Voltage Stability Analysis of Power System Automation System Chen Jinfu1, Peng Feijin, Wang Xinghua, Duan Xianzhong, Zhang Yulin2, Wang Daguang2 (1. Department of Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; 2 Fujian Electric Power Research Institute, Fuzhou 3511(1), China) Sexual analysis, and discussed the voltage stability of the system after (n * 1) test; the transient voltage stability of the system was also simulated. The voltage stability of the power system in Fujian Province is pointed out, and some suggestions for preventing system voltage instability are proposed.
Studying the voltage stability of power systems is of great significance for the safe and stable operation of power systems. For the power system of Fujian Province, the static voltage stability analysis of the system is carried out by using the voltage stability sensitivity index and the margin index. 1 Several typical faults or steady state after operation are analyzed, and the transient voltage stability of the system is also carried out. In order to provide information for preventing and controlling voltage instability and ensuring safe operation of the system, several suggestions for pre-visiting system voltage instability are also provided.
1 Static voltage stability indicators introduced Currently, the safety indicators have been proposed: sensitivity index, trend Jacobian matrix singular value index, minimum mode eigenvalue index, distance index between power flow multi-solution in load state space, threshold voltage index and margin index. The sensitivity index is based on the qualitative physical concept, and the stability problem is analyzed by using the relationship of certain quantities in the system, which has been widely used. 100%. Among them: :cr is the ultimate active load of the system, and P0 is the initial active load of the system.
2 Static voltage stability analysis For a long time, the power system of Fujian Province has a pattern of transmission from south to south and long-distance transmission. Many malignant voltage crashes in the world have shown that such power systems that carry large amounts of electrical energy over long distances are prone to voltage instability. In this paper, a lot of calculations are made on this table. Table 1 and Table 2 list the static voltage stability margin indicators in each typical operation mode and (the voltage stability margin (Kp) load in the typical state of n table 1 is heavy and lacking. Sufficient dynamic reactive support. In normal area, once instability occurs, it may cause system collapse, saving more than 80% of the load. When the system is disturbed, it will pose a great threat to the safe and stable operation of the system. Long-term (greater than 1 s) low-voltage process (this is mainly due to the large-scale reactive power of the Daguyu Power Plant and Houshi Power Plant to maintain the dynamic load of the southern part of the system) and the voltage can still be in the notebook3 zone voltage.鲤 has a great effect. Due to the lack of power supply in the southern region, Ms slows back to normal operation level: http:// Note: 20SD1: Fujian 20 (1) summer generous 20SD2: Fujian 20 (1) summer large mode (less open Hydropower, after the stone double machine full load) 20WX1: Fujian 2 (1) 0 years winter small square 20WX2: Fujian 20 years winter small way (less water, less stone single full load) Table 2 (n-1) test voltage Qualitative Margin Index (KP) Type Margin Type Margin Type Margin Type Margin Note: a1: Shukou 1 suburban tail 5 (1) kV line disconnected; a2: Suburb tail one Quanzhou 5 (1) kV line disconnected; a3: Hou Shiyi Xiamen 5 (1) kV Line disconnected; a4: Tanpingyishan 220kV line disconnected; a5: Shukou one horse station 220kV line disconnected; a6: Yuyu cut a machine u operating mode with the same as Table 1.
Table 3 Typical operating mode load node voltage stability ranking Gushan U*梧 Road U-. Hui'an L (4. Ganzi U-. Guxian U-. Donghai U-5. Xingbei U-5. Fujian Power System South The region is a region with weak voltage stability. In the sensitivity analysis and margin analysis, the voltage stability weak nodes are concentrated in the southern substation. Under the centralized operation mode of the node with poor voltage stability, the partial reactive power of the Yuyu Power Plant and the Houshi Power Plant is maintained. Standby is of particular importance for maintaining voltage stability in the southern region and improving anti-jamming capability.
Among the 6 kinds of operations listed, according to the operation type, the influence is in turn, the influence of the cutting machine is the largest, the 500kV line exits the operation, the 220kV line has the least impact, and the voltage stability margin is under the normal state. The indicators differ very little. When the system was cut, the dynamic voltage support capability of the system was greatly weakened, especially in the 20SD2 mode. At this time, the Houshi Power Plant only started 2 units, running at full load, and having less reactive power. When the Yuyu Power Plant cuts the machine, the system's voltage stability margin is reduced to 7.4%. If other power system accidents occur again, it will seriously threaten the safe operation of the grid. The exit operation of the 500kV line also has a large impact on the system voltage stability, and the voltage stability margin index is significantly reduced, but in most cases will not lead to system instability.
3 Transient voltage stability analysis The power system is a dynamic large system. Under normal operating conditions, all components in the system are in a dynamic equilibrium, that is, steady state operation. External disturbances can destroy this balance, and whether the component can maintain its stability depends on the size of the external disturbance and the stability of the component itself. Therefore, only static analysis can not fully reflect its stability, and it is necessary to analyze the voltage stability of the system in the transient process.
In the transient stability calculation, most generators adopt E, model, and consider the role of excitation regulation system and prime mover speed control system. A few generators adopt E; model, the camera adopts E model, and the load adopts equal-value motor plus constant Impedance model. The operation mode is 4 ways (see the note in Table 1). The fault type is 500kV line three-phase short circuit, unit demagnetization and so on. 3. Impact of 1500kV line short circuit on transient voltage stability With the completion of the post-fired power plant and the formation of 500kV system in Fujian Province, the power distribution of Fujian Province will tend to be balanced, and the power ratio of Nortel South will gradually decrease. The stability level of the whole network has been greatly improved, especially the voltage stability level has been increased more obviously. Under the short-circuit single-fault condition of 500kV line, the voltage of the whole network is at a relatively stable level.
3.2 Influence of dynamic load on transient voltage stability The ratio of dynamic and static load in transient calculation using 4:6 may not meet the current actual situation of Fujian power system. In the industrial load, most of them are dynamic loads; in the civil load, in the summer mode, the dynamic load of air conditioners, refrigerators, etc. is very large, especially at the midday peak and the evening peak. Since the dynamic load ratio has a large influence on the voltage stability, a special analysis is performed as shown in (a) and (b). Through calculation, it is found that only when the dynamic load accounts for the whole (b) the dynamic and static characteristic ratio of the load in the demagnetization system of a unit in the Yuyu Power Plant is 8:2. The voltage stability under the mode of 3.3SD2 is the effect of the loss of the unit on the transient voltage stability. The southern power grid, especially in the Xiamen, Ningbo and Quanzhou areas, has a large load in the province's power grid. Therefore, it is very important to maintain the reactive power of the Yuyu Power Plant and the Houshi Power Plant as the dynamic reactive standby in the southern region. If the Houshi Power Plant exits the operation, it must ensure the normal operation of the Yuyu Power Plant, and the reactive power output of the Yuyu Power Plant is not needed to adjust the static voltage level during normal operation of the system to ensure that the system is disturbed by 0 inches. More reactive power is used to support the voltage level in the southern region and prevent voltage instability in the southern power grid. It can be seen that in the case of demagnetization of the Yuyu Power Plant unit, the voltage will be unstable. Therefore, this should be avoided as much as possible. On the one hand, the working reliability of the excitation system should be improved and the excitation system accident should be reduced; on the other hand, a dynamic reactive power compensation device can be installed in the system to improve the voltage stability during the dynamic process of the system.
Comparison and (b) can be seen that the access operation of Houshi Power Plant will be beneficial to increase the voltage in the southern part of Fujian Power Grid.
3.4 Influence of Excitation Multiplex of Excitation System on Transient Voltage Stability Here, we mainly discuss the strong excitation multiple of the excitation system of the post-stone unit. The selected operation mode is the summer. The voltage problem that the Fujian Power Grid will face is mainly manifested in the small load operation mode. The system high voltage problem, in the current situation, can only be achieved by multi-cast reactor or unit phase-in operation.
From the perspective of the whole system, the voltage stability in the southern part of Fujian Power System is still relatively fragile. In normal operation, it should be ensured that the reactive power output of Houshi Power Plant and Shuyu Power Plant has a certain capacity as a backup, so that when the system is disturbed. It can provide support for the voltage of the southern power grid, prevent voltage collapse accidents in the southern power grid, and ensure the safe operation of the entire system.
The role of the power grid (mainly (M system)) and the effect of shadow transient voltage stability is not obvious. Due to the high transient voltage stability level of Fujian Power Grid, the strong excitation multiple of the excitation system of the back stone unit is improved. In view of the above situation, Fujian Power Grid should mainly consider the following measures to control the voltage: the loss of magnetism of the unit has a great influence on the voltage stability of the local area, and the reliability of the excitation system should be improved, and the excitation system accident should be reduced. The power grid should ensure that at least two units are connected to the grid and that there is a certain reactive power output as a backup. This can improve the voltage stability of the southern power grid to a certain extent, prevent voltage instability in the southern power grid, and endanger the safe operation of the entire system. .
The previous analysis shows that dynamic reactive standby is extremely important to maintain system voltage stability. Among the several types of failures discussed, the Yuji cutting machine has the greatest impact on system voltage stability when the reactive power supply is reduced. This shows that dynamic reactive standby is very important for system voltage stability after failure. In the future, when appropriate, the dynamic reactive power compensation device should be installed at the appropriate position of the southern power grid (generally at the weak busbar location) to dynamically compensate the southern power grid to reduce the dependence of the southern power grid on the reactive power of the generator. Improve voltage stability during transients in the southern region.
Carry out the phase-in operation test of some units, so that in the small mode, when the system voltage is too high, the unit's phase-in operation will absorb the appropriate amount of reactive power and reduce the voltage level of the whole system.
5 Conclusion Static voltage stability analysis shows that the southern part of Fujian Power Grid is a region with weak voltage stability. Whether it is from the voltage collapse accidents that have occurred in the world or from the analysis of the Fujian power system, when a system transmits a large amount of power over a long distance, the voltage stability of the receiving end is relatively weak. Especially when the region formed by the receiving end concentrates the node with poor voltage stability, once the instability occurs, it is easy to cause a chain reaction, causing the system to collapse, and the loss to the system and the user will be enormous.
In the several fault situations discussed in the static voltage stability analysis, the system's reactive power supply has the greatest impact on the system's voltage stability when the system is reduced, indicating that the system's dynamic reactive standby is stable after maintaining the system fault. Sex is extremely important.
From the calculation results of the four operating modes, the transient voltage stability problem of Fujian Power Grid is not very prominent. The effects of various disturbances on voltage stability under different operating modes are similar, that is, the four operating modes are under various disturbances. The stability is basically the same. With the completion of the Fujian 500kV system, the voltage stability of the system has been greatly improved.
The effect of dynamic load and unit loss on the transient voltage stability of the system again shows that sufficient dynamic reactive backup plays an important role in maintaining the voltage stability of the system. In order to alleviate this problem, a dynamic reactive power compensation device can be installed in the system, and the reliability of the excitation system should be improved to ensure the normal operation of the unit.
In the past two decades, many voltage instability and malignant voltage collapse accidents in various countries in the world have made the problem of voltage stability increasingly prominent. Under the current situation that China's power system is developing to high-voltage large-scale power grids and long-distance power transmission, the threat of voltage stability cannot be ignored. Drawing on foreign experience and lessons, it is an urgent task to analyze the voltage stability of China's power system.
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