In this study, a network mode energy (NME) method is used to analyse the low‐frequency oscillation (LFO) of a power system with a high penetration of a permanent magnet synchronous generator (PMSG). This method is also utilized to determine the dominant inter‐area oscillation path. NME comes from a network potential energy based on a small signal mode, which includes a generator internal node mode potential energy and a line mode potential energy (LMPE). The exchange process and distribution of NME in the power system containing the PMSG are studied by analysing the composition of LMPE. A sensitivity index is constructed to determine the state variables of the generator and the PMSG, which remarkably influences energy distribution. Then, the path characteristics of LFO are analysed. The dominant inter‐area oscillation paths and energy interaction of the system connecting to the PMSG are determined. The proposed NME can be calculated on the basis of measurement information, and network energy decomposition is carried out using the measured line mode oscillation index. The mechanism of PMSG participating in oscillation is revealed from the network perspective to provide a basis for network‐based regulation. The correctness analysis and simulation of a four‐machine two‐area system with the PMSG and the New England 10‐machine 39‐bus system with the PMSG are carried out.
Frequency fluctuation of wind power grid-connected system is difficult to adjust, aiming at this problem, this paper proposed a control strategy based on the combination of inner loop control and outer loop to restrain frequency fluctuation. extended state observer (ESO) is used as the outer loop. The error and disturbance which cannot be reflected directly in the system structure are estimated by linearization. The inner loop PI controller is designed through the parameters of proportional link and integral link to realize the reasonable allocation of internal model poles and achieve better damping effect. Simulation show that the control strategy can effectively suppress the system frequency fluctuation caused by load fluctuation and maintain frequency stable. The research results can be used to guide engineering practice.
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