J.-C. Wu

Bio: J.-C. Wu is an academic researcher. The author has contributed to research in topics: Power electronics & Current sensor. The author has an hindex of 1, co-authored 1 publications receiving 181 citations.

Simplified control method for the single-phase active power filter

Abstract: A simplified control method for the single-phase active power filter is proposed. This method has the advantages of using only one current sensor, a simple control circuit and low implementation cost. A model of this method is derived. A prototype is also developed to demonstrate the performance of this method. The test results show that the proposed active power filter has the expected performance.

Odd-harmonic digital repetitive control of a single-phase current active filter

Abstract: Shunt active power filters have been proved as useful elements to correct distorted currents caused by nonlinear loads in power distribution systems. This work presents an all-digital approach, based on the repetitive control technique, for their control. In particular, a special digital repetitive plug-in controller for odd-harmonic discrete-time periodic references and disturbances is used. This approach does not introduce high gain at those frequencies for which it is not needed, and thus it improves robustness. Additionally, the necessary data memory capacity is lower than in traditional repetitive controllers. The design is performed for the particular case of single-phase 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.

Control techniques for active power filters

Abstract: There have been many variants of the active power filter proposed and these variations cover both the circuit topology and the control system employed. Some of the control variants reflect different control objectives but there are still many variants within similar objectives. The available control techniques are described and contrasted in a structured way to identify their performance strengths. Objectives are classified by the supply current components to be corrected and by the response required to distorted grid voltage. The various signal transformations are described in terms of their impact on the distortion identification problem. Time-domain, frequency-domain, instantaneous power and impedance synthesis methods are examined. Additional control functions such as DC-bus voltage and current reference following are also discussed. It is found that a key difference between control methods is the way in which current distortion is treated in the presence of distorted grid voltage.

Selective Harmonic-Compensation Control for Single-Phase Active Power Filter With High Harmonic Rejection

Abstract: This paper presents a linear current control scheme for single-phase active power filters. The approach is based on an outer voltage loop, an inner current loop, and a resonant selective harmonic compensator. The design of the control parameters is carried out using conventional linear techniques (analysis of loop gain and other disturbance-rejection transfer functions). The performance of the proposed controller is evaluated and compared with two reference controllers: a basic control and an advanced repetitive control. In comparison with these controllers, the proposed control scheme provides additional attenuation to the harmonics coming from the load current, the grid voltage, and the reference signal, resulting in a grid current with lower harmonic distortion. Experimental results are reported in order to validate this paper.

Unified constant-frequency integration control of active power filters-steady-state and dynamics

Abstract: An active power filter (APF) is a device that is connected in parallel to and cancels the reactive and harmonic currents from a group of nonlinear loads so that the resulting total current drawn from the AC mains is sinusoidal. This paper presents a unified constant-frequency integration (UCI) APF control method based on one-cycle control. This method employs an integrator with reset as its core component to control the pulse width of an AC-DC converter so that its current draw is precisely opposite to the reactive and harmonic current draw of the nonlinear loads. In contrast to previously proposed methods, there is no need to generate a current reference for the control of the converter current, thus no need for a multiplier and no need to sense the AC line voltage, the APF current, or the nonlinear load current. Only one AC current sensor is used to sense the AC main current and one DC voltage sensor is used to sense the DC capacitor voltage. The control method features constant switching frequency operation, minimum reactive and harmonic current generation, and simple analog circuitry. It provides a low cost and high performance solution for power quality control. Steady-state and dynamic study is presented in this paper. Design example is given using a two-level AC-DC boost topology. A prototype was developed to demonstrate the performance of the proposed APF. This control method is generalized to control a family of converters that are suitable for APF applications. All findings are supported by experiments and simulation.

A new control strategy for single-phase shunt active power filters using a Lyapunov function

Abstract: This paper proposes a new control strategy for single-phase shunt active power filters (APFs) based on Lyapunov's stability theory. The idea in this strategy is to form an energy-like Lyapunov function in terms of the active filter states and then determine the control law that makes the time derivative of the Lyapunov function always negative for all values of the states. It is shown that a globally stable control is possible at the expense of a time-varying reference function for the direct current (dc) capacitor voltage. This method, however, requires the estimation or measurement of the harmonic ripple component on the dc capacitor voltage. Therefore, a modified control is proposed by ignoring this ripple component. The active filter's current reference is obtained by subtracting the measured load current from the generated supply current reference. The amplitude of the supply current reference can be adjusted by using a proportional-integral (PI) controller that regulates the dc capacitor voltage. Experimental results that are obtained for steady-state operation and step changes in the load are presented to verify the correct operation of the proposed control strategy.