Controller Hardware-in-the-loop Research Articles

Unified Platform for Automated Tests of Inverter-Based Resources with Harware-in-the-loop

Testing of inverter-based resources (IBRs) faces challenges in establishing standardized procedures across all product development stages. Most of the testing approaches use Hardware-in-the-Loop (HIL) during the early stages independently from the final product testing, which can lead to discrepant results. To solve these issues, this paper proposes a unified platform for automatically testing IBRs. It can be used during all product development stages, from pure simulation to Controller Hardware-in-the-Loop (CHIL) and finally on the complete commercial product, ensuring uniform test procedures with different test setups. A case study describing compliance tests of grid-connection codes of photovoltaic (PV) inverters are presented to demonstrate the proposed approach. Experimental tests were performed in accordance to Brazilian grid-connection codes in an ISO/IEC 17025 accredited laboratory. The results obtained with the proposed platform in CHIL and full-hardware showed high similarity with the ones obtained with the accredited laboratory, validating the proposed approach. In addition, the platform can be used to perform tests not specified in standards and to verify the performance of IBRs in operating conditions that are often difficult to be tested in laboratory. Ensuring consistent test procedures, the platform facilitates comparable results along all the testing stages, reducing the product development cycle.

Robust integral super-twisting controller for enhanced photovoltaic integration with hybrid battery and supercapacitor storage in DC microgrid

This study relates to the enhancement in performance of a Hybrid Energy Storage System (HESS) over a DC microgrid, particularly toward a fast-accurate controller of the DC bus voltage. Conventional control methods are particularly difficult to implement in order to reduce start-up time with minimum overshoot, resulting in a significant disturbance of the DC bus voltage. To circumvent these problems, we propose an innovative hybrid controller method that combines the Integral Super-Twisting Algorithm (ISTA) controller technique with adaptive gain in regulating DC bus voltage and current. The capacity of ISTA to greatly enhance the system's dynamic responsiveness, guaranteeing steady operation with effective output voltage control, is by far its greatest benefit. Comparative testing found that the conventional PI controller had a rise time of 0.0666 s, a settling time of 0.165 s, and a 17 % overshoot with a steady-state error of 0.02 %. The proposed ISTA controller had a rise time of 0.0016 s, a settling time of 0.0667 s, zero percentage overshoot, and a minimal steady-state error of only 0.0003 %. The above-mentioned issues mostly focused on better sharing power in HESS and a more effective controller of the DC bus voltage. Furthermore, we evaluate the practical feasibility of the suggested controller through hardware-in-the-loop testing. This research lays a foundation for advancing renewable energy integration in DC microgrid, offering a promising avenue for sustainable and resilient power systems. Finally, the effectiveness and applicability of the proposed ISTA controller for DC microgrid use are proven with Controller Hardware-in-the-Loop (C-HIL) simulations.

Hardware in the loop testing of converter control in solar PV and BESS based islanded microgrid

Over the past decades, microgrids have garnered significant attention due to their ability to offer resilient power supply and efficiently integrate renewable energy sources (RESs). The test model includes an islanded microgrid having common voltage source converter for solar photovoltaic and battery energy storage system, characterized by low inertia. To minimize the effect of reduced inertia caused by lack of synchronous generators and also to cope up with the variation in power output from different renewable energy sources, an adaptive virtual inertia and damping based control, is incorporated through voltage source converter control, utilizing swing equation of the synchronous generator. However, it is imperative to verify the proposed control strategy before implementation in an actual plant. In that direction, this paper discusses the practicality of the proposed control in the real-time using Controller Hardware-in-the-Loop (CHIL) platform. So, the plant is built in real time simulator OP4512 and the proposed control is implemented using practical microcontroller TMS320F28379D. Subsequently, configuration and modelling of ADC and EPWM are explained. CHIL testing platform demonstrates flawless compatibility with the converter control, having a system model running in real time. Simulation results are compared with that of HIL results for various loading configurations, hence proving the efficacy of the proposed control strategy.

Controller Hardware-in-the-Loop Testbed of a Distributed Consensus Multi-Agent System Control under Deception and Disruption Cyber-Attacks

The impact of communication disturbances on microgrids (MGs) needs robust and scalable Information Communication Technology (ICT) infrastructure for efficient MG control. This work builds on advances in the Internet of Things (IoT) to provide a practical platform for testing the impact of various cyber-attacks on a distributed control scheme for a Multi-Agent System (MAS). This paper presents a Controller Hardware-in-the-Loop (CHIL) testbed to investigate the impact of various cyber-attacks and communication disruptions on MGs. A distributed consensus secondary control scheme for a MAS within an MG cyber-physical system (CPS) is proposed. The proposed cyber-physical testbed integrates a real-time islanded AC microgrid on RT-Lab, secondary controllers implemented on single-board computers, and an attacker agent on another single-board computer. Communication occurs via a UDP/IP network between OPAL-RT and controller agents, as well as between the agents. Through meticulous experimentation, the efficacy of the proposed control strategy using the developed platform is validated. Various attacks were modeled and launched including deception attacks on sensors, actuators, and their combinations, as well as disruption attacks. The ramifications of both deception and disruption cyber-attacks on system performance are analyzed.

PD-Based Iterative Learning Control for the Nonlinear Low-Speed-Jitter Vibration of a Wind Turbine in Yaw Motion

Aiming at the nonlinear low-speed-jitter (LSJ) vibration suppression for a yaw system of a megawatt wind turbine, a kinematics mechanism of the yaw system is investigated from the perspective of tribology, and a kinematics model of the yaw system based on an equilibrium position is established. On the basis of the dynamic modeling of the yaw system, a nonlinear mathematical model of the LSJ system is deduced. Based on the two lead motors’ driving of the conventional yaw motion, an innovative design with a special installation of two auxiliary motors for yaw transmission is carried out, which is integrated with a matching centralized lubrication system (CLS). Based on open-loop proportional-derivative (PD) control and the iterative learning control methods of the time-varying continuous system, the stability control and jitter amplitude suppression of the yaw system are realized by using a combined driving torque provided by the lead and auxiliary gears. From the stability and convergence of the time-domain response and the convergence of the iterative error, the effectiveness of the iterative learning control method with the PD-based regulation is verified, and its advantages for engineering applications are shown based on the algorithm solver improvement. The feasibility of the physical realization and engineering application of the control methodology is verified by using controller-hardware-in-the-loop (C-HITL) simulation technology.

Enhanced Volts-per-Hertz Sensorless Starting of Permanent Magnet Motor with Heavy Loads in Long-Cable Subsea Applications

Permanent magnet (PM) motors are gaining prominence in subsea applications such as drilling, pumping, and boosting for oil and natural gas extraction. These motors are gradually replacing traditional induction motors. However, starting and operating PM motors at low speeds under heavy loads poses significant challenges. This is because of unknown initial rotor positions and resistive voltage drops due to the presence of a sinewave filter, transformer, and long cable. An unknown rotor position may result in temporary reverse speed, which may cause a loss of synchronism; therefore, initial rotor position estimation is preferable. Additionally, addressing the voltage drop issue requires careful voltage compensation to avoid transformer core saturation. In this paper, an enhanced V/Hz starting of a PM motor is proposed with initial position detection (IPD) and voltage compensation to start the motor reliably with a heavy load. The proposed control method is verified with controller hardware in the loop (C-HIL) real-time simulation using a Typhoon HIL-604 emulator and a Texas Instruments TMS320F28335 digital signal processor (DSP) control card.

Efficient Prototyping of a Field-Programmable Gate Array-Based Real-Time Model of a Modular Multilevel Converter

Field-programmable gate array (FPGA)-based real-time simulation plays a crucial role in testing power–electronic dominated systems with the formation of controller hardware-in-the-loop (CHIL) or power hardware-in-the-loop (PHIL). This work describes an efficient implementation of computation time and resource usage in the FPGA-based study of a modular multilevel converter (MMC) with detailed electromagnetic transients. The proposed modeling technique can be used in continuous control mode (CCM) and discontinuous control mode (DCM) for high-switching frequency semiconductor technologies. An FPGA-based designed solver structure is also presented to take advantage of the parallel features of FPGAs to achieve an ultra-fast calculation speed. In addition, two different switch modeling techniques are discussed with a five-level MMC case study. Experimental results on the NI PXIe platform show the feasibility of the proposed implementation, and a time step of 100 nanoseconds is achieved.

Hierarchical Control of Megawatt-Scale Charging Stations for Electric Trucks With Distributed Energy Resources

Electrifying medium- and heavy-duty trucks is critical to decarbonizing the transportation sector. Energy needs of electric trucks will likely require megawatt-scale charging stations, which could significantly stress the electric distribution grid. Distributed energy resources (DER) can alleviate this stress and reduce charging costs with proper management. To that end, this work develops a hierarchical predictive control algorithm for future multi-port megawatt-scale charging stations that can provide real-time energy management for stations, decide charging rates, dispatch energy storage system (ESS), and provide grid voltage support. We integrate three algorithmic components: (i) an energy management optimization (EMO) that provides supervisory control to DER assets and charging loads at minute scale, (ii) a real-time energy management system (RT-EMS) that heuristically compensates for fast disturbances at sub-second scale, and (iii) a model predictive control (MPC)-based battery management system (BMS) that communicates future charging demands to the EMO, to manage the overall megawatt-scale site. Validation in a controller hardware-in-the-loop (CHIL) environment shows that the hierarchical controller can reduce the total energy consumption from the grid by approximately 28% compared to an uncontrolled case for the station configuration in this paper, without impacting charging time.

Emulation of IEEE STD 421.5/Industrial Excitation Systems Using a Micro-Alternator's Exciter

Micro-alternators, having similar parameters as turbo-alternators, play a significant role in the experimental evaluation of power system dynamics. Early thyristor excitation systems of micro-alternators have limited re-configurable options. Three possible control structures, two closed-loop control structures proposed in the literature and one open-loop control structure proposed in this paper, including a time constant regulator to mimic large machine time constants, are evaluated to emulate any IEEE 421.5 standard excitation system model or interface an industrial excitation system controller hardware in the loop (CHIL). It is shown that the communication delay introduced in CHIL does not impact the closed-loop stability within the bandwidth requirements of the excitation systems. One of the closed-loop structures, which is more generalized, and the open-loop structure performances are compared for emulating IEEE AC4C, DC1C, and ST1C excitation systems on a laboratory micro-machine based single machine infinite bus test system with buck exciter and H-bridge chopper (HBC) exciter using EMTP simulations under small and large disturbances. HBC exciter is used in the experimental validation with both the closed-loop and the open-loop control structures. The proposed open-loop structure is easy to implement and performs better than the closed-loop structure.

Evaluating Power Sharing Performance of Distributed Generators in Microgrids With Hybrid Sources and Mixed Tie-Lines

Proportional output power sharing amongst distributed sources in islanded microgrids is necessary to maintain a good voltage profile, avoid tripping of sources and avoid circulating current flows. Underground (UG) cables are popular in densely populated areas and military applications. However, researchers typically consider microgrid networks with overhead lines (OHL) in their studies. This paper examines the power sharing performance among droop controlled inverters and virtual synchronous generators in a system with mixed tie-line configurations i.e., network sections with both OHL and UG cable tie-lines. Furthermore, two proposed control strategies to vary the virtual impedance linearly as a function of the DG output currents are examined for their effectiveness to improve the proportional power sharing. The studies are performed considering a system with four inverter based sources operated with the popularly used <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$RL$</tex-math></inline-formula> droop controllers through detailed simulations in MATLAB/Simulink. The enhancement of power sharing is verified for both uniform and non-uniform inverter controls, different R/X ratios of the OHL and UG cables, and in a meshed network configuration with different loading conditions. Controller hardware in the loop (CHIL) based experiment validation is carried out in Typhoon HIL with linear, non-linear and induction motor load, showing that proposed control strategy results in enhanced power sharing in addition to damping oscillations due to dynamic loads.

Fault-Tolerant Architectures With Enhanced Bus Protection for Electric/Hybrid Aircraft Systems

This paper introduces two electrical architectures for electric/ hybrid-electric aircraft propulsion systems to address the issues of the radial baseline architecture, where a single bus feeds the four propulsion motors. A fault on this bus results in complete isolation of the bus to which propulsion motors are connected. By using the proposed architectures, the fault can be isolated without having to disconnect all the propulsion motors. This would increase the reliability, redundancy, and robustness of the electrical system, and/or avoid oversizing the components present in the architecture. In this paper, the protection strategy and action of circuit breakers are discussed for different fault conditions. The enhanced fault-tolerant operation of the proposed architectures over the existing radial baseline architecture for the electrified aircraft propulsion (EAP) system is validated for both open circuit and short circuit faults at different locations in the system, using controller hardware in the loop results obtained using typhoon HIL testbed. Furthermore, the feasibility analysis of interconnecting the individual propulsion channels to reduce the over-sizing of components is also discussed.

Event-Synchronous Time-Asynchronous Method for Controller HIL Simulation of 10 kVA Modular Multilevel Converters

This letter presents an event-synchronous time-asynchronous (ESTA) method for controller hardware-in-the-loop (CHIL) simulations of modular multilevel converters (MMCs). The proposed method aims to address the issue of extensive power circuit simulation calculations, which may result in incomplete data interaction within an interaction cycle and subsequently cause CHIL simulation failure. Unlike conventional time-synchronous simulations, the proposed ESTA method employs data interaction events to trigger simulation and control calculations. Furthermore, state and switching events are utilized to drive simulation calculations, reducing the calculation points of the simulator. As a result, the controller and simulator in CHIL systems exhibit synchronous event logic and asynchronous timing. The proposed ESTA method allows for accurate CHIL simulations even when the simulator faces significant computational tasks. The simulated and experimental results from a 10kVA MMC are provided to validate the proposed ESTA method. This letter provides an effective method for simulating large-scale MMCs in the CHIL simulation system, offering a promising avenue for this field.

Capacitor ripple reduction in T-type multilevel inverter operation for solar PV-application

Efficient and reliable power electronic converters are desired to integrate renewable energy sources into households or the grid. Multilevel inverters for their benefits are being explored for low-power applications. In this work, recently introduced 9-level T-Type switched-capacitor multilevel inverters are explored for 11-level operation, increasing their reliability in high-temperature conditions. The operation makes it capable of generating more voltage levels than the prior technology and diminishes capacitor inrush currents. Eventually, in 9-level operation, the undesired continuous high inrush current peaks are inevitable, which heat the capacitors due to electrolytic series resistance (ESR). This leads to early electrolyte evaporation and thus results in capacitance variation and an increase of ESR with time. In order to suppress the capacitor inrush currents, additional inductance of small value in the charging circuit is sought to mitigate these currents, but that leads to increased losses and increased switch ringing effect. In this work, the modulation of the inverter is performed to produce 11-levels at the inverter output. Inverter redundant states are so employed that the capacitors are always charged and discharged through the load. This results in reduction of inrush current peaks by approximately 20 times, thereby increasing the reliability and life of the inverter and making them more suitable for Solar PV applications in harsh weather conditions. This structure and modulation strategy also achieves lower switch voltage and current stresses. The improved topology and the modulation strategy are validated on the controller hardware-in-the-loop (CHIL) setup and PLECS environments. Further, the topologies are experimentally validated on a laboratory prototype.

Control Development and Fault Current Commutation Test for the EDISON Hybrid Circuit Breaker

The DC circuit breaker is an indispensable building block for DC network systems. Hybrid circuit breakers that combine mechanical and solid-state switches have more potential to be utilized in DC distribution networks because of their lower conduction losses and fast interrupt speed. The efficient energy DC interrupter with surge protection (EDISON) removes any solid-state circuit in the main current path, thereby substantially reducing the conduction losses during normal operations. However, it requires a dedicated control with fast dynamics because any false triggering of the mechanical switch or solid-state switches of the breaker would lead to a commutation failure and a potential unquenchable arc. This paper proposes a finite-state-machine (FSM) based control scheme that guarantees an accurate and fast control response during a fault event. Due to this fast response requirement, a dual-core-CPU-based control architecture is applied featuring parallel taskings and negligible communication delays between the two cores. Furthermore, a control-law-accelerator (CLA) is employed to further reduce the latency of the program execution by 33%. The controller hardware-in-the-loop (CHIL) model of the EDISON breaker is implemented in OPAL-RT to verify the control scheme and de-risk the prototype test. A fifth-order RLC network is developed to characterize the mechanical switch behavior such that the hybrid circuit model can be simulated in the CHIL solely by circuit components. Finally, the proposed control scheme is implemented and validated in a prototype test with a 3 kA interrupting current and a 60 A/μs current commutation rate.

Extended Discrete-State Event-Driven Hardware-in-the-Loop Simulation for Power Electronic Systems Based on Virtual-Time-Ratio Regulation

This paper proposes an extended discrete-state event-driven (EDSED) controller hardware-in-the-loop (CHIL) method for power electronic systems, employing virtual time ratio (VTR) regulation to achieve CHIL function. Specifically, the proposed VTR in CHIL simulation is introduced to define the time ratio at which the mathematical model of the power circuit runs in the simulator. Additionally, by adjusting different VTRs, the data interaction between the simulator and controller is modified and employed as an event to trigger both simulation and control calculations, ensuring a precise correlation between simulation data and control information. The proposed EDSED CHIL simulation method is validated through CHIL and full hardware experiments involving a power electronic transformer and a multi-port power router. This paper offers an effective CHIL solution for testing control strategies and codes in power electronic systems characterized by complex coupling and high frequency.

Design and CHIL testing of microgrid controller with general rule-based dispatch

Energy Management for microgrids with various compositions and sizes is challenging for conventional optimization-based approach which requires complex problem formulation and high computing power. A microgrid controller with general rule-based dispatch adaptive to different microgrid compositions and operating modes is presented in this article. Several basic dispatch rules are designed with objectives of balancing the total power, tracking grid power import/export reference, mitigating renewable generation fluctuation and reducing energy storage losses. Mathematical formulation and graphical solutions for rules design are described. The basic rules are then combined to form generalized dispatch strategies capable of operating in different scenarios. Four types of dispatch strategies and their variants in terms of dispatchable generator control are introduced. Recommendation of the dispatch types for different microgrid configurations and the adaptivity to microgrid composition variation are also given. The microgrid controller is validated with comprehensive testing and comparative study under various operating points and modes on a controller hardware-in-the-loop (CHIL) testbed.

Integrating degradation forecasting into distribution grids’ advanced distribution management systems

Advanced distribution management systems (ADMSs) are considered tools for deploying control and management strategies to address challenges in future distribution grids populated with distributed energy resources (DERs). This work presents a framework to integrate a degradation forecasting (DF) layer into ADMSs. Based on observations of considered DERs’ degradation behaviors, a load-dependent degradation model is constructed and integrated into a dynamical Markov chain-based degradation prediction model. Multiple sources of data can be used to train the Markov prediction model, and then Evidence Theory (ET) is used to fuse predicted results from the prediction model to enhance the reliability of the prediction model. Then, the predicted results are used to adjust energy management (EM), which is a component of the ADMS concept, to abate the degradation of components with higher degradation costs. The proposed strategy is verified on the IEEE 33 bus system by numerical simulations. In addition, controller-hardware-in-the-loop (CHIL) experimentation for the proposed scheme is implemented. Both the numerical simulations and CHIL experimentation show operation cost savings for the studied system.

Analysis of transient overvoltages and Self Protection Overvoltage of PV inverters through RT-CHIL

In power systems, Single-Line-to-Ground (SLG) faults are the most common type of fault. When a three-phase four-wire system supplied by an ungrounded synchronous generator is subjected to SLG faults, the unfaulted phases are expected to exhibit significant ground-fault over-voltage (GFOV). Mitigation of this is via effective grounding, as described in IEEE Std 62.92.2. However, for inverter-based resources (IBRs), the physical mechanism that leads to GFOV in synchronous machines is not present. This paper investigates whether GFOV is a problem in IBRs, and whether conventional mitigation requirements, such as providing a grounding transformer (GTF), are suitable for IBR installations. To answer these questions, a Controller Hardware-in-the-Loop (CHIL) based performance analysis is conducted. To this end, different simulation models have been developed to analyze the IBRs control and protection response. The models are comprised of a 13.2 kV, 500 kW distribution system fed by a grid connected PV inverter which was simulated in Typhoon HIL 604 real time simulator, with a IEEE Std 1547-2018 compliant external physical controller connected in the loop. The experimental set-up and tests conducted are explained and results are analyzed, showing that effective grounding requirements are much different than those for traditional generators.

Adaptive online auto-tuning using Particle Swarm optimized PI controller with time-variant approach for high accuracy and speed in Dual Active Bridge converter

&lt;abstract&gt; &lt;p&gt;Electric vehicles (EVs) are an emerging technology that contribute to reducing air pollution. This paper presents the development of a 200 kW DC charger for the vehicle-to-grid (V2G) application. The bidirectional dual active bridge (DAB) converter was the preferred fit for a high-power DC-DC conversion due its attractive features such as high power density and bidirectional power flow. A particle swarm optimization (PSO) algorithm was used to online auto-tune the optimal proportional gain (&lt;italic&gt;K&lt;sub&gt;P&lt;/sub&gt;&lt;/italic&gt;) and integral gain (&lt;italic&gt;K&lt;sub&gt;I&lt;/sub&gt;&lt;/italic&gt;) value with minimized error voltage. Then, knowing that the controller with fixed gains have limitation in its response during dynamic change, the PSO was improved to allow re-tuning and update the new &lt;italic&gt;K&lt;sub&gt;P&lt;/sub&gt;&lt;/italic&gt; and &lt;italic&gt;K&lt;sub&gt;I&lt;/sub&gt;&lt;/italic&gt; upon step changes or disturbances through a time-variant approach. The proposed controller, online auto-tuned PI using PSO with re-tuning (OPSO-PI-RT) and one-time (OPSO-PI-OT) execution were compared under desired output voltage step changes and load step changes in terms of steady-state error and dynamic performance. The OPSO-PI-RT method was a superior controller with 98.16% accuracy and faster controller with 85.28 s&lt;sup&gt;-1&lt;/sup&gt; average speed compared to OPSO-PI-OT using controller hardware-in-the-loop (CHIL) approach.&lt;/p&gt; &lt;/abstract&gt;

Comprehensive Analysis of PV and Wind Energy Integration into MMC-HVDC Transmission Network

Renewable energy will play a vital role in greenhouse gas emissions reduction. However, renewable energy is located far away from the load center. Modular multilevel converter-(MMC) based VSC-HVDC systems became competitive for remotely located renewable energy grid integration. Unlike the average model for MMC and renewable energy side converter, this paper presents a detailed model-based control and analysis of the MMC-HVDC system for solar and wind energy integration. Furthermore, it optimally tracks PV energy employing the modified incremental conductance method and wind energy using field-oriented control. Instead of decoupled control, a feedforward controller is utilized to establish a standalone AC voltage for renewable energy grid integration. This work considers a doubly fed induction generator (DFIG), permanent magnet synchronous generator (PMSG), and squirrel cage induction generator (SCIG) for wind energy integration. The results from MATLAB/SIMULINK platform agree with the controller hardware in the loop results from RTDS-dSPACE platform. The results confirmed the optimum solar and wind energy tracking during wind speed, irradiance, and temperature variations. However, it improved the fault ride-through capability during balanced and unbalanced low voltage disturbances at the point of common coupling (PCC) of AC grid.