Real-time Electromagnetic Transient Simulation Research Articles

Asynchronous co-simulation of photovoltaic power generation system based on FPGA-CPU

In order to realize the real-time electromagnetic transient simulation of grid-connected photovoltaic power generation system with small time step, a heterogeneous multiplexed parallel real-time simulation method based on field programmable gate array (FPGA) and central processor is studied. According to the simulation accuracy requirements of the high and low frequency decoupling module, a differentiated simulation step size is used to solve the problem, and a 1us/50us FPGA-CPU multi-rate real-time simulation platform is constructed, in which the FPGA simulation part meets the real-time requirements of small-step transient simulation through the optimization of the response matching method and the EMTP algorithm, the offline simulation results are compared with Simulink, and the model before and after optimization is analyzed, the real-time electromagnetic transient simulation results are compared with Simulink, and the model before and after optimization is analyzed. By comparing the offline simulation results with Simulink and analyzing the FPGA resource consumption before and after model optimization, the accuracy and real-time performance of the co-simulation method for real-time simulation of grid-connected photovoltaic systems are verified.

ECS-Grid: Data-Oriented Real-Time Simulation Platform for Cyber-Physical Power Systems

ECS-Grid is the first data-oriented real-time electromagnetic transient simulation platform for cyber-physical power systems (CPPS). Traditional simulation tools are constrained by object-oriented programming (OOP) architecture, which is now a significant obstruction to creating a comprehensive cyber-physical simulation. Therefore, the proposed ECS-Grid platform follows a new data-oriented paradigm based on an Entity-Component-System (ECS) framework, which delivers higher flexibility, extensibility, scalability, and performance to support cyber-physical system research. ECS-Grid proposes a layer of virtual intelligent electronic devices (vIEDs) to model IEDs in CPPSs. The vIEDs directly talk to physical components and communicate asynchronously with cyber services via the proposed high-performance JSON-like binary protocol. Tests with the islanding and the man-in-the-middle cyber attack scenarios on a 711-node AC-DC microgrid cluster based on a modified CIGRE 15-Bus system are performed and give accurate results. A faster-than-real-time performance is achieved on the 10th Gen Intel <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> Core <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sup> i7 computer, and real-time performance is achieved on distributed embedded NVIDIA <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> Jetson platform. The ECS-Grid design and test results demonstrate the potential of the ECS data-oriented paradigm and may inspire the renovation of industrial simulation software.

Model predictive control and protection of MMC-based MTDC power systems

Meshed offshore grids (MOGs) present a viable option for a reliable bulk power transmission topology. The station-level control of MOGs requires faster dynamics along with multiple objective functions, which is realized by the model predictive control (MPC). This paper provides control, and protection design for the Modular Multilevel Converter (MMC) based multi-terminal DC (MTDC) power system using MPC. MPC is defined using a quadratic cost function, and a dqz rotating frame voltage inputs are represented using Laguerre orthonormal functions. MPC has been applied for the control of both grid forming and grid following converters in a four-terminal MTDC setup, implemented for real-time Electromagnetic Transient (EMT) simulation. By applying numerous time-domain simulations, the advantages of the MPC when dealing with AC and DC side disturbances are investigated. The investigation highlights the MPC’s inherent feature of fast response and high damping during- and post-disturbance, which is compared to the traditional PI controller performance. The analysis provides a comprehensive insight into the transient behavior of the MTDC during disturbances.

Stabilizing Inverter-Based Transmission Systems: Power hardware-in-the-loop experiments with a megawatt-scale grid-forming inverter

This article presents what the authors believe to be the first experimental verification of the ability of grid-forming (GFM) inverters to stabilize a transmission electric power system that is otherwise unstable. The experiments described here were performed using power hardware-in-the-loop (PHIL) simulation to connect a megawatt-scale battery inverter to a real-time electromagnetic transient (EMT) simulation of the near-future Maui power system. This allows the dynamic interactions between the inverter and the power system to be observed without putting the real power system at risk. The ability to use the actual inverter hardware removes the need to rely on a computer model approximation of the inverter’s behavior.

Real-Time Electromagnetic Transient Simulation of Multi-Terminal HVDC–AC Grids Based on GPU

High-fidelity electromagnetic transient (EMT) simulation plays a critical role in understanding the dynamic behavior and fast transients involved in operation, control, and protection of multiterminal dc (MTdc) grids. This article proposes a cost-effective high-performance real-time EMT simulation platform for large-scale cross-continental MTdc grids based on graphics processing unit (GPU). Fast dynamic transients from both ac and dc networks are captured in real time with 5μs time step, using advanced hybrid-discretized modular multilevel converter model, frequency-dependent transmission line model, and EMT-type model of synchronous generators. The proposed simulation platform i) assembles detailed EMT models of all components within an MTdc-ac grid into a single platform. This setup provides a complete simulation solution to capture fast transient signals required for high-bandwidth controller design and protection studies without any compromise; ii) implements the first GPU-based simulation architecture and corresponding algorithms for MTdc-ac grids with real-time performance at scales of 1s; iii) is highly efficient and balances the high utilization of GPU resources and low latency required for the simulation; and iv) outperforms the existing central processing unit- or digital signal processor (DSP)/field-programmable gate array-based simulators in terms of its higher scalability on large-scale MTdc-ac grids and superior price-performance ratio on the hardware. Accuracy and performance of the proposed platform are evaluated with respect to the reference results from power system computer aided design (PSCAD)/EMTdc environment.

Multi-Rate Mixed-Solver for Real-Time Nonlinear Electromagnetic Transient Emulation of AC/DC Networks on FPGA-MPSoC Architecture

Nonlinear phenomena widely exist in AC/DC power systems, which should be accounted for accurately in real-time electromagnetic transient (EMT) simulation for obtaining precise results for hardware-in-the-loop applications. However, iterative solutions such as the Newton-Raphason method that can precisely obtain the results for highly nonlinear elements, are time consuming and computationally onerous. To fully utilize the time space and optimize hardware computation resources without loss of accuracy, this work proposes a novel multi-rate mixed-solver for AC/DC systems, wherein both iterative and non-iterative solvers with different time-steps are applied to the decomposed subsystems, and the linear solvers are reused within each time-step. The proposed solver and the complete real-time emulation system are implemented on FPGA-MPSoC platform. The real-time results are captured by the oscilloscope and verified with PSCAD/EMTDC and SaberRD for system-level and device-level performance evaluation.

Adaptive Time-Stepping Universal Line and Machine Models for Real Time and Faster-Than-Real-Time Hardware Emulation

Transmission lines and rotating machines that widely exist in power systems should be accurately modeled in real-time electromagnetic transient (EMT) simulation for obtaining precise results for hardware-in-the-loop applications. In the conventional EMT simulator, the time-step is fixed, which may lead to inefficiencies when the time constants of the system change. The adaptive time-stepping (ATS) method can efficaciously solve this problem; however, the ATS schemes for the universal transmission line model (ULM) and universal machine (UM) model remain to be investigated. This article derives the ATS models for ULM and UM, and the proposed ULM model is more stable than the traditional model. Both ATS models are emulated on the parallel and pipelined architecture of the field-programmable gate array (FPGA). The proposed subsystem-based ATS scheme and the local truncation error (LTE) based time-step control enable the large-scale systems to be simulated in real time and “faster-than-real-time” modes. The IEEE 39-bus system with ATS models is emulated on two interconnected FPGA boards, and the emulation results compared with PSCAD/EMTDC and fixed time-stepping (FTS) hardware emulator verify the effectiveness of the proposed models and show that the LTE of ULM and UM can be reduced by 76.5% and 62.0%, respectively, compared with the FTS simulation.

Real-Time MPSoC-Based Electrothermal Transient Simulation of Fault Tolerant MMC Topology

Among different modular multilevel converter (MMC) submodule (SM) topologies, the clamp double submodule (CDSM) has the capability of dc fault current limiting and utilizes a relatively small number of switching devices. Since CDSM has a more complex circuit structure than half-bridge or full-bridge SM, it is a significant challenge for the real-time electromagnetic transient (EMT) simulation for a multiterminal dc (MTDC) system containing CDSM MMC. This paper proposes the device-level electrothermal model of CDSM for real-time EMT simulation, which can accurately present the power losses, the junction temperatures, and the switching transient waveforms of individual switches consuming more computation resources. The individual insulated-gate bipolar transistors of the CDSM MMC during fault clearance transient are evaluated from both electromagnetic and thermal perspectives, which interact with each other dynamically. To ensure the real-time performance of the proposed model, the equivalent circuit model is combined with the device-level model. The system-level and device-level waveforms during normal operation and dc fault transient for a three-terminal dc system are both presented and compared with PSCAD/EMTDC and SaberRD. The simulation system was implemented on the Xilinx Zynq UltraScale+ ZCU102 multiprocessor system-on-chip (MPSoC) platform, and the results were captured by the oscilloscope in real-time.

Exploration of FPGA‐based electromagnetic transient real‐time simulation system design using high‐level synthesis

Field-programmable gate array (FPGA)-based simulation system is applied in real-time electromagnetic transient (EMT) simulation for small time-step simulation. However, the FPGA-based simulation system requires handcrafted hardware description language (HDL) and significant design efforts. This paper explores FPGA-based EMT real-time simulation system design using high-level synthesis (HLS) technology to accelerate the design process and improve the flexibility, because high-level language can be transferred into HDL using HLS. Furthermore, loop unroll and pipeline optimisation directives are analysed and applied for HLS to improve the computation speed of the components. The system can simulate various components, including switches, R-L-C, voltage sources, current sources, and transmission lines. Especially, the system adopting double-precision floating-point calculation can support the network with 74 nodes and achieve 2 us for each small time step on Xilinx Virtex7-690 T FPGA. Comparison of simulation results from offline simulation tools with those from the proposed simulation system validates the correctness of the FPGA-based EMT simulation system using HLS technology.

Design and Implementation of Real-Time Mpsoc-FPGA-Based Electromagnetic Transient Emulator of CIGRÉ DC Grid for HIL Application

Real-time electromagnetic transient simulation is a powerful tool for the power system transient study and the hardware-in-the-loop (HIL) testing. Large-scale DC grid can meet the flexible transmission requirements with high power efficiency and high controllability. CIGRE working group has proposed a DC grid test system, which covers various HVDC configurations and deploys modular multi-level converters (MMCs) in the grid. This work focuses on the efficient solution of the DC grid real-time emulator providing accurate and detailed results. The design and implementation of the CIGRE DC grid are carried out on a hybrid MPSoC-FPGA platform realizing the synergy between the Xilinx Vitrex UltraScale+ FPGA device containing a large number of logic resources and Xilinx Zynq UltraScale+ MPSoC device containing the ARM multi-core processing system and FPGA resources on a single chip. Hybrid modeling methodology using device-level electrothermal model, equivalent circuit model, and average value model for the converters is employed to present the detailed device-level results of local equipment and the accurate system-level results of global interactions of the DC grid. The detailed design partitioning and implementation methods are presented, and the real-time results are captured by the oscilloscope and validated with commercial simulation tools PSCAD/EMTDC and SaberRD.

Dynamic Variable Time-Stepping Schemes for Real-Time FPGA-Based Nonlinear Electromagnetic Transient Emulation

Electromagnetic transient (EMT) simulation of nonlinear elements in power systems is a particular challenge due to the requirements of an accurate representation and an efficient solution. The existing real-time simulators utilize a piecewise linear representation along with a fixed time step for the solution of nonlinear elements. This paper proposes the detailed methodologies for applying variable time stepping to real-time EMT simulation to improve the simulation accuracy and efficiency. The challenges, the feasible solutions, and corresponding restrictions of applying various variable time-stepping schemes along with nonlinear element solution methods in real time are discussed. The offline simulation and the real-time hardware emulation of two case studies, a full-bridge diode circuit and a power transmission system, are presented. The case studies were implemented on the field-programmable gate array device (Xilinx Virtex-7 XC7VX485T) in real time using high-level synthesis tool to achieve a parallelized and pipelined hardware design with minimum coding effort. The real-time emulation results captured by an oscilloscope are validated against the offline simulation on Saber and PSCAD/EMTDC software tools.

A Real-Time Nonlinear Hysteretic Power Transformer Transient Model on FPGA

A transformer is the most widely used equipment in power systems to transfer energy from one circuit to another. For real-time electromagnetic transient simulation, this paper presents a digital hardware emulation of the power transformer on a field programmable gate array. The linear model of the transformer is based on the admittance matrix approach. Detailed real-time modeling of the transient nonlinearities, including hysteresis phenomena, is carried out based on the Preisach theory. The nonlinear solution in real time is undertaken using a full Newton iteration. All the hardware modules for the transformer emulation were developed in VHDL. The model is fully parallelized and pipelined to achieve the lowest latency and the smallest hardware resource consumption. Real-time results on the oscilloscope are compared with off-line results from the ATP software.

Multi-FPGA digital hardware design for detailed large-scale real-time electromagnetic transient simulation of power systems

Multi-FPGA digital hardware design for detailed large-scale real-time electromagnetic transient simulation of power systems

Filters Modeling of Real-Time Electromagnetic Transient Simulation in the Converter Station

In this paper, companion model method is applied to establish a basic filter model for electromagnetic transient simulation. Based on the requirements of real-time simulation in the converter station, this paper proposes a simplified filter model and analyzes the speed-up ratio for model optimization. Simulation result shows that under the presupposition of ensuring calculation accuracy, the simplified model can evidently improve the calculation efficiency and play an important role in the realization of real-time electromagnetic transient simulation in the converter station.

Real-time electromagnetic transient simulation algorithm for integrated power systems based on network level and component level parallelism

The analysis and simulation of power system are becoming more and more challenging as the complexity of system topology and components has been increased. In this paper, a hybrid parallel algorithm is proposed for the real-time electromagnetic transient simulation (EMTS) of integrated power systems containing multiphase machines. The proposed algorithm is composed of a novel network partition method called component level parallelization and the Multi-Area Thevenin Equivalent (MATE) method, which extends the flexibility of the network partition in parallel simulation. Moreover, several methods are developed to enhance the efficiency of the communication and computation. Power systems with up to 410 single-phase electrical nodes and 336 switches are simulated in a time step of 50 μs to validate the proposed algorithm.

Digital Hardware Emulation of Universal Machine and Universal Line Models for Real-Time Electromagnetic Transient Simulation

Real-time electromagnetic transient simulation plays an important role in the planning, design, and operation of power systems. Inclusion of accurate and complicated models, such as the universal machine (UM) model and the universal line model (ULM), requires significant computational resources. This paper proposes a digital hardware emulation of the UM and the ULM for real-time electromagnetic transient simulation. It features accurate floating-point data representation, paralleled implementation, and fully pipelined arithmetic processing. The hardware is based on advanced field-programmable gate array (FPGA) using VHDL. A power system transient case study is simulated in real time to validate the design. On a 130-MHz input clock frequency to the FPGA, the achieved execution times for UM and ULM models are 2.5 μs and 1.42 μs, respectively. The captured real-time oscilloscope results demonstrate high accuracy of the emulator in comparison to the offline simulation of the original system in the EMTP-RV software.

Improved Coherency-Based Wide-Band Equivalents for Real-Time Digital Simulators

This paper introduces an approach which enables very large power systems to be modeled on real-time electro-magnetic transients (EMT) digital simulators. This is achieved using an improved wide-band multi-port equivalent, which reduces a large power network into a small manageable equivalent model that preserves wide-band behaviors. The low-frequency or electromechanical transients are captured with a transient stability analysis (TSA) type electromechanical equivalent derived using coherency-based reduction techniques. The high-frequency behavior is accurately captured by placing in parallel with the TSA equivalent, a passive frequency dependant network equivalent (FDNE). The validity of the proposed technique is demonstrated by comparing the approach with detailed electromagnetic simulations of a modified version of the New England 39-bus test system that includes an HVDC infeed. The power of the method is demonstrated by the real-time electromagnetic transient simulation of a large 2300-bus 139-generator system.

FPGA-Based Real-Time EMTP

Real-time transient simulation of large transmission networks requires significant computational power. This paper proposes a field-programmable gate array (FPGA)-based real-time electromagnetic transient simulator. Taking advantage of the inherent parallel architecture, high density, and high clock speed, the real-time Electromagnetic Transients Program (EMTP) is implemented on a single FPGA chip. It is based on a paralleled algorithm that is deeply pipelined, and uses a floating-point arithmetic calculation to achieve high accuracy for simulating fast electromagnetic transients. To validate the new simulator, a sample system with 15 transmission lines using full frequency-dependent modeling is simulated in real time. A timestep of 12 mus has been achieved based on a 12.5-ns clock period with high data throughput. The captured real-time oscilloscope results demonstrate excellent accuracy of the simulator in comparison to the offline simulation of the original system in the Alternative Transients Program version of EMTP.