Proportional Hysteresis Band Control for DC Voltage Stability of Three-Phase Single-Stage PV Systems

Ensuring the stability of DC-link voltage in grid-connected photovoltaic (PV) systems plays a critical role in their reliable and continuous operation. DC voltage fluctuation and, in the worst case, DC voltage collapse will dramatically hamper real and reactive power delivery to the grid. This is more the case in single-stage inverters with no DC-DC boost stage, and the DC voltage has a varying nature. This paper proposes a new control approach for ensuring DC-link voltage stability in single-stage PV systems. The proposed control strategy is based on an adaptive hysteresis band controller (HBC), supplementing the conventional control blocks. This strategy offers the capability to prevent fast discharge of DC-link capacitor and keeps it within acceptable limits by quickly modifying phase shift applied to inverter PWM through quick calculations. Results show that the approach greatly improves PV system performance, in various operating modes. The proposed control scheme is implemented in the real-time simulator, OPAL-RT, OP5600 to verify its applicability and effectiveness in real time.