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EPE 2021 - Dialogue session - Grids, Smart Grids, AC & DC
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2021 ECCE Europe - Conference > EPE 2021 - Topic 07: Power Supplies > EPE 2021 - Dialogue session - Grids, Smart Grids, AC & DC
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	A 60 kW Power Hardware-in-the-Loop Test Bench for grid emulation based on a Series Hybrid Cascaded H-Bridge Converter   By Ruediger SCHWENDEMANN	[View]   [Download]
Abstract: In this paper the requirements for a Power Hardware-In-the-Loop (PHIL) system for the emulation of grids and grid faults are discussed. Solutions for all parts of the PHIL system - the power electronics, the signal processing system and the software structure - are presented. Subsequently, an analysis of the accuracy, bandwidth and stability of the PHIL testbench is done and the effects of different interface algorithms are shown. Concluding, measurement results of emulated highly dynamic grid faults such as voltage dips and spikes, distorted grids and weak grid situations are shown, which prove the performance of the PHIL system.
	A Fast and Reliable Commuting Strategy for the Bypass Thyristors in Dynamic Voltage Restorers (DVRs)   By Houkai ZHANG	[View]   [Download]
Abstract: This paper proposed a fast and reliable commuting strategy based on the double voltage step method for the bypass thyristors in the dynamic voltage restorer (DVR), which is implemented in three configurations of the DVR with quantitative parameters design scheme. Theoretical analysis and simulations using MATLAB/Simulink indicates that the proposed strategy is feasible and reliable even for the cases with unreliable current sampling.
	A New DC-DC Converter Linking LCC-HVDC Transmission Networks   By Mohamed ELGENEDY	[View]   [Download]
Abstract: Transferring bulk power via high voltage direct current (HVDC) transmission is dominated by linecommutated converters (LCC). This is due to the robustness and higher ratings of the thyristors as well as the higher converter efficiency. Nevertheless, most of these transmission networks are point to point. This is due to challenges of allowing multi-terminal LCC based networks and power reversal. This paper introduces a new dc-dc converter topology which allows connecting two independent LCC networks. The proposed converter is based on insulated gate commutated thyristors (IGCTs). Utilizing IGCTs allow mimicking similar control and performance as in insulated gate bipolar transistor (IGBT) based voltage source dc-dc converters. However, IGCTs has more superior features over IGBTs such as higher efficiency, higher short circuit current and higher power ratings. Detailed analysis and simulations are provided to validate the proposed converter topology, which confirms its potential in connecting HVDCLCC networks.
	A novel high dynamic six phase 120 kW Power Hardware in the Loop Emulation Test Bench for emulating AC/DC Grids and Electrical Machines   By Lukas STEFANSKI	[View]   [Download]
Abstract: This paper presents a highly customizable 120 kVA Power-Hardware-in-the-Loop test bench. The output stage consist of two identical Parallel Hybrid Converters each with a 17-level output voltage and an effective switching frequency of 1 MHz. The Parallel Hybrid Converters can provide 3-phase AC or bipolar DC as output voltage. Thus, one 6-AC, 3-AC or DC system or two systems with 2x3-AC, 1x3-AC and 1xDC or 2xDC can be emulated.
	An Approach Utilizing Converters for Locating Faults in LV Distribution Grids   By Mikko ROUTIMO	[View]   [Download]
Abstract: This paper proposes an approach for locating faults in a distribution grid by utilizing data measured and gathered by distributed converters. The data, comprising grid voltages and impedances from multiple locations, is processed using multinomial logistic regression, a machine learning algorithm, to classify a fault location in the grid. The algorithm is first trained with simulation data, followed by evaluation of its predictive performance using a set of test data previously unseen by the algorithm. The fault location accuracy of the proposed approach is found resonable and encourages further studies of the unused potential in the converters.
	Assessment of the AC/DC converters resilience to DC grids fault by electrothermal modelling   By Frédéric REYMOND-LARUINA	[View]   [Download]
Abstract: In Low Voltage Direct Current (LVDC) grids DC short circuits can generate very high currents and huge stress for electronic power converters. Assessing their withstanding capabilities is critical. The present paper proposes to couple a thermal and electrical model of an AC/DC converter. This method allows to solve coordination issues between protection selection and converter sizing, as well as ensuring a reliable protection whatever the distance the fault occurs.
	Converter Meets Distance Protection: A Good Match_   By Michael KLEEMANN	[View]   [Download]
Abstract: State of the art distance protection can misoperate in electricity grids fed by power electronic converters. This paper investigates how these converters should inject fault currents to mitigate such misoperations. Three fault current injection strategies are investigated in a transient simulation. Findings are validated in a laboratory setup with a commercial distance protection relay. The main result is that injecting positive and negative fault current to balance the converters' voltages in conjunction with an adapted quadrilateral characteristics can render distance protection effective.
	Cooperative Power Conditioners for Microgrids in Mining   By Juan Sebastian GOMEZ QUINTERO	[View]   [Download]
Abstract: This paper proposes a cooperative control scheme for power quality compensation, exploiting the remaining capacity of power electronics converters typically used in microgrids for active power supply.Consensus terms are proposed to mitigate imbalances and harmonics in a mining-industry microgrid. Incontrast to the classical approach, cooperative power compensation uses not only information from localloads, but also information from neighbouring compensators and power sources. Simulations show thatthe proposed cooperative scheme reduces the unwanted power components similarly than the classicalapproach, but also turns the system robust to communication network changes and converters saturation.
	DC Chopper Energy Dissipation Strategies for Integration of Offshore WindPower Plants via Multi-terminal HVDC Networks   By Alvaro Jose HERNANDEZ MANCHOLA	[View]   [Download]
Abstract: The aim of reaching a climate-neutral electric power supply requires a massive integration of renewable energy sources into the main power grid. Multi-terminal HVDC interconnectors provide the capability to integrate largescale offshore wind energy into the main grid and secure at the same time the required interconnection capacity between various countries. Thus, multi-terminal HVDC networks for integration of offshore wind energy are currently pursued by the industry. This paper aims to offer guidance on finding the most suitable strategy for a shared dissipation of the excess energy in case of faults on the onshore ac side of the HVDC converters. For this different energy dissipation strategies are presented and discussed. Simulation results using PSCAD EMTDC areused to highlight the advantages and disadvantages of the different strategies.
	Effects of Component Failures in Drive Inverters during Parallel Operating on an Open Industrial DC Grid   By Simon PULS	[View]   [Download]
Abstract: An open industrial DC grid for energy supply has many benefits. Also new challenges arise by couplingthe DC link capacitors of all devices, e.g. inverters. This paper presents the effects of component failurescausing short circuit faults in combination with electrically coupled and charged DC link capacitors.Resulting energy flows are shown, which arise in the DC grid in case of faults. In addition, measurementsof short circuit tests and two solutions are shown, which enable the safe and simple operation of an openindustrial DC grid.
	Energy Requirements of Modular Multilevel Converter Submodules and High-level Control Design for Synthetic Inertia Function   By Rayane MOUROUVIN	[View]   [Download]
Abstract: This work introduces a method to define the energy requirements for Modular Multilevel Converter (MMC) internal energy reserves for the sake of AC frequency support. The corresponding control is also proposed, which is compatible with the state-of-the-art MMC grid-forming control structure. Its effectiveness is shown by simulations.
	Experimental Performance Evaluation of a Distributed Secondary Control Strategy for Hybrid ac/dc-Microgrids in the event of Communication Loss/Delay   By Enrique ESPINA	[View]   [Download]
Abstract: This paper evaluates experimentally the performance of a distributed secondary control strategy applied to a hybrid ac/dc-microgrid in the event of common communication issues, such as communication loss and communication delays. The two scenarios are tested on a 24kW hybrid ac/dc-microgrid laboratory-scale prototype.
	Fault-ride-through capability of the VSG-based grid-forming converters   By Edris POURESMAEIL	[View]   [Download]
Abstract: Grid-forming virtual synchronous generator (VSG)-based converter has a promising potential to be used as an interfaced converter for high penetration of renewable energy resources. Although emulating inertia and oscillation damping features in the control scheme of converters is possible, the short-circuit behavior of synchronous machines during fault conditions or other large-signal disturbances is not replicable in these converters, as their semiconductor devices are current-sensitive. This paper proposes a modified control technique for grid-forming VSG-based converters, enabling their fault-ride-through capability during fault situations. The proposed control technique limits converter current to its allowable amount while prevents windup in the outer control loops. To validate the performance of the proposed control technique, simulation results in Matlab/Simulink are provided and discussed in detail.
	Frequency locked loop with frozen mechanism   By Shan JIANG	[View]   [Download]
Abstract: With the increasing penetration of renewable energy systems into the power grid, stability and safe operation during grid faults have become a great challenge. The phase and frequency of the grid voltage are the important information for the acquisition of the reference value of the grid-connected converter control signal and ensure the smooth, reliable and stable operation of the grid-connected converter system. In this paper, a new concept the frequency locked loop with frozen mechanism is proposed, which is used for solving the grid synchronization problem of the power grid under unbalanced and distorted operating conditions. The frequency locked loop with frozen mechanism consists of the frequency-locked loop (FLL) based on the Second-order generalized integrator (SOGI) which tuned at grid frequency and the frequency frozen mechanism which guarantee the stability during the severe faults.
	Fuzzy-based energy management system for isolated microgrids using generation and demand forecast   By Mauricio RODRIGUEZ	[View]   [Download]
Abstract: Energy solutions based on sustainable microgrids have been increasing since isolated areas with difficult access can benefit from these feasible solutions. In this context, this paper presents the design of an energy management system based on a fuzzy logic controller for an isolated microgrid composed of a diesel generator, a photovoltaic generator, and a battery energy storage system. The management strategy uses generation and load forecasting to anticipate the future behavior of the microgrid, while considering that the battery state of charge is within safe limits. The main objective is to maintain an average value of the battery state of charge around 75\% of its nominal capacity to improve and extend its lifetime. Three different scenarios are performed to provide electric power solutions to an isolated community in Ecuador, and the results are compared with a management strategy without forecasting. The results show that generation and load forecasts help the system to deal with constant load variations, avoiding many times that the battery state of charge reaches the safety limits. At the same time, the proposed strategy reduces the production of wasted diesel power.
	Hardware and Software Concept for Distributed Grid-Forming Inverters in Microgrids   By Tobias GÜHNA	[View]   [Download]
Abstract: The increasing decentralization towards distributed grid topologies brings both challenges as well as great opportunities for the installation of grid-forming inverters to ensure stable grid operation in future power systems. This paper presents a hardware design concept of an innovative inverter topology with a grid-forming control approach, specifically for predominantly resistive grids in a scalable microgrid testbed.
	Implementation and Evaluation of a High-Performance Battery Converter System for Providing Synthetic Inertia at Distribution Network Level   By Frank DEBLON	[View]   [Download]
Abstract: This paper presents the implementation and evaluation of a virtual synchronous generator algorithm on a 400 kVA battery converter prototype to provide synthetic inertia at distribution network level. The optimization approach of the VSG implementation is to effectively utilize the damping characteristic of the VSG rotor to achieve an aperiodic inertial power response during sudden power imbalances. Hence, the system is able to provide the maximum synthetic inertia to the grid by fully utilizing the system components without violating safety limits. The impact of the VSG control energy demand and the lifetime of the battery energy storage system are evaluated and possible optimization strategies are suggested. Moreover, the grid frequency constraints needed for the VSG optimization are discussed and gaps within the standards are put up for discussion.
	Integrating Voltage-Source Active Filters into Diode Front-End Rectifiers - Harmonic Mitigation and Power Factor Correction   By Daniel BERNET	[View]   [Download]
Abstract: The ongoing grid integration of power electronic based loads requires the increasing use of power filters in order to maintain a high power quality and stability. To address this challenge, conventional active and passive filters are commonly used to meet the harmonic limits defined by the grid code. They allow the mitigation of voltage and current harmonics, however the filter performance is often subject to a limited frequency range or a frequency dependent harmonic mitigation. This paper presents a novel control scheme with a significantly reduced frequency dependence of harmonic mitigation for a voltage-source active filter configuration. Although high control bandwidth and identification of individual harmonics are not required, the harmonics of a diode front-end rectifier can almost entirely be eliminated, while the active filter load is consistently limited to harmonic currents in steady state and transient operation. As a result, the parallel voltage-source active filter can be designed for a small share of the installed load power and constitutes a promising alternative to conventional power filters.
	Model Predictive Control for Three-Phase Buck-Type PFC Rectifier in Aircraft Applications   By Yuvin KOKUHENNADIGE	[View]   [Download]
Abstract: Highly ef_cient and dense power electronic converters are an essential part of aircraft electrical systems. The Swiss recti_er provides an ef_cient application of AC-DC conversion. However, currently used conventional control strategies, such as carrier-based PWM control, have not been able to produce AC currents that meet aircraft power quality standards for the Swiss recti_er. Model predictive control is a control strategy that has recently become popular with the availability of powerful microprocessors and has the potential to improve power quality issues currently faced by the Swiss recti_er in aircraft applications. Therefore, _nite control set model predictive control is used here speci_cally for current control of DC-switches in the Swiss recti_er. This paper consists a design and optimization of a simulation model. The goal is to model the Swiss recti_er to operate with model predictive control and to limit input AC current's total harmonic distortion to less than 5 \% which would suf_ce for aircraft applications as per military standards. The developed phase-based model predictive controller is simulated with different cost functions and the resulting input current THD and switching frequency are evaluated and compared.
	Multi-timescale Modeling of Fast Charging Stations for Power Quality Analysis   By Lu WANG	[View]   [Download]
Abstract: To accurately simulate the harmonic emission of EV DC fast chargers (DCFCs) and the harmonicvoltage of the power grid to which the chargers are connected, a small time-step, i.e., typically smallerthan 10µs, is required. However, for harmonic assessment, a long timescale, typically a day, isrequired. A conflict between accuracy and time efficiency exists. To address this issue, a multitimescalemodeling framework of fast charging stations (FCSs) is proposed in this paper. In thepresented framework, the DCFCs' input impedance and harmonic current emission in the ideal gridcondition, i.e., the grid impedance is zero and there are no background harmonic voltages, is obtainedfirstly through a converter switch model with a small timescale. Since the DCFC's input impedanceand harmonic current source change in the charging course, the input impedance and harmonicemission at different input power should be obtained. Then, the DCFCs' input impedance andharmonic emission will be used in the fast-charging station modeling, where the DCFCs are simplifiedas their Norton equivalent circuits. In the station level modeling, a bigger time step, i.e., 1 minute, isused, since the DCFCs' operating power can be assumed as a constant in one minute. With thisframework, the FCSs' long-term power quality performance can be assessed efficiently withoutneglecting the DCFCs' small timescale dynamics.
	Optimization of the chip area in 3.3 kV SiC submodules for HVDC converters   By Lukas BERGMANN	[View]   [Download]
Abstract: The content of this paper describes the optimizing of the semiconductor area in HV-SiC MOSFET based MMC HB submodules. This paper propose a design method of reducing the semiconductor area due to the asymmetric arm current in a MMC. The mathematical derivation of the design rule and loss performance compared to the conventional Si HB and SiC HB is presented. A power loss simulation on submodule level shows the final results of power losses, junction temperatures of the components and the overall efficiency at different DC converter currents and AC load angles. The increase of the area specific power capability of all three types of semiconductor device modules in the application of a MMC submodule proves the economical benefit of an optimized HVDC SiC HB.
	Real-time Reactive Power Compensation by Distributed Generation Simulated using GridLAB-D and PSIM   By Isla ZIYAT	[View]   [Download]
Abstract: With the recent increase of inverter-based distributed generation (DG), more opportunities for grid support are being explored. Advanced metering infrastructure (AMI), allows monitoring and communication in the distribution grid, which could enable real-time optimal reactive power compensation by DG units. In this study, a real-time simulation using GridLAB-d and PSIM is used to explore this in a British Columbia, Canada grid. State estimation followed by reactive power optimisation is applied in real-time to both under-voltage and over-voltage grids. This process is shown to improve grid performance at very low cost, by either reducing power loss in the lines, mitigating reverse power flow or improving other objective(s) determined by the utility.
	Reliability analysis of the bus-bar systems in multiterminal HVDC systems   By Miad AHMADI	[View]   [Download]
Abstract: In this paper, novel scrutiny of different types of bus-bar configurations is carried out to support the design of the system taking into account reliability aspects. The selection process of proper bus-bar configuration is dependent on several aspects which are: the degree of reliability, degree of security, cost, maintenance, operational flexibility, and safety as well as the selected fault DC grid protection strategy. The evaluation is carried out by evaluating the impact of different bus-bar topologies and DC fault clearing strategies on system overall reliability by considering equipment failures. In this assessment, switching and reconfiguration events are reflected to reveal realistic numerical results. At the end, a comprehensive comparison amongst different bus-bars is carried out from system point of view that highlights the level of reliability of various bas-bar configurations.
	Retardation in Service of Real Time Fault Detection   By Moneer NABWANI	[View]   [Download]
Abstract: A new method for short circuit fault detection is proposed using instantaneous voltage measurement. Faults are described in terms of lumped fault models and also by distributed models using the telegraph equations. Those equations are solved analytically resulting in a description of the short propagating in the transmission line.
	Supervisory control of post-fault restoration schemes in reconfigurable HVDC grids   By Lucas MOLINA-BARROS	[View]   [Download]
Abstract: This paper studies the use of Supervisory Control Theory to design and implement post-fault restorationschemes in a HVDC grid. Our study focuses on the synthesis of discrete controllers and on the management of variable control rules during the execution of the protection strategy. The resulting supervisory control system can be proven 'free of deadlocks' in the sense that designated tasks are always completed.