PID control

Application to Dynamic Load Testing of Cylinder Loads

PV module compressive test is divided into static and dynamic load, this paper focuses on solving the problem of large fluctuation in the dynamic load test process.

1. Cylinder load structure

Cylinder load is widely used in the load test of solar modules due to its convenient operation.

The cylinder loads are constructed as follows:

In the figure, 1 is a cylinder or hydraulic cylinder, 2 is a solar energy assembly, 3 is a control system, 4 is a piston, 5 is a pull pressure sensor, 6 is a suction cup, 7 is an air compressor, 8 is an inflation valve set, 9 is a flow control valve, 10 is a vacuum valve, and 11 is a vacuum generator.

The control method is as follows:

Turn on the air compressor, the control system controls the on-off condition of the inflatable valve group, the upper air port A on the cylinder is inflated, the lower air port B is deflated, the piston goes down through the suction cups to apply the pressure to the solar module, the control system receives the magnitude of the pressure from the pull-pressure sensor, and the control system controls the flow rate control valve so that the pressure reaches the target value.

2. Uncontrollable large fluctuation of tension and pressure in dynamic load test

In the actual dynamic load test due to the pull pressure switching frequency is very fast, 3-7 cycles per minute, if each cycle is adjusted, the proportional valve adjustment is always slightly lagging behind, resulting in a large fluctuations in the pull pressure system phenomenon.

An example is as follows:

The set value is 1000Pa, the actual value may oscillate back and forth between 900Pa and 1300 adjustments can not get a relatively smooth curve, exceeding the standard requirements of ± 100Pa requirements.

3. Problem solving

We see the whole dynamic loading process as a whole process for PID control, instead of controlling each tensile pressure cycle, this so as to eliminate the problem of poor stability and high fluctuation.

3.1 PID control theory

1. Proportional (P) regulation: the proportional role is mainly used to control the deviation that occurs, that is, there are differences in control. Each time the value of the pulling force and the target value of the pulling force to compare, for deviation, proportional regulation to reduce the deviation. The advantage of proportional regulation is that the control is timely, rapid, and reduces the deviation, but it cannot eliminate the steady state error.

2. Integral (I) regulation: Integration can be understood as the control of past errors; it records all previous errors and can be used to eliminate static errors.

3.2 Effect of PID control application

Through the PI control principle in the PID control method, the pressure can be precisely controlled and the whole dynamic loading process is smooth.

Author's Profile

Gu Binwei

With more than ten years of technical precipitation in the electrical industry, he has specialized in the R&D and application of photovoltaic technology in recent years. After joining Zealwe Tech, he is mainly responsible for the electrical design of PV physical testing equipment, and has successively completed the electrical design and debugging of equipment for crushing, hail, stripping, lead end and mechanical load.