Circuit modeling method and output current control method for dual-active-bridge-type micro-inverter

A circuit modeling method for a dual-active-bridge-type micro-inverter, comprising:

• equating the micro-inverter to a standard dual-active-bridge-type circuit by establishing an equivalent circuit model for the dual-active-bridge-type micro-inverter, thereby further establishing a large signal model and a small signal model for the micro-inverter, completing the circuit modeling of the dual-active-bridge-type micro-inverter;
• wherein:
• establishing an equivalent circuit model for the dual-active-bridge-type micro-inverter, comprising:
• constructing a DC source Voc, a DC source series resistor Rpv, a DC side bus capacitor Cbus, a controlled current source iac,in, an ideal transformer with a primary side to a secondary side turn ratio of 1:n, a controlled current source iac,out, a capacitor Cg, a filtering inductor Lg on a AC power grid side, an inductor winding resistor RL, and a DC pulsating source |vg|;
• the positive pole of the DC source Voc is connected with one end of the DC source series resistor Rpv, the other end of DC source series resistor Rpv is connected with the positive pole of the DC side bus capacitor Cbus, the positive pole of the DC side bus capacitor Cbus is simultaneously connected with the positive pole of the primary side of the ideal transformer, the negative pole of the primary side of the ideal transformer is connected with the negative pole of the DC source Voc, the positive pole of the secondary side of the ideal transformer is connected with the negative pole of the controlled current source iac,in, the negative pole of the secondary side of the ideal transformer is connected with the positive pole of the controlled current source iac,in and simultaneously connected with the negative pole of the controlled current source iac,out, the positive pole of the controlled current source iac,out is connected with the positive pole of the capacitor Cg and simultaneously connected with one end of the filtering inductor Lg on the AC power grid side, the other end of the inductor Lg on the AC power grid side is connected with one end of the inductor winding resistor RL, and the other end of the inductor winding resistor RL is connected with the positive pole of the DC pulsating source |vg|, and the negative pole of the DC pulsating source |vg| is connected with the negative pole of the capacitor Cg;
• the established large signal model for the micro-inverter is:
• a third-order average model {dot over (X)}=A1X+B1U;
• wherein X is a state variable of the large signal model;
• {dot over (X)} is a derivative of the state variable of the large signal model with respect to time;
• U is an input variable of the large signal model;
• A1 is a coefficient matrix of the state variable of the large signal model;
• B1 is a coefficient matrix of the input variable of the large signal model;
• the state variable X of the large signal model is:
• X=[vbus, vcg, io]T;
• the input variable U of the large signal model is:
• U=[vdc, vo]T;
• wherein vbus is an average value of the voltage of the DC side bus capacitor Cbus of the equivalent circuit during the switching period, vcg is an average value of the voltage of the capacitor Cg of the equivalent circuit during the switching period, io is an average value of the output current of the equivalent circuit during the switching period, vdc is an average value of the input voltage of the DC side of the equivalent circuit during the switching period, and vo is an average value of the output voltage of the equivalent circuit during the switching period;
• the established small signal model for the micro-inverter is:
• a third-order model {dot over (x)}=A2x+B2u;
• wherein x is a state variable of the small signal model;
• {dot over (x)} is a derivative of the state variable of the small signal model;
• u is an input variable of the small signal model;
• A2 is a coefficient matrix of the state variable of the small signal model;
• B1 is a coefficient matrix of the input variable of the small signal model;
• the state variable x of the small signal model is:
• x=[, , ]T;
• the input variable u of the small signal model is:
• u=[, , , ]T;
• wherein is a perturbation value of the voltage of the DC side bus capacitor Cbus of the equivalent circuit, is a perturbation value of the voltage of the capacitor Cg of the equivalent circuit, is a perturbation value of the output current of the equivalent circuit, is a perturbation value of the input voltage of the DC side of the equivalent circuit, is a perturbation value of the output voltage of the equivalent circuit, is a perturbation value of the internal phase shift angle, is a perturbation value of the external phase shift angle.