In a three-phase bridge inverter system, two switching devices on the same bridge arm operate in a complementary state. Since the turn-on time of general switching devices is less than the turn-off time, if the complementary control signal is added to the control stage of two switching devices on the same bridge arm, then the two switching devices will have a "pass-through". In order to prevent "straight-through", the current inverter system widely uses the time delay control technology that the ideal PWM control signal rising or falling edge delayed for a period of time, the output signal is not controllable during this time, which is the dead time. The existence of dead time makes the inverter unable to reproduce the waveform of the control signal completely and accurately, resulting in errors in amplitude and phase of the output voltage. Due to the dead time, the small distortion caused in each modulation cycle will inevitably distort the output current waveform of the inverter after accumulation, which will not only reduce the fundamental amplitude, but also generate low harmonics, directly affecting the operating performance of the motor at low speed. The estimated rotor position indirectly determines the polarity of the motor three-phase current, and then compensates the deadband to improve the operation performance of DC brushless motor at low speed.

In a modulation cycle, tuon indicates the trigger on time of the bridge arm switch signal on phase u, and the trigger on time after compensation is t'uon; tvon indicates the trigger on time of the bridge arm switch signal on phase u, and the trigger on time after compensation is t'von; twon indicates the trigger on time of the bridge arm switch signal on phase u, and the trigger on time after compensation is t'uon; tvon indicates the trigger on time of the bridge arm switch signal on phase u, and the trigger on time after compensation is t'von; tvon indicates the trigger on time of the bridge arm switch signal on phase u, and the trigger on time after compensation is t'von. Through the analysis of the above six sectors, it can be seen that when the current polarity is positive, the dead time will shorten the upper bridge high level time by Td and the lower bridge low level time by Td; when the current polarity is negative, the dead time will lengthen the upper bridge high level time by Td and the lower bridge low level time by Td. According to the symmetry of the three-phase currents, it can be seen that one of the three-phase currents When the current polarity of the phase to be compensated is positive, the comparison time of the phase reference signal should be advanced by Td, and when the current polarity of the phase to be compensated is negative, the comparison time of the phase reference signal should be delayed by Td. Table 8 shows the compensation of the phase to be compensated when the rotor position θe is in different intervals.