PWM Carrier Displacement in Multi-N-Phase Drives: An Additional Degree of Freedom to Reduce the DC-Link Stress

Abstract

Abstract:The paper presents a particular Pulse Width Modulation (PWM) strategy to reduce the (Direct Current) DC-link capacitor stress for multi-n-phase drives. A multi-n-phase drive is composed of multiple independent systems of n inverter supplying a multi-n-phase electric machine. The paper focused on the investigation of the best phase shifting between carriers for a triple-3-phase drive compared to the 3-phase counterpart in order to reduce the capacitor bench design point. Simulation and experimental results show as the control technique proposed is able to reduce the value of the DC-link capacitor current in any operating condition including fault case. In this sense, the PWM carrier displacement appears like an additional degree of freedom that can be exploited in multi-n-phase drives but also in multi-motor application.

Reducing root‐mean‐square current stress on the DC link capacitor of a five‐phase electric drive through multiple carrier pulse‐width modulation technique

“…The DC-link current drawn by the inverter is composed of a DC value and high-frequency ac components. It is assumed that the DC source supplies all the DC components and the DC-link capacitor provides the ac component [17]. The ac component is thus calculated from the simulated DC link current and assigned as the capacitor current.…”

“…The reduces as the number of phases increase [10]. Additionally, in multiphase drives that use more than one converter, an additional degree of freedom can be exploited by using interleaved carriers [17]. In multi‐3‐phase cases, one PWM carrier is used for each inverter in order to generate PWM pulses, and a specific angle of phase shift between carriers can be found to minimise the DC link stress on the common DC bus.…”

“…A complete analysis of the technique has also been offered for three‐phase machine supplied by three inverters and for a triple‐3‐phase machine supplied by three inverters [15]. In [17], the research is related to the investigation of the best angle of shifting between carriers in order to reduce the DC link RMS current in triple‐3‐phase drives. The same technique can be introduced in order to reduce the harmonic distortion and power losses [18, 19] or to improve the quality of the line‐to‐line output voltages [20].…”

New Modulation Technique to Mitigate Common Mode Voltage Effects in Star-Connected Five-Phase AC Drives

“…AC electric drives are used in a wide variety of industrial applications such as in compressors [1], in electric vehicle propulsion systems [2,3] and in more electric aircraft (MEA) [4], among others. Although three-phase systems dominate the AC drive market, multiphase solutions are gaining popularity [5][6][7]. Multiphase systems are preferable for applications where high fault tolerance is required [8], such as for MEA applications, where electromechanical actuators (EMA) for control surfaces, fuel pumps, landing gears, environmental control systems and starter-generators need to be operated [9][10][11].…”

Low torque ripple tooth coil windings multi‐3‐phase machines: design considerations and validation

“…Multiphase solutions offer the possibility to reduce the stator phase current while maintaining the same voltage per phase and strongly reducing the DC‐link ripple current [4, 5]. In addition, the use of multiphase drives let available the exploitation of additional degree of freedom that can be used to improve the torque in fault operation or to improve the performance of the converter [7, 8].…”