CN103248071A - Generator set low frequency oscillation monitoring method based on PMU measuring data - Google Patents

Abstract

The invention relates to a generator set low frequency oscillation monitoring method based on PMU measuring data, comprising the following steps of 1) synchronously collecting the dynamic data of each generator by a synchronous phasor measuring unit PMU through the position information of each generator of an electric system provided by a GPS (Global Position System); 2) transmitting the collected data by the PMU to a master station in real time; 3) monitoring the running tendency of a generator set in a real-time updating curve mode by the master station, and if the running tendency has oscillation, automatically pushing the running tendency to an oscillation curve to store the data to a data base; and 4) carrying out low frequency oscillation Prony analysis on power angle data in the dynamic data collected by the PMU through the master station to obtain the amplitude, frequency and damping ratio information of an oscillation signal, and judging the low damping low frequency oscillation according to the oscillation characteristics to provide an important basis for power system stabilizer (PSS) damping compensation. Compared with the prior art, the method has the advantages that the influence of low frequency oscillation on the system can be effectively detected and the like.

Description

Monitoring method of low-frequency oscillation of generator set based on PMU measurement data

technical field

The invention relates to a method for monitoring low-frequency oscillation of a generating set, in particular to a method for monitoring low-frequency oscillation of a generating set based on PMU measurement data.

Background technique

In the power system, when the generators run in parallel through the transmission line, the relative swing between the rotors of the generators will occur under the disturbance, and cause continuous oscillation when there is no damping. At this time, the electrical power and power angle between the generators oscillate, and the power on the transmission line also oscillates accordingly. When the oscillation is serious, the system cannot maintain synchronous operation and the stability is destroyed. Because other oscillation frequencies are very low, generally 0.2-2.5Hz, it is called low-frequency oscillation (also known as power oscillation, electromechanical oscillation). Low-frequency oscillation generally has two modes: when the system connection is weak, the oscillation frequency is low, such as in the range of 0.2-0.5Hz, which is called the interarea mode of the interconnected system, and this oscillation is more harmful , it is the oscillation of one part of the machine group relative to another part of the machine group, once it occurs, it will propagate to the whole system through the tie line; if the electrical distance of the units is small, the oscillation frequency is higher, such as above 1Hz, which is called local or intra-regional inter-unit oscillation Oscillation mode (local mode or plant mode), this kind of oscillation is limited to the area, and has a smaller impact range than the former.

Low-frequency oscillations in power systems occur both at home and abroad. Such low-frequency oscillations or power oscillations often occur on long-distance, heavy-duty transmission lines, and are more likely to occur under the conditions of modern fast, high-top value multiple excitation systems. In the early stage of power system development, the static stability problem usually manifests as asynchronous out-of-synchronization between the generator and the system. However, with the expansion of the system, this instability often manifests as an incremental oscillation between generators (or generator groups), especially on the tie lines of the interconnected system.

In 1969, F.P.Demello et al. used the concept of damping torque to analyze and explain the mechanism of the low-frequency oscillation phenomenon in the single-machine infinite system, and pointed out that the root cause of the continuous or increasing low-frequency oscillation in the power system is due to the A negative damping effect is produced, which offsets the inherent positive damping of the system, making the total damping of the system small or negative. This has greatly improved people's understanding of low-frequency oscillations, and most of the future research work is carried out on this basis. For example, the mechanism analysis of low-frequency oscillations in multi-machine systems is basically the promotion of the concept of single-machine infinite systems. A multi-machine system will have multiple oscillations of different frequencies, and each frequency of oscillation is called a low-frequency oscillation mode, also known as an electromechanical oscillation mode. This oscillation mode is related to the movement of the generator rotor and the electromagnetic circuit, but because the inertia of the generator set is relatively large, it appears as a low-frequency characteristic. It is generally believed that in a system composed of n generators, there are n-1 corresponding electromechanical oscillation modes, but usually only the negative damping and insufficient damping modes are concerned. F.P.Demell believes that each unit or inertial group will have a dominant effect on one or more oscillation modes, and the damping of a certain unit can have a dominant effect on certain specific oscillation modes, which has an important impact on later research. Correlation characteristics" or "decoupling relationship".

This is the generally accepted low-frequency oscillation underdamping mechanism, that is, in some specific cases, the negative damping effect provided by the system offsets the positive damping of the system motor, excitation winding and machinery, so that the total damping of the system is very small or negative. . When the system is disturbed under the condition of negative damping, the disturbance is gradually amplified, which causes low-frequency oscillation of power. Heavy duty lines, modern fast excitation and excitation systems with high ceiling multiples are the main causes of negative damping in the system.

Contents of the invention

The object of the present invention is to provide a method for monitoring low-frequency oscillation of a generating set based on PMU measurement data in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A method for monitoring low-frequency oscillations of generator sets based on PMU measurement data, characterized in that the method comprises the steps of:

(1) The synchrophasor measurement unit PMU uses the position information of each generator in the power system provided by the GPS system to collect the dynamic data of each generator synchronously;

(2) The PMU transmits the collected data to the master station in real time;

(3) The master station monitors the operation trend of the generator set in the form of a real-time updated curve. If the above-mentioned operation trend oscillates, it will automatically push the operation trend oscillation curve and save the data to the database;

(4) The master station performs low-frequency oscillation Prony analysis on the power angle data in the dynamic data collected by the PMU, obtains the amplitude, frequency and damping ratio information of the oscillation signal, and judges the weakly damped low-frequency oscillation according to these oscillation characteristics. It provides an important basis for the PSS damping compensation of the power system stabilizer.

The dynamic data includes power angle, active power, reactive power, voltage and frequency.

The operating trends described include dynamic curves for active power, reactive power, voltage and frequency.

Compared with the prior art, the present invention can effectively detect the influence of low-frequency oscillation on the system, and improve the safety and reliability of the system. At the same time, the Prony algorithm is used to analyze the power angle data, and the signal amplitude, phase, The damping factor, frequency and other information do not need to be obtained from the frequency domain response, and the amount of calculation is greatly reduced.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments.

A method for monitoring low-frequency oscillations of generator sets based on PMU measurement data, the method comprising the steps of:

(1) The synchrophasor measurement unit PMU uses the position information of each generator in the power system provided by the GPS system to collect the dynamic data of each generator synchronously;

(2) The PMU transmits the collected data to the master station in real time;

(3) The master station monitors the operation trend of the generator set in the form of a real-time updated curve. If the above-mentioned operation trend oscillates, it will automatically push the operation trend oscillation curve and save the data to the database;

(4) The master station performs low-frequency oscillation Prony analysis on the power angle data in the dynamic data collected by the PMU, obtains the amplitude, frequency and damping ratio information of the oscillation signal, and judges the weakly damped low-frequency oscillation according to these oscillation characteristics. It provides an important basis for the PSS damping compensation of the power system stabilizer.

The dynamic data includes power angle, active power, reactive power, voltage and frequency.

The operating trends described include dynamic curves for active power, reactive power, voltage and frequency.

The methods for measuring power angle data include: 1) an indirect measurement method, and 2) a measurement using a generator speed signal.

The indirect measurement method is to collect the terminal voltage and terminal current of the generator in real time, and then calculate the position of the rotor with the help of the model of the generator. The said measurement using the generator speed signal refers to using a tachometer to measure the power angle in real time.

The Prony method described is to fit equally spaced sampled data with a linear combination of a set of exponential terms. The exponent item includes two parts of amplitude and exponent factor. The specific process is as follows: first, the original data sequence is preprocessed by using a DC-removing and low-pass filter, and the low-pass filter can select an appropriate filter according to the performance index given in advance, and then use re-sampling and selection sequence The length further reduces the effects of noise.

Claims (3)

1. the generating set low-frequency oscillation monitoring method based on the PMU metric data is characterized in that this method comprises the steps:

(1) synchronous phasor measurement unit PMU utilizes the positional information of each generator of electric power system that gps system provides, and each generator dynamic data is gathered synchronously;

(2) PMU is sent to main website with the data in real time that collects;

(3) main website monitors the operation trend of generating set with the curve mode of real-time update, if vibration appears in above-mentioned operation trend, and propelling movement trend oscillating curve automatically, and data are saved to database;

(4) the merit angular data in main website the dynamic data that PMU is collected is carried out low-frequency oscillation Prony and is analyzed, draw amplitude, frequency and the damping ratio information of oscillator signal, and carry out the judgement of underdamping low-frequency oscillation according to these oscillation characteristicses, for power system stabilizer, PSS PSS damping compensation provides important basis.

2. a kind of generating set low-frequency oscillation monitoring method based on the PMU metric data according to claim 1 is characterized in that described dynamic data comprises merit angle, active power, reactive power, voltage and frequency.

3. a kind of generating set low-frequency oscillation monitoring method based on the PMU metric data according to claim 2 is characterized in that described operation trend comprises the performance graph of active power, reactive power, voltage and frequency.