Model predictive control of a single-phase five-level VIENNA rectifier

Power converters and control strategies are very vital for the increasing sustainability of the power grid targeting smart grids. In these circumstances, it is proposed a novel single-phase five-level (SP5L) VIENNA rectifier digitally controlled by a model predictive control (MPC) with fixed switching frequency, which can be useful for a variety of applications with a robust current tracking. The proposed SP5L VIENNA rectifier is an advancement of the classical three-level VIENNA rectifier, also contributing to preserve power quality, and exhibiting the advantage of operating with more voltage levels at the expense of few additional switching devices. The proposed topology is introduced and correlated with the classical solutions of active rectifiers. The operation principle is introduced and used to describe the MPC, which is given in detail, as well as the necessary modulation strategy. The results were obtained for a set of various operating conditions, both in terms of reference of current and grid-side voltage, as well as in steady-state and transient-state, proving the benefits of the proposed SP5L VIENNA rectifier and the accurate and precise use of the MPC to control the grid-side current.This work has been supported by FCT -Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017, and by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

Novel single-phase five-level VIENNA-type rectifier with model predictive current control

A novel single-phase five-level active rectifier based on the VIENNA-type rectifier with model predictive current control is presented. The proposed topology operates in unidirectional mode, imposing a sinusoidal grid-side current with unitary power factor. A unidirectional electric vehicle battery charger is the target application in which the proposed rectifier is used; however, it can also be used as an active rectifier for other purposes aiming to improve the efficiency of ac-to-dc rectification. The model predictive current control is used to select the active rectifier state during each sampling period, trying to minimize the grid current error and obtain low total harmonic distortion. The suitability and performance of the proposed topology of active rectifier, as well as the principle of operation and the digital control algorithm, are evaluated through simulation and experimental results.This work has been supported by COMPETE: POCI-01- 0145–FEDER–007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 – POCI – 01–0145–FEDER–016434.info:eu-repo/semantics/publishedVersio

Performance Improvement in Passive Backscatter Based RFID System with Low DCR Modulations

This paper presents application of the low Duty Cycle Ratio (DCR) modulations: isochronous Digital Pulse Position Modulation (DPPM) and anisochronous Digital Pulse Interval Modulation (DPIM) in backscatter based passive RFID communication system. The proposed modulations are compared to commonly used Amplitude Shift Keying (ASK) modulation. Low DCR modulations are customized for data transmission through inductively coupled link between reader and the tag operating at frequency of 13.56 MHz. The RFID system is mathematically formulated and the performances of the tag are evaluated for each modulation. Observed parameters are modulation depth of backscattered signal, voltage-current characteristics of tag rectifier circuit and ripple of rectifier output voltage. The application of proposed low DCR modulation techniques improves the performance of the RFID system by up to 250%

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

Hybrid three-phase rectifiers with active power factor correction: a systematic review

The hybrid three-phase rectifiers (HTR) consist of parallel associations of two rectifiers (rectifier 1 and rectifier 2), each one of them with a distinct operation, while the sum of their input currents forms a sinusoidal or multilevel waveform. In general, the rectifier 1 is a GRAETZ (full bridge) (can be combined with a BOOST converter) and the rectifier 2 combined with a DC-DC converter. In this HTR contest, this paper is intended to answer some important questions about those hybrid rectifiers. To obtain the correct answers, the study is conducted as an analysis of a systematic literature review. Thus, a search was carried out in the databases, mostly IEEE and IET, and 34 papers were selected as the best corresponding to the HTR thematic. It is observed that the preferred form of power distribution in a unidirectional hybrid three-phase rectifiers (UHTR) is 〖55%P〗_o (rectifier 1) and 〖45%P〗_o (rectifier 2). For the bidirectional hybrid three-phase rectifiers (BHTR) the rectifier 1 preferably takes 〖90% of P〗_o and 〖10% of P〗_o are processed by rectifier 2. It is also observed that the UHTR that employ the single-ended primary-inductor converter (SEPIC) or VIENNA converter topologies in their rectifier 2, can present sinusoidal input currents with low total harmonic distortion (THD) and high Power Factor (PF), even succeeding to comply with the international standards. The same can be said about the rectifier that employs a pulse-width (PWM) converter of BOOST topology in rectifier 2. In short, the HTR are interesting because they allow to use the GRAETZ full bridge topology in rectifier 1, thus taking advantage of its characteristics, being simple, robust and reliable. At the same time, the advantages of rectifier 2, i.e., high PF and low THD are well used. In addition, this article also points out the future direction of research that is still unexplored in the literature, thus giving opportunities for future innovation

Feasability demonstration of the Vienna type excitation system for synchronous generators

The operation of the Vienna rectifier has been analyzed and relevant literature on the rectifier has been reviewed. Furthermore, the Vienna rectifier in scope of rotating power electronics in brushless excitation has been discussed and found to be an viable option. The Vienna Rectifier have been simulated with the parameters from the Svante testrig in Matlab Simulink with satisfactorily results. A re-connection of the main windings is necessary. Also demagnetizationstrategies and necessary modification to the Vienna Rectifier has been discussed and simulated. A demonstration of the Vienna Rectifier were build, but experimental results are remain qualitative due to practical issues with the demonstration rig. The control were designed in LabView Instruments and the workings of the control-scripts were confirmed. The main challenge is comes from dealing with the large inductance from the mains winding on the rotating exciter, but this challenge may be overcome. Additional circuitry consisting of a chopper on the output and demagnetization resistor and switch should be added to ensure better controllability and demagnetization-capability.M-M

Full Digital Control and Multi-Loop Tuning of a Three-Level T-Type Rectifier for Electric Vehicle Ultra-Fast Battery Chargers

The rapid development of electric vehicle ultra-fast battery chargers is increasingly demanding higher efficiency and power density. In particular, a proper control of the grid-connected active front–end can ensure minimum passive component size (i.e., limiting design oversizing) and reduce the overall converter losses. Moreover, fast control dynamics and strong disturbance rejection capability are often required by the subsequent DC/DC stage, which may act as a fast-varying and/or unbalanced load. Therefore, this paper proposes the design, tuning and implementation of a complete digital multi-loop control strategy for a three-level unidirectional T-type rectifier, intended for EV ultra-fast battery charging. First, an overview of the operational basics of three-level rectifiers is presented and the state-space model of the considered system is derived. A detailed analysis of the mid-point current generation process is also provided, as this aspect is widely overlooked in the literature. In particular, the converter operation under unbalanced split DC-link loads is analyzed and the converter mid-point current limits are analytically identified. Four controllers (i.e., dq-currents, DC-link voltage and DC-link mid-point voltage balancing loops) are designed and their tuning is described step-by-step, taking into account the delays and the discretization introduced by the digital control implementation. Finally, the proposed multi-loop controller design procedure is validated on a 30 kW, 20 kHz T-type rectifier prototype. The control strategy is implemented on a single general purpose microcontroller unit and the performances of all control loops are successfully verified experimentally, simultaneously achieving low input current zero-crossing distortion, high step response and disturbance rejection dynamics, and stable steady-state operation under unbalanced split DC-link loading