Bus voltage secondary ripple suppression method and device

A bus voltage ripple suppression method for suppressing a ripple of a DC bus voltage of a two stage photovoltaic (PV) inverter structure having a Boost circuit, comprising:

• determining a current working mode of the Boost circuit, wherein the current working mode comprises one of a continuous current mode (CCM) and a discontinuous current mode (DCM);
• calculating an output compensation amount according to the determined current working mode of the Boost circuit;
• superimposing the calculated output compensation amount on a control output amount of the Boost circuit;
• and
• controlling the Boost circuit through the control output amount superimposed with the output compensation amount,
• wherein determining the current working mode of the Boost circuit comprises:
• determining that the Boost circuit is in the CCM mode when the direct current (DC) bus voltage (Udc) and a DC input PV voltage (Upv) of the Boost circuit meet:
• Udc*(1−D0=Upv;
• determining that the Boost circuit is in the DCM mode when the DC bus voltage (Udc) and the DC input PV voltage (Upv) of the Boost circuit meet:
• Udc*(1−D0)>Upv;
• wherein D0 is a duty ratio of Pulse Width Modulation (PWM), and
• wherein calculating the output compensation amount according to the current working mode of the Boost circuit comprises:
• obtaining respectively a DC amount Udc of the DC bus voltage when there is no voltage fluctuation on a DC bus at an output of the Boost circuit and the DC bus voltage Udc=Udc + when there is voltage fluctuation on the DC bus;
• obtaining a PWM compensation duty ratio from the obtained DC amount Udc of the DC bus voltage when there is no voltage fluctuation on the DC bus at an output of the Boost circuit, and the obtained DC bus voltage Udc when there is voltage fluctuation on the DC bus;
• and
• using the PWM compensation duty ratio as an output compensation amount.