Insertion of dead time in space vector pulse width modulation (SVPWM) causes phase voltage and current distortion or even zero-current clamping phenomenon, degrading the control performance of ac induction motor. In addition, analysis of distortion becomes more complicated due to the existence of parasitic capacitance in power switching device of voltage source inverter (VSI). This paper tries to make clear that how the parasitic capacitance influences VSI's output independently. First, an equivalent circuit of VSI containing parasitic capacitance is constructed. On that basis, mathematical expression of phase voltage distortion is derived from Kirchhoff's voltage law, Kirchhoff's current law, and charge and discharge characteristics of capacitance. Moreover, through the division of multiple zero-crossing regions in one phase current period, the difficulty of obtaining specific phase voltage error expressions is overcome. Second, to figure out the effect of parasitic capacitance, it is theoretically discussed in detail that how parasitic capacitances of different values affect phase voltage, current distortion, and zero-current clamping phenomenon. At last, simulations and experiments are carried out in which VSI with different parasitic capacitances is constructed by paralleling additional capacitors and with phase voltage feedback methods, the theoretical analysis can be verified.

The insertion of dead-time will lead to the distortion of output waveforms, which seriously affects the characteristics of the AC induction motor (ACIM) control system. In order to reduce the output distortion of three-level T-type inverters caused by dead-time insertion, an online feedback dead-time compensation method is developed. In this method, the compensation time is obtained and further corrected by online feedback of duty cycle. Meanwhile, Current polarity judgment is accurately realized by sampling the neutral point potential (NP) and three phase output terminal voltage potentials. In addition, this paper takes the neutral point potential fluctuation into account to approximate the true situation. The developed method can be applied to both open-loop and closed-loop motor drive systems. To verify the effectiveness of the method, essential simulation and experiments are carried out. Compared with the traditional methods, the developed method can prominently reduce the output waveform distortion. Simulation results emphasize that the proposed scheme can significantly improve the performance of three-level inverters, and the identical conclusion is obtained on 210V/2.24kW motor platform.

Electric machine emulator (EME) system is developed for power electronics test. The accuracy of emulator, especially the accuracy of motor model is of vital importance in this system. The traditional lumped parameter permanent-magnet synchronous motor (PMSM) model ignores the nonlinearity. The finite element analysis (FEA) model and magnetic circuit analysis (MEC) are not suitable for EME real-time system. In this paper, we proposed an improved distributed parameter PMSM modeling method which integrates the magnetic saturation, the spatial harmonics and cross-coupling in a mathematical expression. The method reconstructs d-q axis current versus flux linkage and electric angular, rederives the electromagnetic torque, and simplifies the realization schematic. It should be emphasized that the model can be applied on real-time running system. With these improvements, the proposed model occupies much less RAM space compared with look-up table method. The model can mimic the harmonics and hold the merits of high accuracy and high running speed. To validate the accuracy of the proposed method, the simulations and experiments on field program gate array (FPGA) is carried out. Sufficient comparison among three models is implemented. The results validate the accuracy of the proposed model.

An electric machine emulator (EME) system plays a fundamental role in design and validation of hardware and software for power electronic converters and electric drives. In this paper, a desktop digital signal processor (DSP)-based EME is developed for power converters function test. The principle of EME is demonstrated with mathematical derivation. Since the instantaneous phase voltage is either power supply voltage or ground, high-rated voltage sensors are not suitable for DSP-based EME to obtain the average voltage in a pulse-width modulation cycle. To accurately acquiring phase voltages, a method which reconstructs the phase voltage considering the amplitude and duty cycle error is proposed. Voltage drops, dead time, propagation delay, parasitic rising and falling time delay are all considered in reconstructed voltages based on voltage-second balance theory. This is accomplished without any assistant physical circuits. Based on the reconstructed phase voltages, reference current is derived in motor model by using second order Runge-Kutta method. Factors affecting phase voltage accuracy are verified by simulations step by step. The simulation and experimental results support the validity of the proposed method.

During a steering manoeuvre in a ground vehicle, both yaw motion and roll motion can occur simultaneously, and their dynamics can be coupled, as the roll motion is generalized directly from the tires’ lateral force under steering. Hence, it is of significance to analyze them as an integrated plant in the vehicle steering stability control problem. Furthermore, the actuator saturation of yaw control cannot be neglected, as vehicles often steer at a high velocity or on low-friction roads. In this paper, an integrated steering dynamics model is established considering the coupling between the roll motion and lateral motion, then a novel nonlinear adaptive controller is proposed to stabilize the steering motion considering the actuator saturation of yaw motion control. Simulation results indicate that the designed integrated controller is effective in improving the performance of both the yaw rate tracking error and ride comfort taking into account vehicle parameter uncertainties and actuator saturation; the steering stability of ground vehicles can consequently be guaranteed.