DG-IRMCK203 Datasheet, PDF (58/67 Pages) International Rectifier – Application Developer’s Guide

IRMCK203 Application Developer’s Guide
Appendix A Space Vector PWM Module
The Space Vector PWM generation module accepts modulation index commands and generates the appropriate gate
drive waveforms for each PWM cycle. This section describes the operation and configuration of the SVPWM
module.
SVPWM Basic Theory and Transfer Characteristics
A three-phase 2-level inverter with dc link configuration can have eight possible switching states, which generates
output voltage of the inverter. Each inverter switching state generates a voltage Space Vector (V1 to V6 active vectors,
V7 and V8 zero voltage vectors) in the Space Vector plane (Figure 21). The magnitude of each active vector (V1 to
V6) is 2/3 Vdc (dc bus voltage).
The Space Vector PWM (SVPWM) module inputs modulation index commands (U_Alpha and U_Beta) which are
orthogonal signals (Alpha and Beta) as shown in Figure 21. The gain characteristic of the SVPWM module is given in
Figure 22. The vertical axis of Figure 22 represents the normalized peak motor phase voltage (V/Vdc) and the
horizontal axis represents the normalized modulation index (M).
Where : M = Umag *Mod _ Scl *10^−4
Umag = (U _ Alpha ² + U _ Beta ² )
Mod _ Scl : Input scaling factor
(-32768 <= U_Alpha, U_Beta <= 32767)
(0 to 32767 range)
The inverter fundamental line-to-line Rms output voltage (Vline) can be approximated (linear range) by the following
equation:
Vline = Umag * Mod _ Scl *Vdc / 6 / 2²⁵
where dc bus voltage (Vdc) is in volts
V3
V2
sector 2
V_Beta
V
sector 3
V4
sector 1
V_Alpha
V1
U-phase
sector 4
sector 6
sector 5
V5
V6
2 zero vectors V7, V8
Figure 21. Space Vector Diagram
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