Suppression of DC-Link Voltage Oscillation Method for Capacitorless Control Based on Active Damping Technique

A capacitorless based drive system has the advantages of lower cost and longer lifetimes. However, a resonance phenomenon occurs when it is operated with the unbalance between grid input power and inverter output power. A high frequency resonance voltage is imposed on the dc-link capacitor. In order to suppress the voltage oscillation, a reliable method is the active damping technique. Conventional methods utilize the harmonic component of the dc-link current or voltage to compensate the currents or voltages in dq-axes. For current compensation based-methods, the compensated current is in either d-axis or q-axis not a vector component, which leads to the current commands are not optimal. For conventional voltage compensation based-methods, a large component of compensated voltage would cause a disturbance to current regulator seriously. This paper proposes a voltage vector compensation method which uses the information of limited dc-link voltage and currents to predict the modified voltages. The superiority of the proposed method was experimentally justified.