Advanced Materials Research Vols. 860-863

Abstract: The MV multiple Microgrid includes not only a lot of DGs, and may also contain some small microgrids. To the large scale MV multiple microgrid, the interconnection protection problems of different levels microgrid will decide the safe and stable operation of the maximum range. In this paper, list the challenges which are crucial to the microgrid protection, put forward a protection scheme based on the digital integrated protection terminal (DIPT) to solve these problems according to the structure characteristics, analyze the basic principle with comparing composite modulus of fault currents in a DIPT control zone to identify the fault branch and the necessary communication scheme between DIPTs is discussed. At last, build the system model in PSCAD/EMTDC and verify the theory feasibility in different operation modes and different fault types.

Abstract: Traditional transformer fault diagnosis based on single source of information has significant limitation in identification of transformer fault type because of power transformers complex structure and changeable operating environment. So fusion technology is introduced into the fault diagnosis of power transformer. This method divides the progress of transformer fault diagnosis into two fusion levels. The first level is to ascertain whether it is overheated or discharged by content of gases dissolved in transformer oil. The second level is to ascertain the location or cause of the fault by electric data. The intelligence algorithms which are used in these two levels are both the improved BP neural network algorithm. Finally, the effectiveness is validated by the result of practical fault diagnosis examples.

Abstract: With the growing of the system size, rapid, accurate method used for calculating power flow is an important task for the real-time analysis of power system. This paper puts forward a new fast method used for calculating power flow based on ODE(ordinary differential equation).The power flow problems are transformed into solving the differential equations, which avoids calculating Jacobian matrix, and doesn’t need any preprocessing. In order to accelerate the computing speed, the diagonal elements of Jacobian matrix is approximately calculated using the node voltage amplitude and the node admittance matrix. Numerical examples show that the method is simple. Compared with Newton's method, GMRES, MA ,this method has a distinct advantage in computing speed.

Abstract: Through the analysis of traditional forward and backward substitution method, put forward an advanced algorithm of power flow calculation applied for the radial distribution network. This method optimizes the numbered embranchments, nodes, branches, uses directly the branch impedance parameter and the given power of the end node to calculate the voltage and power distribution, And use MATLAB to compile power flow calculation program, which is proved to be feasible by an example.

Abstract: Models of impact load of steel enterprises play an important role in the stability influence of impact load on power system. Take a certain steel enterprise for an example, two modeling methods of impact load are proposed, which can be easily integrated with power system analysis software package (PSASP). These two methods have certain practicality and can be used in most of impact load.

Abstract: The participants utility of the peak regulation market is analyzed in this paper. And then a trading model of the market is proposed which employed the marginal generating cost as decision variables. Using the proposed trading model, the market characteristics are revealed that the total generating costs are reduced after peaking transaction. The bidding, market clearing and settlement rules are given based on the trading model. A case study illuminates the theory results.

Abstract: According to the structural characteristics of the electrical one-line diagram at substation, Its proposed that designing the database which stores electrical properties and graphics properties of the equipment in the paper. And an intelligent graphical modeling and automatic implement of main electrical connections are achieved based on the database. By means of the graph database integrated platform, a topology analyzing method based on bus for main electrical connections is presented, which is capable of not only computer graphics processing easily, but also describing accurately and reliably the topological structure of the main electrical connections. Finally the node admittance matrix is generated and the calculation of short circuit current is completed automatically.

Abstract: Based on mastering the supply power and the maximum load of the 10kV distribution transformers, this paper calculated the maximum and minimum load shape coefficient of the transformers and segmented lines, and obtained the upper and lower limitation of the theoretical line loss with average current method. In the largest variable loss calculating process, this paper put forward an effective iterative fitting algorithm. Firstly, it fitted out the ultimate load curve of the transformer high voltage side, then it fitted through iteration out the ultimate load curve of the superior branch lines and calculated the maximum shape coefficient, considering the influence of transformers loss on the line load curve in the calculation process. The calculation method provided theory evidence for enterprise line loss management level evaluation and vulnerable spot location in the line loss management and enterprise future line loss rate indicator setting.

Abstract: This paper presents a branch-current distribution system state estimation algorithm considering zero-injection constraints. The algorithm takes the branch-current amplitude and phase angle as state variables, considering current-amplitude measurement easily without measurements conversion and makes full use of voltage amplitude measurements, power measurements and current measurements. In order to improve the robust performance of algorithm, exponential function is adopted as the objective function in this paper. The paper takes simulation test to verify the algorithm correctly and effectively on improved IEEE 34 nodes system.

Abstract: In this paper, a new kind of recursive algorithm has been raised. It optimized the distribution network system reliability calculations, improved some efficiency, and met the user's needs closely. This algorithm needs no network equivalence process,has no complex principle and brings no difficulty to programming.Through its failure analysis, can be more easily identify key equipment of distribution systems for customers to adjust. This algorithm can easily cooperate with fault reconfiguration.No adjacency matrix and special chain table will be formed during searching procedure; it takes advantage of basic table of node data and branch data to do searching work, and easily to get access with field data. The algorithm uses recursive search also reduces programming greatly.