Position sensor-less estimation method for low-capacity bus capacitor driver

The invention relates to a position sensor-less estimation method for a low-capacity bus capacitor driver, and belongs to the technical field of motor equipment. The method comprises the steps that 1) a microcontroller transforms phase currents ia and ib sampled by a current sensor from three phases to two phases to obtain ialpha and i beta; 2) pure time-delay filtering is carried out on Vd and Vq; 3) reverse PARK transformation is carried out on Vd and Vq to obtain Valpha and Vbeta; and 4) according to ialpha, ibeta, Valpha, Vbeta as well as the inductance Ls, the phase resistance Rs and the rotor linkage psif of a motor, the rotating speed and position of a motor rotor are calculated by utilizing a virtual coordinate system. Influence of capacitance decrease of a bus capacitor on the sensor-less estimation method is effectively eliminated, realization is simple and convenient, the position estimation error is decreased to lower than 15% of the original, it is basically ensured that decrease of the bus capacitance does not influence the position estimation precision, and the low-capacity bus capacitor driving system can use the position sensor-less control scheme.