An Improved Modulation Strategy for the Active Voltage Clamping HERIC Inverter

The active voltage clamping HERIC (AVC-HERIC) inverter can be employed in PV applications due to its high-performance in terms of low leakage currents, high efficiency, and high power density. However, maintaining a high efficiency and good power quality under reactive power injection requires retrofitting the modulation strategies. This paper thus proposes an improved modulation method for the AVC-HERIC topology. The proposed modulation scheme mainly adopts two operation modes to enable the reactive power injection. Moreover, the two operation modes can be switched according to the polarity of the reference voltage. This maintains the efficiency as when the unipolar pulse width-modulation (PWM) strategy is adopted. Additionally, in the region of the minimum pulse width limitation (MPWL), an effective compensation strategy is also proposed in this paper to improve the power quality. Simulations and experiments are performed on a 4-kW AVC-HERIC system, and the results verify the effectiveness of the proposed modulation.