Compensation system and method for zero-crossing voltage of back electromotiv force of brushless direct current motor

A compensation system for a zero-crossing voltage of back electromotive force of a brushless direct current motor, comprising:

• a direct current power supply;
• a three-phase inverter, connected to the direct current power supply and the brushless direct current motor;
• a back electromotive force detection module configured to detect terminal voltages of three phases in response to the brushless direct current motor being in operation, wherein the three phases comprise two conduction phases and one suspended phase;
• and
• a controller, connected to the three-phase inverter through the back electromotive force detection module;
• wherein the compensation system further comprises a current acquisition module connected between the direct current power supply and the controller, and the current acquisition module is configured to acquire a bus current value in response to the brushless direct current motor being in operation;
• the controller comprises a voltage compensation module connected to the back electromotive force detection module, and a plurality of groups of bus current threshold intervals are preset in the voltage compensation module;
• the voltage compensation module is configured to determine a group of bus current threshold intervals where the bus current value is located and output a corresponding voltage compensation signal based on the group of bus current threshold intervals;
• and
• the controller is configured to compensate a zero-crossing voltage of back electromotive force of the brushless direct current motor based on the voltage compensation signal, and control the brushless direct current motor to perform a commutation operation.

A compensation method for a zero-crossing voltage of back electromotive force of a brushless direct current motor, wherein the compensation method is applied to a compensation system for a zero-crossing voltage of back electromotive force of a brushless direct current motor, and the compensation method comprises the following blocks:

• block S1, acquiring, by a current acquisition module, a bus current value, in response to the brushless direct current motor being in operation;
• block S2, acquiring in real time, by a controller, terminal voltages of three phases of the brushless direct current motor through the back electromotive force detection module, and calculating half of a sum of terminal voltages of two conduction phases;
• block S3, detecting in real time, by the controller, whether the terminal voltage of the suspended phase is equal to half of the sum of terminal voltages of the two conduction phases, and at the same time, determining in real time, by the controller, a bus current threshold interval where the bus current value is located;
• and
• wherein the compensation method further comprises one of the following blocks:
• block S4, determining, by the controller, the zero-crossing voltage of back electromotive force of the brushless direct current motor being half of the sum of terminal voltages of the two conduction phases, in response to the bus current value being a low threshold interval;
• and determining, by the controller, the zero-crossing point of back electromotive force of the brushless direct current motor, and executing the zero-crossing commutation procedure, in response to the controller determining that the terminal voltage of the suspended phase is equal to half of the sum of terminal voltages of the two conduction phases;
• block S5, compensating, by the controller, the zero-crossing voltage of back electromotive force of the brushless direct current motor according to the voltage compensation signal, in response to the bus current value being a high threshold interval;
• and determining, by the controller, the zero-crossing point of back electromotive force of the brushless direct current motor, and executing the zero-crossing commutation procedure, in response to the controller determines that the terminal voltage of the suspended phase being equal to a compensated zero-crossing voltage of back electromotive force of the brushless direct current motor;
• and
• block S6, controlling, by the controller, the brushless direct current motor to perform over-current shutdown protection, in response to the bus current value exceeding the high threshold interval.