Indirect closed loop control of quasi-Z-source inverter for standalone solar PV-based energy conversion system

Abstract

Nowadays impedance source inverter (ZSI) offers an attractive solution to renewable energy sources with low output, can buck/boost the output voltage by utilising shoot-through pulses. The presence of right half plane zero in control transfer function makes the closed loop control complex, an undershoot is visible in the capacitor voltage. This paper presents an indirect control method of peak dc link voltage for a quasi-Z-source (qZS) inverter connected system. Small signal model for dc and ac sides are elaborated, optimum parameters for impedance network and controller are designed by analysing various frequency and time responses. The control methodology uses a single loop PI controller at dc side, decoupled feed forward control at ac side and parasitic resistances are considered for dynamic analysis. Results depicts a fast reference tracking, without compromising stability, harmonic attenuation, and transient response. A stable controller response validates the presented design and control methodology.