This paper introduces an enhanced commutation method applied to the indirect matrix converter topology. It is based on the detection of the load current polarity so as to cancel the turn-on delay ...times of the load-side converter's switches. The proposed method allows the grid-side converter devices to commutate at zero current with larger time interval widths provided for this safe commutation. Moreover, it has been shown through experimental results, carried out on a laboratory prototype of the matrix converter, that a substantial improvement of line current total harmonic distortion is achieved.
This paper presents a new family of buck type power factor corrector rectifiers that operates in continuous-conduction mode (CCM) and generates a multilevel voltage waveform at the input. Due to CCM ...operation, commonly used ac-side capacitive filter and dc-side inductive filter are removed from the proposed modified packed U-cell rectifier structure. Dual dc output terminals are provided to have a five-level voltage waveform at the input points of the rectifier where it is supplied by a grid via a line inductor. Producing different voltage levels reduces the voltage harmonics which affects the grid current harmonic contents directly. Low switching frequency of the proposed rectifier is a distinguished characteristic among other buck type rectifiers that reduces switching losses and any high switching frequency related issues, significantly. The proposed transformerless, reduced filter, and multilevel rectifier topology has been investigated experimentally to validate the good dynamic performance in generating and regulating dual 125-V dc outputs terminals as telecommunication boards feeders or industrial battery chargers under various situation including change in the loads and change in the main grid voltage amplitude.
This paper proposes a real-time DSP- and FPGA-based implementation method of a space vector modulation (SVM) algorithm for an indirect matrix converter (IMC). Therefore, low-cost and compact control ...platform is built using a 32-bit fixed-point DSP (TMS320F2812) operating at 150 MHz and a SPARTAN 3E FPGA operating at 50 MHz. The method consists in using the event-manager modules of the DSP to build specified pulses at its PWM output peripherals, which are fed to the digital input ports of a FPGA. Moreover, a simple logical processing and delay times are thereafter implemented in the FPGA so as to synthesize the suitable gate pulse patterns for the semiconductor-controlled devices. It is shown that the proposed implementation method enables high switching frequency operation with high pulse resolution as well as a negligible propagation time for the generation of the gating pulses. Experimental results from an IMC prototype confirm the practical feasibility of the proposed technique.
A new configuration of three-phase Wye Packed U-cells (Y-PUC) with a single DC source is proposed in this paper. In fact, this configuration represents a single DC source modular three-phase PUC ...converter. The DC source on PUC topology is replaced by a flying capacitor to obtain a suitable submodule. Moreover, the modularity of the Y-PUC configuration makes it an appropriate alternative for MMC applications. Furthermore, the proposed structure is an advantageous configuration for high voltage applications such as high voltage direct current (HVDC) transmission lines with the capability of DC fault handling. All PUC topologies such as PUC5, PUC7, PUC9, PUC15 can be replaced in the modules of this proposed single-phase and three-phase configuration to multiply the load voltage levels for improving the output waveform. Active voltage balancing technique through carrier-based modulation is applied. System modeling and operating sequences are developed. Simulation and experimental results are presented and discussed to validate the performance of the proposed structure.
Uninterruptible power supply (UPS) is the promising candidate to ensure high quality of delivering power from renewable energy resources to the AC loads especially sensitive and critical ones. In ...this study, optimised harmonic elimination modulation technique is extended to four-leg neutral-point-clamped (NPC) with neutral point voltage balancing and it has been experimentally validated. It is demonstrated that by controlling the fourth leg to eliminate more harmonics while operating at low switching frequency makes the four-wire NPC an ideal candidate for an UPS application in energy conversion systems. Non-triplen, 5th to 23rd harmonics orders from the output voltage waveforms are eliminated by optimally computing the switching angles for phase legs. Moreover, switching angles computed for the fourth leg are also considered to help removing triplen harmonics containing 3rd, 9th, 15th, and 21st orders from phase voltages. It is mathematically proved that the designed selective harmonic elimination technique ensures the neutral point voltage balancing. The obtained experimental results confirm the proper performance of the proposed technique in supplying symmetrical/asymmetrical loads from renewable energy resources while keeping the inverter neutral point voltage balanced.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This paper presents an insight into a digital twin concept based on finite element simulator of a large hydro generator. The digital twin is created using finite element technique to design, study, ...monitor and to perform tests including analysis of a large hydro generator operating in normal and both margins of the capability curve. A three-phase synchronous machine generator of 310MVA, 56 poles, 13.8kV was considered for the case study. The created model was validated according to the IEEE standard 115. The presented and discussed results are related to the air gap magnetic flux density distribution and damper bar currents for operation in both under and over excitation modes.
This paper focuses on enhancing the resilience of Power Park Modules (PPMs), connected to the grid via power electronic units, under asymmetrical voltage sag conditions. We particularly address three ...interconnected constraints crucial for Low-Voltage Ride-Through (LVRT) capability of PPMs: grid voltage support, overcurrent protection, and the DC-link voltage quality. Existing literature often overlooks the holistic consideration of these factors, prompting this study to introduce and compare three flexible LVRT strategies compliant with recent German grid codes. The proposed strategies use distinct approaches to reinforce the LVRT capability of the PPMs. Strategy A employs static gain factors to control positive- and negative-sequence reactive current (PSRC and NSRC) and the negative sequence of the active current (NSAC). Strategy B aims to enhance the DC-link voltage quality by eliminating real power oscillations through the flexible choice of NSAC and gain factors controlling PSRC and NSRC. Strategy C enhances DC-bus voltage quality by eliminating NSAC and employing flexible equal gain factors for PSRC and NSRC, mitigating both real and imaginary power oscillations. Testing on an inverter-based PPM, involving 400 kW PV module and 200 A, storage system, reveals the superior performance of strategy C. Additional tests evaluate Strategy C's performance with var/voltage regulation equipment (On-Load-Tap-Changing transformer), demonstrating stable and promising performance. Through the introduced approaches, the authors believe that this research work is useful for developing future grid codes and improving the safety and reliability of grid-connected power systems.
This paper proposes a novel 11-level improved active-neutral-point-clamped (11L-IANPC) converter for ground power unit (GPU) application. This hybrid topology consists of the 5L-ANPC and the proposed ...low-voltage submodule. The proposed 11L-IANPC converter possesses only one flying capacitor (FC) and reduced number of high-frequency switches. Hence, voltage diversity and ratings, stored energy, and the number of costly and bulky FCs are significantly decreased. Moreover, operating the augmented submodule at the low voltage and power leads to doubling the number of output voltage levels, whereas the low extra cost and size are imposed on the proposed converter. In addition, suggested sensorless switching method leads to self-balancing of FC and significantly amends the output voltage frequency spectrum. These improvements cause significant reduction in control complexity of the proposed 11L-IANPC converter, remarkable decrease in size of the bulky and costly output LC filter, and improving the dynamic and steady-state performance of the proposed static GPU. The simulation and experimental results validate the feasibility of the proposed converter as well as its suggested modulation and control method.
Literature reviews affirm the constructive influence of the Intelligent Predictive Multi-objective Control (IPMOC) on the power quality, power ancillary services, efficiency, and reliability expected ...from grid-tide Transformerless Multilevel Converters (TMLC). Regarding, this paper contributes to developing the Intelligent Predictive Multi-objective Control (IPMOC) concept in terms of training, Autonomous Power Management (APM), and real-time harmonic mitigation. In the proposed IPMOC, Model Predictive Control (MPC) adjusts the power, regulates the dc-link capacitors' voltages, reduces the switching transitions, suppresses CMV, and alleviates harmonics using a novel real-time Selective-Predictive Harmonic Mitigation (SPHM) objective. As the intelligent part, two Artificial Neural Networks (ANN) trained by a novel data-free, Fast, Self-Training Strategy (FSTS) reinforce the MPC to handle the multi-objective task. The first one adapts the weighting factors of the MPC dynamically, while the second one as a model-free controller autonomously adjusts the active and reactive power references of the MPC to assure the unity power factor of the grid in the presence of unknown loads. The proposed IPMOC has been applied to a three-phase neutral point clamped converter and evaluated via various test scenarios run by dSPACE 1202 and MATLAB to verify its effectiveness and feasibility.
This paper presents a novel model-free switching and control method for three-level neutral point clamped (NPC) converter using deep reinforcement learning (DRL). Our approach targets two primary ...control objectives: voltage balancing and current control. In this method, voltage balancing, current control and selection of optimal switches are achieved using a reward function which is calculated based on various signals measured as observations of the DRL agent. Since the action space is discrete, a deep Q-network (DQN) agent is utilized. DQN is used due to its capability of handling high-dimensional state spaces. In order to highlight its pros and cons, the proposed method is compared with model predictive control (MPC), which is another popular non-linear control method for power electronic converters. The proposed method is evaluated and compared with the MPC method in grid-connected mode using simulations in Matlab/Simulink. To evaluate the practical performance of the DRL method, various experimental results are obtained. The simulation and experimental results demonstrate that the proposed method effectively achieves accurate voltage balancing and ensures steady operation even in the presence of various dynamic changes, including variations in the reference currents and grid voltage. Additionally, the method successfully handles uncertainties, such as sensor measurement noise, and accommodates parameter variations, such as changes in the capacity of the DC-link capacitors and line impedance. The results demonstrate that this method exhibits superior adaptability to real-time changes and uncertainties, delivering more robust performance compared to similar conventional methods like MPC. Thus, this method can be considered a promising approach for intelligent control of power electronic converters, especially when conventional methods such as MPC face challenges in performance and accuracy under severe parameter variations and uncertainties.
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