| With the nonlinear power electronic devices such as rectifier, inverter, switch power supply equipment widely used in grid applications, a large number of harmonic current is injected to the grid. As a result, the grid voltage and current waveforms are in distortion. The harmonic current not only brings a waste of energy, but also affects the safe operation of electrical equipment. The APF becomes an important mean to harmonic suppression and reactive power compensation. This paper choses shunt APF as a research object to study harmonic detection and control strategy, and puts forward a design of shunt active power filter based on PI + repetitive control.This paper firstly presents a introduction to the structure and working principle of APF, and then the mathematical model is deduced. The main algorithms of harmonic detection are Fourier, instantaneous reactive power theory, d-q-0 transformation. These harmonic detection algorithms all have good detection results. The detection of harmonic current is stable in a half AC cycle, t=0.02 s. The control methods of APF are the traditional hysteresis control, triangular wave comparison control, PI control and repetitive control, advantages and disadvantages are analysis. Because of limitation of PI control and repetitive control, parallel control of PI and repetitive control is proposed. The APF simulation model is built in the Matlab, the pure PI control, repetitive control and parallel control of PI and repetitive control are simulated. The simulation results verify the feasibility of this control method.Finally control methods proposed before are applied in the APF hardware platform. The THD of load current before compensation is 28.7%, and the 5th and 7th harmonics are very high. After the compensation of harmonic current, the THD drops to 3.6%. 5th harmonic drops from the original 2.2A to 0.2A. The compensation effect is obvious. Results have proved the effectiveness and practicability of the algorithm. |
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