Extendable Real-Time Simulation Method And Simulator Design Of Active Distribution Networks Based On FPGAs

Real-time(RT)simulation of active distribution networks(ADNs)is capable of reproducing the dynamic behaviors of the real system and testing the system equipment and their operation strategies.RT simulation of ADNs involving massive high-frequency power electronic converters,various distributed generators and energy storage systems is computationally demanding.The expanding scale and growing time span of system transients brought by renewable energy integration puts forward high requirement for the underlying hareware.Taking advantage of the massive parallelism,deep pipeline,and rich distributed memories of the high-performance hardware field programmable gate arrays(FPGAs),this thesis develops an extendable multi-FPGA-based RT simulator for ADNs.The main contributions of this thesis are summarized as follows:1)The RT simulation framework and system modelling of ADNs is developed in this thesis.According to the high requirements of RT simulation,nodal analysis is employed to solve the overall system.The root-matching method is adopted to form the exponential difference equations that represent the behaviours of the ADNs being modelled.A combined mesh and linear array topology is designed for the multi-FPGA system.The synchronization mechanism for both the singlerate and multirate is implememted to force the FPGAs to operate synchronously.To reduce the influence brought by the communication delay between FPGAs,the data interaction mode is proposed.Considering the modeling requirements of RT simulation,the typical distributed generators and energy storage systems including photovoltaic,battery and wind power generator are designed on FPGA.2)An extendable multi-level parallel architecture of the simulator for ADNs is designed.The coarse-fine-grained partition method of ADNs is presented and the resulting segments are then mapped to the corresponding FPGA hardware resources.To achieve the full parallelisim,a 4-level parallel simulation architecture,including the system-level,unit-level,module-level and element-level is designed in this thesis.3)A high-accuracy and stable multirate simulation algorithm and hardware design is proposed.The entire ADN is decoupled into distributed generators and electric networks according to their inherent time-scales and distinct time steps are then used to solve the subsystems.To handle the interface between the subsystems,a multirate interfacing method is proposed.The hardware design of the multirate interface is presented as well.To further increase the solving efficiency,an asynchronous communication pattern between the electrical and control system of the distributed generators is proposed4)The core modules of the multi-FPGA-based RT simulator for ADNs,including the solver and I/O interface,are designed and implemented.A high-performance solver based on LU decompisiton is designed for the RT simulation of large-scale ADNs,which consists of offline process design on PC and online process design on FPGA Facing the demand for communication with different types of devices,this thesis presents the hardware design of a full duplex photoelectric convertion interface and a universal high-precision analog-to-digital(AD)and digital-to-analog(DA)interface The former makes it possible for multiple FPGAs operating in parallel,sharing the computational burden.The latter contributes to the interaction between the digital simulator and the analog signaling5)Various ADN test cases are simulated on the multi-FPGA-based RT simulator Simulation results are compared with the commercial simulation tool PSCAD/EMTDC to validate the correctness and effectiveness of the proposed method and design from the aspects of simulation efficiency,numerical precision and computing scale.