A Novel Control Strategy For Inverters With Capacitive Equivalent Output Impedance

In low frequency situation, most of inverters are inductive (what is called L-inverter). While in this paper, a novel control method is proposed to change the output impedance of the inverter become capacitive in both low frequency and high frequency (what is called C-inverter). The proposed control method includes splitting capacitor of the LCL filter from one to two and using the current between the two splitting capacitors as the feedback current through an integrator, which is deem as a virtual impedance to constitute control loops. The splitting of the capacitor can reduce the system from the third-order system to the first-order, which would make it to be controlled easier. Moreover, the feedback current through the virtual impedance could change the output impedance of the inverter to achieve capacitive. And simulation results has been provided to demonstrate the excellent performance of the capacitive inverter with the improved LCL filter. It have been shown that the inverter which is capacitive have excellent output characters. In short, this novel control method combine the hardware way and the software way to reduce the constrain on capacitive output to change the output impedance of the inverter.