A comparative study on voltage-source control and current-source control of series active power filter

Series active power filters (SAPF) can effectively suppress the line current harmonics generated by voltage-type harmonics sources. Yet the performance differs much in different control approaches. Generally there are two kinds of typical control strategies: voltage-source control and current-source control. The conventional control is voltage-source control in which the SAPF is controlled as a voltage source, and works just like frequency-selective impedance. It presents zero impedance for the fundamental frequency and acts as a resistor with high resistance of K [Ω] for harmonics frequencies. In late 1990s, some publications reported a new control strategy as current-source control in which the SAPF is controlled as a sinusoidal current source in phase with the utility voltage and with the amplitude as load needs. It is claimed that the current-source control has the priority of better performance, easy to implement, less time delay in digital control system, and most of all, with no stability problem. However, it is quite amazing that how current-source control can achieve all these better performances with just same power stage as voltage-source control and what is the nature between these two control strategies. This paper extensively compared these two control strategies in the view of the whole system, and found that the two control strategies, which seem entirely different in appearance, have identical control structure and operation principles. Simulation and experimental results are illustrated to verify the theoretical analysis. What´s more, some previously confusing issues are discussed at the end to thoroughly express the author´s view on the operation principle of SAPF.