The realization of a permanent magnet synchronous motor drive with digital voltage vector selection current controller

The realization of a fully digital PMSM (permanent magnet synchronous motor) drive with flux weakening and vector modulation is presented. The controller is implemented in a microcontroller-based single-board computer card. To obtain fast execution time and high current loop bandwidth transformations and switching time sequences for vector modulation were stored in look-up tables. With this solution, a 5 kHz sampling frequency for the current control loop was obtained. The current risetime was measured to 800 μs with an overshoot of approximately 35% in the quadrature axis and 5% in the direct axis at standstill. Some crosscoupling in the two axes was observed. The applied optimum current calculation algorithm gives maximum torque-to-current ratio in the constant torque region as well as in flux weakening. The algorithm simplifies the calculation of the currents phase advance in flux weakening. This was done in an outer loop which was calculated every millisecond. Tests with speed control have shown the validity of the control principle in wide speed range