Research of hybrid active power filter based on FBD method detection
To fast and effectively detect harmonic current of power system, FBD method is proposed. Compared with method which is based on instantaneous reactive power, FBD method has no complex transformation and transformation, it can be used to detect harmonic current for single-phase, three-phase three-wire and three-phase four-wire system. But FBD method needs a low-pass filter to extract the DC current, it causes delay and phase-shifting problems, to solve these problems, this paper presents a real-time sliding window to extract the DC current instead of low-pass filter. At the same time, shows the principle of hybrid active power filter, and corresponding mathematical model is established. Finally, take a new composite control strategy. Simulation results show correctness of the detection and effectiveness of the new composite control strategy.
A critical overview on zero sequence component compensation in distorted and unbalanced three-phase four-wire systems
The generalized theory of instantaneous powers has been used in power system applications for compensation of instantaneous powers and harmonic cancellation. Nevertheless, this theory results practically desirable solution in three-phase three-wire systems. However, for a three-phase four-wire system, when the power system is unbalanced or distorted, then these definitions introduce unsatisfactory cancellation of the source zero sequence current. This paper analyzes and simulates this problem to show the issues related to the generalized theory of instantaneous powers. Further, complementary analytical discussions are suggested to remedy the raised problem. Finally, the improved definitions are simulated for a three-phase four-wire system that includes significant zero sequence current. Suggested complementary solutions are then compared with those of conventional generalized definitions, which confirm effectiveness of the proposed solutions in cancellation of zero sequence current of the source.
Modelling and Comparative Evaluation of Control Techniques Applied to a PWM Three-Phase Four-Wire Shunt Active Power Filter
Current harmonics, which are injected in the utility by nonlinear loads, cause major problems that tend to deteriorate the power quality at the mains. To reduce such harmonics, active power filters (APF) are commonly employed. In this paper, two multiple-loops control schemes for a shunt three-phase four-wire APF are considered. The APF is used to compensate the current distortion and the reactive power created by a typical 60 kW industrial load. The first control scheme is based on the use of hysteresis current controllers for the current wave shaping, whereas the second one employs linear PI regulators designed on the basis of a small-signal averaged model of the converter. Both control schemes are designed to ensure voltage regulation at the DC side of the filter, and current wave shaping at the AC side. The control systems are implemented numerically using Matlab/Simulink tool. The performance of the both control approaches are finally evaluated and compared through the obtained simulation results