A Voltage Spike Suppression Strategy for Arm Multiplexing Alternate Arm Converter

The arm multiplexing alternate arm converter (AM-AAC) can reduce the number of submodule capacitors, but transient voltage spikes may appear at commutation instants when phase-shifted carrier pulse-width modulation (PSC-PWM) is used with a low submodule count. This paper analyzes the spike-generation mechanism from the discrete sampling behavior of symmetric regular sampling. The analysis shows that interleaved carrier phases produce nonuniform response delays among submodules, so the arm voltage follows a staircase transition rather than an ideal step change. After mirror folding by the commutation switches, this transition is coupled to the ac side as a voltage spike. Analytical expressions are derived for the spike duration and amplitude, revealing their dependence on the submodule number and phase-shift conduction angle. A suppression strategy is then proposed by shifting the carrier phase of the commutation switches so that commutation occurs near the midpoint of the spike duration. MATLAB R2024b simulations and RTDS hardware-in-the-loop experiments verify that the proposed method substantially reduces the spike amplitude without additional hardware, while PSC-PWM maintains lower output-current THD than nearest-level modulation in low-submodule AM-AAC applications.