Three-Phase Four-Wire Research Articles

Comparative Study between Different Controllers used in Three-phase Four-wire Shunt Active Filter

This paper presents a simulation of Three-Phase Four-Wire Shunt Active Filter destined to suppress harmonic currents generated by nonlinear loads in low voltage networks, and also to compensate reactive power. The identification method is based on P-Q theory using Self Tuning Filters; for-leg inverter commanded by hysteresis is used as generator of harmonic compensation currents. In order to have good performances of compensation, DC voltage of the inverter must remain constant (240V). In this paper we propose to use three different DC voltage controllers, PI, Backstepping and improved Backstepping controllers. The performances of these controllers are compared and discussed. Simulation results proved very good filtering performances with the three controllers either in transient or steady state. Improved backstepping controller gave the best results in transient state.

Detecting Method for Harmonic and Fundamental Negative Sequence and Zero Sequence Currents in Unbalanced Three-Phase Four-Wire Circuits

Shunt Active Power Filter (SAPF) is a new device for compensating harmonic currents in power system [1]. For unbalanced three-phase four-wire circuits, it need detect the total of harmonic and fundamental negative sequence and zero sequence currents at the same time. Base on traditional method of ip-iq, a detecting method which is suitable for unbalanced three-phase four-wire is proposed and analyzed by mathematical reasoning. At last, correctness of the result is verified by simulation.

Comparative study of reference currents and DC bus voltage control for Three-Phase Four-Wire Four-Leg SAPF to compensate harmonics and reactive power with 3D SVM

In this paper the performances of three reference currents and DC bus voltage control techniques for Three-Phase Four-Wire Four-Leg SAPF are compared for balanced and unbalanced load conditions. The main goals are to minimize the harmonics, reduce the magnitude of neutral current, eliminate the zero-sequence current components caused by single-phase nonlinear loads and compensate the reactive power, and on the other hand improve performances such as robustness, stabilization, trajectory pursuit, and reduce time response. The three techniques are analyzed mathematically and simulation results are compared. The techniques considered for comparative study are the PI Control, Sliding Mode Control and the Backstepping Control. Synchronous reference frame theory (SRF) in the dqo-axes is used to generate the reference currents, of the inverter.

Design and Implementation of Solar PV for Power Quality Enhancement in Three-Phase Four-Wire Distribution System

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. Three-Phase Four-Wire (3P4W) system is commonly used where single and three phase loads are connected to Point of Common Coupling (PCC). Due to unbalance loads, the 3P4W distribution system becomes unbalance and current flows in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral conductor. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor by which neutral and phase current harmonics are reduced significantly. In this paper, solar PV based inverter circuit is proposed for compensating neutral current harmonics. The simulation is carried out in MATLAB/SIMULINK and also an experimental setup is developed to verify the effectiveness of the proposed method.

Control for the Three-Phase Four-Wire Four-Leg APF Based on SVPWM and Average Current Method

A novel control method is proposed for the three-phase four-wire four-leg active power filter (APF) to realize the accurate and real-time compensation of harmonic of power system, which combines space vector pulse width modulation (SVPWM) with triangle modulation strategy. Firstly, the basic principle of the APF is briefly described. Then the harmonic and reactive currents are derived by the instantaneous reactive power theory. Finally simulation and experiment are built to verify the validity and effectiveness of the proposed method. The simulation results show that the response time for compensation is about 0.025 sec and the total harmonic distortion (THD) of the source current of phaseAis reduced from 33.38% before compensation to 3.05% with APF.

A New Approach Based on Instantaneous Power Theory for Improving the Performance of UPQC Under Unbalanced and Distortional Load Conditions

In order to deal with power quality problems under distortional and unbalanced load conditions, this paper presents a new control method for a four-wire three-phase unified power quality conditioner (UPQC) which is based on instantaneous power p-q theory. The proposed control approach is based on instantaneous power and is optimized by using a self-tuning filter (STF), without using any low-pass filters (LPFs) or phase locked loop (PLL), and without measuring load or filter currents. In this approach, the load and source voltages are used to generate the reference voltages of a series active power filter (APF) and source currents are used to generate the reference currents of a shunt APF. Therefore, the number of times that current is measured is reduced and system performance is improved. The performance of the proposed control approach is evaluated in terms of power factor correction, source neutral current mitigation, load balancing and mitigation of the current and voltage harmonics of distortional and unbalanced loads in a three-phase four-wire system. The results obtained by MATLAB/SIMULINK software show the effectiveness of the proposed control technique in comparison to the conventional p-q method.

Dynamic Model and Controller Design for Active Power Filter in Three-Phase Four-Wire System

This paper presents the dynamic model and control strategy of active power filter (APF) on dq0-frame in three-phase four-wire system. The structure of the APF is the three-leg split-capacitor. The dq0-frame with Fourier (DQF) method is used to calculate the reference currents on dq0-frame. The pulse width modulation (PWM) with PI controllers is considered in the paper. Moreover, the principle of the PI controller design for three current loops and two voltage loops are completely presented. The discrete design approach is used to design all controllers in the system. In addition, the hardware in the loop (HIL) technique is applied to simulate the harmonic elimination using the APF in the paper. The results show that the control strategy and the design approach presented in the paper can provide the good performance of the APF. Furthermore, the source currents after compensation can also follow the IEEE Std.519-1992 and IEEE Std.1459-2010.

Design and Performance of an Adaptive Low-DC-Voltage-Controlled LC-Hybrid Active Power Filter With a Neutral Inductor in Three-Phase Four-Wire Power Systems

This paper proposes an adaptive low-dc-link-voltage-controlled LC coupling hybrid active power filter ( LC-HAPF) with a neutral inductor, which can compensate both dynamic reactive power and current harmonics in three-phase four-wire distribution power systems. Due to its adaptive low-dc-link-voltage characteristic, it can obtain the least switching loss and switching noise and the best compensating performances, compared with the conventional fixed and newly adaptive dc-voltage-controlled LC-HAPFs. The design procedures of the dc-link voltage controller are discussed, so that the proportional and integral gains can be designed accordingly. Moreover, the general design procedures for the adaptive dc-voltage-controlled LC-HAPF with a neutral inductor are also given. The validity and effectiveness of the adaptive dc-link voltage-controlled LC -HAPF with a neutral inductor are confirmed by experimental results obtained from a 220-V 10-kVA laboratory prototype compared with the conventional fixed and adaptive dc-link voltage-controlled LC-HAPFs without a neutral inductor.

Improvement of Power Quality in Distribution System Using Fuzzy - Unit Vector Controller

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. The 3P4W (Three-Phase Four-Wire) system is commonly used in the distribution system, where single and three phase loads are connected to the PCC (Point of Common Coupling). Due to this loads, system become unbalance and current will flow in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral along with the fundamental component. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor. In this paper, a hybrid model control which consists of unit vector and fuzzy logic based controller is used to reduce the harmonic content in the neutral conductor. The simulation is carried out in MATLAB/SIMULINK to verify the effectiveness of the proposed method.

The Research of Novel High Voltage Electric Energy Measurement Apparatus Based on Three-Phase Four-Wire Virtual-Ground Theory

A novel apparatus is introduced in this paper used to measure high voltage electric energy based on three-phase four-wire virtual-ground theory. The virtual-ground design, Faraday shielding technique and Warner DC (Direct Current) self-supply method are integrated in this apparatus based on new I/V, V/V techniques to realize high accuracy, reliability and wide-linear range measuring. The effectiveness of the apparatus has been proved by in-house calibration and on-site test . The test result shows that it can be used in high voltage grid on-site calibration . Its measurement uncertainty can be limited to 0.1% under the condition of PF=1.0~0.8, and can reach 0.15% as PF=0.5. In summary, the apparatus discussed in this paper can be applied as high voltage electric energy measurement instrument to meet the requirement of online metrological verification and calibration. Furthermore, it is very useful for building the system of Advanced Metering Infrastructure (AMI) in smart grid.

Performance Analysis on Compensation of Three-Phase Four-wire Shunt

Performance Analysis on Compensation of Three-Phase Four-wire Shunt

Three-Phase Four-Wire Active Power Conditioners for Weak Grids

A micro-grid is a weak electrical grid, which can be easily subject to disturbances because it includes a variety of intermittent power sources, single-phase, three-phase and nonlinear loads, which can have a dynamic impact on power quality. The unbalance and the harmonic components in current and voltage waveforms are the most important among these. In this paper, the topologies and the control strategy of two Active Power Conditioners (APC) have been investigated in order to improve the operation of a micro-grid. The APC topologies presented in this paper act as an interface between renewable energy sources and the AC bus of a micro-grid. They also use an improved control strategy, which makes possible to inject energy in the micro-grid, compensate the current harmonics and correct the power factor. Moreover, the proposed control strategy allows the line current at the point of common coupling (PCC) to be balanced and sinusoidal even when the load is unbalanced. Consequently, the voltage at the PPC becomes balanced. The validity of the innovative control strategy has been proved in simulation using Matlab/Simulink environment.

Research on Control Strategy for Three-Phase Four-Wire LCL-Based Active Power Filter

Research on Control Strategy for Three-Phase Four-Wire LCL-Based Active Power Filter

A Novel Control Strategy for Three-Phase Four-Wire STATCOM

Nowadays Static Synchronous Compensator (STATCOM) has gradually become one of the representative techniques in the field of dynamic reactive power compensation in the power distribution system. This paper analyzed the topology and the voltage imbalance problem of the up and down capacitors on DC side of the three-phase four-wire STATCOM. In allusion to the imbalance problem of neutral point, a novel control strategy based on the control of zero-sequence current was proposed. By the triple close-loop control strategy, the STATCOM can achieve great control accuracy and dynamic performance. Simulation result proves that the proposed control method is effective.

Study of Shunt Active Power Filters Applied to Three-Phase Four-Wire Systems

Study of Shunt Active Power Filters Applied to Three-Phase Four-Wire Systems

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.

Component Minimized AC–DC–AC Single-Phase to Three-Phase Four-Wire Converters

This paper proposes two sets of topologies for single-phase to three-phase four-wire ac-dc-ac power conversion. All proposed configurations are characterized by reduction in the number of switches. The first set includes five configurations using ten power switches, while the second one includes six configurations using eight power switches. Such configurations are conceived for supplying three-phase four-wire loads and to guarantee bidirectional power flow between grid and load. Besides collecting different configurations, this paper proposes a synchronization technique, which can be applied for configurations with shared leg. The overall control strategy for providing dc link voltage control, grid current control, and PWM generation are presented. Simulated and experimental results are presented as well.

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.

Comprehensive Definitions for Evaluating Harmonic Distortion and Unbalanced Conditions in Three- and Four-Wire Three-Phase Systems Based on IEEE Standard 1459

So far, various studies are carried out in the field of unbalance decomposition from harmonic distortion in three-phase systems, and several criteria are proposed to express the value of these two types of disturbances, separately. However, most of them do not comply with the standard definitions for the effective values of three-phase voltage and current. Furthermore, extensive investigations are not performed for the calculation of the decomposition factors in three- and four-wire three-phase systems. In this paper, sequence matrices are applied to phase and line voltage and current harmonics to calculate balanced and unbalanced components. Afterwards, according to IEEE Standard 1459-2010, new distinguishing factors are extracted for three- and four-wire installations. Also, a new index is introduced as total harmonic and unbalance distortion to have an overall consideration of the system disturbance. Finally, three illustrative examples are presented to show the ability of the proposed indices in evaluating unbalance and harmonic distortion in three-phase systems.

Four-wire three-phase load balancing with Static VAr Compensators

Static VAr Compensators (SVCs) can balance the phase currents of three-wire three-phase loads and compensate their reactive power. Thus, the SVC-load set becomes a balanced load with any desired power factor. This paper proposes a method to use SVCs with four-wire three-phase loads which still perform those functions: load balancing and reactive power compensation. As a result, any load connected to a three-(or-four-)wire three-phase system can be transformed into a balanced load with unity power factor, even if it is a single-phase load. Other properties that appear in particular cases are also analyzed.