VVVF frequency conversion, vector control frequency conversion, and direct torque control frequency conversion are all one of the AC-DC-AC frequency conversion. Its common disadvantages are low input power factor, large harmonic current, large demand for energy storage capacitors in DC circuits, and renewable energy can not be reflected back to the grid, that is, four-quadrant operation cannot be carried out. For this reason, matrix alternating frequency-alternating frequency came into being. Because matrix AC-AC frequency conversion eliminates the central DC link, thus eliminating the large and expensive electrolytic capacitors. It can complete the power factor of L, the input current is sinusoidal and can operate in four quadrants, and the power density of the system is large. Although this skill is not currently sophisticated, it still attracts many scholars to study it in depth. Its essence is not to indirectly manipulate the current and flux equals, but to directly use the torque as the quantity to be manipulated. Here's how:
1. Control the stator flux to introduce the stator flux observer to complete the speed sensorless mode;
2. Automatic identification (ID) relies on the first-class motor mathematical model to automatically identify motor parameters;
3. Calculate the practical value corresponding to the stator impedance, mutual inductance, magnetic fullness factor, inertia, etc., and calculate the practical torque, stator flux, and rotor speed for real-time control;
4. Complete the Band-Band control, and generate PWM signals according to the Band-Band control of the flux and torque, and control the inverter switch status.
Matrix alternating frequency conversion has fast torque response (<2ms), high speed accuracy (±2%, no PG reaction), and high torque accuracy (<+3%). At the same time, it also has high starting torque and high torque accuracy, especially at low speed (including 0 speed), it can output 150%-200% torque.
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