Maximum Efficiency per Torque Control of Permanent-Magnet Synchronous Machines

Abstract

High-efficiency permanent-magnet synchronous machine (PMSM) drive systems need not only optimally designed motors but also efficiency-oriented control strategies. However, the existing control strategies only focus on partial loss optimization. This paper proposes a novel analytic loss model of PMSM in either sine-wave pulse-width modulation (SPWM) or space vector pulse width modulation (SVPWM) which can take into account both the fundamental loss and harmonic loss. The fundamental loss is divided into fundamental copper loss and fundamental iron loss which is estimated by the average flux density in the stator tooth and yoke. In addition, the harmonic loss is obtained from the Bertotti iron loss formula by the harmonic voltages of the three-phase inverter in either SPWM or SVPWM which are calculated by double Fourier integral analysis. Based on the analytic loss model, this paper proposes a maximum efficiency per torque (MEPT) control strategy which can minimize the electromagnetic loss of PMSM in the whole operation range. As the loss model of PMSM is too complicated to obtain the analytical solution of optimal loss, a golden section method is applied to achieve the optimal operation point accurately, which can make PMSM work at maximum efficiency. The optimized results between SPWM and SVPWM show that the MEPT in SVPWM has a better effect on the optimization performance. Both the theory analysis and experiment results show that the MEPT control can significantly improve the efficiency performance of the PMSM in each operation condition with a satisfied dynamic performance.

Analysis of Core Loss of Permanent Magnet Synchronous Machine for Vehicle Applications under Different Operating Conditions

“…When the motor adopted MTPA control, the internal magnetic saturation of the stator was relatively high, and the phase current obtained was larger than the phase current without considering the magnetic saturation. In weak field control, the magnetic saturation was low, and the phase current was smaller than the phase current without considering the effect of magnetic saturation [15][16][17][18][19][20][21][22][23]. The A-phase current shown in Figure 2 was Fourier decomposed to get its harmonic amplitudes, as shown in Figure 3.…”

Experimental Study for the Assessment of the Measurement Uncertainty Associated with Electric Powertrain Efficiency Using the Back-to-Back Direct Method

“…Analysis and estimation of the power loss and efficiency of the drivetrain are of practical significance in this matter [3]. As an example, the drive components in the system simulation tools are typically designed based on the efficiency maps of the motor, which is a cost-effective method for optimizing the power consumption and power efficiency over the required ranges of torque and speed [4][5][6][7].…”

A Novel Optimal Current Trajectory Control Strategy of IPMSM Considering the Cross Saturation Effects

“…The interior permanent magnet synchronous machine (IPMSM) has become an ideal choice for electric vehicles (EVs) nowadays because of its higher torque density, wider speed range, and higher reliability compared with other types of machines [1,2]. Due to fluctuant working conditions, the traction motors of EV are commonly in operation at partial load mode where a low torque and high speed are required [3,4].…”

“…In full speed range, the most popular running state of IPMSM is to realize the maximum torque per ampere (MTPA) operation below the base speed. In other words, it takes full advantage of electric torque with minimum copper loss, then acquires a high speed by sacrificing torque performance in the flux weakening region within safety boundaries [2,5]. The control references are derived by computing the intersection of the constant torque line and the voltage constraint locus [6][7][8].…”

“…Consequently, it may be imprecise to apply fixed parameters in the motor model and control strategy to control IPMSM. According to the flux linkage Equation (1), the computational model has been modified in [22], as shown in Equation (2). A 10 kW IPMSM has been computed by the finite element analysis (FEA) using…”