RT Box

The Fastest Real-Time Simulator for Power Electronics

  • Controller testing with HIL simulation

  • Rapid control prototyping

  • Nanostep® solver with simulation steps of 4 ns

Hardware-in-the-Loop (HIL) Simulation

The RT Box enables high-performance HIL simulations of power electronic systems, where the real controller interacts with a virtual power circuit. HIL simulations allow engineers to validate control algorithms in a safe environment under normal and faulty operating conditions without the risk of damaging the power hardware.

However, the small time constants in electrical circuits and the fast-switching power semiconductors pose a particular challenge for real-time simulations. The RT Box masters this challenge by sampling the PWM signals with a resolution of a few nanoseconds and applying state-of-the-art modeling techniques, such as:

  • Sub-cycle averaging
  • Nanostep

This ensures high simulation fidelity and minimal loop-back latency, even with switching frequencies of several 100 kHz.

Rapid Control Prototyping (RCP)

The RT Box can alternatively serve as a controller for a power circuit. It is capable of generating sophisticated PWM patterns and capturing sensor data via analog inputs. The RT Box comes with encoder and resolver interfaces for electrical machine control and offers various communication interfaces such as SPI and CAN. Using the RT Box for RCP is especially helpful when the final controller is not yet available. It allows engineers to operate and test the power stage while the controller hardware is still under development.

Parallel Computing on CPU and FPGA

The RT Box is powered by a Xilinx Zynq chip that combines multiple CPU cores with an FPGA. This architecture allows circuit models to be partitioned and computed in parallel on the CPU cores and the FPGA. The RT Box offers various solver options to accommodate different application requirements:

  • CPU: General purpose solver supporting most PLECS components, including electrical machines and control systems, with step sizes above 1 µs.
  • FlexArray: Optimized for complex inverter and rectifier circuits, such as multi-level converters, achieving step sizes as small as 250 ns.
  • Nanostep: Guaranteed single-digit nanosecond step size for high-frequency applications such as dual active bridges and resonant converters.
Solver Performance and Availabiltiy:
  RT Box CE RT Box 1 RT Box 2 RT Box 3
Processor Xilinx Zynq Xilinx Zynq Ultrascale+
CPU clock rate 1 GHz 1.5 GHz
Solvers
 ↳ CPU 1 core 3 cores
 ↳ FlexArray
 ↳ Nanostep 1 unit (7.5 ns) 2 units (4 ns)

Nanostep® Solver for MHz Switching

What really sets the RT Box apart from other real-time simulators is its capability to simulate converters with nanosecond time steps. Common oversampling techniques are accurate as long as converters are operated in continuous conduction mode, even if the simulation step size is several micoseconds. However, every simulation step containing a current zero crossing is subject to inaccuracies. If such steps occur frequently, they distort the simulation result.

With the revolutionary Nanostep technology these distortions are minimized by performing the gate signal sampling, the current and voltage computation as well as the zero-crossing detection within a single FPGA clock cycle. The Nanostep solver excels in the simulation of DC/DC converters with an inductive AC link, including:

  • Dual active bridges
  • LLC converters
  • Phase-shifted full-bridge converters

It is also supports classic buck and boost converters and 3-phase inverters with switching frequencies up to 1 MHz.

Scalability

Multiple RT Boxes, connected via multi-gigabit optical links, can form a scalable HIL simulation cluster. This enables distributed synchronous computation of large circuit models, such as:

  • Modular multilevel converters
  • Microgrids

Model Configuration and Upload in Seconds

Circuit models designed in PLECS can be swiftly converted into real-time code and deployed to the RT Box in seconds. Unlike other FPGA-based simulators, the coding process does not involve lengthy bitstream generation.

Required Software Licenses

Operating the RT Box requires no third-party tools, relying solely on software provided by Plexim. Following licenses are needed:

Interface Cards

For fast and easy connection of external hardware a set of breakout boards and interface cards is available:

Why Choose the RT Box?

  • Speed: The fastest HIL simulator for power electronics
  • Standard Toolchain: Seamless integration with the simulation platform PLECS
  • Cost-Effective: A powerful yet affordable solution for controller testing (see pricing)

Which RT Box Model is Right for Me?

Model Target Audience
RT Box CE Classroom and lab teaching
RT Box 1 Versatile and scalable for HIL and RCP
RT Box 2 Multi-core and FPGA for faster, higher complexity circuits
RT Box 3 Increased I/O for multi-level converters and microgrids

The technical specifications of all RT Boxes are listed in a comparison table.