Unified Modeling of External Characteristics for Multi-Type Reactive Power Sources Under Short-Circuit Faults

Under short-circuit faults, synchronous machine power source exhibits voltage source characteristics, while non-synchronous machine power source external characteristics are determined by the control mode, presenting the controlled voltage source or current source characteristics during fault ride-through. At present, the external characteristic models of the above different types of power sources under short-circuit faults have not been unified. Therefore, this paper proposes a unified model of reactive-voltage external characteristics for synchronous machine power source and non-synchronous machine power source under short-circuit faults. Firstly, the excitation regulation characteristics of synchronous machine power source, the fault ride-through control strategy of grid-following converter and the fault current limiting method of grid-forming converter are considered in the model proposed in this paper. Then the short-circuit currents contributed by different types of reactive power sources under short-circuit faults are analyzed based on the model. Finally, actual and equivalent models of synchronous and non-synchronous machine power sources are established based on DIgSILENT PowerFactory to verify the correctness of the proposed unified model and the accuracy of the short-circuit current analysis based on this equivalent model.