A Novel AC Side Four-Switch Power Decoupling Circuit for Single-Phase Inverter

In single-phase inverter, the output voltage and current are both sinusoidal quantities with angular frequency ω. Thus, the instantaneous output power oscillates at angular frequency 2ω, which cause secondly ripple power (SRP) in the inverter. Traditionally, the absorbing of SRP is relied on electrolytic capacitors (E-caps) which is short-life and unreliable. In comparison, the active power decoupling circuit (APDC) utilizing thin film capacitors to absorb SRP is superior to E-caps. To shorten the loop of the SRP, this paper proposed an ac-side decoupling scheme. Specifically, a four-switch APDC is designed and paralleled with the ac-side of inverter. By this way, the local decoupling of SRP could be implemented. Moreover, the pulse energy modulation (PEM) strategy is applied to four-switch APDC to enhance the decoupling effect and dynamic performance. In this way, the capacitance value of the system makes a great reduction. At last, the experimental results show that the decoupling topology proposed in this paper can replace the traditional 220μF large electrolytic capacitor only by using the film capacitor with a total capacitance of 50μF. In addition, the proposed PEM control strategy can effectively buffer the double frequency ripple and improve the stability of the system.