Universal Active Power Filter Research Articles

An Enhancement of Power Quality With Efficient Active Power Transfer Capability in a PV–BSS-Fed UAPF for Microgrid Realization

This article investigates the enhancement of power quality with an efficient active power transfer capability in a universal active power filter (UAPF) integrated with a photovoltaic (PV) and battery storage system (BSS). The UAPF operates as a bidirectional interface between the PV–BSS and point of interconnection for microgrid realization. A new control strategy is proposed to extract fast and accurate voltage and current reference signals to operate the system in a desired manner. Here, the extraction of load voltages and calculation of load and reference powers are used to generate the reference signals, thereby comparing with actual signals with hysteresis controller to produce switching pulses of converters. As a result, the shunt and series converters form a robust system by acting as a current-controlled voltage source and voltage-controlled current source, respectively. It eliminates the need for adaptive filters and low-pass filters to extract the fundamental component of the load current. Furthermore, it increases the conversion efficiency of converters and improves the static and dynamic performance of the system. The proposed system is developed with a 1-kVA prototype laboratory setup using a field-programmable gate array controller and extensively tested with various test conditions such as grid voltage fluctuations, nonlinear and imbalanced load, and change in irradiance.

A Novel Control Scheme Using UAPF in an Integrated PV Grid-Tied System

This article investigates the photovoltaic fed universal active power filter (PV-UAPF) system for enhancing power quality indices. A novel comb filter together with second-order generalized integrator (CFSOGI) based instantaneous power balance theory with power angle (IPBTPA) control scheme is implemented. Under distorted or adverse grid conditions, the CFSOGI effectively extracts the phase angle, frequency, and fundamental positive and negative sequence components (FPNSC) to overcome the limitations of adaptive notch filters. Here, a comb filter constitutes a cluster/group of zeros at multiple harmonic frequencies to achieve notch peaks thereby providing superior harmonic rejection ability. Whereas, IPBTPA generates the reference signals to operate the system at dual compensation strategy with or without solar PV. The power angle is used to extract the desired load voltages under grid voltage fluctuations thereby reducing the burden on the shunt converter. Moreover, the hysteresis controller generates the switching pulses based on the calculation of reference and load powers which improves the dynamic performance by maintaining system power balance and effective DC voltage regulation. Besides, reactive power compensation, suppression of harmonic currents and mitigation of grid voltage fluctuations is also carried out to strengthen the system further. The system is also tested in grid voltage interruption for islanding mode to realize a microgrid system. The overall system performance is also validated using simulation and in a real-time experimental set-up, and results are demonstrated under various conditions.

Real-Time Implementation of PV fed Universal Active Power Filter Using CF-SOGI based IPBT Control Scheme

This paper proposed a new control scheme of comb filter based second-order generalized integrator (CF-SOGI) in instantaneous power balance theory (IPBT) for photovoltaic (PV) fed universal active power filter (UAPF). The conventional SOGI frequency locked loop (SOGI-FLL) can provide good accuracy and fast dynamics, and better filtering abilities during idle grid conditions. To enhance the filtering ability and improve the accuracy under distorted conditions usually multiple notch filters are used. However, it suffers from a heavy computational burden due to the presence of multiple filters, the system becomes a complex structure and deteriorate dynamic performance. To overcome the above a comb filter is incorporated in the conventional SOGI-FLL. It extracts the frequency and fundamental positive component of voltage under adverse grid voltages. Along with it, a new IPBT control scheme generates the reference signals for UAPF using reference and load power calculations. It improves the dynamic performance by maintaining power balance in the system along with effective DC voltage regulation. The proposed system enhances the power quality issues on both source and load side as per IEEE-519 and integrates the PV into the utility grid on a two-stage topology. Also, it extracts the maximum power from the PV and delivers it to the load and grid connected at the point of interconnection (PIC). The system with the proposed control scheme is simulated on MATLAB/Simulink and the same is validated in the laboratory prototype experimental setup. The performance of a system is validated under grid voltage fluctuations, non-linear load, unbalance load, and change in irradiation conditions.

Renewable integrated UAPF fed microgrid system for power quality enhancement and effective power flow management

In this paper, renewable energy integrated universal active power filter (UAPF) is proposed for the microgrid system. Here, renewable energy sources such as solar and wind with the battery storage system are integrated at DC-link of UAPF. In the proposed microgrid system, the centralized microgrid controller (CMC) is implemented for power quality enhancement and effective power flow management. The main objective of the CMC is to achieve effective utilization of RES, seamless power transfer under various operating conditions, reliable and supplying quality power to the load. In CMC, the instantaneous power balance theory (IPBT) is implemented to generate the switching pulses to shunt active power filter (ShAPF) and series active power filter (SeAPF) for power quality enhancement. In addition, the power flow management strategy is integrated into CMC to generate the appropriate reference signals to the various DC-DC converters for efficient power flow management. The system with the proposed control scheme is simulated on MATLAB/Simulink and the same is validated in the experimental setup under various modes such as interconnected, isolated, and floating mode. In real-time hardware setup, a field-programmable gate array is used for parallel processing of microgrid components.

PV integrated universal active power filter for power quality enhancement and effective power management

This paper presents a new control scheme for solar photo-voltaic (PV) integrated universal active power filter (PV-UAPF). Here, the instantaneous power balance theory (IPBT) is proposed to extract the reference signals for shunt active filter (ShAPF) and series active power filters (SeAPF). Thereby, ShAPF will act as a pure sinusoidal voltage source and SeAPF will act as a pure sinusoidal current source. In the IPBT control scheme, the frequency locked loop (FLL) based modified reduced order generalized integrator (MROGI) is proposed to extract positive and negative sequence components (PNSC) and phase angle during adverse grid conditions. Also, the PV integration at the DC link will reduce demand on the supply system thereby reduces the burden on the utility grid. Hence, the proposed system combines both the benefits of clean energy generation along with power quality improvement. To validate the performance of the proposed system, simulation is developed in MATLAB, and results are verified. Also, the system performance is then verified in the hardware setup under various disturbances such as voltage sag/swell, load distortion, and change in PV power.

DIGITAL WALLET USING ARM MICROCONTROLLER

In this work, a novel technique based on second order sequence filter and proportional resonant controller is proposed for control of universal active power filter integrated with PV array system (UAPF-PV). Using a second order sequence filter and sampling it at zero crossing of instant of the load voltage, the active component of distorted load current is estimated which is further used to generate reference signal for shunt active filter. The proposed method has good accuracy in extracting fundamental active component of distorted and unbalanced load currents with reduced mathematical computations. Along with power quality improvement, the system also generates clean energy through the PV array system integrated to its DC-bus. The UAPF-PV system integrates benefits of power quality improvement and distributed generation. The system performance is experimentally evaluated on an experimental prototype in the laboratory under a variety of disturbance conditions such as PCC voltage fall/rise, load unbalancing and variation in solar irradiation

UAPFs topologies with UPS features for low and medium voltage applications

Some configurations of universal active power filter (UAPF) with uninterruptible power supplies (UPSs) features for single-phase applications are proposed in this study focus on a reduced number of power electronic switches. All proposed configurations, composed by two-leg converters, compensate for current and voltage harmonics and provide power factor control close to one. Comparisons between the structures are made in terms of converters voltage capabilities, shared-leg, and capacitor currents. The model of the systems, including the equations and control system, is detailed described. Steady-state analysis of the proposed configurations demonstrates the existence of a load angle, which reduces the converters current, increasing the efficiency of the proposed systems. A complete set of simulated and experimental results are presented.

Implementation of Solar Photovoltaic System With Universal Active Filtering Capability

In this paper, a novel technique based on a second-order sequence filter and a proportional resonant controller is proposed for the control of a universal active power filter integrated with a photovoltaic array (UAPF-PV). Using a second-order sequence filter and sampling it at zero-crossing instant of the load voltage, the active component of the distorted load current is estimated, which is used to generate a reference signal for a shunt active filter. The proposed method has good accuracy in extracting a fundamental active component of distorted and unbalanced load currents with reduced mathematical computations. Along with power quality improvement, the system also generates clean energy through the PV array system integrated to its dc link. The UAPF-PV integrates benefits of power quality improvement and distributed generation. The system performance is experimentally evaluated on a prototype in the laboratory under a variety of disturbance conditions, such as point of common coupling voltage fall/rise, load unbalancing, and variation in solar irradiation.

Single‐phase universal active power filter based on ac–dc–ac converter with eight controlled switches

This study presents an ac–dc–ac converter with eight controlled switches. The proposed topology is applied as a universal active power filter, compensating for disturbances in the grid voltage, voltage sags/swells, and harmonics generated by non-linear loads. The difference between the proposed and conventional solution is the addition of an uncontrolled leg (composed only of diodes) to increase the number of voltage levels, reducing harmonics and the average switching frequency. For performance comparisons, current total harmonic distortion (THD), voltage weighted THD, switching and conduction losses of the semiconductors, and average switching frequency were used as parameters. Control and pulse-width modulation techniques based on space vector approaches were developed to eliminate zero-crossing distortions caused by the use of the uncontrolled leg. Simulation and experimental results were presented for validation of the mathematical model.

Control of Single-Phase Solar Power Generation System With Universal Active Power Filter Capabilities Using Least Mean Mixed-Norm (LMMN)-Based Adaptive Filtering Method

This paper deals with the control of a single-phase grid-tied solar photovoltaic (SPV) power generation system with an universal active power filter (UAPF) capabilities. The SPV-UAPF system consists of series and shunt voltage-source inverters (VSIs). The shunt VSI exports the real power extracted from the photovoltaic panels to the grid and local loads. In addition to handling the real power, the shunt VSI provides compensation of reactive and harmonic currents generated by the loads. The reference signals required for the control of the shunt and series VSIs of the SPV-UAPF system are estimated using the least mean mixed-norm (LMMN) adaptive identification algorithm. The performance of the LMMN-based control of the SPV-UAPF system with series shunt compensation capabilities is demonstrated using MATLAB/Simulink-based computer simulations and hardware-in-the-loop-based experimental results under various operating conditions such as solar irradiance variation, voltage sag, swell, and current harmonics.

Single-Phase Universal Active Power Filter Based on Four-Leg AC–DC–AC Converters

This paper presents two universal active power filters (UAPFs) configurations using single-phase four-leg ac–dc–ac converters. The proposed topologies are used for disturbance compensation in the power supply, such as voltages sags/swells, and to compensate harmonic distortions in the current. The operation of the proposed configurations is compared with the conventional single-phase four-leg UAPF. The harmonic distortions, semiconductor losses, and average switching frequency are used as comparison parameters. Compared to the conventional configuration, the proposed topologies use a transformer with lower power, provide lower average switching, and reduced current total harmonic distortion (THD) and voltage weighted THD. The pulsewidth modulation (PWM) strategy was designed based on a space vector modulation technique, and a control system for the grid current and dc-link bus voltage regulation was also developed. Simulation and experimental results are presented showing the efficiency of the PWM and control strategies and validating the proposed topologies.

Three-Phase Four-Wire AC–DC–AC Multilevel Topologies Obtained From an Interconnection of Three-Leg Converters

This paper investigates ac–dc–ac multilevel topologies for three-phase four-wire applications obtained from an interconnection of three-leg voltage-source converters. The topologies can be applied in line voltage regulators, universal active power filters, and uninterrupted power supplies. Operating principles, a pulsewidth modulation (PWM) technique, and an overall control strategy are developed. The PWM and control strategies are suitable to regulate the dc-link voltages and to reduce the harmonic distortion, switching stress, and power losses. Simulation results are used to compare the proposed configurations with a conventional solution in terms of harmonic distortion, semiconductor losses, and others characteristics. Experimental results are presented to validate the theoretical considerations and were obtained by using insulated-gate bipolar transistors with dedicated drives and a digital signal processor with appropriated plug-in boards and sensors.

Control of a Solar Photovoltaic Integrated Universal Active Power Filter Based on a Discrete Adaptive Filter

In this work, a novel technique based on adaptive filtering is proposed for the control of a three-phase universal active power filter with a solar photovoltaic array integrated into its dc bus. Two adaptive filters along with a zero crossing detection technique are used to extract the magnitude of a fundamental active component of distorted load currents, which is then used in estimation of a reference signal for the shunt active filter. This technique enables extraction of an active component of all three phases with reduced mathematical computation. The series active filter control is based on synchronous reference frame theory and it regulates load voltage and maintains it in-phase with voltage at point of common coupling under conditions of voltage sag and swell. The performance of the system is evaluated on an experimental prototype in the laboratory under various dynamic conditions such as sag and swell in voltage at point of common coupling, load unbalancing, and change in solar irradiation intensity.

Transformerless Single-Phase Universal Active Filter With UPS Features and Reduced Number of Electronic Power Switches

This paper presents an universal active power filter for harmonic and reactive power compensation with uninterrupted power supplies (UPS) features. The configurations does not use transformer in the series part. Transformerless modern UPS systems have been rapidly replacing the old technology due to their performance and size attributes. Reducing the numbers of passive elements and/or switches in active power filters and UPS topologies not only reduces the cost of the whole system but also provides some advantages, such as great compactness, smaller weight, and higher reliability. However, the cost reduction requires the use of more complex control strategies. The model of the proposed system is derived and it is observed that the system can be reconfigurable to operate with four or three leg depending on the issue. A complete control system, including the pulsewidth modulation techniques, is developed and a comparison between the proposed filter and the standard one is done, as well. Simulated and experimental results validate the theoretical considerations.

Multivariable load current sensorless controller for universal active power filter

The universal active power filter is one of most efficient solutions to problems related to energy quality. The topology integrates series and parallel active filter, and theoretically has the compensation capacity of both. The efficiency of compensation, however, is dependent on the control strategy implemented. Moreover, the controller determines the necessary number of sensors and measurement techniques, consequently, it determines associated costs. This study uses a multivariable approach for synthesis and development of a decoupled control. The proposed strategy uses only measuring of the input currents, thereby reducing the number of current sensors. The strategy is validated in simulation and experimentally in a 1.1 kVA laboratory prototype.

The Transformerless Single-Phase Universal Active Power Filter for Harmonic and Reactive Power Compensation

This paper presents a universal active filter for harmonic and reactive power compensation for single-phase systems applications. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the system is derived and it is shown that the circulating current observed in the proposed active filter is an important quantity that must be controlled. A complete control system, including pulse-width modulation (PWM) techniques, is developed. Comparisons between the structures are made from weighted total harmonic distortion (WTHD). The steady-state analysis is also presented in order to demonstrate the possibility to obtain an optimum voltage angle reducing the current amplitude of both series and parallel converters and, consequently, the total losses of the system. Simulated and experimental results validate the theoretical considerations.

Single-phase Active Power Filters With Reduced Number Of Power Switches And Optimum Voltage Control Angle


 This paper proposes some topologies of universal active power filter for single-phase applications with reduced number of components. Some configurations are proposed: two with both series and parallel converters connected in half-bridge, sharing the same d.c.-bus mid-point connection; and the others with the series and parallel converters sharing one leg. It will be demonstrated the existence of a coupling law between the two converters (Se and Sh) related to the voltage capabilities. All configurations compensate current and voltage harmonic and provide power factor control close to unit. Comparisons between the structures are made and the steady-state analysis are also presented to demonstrate that it is possible to obtain an optimum voltage angle in order to reduced the amplitudes of the converters’ currents and, consequently, the total losses of the systems. Simulated and experimental results validate the theoretical considerations.

Single-Phase to Three-Phase Universal Active Power Filter

In this paper, a universal active power filter is proposed for harmonic and reactive power compensation in the single-phase to three-phase systems. The proposed configuration solves a typical problem found in remote (or rural) applications, where only a single-phase grid is available and there is a demand to supply three-phase loads. A suitable control strategy is presented to regulate the load voltage, the power factor, and to minimize the voltage and current harmonics simultaneously. Simulated and experimental results are also presented.