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Step increase in power demand at 10 s. (upper) Voltage synchronization between the two interconnected domains. (lower) Prompt change in current drawn analyzed in both domains due to step increase in power demand.
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With increasing changes in the contemporary energy system, it becomes essential to test the autonomous control strategies for distributed energy resources in a controlled environment to investigate power grid stability. Power hardware-in-the-loop (PHIL) concept is an efficient approach for such evaluations in which a virtually simulated power grid...
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... load is replaced by a three-phase dynamic load, the power demand of which is stepped-up during the simulation to observe the imminent current change in both domains. The voltage and current comparison is shown in Figure 6. The plot in Figure 6a shows the comparison of the voltage measured from both domains at the interface bus. ...
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... voltage and current comparison is shown in Figure 6. The plot in Figure 6a shows the comparison of the voltage measured from both domains at the interface bus. In Figure 6b, it can be observed that there is a variation in current magnitude due to the change in power demand at that instant which is also followed by current waveform. ...
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... plot in Figure 6a shows the comparison of the voltage measured from both domains at the interface bus. In Figure 6b, it can be observed that there is a variation in current magnitude due to the change in power demand at that instant which is also followed by current waveform. The change in phasor magnitude is captured dynamically at the same instant as seen by the instantaneous waveform results. ...
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In the last years, the overall system inertia is decreasing due to the growing amount of energy resources connected to the grid by means of power inverters. As a consequence, reduced levels of inertia can affect the power system stability since slight variations of power generation or load may cause wider frequency deviations and higher rate of cha...
Citations
... In addition, a DUT such as a PV inverter may be interfaced on its AC side through a transformer to the power amplifier to match the voltage levels of the solar PV inverters and the grid voltages passed to the amplifier as in [6,7] In most of the literature on PHIL testing for DER integration, the DUTs and their controls are tested in a PHIL environment, not amplifiers [112]. In [112] the authors focus on a power amplifier in current-controlled mode as the actual DUT which could enable the effective use of amplifiers as hardware emulators for DERs in future PHIL integration studies. The methodology of the interface determines which signals are exchanged between the RTS and the external equipment, as well as the timing of those exchanges during the simulation timestep [57]. ...
... Some PHIL power hardware, such as PV and battery inverters, require a DC power input, e.g., provided by a controllable DC source [7]. In addition, a DUT such as a PV inverter may be interfaced on its AC side through a transformer to the power amplifier to match the voltage levels of the solar PV inverters and the grid voltages passed to the amplifier as in [6,7] In most of the literature on PHIL testing for DER integration, the DUTs and their controls are tested in a PHIL environment, not amplifiers [112]. In [112] the authors focus on a power amplifier in current-controlled mode as the actual DUT which could enable the effective use of amplifiers as hardware emulators for DERs in future PHIL integration studies. ...
... In addition, a DUT such as a PV inverter may be interfaced on its AC side through a transformer to the power amplifier to match the voltage levels of the solar PV inverters and the grid voltages passed to the amplifier as in [6,7] In most of the literature on PHIL testing for DER integration, the DUTs and their controls are tested in a PHIL environment, not amplifiers [112]. In [112] the authors focus on a power amplifier in current-controlled mode as the actual DUT which could enable the effective use of amplifiers as hardware emulators for DERs in future PHIL integration studies. ...
Over the past decade, the world’s electrical grid infrastructure has experienced rapid growth in the integration of grid-edge inverter-based distributed energy resources (DERs). This has led to operating concerns associated with reduced system inertia, stability and intermittent renewable power generation. However, advanced or “smart” inverters can provide grid services such as volt-VAR, frequency-Watt, and constant power factor capabilities to help sustain reliable grid and microgrid operations. To address the challenges and accelerate the benefits of smart inverter integration, new approaches are needed to test both the impacts of inverter-based resources (IBRs) on the grid as well as the impacts of changing grid conditions on the operation of IBRs. Power hardware-in-the-loop (PHIL) stands out as a strong testing solution, enabling a real-time simulated power system to be interfaced to hardware devices such as inverters which can be implemented to determine interactions between multiple inverters at multiple points of common coupling on the grid and microgrids. This paper presents a review of PHIL for grid and microgrid applications including recent advancements and requirements such as real-time simulators, hardware interfaces and communication and stability considerations. An illuminating case study is summarized followed by exemplary PHIL testbed developments around the world, concluding with a proposed research paradigm to advance the integration of smart grid-following and grid-forming inverters.
... The amplifier controls the voltage applied, as decided by the voltage regulation model. Focusing on distribution grid stability, in [19], an innovative bench focusing on dynamic behavior simulation was presented. An extensive study was provided on the inaccuracies between the real devices and the virtual model. ...
By empowering consumers and enabling them as active players in the power and energy sector, demand flexibility requires more precise and sophisticated load modeling. In this paper, a laboratory testbed was designed and implemented for surveying the behavior of laboratory loads in different network conditions by using real-time simulation. Power hardware-in-the-loop was used to validate the load models by testing various technical network conditions. Then, in the emulation phase, the real-time simulator controlled a power amplifier and different laboratory equipment to provide a realistic testbed for validating the load models under different voltage and frequency conditions. In the case study, the power amplifier was utilized to supply a resistive load to emulate several consumer load modeling. Through the obtained results, the errors for each load level and the set of all load levels were calculated and compared. Furthermore, a fixed consumption level was considered. The frequency was changed to survey the behavior of the load during the grid’s instabilities. In the end, a set of mathematical equations were proposed to calculate power consumption with respect to the actual voltage and frequency variations.
... Following a hybrid approach by Muhammad et al. based on the concept of Plumier et al. [28,29], the grid simulation was set to run in phasor mode, which allows it to simulate On the grid simulation side, the three-phase reference grid no. 8 for low voltage distribution grids from the MONA 2030 project [23] was modeled in MATLAB/Simulink (release 2020b) using the toolboxes Simscape and Simscape Electrical [24,25]. Therefore, the grid model contained a low voltage grid of 0.4 kV including ten GCPs and a transformer that connects to a virtual medium voltage level of 11 kV. ...
... Following a hybrid approach by Muhammad et al. based on the concept of Plumier et al. [28,29], the grid simulation was set to run in phasor mode, which allows it to simulate large power grids without over-loading the computational capacities of the real-time system. In addition, a conversion from phasor to EMT domain was included to transform phasor values into discrete sinusoidal signals of voltage and current. ...
Due to the increasing penetration of the power grid with renewable, distributed energy resources, new strategies for voltage stabilization in low voltage distribution grids must be developed. One approach to autonomous voltage control is to apply reinforcement learning (RL) for reactive power injection by converters. In this work, to implement a secure test environment including real hardware influences for such intelligent algorithms, a power hardware-in-the-loop (PHIL) approach is used to combine a virtually simulated grid with real hardware devices to emulate as realistic grid states as possible. The PHIL environment is validated through the identification of system limits and analysis of deviations to a software model of the test grid. Finally, an adaptive volt–var control algorithm using RL is implemented to control reactive power injection of a real converter within the test environment. Despite facing more difficult conditions in the hardware than in the software environment, the algorithm is successfully integrated to control the voltage at a grid connection point in a low voltage grid. Thus, the proposed study underlines the potential to use RL in the voltage stabilization of future power grids.
... Through this test, the dynamics (parasitic effects, unwanted power flow, harmonics, consumption deviation etc.) of the HUT as an individual component were observed in real-time. An insight into a similar PHIL simulation performed at DLR-NESTEC to analyze the components response is discussed in detail in this study [13]. Additionally, the accuracy of PHIL simulation, development complications of software-hardware coupled interfaces and latency of the real-time simulation are also being analyzed. ...
This paper describes the Networked Energy Systems Emulation Center – DLR-NESTEC – a platform for research on power grids of the future. The DLR-NESTEC consists of a large number of networked power electronic components with which real hardware can be emulated using a real-time simulation system. The grid networking is realized via cable emulators. The laboratory works with real physical power flows and has a connected load of 800 kVA. In addition to the emulators, real network components can be integrated into the laboratory. The sector coupling is addressed by the coupling of charging infrastructure of electric cars as well as the integration of electricity-controlled heating systems. In addition, hydrogen technologies can be integrated. The laboratory is controlled by a SCADA system coupled to high-resolution measurement equipment. With the help of DLR-NESTEC, various future questions regarding robust and safe operation sector-coupled energy networks can be addressed – for instance the operation of a grid structure with a high share of controllable loads without a superordinate control.
... Por lo tanto, la reducción de la latencia en las pruebas en bucle (HIL o PHIL), es algo crítico para aumentar el ancho de banda, aumentando a su vez la estabilidad y el determinismo de la prueba.3.1.1.2 Estado del arteExisten varios simuladores en tiempo real comerciales, los cuales han sido analizados en diferentes artículos[49,69,70,78,79,80]. El análisis más completo de las características de estos simuladores es el realizado por el grupo de trabajo del IEEE PES sobre simulación en tiempo real de sistemas de potencia y energía[49].En este trabajo destaca la tabla completa, con un resumen de las características más importantes de los simuladores digitales en tiempo real más utilizados, tanto en la industria como en el mundo académico. ...
Los problemas asociados al uso de combustibles fósiles nos están llevando como sociedad a una transición energética hacia las energías renovables. Para su integración, la red eléctrica actual está evolucionando a una red eléctrica inteligente, o también denominada Smartgrid. Pero esta evolución supone un aumento en la complejidad de su funcionamiento, sobre todo en las redes de distribución.
En las redes eléctricas se van a necesitar nuevos equipos, con nuevas funcionalidades, que interactúen y comuniquen con sistemas de otros fabricantes para garantizar en todo momento la calidad y seguridad de suministro, equilibrando la balanza entre generación y consumo. Este salto disruptivo pone en riesgo la gran fiabilidad que estos nuevos equipos deben mostrar durante su operación. Por ello, el desarrollo y mejora de los métodos de prueba para la validación de estos sistemas es clave para el éxito de su despliegue.
El presente trabajo de investigación tiene dos objetivos principales. El primer objetivo es la identificación, análisis y mejora de los métodos de prueba actuales para la Smartgrid, centrándose en aquellos que permitan la verificación y validación de los sistemas de potencia. El segundo objetivo es el lanzamiento de un servicio tecnológico que permita mejorar las capacidades técnicas actuales en el territorio, necesarias para el despliegue del equipamiento requerido en el desarrollo de la Smartgrid.
Para ello, en primer lugar se ha realizado un revisión de los métodos de prueba para equipos de la Smartgrid, clasificándolos según su precio, fidelidad y cobertura. Esta clasificación muestra que la técnica de pruebas que ofrece la mejor relación entre cobertura y fidelidad para sistemas de potencia es Power Hardware-In-the-Loop (PHIL). Además, la disposición de esta bancada por parte de los laboratorios también ofrece otras técnicas de prueba interesantes, tales como la simulación y las restantes técnicas en bucle cerrado (MIL, SIL, PIL y HIL).
Dada las capacidades de esta técnica de pruebas, se ha desarrollado un nuevo procedimiento para el dimensionamiento de una bancada PHIL, recopilando información tanto del equipamiento comercial, como de prototipos y diferentes pruebas desarrolladas en laboratorios. Además, se ha definido y clasificado la información relevante a documentar de una prueba PHIL para poder reproducir el experimento y reutilizar las configuraciones utilizadas. Esta clasificación de la información ha sido utilizada para la creación de una base de datos en línea, permitiendo a los usuarios consultar la información de las pruebas realizadas por otros laboratorios a equipos de interés común, así como incluir la información de sus nuevos experimentos.
También se ha realizado un análisis de los elementos que componen el lazo cerrado de control de una bancada PHIL, proponiendo mejoras que consiguen aumentar la máxima frecuencia de emulación hasta cinco veces respecto las bancadas actuales. Para la ejecución de estas mejoras, se ha realizado el diseño conceptual de una nueva plataforma PHIL, que posibilita la prueba de equipos en varios puntos de conexión de la red eléctrica. A su vez, también se ha desarrollado un simulador embebido que permite la ejecución de modelos multiplataforma y su modelado en herramienta gráfica. Estas mejoras se cierran con la propuesta de un amplificador de corriente de gran ancho de banda, basado en la topología de un convertidor masivamente paralelo.
En el análisis de los requerimientos de los sistemas de ensayo, se ha observado que para aquellas pruebas de sistemas de potencia con un protocolo de maniobra hardware y de comunicaciones muy específico y repetitivo (como por ejemplo, los cargadores de vehículo eléctrico), la utilización de emuladores de potencia puede suponer un ahorro importante en el tiempo de desarrollo y ejecución de los ensayos. Estos emuladores además ofrecen también ventajas operativas en pruebas muy acotadas o repetitivas respecto el método PHIL.
Por este motivo, se presenta el desarrollo de un emulador de vehículo eléctrico V2G para la comprobación de cargadores bidireccionales. El funcionamiento de este emulador ha sido verificado en laboratorio ante un equipo real. Para la realización de este prototipo, dentro de esta tesis se ha diseñado el control de tensión de salida de batería, el filtro de salida utilizando la técnica de espacio de diseño y la implementación del código de su tarjeta de control. También se ha diseñado el control de reactiva para compensar la potencia de los cargadores durante la prueba.
Para finalizar, se presenta el Laboratorio de Estudios y Ensayos de Electrónica de Potencia (LE3P) en las instalaciones de CIRCE, desarrollado en el marco de esta tesis. Este laboratorio ofrece un servicio tecnológico a las universidades, centros de investigación tecnológicos y empresas para el despliegue de nuevo equipamiento de potencia para la Smartgrid. En este servicio se define un modelo de desarrollo en V, complementándolo con el equipamiento utilizable dentro del mismo y las diferentes técnicas de prueba disponibles. Como muestra de este lanzamiento, en los anexos se describen dos pruebas realizadas dentro del LE3P a prototipos desarrollados en proyectos europeos.
... Device under Test (DuT) [8,21], Equipment under Test (EuT) [20] or Physical Power System (PPS) [18] are seldom used. In contrast, Hardware under Test (HuT), is most common [6,[13][14][15][16]20,[22][23][24][25], therefore this abbreviation will be used in this paper. The virtual part of the system which Electronics 2022, 11, 7 3 of 23 has to be modeled and simulated in real time will be referred to as Real Time Simulation (RTS) in the following. ...
Power Hardware-in-the-Loop (PHiL) simulation is an emerging testing methodology of real hardware equipment within an emulated virtual environment. The closed loop interfacing between the Hardware under Test (HuT) and the Real Time Simulation (RTS) enables a realistic simulation but can also result in an unstable system. In addition to fundamentals in PHiL simulation and interfacing, this paper therefore provides a consistent and comprehensive study of PHiL stability. An analytic analysis is compared with a simulative approach and is supplemented by practical validations of the stability limits in PHiL simulation. Special focus is given on the differences between a switching and a linear amplifier as power interface (PI). Stability limits and the respective factors of influence (e.g., Feedback Current Filtering) are elaborated with a minimal example circuit with voltage-type Ideal Transformer Model (ITM) PHiL interface algorithm (IA). Finally, the findings are transferred to a real low-voltage grid PHiL application with residential load and photovoltaic system.
The effective modeling of power distribution grid components has become extremely challenging especially considering the increase of power electronics interface based distributed energy resources (DER). The aim behind is, to optimize the accuracy of the models to precisely evaluate the component response and stability of the system. For this purpose, based on the fundamentals of power hardware-in-the-loop simulation, grid-in-the-loop (GIL) environment is proposed in this study to evaluate the grid stability due to integration of DER. A complete low-voltage (LV) distribution grid is emulated along with active grid participants. Additionally, to study the impact at high voltage levels the emulated grid is firmly synchronized with a medium-voltage (MV) simulated grid. An initial case-study is also performed to demonstrate the interesting dynamic behavior at coupling nodes, that otherwise may not have been depicted in simulation studies. Thus, the approach eases up the need for time-intensive detailed modeling of distribution grid participants and provides a setting to test actual components in grid-connected states. If required, the results can be used to replicate the behavior for simulation studies as an alternate to detailed component models.
Grid stability becomes an issue when incorporating renewable distribution generation into an electrical grid due to voltage fluctuations. This work presents an innovative solution which assists grid planners in carrying out technical and economic analysis of future grids and in taking decisions based on it. A set of tools allows the determination of the renewable energy sources and energy storage systems impact to a given grid concerning technical and economic indicators. Using these tools, a study was conducted comparing model predictive control with photovoltaics-curtailment, volt-watt and volt-var methods for the control of photovoltaics and energy storage power in an existing grid. Some highlights of the analysis are: (i) the given grid supports maximal photovoltaics penetration level of 120% without exceeding the ±10% voltage level limits; (ii) the model predictive control method aiming at the minimization of power exchange in a grid with 60% storage penetration allowed significant increase of photovoltaics penetration to 190% and reduced the maximum voltage level to 1.089pu; (iii) a user-centered design and development of the interface for grid planners resulted in a system usability scale score of 63.9. The tools enable the grid planner to take decisions when planning the future grid.
The real-time (RT) hardware-in-the-loop (HIL) simulation-based testing is getting popular for power systems and power electronics applications. The HIL testing provides the interactive environment between the actual power system components like control and protection devices and simulated power system networks including different communication protocols. Therefore, the results of the RT simulation and HIL testing before the actual implementation in the field are generally more acceptable than offline simulations. This paper reviews the HIL testing methods and applications in the recent literature and presents a step-by-step documentation of a new HIL testing setup for a specific case study. The case study evaluates improved version of previously proposed communication-dependent logically selective adaptive protection algorithm of AC microgrids using the real-time HIL testing of IEC 61850 generic object-oriented substation event (GOOSE) protocol. The RT model of AC microgrid including the converter-based distributed energy resources and battery storage along with IEC 61850 GOOSE protocol implementation is created in MATLAB/Simulink and RT-LAB software using OPAL-RT simulator platform. The Ethernet switch acts as IEC 61850 station bus for exchanging GOOSE Boolean signals between the RT target and the actual digital relay. The evaluation of the round-trip delay using the RT simulation has been performed. It is found that the whole process of fault detection, isolation and adaptive setting using Ethernet communication is possible within the standard low voltage ride through curve maintaining the seamless transition to the islanded mode. The signal monitoring inside the relay is suggested to avoid false tripping of the relay.
