| More and more attentions are focused on the environmental problem.The traditional power systems are gradually changed to clean power systems.For example,more and more traditional synchronous generators are replaced by doubly-fed induction generators(DFIG)and the proportion of inertia and exciters of power systems becomes lower,thus the stability of power systems is deteriorated.In order to solve this problem,various grid-friendly DFIG control strategies are proposed to mimic the control capability of inertia and exciters.However,the proposed grid-friendly DFIG control strategies are only focused on single part of the stability issues.The mutual influences of the control strategies are hardly researched when these control strategies are utilized together.The control capability may be badly influenced by the mutual influences of the control strategies and even the stability of power systems are damaged.Based on the concern,the DFIG model including grid-friendly control strategies is established.The transient active current control(TACC),transient reactive power control(TRPC)and virtual inertia control(VIC)are chosen as the study object.The transient active current reference is firstly researched.Second,the influence of TACC on VIC is studied and finally the impact of VIC on TRPC is investigated considering the reactive power loss of wind farm transformer.The impact of the mutual influences on power system transient stability is analyzed and time domain simulations are done to validate the truth of the analysis.In order to mitigate the transient stability of power systems,an improved active power control scheme and an improved reactive power control strategy are proposed after the mechanism of mutual influences and the law of its impact on power system transient stability are drawn out.The time domain simulations are also done to validate the effectiveness of the proposed control strategies. |
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