Method for preventing ultra-low frequency oscillation of hydropower generating set during active power regulation

Abstract

The invention discloses a method for preventing the ultra-low frequency oscillation of a hydropower generating set during active power regulation. According to the method, oscillation monitoring is performed according to the active power fixed-value adjustment and primary frequency modulation of the hydropower generating set; a fixed-value adjustment monitoring module applies a static characteristic that an active power set value usually keeps unchanged during fixed-value adjustment, and a primary frequency modulation monitoring module adopts a grid frequency as a reference, and therefore, theactive-power ultra-low frequency oscillation of the hydropower generating set which is adverse to the stability of a power system can be effectively distinguished. A judgment logic and B judgment logic are designed for primary frequency modulation with complicated working conditions; only when the two kinds of logic both consider that the primary frequency modulation is not conducive to the stability of the power system, the primary frequency modulation function is automatically withdrawn, otherwise only an alarm is issued, and operation personnel decide whether the primary frequency modulation function is to be withdrawn; and therefore, the possibility of the misjudgment, and mistakenly withdrawing the frequency modulation of a real-time control system can be eliminated, and the reliability of the function is improved.

Description

Technical field [0001] The invention belongs to the technical field of automatic control of a hydroelectric generating set, and relates to a method for preventing the active power of a hydroelectric generating set from generating ultra-low frequency oscillation during the adjustment process. Background technique [0002] In 2016, the asynchronous interconnection project between Yunnan Power Grid and China Southern Power Grid was officially put into operation, realizing the asynchronous interconnection between my country's first provincial power grid and large regional power grid. After asynchronous interconnection, the Yunnan Power Grid operates independently of the large regional power grid, showing very complex typical characteristics: 1) The system is small in scale, the proportion of outgoing transmission is high, the grid structure is weak, and the requirements for power balance are more stringent. The power disturbance of grid-connected units The influence of grid frequency...

AI Technical Summary

Problems solved by technology

During the adjustment process of the fixed value of the hydroelectric unit, or in the process of a frequency adjustment, affected by factors such as the inertia of the water flow, the inertia of the unit, and the adjustment feedback delay, it is possible that the active power of the hydroelectric unit as the adjustment target will continue to oscillate, and then in the " Under the influence of the operating characteristics of large units and small power grids, it will cause or aggravate the oscillation of the power grid frequency, which will become an unfavorable factor for the stability of the power system

[0004] The Chinese patent "A Control Method for Preventing Power Adjustment Oscillation of Hydroelectric Units" (CN 103490436 A) aims at the problem of active power oscillation of hydroelectric units caused by fixed value adjustment, and proposes self-adaptation of PID parameters for unit power adjustment and adding filtering in the power measurement link However, there are the following problems: 1) The literature only puts forward ideas, for the most difficult but also the most critical link in the method (such as "the method of tuning the control parameters", "the filter parameter increases the damping of the closed-loop adjustment loop of the unit "Mechanism", etc.) have not been positively explained and explained, so it is not feasible; 2) Most hydropower stations have not been considered (only in the Lancang River Basin, there are Gongguo Bridge, Miaowei, Xiaowan, Manwan, Nuozhadu, etc. Jinghong and other hydropower stations) does not use the PID control method for active power setting adjustment, so it does not have wide applicability

[0005] The Chinese patent "A Method for Optimizing Governor Parameters Based on Critical Parameters to Suppress Ultra-low Frequency Oscillation of Hydroelectric Units" (CN 107086589 A) proposes a method for optimizing the parameters of the governor, which is useful for preventing the overshooting of the primary frequency regulation of hydroelectric units from causing The power grid frequency oscillation has a certain effect, but there are the following problems: 1) Affected by the adjustment mechanism, water flow inertia, mechanical inertia and other factors, compared with the primary frequency regulation of the thermal power unit, the primary frequency regulation of the hydropower unit has a serious hysteresis relative to the frequency change of the grid , the method used to suppress the performance of the primary frequency modulation of the hydroelectric unit does not fundamentally solve the problem of poor quality of the primary frequency modulation of the hydroelectric unit. In fact, under the current technical conditions, there is no effective way to "root" solve the problem Ultra-low frequency oscillation problem; 2) When the frequency of the grid is already oscillating, the adjustment target of primary frequency regulation will fluctuate with the frequency of the grid. Hysteresis, even if the PID parameters of the governor are set to a completely ideal state, it is impossible to avoid the harmful effect of the primary frequency regulation of the hydroelectric unit maintaining or promoting the frequency oscillation of the grid, and the patent does not propose a solution to this situation

[0006] The Chinese patent "Ultra-low frequency oscillation monitoring and its emergency control method based on WAMS" (CN 107872064 A) proposes a method to calculate the primary frequency of a hydroelectric unit by using the multi-signal Prony method through the active power of the unit and the frequency signal of the grid during the grid frequency oscillation process. The frequency modulation has a damping effect on the grid frequency, and the primary frequency modulation function is automatically intervened according to the calculation results, but the Prony algorithm needs to calculate the least square method fitting and high-order algebraic equations to find complex roots, and is very sensitive to the influence of signal noise, which is contrary The simple and reliable principle of the real-time control system of the power system greatly weakens the feasibility of the method provided

[0007] The Chinese patent "A Method for Screening Ultra-Low Frequency Oscillation Sensitive Units in Electric Power System" (CN 107506945 A) provides a method for screening ultra-low frequency oscillation sensitive units, but there are the following problems: 1) There is no provision for establishing a simulation model, and using the simulation model Feasible method for calculating small disturbances; 2) Since it involves rotating equipment such as turbines and generators, and is affected by factors such as water flow inertia and mechanical inertia, a simulation model is built to analyze the governor of a hydroelectric unit, especially when performing quantitative analysis. There is often a large difference from the actual working conditions, and the sensitivity coefficient of the unit obtained is not convincing; 3) The sensitivity of the unit is only judged by constants such as reference capacity, rated capacity, and inertia time, but in the actual oscillation process, the hydroelectric unit is The influence of grid frequency is also affected by important factors such as data acquisition delay and grid frequency oscillation cycle, which further weakens the convincing power of the obtained unit sensitivity coefficient

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