H-bridge-based single-phase applications have second-order harmonics on the dc-link voltage. Conventionally, the second-order harmonics are filtered by bulky dc capacitors to maintain the constant dc-link voltage, which results in poor power density and low reliability. However, in applications, such as the solid-state variable capacitor (SSVC), the constant dc-link voltage is unnecessary since the dc link is disconnected from the load or source. This article proposes a dc capacitor-less SSVC, which removes the dc capacitors from the topology. The dc voltage is supported by the ac-side voltage directly. Only a 0.03 per unit (p.u.) capacitor is needed to filter the switching-frequency harmonics. This enables the proposed SSVC to use the snubber capacitors to achieve the function of the 0.03-p.u. filtering capacitor. Other capacitors can be removed from the dc-link busbar. The modulation, modeling, and control strategy of the proposed dc capacitor-less SSVC are provided in this article. The proposed dc capacitor-less SSVC is validated by the experiment.

中文翻译：

---

无直流电容器的固态可变电容器

基于 H 桥的单相应用在直流母线电压上有二次谐波。传统上，二次谐波由体积庞大的直流电容器过滤以保持恒定的直流链路电压，这导致功率密度差和可靠性低。然而，在固态可变电容器 (SSVC) 等应用中，由于直流链路与负载或电源断开，因此不需要恒定的直流链路电压。本文提出了一种无直流电容器的 SSVC，它从拓扑中去除了直流电容器。直流电压由交流侧电压直接支持。只需要一个 0.03 个每单位 (pu) 的电容器来过滤开关频率谐波。这使得提议的 SSVC 能够使用缓冲电容器来实现 0.03-pu 滤波电容器的功能。其他电容器可以从直流母线母排上移除。本文提供了所提出的直流无电容器 SSVC 的调制、建模和控制策略。所提出的无直流电容器 SSVC 已通过实验得到验证。