Three-phase Four-wire Shunt Active Filter Research Articles

Three-Phase Four-Wire Shunt Active Power Filter Based on the Hybrid Automaton Control with Instantaneous Reactive Power Theory

The present paper proposes a new controller design method based on the hybrid automaton approach with instantaneous reactive power theory for three-phase four-wire shunt active power filter (SAPF) which employs a three-leg split capacitor voltage source inverter (VSI) in presence on nonlinear loads. In this study, the control objectives are twofold:(i) compensation for undesired harmonic and reactive currents caused by the non-linearity of electronic power loads, i.e. power factor correction (PFC) and (ii) regulation of the voltage of the DC link capacitor. To meet the above objectives, the problem of controlling is dealt with by designing a new Two-loop cascaded controller. The inner loop is constructed using a hybrid automaton representation of three-phase four-wire SAPF with instantaneous reactive power theory in order to ensure a unity power factor. The outer loop is constructed using a proportional-integral (PI) regulator, that assures a tight regulation of the DC bus voltage to a desired value. The numerical simulation within the MATLAB/SimPowerSystems environment confirms the theoretical results and shows the effectiveness of the hybrid automaton controller.

Improving Power Quality by a Four-Wire Shunt Active Power Filter: A Case Study

This paper presents the use of a three-phase four-wire shunt active power filter to improve the power quality in the Department of Industrial Electronics of a large enterprise from Romania. The specificity is given by the predominant existence of single-phase consumers (such as personal computers, printers, lighting and AC equipment). In order to identify the power quality indicators and ways to improve them, an A-class analyzer was used to record the electrical quantities and energy parameters in the point of common coupling (PCC) with the nonlinear loads for 27 h. The analysis shows that, in order to improve the power quality in PCC, three goals must be achieved: the compensation of the distortion power, the compensation of the reactive power and the compensation of the load unbalance. By using the conceived three-leg shunt active power filter, controlled through the indirect current control method in an original variant, the power quality at the supply side is very much improved. In the proposed control algorithm, the prescribed active current is obtained as a sum of the loss current provided by the DC voltage and the equivalent active current of the unbalanced load. The performance associated with each objective of the compensation is presented and analyzed. The results show that all the power quality indicators meet the specific standards and regulations and prove the validity of the proposed solution.

Performance Analysis of ANN Based three-phase four-wire Shunt Active Power Filter for Harmonic Mitigation under Distorted Supply Voltage Conditions

This paper presents the design and implementation of three-phase four-wire shunt active power filter (SAPF). It consists of insulated gate bipolar transistors, IGBT based current-controlled voltage source inverter (CC-VSI), series coupling inductor and self-supported DC bus. Power electronics based converters and non-linear loads generate waveform-driven power quality issue as harmonics. Three-phase four-wire SAPF mitigates harmonics, compensates for reactive power, neutral current and power factor correction. Conventionally, the positive sequence detection control strategy using phase-locked loop (PLL) is applied as the synchronizing unit vector element to generate reference source currents. Conventional controller tuning process is difficult and fails to perform satisfactorily under supply voltage variation conditions. In this paper, Levenberg-Marquardt back propagation training algorithm based artificial neural network (ANN) controller is proposed to regulate DC link voltage due to its self-adapting and rapid calculation characteristics that allow the controller to handle high nonlinearity and uncertainty in a non-linear system. Weights of a neuron are adapted to minimize total harmonic distortion (THD) of source current under the step, ramp, time series amplitude variation and frequency and amplitude of modulation conditions. The proposed system is modelled in MATLAB/SIMULINK environment and laboratory prototype with dSpace1104 control card is developed. Experimentation results validate the simulated results of the proposed scheme under supply voltage variations for three-phase four-wire distribution system.

PLL-Less Three-Phase Four-Wire SAPF with STF-dq0 Technique for Harmonics Mitigation under Distorted Supply Voltage and Unbalanced Load Conditions

This paper presents a non-iterative technique that generates reference current to manage operation of a three-phase four-wire shunt active power filter which employs a three-leg split capacitor voltage source inverter (VSI) topology. The proposed technique integrates together a self-tuning-filter (STF) and direct-quadrature-zero (dq0) principle (referred here as STF-dq0), allowing the controlled shunt active power filter (SAPF) to perform effectively under distorted source voltages and unbalanced load conditions. Unlike the previous technique developed based on the standard dq0 principle, the proposed technique does not require any service from a phase-locked loop (PLL) where two STFs are applied to separate harmonic and fundamental elements for the purpose of generating synchronization phases and reference current, respectively. Simulation work which includes connection of the SAPF circuits, design of control techniques and all the necessary assessments are conducted in MATLAB-Simulink platform. Performance achieved by the SAPF while utilizing the proposed technique is thoroughly investigated and benchmarked with that demonstrated by the SAPF while using the standard dq0 technique, to evaluate the inherent advantages. Exhaustive simulation results are provided and thoroughly discussed to support design concept, effectiveness, and benefits of the proposed technique.

A Three-Phase Grid-Connected PV System Based on SAPF for Power Quality Improvement

This paper proposes a combined system of three-phase four-wire shunt active power filter (SAPF), and photovoltaic generator (PVG), to solve the power quality problems such as harmonic currents, poor power factor, and unbalanced load. In addition, the proposed system can inject the issued energy from the PVG into the utility grid. To increase the efficiency of the PVG and extract the maximum photovoltaic (PV) power under variable atmospheric conditions, a maximum power point tracking (MPPT) technique based on perturb and observe (P&O) is implemented in the DC/DC boost converter. The effectiveness of the proposed PVG-SAPF (PVG and SAPF) based on the use of synchronous reference frame theory (SRF theory) under unbalanced nonlinear load. The proposed PVG-SAPF is validated through numerical simulations using Matlab/Simulink software. The simulation results show the effectiveness of the proposed PVG-SAPF.

Three-phase four-wire shunt active power filter working simultaneously as energy conditioner

PurposeThe purpose of this study is to find a control method for three-phase four-wire shunt active power filters, which uses a load-equivalent conductance for obtaining a reference signal for compensating non-active current.Design/methodology/approachChanges of energy stored in an active filter’s reactance elements are monitored to find the active component of the load current. It is then used as a current reference to be realised as a supply source current. Computer simulation methods were used to verify the presented control method.FindingsTo calculate the reference signal for the active filter action, it is enough to measure the active filter’s DC-side capacitors’ voltages. It has been proved that P regulators are sufficient to realise compensating current and to stabilise active filter capacitors’ voltages. The supply source-neutral conductor current can be zeroed even for nonlinear and unbalanced load-generating DC-component in its neutral conductor. In addition, the active filter can buffer load-active power changes and act simultaneously as a local energy accumulator.Originality/valueThis paper provides an alternative approach to address the problem of the three-phase four-wire shunt active power filter control methods.

Three-phase four-wire shunt active filter under unbalanced loads with backstepping and PI controllers

This paper proposes backstepping technique for the direct-current bus voltage control in three-phase four-wire shunt active filter. The identification of reference currents is made by synchronous referential frame theory with self-tuning filter. The three-phase four-wire shunt active filter is implemented with DSPACE 1104 system to compensate harmonics generated by unbalanced system of non-linear loads. Four-leg topology is used for the inverter of shunt active filter and the switching patterns of the inverter are generated by analogue hysteresis card. The experimental results verify the good performance of the proposed shunt active filter in term of harmonic currents reduction and improvement of power quality. A comparison between backstepping controller and the conventional proportional-integral controller is illustrated, in steady state, the two controllers fixe direct-current bus voltage at its reference value, however, a clear advantage of the backstepping control in dynamic state can be observed.

Modeling, Simulation and Control Design of a PWM Three-Phase Four-Wire Shunt Active Power Filter for a 60 kW Industrial Load

Electric Power Quality remains a major concern for energy suppliers and consumers. One of the major reasons that contribute to the worsening of power quality is the existence of current harmonics in the power network caused by nonlinear electric loads. A common solution to eliminate such harmonics is the application of Active Power Filters (APF). In this paper, experimental measurements of the current were conducted on a power line that belongs to Electricité du Liban (EDL); feeding a three-phase large industrial load. Two control schemes for a shunt three-phase four-wire APF are developed: one is based on the use of hysteresis current controller to compensate the current distortion and the reactive power, the other consists of multiple loops PI controllers that ensure voltage regulation at the DC side of the filter and current wave shaping at the AC side. The latter control scheme is based on a small–signal averaged model of the converter, computed in the (dq0) synchronous frame. The simulations are performed using Matlab/Simulink tools. Results show an important reduction of the Total Harmonic Distortion (THD) and significant improvement of the power factor for both methods. Also, a comparison between the obtained results shows that the second control scheme is better than the first one on the level of harmonics reduction.

DC-Link Voltage Balance Control in Three-phase Four-wire Active Power Filters

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.

Operation of PV System With dc–dc Boost-Fed Shunt Active Filter to Mitigate Current Harmonics and Energy Conservation

Abstract A three-phase four-wire shunt active filter (SAF) with photovoltaic (PV) array operated dc–dc converter is proposed in this paper. When the PV system generates excessive or equal power required to the load demand, then the coordinating logic disconnects the service grid from the load and reduces panel tariff. The PV array is connected to the dc side of SAF through the dc–dc converter with fuzzy-based perturb and observe (P&O) maximum power-point tracking (MPPT) algorithm to eliminate the drawback in the conventional PV system. The reference currents extracted by the fuzzy logic controller-based p-q control strategy. This proposed PV-SAF, if connected at the terminals of a small industry or a home, or a small, lighted institution, can avoid the use of an interruptible power supply and individual stabilizer. A MATLAB simulink is presented to validate the advantage of the proposed system.

Adaptive Backstepping Control of Three-Phase Four-Wire Shunt Active Power Filters for Energy Quality improvement

The increasing use of nonlinear loads entails serious electrical energy quality problem in power grids. In this paper, the energy quality issue is dealt with by using three-phase four-leg shunt active power filters (SAPFs). A new model that describes the whole controlled system including the SAPF and associated nonlinear and unbalanced loads is developed. The model also accounts for the electrical grid line impedance. The control objective is threefold: to make up for the harmonics and the reactive currents absorbed by the loads; to cancel the neutral current; and to regulate the inverter DC capacitor voltage. Based on the new model, a nonlinear controller is designed, using the backstepping technique. Moreover, the controller is made adaptive for compensating the uncertainty on the switching loss power. The performances of the proposed adaptive controller are formally analysed using tools from the Lyapunov stability and averaging theory, and their supremacy with respect to standard control solutions is illustrated through simulation.

Adaptive notch filter solution under unbalanced and/or distorted point of common coupling voltage for three‐phase four‐wire shunt active power filter with sinusoidal utility current strategy

In this study, the three-phase four-wire shunt active power filter (ShAPF) dealing with non-ideal point of common coupling (PCC) voltages will be presented. The instantaneous power theory is applied to design the ShAPF controller which shows reliable performances. An adaptive notch filter (ANF) is proposed to process those unbalanced and/or distorted PCC voltage. The power balance among utility, load and ShAPF while applying ANF is clarified by an in-depth explanation. The simulation results prove that the ANF can successfully facilitate the ShAPF in terms of compensating unbalanced/distorted current of loads under a non-ideal PCC voltage circumstance.

Comparative Study of Three Phase Four Wire Shunt Active Power Filter Topologies based Fuzzy Logic DC Bus Voltage Control

In this paper, a comparative study based fuzzy logic DC bus voltage control for three phase four wire shunt active power filter for two different inverter topologies, three-leg splitcapacitor topology (TLSC) and four-leg inverter (FLFB) are proposed. Identification of reference currents will be developed by classical extraction filters based on pq theory in the first section of the paper. DC-bus voltage control in three-phase four-wire shunt active filter is treated by a fuzzy logic control. A comparison of the proposed method against the conventional proportional integral is illustrated with two different inverter topologies through simulation results and a clear advantage of the fuzzy logic control can be observed. Moreover, the switching pattern of the inverter is generated by a modulated hysteresis current controller. All simulations have been realized in the same conditions so results can be compared with each other. The effectiveness of the proposed method is verified by MATLAB software.

Four hundred Hertz shunt active power filter for aircraft power grids

To fulfill the high reliability of the aeronautical application, a novel three-phase four-wire shunt active power filter (APF) is proposed in this study. In this proposed configuration, traditional phase-leg which is composed of two power switches is replaced by the novel leg composed of one power switch and one diode. The annoying ‘shoot-through’ phenomenon is eliminated by using this novel configuration. Meanwhile, better efficiency and better performance brought by this novel configuration benefit the improvement of the compensation performance. Moreover, operation principle of the APF is analysed in detail; current control strategy and the voltage balance control strategy for the split-capacitor topology are studied as well. Finally, a prototype with the compensating capacity of 3 kVA is designed. Simulation and experimental results are shown to confirm the validity and feasibility of the novel aeronautical APF.

Adaptive non-linear control of three-phase four-wire Shunt active power filters for unbalanced and nonlinear loads.

The problem of controlling three-phase, four-leg shunt active power filters (SAPF) is addressed in presence of nonlinear and/or unbalanced loads. A new control model for four-leg SAPF, taking into account for the electrical grid line impedance, is developed. The control objective is threefold: (i) compensating for the current harmonics and the reactive power absorbed by the nonlinear load; (ii) annulations of neutral line current (iii) regulating the inverter DC capacitor voltage. To this end, based on the new model, a nonlinear controller is developed, using the Lyapunov technical design. It is therefore able to ensure good performances over a wide range variation of the load current. Moreover, the controller is made adaptive for compensating the uncertainty on the switching loss power. The performances of the proposed adaptive controller are formally analyzed using tools from the Lyapunov stability and averaging theory. The supremacy of the proposed controller with respect to standard control solutions is illustrated through simulation

A Noniterative Optimized Algorithm for Shunt Active Power Filter Under Distorted and Unbalanced Supply Voltages

In this paper, a single-step noniterative optimized algorithm for a three-phase four-wire shunt active power filter under distorted and unbalanced supply conditions is proposed. The main objective of the proposed algorithm is to optimally determine the conductance factors to maximize the supply-side power factor subject to predefined source current total harmonic distortion (THD) limits and average power balance constraint. Unlike previous methods, the proposed algorithm is simple and fast as it does not incorporate complex iterative optimization techniques (such as Newton-Raphson and sequential quadratic programming), hence making it more effective under dynamic load conditions. Moreover, separate limits on odd and even THDs have been considered. A mathematical expression for determining the optimal conductance factors is derived using the Lagrangian formulation. The effectiveness of the proposed single-step noniterative optimized algorithm is evaluated through comparison with an iterative optimization-based control algorithm and then validated using a real-time hardware-in-the-loop experimental system. The real-time experimental results demonstrate that the proposed method is capable of providing load compensation under steady-state and dynamic load conditions, thus making it more effective for practical applications.

Three-level H-bridge and three H-bridges-based three-phase four-wire shunt active power filter topologies for high voltage applications

In a three-phase four-wire distribution system, presence of current harmonics, unbalanced loading, reactive power and excessive neutral current play the most important role in deciding power quality. Main culprits behind these are the disturbances caused due to non-linear and unbalanced loads. Here a new three-level H-bridge (3L-HB) topology of three-phase four-wire shunt active power filter (APF) has been developed for load compensation. This can be connected to the distribution lines directly, and does not require any bulky and expensive coupling transformers. Furthermore, this topology of shunt APF has been compared with two-level three H-bridges (3HB) based topology. The performances of APFs are investigated with the help of real-time performance analysis in Opal RT-Lab. A comparison has been made between the two configurations showing their topological differences and load compensation capabilities under ideal, distorted and unbalanced supply voltage conditions. Observations are done taking into consideration the unbalanced loading scenario that is when both three-phase and single-phase loads are present in the system.

A Digital Signal Processor Based Performance Evaluation of Three-phase Four-wire Shunt Active Filter for Harmonic Elimination, Reactive Power Compensation, and Balancing of Non-linear Loads under Non-ideal Mains Voltages

Shunt active power filters are the most viable solution for solving current harmonic, reactive power compensation, and load unbalancing problems widely presented in electrical distribution systems. In this article, development and implementation of a digital signal processor based three-phase four-wire shunt active power filter are analyzed to compensate non-linear and unbalanced loads under non-ideal supply voltages conditions. The proposed algorithm is divided into two parts, the first associated with the calculation of the positive-sequence component of unbalanced supply voltage and second deriving a simple and attractive fundamental extraction filter to extract the fundamental frequency component from distorted positive-sequence voltage. Average power and DC-link energy balance methods are used to calculate peak value of the supply current, which is required to flow from source to load. The behavior and effectiveness of the proposed control algorithm has been verified by simulation using MATLAB/Simulink (The MathWorks, Natick, Massachusetts, USA) environment for different cases of supply voltage. A laboratory prototype has been developed to verify the simulation results. The control scheme is realized using a TMS320F28335 floating-point digital signal processor (Texas Instruments, Dallas, Texas, USA) based system. It is found that simulated and experimental harmonic spectral performances are in compliance with the recommendations about harmonic limits imposed by the IEEE-519 Standard.

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.

Digital signal processor implementation and performance evaluation of split capacitor, four-leg and three H-bridge-based three-phase four-wire shunt active filters

In this paper a comprehensive study on the three-phase four-wire (3P4W) shunt active power filter (APF) is carried out on the basis of three system configurations. These three two-level voltage source inverter topologies are compared for 3P4W shunt APF, namely, split capacitor (2C), four-leg (4L) and three single-phase H-bridges (3HB). The performance of all three topologies, under an unbalanced non-linear load condition, is evaluated with a detailed digital signal processor (DSP)-based experimental investigation. The steady-state as well as dynamic performance of APF is studied to compensate for current harmonics, reactive power, current unbalance and neutral current. The advantages and limitations offered by each of the topologies are also discussed in brief.