electric motor

controller

Power amplifier conversion device

Corresponding sensor

Constant torque load

constant power load

Fan, pump loads

Voltage regulation (voltage reduction) speed regulation

Magnetization (magnetic weakening) speed regulation

Adjust resistance (increase resistance) and adjust speed

n=（Ud0-Idr）/Ce

G-M system

V-M system

static controlled rectifier

Tsmax=1/mf V-M system

Tsmax=1/f PWM system

Speed ​​range

Static error rate

Voltage comparison link

Proportional regulator

Power electronic converter

DC motor

Speed ​​test feedback link

The static characteristics of a closed-loop system can be much stiffer than the mechanical characteristics of an open-loop system

The static error rate of a closed-loop system is much smaller than that of an open-loop system.

Closed-loop system can greatly increase the speed range

Resist disturbance and obey given

Adopt proportional integral control system

Steady-state error of DC speed control system

The proportional control is a zero-type system, and there is a difference in steady state.

Proportional and integral control is a one-type system with no difference in steady state

M method speed measurement

T method speed measurement

The use of cut-off current negative feedback link can limit the armature current

Inner loop: current loop (used at startup) ACR ACR is never saturated

Outer loop: speed ASR. When ASR is saturated, the output reaches the limiter, the outer loop is in an open-loop state, and it has a linear relationship when it is not saturated.

The current rises. ASR is not saturated

Constant current speed up. ASR saturation, ACR effect

Speed ​​adjustment, ASR desaturation, ASR function

Features

Load current

Grid voltage fluctuations

Follow the given voltage change

Anti-interference effect against load changes

Its output amplitude determines the maximum allowable current of the motor

Current closely follows a given voltage

Anti-interference effect on power grid voltage fluctuations

Ensure the maximum allowable current of the motor is obtained during the dynamic process

Follow performance metrics

Anti-interference performance index

It is best to follow the performance index Kt=0.5. Good following performance, slightly poor anti-interference performance

h=5 has the best performance, relatively large overshoot and good anti-interference performance

First the inner ring, then the outer ring

Approximation and Correction

Determine regulator type based on calibration

Parameter settings

Simplification of current loop structure diagram. Adopt Type I system

Choice of current regulator structure. Using proportional integral current regulator

Current regulator parameter calculation

Implementation of current regulator

Equivalent closed-loop transfer function of current loop

Structural selection of speed regulator. Using proportional integral speed regulator

Parameter calculation of speed regulator

Implementation of speed regulator

The first quadrant: forward rotation, the motor is in electric state

Second quadrant: forward rotation, the motor is in braking state

The third quadrant: reverse rotation, the motor is in electric state

The fourth quadrant: reverse, the electric motor is in braking state

The average voltage is less than zero, the motor speed can be reversed

Ud is a positive value and the motor rotates forward.

Ud is a negative value, the motor reverses

Ud=0. Motor stalls

The direction of the armature current determines whether the current flows through the freewheeling diode or through the electronic switching device

When the conduction angle is <90°, Ud>E, the V-M system operates in the first quadrant

When the conduction angle is >90°, Ud0 is negative, the motor reverses, and a reverse electromotive force is generated.

Install smooth wave reactors and circulating current reactors to suppress circulating currents

If the motor is working at the rated state, the speed is called the base speed

Speed ​​mode

Steady-state relationship between torque and slip

Frequency

Changing magnetic pole logarithm speed regulation

Change slip speed regulation

change voltage

change frequency

Change motor parameters

Keep the power frequency constant and change the stator voltage

The constant torque power remains unchanged and the electromagnetic power remains unchanged, regardless of the speed.

All the increased slip is consumed in the rotor resistance

Speed ​​regulation below fundamental frequency

Speed ​​regulation above fundamental frequency

Three kinds of magnetic flux

indirect frequency conversion

Direct conversion

Sinusoidal pulse width modulation (SPWM) technology

Voltage space vector (SVPWM) technology

When the motor is working in the feedback braking state, the energy cannot be fed back to the grid, causing the DC side voltage to rise, which is called the pump voltage.

Suppression measures: use DC bus power supply and install discharge resistor

Through coordinate transformation and according to the rotor flux direction, the equivalent DC motor model is obtained, and then the control system is designed by imitating the DC motor control strategy.

Three-phase dynamic model composition