The influence of model mismatch to power system calculation, part I: on the steady state calculation

Secure and reliable operation of power system is significant for nation's economy development and society stability. To ascertain this, analysis and calculation plays an important role. Power system calculations can be classified into three categories in time domain: for the past, for the present and for the future respectively. And the calculations for the future seem to be more significant to support power system operation and make production arrangement. However, almost all the calculations of power system are based on the mathematic models established from the physical system; and the models may have various errors and mismatch the actual system, especially for the calculations facing the future. The mismatch between calculation model and actual system influences the analysis result and the operation of power system. In this paper, the influence of two kinds of model mismatches injection mismatch and grid structure mismatch on the actual system are analyzed for power flow calculation using matrix analysis method. The results show that the calculation errors of injection parameter mismatch are approximately linear to the mismatch quantities, and the calculation errors of grid structure mismatch are closely related to the admittance of the mismatching branch and the phase-angle difference of its node voltage. Because the mismatch between calculation model and real system always exists, so this paper also suggests that we should depend more on measurements rather than calculation models in power system analysis.