Fidelity Assessment of Real-Time Simulation for High-Frequency Resonant Converter Applications

Real-Time Simulation: Enhancing High-Frequency Resonant Converter Applications

High-frequency resonant converters are essential in modern power electronics, particularly in the electrification of transportation. These converters provide bidirectional power flow with high efficiency, making them a preferred choice for applications that require high power density. However, designing and validating controllers for these converters is a complex and time-consuming process. This is where Hardware-in-the-Loop (HIL) testing plays a crucial role in accelerating and simplifying the development cycle.

The Challenge of High-Fidelity Real-Time Simulation

One of the major challenges in real-time simulation of high-frequency resonant converters is maintaining a high level of simulation accuracy. The precise modeling of switching events and resonant behaviors is critical for achieving realistic results. Traditional numerical integration methods, such as the Backward Euler (BE) method, often fall short in accurately representing resonant circuits, necessitating the use of more advanced methods.

The OPAL-RT Solution

To address these challenges, OPAL-RT has developed an advanced FPGA-based electrical hardware solver (eHS) designed specifically for high-fidelity real-time simulation of high-frequency resonant converters. This cutting-edge solver:

• Captures switching signals with a sampling frequency exceeding 1GHz.
• Utilizes a high-order numerical integration method to accurately simulate resonant circuits.
• Implements an efficient FPGA-based design that minimizes simulation time steps, achieving 135ns for an entire DC-DC converter system that consists of multiple conversion stages without component decoupling.

Real-World Application: Hybrid Electric Aircraft

A practical use case demonstrating the effectiveness of this technology involves a DC-DC converter system designed for a Hybrid Electric Aircraft. This system features a multi-port converter with two main stages:

• A voltage-balancing stage operating at 100kHz.
• A resonant converter stage, operating at up to 250kHz, which includes:

- A bidirectional CLLC converter interfacing the High-Voltage (HV) load.

- A unidirectional LLC converter interfacing Low-Voltage (LV) loads.

Using OPAL-RT’s eHS solver, real-time simulations were compared to offline reference simulations that employ a variable-step solver. The results demonstrated a significant improvement in simulation fidelity when using the PADE-5 numerical integration method over the BE method, particularly in modeling the resonant inductor current at the primary side of the converter.

The Future of HIL Testing in Power Electronics

As power electronics continue to evolve, particularly in applications such as electric vehicles and hybrid aircraft, the demand for high-fidelity HIL testing will only increase. Ensuring precise and reliable real-time simulation models will be necessary to advance these technologies. OPAL-RT’s latest eHS solver and hardware solutions set a new standard in simulation accuracy, empowering engineers to develop and test innovative power electronic systems with confidence.

With continuous advancements in real-time simulation, engineers can accelerate the design and validation process, ultimately driving the future of high-efficiency, high-power-density electronics forward.

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