Comparison of two modulation strategies for a three level inverter synchronous reluctance motor (SynRM) drive

Comprehensive Modulation Strategies for Synchronous Reluctance Motor Drives Used in Weak Grids

“…The SynRM equivalent circuit can be shown in Figure 1a,b [30][31][32]. The equations describing the operation of the SynRM can be written as follows [9,13,29]:…”

“…The well-known DPWM method is a possible solution when used in a high-modulation index field to reduce the switching times with one phase clamped to the DC-link bus. As explained in [10][11][12][13][14], according to the segment period for discontinuous modulation, DPWM can be divided into six classic types: 120° clamping (DPWMmax and DPWMmin), However, these factors do not occur simultaneously, and evaluating them in practical applications is challenging. For the above reasons, in the analysis and experiments presented in the following sections, the DC-link voltage cases are mainly divided into two levels: (a) expected voltage drop level-low voltage ranges from 500 V to 550 V, covering all factors to provide a sizeable DC-link voltage drop of approximately 7.4%-and (b) extreme voltage drop level-the worst DC-link voltage range considered was approximately 450 V-500 V for super-weak grid analysis.…”

“…The well-known DPWM method is a possible solution when used in a high-modulation index field to reduce the switching times with one phase clamped to the DC-link bus. As explained in [10][11][12][13][14], according to the segment period for discontinuous modulation, DPWM can be divided into six classic types: 120 • clamping (DPWM max and DPWM min ), 60 • clamping (DPWM0, DPWM1, and DPWM2), or 30 • clamping (DPWM3). Some studies [19][20][21][22][23] discussed advanced clamping DPWM (split-clamp DPWM), in which the 60 • clamping region is divided into two sub-clamping regions from DPWM0-2.…”

“…In the six-step operation mode, the voltage vectors can only move at the six vertices of the hexagon, as discussed in [8,9]. Other works have presented different discontinuous PWM (DPWM) strategies [10][11][12][13][14] that can be implemented by properly injecting zero-sequence voltage into the original modulation waveform. The modulation voltage waveform of one phase has one segment each of 120 • (DPWMmax, DPWMmin), 60 • (DPWM0, DPWM1, DPWM2), or 30 • (DPWM3) clamped to the positive or negative DC-link voltage during which no switching occurs in either inverter arm.…”