Active PWM rectifier has become a popular choice in recent years. Compared with passive rectifiers, active rectifier can bring more benefits such as regulated dc link voltage, adjustable power factor and lower harmonics on ac side. Especially in a system with a generator as AC power source, active rectifier can significantly reduce the power loss in the generator caused by harmonic current. Since generator and active rectifier always work together and can be controlled simultaneously, it would be very desirable to develop a unified control to improve the system performance and reduce the need for additional passive components.
The paper proposes a unified control strategy for permanent magnet generator (PMG) and rectifier. The dynamic d-q model is used to cancel the time varying inductances and additional decoupling terms are used to minimize the damper windings' influences. A state observer and a PLL-based tracking controller provide a fast and accurate speed and rotor position estimation without sensors. With the control strategy, both the DC link voltage and generator power factor can be controlled effectively.
Fig. 1. Power stage and control circuit.
Fig. 2. Permanent magnet generator.