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.

The coordinate transformation method of asymmetric dual three phase synchronous motor (ADTP-SM) is a Double dq transform using two dq-axes and a vector space decomposition (VSD) model method using the orthogonality of ADTP-SM. There are several studies comparing the two methods in a healthy state, but few in a single-phase open fault state. In the healthy, when the VSD model is applied, different harmonic orders of the phase current are projected onto the dq and xy-axes (the axis for controlling harmonics of the phase current), and the two-axes are orthogonal, so it can be controlled stably. In the single-phase open fault state, the same current control logic as in the healthy situation is applied. When applying the Double dq transform, the dq-axis of the fault set fluctuates, and it affects the healthy set, so it cannot be controlled stably. When applying the VSD model, if both the dq-axis and the xy-axis are controlled, the two coordinate systems do not have orthogonality and cannot be stably controlled, due to mutual interference. However, if only the dq-axis is controlled, it can be controlled stably because there is no Cartesian coordinate system other than the dq-axis. In the healthy state and single-phase open fault state, the equation is verified through experiments and simulations, and the control stability according to the coordinate transformation is compared.

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.

This paper proposes hybrid mode control for an asymmetric dual three-phase synchronous motor (ADTP-SM) with separated neutral points in a single-phase open-fault situation. The fault-tolerant control is classified into the maximum torque mode and minimum loss mode. For an arbitrary phase with an open fault, the combination of phase currents for operation in each mode is derived by mathematical analysis. In maximum torque mode operation, a rotational coordinate transformation is proposed to minimize the performance variance according to the speed. In minimum loss mode operation, a stationary coordinate transformation is proposed to control the harmonics of the phase currents. This stationary coordinate transformation can be applied to arbitrary-phase open-fault situations. In addition, the performances with and without harmonic control are compared and analyzed, and the smoothness of the mode conversion is also analyzed. The validity of the proposed coordinate transformations is verified through experiments at various speeds.