Research On Micro-grid Fault Diagnosis Based On Redundant Embedding Petri Net

With the massive access of distributed generations,the development of micro-grid is becoming an inevitable trend.On account of the variable topology and multi-terminal power supply in micro grid,the fault diagnosis of micro grid faces many challenges.For example,traditional fault location criterions are unsuitable,fault diagnosis modeling is complex or poor universality,and the fault reasoning operation is time-consuming and so on.Hence,this thesis focuses on establishing a high transplantable fault diagnosis model aiming at the fault features in micro-grid,and a simple inference algorithm with good error-detecting capacity should be proposed.The micro-grid is double-terminal or multi-terminal supply and its structure is flexible in the topology.In the fault features,the DGs will also supply short-circuit current to the fault point,so the traditional fault criterions which rely on current or power direction information are no longer applicable.Based on this,a fault location criterion based on current magnitude,current phase and DG's current direction information is proposed,and the fault transient component is used as the supplementary criterion.Furthermore,Because of the information distortion or malfunction,it is not reliable to locate fault merely making use of relays and circuit breakers information from supervisory control and data acquisition(SCADA).Hence,in this thesis,hierarchy model utilizing the electrical ternary criterion and relays' and circuit breakers'state information is accomplished,which consists of the fault location layer and the fault clearance layer.In order to increase the portability of the model,the aggregative processing for the breakers is implemented.The double-arrow arc are introduced to reduce the number of places and the model is simplified well.Further,the time constraints are set on transitions and the model's reachability is verified by software HPsim.Finally,based on the fault clearance layer of the Petri net model,an improved redundant coding Petri net reasoning algorithm is proposed.This algorithm can identify the incorrect actions only by the transition fault check.And it can be concluded that a transportable hierarchical Petri net model of the upstream and downstream lines connected with the same bus can be built fast from case study.The validity of the improved redundant coding Petri net fault reasoning algorithm is verified.