The FPGA-based Power Electronics Toolbox has, in its heart, an electric Hardware Solver (eHS).

The eHS solver is an FPGA-based technology developed by OPAL-RT for real-time power electronics simulation. Thanks to a convenient circuit schematic graphical user interface, the FPGA code is automatically generated, making FPGA-based simulation accessible to a large number of users.

The OPAL-RT electric Hardware Solver (eHS) is a powerful floating-point solver developed by OPAL-RT that enables users to simulate an electric circuit on an FPGA automatically, without having to write the mathematical equations. It combines the simplicity of building electric circuit models using either our OPAL-RT Schematic Editor or the Simscape Electrical Specialized Power Systems (SPS) Toolbox, PSIM, the PLECS Blockset, or NI Multisim software with the strength of OPAL-RT FPGA-based simulators to solve the currents and voltages within the circuit in real-time, with a sample time below 1μs.

The 4th generation of eHS solver uses the modified nodal analysis. It solves a conductance matrix to find the voltage at each node of the circuit, and the current in each branch. The conductance matrix of the circuit is made independent of the switch control signals through the implementation of the Pejovic1 method representing the switch impedance. With this method, a conducting switch is represented as an inductance and an open switch is represented as a capacitance so the conductance matrix does not change during the simulation.

The upcoming 5th generation is based on state space method that allows higher order of discretization and offers better performances than the previous generation. It is currently in a beta version and is being actively developed to become our newest official generation.

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KEY FEATURES

1.1 CONFIGURABILITY

4th Generation

The conductance matrix does not need to be re-computed since switches are represented using the Pejovic* method. All the matrices needed for solving the system are loaded onto the FPGA engine when the simulation is initiated. Reconfiguring the engine with specific firmware for each application is not necessary. This feature makes running real-time simulations of electrical systems at high sampling rates as easy as any RT-LAB simulation.

* P. Pejovic and D. Maksimovic, "A new algorithm for simulation of power electronic systems using piecewise-linear device models," in IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 340-348, May 1995, doi: 10.1109/63.388000.

5th Generation

This new generation is using a new circuit analysis method based on State Space equations resolution for faster and more accurate discretization method. Switching components are now computed with enhanced fidelity thanks to the Time Stamped Bridge technology, which considers the switching events with an accuracy down to 625ps of resolution.

This generation allows the accurate simulation of frequency and/or phase -controlled power electronics systems, such as resonant converter (CLLC, LLC topologies) and Dual Active Bridge with switching frequency above 200 kHz.

1.2 PERFORMANCE

4th Generation : The sample time of the electrical system solved by the eHS solver ranges from 200ns to 4μs, depending on the circuit complexity.

5th Generation : The sample time of the electrical system solved by the eHS solver ranges from 90ns to 4μs, depending on the circuit complexity.

1.3 COMPATIBILITY

eHS solvers provide a flexible environment that allows the user to design the simulated circuit in various netlist editors such as

• OPAL-RT Schematic Editor

• SPS and PLECS Simulink toolboxes

• Powersim PSIM

• NI Multisim software

1.4 SCALABILITY

eHS exists in various licence classes to accommodate low to high-end FPGA-based platforms. It is capable of simulating a Boost circuit with time step as low as 200ns (4th Generation) and 90ns (5th generation), as well as a micro-grid system with outstanding resolution. Depending on the use case, it is possible to interconnect several eHS cores using a multi-FPGA system with low latency SFP 5Gbps links between chassis.

1.5 PARAMETER SETS

It is possible to modify the component values during simulation to apply load variations and faults using the parameter set feature.

Choose your best parameter set flow based on your requirements

• Performance - Option From FPGA: Switch from one set of parameters to another in a single time step.
  Limitation: Number of parameter sets available depends on the size of FPGA and the circuit simulated on the FPGA.

• Flexibility - Option From CPU: Unlimited number of parameters sets
  Limitation: Switching from one set of parameters to another will be done within a second.

SPECIFICATIONS

(See Supported features for more details)

2.1 EHS GEN4

The circuit is designed using blocks in supported netlist editors. A limited number of elements, chosen from a specific list, can be included in each circuit. The maximum number of circuits that can be simulated in one real-time model depends on the firmware installed onto the solver hardware and the number of available eHS licenses installed onto the simulation system. The 4th Generation of eHS comes in various sizes to respond to different needs in terms of FPGA size, simulation complexity, and compatibility. Table 1 describes the existing eHS gen4 cores followed by their associated specifications: Features eHSx16 eHSx32 eHSx64 eHSx128

2.1 eHS - Advanced Performance Add-on (GEN5)

3 INTENDED AUDIENCE AND REQUIRED SKILLS AND KNOWLEDGE

The intended user of the eHS solver within OPAL-RT’s eFPGAsim Toolbox is an R&D, algorithm, or Test Engineer requiring an easily reconfigurable, very-high-speed electrical circuit solver that does not require knowledge of time-consuming custom firmware development and configuration processes.

4 EXTERNAL TOOLS

4.1 OPAL-RT SCHEMATIC EDITOR

OPAL-RT Schematic Editor is brand new circuit editor allowing user to design in a highly efficient user interface the circuit that will be used by eHS. Schematic Editor is compatible with RT-LAB and HYPERSIM to provide you with a clear and simplified eHS experience.

4.2 SIMULINK

Simulink is a software package developed by The MathWorks, Inc. that enables modeling, simulation and analysis of dynamic systems. Models are described graphically, following a precise format based on a library of blocks. The eHS solver uses Simulink to define models that will be executed during an RT-LAB simulation. Users are expected to have a clear understanding of Simulink operation, particularly regarding model definition and simulation parameters.

4.3 SIMSCAPE ELECTRICAL SPECIALIZED POWER SYSTEMS (SPS) AND PLECS SIMULINK TOOLBOXES

The SPS and PLECS Blockset toolboxes provide libraries and analysis tools useful for modeling and simulating electrical systems. They are used by the eHS only as circuit description environments. They can be used from within the RT-LAB environment for real-time simulation, but fail to achieve the very high sample rate that can be attained with the eHS solver. It can be useful, though, to use these simulation tools to compare the results to those of the eHS solver.

4.4 PSIM

PSIM, developed by Powersim, is an Electronic circuit simulation software package, designed specifically for use in power electronics and motor drive simulations but can be used to simulate any electronic circuit. It is used by the eHS only as circuit description environments, and its netlist file can be used from within the RT-LAB environment for real-time simulation, but fails to achieve the very high sample rate that can be attained with the eHS solver. It can be useful, though, to use these simulation tools to compare the results to those of the eHS solver.