Active Power Filter Research Articles

A Novel Three-Dimensional Sigma–Delta Modulation for High-Switching-Frequency Three-Phase Four-Wire Active Power Filters

This article presents a new modulation technique called three-dimensional sigma–delta (3D-ΣΔ) modulation for high-frequency three-leg four-wire voltage source converters (VSCs) that use wide-bandgap (WBG) semiconductors. These WBG devices allow for the use of high switching frequencies with a greater efficiency than silicon devices. The proposed 3D-ΣΔ technique enables operation at a variable switching frequency, resulting in a significant reduction in switching losses compared to classical pulse-width modulation (PWM) techniques. Moreover, the 3D-ΣΔ technique uses a fast-processing 3D quantiser that simplifies implementation and considerably reduces computational costs. The behaviour of the 3D-ΣΔ modulation is analysed using MATLAB/Simulink and PLECS. The experimental results performed on an active power filter that uses silicon carbide (SiC) MOSFETs demonstrate an improvement in converter efficiency compared to the conventional SPWM technique. Additionally, the experimental results show how 3D-ΣΔ allows for the compensation of harmonics and homopolar currents, thereby balancing the electrical grid currents. The experiments also show that the proposed 3D-ΣΔ modulation outperforms an SPWM technique in terms of power quality, since the former achieves a larger reduction in the harmonic content of the power grid. In conclusion, the proposed modulation technique is an attractive option for improving the performance of four-wire converters in active power filter applications.

Optimal siting and sizing of custom power system and smart parking lot in the active distribution network

AbstractNon‐linear loads, electrical vehicles (EVs) and power electronics are the sources of harmonic generation in the power system. Harmonics are the reason for the disturbance in the technical constraints and quality of the power system. These disadvantages are formed in the current and the voltage of the system branches and buses. To reduce these harmonics, active and passive power filters are used. Since active power filters (APFs) include electronic power switching devices, they are used to eliminate or reduce current or voltage harmonics. To properly reduce these harmonics and supply consumer demand, private investors (PIs) are considered to enhance the power quality, by investing in the APF units and the distribution network operator (DNO) coordinating and feeding the EVs, by equipping the network with smart parking lots. Total harmonic distortion, bus voltage profile, active power loss and energy not supplied (ENS) are considered problem attributes. Using techniques for order of preference by similarity to the ideal solution (TOPSIS), it is determined how the addition of photovoltaic (PV), energy storage system, and batteries affects the ranking of attributes from the perspectives of both DNO and PI. The best solutions are obtained in the first stage using a genetic algorithm (GA), and the attributes have been prioritized from a utility perspective in the second stage by TOPSIS. To verify the performance of GA and TOPSIS, all of the obtained results are compared with the other algorithms. As seen clearly, active, reactive power loss and ENS in scenarios with the participation PV are reduced. Furthermore, comparing the results of different algorithms confirms the efficiency of GA and TOPSIS.

Comparison between Active power filter with selective control and conventional control for harmonic in photovoltaic systems

In order to to improve the power quality from energy generated by the photovoltaic systems connected to the network, this paper presents the results of two types of filters, first the active power filter with conventional control scheme and second, active power filter with a selective control scheme in order to reduce the harmonic content injected by the inverter in a photovoltaic system. The results are presented and compared by means of harmonic distortion (individual and THD). This is a novel proposal, since studies before to this, always have been interested in the compensation of harmonics arising from non linear loads but rarely from a voltage source, as in this case.

Simplified Control Method for Unified Power Quality Conditioner (UPQC)

Unified Power Quality Conditioner (UPQC) for harmonic elimination and simultaneous compensation of voltage and current, which improves the power quality offered for other harmonic sensitive loads. UPQC consist of combined series active power filter that compensates voltage harmonics of the power supply, and shunt active power filter that compensates harmonic currents of a non-linear load. In this paper a new control algorithm for the UPQC system is optimized and simplified without transformer voltage, load and filter current measurement, so that system performance is improved. The proposed control technique has been evaluated and tested under dynamical and steady state load conditions using PSIM software. The laboratory prototype experimental results for shunt active filter part are given.

IMPACT OF NON-LINEAR SMALL POWER RECEIVERS ON LOW VOLTAGE NETWORK OPERATION CONDITIONS

The paper discusses the causes of distorted waveforms of currents and voltages in industrial electric power systems of low voltage. The ascending contribution of domestic and municipal customers, particularly office and as commercial as well as service and shopping centers where, non-linear loads and load phase unbalance are common, is indicated. Studies of voltage and current waveforms and their harmonics spectra at selected this type of facilities were carried out. The ability to compensate for the negative impact of low power consumer receivers using the active power filter has been demonstrated.

Harmonic compensation using a single phase active filter

This work presents the implementation of a single phase parallel active filter for harmonic compensation. The idea is to optimize the processed power by the active single-phase filter restricting the compensation only to harmonic currents without processing the linear reactive one. It is made a comparison study of processed power by a conventional active power filter compensating the entirely reactive power and another compensating only the harmonic contents. It is presented the control methodology employed, the power circuit design and the results obtained through a 500VA experimental prototype.

Control strategy for an interface to improve the power quality at the connection of AC microgrids

In this paper, a control strategy is proposed for an interface which is connected between a microgrid and main grid. The interface is based on an active power filter configuration of series connection. The proposed control strategy allows mitigating of current harmonics and reduction of voltage unbalances that may appear at the microgrid side and/or at the network side. The proposed strategy was verified by simulation. To do this, a simulation platform based on MATLAB-Simulink was developed. The interface was subjected to voltage unbalances and current harmonics produced at the microgrid side and main grid side. The results obtained demonstrate the validity of the designed interface with the proposed strategy.

Control strategy to improve the power factor with a hybrid filter

Nowadays an electrical system must provide adequate electrical power quality so that it meets the international standards. To do this, this paper develops a control strategy for an active compensator based on a hybrid filter topology. This topology is formed by an active power filter of series connection and a passive filter of parallel connection. The proposed strategy is based on minimizing the rms value of the voltage at the point of common coupling so that the source transfers the power demanded by the load. Thus, the determination of the reference signal is posed as a constrained optimization problem. The strategy was proposed for four-wire systems and it allowed the compensation of current harmonics, reactive power and neutral current. Finally, a simulation platform in Matlab-Simulink was developed. This allowed the verification of the new strategy for different types of loads.

Three-phase four wire shunt active power filter based on Simplified Backstepping technique for DC voltage control

This work presents a simulation of Three-Phase Four-Wire Shunt Active Power Filter (SAPF) destined to suppress harmonic currents generated by nonlinear loads. The SAPF guarantee also the compensation for unbalanced nonlinear load currents, reactive power and harmonic neutral current. The identification method is based on the synchronous reference frame. In order to have good performances of DC voltage control, simplified Backstepping control for three-Phase four-Wire (SAPF) system is proposed. Complete simulation of the resultant active filtering system validates the efficiency of the proposed simplified Backstepping control law over to the traditional control with PI controller.

Improved Structure for Three-Phase Four-Wires Hybrid Active Power Filters

This paper presents a novel three-phase four-wire low power rating flexible hybrid active filter with a power factor, harmonic and neutral currents capability for distribution systems. The passive filter is tuned to compensate the two largest harmonics components and the power factor of the load. A selective algorithm is employed in order to enable the active filter to compensate only the desirable harmonic components. Simulation results are presented in order to verify the performance of the proposed hybrid filter.

Improvement of the electric energy quality by use of active power filters

The paper presents basic theories of electrical power used to analyze phenomena in electric circuits with deformed waveforms of current and voltage. Discusses investigated results of application of an active power filter developed on the basis of concept of physical components of the current (CPC).

Harmonics Cancelation in 3-Phase 4-Wire System using Modified Reference Frame

In this paper, A modified synchronous reference frame (SRF) or (d-q theory) with Self-Tuning Filter (STF) for the three-phase four wires system is presented to control of 4-legs shunt active power filter (SAPF) under balanced supply voltages. The main goal of the paper is to apply this control method using unit vector generation with STF instead of PLL circuit. In utility power system, it has been observed that harmonics build a major role in reducing the power quality. These harmonics caused by nonlinear loads. Many consumers appliances demand quality of power continuously for their operation. The performance of the end user equipment is heavily dependent on the quality of power supplied to it. This power is affected by various external and internal factors. They are like voltage and frequency variations, faults, outages etc. The solution to overcome these problems is to filter out these harmonics. For this purpose, there are many filters' topologies and control methods are proposed and studied in the literature to eliminate harmonics currents. In our study, 4-legs shunt active power filter is proposed and controlled by d-q method with modified unit vector generation. The SAPF is proposed to solve problems of line harmonic currents and neutral line currents of three phase 4-wire power distribution system. The use of STF in the modified control method can optimize the performance of this topology regarding to classical one (high pass and low pass filters). The proposed control strategy is simulated in MATLAB Simulink and the results are presented.

Discussions on the Instantaneous Reactive Power Theory Terms in the General Case Based on the Symmetric Components

This paper deals with the presentation of different terms of the powers presented in the Instantaneous Reactive Power Theory (IRPT) in the general case of a generic power system voltage. This presentation is based on the use of the symmetric components in the E. Clarke stationary frame, where the instantaneous real active power, the instantaneous imaginary reactive power and the instantaneous zero sequence power are divided into their DC components and AC components function of the symmetric components. The contributions of these terms in the transfer of the energy from the power supply to the load in four wire system are explained, hence, a good choice of the power to be compensated using shunt active power filter can be obtained. Finally, simulation results are presented under unbalanced and distorted generic power system voltages, where different terms of the instantaneous reactive power theory are clarified and presented based on symmetrical components.

Comparison of Multi-Resonant- and Hysteresis Band Controllers used in Current Control Loop of Shunt Active Power Filter

In the paper the advantages and disadvantages of both current control loops with hysteresis and resonant types are presented by simulation analyses and experimental results. The result of comparison defines some recommendations for the fields of use of shunt active power filter controlled by these regulators.

Design and dynamic analysis of superconducting magnetic energy storage-based voltage source active power filter using deep Q-learning

Design and dynamic analysis of superconducting magnetic energy storage-based voltage source active power filter using deep Q-learning

Simulation and optimization of control parameters in energy hybrid filter

Two energy hybrid filter systems were considered which reduce level of higher mains current harmonics. An advantage of such system is low demanded active filter power because in complements only passive filter operation. The first considered system has inverter switched on in series with shunt passive filter. Through optimization of control parameters it is able to eliminate specific higher mains currents harmonics left by passive filter in a point by point way. The other tested system includes two inverters which are switched on to the system in series and shunt way. Their operation is to reduce higher mains current harmonics induced by higher load currents harmonics in a continuous way. The simulations carried out proved correct operation of the system.

Neural-Networks and Synchronous Reference Frame Applied in the Harmonic Compensation with a Three-Phase Parallel Active Power Filter

This paper presents an alternative method based on artificial neural network, which is used to obtain the reference currents for harmonic current suppression and reactive power compensation in a shunt active power filter applied to three-phase four-wire system. The neural network consists of a multilayer perceptron, which is trained to estimate the peak amplitude of the load fundamental component currents. The performance of the proposed artificial neural network is evaluated by computer simulation, and it is compared with the method based on synchronous reference frame

Analysis on Stability in Control of Active Power Filter in Electric Grid with Megawatt DFIG Wind Farm Connected

This paper presents a pretty comprehensive analysis on stability issues of control for active power filter (APF) installed in an electric grid where megawatt doubly fed induction generator (DFIG) wind farm is connected. Major objectives of this paper are to evaluate roles and impacts of main design parameters in the controller of APF. As well, the ultimate goal is to determine the stable value range and the suitable-performance value range for a proportional control coefficient in APF. Wherein, firstly, background theories of the voltage-detection control method for APF to reduce the voltage and current distortions on the electric grid are described. Furthermore, an appropriate equivalent circuit of a typical grid-connected DFIG wind farm with APF to analyze impedance in the frequency domain is introduced. After that, mathematical formulas and algorithm to determine the stable value range and suitable performance value range for the control coefficient in APF are proposed. Finally, results obtained with the suggested equivalent circuit and impedance analysis technique are shown and discussed in detail. Besides, different operation cases of the controller of APF and the illustrative DFIG wind farm, including parametric uncertainties of the electric grid, also are examined to assess effectiveness of the proposed analysis algorithm.

A New Design of UPQC-Based Hybrid Multi-Carrier Modulation for Transformer Less Grid Connected PV-Based Active Power Filter

In recent times, there has been a growing concern over the augmented power consumption, leading to a pressing need for compensating devices to maintain power quality in grid-connected systems. One extensively employed solution is the Unified Power Quality Conditioner (UPQC), which incorporates both shunt and series active power filters (APFs) connected through a DC-link capacitor. However, traditional systems using compensating devices can be costly and cumbersome, often relying on transformers to interface with the grid. To address these drawbacks, this report proposes a transformer-less networking approach using a multi-level inverter (MLI) that reduces the number of switches in the shunt and series APF. To enable the efficient operation of the MLI in UPQC, the report utilizes Synchronous Reference Frame Theory and Hybrid Multi-Carrier Pulse Width Modulation (H-MCPWM) techniques for reference signal generation and gate control, respectively. MATLAB/Simulink simulation version 2019a is employed to validate the performance of the proposed system, along with a hardware prototype featuring a motor load. A key aspect of the investigation involves conducting harmonic analysis for various modulation indices with a non-linear load. The resulting data is then compared to the outcomes of the conventional model. By exploring this approach, the report aims to showcase the viability of the transformer-less networking of MLI in UPQC, thereby paving the way for more cost-effective and efficient grid-connected systems with improved power quality.

Fuel cell inverters used for unbalance compensation in low voltage distribution systems

The aim of this paper is to evaluate the benefits that can be achieved by operating the connection inverters of the distributed energy resources as active power filters in LV distribution networks. The use of the future fuel cell inverters to compensate zero sequence currents, arising from unbalances among phases, can improve the efficiency of the distribution networks by means of reducing the total amount of losses. A common unbalanced load connected to a LV feeder where a FC inverter is present has been simulated. The reductions in the distribution power losses and compensation of zero sequence currents have been analyzed.