Simulink simulation and system analysis of double closed-loop PI DC speed control system

Block diagram of double closed loop DC speed control system

In the actual modeling, the system is slightly different. The feedback link must become a low-pass filter with a small inertia link, and the input end must also have a corresponding inertia link. The current loop and speed loop given later will be explained.

1. ASR Speed ​​Regulator
2. ACR current regulator
3. Ks Thyristor

Current loop

Here you can see that feedback and input have one more inertia link.

Speed ​​ring

The current loop here is equivalent to a first-order inertia link.

simulation

• Parameter given:
  

Simulation note:

1. Since the actual PI controller has an upper limit output, it needs to limit, but the output limit of the pid module under Simulink only adds a limiter module to the output, that is, its internal integral term will continue to integrate , It will happen that when the double closed-loop speed control system enters ASR desaturation, it cannot desaturate, because the integral term output at this time is already very large, even if the reverse integral output still reaches the amplitude. In this situation, we need to build a PI controller with an integral module and a proportional module, and then add a limiting module to the output, but note that the above problem still exists at this time, we also need to set the output limiting of the integral module, Set it to the same limit value as the limiter module. So far, the PI controller has the same operating characteristics as the actual analog controller.
2. The double closed-loop control system needs to maintain the saturation state of ASR in the first and second stages, so the selection of the limit value should be paid attention to. Here, my step is 20, the ASR limit is 10, and the ACR limit is 15.

ASR:
Ki ： 1 / 0.085
Kp: 2
ACR:
Ki: 1 / 0.051
Kp: 0.015 / 0.051
IdL: 100

Monitor output speed, armature current, ASR output, ACR output:

Id finally stabilizes at 100, which is exactly the given load current.
Forced flow-building phase (speed):

constant current speed-up phase (speed):

saturation overshoot phase (speed):

ASR, ACR output: It is

obvious that the output of ASR is saturated first, and then desaturated, the time for the beginning of desaturation is exactly The time when the speed starts to overshoot. When the current desaturates to 100, the speed starts to drop from the maximum value, which also conforms to the theoretical analysis.

to sum up

The PI controller wants to use the PID module to meet the working characteristics of the analog device, and build it yourself!
The impression of verifying what you have learned in class will be deeper!
Experience the essence of double closed loop:First open the loop to quickly stabilize a value with a small inertia, and then close the loop to stabilize a value with a large inertia! !