646 / 2022-03-31 00:19:24

Analysis of multiple valve units steep front impulse voltage test of HVDC thyristor valve

Thyristor valve

Purpose/Aim

With the development of HVDC transmission, the latest Chinese standard for thyristor valves specifies the steep front impulse voltage test of multiple valve units as one of the type tests. And this test item has not been implemented before. Therefore, it is necessary to calculate and demonstrate this test according to the characteristics of the thyristor valve. And finally carry out this test.

Experimental/Modeling methods

Based on the single valve steep front test, the calculation model and parameters of single valve can be obtained, and then the calculation model of double valve can be obtained. Since the load characteristics of MVU lightning impulse are similar to those under steep front impulse voltage, the corresponding simulation load parameters and stray capacitance parameters can be calculated according to MVU lightning impulse test. Finally, according to the obtained double valve calculation model and simulation load calculation model, the MVU steep front impulse test waveform can be simulated and calculated. This test is successfully carried out on a ± 800kV thyristor valve.

Results/discussion

This steep front voltage test is carried out for a ±800kV thyristor valve used in Baihetan- Jiangsu UHV DC project. The measured waveform steepness and the voltage ratio on the simulation load are consistent with the above calculation model. The total test voltage reaches 2462kV and the maximum steepness reaches 1726kv/us.

Conclusions

Under high-frequency voltages such as lightning and steep front voltage, the stray capacitance of the valve and MVU decreases, which has an obvious impact on the voltage distribution of the equivalent load and the valve. In the actual test, the required voltage distribution can be obtained by adjusting the value of the adjustable capacitance in the simulation load and paralleling the appropriate capacitance on the test valve.