An important analytical method for motor vector control
In the operation of the motor, a rotating coordinate system with synchronous rotating speed is established by synchronous rotation of the motor stator and the rotor magnetic field. This rotating coordinate system is a commonly known D-Q rotating coordinate system. On this rotating coordinate system, all electrical signals can be described as constants. In order to facilitate the study of motor vector control problems, can the D-Q conversion result be directly obtained by the instrument?
DQ transform is a decoupling control method, which converts the three-phase winding of the asynchronous motor into an equivalent two-phase winding, and converts the rotating coordinate system into orthogonal stationary coordinates to obtain the voltage and current expressed by the direct current. Relationship. The D-Q transformation allows each control quantity to be separately controlled, which can eliminate the influence of harmonic voltage and asymmetric voltage. Due to the application of synchronous rotating coordinate transformation, the separation of fundamental wave and harmonic is easy to realize.
Since the main magnetic flux of the DC motor is basically uniquely determined by the excitation current of the field winding, this is the fundamental reason why the mathematical model of the DC motor and its control system are relatively simple.
Analysis and control can be greatly simplified if the physical model of the AC motor can be equivalently transformed into a DC-like mode. The coordinate transformation is carried out according to this idea.
Application of D-Q coordinate transformation
The theory of motor coordinate transformation has been widely used in the field of electrical engineering. It is widely used not only in motor control and transient analysis, but also in power system fault analysis and grid power quality detection and control. Motor coordinate transformation theory The main applications are as follows.
1, motor control
2. Analysis of transient operation of the motor
3, motor fault diagnosis
Test Methods
D-Q conversion is widely used in motor testing. As long as the rotor position can be accurately obtained and the current of the three-phase signal can be accurately measured, a real-time algorithm operation can be realized by using a high-speed FPGA in parallel, and the three-phase coordinate system of the stationary stator relative to the stationary stator can be converted into a two-phase coordinate system of the stationary stator by a clark transform. The corresponding transformed outputs Iα and Iβ are output, and then the park transform is used to convert the two-phase coordinate system that is stationary relative to the stator into a two-phase coordinate system that is stationary with respect to the rotor to calculate ID and IQ. The motor control process is an inverse transformation process. First, the excitation current and the torque current are set, and then converted to two phases that are stationary relative to the stator, and then converted to three phases that are stationary relative to the stator, thereby realizing control of the motor.
At present, ZLG Zhiyuan Electronics is planning to implement this DQ conversion function in the power analyzer, which can provide reference for motor control. The motor control process can design and control the motor control by comparing the set value with the result of the power analyzer test. , algorithm optimization, etc.
