Kernel Solver Design of FPGA-Based Real-Time Simulator for Active Distribution Networks

The literature review explores the evolution and advancements in the implementation of latency-based solvers for real-time simulation of power electronic systems using field-programmable gate arrays (FPGAs).The journey begins with Dr. Johnson, who highlights the exceptional capability of FPGAs to outperform traditional general-purpose processors in floating-point throughput for power flow computations.[1] This foundational work sets the stage for subsequent research that delves deeper into the acceleration of various computational tasks using FPGA technology.As the field continues to mature, new methodologies and algorithms are developed to harness the full potential of FPGAs.These innovations aim to not only improve the performance of power electronic simulations, but also to enhance the flexibility and reconfigurability of the systems.Researchers are exploring novel approaches such as adaptive solvers, where the latency of the system dynamically adjusts based on the complexity of the simulation.[2] This adaptive nature allows for efficient resource allocation and utilization in real-time applications, leading to improved overall system performance.Furthermore, advancements in FPGA architecture and design techniques enable the integration of multiple solvers on a single chip, catering to the increasing demand for multi-domain simulations.This integration paves the way for seamless co-simulation of diverse power electronic systems, including converters, inverters, and motor drives.Additionally, the emergence of high-level synthesis tools simplifies the development process, making it more accessible to researchers and practitioners alike.[3] These tools enable the conversion of high-level hardware description languages into FPGA-specific designs, alleviating the need for manual low-level coding.Moreover, the availability of FPGA development boards and development kits provides a testing ground for prototype implementations, allowing researchers to evaluate their designs in a real-world scenario.[1] In conclusion, the literature review highlights the evolutionary journey of latency-based solvers for real-time power electronic simulations using FPGAs.From the initial groundbreaking work to the current state-of-the-art advancements, researchers have continuously pushed the boundaries to achieve higher performance and accuracy.With ongoing research and innovation, the field is poised for further growth and development, promising even more efficient and versatile solutions for real-time power electronic simulations.[4] [5] build on this foundation by addressing the parallelization of the sparse Matrix-Solve phase in SPICE applications.Their findings indicate that reduced-precision floating-point datapaths can significantly enhance performance, achieving speedups of 2-18 times over single-core microprocessor implementations.This article emphasizes the importance of exploiting parallelism and optimizing resource usage in FPGA designs.The authors present an FPGA-based framework that effectively tackles and addresses the inherent challenges associated with simulating intricate physical phenomena utilizing unstructured spatial discretization.This innovative and pioneering approach significantly enhances data locality and memory access patterns, thereby showcasing a remarkable and astonishing 90 times speedup as compared to high-performance microprocessors.[1] The demonstrated outcomes and results of this work serve to underscore and emphasize the critical significance of efficient and effective memory management when harnessing and leveraging the immense computational power offered by FPGAs.This research proves to be a groundbreaking and pivotal advancement in the field, with far-reaching implications and potential for further exploration and application in diverse areas of study.[6] Introduce FPGA-SPICE, which is a state-of-the-art simulation-based power estimation framework that perfectly integrates seamlessly with cutting-edge architecture exploration tools.

Real-time simulation of distribution system is challenging due to its' complex structure consisting of DGs. In this literature, a real-time simulator for distribution system with DG integration based on the field programmable gate array (FPGA) is realized for hardware emulation. The overall framework and asynchronous multi-rate interface method between DG with high nonlinearity and distribution system is proposed. The models of main components in distribution system are designed in FPGA. The hardware parallelism and highly pipeline design is utilized to guarantee real-time simulation, which has strong generality and flexibility. The simulator uses a floating point arithmetic calculation to achieve high accuracy. To validate the new simulator, a photovoltaic-battery hybrid generation system and a typical distribution system integrated with PV generation system are emulated in the hardware. The time-step of DG system and distribution system reach 1.096μs/1.696μs and 2μs/2μs respectively. The captured waveforms show excellent accuracy in comparison to the offline simulation in PSCAD/EMTDC. The time-step is less than RTDS which indicate a higher precision. The resource consumption of FPGA also show advantage compared with RTDS.

The method for modeling switching converters plays a key role in real-time simulators. Associate discrete circuit (ADC) modeling technique is a commonly used method for modeling the switching converter. However, the optimal selection of the ADC-based switch model parameters has great importance in the accuracy of the real-time simulator. In this paper, the design of a real-time simulator for a switching power converter has been done, in which a novel method for detecting optimum values of the switch model parameters has been expressed. Particle swarm optimization (PSO) algorithm is used to find these optimum values using state-space analysis of the modeled circuit in the z-domain. The modified nodal analysis (MNA) method solves the real-time model at each simulation time-step. Case studies are a single-phase 5-level Cascaded H-Bridge (CHB), three-phase 9-level CHB inverter, and a Transmission line. Field-programmable gate array (FPGA) has been used as a platform for implementing the real-time simulator. Experimental result of the real-time simulator of the 5-level CHB inverter on a SPARTAN-6 FPGA and its comparison with the result of a prototype of a 5-level CHB inverter confirms not only the performance of the real-time simulator, but also the effectiveness of the proposed method for confirming the real-time simulator accuracy.

This paper deals with a real-time simulation (RTS) able to accurately reproduce an electrical system in real-time. The RTS proposed architecture is written in VHDL and implemented in a field programmable gate array (FPGA) device. Multi-sampling approach is adopted allowing a real-time functioning with different time-steps and different operating conditions with minimized lost of accuracy. The proposed concept is illustrated by the RTS of each of a three-phase RLE load performed with a very short time step of 2.5 mus, an inverter, the measurement system and the hysteresis current controllers. Comparison with experimental results shows the high performances of this RTS.

For the power system with a large number of power electronic equipment, the traditional electromagnetic transient real-time simulator is difficult to achieve small step simulation. To solve this problem, a power system transient real-time simulator is built by adopting a power system multi-rate real-time simulation method based on field programmable gate array (FPGA) and CPU. Taking the photovoltaic power generation system as an example, the system is divided into a large step part and a small step part by adopting a model partition method, and the asynchronous communication between FPGA and CPU is realized through Ethernet to form a large step-small step multi-rate co-simulation platform. For the error problem caused by the system data interaction after model partition, a PWM equivalent averaging method is proposed to equalize the output voltage at the AC side of the inverter, so as to reduce the error and compare the consumption of the equalized hardware resource. Finally, by comparing with the simulation results of the Simulink offline model, the experimental results have verified the effectiveness and accuracy of the method in real-time simulation of the power system.

This paper presents the implementation and experimental details of a real-time digital simulator designed for representing a Distribution Static Compensator (D-STATCOM) interfaced with a digital controller. Real-time simulation using conventional fixed time-step integration algorithms can lead to erroneous results due to the lack of synchronism between the simulator time-step and the discrete switching signals coming from the digital controller. The real-time simulation algorithm implemented in this paper overcomes the drawbacks of a fixed time-step algorithm. The real-time algorithm relies on precise registration of timing of the incoming discrete firing pulses and a subsequent correction procedure to calculate the system state. This approach has been implemented on a hybrid digital processing platform comprising of a Digital Signal Processor (DSP) and a Field Programmable Gate Array (FPGA). The platform represents both the power electronic system and the digital control system. Experimental results, for a 5 kV A D-STATCOM system, in verification of the real-time simulator results are also provided.

This paper presents a field-programmable gate array (FPGA)-based real-time digital simulator for power electronic apparatus based on a realistic device-level behavioral model. A three-level 12-pulse voltage source converter (VSC)-fed induction machine drive is implemented on the FPGA. The VSC model is computed at a fixed time step of 12.5 ns, allowing a realistic representation of insulated-gate bipolar transistor (IGBT) nonlinear switching characteristics and power losses. The simulator also models a squirrel-cage induction machine, a direct field-oriented control system, and a pulsewidth modulator to achieve the real-time simulation of the complete drive system. All the models have been implemented using very high speed integrated circuit hardware description language (VHDL). Real-time simulation results have been validated using the measured device-level IGBT characteristics.

A new hardware platform for digital real-time simulation and control applications is introduced which is highly expandable and customizable due to its modular design and flexible, open interfaces. The system is based on digital signal processors (DSPs) and field programmable gate arrays (FPGAs). A detailed description of the processor and interface boards as core components of the system is given. A small-scale desktop system for hardware-in-the-loop real-time simulations is shown. Furthermore, modeling methodologies and commonly used integration techniques with regard to usual problems and practical implementation are presented. An actual implementation is presented as an example simulation which is used to verify the functionality and evaluate the performance of the real-time simulation platform. A real-time simulation of a buck converter with a time-step of 1 µs without FPGA co-processing is shown and the simulation results are compared to real hardware measurements. To address the common problem of inter time-step switching, solutions are discussed and two approaches are implemented and compared. In total, this paper presents a short overview of digital real-time simulation including modeling and integration, software implementation, hardware platform for code execution and hardware-in-the-loop testing.

The microgrid containing a large amount of high frequency power switches and nonlinear components has put forward high requirements for power system real-time simulation technology. Multivalued coefficient prestorage can reduce the calculation steps in real-time simulation. In order to reduce the storage pressure of the multivalued coefficients, the whole network is divided into multiple subnetworks that can be simulated in parallel, and only the parameters for computing input variables and internal variables are prestored. The multiport hybrid equivalent is performed to reduce the number of simultaneous network equations. The input variables are tied to state variables of the circuit so that the iterative calculation is limited to the local network. The devised methodology is validated through simulation of a low-voltage microgrid on a field programmable gate array (FPGA)-based real-time digital simulation (FRTDS) platform at a 5 μs time step. Comparison with a power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) model shows that the proposed method is effective.

Real-time (RT) simulation plays a fundamental role in the design and validation of hardware and software for power electronic converters and electric drives. In this paper, a field-programmable gate array (FPGA)-based RT platform for simulation of power converters and electric machines is presented. Strategies for modeling power electronic devices are explained and compared. In addition, a Thevenin-based equivalent model of a switch is enhanced to model the on characteristics of these devices. This motivates the design of an electrothermal algorithm for FPGA implementation. With respect to electric machines, different methods for modeling of the saturation characteristics are evaluated for their use in RT simulation. A procedure to efficiently compute the saturation characteristics is proposed. Finally, a hardware-in-the-loop model of an electric vehicle drive is used to illustrate the machine saturation.

The article presents the results of transmitting video data simulation in real time from video cameras on board Unmanned Aerial Vehicles (UAVs) to a ground station (GS). The main purpose of the article was to evaluate the impact of the flying source node number on Quality of Service (QoS) metrics, such as Packet Delivery Ratio and Goodput at OSI model application layer. A scenario was considered when hovering over UAVs, in the zone of reliable communication, transmitted a stream of video data to a ground station, then the distance between the UAV and the GS increased to repeat the experiment. The bitrate was maintained at the same level, close to the bitrate of real high-definition video. The experiment was carried out in the Network Simulator 3 (NS-3) simulation environment for scenarios with one, two, four, and eight source nodes. Simulation results have shown the negative impact of the increasing the number of flying source nodes on Quality of Service (QoS) metrics such as Packet Delivery Rate (PDR) and Goodput. Recommendations regarding the applicability of different standards of the 802.11 family to scenarios for using UAVs in the multistreaming video data transmission mode are given. A change in the relationship of useful throughput on the number of source nodes by 15 % was also found.

This chapter briefly presents a various industrial applications of real-time simulation in the fields of power systems, motor drives, avionics and robotics. It also presents the model-based design methodology, and discusses the main challenges encountered in the design of real-time simulators (RTS). The most important aspect of real-time simulation technologies is that they need to make their computations fast enough to keep up with real-world time. Modern RTS are typically built around multicore multiprocessor PCs with extensive I/O capabilities based on field programmable gate array (FPGA) technology. The chapter discusses various applications of real-time simulation. These applications are: rapid control prototyping (RCP), hardware-in-the-loop testing (HIL) or controller-in-the-loop (CIL), software-in-the-loop (SIL), power-hardware-in-the-loop (PHIL), and rapid simulation (RS). The FPGA models are also integrated into the RT-LAB real-time environment and directly linked with the simulator I/Os, providing ultra-low HIL gate-in-to-current-out latency, suitable for testing motor controllers with ultra-low latency requirements.

Wind power generation studies of slow phenomena using a detailed model can be difficult to perform with a conventional offline simulation program. Due to the computational power and high-speed input and output, a real-time simulator is capable of conducting repetitive simulations of wind profiles in a short time with detailed models of critical components and allows testing of prototype controllers through hardware-in-the-loop (HIL). This paper discusses methods to overcome the challenges of real-time simulation of wind systems, characterized by their complexity and high-frequency switching. A hybrid flow-battery supercapacitor energy storage system (ESS), coupled in a wind turbine generator to smooth wind power, is studied by real-time HIL simulation. The prototype controller is embedded in one real-time simulator, while the rest of the system is implemented in another independent simulator. The simulation results of the detailed wind system model show that the hybrid ESS has a lower battery cost, higher battery longevity, and improved overall efficiency over its reference ESS.

This paper gives an overview of hardware-in-the-loop (HIL) simulation mainly used for design, development, analysis, and testing of different power systems and their components. These power HIL simulations are real-time simulations that combine both hardware and software testing in a closed loop configuration. This work outlines the evolution of power system testing approaches, various PHIL implementation requirements such as, digital real-time simulator (DRTS) and different interfacing techniques. In order to verify the proposed hardware and software for HIL testing, an experimental set-up of full-bridge voltage source inverter is developed, having series resonance load, mainly used in induction heating applications. Its digital control is implemented using field programmable gate array (FPGA). Simulation results and experimental results are presented to validate the HIL system.

Field Programmable Gate Arrays (FPGAs) are increasingly being used as a key component of digital systems because of their in-fieldreprogrammability, low non-recurring engineering costs (NRE), andrelatively short design cycle. Recently, there has been greatinterest in using FPGAs within spacecraft. FPGAs, like allsemiconductor devices, are susceptible to the effects of radiation.There is an active research community investigating the effects ofradiation on FPGAs and developing methods to mitigate against theseeffects. There has been significant progress over the last decade inthe understanding and developing FPGA technology that is resistant tothe effects of radiation. The success of FPGAs within spacecraftsuggests that FPGAs may be used in particle physics experiments whereradiation levels are considerable higher than the conventionalterrestrial earth environment. This paper will summarize the effectsof radiation on FPGAs, methods to mitigate against these effects,provide a case study of a successful FPGA system operating in space,and discuss the issues that will affect the use of FPGAs withinparticle physics experiments.