Design conditions for space vector modulated three-phase converter to avoid instability

The analysis, design aspects and numerical results of a current controlled three-phase space vector modulated (SVM) voltage source converter (VSC) are presented. The aim of the current controller of VSC is to track the balanced three-phase sinusoidal reference currents. The current controller includes a complex saturation function in order to avoid overmodulation in the SVM. Due to this strong nonlinearity the study leads to rather unexpected system states. An approximate Poincare" map is derived using stroboscopic sampling with the modulation period of the SVM. Selecting eigenvalues of the system linearized around the desired fixed point is not sufficient to the proper operation. Other stable fixed points or limit cycles can appear. Chaotic states also can develop in the unstable region of the desired fixed point. The main objectives arc to develop the tools for describing the nonlinear behavior, for designing the digital PI controller and to present numerical results.