introduction
The stability of power angle, voltage stability, frequency dynamics and its stability in power systems are not isolated phenomena, but different sides of unified physical phenomena that induce each other, and the relationship between them is affected by the network structure and operating state. Impact. Among them, the bus voltage phasor and generator power angle are the main state variables of the system operation, and it is a sign of whether the system can operate stably. If it can be directly measured, it can not only be used for centralized monitoring and control of the dispatch center, but It is used for decentralized on-site monitoring and control, improves the reliability of state estimation, and is more likely to fully realize real-time automatic control of the power system to solve the problem of system stability. Therefore, real-time measurement of the generator's power angle and bus voltage phasor will be the key foundation for the stable monitoring and control of the power system. Through real-time GPS -based phasor measurement, the state quantity of the power grid can be obtained in real time, that is, the historical data and current trajectory of the accurate model of the actual system can be obtained. Since the phase angle involves many fields such as power system monitoring, control and protection, the realization of real-time phasor measurement will promote the development of new methods and theories of power system monitoring, control and protection, etc. Protection opens up a new field.
1 Power angle measurement
1.1 Power angle and power angle measurement
The power angle represents the phase difference between the potential in the generator and the terminal voltage, which represents the electromagnetic relationship of the system, and also indicates the relative spatial position between the rotors of each generator, and this is just to determine whether the generators are operating synchronously. Basis.
Due to the asynchronous operation of the generator or system oscillation, the safety of the generator, transformer and even the entire system will be endangered. The continuous occurrence of the oscillating current will cause the stator of the large turbogenerator to overheat, mechanically damage the ends, and twist the large shaft Shorten operating life. Starting from the objective requirements of power system safety and stability, generator out-of-step and out-of-step predictive protection are necessary. Therefore, the method of obtaining the rotor angle of the generator was once actively explored by many scholars.
1.2 Existing power angle measurement methods
1.2.1 Indirect measurement method
Indirect measurement is to calculate the power angle through known parameters.
The traditional method is that if the horizontal axis synchronous reactance Xd (salient pole machine) or Xq (salient pole machine) is known, after measuring the voltage, current and corresponding φ angle, the power angle can be calculated according to the corresponding vector diagram .
Similarly, if Xd, Xq, X′d, X′q, and X ″ q are known, the δ angles under steady-state, transient, and sub-transient conditions can be obtained, respectively.
To obtain the delta angle with this method, the following two conditions must be met: First, the above parameters must be determined, and these parameters are required to be very accurate; (Synchronous reactance, transient reactance or sub-transient reactance), which generator equivalent model is used for calculation, but in fact, it is difficult to determine; this method has good measurement accuracy in the steady state process, and the measurement error is less than 1 ° However, in the transient process, the power angle calculated using the transient reactance or sub-transient reactance has a certain error. Even using signal processing methods such as FFT cannot solve this problem. And the measurement calculation time is too long, which is not suitable for real-time measurement of real-time stability control system.
The phasor measurement device PMU based on GPS synchronous clock can obtain the generator rotor angle after Fourier transform after sampling the voltage and current, which is also time-consuming.
It can be equipped with different type of storage battery such as lead acid battery, Nickel Cadmium Battery, silver zinc battery, Lithium Ion Battery and other storage batteries, providing various output voltage classes.
Built-in storage battery and charger, equipped with the function of over-charge and over-discharge protection and capacity display. It is used as working power supply for lightings, communications, laptops, and special instruments of emergency working, field working, press interviews, special vehicles and other fields.
Dc Power Supply,110V Dc Power Supply,220V Dc Power Supply,110V Dc Power Supply System
Xinxiang Taihang Jiaxin Electric Tech Co., Ltd , https://www.chargers.be