This paper proposes a junction temperature estimation algorithm for the insulated gate bipolar transistor (IGBT) based on a power loss calculation and a thermal impedance model for inverter systems. The Simulink model was designed to calculate the power losses of power semiconductor devices and to estimate the junction temperature with a simplified thermal impedance model. This model can estimate the junction temperature up to the transient state, including the steady state. The parameters used to calculate the power losses, the thermal resistance, and the thermal capacitance were optimized for a given inverter to be tested for improving the accuracy. The simulation results and experimental measurement data were compared to verify the proposed junction temperature estimation algorithm. Finally, the algorithm was installed on the inverter controller, and the performance was verified by comparing the real time estimation result with the measured temperature.

To detect the three-phase current in the complex plane of a DC link shunt inverter, an algorithm for restoring the current is required. In this paper, a method of dividing the detection voltage and the compensation voltage to match the output voltage as much as possible to reduce the total harmonic distortion while restoring the current is proposed. In addition, an overmodulation algorithm for a 12-step output, which corresponds to the largest voltage in a DC link shunt inverter, is proposed, and a current recovery method in the overmodulation region is proposed. To determine how to ensure a linear output voltage, the fundamental frequency of the output voltage is analyzed through a Fourier series, and a new voltage vector whose fundamental frequency amplitude is equal to the amplitude of the command voltage is calculated. Finally, the performance of the proposed algorithm is verified through simulation and experimentation. The output of a motor was increased by using overmodulation, and the harmonics of the current based on the output voltage were analyzed through a Fourier series.

In permanent magnet motors, the stator resistance and magnetic flux of the magnet change as the temperature increases. These changes result in a change in the maximum torque point per unit ampere (MTPA) of the motor. Without adequate compensation, this leads to a decrease in output torque. For this reason, look-up table (LUTs) are prepared over the temperature range and used for interpolation. This paper proposes a method to compensate for the output torque reduction due to a temperature increase using only a single LUT prepared at a base temperature. First, an estimation of the magnetic flux linkage and the output torque using a single LUT is performed. Second, the problem is modeled as a limited optimization problem to minimize the loss due to the torque reduction. The magnetic flux linkage and output torque are calculated in real time through the fundamental active power. The compensation value is calculated using the Lagrange multiplier method, an optimization technique, using the estimated magnetic flux linkage and output torque. The proposed method is verified by comparing it with other algorithms through simulation and experiment.