Method for improving efficiency of micro-inverter and dual-active-bridge-type micro-inverter

A method for improving the efficiency of a micro-inverter, characterized by comprising:

• performing power modulation mode switching of a dual-active-bridge-type micro-inverter, such that the power is bi-directionally transmitted from a DC side to an AC side and from the AC side to the DC side, thereby reducing an effective value of a secondary side current of a transformer;
• and
• according to a modulation mode switching characteristic of the dual-active-bridge-type micro-inverter within a power frequency period, performing hybrid optimization on a turn ratio of a primary side to a secondary side and a transformer leakage inductance of a high-frequency transformer of the dual-active-bridge-type micro-inverter,
• wherein performing power modulation mode switching of a dual-active-bridge-type micro-inverter, such that the power is bi-directionally transmitted from a DC side to an AC side and from the AC side to the DC side, thereby reducing an effective value of a secondary side current of a transformer comprises:
• determining an internal phase shift angle D1 and an external phase shift angle D2, the internal phase shift angle D1 is an angle between a negative rising edge of a square wave voltage generated by a primary side square wave generating circuit and a positive rising edge of the square wave voltage generated by the primary side square wave generating circuit;
• the external phase shift angle D2 is an angle between a fundamental wave of the square wave voltage generated by the primary side square wave generating circuit of the transformer and a fundamental wave of a square wave voltage generated by a secondary side square wave generating circuit of the transformer;
• directly controlling the primary side square wave generating circuit by using the internal phase shift angle D1 to generate a corresponding square wave voltage, controlling the secondary side square wave generating circuit by using the external phase shift angle D2 summed with an output of the current loop closed-loop control by an adder, to generate a corresponding square wave voltage, to realize the given transmission power of the micro-inverter;
• taking the internal phase shift angle D1 and the external phase shift angle D2 as two control degrees of freedom of the micro-inverter, according to the two control degrees of freedom of the micro-inverter, dividing the modulation mode of transmission power into mode one, mode two and mode three, and according to the instantaneous transmission power of the micro-inverter and the value of the internal phase shift angle D1, switching the micro-inverter between mode three and mode two.