Multi-cell current source inverter drive system with equivalent DC machine control

Abstract Modular electric drive systems have attracted increasing attention due to their scalability, fault tolerance, and suitability for integrated high-power-density applications. Most existing modular drive concepts are based on the series stacking of low-voltage voltage-source inverters (VSIs), where each machine segment is supplied by an individual three-phase inverter connected to a common high-voltage DC-link. While this approach is well established, it requires per-segment current measurement and voltage balancing of DC-links to avoid stability issues. Series-connected current-source inverter (CSI) drive systems offer an attractive alternative, as the output current is inherently imposed and individual segment current control and voltage balancing are avoided. However, conventional series stacking of CSIs results in a high number of power semiconductor devices, limiting practical implementation with modern wide-bandgap technologies. Building on a recently introduced multi-cell current-source inverter architecture (mCSI), this paper presents and experimentally verifies a modular electric drive system supplying a segmented permanent-magnet synchronous machine. The multi-cell approach provides functionality equivalent to conventional series-connected CSI drives while requiring close to half the number of power semiconductor devices. By operating the drive with fixed modulation parameters, the electromechanical behavior of the segmented machine can be consistently interpreted using an equivalent DC machine representation, enabling torque and speed control solely via the DC link current of a single front-end converter. A compact DC-side model is developed to describe the steady-state and transient behavior of the resulting drive system. The proposed modeling and control framework is validated through simulations and experimental measurements obtained from a laboratory demonstrator comprising a multi-cell current-source inverter and a segmented PMSM with two independent three-phase stator segments. The results confirm the predicted equivalent DC machine behavior and demonstrate the feasibility of the proposed approach as a scalable and hardware-efficient solution for future integrated electric drive applications.