High-power density, single-phase cascaded h-bridge rectifier, control method, and control system

A control system of high-power density, single-phase cascaded H-bridge rectifier, the high-power density, single-phase cascaded H-bridge rectifier comprising:

• an alternating current (AC) grid-side filter inductor and at least two cascaded power conversion units, wherein each power conversion unit comprises an H-bridge power unit, a decoupling unit, and a direct current (DC)-side equivalent load that are connected in parallel;
• and each decoupling unit is an independent buck-type active power decoupling circuit, and the decoupling unit is configured to buffer secondary ripple power, to reduce a capacity of a DC bus capacitor, wherein the control system comprises:
• a DC bus voltage control module, configured to control a DC bus voltage of each power conversion unit in a closed-loop manner, to generate an operation voltage of the each power conversion unit and a total voltage of the H-bridge rectifier;
• a unit-power-factor rectification module, configured to use the total voltage of the H-bridge rectifier as an outer-loop given value, and control a grid-side current in a closed-loop manner, to generate an average modulation signal factor;
• a voltage equalization module, configured to respectively compare an average value of the total voltage of the system with each power unit voltage, and then multiply a per-unit difference value by a grid-side voltage phase to obtain a result as a deviation modulation signal factor, to implement both voltage equalization and suppression of secondary pulsation of the DC bus voltage;
• a modulation-signal generation module, configured to superimpose the deviation modulation signal factor of the each power conversion unit with the average modulation signal factor, to generate a final modulation signal of the each power conversion unit;
• a drive-signal generation module, configured to compare the final modulation signal of the each power conversion unit with a carrier, and generate a drive signal of a switch tube of the each power conversion unit by using a single-pole double-frequency phase-shifted carrier modulation algorithm;
• and
• an active-power-decoupling control module, configured to extract a secondary ripple current on the DC bus of the each power conversion unit in real time, and calculate a duty cycle of a power switch tube in the decoupling unit online, to transfer secondary ripple power on the DC bus to the decoupling unit.