An Improved Current Control Strategy Based on Particle Swarm Optimization and Steady-State Error Correction for SAPF

Shunt active power filter (SAPF) is widely used for compensating harmonic current produced by nonlinear loads. As one of the critical technologies, the current control strategy has an important influence on the compensation precision and dynamic response performance. In this paper, the essential of the current-limiting demands for the comprehensive protection of SAPF are revealed, namely the limiting control objects: first, rms of the compensation current (mainly for the overheat protection of IGBTs and inductors), second, the instantaneous wave of compensating current (mainly for the accurate current control and IGBT I
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specification), and third, the instantaneous wave of PWM-VSC modulation voltage (for the need of liner close-loop control). To avoid the over-current fault and over-modulation fault of SAPF, this paper proposes an improved current-limiting scheme based on particle swarm optimization (PSO) to achieve the two optimization targets: the minimization THD for the grid-side current, and the maximization utilization ratio for the capacity of SAPF. The main advantage lies on the optimum limiting ratios of each harmonic order calculated in real time, respectively, to achieve the flexible and liner limiting control. In addition, taking the control structure consisting of selective harmonic detection under the multiple rotating reference frame and the single PI current loop, for example, this paper gives the method for steady-state error correction qualitatively and quantitatively, which employs the method based on the frequency response characteristics analysis. Finally, simulation and experimental results verify the effectiveness of the proposed strategy.