Voltage Sampling Influence and Improvement Strategy of Medium Voltage Megawatt Power Grid Simulator

doi:10.11985/2021.04.026

Abstract

Abstract:

In order to test the grid adaptability of MW-level and medium voltage direct-connected grid connected power generation systems such as photovoltaic power station, wind turbine and pumped storage plant, a 35 kV/3 MW grid simulator topology is introduced. However, limited by the sampling accuracy of potential transformer (PT), the direct use of PT output signal as the feedback of voltage regulator will seriously reduce the control bandwidth of the system and affect the dynamic and steady-state performance of the system output voltage. The frequency domain modeling is carried out according to the characteristics of PT, the influence of PT sampling on the system control is analyzed, and an improved control strategy is proposed. The output voltage of PT is used as the feedback of the effective value loop to ensure the steady-state accuracy. At the same time, the high-bandwidth and low-voltage instantaneous value sampling control is added to track the voltage command, so that the output characteristics of the power grid simulator can meet the requirements. The experimental prototype of 35 kV/3 MW power grid simulator verifies the feasibility and correctness of the control scheme.

Key words: Medium voltage power grid simulator, potential transformer, low voltage instantaneous value feedback, voltage RMS feedback

CLC Number:

TM464

SUN Yong, , LAI Jidong, WANG Qingfa, DONG Lei. Voltage Sampling Influence and Improvement Strategy of Medium Voltage Megawatt Power Grid Simulator[J]. Journal of Electrical Engineering, 2021, 16(4): 205-212.

Figures/Tables 13

References 20

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参数	数值
系统相电压U_o/kV	20.207
直流电压U_d/V	700
额定频率/Hz	50
额定功率/MW	3
变压器变比	0.4/5.2
变压器漏感L₁₁/mH	0.01
励磁电感/mH	1.5
滤波电感L₁/mH	0.6
滤波电容C₁/μF	120

参数	数值
额定电压/kV	35
额定容量/MVA	3
高电压穿越测试功能	暂态输出电压110%~130%
低电压穿越测试功能	暂态输出电压5%~90%
稳态电压偏差	≤±1%
阶跃响应调节时间/ms	≤10
输出谐波调节功能	2~7次,单次精度≤±0.3% 8~25次,单次精度≤±3%
输出频率调节范围	45~60 Hz,精度为0.01 Hz