The present disclosure provides a high-power density, single-phase cascaded H-bridge rectifier, a control method, and a control system. The high-power density, single-phase cascaded H-bridge rectifier includes: an alternating current (AC) grid-side filter inductor and at least two cascaded power conversion units, where each power conversion unit includes 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.