Solar micro-inverters work based on Digital Signal Controller (DSCs) that boast powerful algorithms to provide the features of both off-grid and on-grid inverters, so that functions such as MPPT (Maximum Power Point Tracking), charge management, inversion, and connection with grid can be enabled on a single device. A micro-inverter is built with battery charge management, an inversion circuit and a relay.
Battery charge management includes a DC-DC module, and circuits for detection of input/output voltage and current. It provides MPPT and charge management functions under the control of a DSC. Inversion circuit is made up of four circuits: input filter circuit is implemented with filter capacitors which are used to reduce input voltage ripples; boost circuit includes a Schottky diode, an inductor and a DSC-driven MOSFET to boost a low DC voltage (usually 12-36V) provided by batteries to a high DC voltage; single-phase full-bridge inverter consists of 4 MOSFETs which are driven by a DSC to convert high-voltage DC power into 50-60Hz AC power; output filter circuit uses two inductors and a capacitor to eliminate harmonics of output voltage. Relay could be functioning either to supply power for AC loads or to lead current to power grid under the control of a DSC. When micro inverters are connected to AC loads such as home appliances and lights, relays can be switched on under any condition. But if inverters are connected to the power grid, relays should stay switched-off until a match is found on voltages and phases between the relays’ output end and power grid. Inverters can display operation status, input/output voltage and current. They also have keys for configuring necessary parameters to ensure proper operation.