| The nature of the power system is the free transmission of energy to meet the unpredictable needs of the control area load.In the operation of the grid,due to the lack of control capacity or irresponsible behavior in certain area,the control area can not meet the regulatory requirements,which ultimately affects the quality of the overall operation of the power grid.Therefore,in the power system,a reasonable evaluation criterion is required standardize the responsibility of operation,which could secure the reliability during the operation of the power grid,and take the advantages of the interconnected power grid in the meantime.The North American Electric Reliability Council(NERC)set the A standard in 1960 s,and the A standard was replaced by CPS standard in 1997.China Power Grid in 2001 began to draw on the North American CPS standards and put forward the corresponding evaluation criteria,which allows for a more equitable distribution of the responsibilities of the regions for power system frequency control.Nowadays,CPS standard has been developed as the main index of power system evaluation.In the conventional interconnected power system,the tie line between the regions is generally the AC tie line,and the existing evaluation criteria are specifically designed for AC synchronous power grids.However,with the application of DC transmission technology to AC system,the original evaluation environment changes,so the reference quantity and control quantity which the evaluation standard is based on need to be reconsidered.Meanwhile,DC transmission can be used as a means of frequency modulation,and the stability of the system is improved by rapidly adjusting the active power transmitted.Frequency deviation will be affected by the primary frequency control,secondary frequency control and DC frequency control,and the original evaluation criteria can not evaluate the performance of the control area.Therefore,it is necessary to design the matching evaluation criterion for performance control according to the characteristics of HVDC transmission participation in frequency modulation in the interconnected power grid.In this paper,the physical process of AC / DC frequency modulation coordination control is studied,and the essential difference between the operation of DC interconnected power grid and AC synchronous power grid is analyzed.HVDC transmission participation in frequency control changes the original transmission and evaluation environment,and the existing evaluation parameters need to be reconsidered.As the interregional interaction and influence in the DC interconnected power grid have changed,the existing evaluation criteria are no longer applicable.Therefore,two indicators are designed in the paper to comprehensively measure the regional control performance,one is to evaluate the regional behavior of stripping out DC Frequency control,and the other is to evaluate the common control behavior of regional control and DC frequency control.The simulation results show that the new standard can well reflect the various control ability of each part of the region,and verify the feasibility and reliability of the new standard. |
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