Power system voltage stable on-line monitoring and prevention control method based on probability

Abstract

The method includes following steps: obtaining online data of power network from energy management system and power market; determining probability of equipment fault in the time period based on arrangement of equipment repair and weather condition in each area; creating sample space from Monte Carlo simulation, each sample includes two parts: X (increment direction of power), and Y (set of fault equipment); calculating steady tolerance of voltage corresponding to each sample and obtaining probability density distribution of voltage of voltage in power system from layered computation method; determining value of steady tolerance system needed to reach, limiting values of system parameters, and precaution control value; adjusting working parameters of system to ensure steady voltage in power system under specified confidence level. Advantages are: getting rid of a great lot calculation in traditional 'point-by-point method' and avoiding CPF calculation again.

Description

technical field [0001] The invention belongs to the field of on-line voltage safety assessment and control, and relates to a probability-based on-line monitoring and prevention control method for power system voltage stability. Background technique [0002] Maintaining grid voltage stability has great economic and social significance. Although offline analysis of voltage stability can partially reveal the mechanism of voltage instability, it is difficult to adapt to changes in the actual system operation mode. Therefore, online monitoring and control of voltage stability has become particularly important. [0003] On-line monitoring and control schemes for voltage stability can be divided into two categories: the first category is based on deterministic methods, and the second category is based on probabilistic methods. [0004] Scenarios based on deterministic methods include the following: [0005] 1. Low voltage load shedding scheme. This scheme has been widely used in...

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Problems solved by technology

This type of method avoids the calculation of a large number of samples, but the expression of the probability formula is often too complicated, and the probability function used is very strict, it is difficult to accurately describe the actual power system behavior, and it is impossible to obtain an accurate probability density distribution.

[0010] 2. Enumeration method, which enumerates all possible states of the system for calculation. This method is only suitable for theoretical research on small systems, and it is difficult to apply in actual systems because there are too many state quantities to be considered.

However, the existing methods are extremely time-consuming for the calculation of a large number of samples, and currently can only be applied to offline analysis of voltage stability

[0012] Compared with the probabilistic method, the calculation speed of the scheme based on the deterministic method is fast, and it is suitable for online application, but there are the following problems: (1) The deterministic method adopts the way of giving the expected fault set in advance for safety verification, and the most The voltage stability index corresponding to the serious expected fault is used as the basis for judging the voltage safety, which cannot deal with multiple faults and cascading faults, and may cause the stability index to be optimistic due to the omission of more serious faults. It is possible that the expected failure set contains serious failures with a small probability of occurrence, resulting in a conservative stability index

(2) The deterministic method cannot reflect the impact of a large number of uncertain factors on the power grid (fluctuations in load and generator output distribution, equipment failure probability, weather changes, etc.), and the amount of information provided is very limited, which is not conducive to the market environment Under the system operators comprehensively consider the security and economy of the power grid

However, the existing probabilistic methods all use the "point-by-point method", that is, calculate each sample separately. Due to the large number of samples, the calculation speed is very slow and time-consuming, so it can only be used for offline theoretical analysis.

At present, there is no probabilistic-based voltage stability monitoring and control method that can be applied online at home and abroad.

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