Opal-Rt Technologies (Canada)

With the large-scale development of offshore wind power, MMC-HVDC transmission has become a mainstream grid integration solution due to its advantages of operational flexibility in long-distance power transfer. However, OWFs lack the inherent inertia and voltage support capabilities of traditional synchronous generators, making it difficult to autonomously restore power after grid failures (i.e., black start). The development of grid-forming control is regarded as a key technology to address this challenge due to their fast power response and energy buffering capabilities. This paper proposes a black start strategy for OFWs based on HESS GFM control, where HESS establishes AC voltage and cooperates with wind turbines to gradually restore the MMC-HVDC system with OWF integration. An integration model is developed in HYPERSIM to validate the performances of OWF LVRT and black start integrated with MMC-HVDC both in offline and real-time simulations.

Power-hardware-in-the-loop (PHIL)-based machine emulator systems use controlled power converters to mimic the behavior of an electric machine. In this article, a PHIL-based machine emulation system is proposed for grid-tied three-phase induction machines (IM). Typically, a switched voltage source inverter (VSI) is employed as an emulator converter in the motor emulation system. However, the VSI introduces various harmonics into the motor emulation system. These harmonics are mainly attributed to dead time, switching components, and control signals. These harmonics deteriorate motor emulation accuracy. Thus, it is important to investigate and compensate for emulator converter harmonics in motor emulation systems. As an important source of these harmonics is dead time, a detailed analysis of the dead time effect on motor emulation will be presented first. Subsequently, a novel artificial neural network (ANN)-based harmonic compensation technique is developed to ensure the mitigation of harmonics in the emulated motor currents. The proposed ANN-based intelligent harmonic compensator leads to the improvement of motor emulation accuracy. Experimental results are obtained from the emulator system and a 5 hp squirrel cage induction motor to validate the proposed emulator with harmonic compensation.

In this era of an unprecedented energy transition, the digital representations of dynamic power system models in the time domain for Electro Magnetic Transients including DC (EMTDC) simulations, have become necessary and even mandatory by most grid codes for a range of use cases. This is primarily due to the increased penetration of Inverter Based Resources (IBRs) and other power electronic components like Voltage Source Converters-based High Voltage Direct Current (VSC-HVDC) grids or Multi-Terminal HVDC grids. While accurate, offline EMTDC simulations are limited to some basic, small-scale studies, such as voltage, frequency, fault studies, etc., due to limitations in their performance. In contrast, carefully developed and decoupled models for real-time EMTDC simulations can be both accurate and fast. They can also be leveraged to serve as digital twins/replicas of the existing system to conduct detailed and accurate studies including hardware controllers. In this context, this paper presents a real-time simulation case study of an IBR-dominated, hybrid AC-surrounded Multi-Terminal high voltage DC (AC-MTDC) grid using HYPERSIM on a real-time digital simulator. This paper also includes the integration of Software In-the Loop (SIL) and Hardware In-the Loop (HIL) aspects to show the value of real-time simulations for dynamic and stability studies by considering two different scenarios and by comparing IBR-dominated systems performance with an equivalent synchronous machine (SM)-dominated system.

The rise in inverter-based renewables (IBRs), flexible ac transmission systems (FACTSs), and high-voltage direct current (HVdc) systems, coupled with the retirement of synchronous generating plants, is substantially decreasing inertia in large-scale power systems. Fast controllers of IBRs should stabilize these systems, but they are highly sensitive to fast transients, harmonics, and system imbalances.

Microgrids are well known to be a complex system with many different disciplines involved: communications, power electronics, data management, control systems, power systems, etc. Validating a complete microgrid system in the design stages considering all of these disciplines might become a complex problem given the need of integrating different computational and hardware platforms. Real-time simulation represents a feasible, accurate, and affordable way of performing such validations. With it, some or all the parts of the microgrid system can be simulated in real-time such that the particular device under test believes it is connected to the real microgrid components. Different strategies for performing real-time simulation are used: Hardware-in-the-loop (HIL), Control HIL, Software HIL, and Power HIL. Depending on the nature of the device under test, one or many of these strategies can be used during the validation stage. This chapter explains each of the testing strategies involved in real-time simulation. Also, important information regarding modeling and solving circuit devices for microgrid applications is presented. Finally, some practical application examples are presented to help the readers conceptualize their validation/experimental methods.

The need for modeling different aspects of microgrid design and operation has seen the development of various tools over time for different analysis purposes. In this study, Modelica has been adopted as the language of choice to construct a University Campus Microgrid model, utilizing the Modelica Standard Library and the OpenIPSL library. This paper explores the advantages of utilizing Modelica for campus microgrid modeling, emphasizing its benefits and unique features. Modelica features, such as the use of record structures and replaceable templates prove to be particularly advantageous for the modeling task, enabling flexibility and efficiency in the modeling process. Furthermore, comprehensive validation tests are conducted to ensure the accuracy and reliability of sub-systems (e.g. specific power generator systems), before assembling the microgrid network model as a whole. The results demonstrate the efficacy of Modelica in accurately modeling and simulating microgrids, highlighting its potential for advancing microgrid research and development.

Power hardware-in-the-loop based motor emulation system is attracting research attention in recent years as it can enhance electric machine and drive testing. This paper analyzes machine emulation systems based on three mainstream hardware technologies to compare their performance and limitations. The first emulator system uses a conventional IGBT based hard switching power converter, the second one uses a high bandwidth soft switching power converter and the last one uses a linear amplifier. Detailed configuration and control descriptions for these three machine emulator systems are first presented. Comparative experimental studies are then conducted based on the emulation of a laboratory induction machine (IM) using these three different emulator systems. Moreover, experimental results obtained from the emulators are compared against the experimental results of the physical IM to verify their emulation performance. Finally, obtained results from these configurations are compared and analyzed in terms of accuracy, total harmonic distortion, and bandwidth.

This paper presents a method for modeling and real-time (RT) hardware-in-the-loop (HIL) simulation of the multi-active bridge (MAB)-based cascaded solid-state transformer (SST). These types of circuits are challenging for the realm of RT HIL simulation testing due to their high switching frequency, large circuit size, and the high number of switches. The proposed method uses an equivalent circuit and switching function approach to model MAB-based SST. The model is implemented on a field-programmable gate array (FPGA) and achieves time steps ranging from 130 ns to 370 ns, depending on the circuit size and allows switching frequencies ranging up to 150 kHz. To demonstrate the effectiveness and performance of the model, a multi-rate HIL RT test bench is developed. A 3-phase three-stage ac-ac system including 100 kHz 5-winding MABs is considered as a case study. To test both HIL and rapid control prototyping simulation, the plant and controller run on two independent real-time simulators, and fiber optic cables are established to exchange measurements and gating pulses. The developed test bench showed high model fidelity and real-time performance in various circuit conditions.

In the control of DC/AC switched power converters (SPC), one of the most important aspects to be considered is the selection of the real-time control platform. The real-time control platform must be able to meet the high performance efficiency and regulation requirements of the DC/AC SPC, as these typically operate at switching frequencies in the order of kHz to MHz. For this reason, the hardware characteristics of the ADC and PWM, and the processing capacity of the real-time control platform are of vital importance when implementing advanced digital controllers that maintain voltage and current levels within regulatory standards. In this context, we aimed to perform a comparative study of the computation times of different real-time control platforms when implementing different control strategies for DC/AC switched power converters. We also analyzed the impact of the real-time control platforms on the THD of the voltages generated by the DC/AC switched power converters. With the help of this paper, researchers and developers will have criteria to select which real-time control platform to use in real-time control for DC/AC SPC applications.

Smart Transformers (STs) have a key role to play in establishing hybrid ac/dc grids. This paper focuses on challenges in ensuring high-fidelity Real-Time Simulation (RTS) of switching models of STs, in particular on the RTS of a switching model of the Dual-Active Bridge (DAB) converter utilized for the dc/dc power conversion stage. Phase-shifted modulation used for the operation of DAB converters requires a relatively small simulation time-step to achieve a sufficient level of simulation fidelity. An analytical condition for the upper limit of the simulation time-step required to achieve a predefined level of simulation fidelity for a given switching frequency and operating range of the phase-shift angle of a single-phase DAB converter is introduced in this paper. However, the size of the simulation time-step must be sufficiently large to allow the calculation of the switching model of the entire power-converter system in real time, which might be in conflict with the requirement in terms of simulation fidelity. In this case, a method of oversampling the switching signals is proposed, which allows for the utilization of a simulation time-step feasible for real-time model calculation while sampling switching signals at a rate higher than the simulation time-step. Using the approaches mentioned above, the paper provides validation of the simulation fidelity of RTS of switching models of DAB converters in open-loop operation and closed-loop operation with controlled output voltage.