scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Correction to “Experimental Design of a Nonlinear Control Technique for Three-Phase Shunt Active Power Filter”

TL;DR: A computational control delay compensation method, which delaylessly and accurately generates the SAPF reference currents, is proposed, and various simulation and experimental results demonstrate the high performance of the nonlinear controller.
Abstract: This paper presents a nonlinear control technique for a three-phase shunt active power filter (SAPF). The method provides compensation for reactive, unbalanced, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently nonlinear SAPF system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the SAPF output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that significantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the SAPF reference currents, is proposed. The first step is to extract the SAPF reference currents from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase diode bridge rectifier with R-L load is taken as the nonlinear load, and then, the reference currents are modified, so that the delay will be compensated. The converter, which is controlled by the described control strategy, guarantees balanced overall supply currents, unity displacement power factor, and reduced harmonic load currents in the common coupling point. Various simulation and experimental results demonstrate the high performance of the nonlinear controller.
Citations
More filters
Journal ArticleDOI
TL;DR: The proposed control scheme requires only two current sensors at the supply side and does not need a harmonic detector, and the performance of the APF is improved significantly compared to the traditional control scheme, thanks to the effectiveness of the proposed compensation scheme.
Abstract: This paper proposes an advanced control strategy to enhance performance of shunt active power filter (APF). The proposed control scheme requires only two current sensors at the supply side and does not need a harmonic detector. In order to make the supply currents sinusoidal, an effective harmonic compensation method is developed with the aid of a conventional proportional-integral (PI) and vector PI controllers. The absence of the harmonic detector not only simplifies the control scheme but also significantly improves the accuracy of the APF, since the control performance is no longer affected by the performance of the harmonic tracking process. Furthermore, the total cost to implement the proposed APF becomes lower, owing to the minimized current sensors and the use of a four-switch three-phase inverter. Despite the simplified hardware, the performance of the APF is improved significantly compared to the traditional control scheme, thanks to the effectiveness of the proposed compensation scheme. The proposed control scheme is theoretically analyzed, and a 1.5-kVA APF is built in the laboratory to validate the feasibility of the proposed control strategy.

224 citations

Journal ArticleDOI
TL;DR: An energy-based Lyapunov function control technique is developed for a three-phase shunt hybrid active filter (SH-AF) to compensate harmonics generated by nonlinear loads and is applied for balanced operation.
Abstract: In this paper, an energy-based Lyapunov function control technique is developed for a three-phase shunt hybrid active filter (SH-AF) to compensate harmonics generated by nonlinear loads and is applied for balanced operation. The method provides compensation for harmonic load current components. The strategy determines the control law that makes the derivative of the Lyapunov function always negative for all values of the states. The dc bus voltage of the SH-AF is maintained to 50 V, which is significantly lower than that of the conventional hybrid active filter. The rating of the active filter in the SH-AF system is much smaller than the one used in the conventional shunt active power filter because the passive filter takes care of the major burden of compensation. The SH-AF performances, during both nominal and severe operating conditions, are then evaluated using a dSPACE DS1104 controller board, supported by a Matlab/Simulink Real-Time Workshop environment. A significantly high correlation between the experimental results and the theoretical model, implemented with Simulink/Matlab, is obtained.

223 citations


Cites background from "Correction to “Experimental Design ..."

  • ...Also, there has been tremendous progress during the last decade in detection techniques and control law implementation mainly due to the development of reliable and very fast digital signal processors (DSPs) [7], [14] and field-programmable gate arrays, allowing therefore the implementation of complex algorithms without altering the switching frequency of the semiconductor devices in the active part of the filter....

    [...]

  • ...A number of control concepts and strategies for active power filters, such as linear feedback control [12], [13], nonlinear control [14], repetitive control [15], neural network approach [16], [17], adaptive control [18]– [21], and Lyapunov-function-based control [22]–[24], have been reported in the literature....

    [...]

Journal ArticleDOI
TL;DR: A new large-signal-based control topology for DG power converters that is suitable for both grid-connected and islanding modes of operation without any need to reconfigure the control system and without islanding detection is presented.
Abstract: The energy sector is moving into the era of distributed generation (DG) and microgrids (MGs). The stability and operation aspects of converter-dominated DG MGs, however, are faced by many challenges. Important among these, are: 1) the absence of physical inertia; 2) comparable size of power converters; 3) mutual interactions among generators; 4) islanding detection delays; and 5) large sudden disturbances associated with transition to islanded mode, grid restoration, and load power changes. To overcome these difficulties, this paper presents a new large-signal-based control topology for DG power converters that is suitable for both grid-connected and islanding modes of operation without any need to reconfigure the control system and without islanding detection. To improve MG stability, the proposed control structure is realized via two steps. First, an emulated inertia and damping functions are adopted. Second, to guarantee stability and high performance of the MG system during sudden harsh transients such as islanding, grid reconnection, and large load power changes, a nonlinear MG stabilizer is proposed. An augmented converter model is developed and used to design the MG stabilizer via the adaptive backstepping (AB) technique to guarantee large-angle stability and robustness against unmodeled dynamics. Theoretical analysis and evaluation results are presented to show the effectiveness of the proposed control scheme in achieving stable and smooth operation of a MG system in grid-connected, islanding, and transition modes.

197 citations

Journal ArticleDOI
TL;DR: Different Distribution Static Compensators (DSTATCOMs) topologies, state of the art, their performance, design considerations, future developments, and potential applications are investigated for power quality improvement.
Abstract: In this paper, different Distribution Static Compensators (DSTATCOMs) topologies, state of the art, their performance, design considerations, future developments, and potential applications are investigated for power quality improvement. These DSTATCOMs for three-phase three-wire systems and three-phase four-wire systems are developed and installed in the distribution system for many functions, such as reactive power compensation, harmonics elimination, load balancing, and neutral current compensation. This paper is aimed to explore a broad perspective on DSTATCOMs to researchers, engineers, and the community dealing with the power quality improvement. A classified list of some latest research publications is also provided for quick reference.

172 citations

Journal ArticleDOI
TL;DR: The proposed topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability, and helps to match the dc- link voltage requirement of the shunt and series active filters of the UpQC.
Abstract: The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. In this paper, a UPQC topology for applications with non-stiff source is proposed. The proposed topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability. This proposed topology also helps to match the dc-link voltage requirement of the shunt and series active filters of the UPQC. The topology uses a capacitor in series with the interfacing inductor of the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the paper. A simulation study of the proposed topology has been carried out using PSCAD simulator, and the results are presented. Experimental studies are carried out on three-phase UPQC prototype to verify the proposed topology.

150 citations

References
More filters
Journal ArticleDOI
TL;DR: The final analysis shows that, in general, the five theories present a different behavior, which depends on supply voltage, with respect to distortion, however, all of them widely decrease the waveform distortion.
Abstract: In this paper, the five main formulations of the instantaneous reactive power theory have been chosen to study nonlinear load compensation. They are p-q original theory, d-q transformation, modified or cross-product formulation, p-q-r reference frame, and vectorial theory. The obtention of the compensation current according to each formulation has been established. Next, the behavior of an active power filter (APF) that is implemented with those different control algorithms has been studied. On one hand, a simulation platform with control, APF, and load has been built to test them. Results obtained in an unbalanced and nonsinusoidal three-phase four-wire system have been compared by means of the most adequate indexes. On the other hand, the APF control strategies have been implemented in an experimental platform constituted by a 20-kVA power inverter and a 400-MHz digital signal processing controller board. The final analysis shows that, in general, the five theories present a different behavior, which depends on supply voltage, with respect to distortion. However, all of them widely decrease the waveform distortion. Moreover, a more general compensation objective is possible. It obtains balanced and sinusoidal source current in any conditions of the supply voltage.

320 citations

Journal ArticleDOI
TL;DR: By their learning capabilities, artificial neural networks are able to take into account time-varying parameters, and thus appreciably improve the performance of traditional compensating methods.
Abstract: In this paper, an efficient and reliable neural active power filter (APF) to estimate and compensate for harmonic distortions from an AC line is proposed. The proposed filter is completely based on Adaline neural networks which are organized in different independent blocks. We introduce a neural method based on Adalines for the online extraction of the voltage components to recover a balanced and equilibrated voltage system, and three different methods for harmonic filtering. These three methods efficiently separate the fundamental harmonic from the distortion harmonics of the measured currents. According to either the Instantaneous Power Theory or to the Fourier series analysis of the currents, each of these methods are based on a specific decomposition. The original decomposition of the currents or of the powers then allows defining the architecture and the inputs of Adaline neural networks. Different learning schemes are then used to control the inverter to inject elaborated reference currents in the power system. Results obtained by simulation and their real-time validation in experiments are presented to compare the compensation methods. By their learning capabilities, artificial neural networks are able to take into account time-varying parameters, and thus appreciably improve the performance of traditional compensating methods. The effectiveness of the algorithms is demonstrated in their application to harmonics compensation in power systems

237 citations

Journal ArticleDOI
TL;DR: An all-digital approach based on a particular repetitive control technique for odd-harmonic discrete-time periodic references and disturbances is used for the current control loops of the active filter to improve robustness of the controlled system.
Abstract: Shunt active power filters have been proved as useful elements to correct distorted currents caused by nonlinear loads in power distribution systems. This paper presents an all-digital approach based on a particular repetitive control technique for their control. Specifically, a digital repetitive plug-in controller for odd-harmonic discrete-time periodic references and disturbances is used for the current control loops of the active filter. This approach does not introduce a high gain at those frequencies for which it is not needed and, thus, improves robustness of the controlled system. The active power balance of the whole system is assured by an outer control loop, which is designed from an energy-balancing perspective. The design is performed for a three-phase four-wire shunt active filter with a full-bridge boost topology. Several experimental results are also presented to show the good behavior of the closed-loop system

207 citations

Journal ArticleDOI
TL;DR: A new topology for active power filters (APF) using an 81-level converter is analyzed, and results are compared with conventional pulsewidth-modulated (PWM) converters, showing that this filter can compensate load current harmonics, keeping better-quality sinusoidal currents from the source.
Abstract: A new topology for active power filters (APF) using an 81-level converter is analyzed. Each phase of the converter is composed of four three-state converters, all of them connected to the same capacitor dc link voltage and their output connected in series through output transformers. The main advantages of this kind of converter are the negligible harmonic distortion obtained and the very low switching frequency operation. The single-phase equivalent circuit is analyzed and their governing equations derived. The dc link voltage control, based on manipulating the converter's voltage phase, is analyzed together with the circuit's characteristics that determine the capability to draw or deliver active and reactive current. Simulation results for this application are compared with conventional pulsewidth-modulated (PWM) converters, showing that this filter can compensate load current harmonics, keeping better-quality sinusoidal currents from the source. The simulated configuration uses a 1-F ultracapacitor in the dc link, making it possible to store energy and deliver it during short voltage dips. This is achieved by applying a modulation control to maintain a stable ac voltage during dc voltage drops. A prototype of the filter was implemented and tested, and the obtained current waveforms showed to be as good as expected.

187 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared the performance of current-source and voltage-source active power filters with different kinds of nonlinear load and the power losses of the active filters.
Abstract: In recent years, active power filters have been widely studied. The research has mainly concentrated on voltage-source active filters, but some attention has also been paid to an alternative-to current-source active filters. Since voltage-source pulsewidth modulation (PWM) technology is widely used in industrial applications, this has also been more common in active filter use. In addition, current-source technology has been said to have drawbacks compared to voltage-source systems, such as high on-state losses in the PWM bridge and inefficient inductive energy storage element on the dc side of the bridge. In the paper, the two active filter topologies are compared. First, the main circuits and space-vector modulation techniques used are studied and the digital control systems are presented. The filtering performances of the systems with different kinds of nonlinear load are examined and finally the power losses of the active filters are studied. The comparison is based on measurements with the prototypes built. The results clearly show the properties of the active filters examined. In addition, the results prove that current-source active filters also offer a considerable choice for harmonic filtering

186 citations