Research On Adaptive Protection Of Distribution Network With Photovoltaic Power Station Considering LVRT Control Strategy

The problems are getting more and more serious because of the increasing penetration of photovoltaic power station in the distribution network.Protection device is the premise condition to ensure the power system safety and stable operation.Reconsidering the design and application of the protection device is the problem urgently needs to solve.This article deeply analyzed and proposed the solutions according the problem.Firstly,analyzed the photovoltaic power station output characteristics and analyzed the low voltage ride through of photovoltaic power station according the newest provision of the photovoltaic power station interconnection.The simulation analysis showed that the steady-state output characteristic is influenced by the battery temperature and sunlight intensity,but the output characteristic is influenced by the control strategy and has the voltage support capabilities when failure.Secondly,established the current source equivalent model which is controlled by the PCC positive sequence voltage baize on the photovoltaic power station failure output characteristics.This model correctly reflects the photovoltaic power station output characteristics when the system occurs failure.Analyzed the node voltage equations under symmetrical and asymmetric fault conditions.Proposed the test root method under the double-ended search method by the nonlinear relationship of the equations.Verified the accuracy of the algorithm by comparing the results between the Matlab and the PSCAD.Thirdly,aimed to the problem of direction element miscalculates by the photovoltaic power station characteristic which is different from the traditional linear power system,analyzed the phase angle between the positive sequence voltage and the positive sequence current of protection under the symmetrical and asymmetric faults.Action area is based on the positive sequence voltage and the positive sequence current.To verify the correctness of the proposed method,builded the typical distribution network with photovoltaic power station by PSCAD.The results showed that the proposed method can determine fault direction and avoid the affect by the fault type and fault location.Finally,basing on the fault feature of the electric parameters when the system with the photovoltaic power station occurs faults,analyzed the traditional adaptive protection action features which are influence by the photovoltaic power station.Proposed the new adaptive protection in distribution network considering the photovoltaic power station influences.Taking an example of 10 kV power system with photovoltaic power station of baoding to verify by PSCAD,the results showed that the proposed principle of protection setting is feasibility.