Real-time Electromagnetic Transient Research Articles

Compensation Method for Parallel and Iterative Real-Time Simulation of Electromagnetic Transients

Parallelization allows accelerating the computation of Electromagnetic Transients (EMTs). It can rely on the natural propagation delay of transmission lines (line-delay) to decouple a network into sub-networks without any loss of accuracy. Other techniques have to be used when there is no line-delay available. This paper presents one of them, using the Compensation Method (CM). This method is applied to decouple and parallelize real-time EMT simulations. The main novelty towards previous works is the introduction of an iterative version of CM to handle nonlinearities. The performance and accuracy of CM is studied through test cases, including practical distribution and High Voltage Direct Current (HVDC) networks. Hardware-In-the-Loop (HIL) setups with Line-Commutated Converters (LCC) and Voltage Source Converters (VSC) are used to test the iterative CM on practical real-time nonlinear cases.

Real-Time Simulation of Power System Electromagnetic Transients on FPGA Using Adaptive Mixed-Precision Calculations

The massive integration of renewable energy sources and power electronics into the power grid leads to the strong need of real-time Electromagnetic Transients (EMT) simulation of power system using field-programmable gate array (FPGA) platform due to its high efficiency and superior performance. FPGA based EMT simulations – A key for Digital Twin were mainly based on Single-Precision calculations, but ignored potential accumulation displacement. To address this problem, this paper proposes full Double-Precision and Mixed-Precision Floating-Point schemes to achieve optimal balance between numerical accuracy and computational resource cost in FPGA-based EMT simulation even for long duration simulations. Furthermore, adjustable pipeline, address dynamic access and sequence controller techniques for solving high fanout and long datapath hardware implementation are developed to optimize resource usage and timing constraints for all schemes. For non-rotating components, full Double-Precision and full Single-Precision both shows excellent convergence. For rotating components, extra Single-Precision iteration method and Mixed-Precision calculations are compared for Synchronous Machines (SG) with strong nonlinearity, and it is found that only full Double-Precision could avoid phase shift problem. Based on component-level sensitivity analysis, proposed system-level Mixed-Precision scheme is able to achieve close accuracy to that of full Double-Precision scheme and additional average 20% resource reduction for Kundur's system.

Dynamic Frequency Support for Low Inertia Power Systems by Renewable Energy Hubs with Fast Active Power Regulation

This paper concerns the feasibility of Fast Active Power Regulation (FAPR) in renewable energy hubs. Selected state-of-the-art FAPR strategies are applied to various controllable devices within a hub, such as a solar photovoltaic (PV) farm and an electrolyzer acting as a responsive load. Among the selected strategies are droop-based FAPR, droop derivative-based FAPR, and virtual synchronous power (VSP)-based FAPR. The FAPR-supported hub is interconnected with a test transmission network, modeled and simulated in a real-time simulation electromagnetic transient (EMT) environment to study a futuristic operating condition of the high-voltage infrastructure covering the north of the Netherlands. The real-time EMT simulations show that the FAPR strategies (especially the VSP-based FAPR) can successfully help to significantly and promptly limit undesirable large instantaneous frequency deviations.

Compensation method for parallel real-time EMT studies✰

The classical solution for computing electromagnetic transients (EMTs) in parallel relies on the propagation delay of transmission lines. The lines are used as decoupling elements to split the network into different tasks. When there is no natural delay or the delay is too short for the selected simulation time-step, other techniques have to be considered. This paper presents one of them. The compensation method is used in this paper for network decoupling for parallelization. A detailed implementation of this method is presented for real-time simulation. Performances are assessed in both offline and real-time environments with distribution and High Voltage Direct Current (HVDC) network test cases. Switching cases are also studied with HVDC power electronics devices. A Hardware-In-The-Loop (HIL) setup for an HVDC link in operation is also considered to validate the proposed method in a real-time environment.

Use of efficient task allocation algorithm for parallel real-time EMT simulation

Real-time EMT (Electromagnetic Transients) simulation relies on multi-cores computers to accelerate the simulation through parallelization. It also increases simulation accuracy by allowing a lower time step. First, the network has to be split into several tasks using a separation technique. Then, each task has to be allocated/mapped to a processor. This paper focuses on this problem which can be formulated as a TAP (Task Allocation Problem). To find optimal task allocation, operational research techniques can be used. Heuristics such as graph partitioning allow getting fast solutions. Their performances are asserted with very large networks and real-time simulator architectures, both from TSO (Transmission System Operator) grids. Exact resolution methods are used to verify solution quality. The validation of each task mapping strategy is done through a real EMT case study which involves real-time Hardware-in-the-Loop simulation.

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.

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.

A Matrix-Inversion Technique for FPGA-Based Real-Time EMT Simulation of Power Converters

This paper proposes a novel FPGA-based matrix-inversion technique that is specifically tailored and optimized for real-time electromagnetic transients simulation of power electronic converters with high switching frequency. This is the first reported solution that is capable of solving the real-time equations related to using ideal switch model and the associated circuitry in very small time-steps (e.g., an average of 36 ns in a three-phase back-to-back converter case study), without requiring large amount of memory, being limited to small number of switches, adding parasitic elements, or depending on a priori knowledge of the circuit operation or switching strategy. The accuracy of the proposed real-time simulator is verified against the results from experimental measurements.

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.

An automated FPGA real-time simulator for power electronics and power systems electromagnetic transient applications

The paper presents an automated FPGA-based real-time electromagnetic transients simulator for power electronics and power systems applications. The simulator features an automated procedure enabling its straightforward applications to different topologies by avoiding the need of complex FPGA programming. The proposed solver integrates: (i) the Modified Augmented Nodal Analysis (MANA) method, (ii) the Fixed Admittance Matrix Nodal Method (FAMNM), (iii) the optimal selection of the switch conductance parameter, and (iv) efficient sparse matrix-to-vector multiplier. The simulator is able to accurately reproduce, in real-time, electromagnetic transients taking place in power electronics devices together with electromagnetic waves propagating in transmission lines. The peculiar structure of the MANA-FAMNM solver enables to reach extremely low integration time steps and avoids the need to redesign the FPGA code. The results of the proposed simulator are validated by dedicated comparisons with off-line EMTP-RV simulations and a hardware-in-the-loop (HIL) test for a three-phase two-level inverter and a three-phase power network.

Compacting and partitioning‐based simulation solution for frequency‐dependent network equivalents in real‐time digital simulator

Rational models of frequency-dependent network equivalents (FDNEs) have been used in real-time digital simulator (RTDS) for power-system simulation. However, this can lead to a computational burden issue; the application of FDNEs may result in a loss of real-time simulation features because the computational cost of the FDNE component exceeds the limits of RTDS. The authors describe a solution that combines compacting and partitioning of the FDNEs, whereby the former reduces the redundancy in the mathematical model and the latter allows us to exploit parallel computer architectures. Then they describe the results of numerical simulations that demonstrate the effectiveness of the approach. Moreover, the proposed simulation solution is not limited to the applications of FDNEs in RTDS, it solves a set of subsistent computational issues when apply rational models in real-time electromagnetic transients programs tools.

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.