A novel modulation scheme for a modular multiphase multilevel converter in a power hardware-in-the-loop emulation system

This paper presents a novel modulation strategy for a Modular Multiphase Multilevel Converter especially for the usage in Power Hardware-in-the-Loop Emulation Systems. The proposed modulation scheme generates the required voltage time area by means of an integrator in a quasi continuous operation mode. Therefore, the fixed modulation period is disestablished to achieve a minimum response time of the emulation converter. The switching states of the parallel half-bridges are selected by a sorting algorithm, dependent on the instantaneous branch currents, to avoid saturation in the flux compensated chokes of the converter. The performance of the modulation scheme is verified at a three phase, seven level multilevel converter, with a PWM-frequency up to 120 kHz and an output power of more than 100 kW.