瞬动校验电流误差分析评价与控制系统的研究

发布时间：2019-06-16 13:55

【摘要】：随着用电需求的不断增大，，处于电力系统末端起保护作用的低压断路器的用量逐年增加。低压断路器除了具有接通、分断电路的功能外，还具有短路保护、漏电保护、过载保护等功能，其中，短路保护又称为瞬动保护。在断路器产品出厂前，需要对断路器产品的瞬动特性进行调整与检测。由于检测技术和检测水平的限制，存在断路器瞬动校验精度不高问题，在实际使用中存在“误动”和“拒动”现象，这会对电力系统造成很大危害，同时威胁人们的用电安全。因此，对提高断路器瞬动校验精度的研究具有十分重要的意义。本文首先深入分析了国内外断路器瞬动检测标准和试验方法，对比其中的差异，深入分析存在差异的原因，阐述了各自的优点与不足。针对国内普遍使用的断路器瞬动校验设备，总结归纳了影响瞬动校验精度的因素；提出了校验电流评价与误差分析方法；校验电流逐步逼近控制方法；基于希尔伯特变换的功率因数角计算选相合闸方法；以及试验设备优化设计方案。电流发生系统是一个双输入单输出系统，电流误差表现为幅值误差和电流的暂态过程，它产生于电压控制和选相控制。为消除校验电流的误差，本文提出了校验电流误差分解方法。通过理论和试验验证，证明了该方法的准确性和实用性，为设计控制试验系统奠定了基础。为了保证断路器短路保护特性整定校验的精度，必须对产生的校验电流的精度做出评价。当试验电流精度满足校验要求时，才能将试验结果作为断路器瞬动整定校验依据。针对电流幅值误差和电流的暂态过程，本文提出一种校验电流综合评价方法。提出了一种校验电流广义闭环控制的思想，将每次校验电流存在误差作为下一次试验控制和调节的依据，逐步逼近校验电流期望值。通过对PID和模糊PID两种控制方法的控制效果对比，阐述了模糊控制方法的优势。针对快速傅里叶变换计算电压、电流初相位算法，深入分析了在电信号频率变化时算法存在误差原因，并提出希尔伯特变换方法计算电信号初相位的方法，通过仿真和实际验证，该方法在电信号频率变化时，具有很好的鲁棒性和计算精确度。提高了基于功率因数角计算的选相合闸精度。最后，对试验系统硬件进行改进优化设计，降低了试验系统中非线性因素对试验电流精度的影响。通过对试验系统测试表明，该系统具有试验精度高，调节速度快的优点。
[Abstract]:With the increasing demand of electricity, the amount of low voltage circuit breaker which plays a protective role at the end of power system increases year by year. Low voltage circuit breaker not only has the function of switching on and breaking circuit, but also has the functions of short circuit protection, leakage protection, overload protection and so on. Among them, short circuit protection is also called transient protection. Before the circuit breaker product leaves the factory, it is necessary to adjust and test the transient characteristics of the circuit breaker product. Due to the limitation of detection technology and detection level, there is a problem that the transient calibration accuracy of circuit breakers is not high, and there are the phenomena of "misoperation" and "rejection" in practical use, which will cause great harm to the power system and threaten the safety of power consumption at the same time. Therefore, it is of great significance to improve the instantaneous calibration accuracy of circuit breakers. In this paper, the transient detection standards and test methods of circuit breakers at home and abroad are deeply analyzed, the differences are compared, the reasons for the differences are deeply analyzed, and their advantages and disadvantages are expounded. In view of the transient calibration equipment of circuit breakers commonly used in China, the factors affecting the accuracy of transient calibration are summarized and summarized; the methods of checking current evaluation and error analysis are put forward; the step by step control method of calibration current; the phase selection and closing method of power factor angle calculation based on Albert transform; and the optimal design scheme of test equipment are put forward. Current generating system is a double input and single output system. The current error is a transient process of amplitude error and current, which is caused by voltage control and phase selection control. In order to eliminate the error of calibration current, a method of error decomposition of calibration current is proposed in this paper. Through theoretical and experimental verification, the accuracy and practicability of the method are proved, which lays a foundation for the design of control test system. In order to ensure the accuracy of setting calibration of short circuit protection characteristics of circuit breakers, the accuracy of calibration current must be evaluated. When the test current accuracy meets the calibration requirements, the test results can be used as the basis for transient setting calibration of circuit breakers. Aiming at the amplitude error of current and the transient process of current, a comprehensive evaluation method of calibration current is proposed in this paper. In this paper, an idea of generalized closed loop control of calibration current is proposed. The error of each check current is taken as the basis of control and adjustment in the next test, and the expected value of check current is approximated step by step. By comparing the control effects of PID and fuzzy PID control methods, the advantages of fuzzy control methods are expounded. Aiming at the algorithm of calculating voltage and current initial phase by fast Fourier transform, the causes of error in the algorithm when the frequency of electric signal changes are deeply analyzed, and the method of calculating the initial phase of electric signal by Albert transform is put forward. Through simulation and practical verification, this method has good robustness and accuracy when the frequency of electrical signal changes. The accuracy of phase selection and closing based on power factor angle calculation is improved. Finally, the hardware of the test system is improved and optimized to reduce the influence of nonlinear factors on the accuracy of the test current. The test results show that the system has the advantages of high test accuracy and fast adjustment speed.
【学位授予单位】：河北工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM561

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