Fault Analysis On Distribution Network With Inverter Interfaced Distributed Generations Based On PQ Control Strategy

Due to energy crisis and environment pollution issues and the security issue of traditionalgrid, a large number of distributed generations based on clean energy are going to beinterfaced with distribution network, which leads to the change of the fault characteristic ofdistributed network, including the magnitude and direction of fault current. The widely usedinverter interfaced distributed generations show the feature of quick response and it isessential to take the control strategy of IIDG into consideration when the fault characteristic isto be analyzed. Besides, IIDG is required to stay grid connected and provide reactive powerunder the new grid code, so as to support grid voltage. Therefore, this paper takes the controlstrategy of IIDG into consideration and proposes a method of fault analysis on distributionnetwork containing PQ control strategy based IIDGs, which is suitable to the newest gridcode.For the widely used PQ control strategy based IIDG, based on the mathematical modelthe dual control method is used and the output characteristic is analyzed as well. And for thefact that traditional PI control could not be used to realize non-error control underunsymmetrical condition and IIDG would output negative sequence current, the doublerotating dq coordinate system is used to delete the negative sequence current. And when faultoccurs, the fault-ride through control strategy with the capability of voltage support is usedfor IIDG according to the newest grid code. And simulation results show the effectiveness ofthe control strategy.The distribution network with IIDG based on PQ control strategy has been built on theplatform of DIgSILENT. And the fault transient characteristic of IIDG is analyzed withsimulation analysis method. Besides, the fault equivalent model of IIDG under symmetricaland unsymmetrical condition is proposed from analyzing the control response, and thesimulation results have verified the accuracy of the equivalent model.For the distributed network with multi-IIDGs, the node voltage equation is built and forthe coupling effect among different IIDGs and non-linear relationship between the fault voltage of the point of common coupling and the fault current of the IIDG in the nodefunction, an iterative correction method is proposed to solve the function. At last, test resultsverify the feasibility and validity of the proposed method.