National Power Dispatching and Control Center

Beijing, China

National Power Dispatching and Control Center

Beijing, China
SEARCH FILTERS
Time filter
Source Type

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 | Liu W.,Tsinghua University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2017

The power oscillation induced by the interactions between power converters and AC/DC power grids is an important stability problem faced by grid-connected renewable energy generation systems (GREGSs). Small-signal modeling is the basis for the analysis of such a problem. But the large quantities of converters with different structures, parameters and “black (grey)-box” control systems make it very difficult for the conventional method to handle the issue of system modeling. A methodology of small-signal impedance (admittance) network modeling is proposed to address the issue. With each component represented with an impedance or admittance model, a GREGS as a whole can be modeled as the network of impedance or admittance by interconnecting all the individual impedances (admittances) according to the topology of the grid. Such an impedance (admittance) network model can be further aggregated into a lumped impedance (admittance), with which the features of the oscillation could be quantified given the frequency-dependent characteristics of the lumped impedance (admittance). Case studies on the Guyuan series-compensated wind power system have verified the effectiveness of the proposed modeling method. © 2017 Automation of Electric Power Systems Press.


Li J.,North China Electrical Power University | Bi T.,North China Electrical Power University | Yu Z.,National Power Dispatching and Control Center | Zhang P.,North China Electrical Power University | Xiao S.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2017

In this paper, transfer functions for PLL (phase-locked loop) and d/q decoupling control system are presented respectively. With small signal method, for the case when a subsynchronous frequency component is fed into PLL and d/q decoupling control system as inputsignal, expressions of output signals are derived. Frequency transformation relationship between input and output signals and amplitudes of multiple output components of sub- and super-synchronous frequency are then discussed in detail. Simulation results and practical wave recording data from PMU(phasor measurement unit) validate theoretical analysis. With the theoretical analysis, existence of multiple sub- and super-synchronous frequency components in PMSG collecting bus is explained, and the basis of suppression of main subsynchronous frequency componentsare given. © 2017, Power System Technology Press. All right reserved.


Yu M.,North China Electrical Power University | Xie H.,China Electric Power Research Institute | Song W.,North China Electrical Power University | Wang H.,State Grid Corporation of China | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2017

With the increasing penetration of wind power, abnormal voltage oscillation occurs frequently due to utilization of static var compensator (SVC) in large-scale wind power influx area, which attracts attention of researchers working on network planning and operation. An equivalent model of the system is established on the basis of reactive power and voltage control in typical large-scale wind power influx areas with software DIgSILENT/PowerFactory. Two main control modes of SVC, namely constant voltage control and constant reactive power control, are compared and analyzed via adopting different stability analysis methods including eigenvalue analysis in small signal stability, time-domain simulation and Bode plots. Moreover, the derivation method for open loop transfer function in control theory is introduced targeting certain variables. From the perspective of the new controller, the reason why oscillation occurred when it comes into use in actual wind farms is explained in theory. The results demonstrate that SVC with different control modes has different adaptability to the system's change. In terms of the number of wind farm with SVC and the impedance of the system, the constant reactive power control mode performs better than the constant voltage control mode for weak sending end systems in large-scale wind influx area. © 2017 Automation of Electric Power Systems Press.


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.


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 | 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.


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.

Loading National Power Dispatching and Control Center collaborators
Loading National Power Dispatching and Control Center collaborators