Monitoring critical temperatures in permanent magnet synchronous motors is crucial for improving working reliability. Aiming at resolving the difficulty in online temperature estimation, an accurate and simple five-node lumped parameter thermal network (LPTN) is proposed and the mathematical model of the LPTN is built. Both radial and axial heat transfer paths inside the motor are considered to model the complete thermal circuit. In addition, an innovative parameter identification method based on multiple linear regression is applied to identify the parameters of the LPTN model. The parameters in the state equation are identified instead of the data of the motor, which are strongly dependent on the material and geometrical parameters. Finally, an open-loop estimation scheme based on the state equation and Kalman filter algorithm is adopted to predict the motor temperature online. The model performances are validated by extensive experiments under varying speed and torque conditions in terms of the accuracy and robustness. The results indicate that the temperature estimation error is within the range of ±5 • C in most cases and the proposed model can quickly follow the load variation. Besides, the online temperature estimation scheme and parameter identification method are easy and convenient to implement in an embedded system, which is feasible in automobile applications. Appl. Sci. 2019, 9, 3158 2 of 18 permanent magnet but also changed the transient resistance of the rotor. If the transient resistance of the rotor can be obtained, the temperature of the rotor can be obtained indirectly. Therefore, when the rotor transient impedance was observed under the condition of high-frequency voltage, the rotor temperature information can be obtained by the relationship between the transient resistance and the temperature [12].However, the above-mentioned methods have some drawbacks. FEM has high estimation accuracy, but this method depends on the motor geometry, material properties, and boundary conditions, resulting in complex calculation and longer computing times. Thus, it can only be used for off-line analysis in the motor temperature field. Although the motor rotor temperature estimation algorithm based on rotor flux linkage is simple and easy to conduct, it is only able to predict the rotor temperature. In addition, the estimation accuracy depends on the observation accuracy of the rotor flux linkage, and the change of the flux linkage caused by temperature is not completely linear. Therefore, it is difficult to obtain a more accurate estimation of the rotor temperature. Compared with the method based on the rotor flux observation, the advantage of the approach based on the high frequency injection is that the change in rotor transient impedance is easier to detect. However, the injected high frequency signal may bring additional rotor loss, causing an increase in temperature.A suitable alternative to monitor motor temperature is lumped parameter thermal networks (LPTNs). This thermal network model is a simplifi...

Two problems can cause control performance degradation on permanent magnet synchronous motor (PMSM) systems, namely, fluctuation of PMSM parameters and the time delay between current sampling and command value update. In order to reduce the influence of these problems, a new current-predictive control strategy is proposed in this article for medium- and high-speed PMSM. This strategy is based on the discrete mathematical model of PMSM. This new control strategy consists of two main steps: First, an integrator is applied to calculate current compensation value; second, the predictive current value is obtained through deadbeat-current predictive method. The stability of predictive control system is also proved in the article. With this deadbeat-current predictive control scheme, the real current can reach the desired value within one control-step. Based on this new current control method, Luenberger observer and phase-locked loop position tracker is applied in this article. Experimental results for 0.4 kW surface-mounted PMSM confirm the validity and excellent performance for parameters fluctuation of new current predictive control.

The modeling of conduction and switching losses for insulated gate bipolar transistors (IGBTs) and free-wheeling diodes (FWDs) in automobile applications is becoming increasingly important, especially for the improvement of the system efficiency and the reliability prediction. The traditional modeling of conduction and switching losses based on the space vector pulse width modulation (SVPWM) is not applicable in practice due to the complex curve-fitting and the computation demands. In this paper, a simple and practical losses model for IGBTs and FWDs is proposed based on the SVPWM algorithm. Firstly, the traditional power losses model is introduced briefly. Then, the piecewise linear switching losses model and the conduction losses model based on the equivalent three-order harmonic model of the duty cycle are proposed. The comparison of experimental results between the traditional model and the proposed model is presented in the experiment validation. Furthermore, the power analyzer is adopted to measure the inverter losses, and the chips losses are further validated when other extra losses are considered. The proposed model shows good modeling accuracy with the large benefit of smaller measurement and lower computation requirements.

When a safety-related fault in the motor controller is detected, the torque output of the motor cannot be effectively shut off in time and an overcurrent occurs at the moment of switching. The advantages and disadvantages of the open circuit and active short-circuit methods are analyzed. Combining the advantages of these two operations, this paper proposes a new mixed voltage modulation method. It introduces a voltage modulation ratio that represents the duty cycle of the open circuit operation during a PWM period. This ratio is first set to a fixed value and gradually reduced to zero. The inverter is switched at a mixed operation and finally remains in the active short-circuit mode. The current can be quickly converged by a freewheeling diode of open circuit. After switching to active circuit, the brake torque is safety. The effectiveness of this shutoff method was verified by simulations and experiments. It shows that current fluctuations are suppressed and the torque output is also within a safety range. In addition, this shutoff method does not require any additional sensor information and is simple to implement.

Active-short-circuit and locked-rotor modes are common abnormal operations in new energy vehicles. The IGBT junction temperature measurement for these two operating conditions is a challenging problem due to the unexpected large current and the asymmetric operation of semiconductor chips. In addition, different cooling flow rates have a significant influence on the heat dissipation, which will also have an impact on the building of the thermal model. Based on these difficulties, a modified Foster thermal network under active-short-circuit and locked-rotor modes has been presented considering different cooling conditions. The power loss models of the semiconductor chip under abnormal conditions are developed and a modified Foster thermal network based on the NTC temperature sensor is proposed. The model can be adapted to different cooling conditions since the thermal impedance fluctuates slightly at different cooling flow rates. The proposed thermal model is verified with inverter application under active-short-circuit and locked-rotor modes and the experimental performance shows good accuracy compared with the infrared camera measurement results. INDEX TERMS Insulated gate bipolar transistors(IGBTs);active short circuit(ASC) mode; locked-rotor mode; thermal models.

<div class="section abstract"><div class="htmlview paragraph">DC link active discharge is mandatory in new energy vehicles. This paper first analyzes the necessity of active discharge in automotive inverters and then introduces the commonly used discharge methods. After reviewing the pros and cons of the current methods, a new discharge solution using IGBT (Insulated Gate Bipolar Transistor) modules WSC (Weak Short Circuit) is proposed. The essence of WSC is to make one of the shooting through IGBTs (two IGBTS forms a half bridge topology) entering into active work area by controlling its gate voltage V_GE, where the short current is controlled in safe range and IGBT V_CE voltage is relative large. Hence, large transient power is produced inside IGBT in this condition. By this method, the DC link capacitor energy will be consumed by the weak turned on IGBT gradually. Since the IGBT module has a dedicated cooling loop, the heat generated during discharging process can be transferred into coolant. In order to discharge the DC link capacitor safely, an optimized discharge topology is suggested in which PWM method is applied. This paper focuses on the intensive evaluation of the IGBT both steady and transient electro-thermal stress under this new discharge method. The simulation and experimental results show that this method can not only discharge the DC link capacitor fast, but also has no risk of IGBT damaging since the IGBT electric and thermal stresses are in the safe operation range during the discharge time. It is proved that this new discharging solution saves cost and is also practical for engineering.</div></div>

To pursue high-performance motor drive, the current regulators are designed directly in the discrete domain. However, few kinds of research are developed to achieve arbitrary poles placement simply. To fill this gap, the authors propose a discrete-time current regulator consisting of two parts: the main regulator used to obtain decoupling control of dq axes currents, and the bi-proper compensator applied to realise arbitrary poles placement. To strengthen the anti-disturbance ability of the current regulator, the active resistance is added to the inner feedback path. Combining the active resistance, a new zero-order-hold equivalent motor model is developed, based on which the main regulator is designed using the zero-pole cancellation method. Furthermore, in this way, decoupling control for the two control objectives of reference tracking and anti-disturbance is realised. To achieve fast tracking response and negligible overshoot, an easy-toimplement scheme that simplifies the tuning of the current regulator is proposed based on the arbitrary poles placement. Moreover, the current regulator can be treated as a two-degree-of-freedom controller with this scheme. Finally, the effectiveness and reliability of the proposed current regulator are validated by the simulation results and experimental results in an alternating current machine drive platform.

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