wire Isolated Wind Energy Conversion System Employing VSC with a T-Connected Transformer for Neutral Current Compensation

This paper presents a voltage and frequency controller (VFC) for a 4-wire stand-alone wind energy conversion system (WECS) employing an asynchronous generator. The proposed VF con-troller consists of a three leg IGBT (Insulated Gate Bipolar Junction Transistor) based voltage source converter and a battery at its DC bus. The neutral terminal for the consumer loads is created using a T-connected transformer, which consists of only two single phase transformers. The control algorithm of the VF controller is developed for the bidirectional flow capability of the active power and reactive power control by which it controls the WECS voltage and frequency under different dynamic conditions, such as varying consumer loads and varying wind speeds. The WECS is modeled and simulated in MATLAB using Simulink and PSB toolboxes. Extensive results are presented to demonstrate the capability of the VF controller as a harmonic eliminator, a load balancer, a neutral current compensator as well as a voltage and frequency controller.

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.

Design and Control of Voltage Regulators for a Standalone Power Generation

This paper presents various configurations of voltage source converter (VSC) based voltage regulators (VRs) for a stand alone power generation employing an isolated asynchronous generator (IAG). A set of VRs are designed and their performance is simulated using Simulink and Power System Blockset (PSB) toolboxes to demonstrate their capabilities as a voltage regulator, a harmonic eliminator, a load balancer and a neutral current compensator. It also discusses their merits and demerits, to select a suitable topology of the voltage regulator according to IAG system requirements.

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.

VSC with zigzag transformer based electronic load controller for a stand-alone power generation

This paper presents a novel configuration of a voltage and frequency (VF) controller for a stand-alone pico hydro power generating system employing an asynchronous generator (IAG). The proposed VF controller is an electronic load controller (ELC), which consists of a three leg insulated gate bipolar junction transistor (IGBT) based voltage source converter (VSC), a DC chopper and an auxiliary load at its DC bus. The neutral terminal for the consumer loads is created using a zigzag transformer. Three leg VSC is connected to the tertiary winding of the zigzag transformer to select the optimum voltage rating of the DC bus. The control algorithm of the VF controller is developed to control the system VF under varying consumer loads. The proposed system is modelled and simulated in MATLAB using Simulink and power system blockset (PSB) toolboxes. Extensive simulation results are presented to demonstrate the capability of the controller as a harmonic eliminator, a load balancer, a neutral current compensator along with VF controller.

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.