Qingbo Guo

Design and implementation of a loss optimization control for electric vehicle in-wheel permanent-magnet synchronous motor direct drive system

As a main driving force of electric vehicles (EVs), the losses of in-wheel permanent-magnet synchronous motor (PMSM) direct drive system can seriously affect the energy consumption of EVs. This paper proposes a loss optimization control strategy for in-wheel PMSM direct drive system of EVs which optimizes the losses of both the PMSM and the inverter. The proposed method adjusts the copper losses and iron losses by identifying the optimal flux-weakening current, which results in the PMSM achieving the lower losses in the whole operational range. Moreover there are strongly nonlinear characteristics for the power devices, this paper creates a nonlinear loss model for three-phase half-bridge inverters to obtain accurate inverter losses under space vector pulse width modulation (SVPWM). Based on the inverter loss model and double Fourier integral analysis theory, the PWM frequency is optimized by the control strategy in order to maximize the inverter efficiency without affecting the operational stability of the drive. The proposed loss optimization control strategy can quickly find the optimum flux-weakening current and PWM frequency, and as a result, significantly broaden the high efficiency area of the PMSM direct drive system. The effects of the aforementioned strategy are verified by both theoretical analysis and experimental results.

Design and Implementation of a Loss Optimization Control for Electric Vehicle In-Wheel Permanent-Magnet Synchronous Motor Direct Drive System☆

Abstract As a main driving force of electric vehicles (EVs), the loss of in-wheel permanent-magnet synchronous motor (PMSM) direct drive system can seriously affect the energy consumption of EVs. This paper proposes a loss optimization control strategy for EV in-wheel PMSM direct drive system which can optimize both the loss of PMSM and loss of inverter. The proposed method adjusts the copper loss and iron loss by optimal flux-weakening current, and as a result the PMSM achieve the lower loss in the whole operation range. According to the speed, the PWM frequency is optimized by the proposed control strategy, which can acquire high efficiency of inverter and not affect the stability of the PMSM system in the each operation condition. The optimum flux-weakening current and PWM frequency can be quickly found, and optimal effects of energy loss are verified by theoretical analysis and experimental results.

High-Bandwidth and Strong Robust Current Regulation for PMLSM Drives Considering Thrust Ripple

This paper presents a high-performance current controller for the permanent-magnet linear synchronous motor considering the bandwidth and disturbances caused by the parameter variation and thrust ripple. First, an improved predictive current control (PCC) scheme based on the discretized model is proposed to increase the current control bandwidth. Besides the time-delay issue, it is noteworthy that the parameter variation in the PCC method can degrade the steady-state response. Through utilizing the information of first two sampling periods, the proposed PCC strategy can overcome such two issues at the same time. Second, a new discrete-time linearization observer is designed to estimate the thrust ripple. Then, the ripple can be suppressed by injecting the estimated value into the control system. Meanwhile, the stability analysis is given by the Lyapunov stability theory. A precise test platform based on the aerostatic guideway is established, and experimental results are shown to demonstrate the effectiveness and correctness of the proposed scheme.

An improved predictive current control for PMLSM considering parameter variation

For the model-based control strategy, the predictive current control (PCC) requires the full knowledge of the motor parameters, which reduces the system robustness. This paper presents an optimal PCC for the permanent magnet linear synchronous motor (PMLSM). Through the information of first two switching periods, the parameter variation issue can be eliminated without impacting the performance of the current loop. The simulation and experimental results are shown to prove the correctness and effectiveness of the proposed scheme.

Efficiency optimization control of permanent magnet synchronous motor system with SiC MOSFETs for electric vehicles

As the permanent magnet synchronous motor (PMSM) system is the key part of power system in electric vehicles (EVs), the efficiency of PMSM system has great influence on the energy consumption of EVs. To increase the endurance mileage of EVs in one charge, it is important to improve the system efficiency of PMSM drive system. This paper proposes a novel analytical nonlinear loss model for PMSM system which can calculate motor loss and inverter loss together. The PMSM loss can be calculated by the analytical model which can exactly predict copper loss and iron loss together. The nonlinear switch characteristics and conduction characteristics of power devices can be fitted by the nonlinear model, by which the accurate inverter loss is acquired in a fast and simple way. This paper applied double Fourier integral analysis to calculate the harmonic current caused by the PWM output voltage of inverter in an analytic method, by which the system stability is analyzed. Based on the nonlinear system loss model, this paper proposes an efficiency optimization control strategy which can significantly increase the system efficiency without serious effect on the system stability in the whole operation condition of PMSM system for EVs. Both analytical and experimental results prove that efficiency optimization control can decrease the system loss and improve the system efficiency of PMSM system.

Efficiency Optimization Control of Permanent-Magnet Synchronous Machines for Electric Vehicle Traction Systems

This paper investigates a method to increase the energy economy of motors for an electric vehicle (EV) traction system. The low torque region of an EV motor is frequently used in everyday urban driving. Pulse-width modulation (PWM) carrier harmonic loss accounts for a high percentage of total loss for EV motors in this region. This paper reveals the relationship between fundamental and harmonic iron current for a permanent magnet synchronous motor (PMSM) by double Fourier integral analysis and builds the global loss model of PMSM which considers about both fundamental and harmonic loss. Based on the global loss model, an efficiency optimization control strategy is proposed in this paper, which can achieve the maximum efficiency by adjusting the flux-weakening current to the optimum value in the whole operation range for EV. Comparison among different control algorithms is drawn from both analytical and experimental results, from which the effectiveness of efficiency optimization control is verified.

Analysis and Modeling of Air-Core Monopole Linear Motor for Nanopositioning System

In the ultra-precision system, the multi-axis servo system is composed of air-core monopole linear motors (AMLM) for achieving nanopositioning. In the AMLM system, the thrust varies according to the changes of the relative position of motors primary and secondary. In this paper, the concept of thrust stiffness is proposed in order to illustrate the phenomenon of varieties of thrust according to changes in position. By using the surface charge model, the air-gap magnetic flux density of AMLM is predicted. Based on this prediction, the whole windings thrust, including straight and corner segments of winding, is calculated. Then, this winding thrust model is simplified to replace the original complicated analytical model. The accuracy of the simplified model is verified by the corresponding experimental tests. Thus, the thrust stiffness simplification model can be used in the feedforward compensation model in the control system of AMLM and efficiently decrease the calculation time of DSP.