Simulation Of Power Electronic Systems Research Articles

A Self-Restoring Fault-Tolerant Method for Controller Cooperation Simulation of Power Electronics Systems

Controller cooperation simulations of power electronics systems can be used to test control strategies and codes efficiently and safely. However, with the switching frequency increment of power electronics systems, the data interaction between actual controllers and simulators requires more software and hardware improvements to ensure its accurate execution. This paper presents an easy-realized self-restoring fault-tolerant method for controller cooperation simulation of power electronics systems without extra software and hardware improvements. The proposed method is built in a controller cooperation simulation system based on CPU simulators and realized by transitorily rematching the control information and simulation data based on the time difference between controllers and simulators. Moreover, the proposed method only needs to modify the peripheral communication calling program and does not need to modify the calculation programs of the simulator. A 20kHz power electronic transformer as an example is built on the cooperation simulation system with and without the proposed method and the experimental prototype to verify the effect of the proposed method. This paper helps to build a controller cooperation simulation system with a self-restoring fault-tolerant, and further provides a fast and effective design and analysis tool for control strategies and codes of power electronics systems.

A Delay-Free Decoupling Method for FPGA-based Real-Time Simulation of Power Electronic Systems

A Delay-Free Decoupling Method for FPGA-based Real-Time Simulation of Power Electronic Systems

Large-signal time-domain equivalent circuit model for PEM fuel cell stacks

Hydrogen fuel cells have become one of the most viable power sources for electric aircraft. Models representing the electrical behavior of the fuel cell stack over the full dynamic operation region are essential for the development of power electronic energy systems powered by fuel cell stacks. This work presents an electrical equivalent circuit model for PEM fuel cell stacks representing the static and dynamic electrical behavior of the fuel cell stack under pulsed loads up to frequencies of 10 kHz. Dynamic phenomena on time scales slower than the considered timescale of power-electronic switching, such as reactant flow, membrane hydration, and temperature effects, are considered stationary. The parameterization method proposed is developed on measured data from a 110 W PEM fuel cell stack and validated with a set of measured data from a 2 kW stack. The time-domain simulated behavior of the parameterized model shows an accurate representation of the measured behavior: the parameterized model reproduces both the static polarization behavior and the behavior under high-frequency pulsed loading with errors of less than 1% with respect to the nominal stack voltage. The model is suitable for dynamic simulation of power electronic systems directly connected to fuel cell stacks and can be parameterized without special electrochemical impedance spectroscopy measurements.

An Automatic Circuit Partitioning Strategy for Accelerated Simulation of Power Electronic Systems

Decoupling the circuit by energy-storage elements is commonly used to accelerate the simulation of large-scale power electronics (PE) systems. However, current researches mainly deal with specific cases manually, and automatic circuit partitioning by computer is not realized. In this letter, a novel automatic circuit partitioning strategy for accelerated simulation of PE systems is proposed. It is a general method for computer implementation and can benefit different types of decoupling simulation approaches. A 2-port solid-state transformer circuit is partitioned by the proposed method to verify its effectiveness. Simulated with a state-variable-interfaced decoupling (SVID) integration method, 3-fold speedup is achieved compared with the original simulation method without circuit partitioning and 100-fold acceleration is obtained in total compared with commercial software.

A fractional time‐step simulation method suitable for the associated discrete circuit model of power electronic system

The associated discrete circuit (ADC) model for switches is widely used in electromagnetic transient simulation of power electronic system. When using ADC model, the problem of virtual power loss caused by L/C switching cannot be ignored and small time-step (≤2 μs) is usually required to guarantee accuracy, both of which will limit the application of ADC model. To cope with this, a fractional time-step simulation method (FTSSM) suitable for the ADC model of power electronic system is proposed. The method is derived from the compact form of electro-magnetic transient program (EMTP) algorithm, and the simulation iteration is implemented by small-step synthesis calculation with different fractional time-steps, which are designed to locate the accurate switching actions. In this way, the simulation can be conducted under larger time-step (to tens of μs) while the accuracy is still acceptable. Further analysis on time domain error and numerical stability of the FTSSM are discussed. Simulations of grid-connected inverter system and permanent magnet synchronous motor (PMSM) driving system are done, using FTSSM and on PSCAD respectively for comparison. The results verify the accuracy of proposed FTSSM, and indicate that the FTSSM is helpful to accelerate the offline simulation and improve the real-time simulation performance.

Design, Implementation, and Validation of Electro-Thermal Simulation for SiC MOSFETs in Power Electronic Systems

Silicon carbide (SiC) mosfets are getting popular in high-frequency power electronic (PE) applications. More and more concerns for system efficiency and reliability are growing due to the increasing switching losses and thermal stress. In this article, an electro-thermal simulation method for SiC mosfets in modern PE systems is proposed. In the device simulation, a behavioral transient model of SiC mosfets is developed and used for generating a multidimensional power loss table in a wide range of operating conditions. The effects of parasitic elements, temperature-dependent parameters, and reverse recovery effect of the diode are taken into account. Furthermore, the power loss look-up table is integrated into the PE system simulation with an additional Cauer-based dynamic thermal model considering heatsink impact. In this way, the instantaneous power losses and junction temperature can be obtained, respectively, with fast simulation speed, reasonable accuracy, and improved simulation convergence. The proposed approach is implemented in PSCAD/EMTDC and further validated by the experimental results of a double pulse test setup and a power factor correction system.

An Automated Semi–symbolic State Equation Generation Method for Simulation of Power Electronic Systems

Computer-aided analysis is playing an important role in the design and control of power electronic systems. A discrete-state event-driven (DSED) framework with state-space modeling has been proposed recently for accurate and efficient off-line simulation. Nevertheless, automated equation formulation for arbitrary circuits is also required to develop the DSED framework toward general simulation software. However, the traditional state equation generation method is very time-consuming, especially for large-scale systems due to the variable topologies brought by switching events. In this article, an automated semi-symbolic state equation generation method is proposed. Based on the switching function modeling of basic switching legs, an explicit function from switching states to state equation matrices is given, which reduces the computational cost without sacrificing any accuracy. The operating and topological characteristics of power electronics systems are utilized for further optimization. The proposed method greatly increases the simulation efficiency of power electronic systems, especially for large-scale systems. Two cases of the 2 MW 4-port solid-state transformers with different system scales are simulated with the proposed method under the DSED framework. About 700-fold and 1200-fold acceleration is achieved compared with one fast-speed commercial software, where the proposed method contributes 50-fold and 110-fold acceleration in the two cases, respectively.

Real-Time Simulation of Power Electronic Systems Based on Predictive Behavior

The field-programmable gate array (FPGA) based hardware-in-the-loop (HiL) test, which minimizes the time-step of the real-time simulation below 500 ns, is an enabling technology for the development of the control unit of high-power electronic systems (HPE). In order to improve the time performance of FPGA-based HiL, this article proposes a novel parallel structure using the predictive behavior of the power electronic system. With this structure, we design an improved system-level solver applied to HPE. A piecewise insulated-gate bipolar transistor (IGBT) model is used to determine the state of the switch, offering a quasi-realistic model of the power converter. A parallel integration method is also implemented to solve the status of the circuit elements. Moreover, the proposed parallel structural can execute both the IGBT model and circuit element model at the same time, thus, reducing the simulation time-step significantly. The numerical accuracy of the solution, the architecture design, and the issue of the parallel computation are discussed in detail. An ac-dc-ac topology is presented as a case study. At last, a 25 ns time step in the National Instruments FlexRIO platform is achieved. Results comparison with the reference model is also identified and discussed.

Discrete State Event-Driven Framework With a Flexible Adaptive Algorithm for Simulation of Power Electronic Systems

Accurate and efficient simulation of power electronic systems is challenging due to their hybrid nature consisting of continuous states and discrete events. In this paper, a comprehensive discrete state event-driven (DSED) framework is proposed for offline simulation of such hybrid dynamic systems. Two key elements of the proposed comprehensive DSED simulation framework that contribute to the significant improvements in numerical accuracy and computational efficiency are a flexible adaptive algorithm for flexible integration of continuous states and an event-driven mechanism for efficient locating of discrete events. The proposed DSED simulation framework is applied to a 50-kVA solid-state transformer and a multileg full-bridge Class-D amplifier to verify its accuracy and efficiency by comparisons with experimental waveforms and simulated waveforms of Simulink and PLECS. Up to 100-fold and 10-fold improvements in simulation speed are achieved at the same level of numerical accuracy compared with Simulink and PLECS, respectively.

Parallel-in-Time Simulation Algorithm for Power Electronics: MMC-HVdc System

The complexity in simulating power electronics, such as modular multilevel converters (MMCs), requires simulation algorithms to speed up the process. Existing simulation algorithms exploit spatial parallelism to speed up the simulation. With the rise in the complexity of power electronics and the presence of an increased number of states within them, there are limits in the speedup using spatial parallelism. In this article, a temporal parallelism algorithm based on parallel-in-time methods is developed for simulation of power electronics systems. The temporal parallelism algorithm is based on the computation of power electronics states on coarse and fine time steps using different models. The models of power electronics systems used in coarse and fine time steps are average-value and detailed models, respectively. The updates to states on coarse time step are computed serially and are used to initialize the states on the fine time step. The updates on fine time step are computed in parallel. A translation method is proposed in this article to update the states on fine time step from the simulations in the coarse time step, and vice versa. The proposed algorithm is applied to simulate MMCs and is validated with respect to a detailed reference MMC model. The proposed algorithm recorded a speedup of up to $3.47 \times $ with five cores.

Piecewise Analytical Transient Model for Power Switching Device Commutation Unit

Taking switching transients of switching devices into consideration in design and simulation of power electronic systems has long been a huge obstacle. Sufficient accuracy has to be ensured, meanwhile more significantly the transient model has to be practical, i.e., providing a convergent result with an acceptable solving speed and a convenient parameter extraction technique. Aiming at both targets, this paper proposes a piecewise analytical transient (PAT) model for switching device commutation unit, taking an IGBT-p-i-n diode pair as an example. A piecewise time-varying voltage source-current source pair is utilized to model the IGBT-p-i-n diode pair. With sufficient accuracy, PAT modeling methodology noticeably increases the solving speed and improves the convergence of converter simulations. Model expressions and datasheet-driven parameter extractions are illustrated in detail. Experimental and simulated results are presented and compared to validate both the accuracy and the practicability of the proposed PAT model, expected to be employed in transient simulations of power electronic systems.

A new approach for FPGA-based real-time simulation of power electronic system with no simulation latency in subsystem partitioning

In real-time Hardware-in-the-Loop (HIL) test applications for power electronic systems, the main hurdle is to tackle with the mathematical models of variable topology of complex and high frequency driven converter. The most widespread solution is to separate the whole system into subsystems. However, partitioning method usually introduces simulation time step latency between different subsystems, which causes numeric instabilities especially when stiff situation occurs. In this paper, we propose a novel parallel simulation approach which has no time step latency in the whole system division, from which a numerically stable system modeling can be realized. Its numerical accuracy of the solution, the architecture design, and the issue pertaining to the parallel calculation are discussed in detail in this paper. The pertinence of the developed solution is also tested using a case study relating to a traction system power electronic application. For this case study, implementations are made both on a 3 GHz Xeon CPU of RT LAB real-time simulator with a 2 μs simulation step and a Field Programmable Gate Arrays (FPGA) Kintex-7 embedded in National Instruments FlexRIO PXIe-7975 enabling a simulation step below 50 ns. Besides, comparison with results obtained from Simpower system in Matlab allows to evaluate the accuracy of our proposed modeling approach.

A Simplified Behavioral MOSFET Model Based on Parameters Extraction for Circuit Simulations

This paper presents results on behavior modeling of a general purpose metal–oxide–semiconductor field-effect transistor (MOSFET) for simulation of power electronics systems requiring accuracy both in steady state and in switching conditions. Methods of parameters extraction, including nonlinearity of parasitic capacitances and steady-state characteristics, are based on manufacturer datasheet and externally measurable characteristics. The MOSFET template is written in the MAST language and simulated in the SABER simulator. Experimental validation of the N-channel power MOSFET-type IRFP240 (Fairchild Semiconductor) rated at 20 A/200 V is performed in a dc/dc boost converter. The main features of the developed model have been compared with the properties of an analytical MOSFET model and a general MOSFET model embedded to a SABER simulator.

A Parallel Approach to Real-Time Simulation of Power Electronics Systems

We define here a new parallel simulation method designed for real-time execution. This method is highly parallelizable and scalable, and the simulation execution time is fully predictable, which is very important for real-time execution. The stability conditions for the method are defined. Furthermore, we show how to define appropriate flow variable injections so that this method can be extended to multiphysic applications and how to implement multirate time step in the defined method. Finally, we present simulation tests that validate the presented method.

Educational Applications of Interactive Tools to Analyze, Design, and Simulate D.C.-D.C. Power Converters

Currently, interactivity is playing a fundamental role in engineering education because of the development of communications and systems. An important challenge is the effective use of computer tools that allow associating teaching methods with the new ways students learn. In the area of power electronics, recognizing different concepts of switching converters is simplified, given simulation and experimentation tools. Nevertheless, general-purpose tools applied in the analysis and simulation of power electronics systems do not make use of the full interactivity that computer applications can offer. Consequently, it is necessary to develop modern tools with specific capacities to complement teaching and research experiences in power electronics. This article describes the Power Electronics Interactive Laboratory implemented in LabVIEW as a tool to introduce interactivity in power electronics education and presents results of its application in research and teaching activities.

Real-time digital simulation of power electronics systems with Neutral Point Piloted multilevel inverter using FPGA

Most of actual real time simulation platforms have practically about ten microseconds as minimum calculation time step, mainly due to computation limits such as processing speed, architecture adequacy and modeling complexities. Therefore, simulation of fast switching converters’ instantaneous models requires smaller computing time step. The approach presented in this paper proposes an answer to such limited modeling accuracies and computational bandwidth of the currently available digital simulators.As an example, the authors present a low cost, flexible and high performance FPGA-based real-time digital simulator for a complete complex power system with Neutral Point Piloted (NPP) three-level inverter. The proposed real-time simulator can model accurately and efficiently the complete power system, reducing costs, physical space and avoiding any damage to the actual equipment in the case of any dysfunction of the digital controller prototype. The converter model is computed at a small fixed time step as low as 100ns. Such a computation time step allows high precision account of the gating signals and thus avoids averaging methods and event compensations. Moreover, a novel high performance model of the NPP three-level inverter has also been proposed for FPGA implementation. The proposed FPGA-based simulator models the environment of the NPP converter: the dc link, the RLE load and the digital controller and gating signals. FPGA-based real time simulation results are presented and compared with offline results obtained using PLECS software. They validate the efficiency and accuracy of the modeling for the proposed high performance FPGA-based real-time simulation approach. This paper also introduces new potential FPGA-based applications such as low cost real time simulator for power systems by developing a library of flexible and portable models for power converters, electrical machines and drives.

Hardware-in-the-Loop Simulation of Power Electronic Systems Using Adaptive Discretization

This paper presents the hardware-in-the-loop (HIL) simulation of power electronic systems using a unique adaptive discretization technique based on the input of the system, where the coefficient matrices and system equations are changed while the simulation is running. The voltage-source-converter (VSC)-based HVDC system is used as a case study. Two z-transform-based discretization techniques, known as the step-invariant transformation (SIT) and the ramp-invariant transformation, and one of their derivative time-shifted SIT are applied for simulating the VSC-HVDC system. Discrete switching synchronization algorithms are used to accommodate the asynchronous events that take place in between two discrete simulation points. The HIL simulation is implemented using an off-the-shelf PC cluster interfaced with a digital controller. The simulator and the controller are connected through I/O ports, which facilitate the exchange of analog and digital signals. A 4-kW VSC-HVDC experimental setup is used to validate the simulation results, using the same digital controller as that in the HIL simulation to supply the necessary gate pulses for the experimental VSCs. A comparative study of the results obtained through offline, HIL simulation, and the experiment is presented.

USING FIELD-PROGRAMMABLE GATE ARRAYS FOR HIGH-SPEED REAL-TIME SIMULATION

Some applications of real-time simulation now require frame times that are shorter in duration than can be delivered by traditional methods such as real-time versions of Linux (RT-Linux). RT-Linux can be satisfactory for frames as short as 10μS, but there is now a need, for example in the simulation of power-electronic systems, for frame times as short as 1 μS or even less. Techniques based on the interfacing of digital signal processors (DSPs) to a Windows PC have achieved a 2 μS frame time for a typical power electronics application and less than 1 μS is shown to be possible using field-programmable gate arrays (FPGAs). Combining these high-speed techniques with simulations of the rest of the system necessitates the use of multi-rate techniques. Software tools, interfacing issues, and system architecture for a high-speed, real-time, distributed, multi-rate (HRDM) simulator are discussed.

Simple Modeling and Identification Procedures for “Black-Box” Behavioral Modeling of Power Converters Based on Transient Response Analysis

Today, black-box behavioral models of power converters are becoming interesting for system level simulation of power electronics systems. These models can be used to evaluate the response of systems that are composed of commercial converters, since they can be fully parameterized by analyzing the actual converter response. To optimize the required computational resources, these models should be as simple as possible. Furthermore, the identification of the parameters should be carried out easily, looking for simple experiments and straightforward adjusting algorithms. Easy modeling and identification procedures, based on a transient response analysis, are proposed in this paper. Using this method, a large-signal black-box behavioral model of a power converter is composed of reduced-order transfer functions, which are identified by analyzing the step response of the converter. Both an actual commercial dc-dc converter and a line-commutated rectifier have been modeled and identified by means of this approach, in order to validate the proposed procedures.

Special Issue on Modeling and Simulation of Power Electronic Systems

Special Issue on Modeling and Simulation of Power Electronic Systems