eHS

eHS, or Electric Hardware Solver, is OPAL-RT’s FPGA-based toolbox for real-time simulation of power electronic circuits and power systems. It is not related to Environment, Health and Safety software, which shares the same acronym. Released in 2012 for MATLAB/Simulink users, eHS uses a generic, reprogrammable electrical solver that simulates circuits without coding or state-space derivation. It runs at time steps as low as 32 ns with switching frequencies up to 500 kHz, and is used for hardware-in-the-loop testing of onboard chargers, solar inverters, motor drives, electric propulsion systems, and traveling wave relay protection.

FPGA-based power electronics simulation solves electrical circuit equations on a field-programmable gate array rather than a CPU, allowing the solver to run in parallel at time steps measured in nanoseconds. This resolution is what makes real-time simulation of fast-switching converters possible. eHS reaches a minimum time step of 32 ns and supports switching frequencies up to 500 kHz, with 625 picosecond oversampling.

Use FPGA when the model contains fast switching devices, resonant converters, or dynamics faster than roughly 10 microseconds, and CPU when the model is large but slower, such as extended grid networks or vehicle-level dynamics. Most real systems need both. eHS supports co-simulation, so the FPGA handles high-frequency switching while the CPU manages broader system behaviour on the same target.

Accuracy degrades when the simulation time step is too coarse to resolve switching events, so transitions land between time steps and the solver reports a switch that happened at the wrong instant. The usual workarounds, averaging the converter model or artificially decoupling the network, trade fidelity for stability. eHS addresses this with 625 picosecond oversampling and interpolating converter models, resolving switching instants far below the simulation time step, and by running up to 21 three-phase converter models on one target without manual decoupling.

Yes. SiC and GaN devices switch far faster than silicon, which typically forces engineers to simplify the topology or accept averaged models. The High Speed Converter Solver available within eHS simulates advanced architectures, including resonant converters and topologies with bidirectional switches, without reducing the topology to fit a predefined converter model. It supports up to 500 kHz for Voltage Source Converter (VSC) applications and 250 kHz for resonant converter models.

eHS is compatible with Simscape Specialized Power Systems (SPS), PLECS, PSIM, and the built-in OPAL-RT Schematic Editor. No coding is required. The solver is generic and reprogrammable, so circuits are drawn schematically rather than derived as state-space equations or written in HDL. Models deploy to OPAL-RT and NI real-time platforms without rebuilding the circuit, and parameter sets can be changed on the fly to test fault conditions without recompiling.

eHS runs the power stage in real time on FPGA while the physical controller under test sees realistic PWM and analog signals, so control hardware can be validated before a prototype or vehicle exists. For onboard chargers, this covers AC-DC PFC and DC-DC LLC resonant stages at switching frequencies up to 180 kHz on an OP4610XG. For motor drives, optimized FPGA models cover PMSM, IPM, BLDC, SPM, induction machines, and switched reluctance machines.