Decoupled modulation techniques for a four-level five-phase open-end winding drive

Abstract

AbstractThe paper studies pulse width modulation (PWM) techniques for a five-phase multilevel open-end winding drive with two inverters supplied with unequal dc-link voltages, which are in the ratio 2:1. It is shown in the paper that application of in-phase disposition modulation (PD-PWM), often used in multiphase multilevel converters, results in overcharging of the capacitor in the dc-link of the converter intended to operate at the lower dc voltage. The voltage space vector combinations which lead to the overcharging are identified and two decoupled modulation techniques which do not activate the troublesome vector combinations are proposed. The performance of the developed modulation techniques is investigated using simulations and an experimental prototype, and the results are presented in the paper.

Decoupled PWM Control of a Dual-Inverter Four-Level Five-Phase Drive

“…Secondly, this solution leads to a more complex structure with an increased component count, which is in contradiction with the primary motivation for the OeW drive development. This paper builds on the work presented in [20] where a decoupled SV PWM algorithm is developed, which considers the four-level drive as two individual two-level inverters rather than a single four-level structure. Two decoupled modulation strategies, based on the unequal reference sharing between the modulators of the inverters (so called URS1 and URS2) are discussed in [20].…”

“…This paper builds on the work presented in [20] where a decoupled SV PWM algorithm is developed, which considers the four-level drive as two individual two-level inverters rather than a single four-level structure. Two decoupled modulation strategies, based on the unequal reference sharing between the modulators of the inverters (so called URS1 and URS2) are discussed in [20]. It is shown that the decoupled SV PWM methods naturally avoid the switching states that lead to the dc-link capacitor overcharging.…”

“…Contrary to the coupled CB PD PWM case, decoupled modulation algorithm for the four-level drive relies on only two carrier signals and each of them corresponds to one two-level inverter. The main contributions of the paper are:  Proposed CB PWM is simpler to implement, when compared to the SV PWM of [20]. The developed socalled unequal reference sharing (URS) modulation methods are compared with the proportional reference sharing (PRS), proposed in [11].…”

“…Results show that URS is superior in terms of total harmonic distortion performance.  A novel concept of open-end winding drive modelling is introduced, which leads to better understanding of the dc-link voltage stability, when compared to methods in [19,20]. The paper is organised as follows.…”

“…For the sake of clarity, Section II provides a short description of the topology under analysis. More details can be found in [14][15][16][17]20]. Unequal reference sharing algorithms (URS1 and URS2), based on CB PWM are discussed in Section III, and compared with the method introduced in [11].…”