Description
2. Principle of frequency converter
In embedded development, the control of motors is often involved. Currently, frequency conversion control of AC motors is widely used, so let”s briefly introduce the
frequency converter by looking at the diagram, assuming that you already understand the principle of the motor.
The block diagram is as follows:
The frequency converter is mainly composed of rectifier (AC to DC), filtering, inverter (DC to AC), braking unit, drive unit, detection unit, microprocessing unit, etc.
The inverter relies on the switching of the internal IGBT to adjust the voltage and frequency of the output power supply, and provides the required power supply voltage
according to the actual needs of the motor, thereby achieving the purpose of energy saving and speed regulation. In addition, the inverter also has many protection functions.
, such as overcurrent, overvoltage, overload protection, etc. With the continuous improvement of industrial automation, frequency converters have also been widely used.
A typical inverter system diagram is shown below. It mainly includes operation panel, VFD controller, motor and other parts.
1. Typical structure:
Mainly includes: control platform, measurement circuit, power circuit, protection circuit, etc.
There are two common types of frequency converters: voltage type and current type. Among them, the power inverter part mostly uses power
tubes such as IGBT and IGCT.
2. Typical algorithm:
Among them, the control algorithm represented by Siemens is mainly based on coordinate transformation (vector control). Friends who are
interested in the algorithm represented by ABB can search for information by themselves (direct torque control) and will not go into details here.
3. Vector control:
Many chip MCU and MPU manufacturers have provided block diagrams and algorithm libraries for variable frequency vector control. Those
who are interested can study it. For example, the following figure is a block diagram provided by Microchip
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