Full-Speed Control of A Novel Variable Speed Drive Using Four-level Hybrid Clamped Converter

The four-level hybrid clamped converter (4L-HCC) is emerging as a new multilevel topology for medium/high-voltage motor variable speed drives. However, the internal capacitor voltage has unstable issues at extra low frequencies, limiting the 4L-HCC's application. This paper presents an integrated control scheme of the 4L-HCC and an electrical machine. Compared with the traditional PWM method, the proposed method can effectively suppress the excessive voltage ripples at low speed. The proposed control has features of easy implementation, accurate/fast current and torque response, and strong capacitor voltage balancing capability. Four-quadrant operation with high constant torque current is realized. Simulated and experimental results are used to validate the effectiveness of the proposed integrated method.