CN105548811A - Electric-power-system subsynchronous resonance and severe degree quantification identification method - Google Patents

Abstract

The present invention proposes a method for quantifying subsynchronous resonance of a power system and its severity. It detects the voltage at both ends of the capacitor in series, and calculates the ratio DEG between the half cycle time of the capacitor voltage and the half cycle time of the normal 50Hz system. When the ratio DEG is greater than 102% , it is considered that a subsynchronous resonance occurs; set the flag SIG of the subsynchronous resonance to 1, otherwise set the flag SIG to 0. Use the proportion DEG as the weight to time-integrate the sub-synchronous resonance mark SIG to obtain the quantitative index INDEX of the severity of the sub-synchronous resonance in the power system; corresponding stabilization controls. The invention can quickly and effectively judge the power system subsynchronous resonance and its severity without complex calculation, and can provide a powerful tool for the analysis, research and risk assessment of the power system subsynchronous resonance, and has strong engineering practicability.

Description

Quantitative Discrimination Method of Power System Subsynchronous Resonance and Its Severity

technical field

The invention relates to a quantitative discrimination method for power system subsynchronous resonance and its severity.

Background technique

Due to the distribution of primary energy in my country, the cross-domain transmission of electric energy is caused, and the transmission distance is long and the stability is weak. Series compensation technology is an economical and effective method to shorten the electrical distance of AC transmission, increase line transmission capacity and improve system transient stability. In addition, the cost and expropriation problems of my country's transmission corridors are becoming increasingly prominent, so the availability of series compensation will be greatly improved. improve. One of the problems that the series compensation will cause to the operation of the power system is that it may cause subsynchronous resonance, which will lead to torsional vibration of the steam turbine generator shaft and electrical oscillation lower than the normal system frequency, seriously affecting the safety of the power grid. Therefore, the in-depth analysis and research of subsynchronous resonance in power system is very important.

In the existing analysis and research on subsynchronous resonance of power system at home and abroad, how to judge the occurrence of subsynchronous resonance in large power systems, especially the severity of subsynchronous resonance, there is still a lack of quantitative identification methods and quantitative identification indicators. In fact, individual transient subsynchronous resonances do not do much harm to the power system. However, the existing subsynchronous resonance identification methods cannot quantify the severity of subsynchronous resonance in order to conduct in-depth and comprehensive quantitative analysis and risk assessment of power system subsynchronous resonance. Therefore, how to judge the severity of power system subsynchronous resonance and give quantitative indicators has practical engineering significance.

Contents of the invention

The purpose of the present invention is to propose a quantitative discrimination method for power system subsynchronous resonance and its severity. The discrimination method forms a power system subsynchronous resonance severity index through a specific operation through the detected voltage at both ends of the series capacitor. Through the Indexes are used to quantify the severity of power system subsynchronous resonance, so as to conduct analysis, research and risk assessment of power system subsynchronous resonance.

In order to achieve the above object, the technical solution of the present invention is to provide a quantitative discrimination method for power system subsynchronous resonance and its severity, including the following process:

Sensing the voltage across the series capacitor;

Calculate the ratio of the half-cycle time of the capacitor voltage to the half-cycle time of the standard 50Hz system DEG=t _{Vcap_half} /t _stand ; where, t _{Vcap_half} is the half-cycle time of the capacitor voltage; t _stand is the half-cycle time of the standard 50Hz system;

When the ratio DEG is greater than 102%, it means that subsynchronous resonance occurs.

Preferably, when the judgment ratio DEG is greater than 102%, set the subsynchronous resonance flag SIG=1;

When the judging ratio DEG is not greater than 102%, it means that the sub-synchronous resonance does not occur in a normal state, so that the sub-synchronous resonance flag SIG=0.

Preferably, the proportion DEG is used as a weight, and the subsynchronous resonance flag SIG is time-integrated to obtain a quantitative index INDEX=∫(DEG·SIG)dt representing the severity of the power system subsynchronous resonance;

When the quantitative index INDEX is greater than 0.5, it means that a subsynchronous resonance has occurred that affects the stability of the system, and the subsynchronous resonance control measure is enabled.

Preferably, if the quantitative index INDEX is not greater than 0.5, the voltage across the two terminals of the series capacitor is re-detected.

Compared with the prior art, the method and procedure for judging the subsynchronous resonance and its severity of the power system proposed by the present invention can quickly and effectively judge the subsynchronous resonance and its severity of the power system without complicated calculations , which can provide a powerful tool for the analysis and research and risk assessment of power system subsynchronous resonance, and has strong engineering practicability.

Description of drawings

Fig. 1 is a schematic diagram of a process for identifying subsynchronous resonance and its severity in a power system.

detailed description

The method for quantifying and discriminating power system subsynchronous resonance and its severity proposed by the present invention is as follows:

Detect the voltage at both ends of the capacitor in series. Under normal circumstances, the half-cycle time of the capacitor voltage should be equal to the half-cycle time (10ms) of the standard 50Hz system. Calculate the ratio DEG of the half-cycle time of the capacitor voltage to the half-cycle time of the normal 50Hz system. When the ratio DEG is greater than 102%, it is considered that sub-synchronous resonance occurs; set the flag SIG of sub-synchronous resonance. When SIG=1, it means that sub-synchronous resonance occurs , when SIG=0, it means that subsynchronous resonance does not occur, which is a normal condition.

Moreover, the ratio DEG of the half cycle time of the capacitor voltage to the half cycle time of the normal 50Hz system can be used to indicate the severity of the instantaneous subsynchronous resonance. When the ratio DEG is larger, the instantaneous subsynchronous resonance is considered to be more serious.

For this reason, considering the factor of the subsynchronous resonance duration, the proportion DEG is used as the weight to perform time integration on the subsynchronous resonance flag SIG to obtain the quantitative index INDEX of the severity of the subsynchronous resonance in the power system; the subsynchronous resonance of the power system is judged according to the quantitative index INDEX Severity, if INDEX is less than 0.2, it is considered as a mild subsynchronous resonance, which has little impact on the stability of the power system; if INDEX is greater than 0.5, it is considered a serious subsynchronous resonance, which has a greater impact on system stability. Appropriate stabilization control measures are required.

According to the quantitative discrimination method of power system subsynchronous resonance and its severity above, the identification process of power system subsynchronous resonance and its severity can be formulated. Figure 1 shows the identification process of power system subsynchronous resonance and its severity:

S1. Detect the voltage at both ends of the series capacitor;

S2. Let t _{Vcap_half} be the half cycle time of the capacitor voltage;

Let t _stand be the normal 50Hz half cycle time (10ms in this example);

Calculate the ratio DEG=t _{Vcap_half} /t _stand .

S3. Determine whether the ratio DEG is greater than 102%:

If the judgment is "Yes", it is considered that sub-synchronous resonance occurs, and the flag SIG of sub-synchronous resonance is set to 1;

If the judgment is "No", it is considered to be in a normal state where subsynchronous resonance does not occur, and the flag SIG=0.

S4. Calculate the quantitative index INDEX=∫(DEG·SIG)dt of the severity of synchronous resonance

S5. Compare the quantitative index INDEX with the set threshold LIMIT; in this example, the set threshold LIMIT is 0.5, that is, determine whether the quantitative index INDEX is greater than 0.5:

If the judgment is "Yes", after starting the relevant subsynchronous resonance control function, the judgment process ends;

If the judgment is "No", re-execute S1 to detect the voltage across the capacitor in series.

The method and process for judging the subsynchronous resonance and its severity of the power system proposed by the present invention can quickly and effectively judge the subsynchronous resonance of the power system and its severity without complicated calculations, and can be used for the subsynchronous resonance of the power system. The analysis research and risk assessment of resonance provide a powerful tool with strong engineering practicability.

The present invention is proposed on the basis of a large number of calculation conclusions of domestic series compensation system subsynchronous resonance research, and the quantitative judgment method of power system subsynchronous resonance and its severity has been verified by a large number of theoretical calculations and engineering examples .

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present invention. Various modifications and alterations to the present invention will become apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (4)

1. a quantitative appraisal method for hyposynchronous resonance of power system and the order of severity thereof, is characterized in that, comprises following process:

Detect the voltage at series capacitor two ends;

The time of calculable capacitor voltage half cycle and the ratio DEG=t of half cycle time of standard 50Hz system _{vcap_half}/ t _stand; Wherein, t _{vcap_half}for the time of condenser voltage half cycle; t _standfor the time of standard 50Hz half cycle;

When ratio DEG is greater than 102%, represents and subsynchronous resonance occurs.

2. quantitative appraisal method as claimed in claim 1, is characterized in that,

When judging that ratio DEG is greater than 102%, make subsynchronous resonance mark SIG=1;

When judging that ratio DEG is not more than 102%, representing and being in the normal condition that subsynchronous resonance does not occur, making subsynchronous resonance mark SIG=0.

3. quantitative appraisal method as claimed in claim 2, is characterized in that,

Using ratio DEG as weight, time integral is carried out to subsynchronous resonance mark SIG, obtain quantizating index INDEX=∫ (DEGSIG) dt representing the hyposynchronous resonance of power system order of severity;

When quantizating index INDEX is greater than 0.5, represents and there occurs the stable subsynchronous resonance of influential system, then enable subsynchronous resonance control measure.

4. quantitative appraisal method as claimed in claim 3, is characterized in that,

If when quantizating index INDEX is not more than 0.5, again the both end voltage of series capacitor is detected.