National Power Dispatching and Control Center

Beijing, China

National Power Dispatching and Control Center

Beijing, China

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Guan M.,State Grid Corporation of China | Cheng J.,State Grid Corporation of China | Wang C.,National Power Dispatching and Control Center | Hao Q.,Shandong University | And 3 more authors.
IEEE Transactions on Power Systems | Year: 2017

Nowadays interconnections of non-synchronous AC grids with VSC-HVDC links become attractive in preventing cascading outages. To share the spinning reserves, the VSC-HVDC link is expected to balance the frequencies of the interconnected grids under tolerable disturbances. Based on the synchronous generator emulation control (SGEC) strategy, this paper presents a communication-free scheme for the frequency regulation of interconnected grids with a VSC-HVDC link. Under a tolerable disturbance, the scheduled powers of the rectifier and the inverter are changed to their actual powers, respectively. As a result, the grid frequencies could be balanced and the adjacent grid will provide frequency support to the disturbed grid. If the disturbance becomes larger, the scheduled powers of the two converters are changed until the maximum or minimum limits and the frequency support to the disturbed grid is limited. Thus, the large disturbance results in a deeper frequency drop in the disturbed grid, which could be arrested by its under-frequency load shedding. As a result, the disturbance propagating to the adjacent grid is suppressed, which does not jeopardize security. The frequency regulation scheme coordinates well with the automatic generation control (AGC) of the grids. Time-domain simulation studies are performed in the PSCAD/EMTDC software environment. © 1969-2012 IEEE.


Xie X.,Tsinghua University | Liu H.,Tsinghua University | He J.,National Power Dispatching and Control Center | Zhang C.,Tsinghua University | Qiao Y.,Goldwind Science and Technology Co.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2016

Recently, sustaining power oscillation within the range of subsynchronous frequency was observed in many direct drive permanent magnet synchronous generator (D-PMSG)-based wind farms in China. Different from the previous oscillation events, there is no series compensation in nearby power grid. To investigate the mechanism and characteristics of this emerging subsynchronous oscillation (SSO) issue, the equivalent model of the multiple D-PMSGs interfaced with AC power grid was established. Both time-domain simulation and small-signal analysis were conducted to analyze the mechanism of SSO problem. The impact on its characteristics from many factors was also analyzed, including short-circuit capacity, loading level and online number of D-PMSGs, etc. The analyses results indicate that there exists an SSO mode when multiple D-PMSGs are connected to a weak AC system. These D-PMSGs behave as a "capacitive reactance with a negative resistance" at the SSO mode, whose interaction with the AC grid (considered as inductance) constitutes the resonance circuit. Negative resistance effect will lead to risky power oscillation phenomenon. Finally, potential hazard and precautionary measure of such SSO problem were discussed. © 2016 Chin. Soc. for Elec. Eng.


Li Z.-W.,State Grid Electric Power Research Institute of China | He J.-B.,National Power Dispatching and Control Center | Fang Y.-J.,State Grid Electric Power Research Institute of China | Li W.,State Grid Electric Power Research Institute of China | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

According to the current Guide on Security and Stablility for Power System, the reclosing moment of power plant transmission lines directly affects the power plant transmission ability. This paper establishes a mathematical model of system transient stability affected by reclosing moment. The system stability characteristics considering reclosing time is studied based on Extended Equl-Area Criterion (EEAC) theory. An approach to setting the reclosing time considering transient stability is proposed. The actual power system simulation shows that it can identify the reasonable range of reclosing time quickly and ensure that the setting value of reclosing time meets the system transient stability requirement.


Zhu X.,North China Electrical Power University | Liu W.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Wu X.,Anhui Electrical Power Dispatching and Communication Center | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

To improve the fitting degree between analysis results and actual situation, the idea of dynamic power flow was introduced into probabilistic load flow (PLF) analysis to research the model and algorithm of PLF considering frequency modulation. Based on processes of frequency response in real system, the analytical model of dynamic unbalance power distribution was established by use of piecewise functions. And the model was combined with traditional PLF model to establish the model of PLF considering frequency modulation. The proposed PLF model was modified according to the impact of insufficient frequency modulation on unbalance power distribution. To ensure the practicality of the model solution, a hybrid method was proposed, which is simple and easy to realize. Compared with conventional analytical method, the proposed method has more powerful capacity of random processing. Compared with conventional simulation method, the solving speed can be greatly improved while keeping higher calculation accuracy. The effectiveness of the proposed model and method was verified via IEEE 24 bus system tests. © 2014 Chin. Soc. for Elec. Eng..


He J.,National Power Dispatching and Control Center | Li M.,National Power Dispatching and Control Center | Jun Y.,China Electric Power Research Institute | Qing C.,National Power Dispatching and Control Center | And 2 more authors.
POWERCON 2014 - 2014 International Conference on Power System Technology: Towards Green, Efficient and Smart Power System, Proceedings | Year: 2014

Voltage grade and capacity of HVDC transmission in China continue to increase these years. With the commissioning of UHV-HVDC transmission, voltage grade of HVDC has reached ± 800kV, and transmission capacity of single HVDC had reached 8000MW. Thus AC/DC interaction and its effects on system safety become a focal point on power system operation area. In this paper, based on operation practice of a large power grid and theory analysis, operation characteristics of HVDC with massive power transmission are illustrated, including over voltage control and multi-infeed HVDC system problems. A standpoint is proposed in this paper, that to build a strong sending and receiving AC power grid, is the fundamental measures to ensure grid safety with large scale power HVDC transmission. © 2014 IEEE.


He J.,National Power Dispatching and Control Center | Zhuang W.,National Power Dispatching and Control Center | Xu T.,National Power Dispatching and Control Center | Huo C.,Northwest Power Dispatching and Control Sub Center | Jiang W.,State Power Economic Research Institute
Dianwang Jishu/Power System Technology | Year: 2016

Transient overvoltage is a common phenomenon in process of HVDC commutation failure or blocking. Overvoltage amplitude is strongly related to transmitted power. If large amount of wind farms are located adjacent to converter station, this overvoltage phenomenon may lead to wind farm tripping and chain reaction. In this paper, principle and impact factors of HVDC transient overvoltage are analyzed, and mechanism of wind power tripping caused by overvoltage is illustrated. Both are verified with actual case analysis and simulation results. Finally, strategies for preventing cascading tripping of wind farms adjacent to HVDC converter station are proposed, such as improving short circuit capacity, strengthening grid structure and improving voltage adaptability of wind farms. © 2016, Power System Technology Press. All right reserved.


He J.,National Power Dispatching and Control Center | Zhang J.,National Power Dispatching and Control Center | Li M.,National Power Dispatching and Control Center | Li W.,China Electric Power Research Institute | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

During the development process of HVDC in China ,several HVDC projects are faced with the problem that the sending system may change into islanded mode. Stability problem of governor should be paid more attention in an islanded sending system since it has resulted in an abnormal frequency oscillation phenomenon in island experiments of Jinsu HVDC project. In this paper, a transfer function model was established to analyze the governor stability in an islanded HVDC sending system. Then sensitivity analysis for governor stability was given in frequency domain. A decoupling coordinated design approach of governor and HVDC frequency controller was proposed based on the sensitivity analysis results. The abnormal frequency oscillation phenomenon was analyzed and the controllers in Jinsu HVDC islanded sending system were redesigned. The analysis and design approaches were verified by the field test of Jinsu HVDC link.


Wang G.,China Electric Power Research Institute | Yu Z.,National Power Dispatching and Control Center | Zhang Y.,National Power Dispatching and Control Center | Li Y.,China Electric Power Research Institute | And 3 more authors.
Dianwang Jishu/Power System Technology | Year: 2016

Recently, ultra-low frequency oscillation (ULFO) emerges in DC island sending system and isolated power system, especially where high proportion of hydro-turbine generators exists. To find oscillation reasons, this paper established a typical DC island sending system, and analyzed ULFO stability with eigenvalue analysis and time domain simulation method to quickly troubleshoot negative damping oscillation modes caused by prime mover and governor. Simulations indicate that if turbine governor works, ULFO may appear in power system and damping ratio will decrease when generator governor operates at a higher speed. Eigenvalue analysis shows that real parts of eigenvalues are located in right side of complex plane and not stable. Study indicates that governor control mode and parameters, such as water hammer effect time constant, frequency gain, PID parameters, can significantly change eigenvalue positions in complex plane. Governor parameter optimization based on sensitivity analysis can enhance mode damping ratio, but with drawback of reducing primary frequency regulation ability of generator. Frequency limit controller (FLC) can regulate DC power or DC current in a fast and stable way, beneficial to primary frequency adjustment of governor optimization. Dead band of FLC should not be too wide and its value can be set with reference of primary frequency regulation dead zone of generator. © 2016, Power System Technology Press. All right reserved.


He J.,National Power Dispatching and Control Center | Wan L.,China Electric Power Research Institute | Huo C.,Northwest Power Dispatching and Control Sub Center | Chang Q.,National Power Dispatching and Control Center
Dianwang Jishu/Power System Technology | Year: 2014

Overvoltage control in high capacity HVDC transmission is such a problem, to which attentions are widely paid. Due to the concentrated compensation with large-amount of reactive power, the voltage of the converter station will sharply rise in a short-term after the DC disturbance or DC block, so that it is necessary to carry out the preventive control to avoid the destruction of equipment insulations or the occurrence of secondary fault caused by overvoltage. When post-DC block abnormal overvoltages occur in actual HVDC transmission systems under atypical operating conditions, the voltage rising exceeds that in conventional operating conditions and it brings the risk to the power grid security. The detailed analysis on the mechanism leading to abnormal overvoltage is performed and the effectiveness of the mechanism analysis is validated by simulation. On this basis the atypical operating conditions, in which the risk due to abnormal overvoltage exists, are summarized to provide for reference to the design of over-voltage and insulation coordination and to the operation and control of AC/DC hybrid power grid as well. ©, 2014, Power System Technology Press. All right reserved.


Zhang P.,North China Electrical Power University | Bi T.,North China Electrical Power University | Yang Q.,North China Electrical Power University | He J.,National Power Dispatching and Control Center
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2015

Parallel-connected no-identical machines with close torsional frequencies as large power plants are usually built in phases. In this paper, the mechanism, characteristic and risks of subsynchronous oscillation (SSO) of parallel connected generators with close torsional frequencies were studied. Firstly, the mechanism and characteristics of Gen-Grid Mode and Gen-Gen Mode were revealed based on eigenvalue analysis. Furthermore, the SSO phenomenon in an actual system was explained reasonably and clearly. On this basis, the effects of compensation level and array mode of generators on the two modes were investigated, and the risk law of parallel-connected generators with close torsional frequencies was revealed. Digital simulation was conducted to verify the analysis conclusions. © 2015 Chinese Society for Electrical Engineering.

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