Cooperative Control of Two Single-Phase Full-Bridge Structures Composed of Master and Damping Inverter for Output Voltage Stabilization

In a stand-alone inverter, a high-quality sinusoidal output of a constant voltage and constant frequency must be supplied to the load regardless of the load condition. Therefore, the THD of the output voltage in steady-state should be low and the ability to recover from the transient period needs to be fast for the load variations. However, when the inverter employs an LC filter at the output stage, a damping technique is required to suppress voltage oscillations due to resonance when the load changes. This paper proposes a damping control method to stabilize the output voltage using cooperative control of two single-phase inverters connected in parallel. The Master inverter controls the output voltage, and the Damping inverter controls the output current to support output voltage damping and power capacity. Each inverter output stage consists of a lossless filter with no damping resistor to prevent efficiency degradation and robust against system parameter changes. The output voltage distortion is less than the conventional method, regardless of loads and load variations. We carried out PSIM simulations and experiments to verify the superiority of the proposed approach.