A sine wave is a signal with the most single frequency component, and it is named because the waveform of this signal is a mathematical sine curve. Any complex signal, such as a music signal, can be seen as a composite of many sine waves of different frequencies and sizes.
In the 1970s, Siemens engineer F. Blaschke first proposed the asynchronous motor vector control theory to solve the AC motor torque control problem. The basic principle of vector control is to measure and control the stator current vector of the asynchronous motor, and control the excitation current and torque current of the asynchronous motor according to the principle of field orientation, so as to achieve the purpose of controlling the torque of the asynchronous motor. Specifically, the stator current vector of the asynchronous motor is decomposed into the current component that generates the magnetic field (excitation current) and the current component that generates the torque (torque current) to be controlled separately, and the amplitude and phase between the two components are controlled at the same time, that is, control Stator current vector, so this control mode is called vector control mode (sine wave control mode). Simply put, vector control is to decouple the flux linkage and torque, which is beneficial to design the regulators of the two separately to achieve high-performance speed regulation of AC motors. Vector control methods include vector control methods based on slip frequency control, speed sensorless vector control methods, and speed sensor vector control methods. In this way, a three-phase asynchronous motor can be equivalently controlled as a DC motor, thus obtaining the same static and dynamic performance as the DC speed control system. The FOC sine wave control algorithm has been widely used in the inverters of major international companies such as Siemens, AB, GE, Fuji, and internationally renowned brands of electric cars and electric motorcycles.
The general-purpose frequency converter adopting the vector control mode can not only match with the DC motor in the speed range, but also can control the torque produced by the asynchronous motor. Since the sine wave control method is based on the accurate parameters of the controlled asynchronous motor, some general-purpose inverters need to accurately input the parameters of the asynchronous motor when in use, and some general-purpose inverters need to use speed sensors and encoders. In view of the possibility of changes in motor parameters, which will affect the control performance of the inverter on the motor, the current new vector control general inverter has the functions of automatic detection, automatic identification and self-adaptation of asynchronous motor parameters. A general inverter with this function Before the asynchronous motor is driven for normal operation, the parameters of the asynchronous motor can be automatically identified, and the relevant parameters in the control algorithm can be adjusted according to the identification result, so as to perform effective vector control on the ordinary asynchronous motor.