The Design And Research On LokV Suspended Static Var Generation

As an important issue in the flexible AC transmission systems field of the smart power grids, the development of SVG has vital significance in its design and research. In order to solve the serious problem of the reactive power imbalance which exists in the power grid of our country, various kinds of reactive compensation devices are developed and applied to the power grid. Based on this situation, the10kV,±10Mvar suspended Static Var Generation has been designed and researched in this thesis.Firstly, the basic working principle of SVG is analyzed in both lossless and lossy cases.Secondly, the main circuit of SVG, which has adopted the generalized soft switch technology for cascaded2H-bridge converter in the topology structure, is designed on the basis of this principle, and the fittest parameters of main circuit are selected, including the parameters of the IGBT and its drive, the DC capacitor C and the connection inductor Ls.Thirdly, the device control method is studied in the thesis. The current of reactive power compensation instructions is calculated based on the improved ip-iq detection theory on the basis of the traditional ip-iq detection theory. This theory combining with d-q detection theory adds the phase φ which emerges as soon as the system voltage jump in the process of reactive current detection, so that the system voltage can be detected in any state, Outputs SPWM pulse signals of switches according to the triangle carrier comparison expression directly current control method and adopts the triangle carrier phase shifting SPWM mixed control method.Then the hardware and the software of the control system of SVG are designed. DSP+double FPGA control mode is adopted in the control system, which can perform the calculation of the complex algorithm quickly and efficiently. The control circuit and the protection circuit are mainly designed in the hardware. The DSP software parts and the FPGA software parts are designed in the software. C compiler is used in DSP while VHDL language is used in FPGA to realize online programming in software.Finally, SVG system simulation model is built in the PSCAD/EMTDC software environment. The system is simulated in the following three cases respectively:the simulation analysis of the symmetrical load put into SVG; the simulation analysis of the asymmetrical load; the simulation analysis when the system is at fault. The validity and the correctness are confirmed through the analysis of simulation results in the design of SVG device, which further proves that the main circuit topology structure of SVG device is rational and the control method is accurate.