Research On Test Methodology And Its Key Technology For Secondary System In Smart Substation

As the development of smart grid, the concept of smart substation is proposed, inwhich some novel types of devices such as smart switch, electronic transformer,merging unit (MU) etc, are introduced. These devices can greatly increase the flexibilityin the organization and distribution of the information. However, the implementationand application of the whole primary and secondary systems are changed greatly. Thetraditional signal transmission by electrical cable is replaced by digital fiber.Information is not transmitted through point to point communication, but through novelcommunication network. Simultaneously, the interrelationship among different devicesin smart substation is closer. Some of the novel types of protection devices need tojudge based on the outputs from multiple devices. The utility engineers must solve theproblems such as how to verify the complex information distribution relationship andcheck the functionalities of comprehensive protection and control, before putting thesmart substation into operation.In the past, the test of secondary system in smart substation mainly involves withthe function verification of single devices. This approach is not able to check thenetwork behavior and correlationship of devices in field test. Therefore, the test lacks ofintegrity, threatening the security and stability power system operation. In thisdessertation, we study the test approach and its key technologies of secondary system ina smart substation from a systematic view. It is expected that the research would providesolution for enhancing the security level of the operation of smart substation and testefficiency. The main research contents and innovative results include:1. By analyzing the structure and network characteristics of the secondary systemin smart substation, a novel whole-view test approach is proposed based on the analysisof the test contents and requirements. The principle, test procedure, and processing oftest results are described in detail. The feasibility of the approach and the keytechnologies to implement are discussed.2. According to time synchronization performance requirement of substation fieldtest, a scheme of wireless time synchronization by IEEE1588and WLAN technology,suitable for distributed whole-view test, is proposed. The impact of field is alsoconsidered. Based on analyzing factors affecting accuracy of synchronization, an improved method based on wireless IEEE1588is proposed by changing the timingmethod and time correction based on average transmission rate of the network. Thesystem is implemented and the performance is comparatively studied. A model ofwireless radiation is built, and the effect of radiation of2.4GHz wireless communicationon secondary device is quantitatively evaluated.3. As the whole-view test needs fast electromagnetic transient simulation, twomethods for accelerating computation are proposed in the dissertation, based on theanalysis of the factors affecting the simulation process and computation speed. InCUDA based parallel computing method, the solution of conductance matrix istransformed into bordered diagonal form by using the matrix decomposition based onpath tree of factor table. The computer tasks are distrubted to independent computingresources provided by CUDA, accelerating the solution of linear equations in theprocess of electromagnetic transient simulation process. In FPGA based hardwarecomputing method, the method of contruction of logic circuit of electromagnetictransient components and faults is designed, which implemented the real-timecomputing of electromagnetic transient simulation based on implicit integral. Withactual examples, the performance of acceleration and computation accuracy is assessed.4. In order to further save computing resources, the improvement and realization ofnetwork equivalence based on VF (Vector Fitting) in large-scale electromagnetictransient simulation are explored in the dissertation, based the Frequency DependentNetwork Equivalence (FDNE) approach. To overcome the shortcomings of VF, MixingMatrix method is introduced. And a new method for network equivalence forelectromagnetic transient simulation considering three-phase coupling is discussed. Bysimulation with actual circuits, the performance of steady-state and transientcomputation with VF method and Mixing Matrix method is comparatively studied. Theapplicability of Mixing Matrix method in the whole-view test is evaluated.