Control Strategy For Active Filter Research Articles

Energy efficiency comparison of shunt active filter's control strategies for three phase four-wire power system

In the presented article, the values of the components of the total power of the three-phase four-wire power supply system for non-sinusoidal asymmetric modes, the condition for achieving a unit value of the power factor and the minimum value of the power losses were clarified. The obtained results were applied to compare the energy efficiency of shuntl active filters (SAF) using different control strategies. Based on the proposed apparent power formula, a new calculation formula for the experimental determination of the power factor has been obtained. It is proved that only the proportional-vector control strategy of the, which uses a reference vector of phase voltages with the optimally weakened zero sequence component, provides a unit power factor and the minimum possible power losses, exceeding other possible strategies in these indicators. It was shown that other known proportional-vector algorithms for forming the source currents of a three-phase four-wire power system with an integral value of the proportionality factor do not provide a unit value of the power factor. To confirm the energy efficiency of the proposed control algorithm for SAF in the MathWorks ® Simulink ® 2012a computer simulation was carried out. The model of a three-phase four-wire power system with a shunt active filter and a nonlinear load in the form of a three-phase rectifier with zero output, assembled according to the Mitkevich scheme and operating on the active resistance was investigated. The results of computer simulation confirmed the advantage of the proposed SAF control algorithm in value of power factor up to 7% in comparison with the algorithm of S. Fryze with full preservation of the zero-sequence component and up to 0.5% in comparison with the algorithm of P. Salmeron, J. Monton with complete suppression of the zero-sequence component. Ref. 9, fig. 3, tabl. 1.

A novel strategy for shunt active filter control

The present paper proposes the use of an advanced algorithm based on the instantaneous powers theory for harmonics current compensation. A fast and exact computation of harmonic references is more than crucial for any active filter control strategy, especially during the transient time and frequency domains. The proposed method contains mainly two stages, the first one is based on a self-tuning filter (STF) to perform instantaneous synchronized sine and cosine fundamental waveforms. These two signals are used to calculate the instantaneous active and reactive powers using the well-known PQ theory. The second one is based on a new proposed method to accelerate the power ripple cancelation in the PQ active and reactive powers. An analytic study is conducted to show the effectiveness of these methods which is consolidated by simulation and experimental results.

Real-Time Implementation of Type-2 FLC–Based Shunt Active Filter Control Strategies (p–q and Id–Iq) with Different Fuzzy MFs for Power Quality Improvement

Abstract This research article proposes the shunt active filter (SHAF) control strategies (p–q and Id–Iq), which are used to improve the power quality of the electrical network by mitigating the harmonics with the help of Type-2 fuzzy logic controller (Type-2 FLC) different membership functions (MFs). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the proposed control strategies has been evaluated in terms of harmonic mitigation and DC link voltage regulation under various source conditions. In order to maintain DC link voltage constant and to generate the compensating reference currents, we have developed Type-2 FLC with different fuzzy MFs (trapezoidal, triangular and Gaussian). The SHAF with proposed Type-2 FLC using Gaussian MF is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed real-time results using real-time digital simulator are presented to support the feasibility of proposed control strategies.

A comparative study on the active power filter control strategy for independent and small power system

Aiming at the serious influence on the power frequency stabilisation for independent power system when its loads are largely changed, a control strategy of active power filter is presented. Firstly, the principle of second-order direct type IIR (infinite impulse response) digital notch filter is described, and the frequency real-time detection model is established based on least mean power (LMP, p = 3) adaptive algorithm to track the notch filter parameters. Then, combining the instantaneous reactive power theory and hysteresis current method, the simulation model of active filter control strategy with power frequency’s change is established. Finally, the simulation results proved that the active power filter model can track the changing frequency quickly and compensate harmonic current accurately. Therefore, the power quality and reliability of the small power grid are enhanced.

Fuzzy logic controller based Shunt Active Filter control strategies for Power quality improvement Using Different Fuzzy M.F.s

Abstract Current harmonics are one of the most common power quality problems and are usually resolved by the use of shunt active filters (SHAF). Control strategies (p-q and id-iq) for extracting the three-phase reference currents for shunt active power filters are compared, evaluating their performance under different source conditions. Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme.The performance of the control strategies has been evaluated in terms of harmonic mitigation and DC link voltage regulation. The proposed SHAF with different fuzzy M.F.s (Trapezoidal, Triangular and Gaussian) is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategies.

Real-time implementation of PI and fuzzy logic controllers based shunt active filter control strategies for power quality improvement

Instantaneous active and reactive power (p–q) and current (Id–Iq) control strategies for extracting the three-phase reference currents for shunt active power filters are compared, evaluating their performance under different source voltage conditions with PI and fuzzy logic controllers in MATLAB/Simulink environment and also implemented using Real-Time Digital Simulator Hardware (RTDS Hardware). When the supply voltages are balanced and sinusoidal, then all control strategies with both controllers converge to the same compensation characteristics. However, when the supply voltages are distorted and/or un-balanced sinusoidal, these control strategies result in different degrees of compensation in harmonics. The p–q control strategy unable to yield an adequate solution when source voltages are not ideal. Extensive simulations are carried out with PI as well as fuzzy logic controller for both p–q and Id–Iq control strategies by considering different voltage conditions and adequate results were presented. On owing Id–Iq method with fuzzy logic controller gives away an out-standing performance under balanced, un-balanced and non-sinusoidal supply conditions. The detailed simulation and RTDS Hardware results are included.

Discussion on Instantaneous $p$–$q$ Strategiesfor Control of Active Filters

Active filters (AFs) compensate harmonic currents demanded by non linear or time variants loads, with the aim to draw sinusoidal currents from the source. Different control strategies for AF have been proposed: among them, p-q theory is the most popular. However, the p-q strategy presents some drawbacks. As already reported in the literature, unexpected harmonic frequencies are generated in the source current as a consequence of such a control strategy. The aim of this paper is to provide, by means of the space vector approach to the p-q theory, analytical expressions that allow to determine the order and the amplitude of the harmonic components in the source current as function of load current or voltage harmonic distortion. By means of these expressions the limits and drawbacks of p-q strategies are quantified and a tool able to quantitatively predict the results of such a control is provided. Simulation results presented in the literature are interpreted according to the proposed expressions; moreover, further simulations are carried out in order to analyze some relevant cases not considered in previous works.

Power factor improvement using active filter for unbalanced three-phase non-linear loads

In this paper, a modified shunt active filter is used under unbalanced three-wire supply voltages with non-linear loads. The main objective of the proposed shunt active filter is to control the three-phase supply currents both in its waveform, magnitude and phase to follow three-phase reference signals. The reference signals are derived from one of the phase voltages. When this is achieved, ideally the supply current will then be always sinusoidal, with robust control over its magnitude and phase, irrespective of the harmonics and unbalance of the load demand or the supply voltage system. This confirms nearly unity power factor on supply side and reactive compensation by the active filter in static-compensator mode. The proposed shunt active filter control strategy is based on hysteresis control, which is very simple to implement and does not even require any measurement of the load demand. The controller performance is improved by incorporating an additional loop that can respond to the variation in the DC bus voltage due to changes in the real and reactive power demand. This paper presents the detailed design analysis of the proposed active filter with simulation and test results obtained from the laboratory implementation.

A control strategy for active filters using quasi‐instantaneous positive sequence extraction filters

AbstractA novel control strategy for active filters, employing quasi‐instantaneous positive sequence extraction of utility voltage, can be useful in harmonic polluted and/or imbalanced utility voltage. In this paper, the authors examined its transient response, its performance under the change of fundamental frequency of utility voltage and its performance under utility voltage with harmonics and unbalance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 54–65, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10307

A Control Strategy for Active Filters using quasi-Instantaneous Positive Sequence Extraction Filters

A novel control strategy for active filters, in which quasi-instantaneous positive sequence extraction of utility voltage is used, can be useful in harmonic polluted and/or imbalanced utility voltage. In this paper, authors examined its transient response, its performance under the change of fundamental frequency of utility voltage and its performance under utility voltage with harmonics and unbalance.

Three-phase four-wire shunt active filter control strategies

This paper describes a three-phase four-wire shunt active power filter using a conventional three-leg converter, without the need of power supply at DC bus. Two approaches have been developed to control the active filter. Both control strategies consider harmonics and zero sequence components in the voltage and current simultaneously. The first one provides constant power and the second one sinusoidal current to the source, even under unbalanced voltage conditions. Simulation results from a complete model of shunt active filter are presented to validate and compare the control strategies.