IEEE Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia 2018)

313 / 2017-12-08 14:01:22

Design of GaN-Based Ultra-high Speed PMSM Drive

Plenary track > Applications in renewable energy and storage, transportation, industrial drives, and grid power

Summary
In this paper, a design of GaN-based ultra-high speed PMSM drive is proposed. This drive uses a modular layout, including three-phase half-bridge inverter and controller circuit. The switching frequency can be improved to 40 kHz, thereby increasing control performances of the high-speed PMSM. An optimized vector control algorithm is developed to reduce calculation time which is limited by the high switching frequency. Sensorless control is implemented because of the high-speed application. This controller uses a second-order sliding-mode observer (SMO) for position and speed estimation. The SMO achieves high dynamic response and strong robustness, and the calculation time of the total control algorithm satisfies the high control frequency.
Motivation
Ultra-high-speed PMSM has wide applications, e.g., aerospace and energy storage. Electric frequency of the high-speed PMSM can be larger than 1 kHz. Thereby, high switching frequency is required to achieve high control performance. However, the maximum switching frequency is limited in traditional Si-based devices. Because of small junction capacitance and low conduction loss of the GaN device, the switching frequency and efficiency can be greatly improved1. However, DSP calculation speed limits the actual switching frequency, thereby, the control algorithms including machine control and modulation should be optimized to reduce the calculation burden. Rotor position sensors require mounting space and accuracy of these sensors is reduced in the ultra-high-speed applications. Thus, sensorless control is favorable in the control of high-speed machine. Some literatures have investigated the sensorless control based on sliding-mode position observers2. Besides the considerations of high dynamic response and high robustness of the machine control system, the position observers have to satisfy the calculation time limit in such high-switching frequency application.
Result
Fig. 1 presents the hardware of the GaN-based drive. This drive contains a three-phase GaN inverter and a DSP (TMS320F28335) control board. The optimized modulation algorithm is shown in Fig. 2. This algorithm injects a calculated three harmonic signal, which was based on the three-phase voltage reference signals into the standard sine reference signal, thereby obtains the same modulation result as the traditional SVPWM method. The principle and simulation result of super-twisting algorithm second-order sliding-mode observer (STA-SMO) is shown in Fig. 3 and Fig. 4. It’s obviously that the STA-SMO has a high estimation accuracy and get the desired effect. Experimental verifications are ongoing.

1Tatsuo Morita, Satoshi Tamura, Yoshiharu Anda, etc., “99.3% Efficiency of Three-Phase Inverter for Motor Drive Using GaN-based Gate Injection Transistors”, Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), vol., no., pp. 481-484 (2011).
2Donglai Liang, Jian Li, Ronghai Qu, “Sensorless Control of Permanent Magnet Synchronous Machine Based on Second-Order Sliding-Mode Observer With Online Resistance Estimation”, IEEE Transactions on Industry Applications, vol. 53, no. 4, pp. 3672-3682 (2017).