Multilevel inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters. Among various modulation techniques for a multilevel inverter, the space vector pulsewidth modulation (SVPWM) is widely used. However, the implementation of the SVPWM for a multilevel inverter is complicated. The complexity is due to the difficulty in determining the location of the reference vector, the calculation of on-times, and the determination and selection of switching states. This paper proposes a general SVPWM algorithm for multilevel inverters based on standard two-level SVPWM. Since the proposed multilevel SVPWM method uses two-level modulation to calculate the on-times, the computation of on-times for an n-level inverter becomes easier. The proposed method uses a simple mapping to achieve the SVPWM for a multilevel inverter. A general n-level implementation is explained, and experimental results are given for three-level and five-level inverters.Index Terms-Multilevel inverter, neutral point clamped (NPC), space vector pulsewidth modulation (SVPWM), switching state, two-level inverter.

Multilevel inverters are being increasingly used in high power industrial drive applications. There are many modulation techniques available for a multilevel inverter but Space Vector PWM is commonly used. When the inverter operates in the sinusoidal mode of Space Vector PWM, the DC link voltage of the inverter is not fully utilized. A suitable overmodulation scheme is required to address this problem. Another problem associated with the Space Vector PWM of multilevel inverters is, when the level of the inverter increases, the implementation of space vector modulation becomes cumbersome due to the difficulty in determining the location of reference vector, calculation of on-times and large number of switching states. This paper proposes a simple space vector PWM algorithm, which (a) can cover sinusoidal mode and overmodulation mode (b) can easily determine the location of reference vector (c) can easily calculate the on-times (d) can be used for any level of inverter. In the proposed scheme, the on-time calculations are based on a standard two-level Space Vector PWM. The proposed scheme is explained for a 5-level cascaded H-bridge inverter with operation in sinusoidal mode, overmodulation mode I, and overmodulation mode II. Experimental results are provided to prove the viability of the scheme. 0-7803-8987-5/05/$20.00 ©2005 IEEE.

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