Control of electrical excited synchronous machine at low switching frequency

The operation of the PWM converter should be kept at low switching frequency so as to restrain the dynamic losses of the three-level converter and improve its output power. However, traditional control methods are no longer suitable for this condition with the resulting increasing output harmonic distortion and reduction of dynamic performance. To overcome the above problems, a novel complex matrix model of the electrically excited synchronous machine combining the complex vector and matrix was established in this paper. And then, a hybrid observer was proposed to identify the instantaneous fundamental component of the stator current. With the consideration of the delay introduced by the switching device and the time-discrete sampling, a novel current control system was designed based on the control theory. MATLAB simulation and DSP experimental results verify the effectiveness of the proposed control method.