Bisection Algorithm based Indirect Finite Control Set Model Predictive Control for Modular Multilevel Converters

In this work, an idea based on the bisection algorithm is used to reduce the computational burden of indirect finite control set model predictive control (FCS-MPC) for modular multilevel converters (MMCs). The proposed method greatly reduces the search space for reaching the optimal insertion index (number of submodules to be inserted). Therefore, the strategy proposed offers similar steady-state and dynamic performance compared to full indirect FCS-MPC at a much lower computational burden. A new cost function is also proposed for indirect FCS-MPC which eliminates the need for an outer loop or additional control of differential current to regulate the summation voltages in each arm. The results of the proposed strategy are validated through simulations in MATLAB/Simulink.acceptedVersio

A multi‐layer framework for energy efficiency assessment of shore‐to‐ship fast charging systems including onshore batteries

This paper proposes a three-layer framework for energy efficiency evaluation of Shore-to-Ship Charging (S2SC) systems using load-dependent loss models of the components. The considered S2SC system is supplied by the grid but is also supported by On-Shore Batteries (OSB). The presented approach is then used to investigate the impact of the specific design and operational parameters on energy efficiency. Power system architectures for three general S2SC solutions for ac, dc, and inductive charging are defined and compared in terms of energy efficiency. Operational parameters are also considered in the analysis, namely, the grid power ratio, determining the load sharing between the grid and the OSB, as well as the OSB charging profile. A case study is performed with peak charging power of 1 MW, and the most efficient S2SC solutions are identified for both ac- and dc-based onboard power systems. Moreover, it is shown that charging OSB with the highest available power from the grid between the charging breaks would often lead to higher energy efficiency than the maximum utilization of the available charging time. Field data from a real S2SC system is used to verify the estimated energy efficiency by the proposed framework. The analysis of the real case S2SC is then extended to include and verify a projected OSB. © 2022 The Authors. IET Electrical Systems in Transportation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.A multi‐layer framework for energy efficiency assessment of shore‐to‐ship fast charging systems including onshore batteriespublishedVersio

Position Locking for Permanent Magnet Synchronous Machine Propeller Drives in Drones by Hall-Effect Sensor-Assisted Nonlinear Observer

The paper presents a hall-effect sensor-assisted non-linear observer-based solution for position locking of a surface-mounted permanent magnet synchronous motor (SMPMSM) propeller drive in drone applications. The purpose of the position locking is to ensure a fixed motor position at the landing instant to avoid mechanical damage to the propeller. To evaluate the proposed solution, the position locking sequence of the motor drive is studied for two cases, implemented with two different state machines. The first case is relying on an encoder to provide the position feedback signal and serves as a reference for assessing the performance of the proposed solution based on the position estimate from the hall-effect sensor-assisted nonlinear observer. Experimental results show how the proposed solution can provide sufficient performance of position locking without the encoder.Position Locking for Permanent Magnet Synchronous Machine Propeller Drives in Drones by Hall-Effect Sensor-Assisted Nonlinear ObserveracceptedVersio

P-HiL Evaluation of Virtual Inertia Support to the Nordic Power System by an HVDC Terminal

This paper provides an assessment of the effect from virtual inertia provided by an HVDC converter terminal on the Nordic power system. The analysis is based on results from Power-Hardware-in-the-Loop (P-HiL) tests with a laboratory-scale Modular Multilevel Converter (MMC) representing an HVDC terminal interfaced with a real-time phasor simulation of the Nordic grid. The applied control method for providing virtual inertia is utilizing the derivative of the locally measured grid frequency to adapt the power reference for the studied converter terminal. The power injection provided by the converter and the resulting impact on the frequency dynamics of the power system are investigated as a function of the emulated inertia constant and the frequency droop gain. The results demonstrate how the HVDC converter can effectively support the dynamic response of the power system when exposed to large load transients by improving the frequency nadir and reducing the Rate-of-Change-of-Frequency (ROCOF). Keywords: HVDC Transmission , Power-Hardware-in-the-Loop , Real-time Simulation , Virtual InertiaacceptedVersio

Evaluation and Suppression of Oscillations in Inductive Power Transfer Systems with Constant Voltage Load and Pulse Skipping Modulation

This paper identifies how Constant Voltage Load (CVL) characteristics cause Inductive Power Transfer (IPT) systems to exhibit a poorly damped oscillation mode. When operated with pulse skipping strategies such as Pulse Density Modulation (PDM), the skipped voltage pulses can excite this mode and cause severe oscillations that do not appear in systems with a constant resistance load (CRL). The critical mode is identified from a linearized state-space model of the system and two control approaches are proposed for attenuating the oscillations in current amplitude and power flow. Firstly, the influence of the operating frequency on the critical eigenvalue is analyzed and it is shown how slightly off-resonant operation can increase the damping of the oscillation mode. Secondly, an active damping method based on sending current feedback control is studied. The active damping is based on Phase Shift Modulation (PSM) with limited phase shift angles applied to the PDM signal when oscillations are detected. The effectiveness and feasibility of the proposed methods are validated by simulations and experimental results from a small-scale laboratory prototype.Evaluation and Suppression of Oscillations in Inductive Power Transfer Systems with Constant Voltage Load and Pulse Skipping ModulationacceptedVersio

Modeling and Analysis of SOGI-PLL/FLL-based Synchronization Units: Stability Impacts of Different Frequency-feedback Paths

— Second-order Generalized Integrator (SOGI)-based quadrature-signal-generator (QSG) together with either a phaselocked-loop (PLL) or a frequency-locked-loop (FLL) constitute two types of typical synchronization units (i.e., SOGI-PLL and - FLL) that have been widely used in grid-tied converter systems. This paper will reveal and clarify the stability issue of these two synchronization units arising from different implementations of the frequency-feedback-path (FFP) connecting the SOGI-QSG and the PLL/FLL. In this regard, four types of FFP implementations that are frequently seen in the literature will be discussed. Although different implementations of the FFP will not affect the steady-state frequency adaptation, their dynamical effects on the small-signal stability of SOGI-PLL/FLL remain concealed. To this end, this paper will present a comprehensive stability assessment and comparative analysis of SOGI-PLL/FLL focusing on the FFP issue. To extend the applicability and accuracy of discussions, all the analyses will be fulfilled by using a parameter space-oriented stability assessment method formulated in the linear-time periodic (LTP) framework. The obtained results are verified by time-domain simulations, and the main findings are further interpreted by using appropriate analytical models. Index Terms— FLL, PLL, synchronization, SOGI, stability, LTP, frequency feedback.acceptedVersio

Optimal Compensation of Harmonic Propagation in a Multi-Bus Microgrid

This paper discusses how an Active Power Filter (APF) can be utilized for system-wide harmonic mitigation in a microgrid with multiple sources of harmonic distortion located at different buses. A two-bus microgrid system with independent nonlinear loads at both buses is first investigated analytically, and it is demonstrated that it is possible to derive a harmonic current injection from the APF that will minimize the harmonic distortion at both buses. However, analytical optimization of the APF current will be sensitive to parameter variations, will deteriorate when the APF reaches current saturation and cannot be easily extended to larger systems with many loads at different buses. A more practically applicable method for calculating the APF current references, by using the framework of Model Predictive Control (MPC) is instead proposed for the investigated system. Under realistic operating conditions, this approach can obtain further improvement in the system-level harmonic mitigation. The characteristics and performances that are obtained with the analytical solution and the MPC-based control are assessed by time domain simulations in the Matlab/Simulink environment. The results clearly indicate how an MPC-based system-oriented compensation can maximize the utilization of a single APF in a multi-bus Microgrid.© EA4EPQ. This is the authors’ accepted and refereed manuscript to the article

Decentralized Energy Management Concept for Urban Charging Hubs with Multiple V2G Aggregators

This work introduces a decentralized management concept for the urban charging hubs (UCHs) where electric vehicles (EVs) can access multiple charger clusters, each controlled by an aggregator. The given day ahead schedules (DASs) and peak power limits (PPLs) of the aggregators providing grid-to-vehicle (G2V) and vehicle-to-grid (V2G) services can constrain the energy supply. A suitable energy management concept is required to prevent the impact of supply limitations on EV users. In the proposed approach, an electromobility operator (EMO) acting as an authorized entity, allocates incoming EVs into the charger clusters in the UCH. The EMO executes a smart routing (SR) algorithm that jointly optimizes the cluster allocations and charging schedules, minimizing the charging cost for the given dynamic price signals produced by the aggregators. For real-time charging control (RTC) of the charging units, each aggregator solves an optimization problem with periodically updated parameters given by the DAS/PPLs and charging commitments. This work demonstrates the effectiveness of the proposed concept through comparisons against benchmark strategies without SR and RTC. The results highlight that the proposed concept reduces the deviations from the DASs and the violations of PPLs while significantly decreasing unfulfilled charging demand and unscheduled discharge from EV batteries.Decentralized Energy Management Concept for Urban Charging Hubs with Multiple V2G AggregatorsacceptedVersio

System-Wide Harmonic Mitigation in a Diesel Electric Ship by Model Predictive Control

Email Print Request Permissions This paper proposes a system-oriented approach for mitigating harmonic distortions by utilizing a single Active Power Filter (APF) in an electrical grid with multiple buses. Common practice for control of APFs is to locally compensate the load current harmonics or to mitigate voltage harmonics at a single bus. However, the operation of an APF in a multi-bus system will influence the voltages at neighboring buses. It is therefore possible to optimize the APF operation from a system perspective instead of considering only conventional local filtering strategies. For such purposes, Model Predictive Control (MPC) is proposed in this paper as a framework for generating APF current references that will minimize the harmonic distortions of the overall system within a given APF rating. A diesel-electric ship, with two buses supplying separate harmonic loads, with an APF located at one of the buses, is used as study case. The operation with on-line MPCbased optimization of the APF current references is compared to two benchmark methods based on conventional approaches for APF control. The results demonstrate that the MPC generates current references that better utilize the APF current capability for system-wide harmonic mitigation.2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other work

Power oscillation damping method suitable for network reconfigurations based on converter interfaced generation and combined use of active and reactive powers

Power system stabilisers (PSSs) are commonly used in synchronous generators for damping low-frequency oscillations. However, many of these machines have been replaced by converter-interfaced generators (CIGs), such as those used in solar power plants. This means that CIG-based power plants should also contribute to oscillation damping. Moreover, CIGs may use both active and reactive power for power oscillation damping (POD). However, their combined use has been seldom studied in the literature. Moreover, only a few articles have addressed the adaption of POD controllers when the power system changes (e.g., after a fault). In this paper, a POD controller for CIG-based power plants is proposed that is suitable for operation in power systems exposed to reconfiguration. This controller takes advantage of both active and reactive power injection to maximise the damping of the power system. This controller is based only on local measurements so communication systems are not required. Theoretical developments were validated in a laboratory using real power converters including a 75 kVA grid emulator where the two-area benchmark model is emulated and four 15 kVA CIGs operating in parallel connection. The applicability of the proposed controller was also explored for the IEEE 39-bus system.Power oscillation damping method suitable for network reconfigurations based on converter interfaced generation and combined use of active and reactive powerspublishedVersio