PV MICRO-INVERTERS WITH ROBUST OFF-GRID OPERATION

Systems and methods relating to control systems for DC/AC inverters that receive power from photovoltaic based renewable energy resources. When the DC/AC inverters are operated in on-grid mode, the DC/AC inverters and the DC/DC control system operate to provide on-grid functions such as maximum power point tracking (MPPT) and DC-bus voltage regulation. When in off-grid mode, the DC/AC inverter and the off-grid control system regulates the resulting AC voltage from the DC/AC inverter to be within a pre-set range. The off-grid control system is based on differential geometry and uses a Lie Group controller for setting a frequency reference signal. The frequency and current amplitude reference are used to generate a sinusoidal current reference signal which is then tracked by a current controller. The current controller controls the switches in the DC/AC inverter to regulate the AC voltage.