Sector-Based Analytic Overmodulation Method

In this paper, an overmodulation (OVM) technique is proposed based on Fourier analysis. The OVM trajectory is a mixture of six arc segments of the inscribed circle and six vertices of the voltage hexagon. By adjusting the holding angle at each vertex, the modulation index is determined. The fundamental component is expressed as a function of the holding angle, and the linearity with the modulation index is obtained by the inverse relation. This algorithm guarantees seamless transitions from the space vector pulsewidth modulation to OVM and finally to the six-step. Apart from the variable voltage variable frequency control, the proposed algorithm works well with the interior permanent magnet synchronous motor current controller. By computer simulation and experimental evidence, the effectiveness is demonstrated.