Improve Output Voltage Quality Research Articles

Design and Implementation of Modular Multi-Level Converter Based HVDC System for Grid Connection

This paper examines Modular Multilevel Converters (MMC) for harnessing power from offshore wind farms. MMCs use many simple Voltage Source Converter (VSC) submodules, enabling high-voltage and high-power applications. They offer faster response times and lower harmonic distortion than traditional two-level VSCs. The paper addresses modelling challenges due to numerous switching devices and discusses the development of Cascaded Two-Level (CTL) converters, which improve output voltage quality. Overall, the study highlights advancements in MMC technology that enhance HVDC transmission capabilities.

PV Integrated Multifunctional Off-Board EV Charger With Improved Grid Power Quality

This article presents an adaptive notch filter (ANF) based efficient control algorithm for multifunctional grid connected solar photovoltaic (PV) powered electric vehicle (EV) charger to power the EV batteries and simultaneously improve the grid power quality. Furthermore, a multilevel topology is adopted for the grid-facing converter to improve output voltage quality. The ANF accurately estimates the fundamental EV current and grid voltage for generating pure sinusoidal reference current and synchronizing voltage template, respectively. The ANF-based voltage template estimator precisely estimates in-phase and in-quadrature synchronizing voltage templates compared to a phase-locked loop and second-order generalized integrator during nonideal grid voltage conditions. The charger is designed to operate in grid connected operation (GCO) and standalone operation (SO) to optimize the PV generation. In GCO, the charger provides grid current harmonic compensation and reactive power support to the grid. Furthermore, it offers backup power to the residential load during an emergency. The charger control algorithm also includes a grid synchronization technique based on phase error minimization to achieve a smooth and seamless transition from SO to GCO and vice versa. The effectiveness of the proposed control algorithm is validated in a 12.6-kVA <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -board EV charger laboratory prototype. The obtained results verify the charger performance complies with IEEE 1547 standard.

Elimination of Harmonics in Multilevel Inverter Using Multi-Group Marine Predator Algorithm-Based Enhanced RNN

Multilevel inverters (MLI) are becoming more common in different power applications, such as active filters, elective vehicle drives, and dc power sources. The Multi-Group Marine Predator Algorithm (MGMPA) is introduced in this study for resolving transcendental nonlinear equations utilizing an MLI in a selective harmonic elimination (SHE) approach. Its applicability and superiority over various SHE approaches utilized in recent research may be attributed to its high accuracy, high likelihood of convergence, and improved output voltage quality. For the entire modulation index, the optimum switching angles (SA) from Marine Predator Algorithm (MPA) is utilized to control a three-phase 11-level MLI employing cascaded H-bridge (CHB) architecture to regulate the vital element and eliminate the harmonics. The limitation of SHE is that it is difficult to find solutions for nonlinear equations. As a result, specific optimization approaches must be used. Artificial Intelligence (AI) algorithms can handle such a nonlinear transcendental equation successfully, although their time consumption as well as convergence abilities vary. Here, recurrent neural network (RNN) is considered where the hidden neurons are tuned by MGMPA with the intention of harmonic distortion parameter (HDP) minimization, thus called as enhanced recurrent neural network (ERNN). The method’s resilience and consistency are demonstrated by simulation and analytical findings. The MGMPA method is more effective and appropriate than various algorithms including the MPA, Harris Hawks optimization (HHO), and Whale optimization algorithm (WOA), according to simulation data.

High Gain Quasi-Switched Boost Inverter With Optimal Performance Parameters

Numerous Z-source three-phase inverters are developed for realizing higher voltage gain which are suitable to use in hybrid electric vehicle to drive the electric machine. However, higher voltage and current stress of the passive elements and semiconductor devices are the major limitations of the reported Z-source inverters. In this article, a new quasi-switched boost three-phase inverter is proposed which has the following features: 1) very low continuous input current; 2) reduced voltage stress; 3) reduced current stress; 4) shoot through immunity; 5) single stage voltage conversion from dc to ac; and 6) improved output voltage quality by utilizing higher modulation index. The operation, steady-state analysis, and design guidelines for the proposed converter are discussed in detail. To prove the feasibility of the proposed inverter, a comparative analysis is also presented with the state-of-the-art converters. An experimental setup is designed on printed circuit board and tested for 400 W power rating.

Sensor Malfunction Detection and Mitigation Strategy for a Multilevel Photovoltaic Converter

Cascaded H-bridge (CHB) based converters have several advantages including modularity, isolated DC-side voltage, and improved output voltage quality. These multilevel converters are increasingly used in photovoltaic (PV) systems. With the number of H-bridge submodules (SM) and sensors increased due to the cascaded topology, the converter becomes more prone to sensor malfunctions. This article proposes a method to make a CHB-based PV converter resilient to sensor malfunctions using a real-time state estimation–based malfunction detection algorithm. The proposed method is validated using simulation studies in MATLAB/SIMULINK and experimental studies on a test system. It is shown that a nine-level CHB-based PV system can operate normally even when one sensor measurement is missing.

8200호대 전기기관차 객차전원공급장치(HEP)의 출력전압품질향상을 위한 최적화된 PWM 방법

HEP(Head Electric Power) system, supplying 3-phase service power to the coach vehicles, is a kind of special auxiliary power equipment which is boarded on 8200 series electric locomotives in KORAIL. This equipment shares high voltage DC link with a main propulsion converter/inverter systems. It was difficult to use high frequency PWM technique so that GTO has been used as a power device same like the main power system. Due to low PWM frequency(300㎐) of HEP inverter, the output voltage has less power quality comparing to normal SIV(Static Inverter) system. In this paper, an optimal PWM strategy is presented for new IGBT type HEP inverter system. Several PWM techniques were investigated to improve output voltage quality under fixed lower filter inductance and not high PWM frequency. Finally PC simulations have been done to clarify its availability.

An Improved Performance Direct-Drive Permanent Magnet Wind Generator Using a Novel Single-Layer Winding Layout

Direct-drive permanent magnet (PM) generators have become a strong contender in medium and large rating wind energy conversion systems as they not only provide higher efficiency and annual energy production, but also reduce the operational and maintenance cost. PM generators with nonoverlap single-layer windings provide a cost-effective design variation that eases manufacturing, reduces torque ripples, enhances voltage quality, and provides fault tolerant capability. The performance of such machines depends mainly on the proper selection of the pole and slot numbers, which results in negligible coupling between phases. The preferred slots per phase per pole (SPP) ratios eliminate the effect of low order harmonics in the stator magnetomotive force (MMF), and thereby the vibration and stray loss are reduced. This paper proposes a new three-phase winding configuration based on the 20 slots/18 poles five-phase PM machine. The proposed design is compared with the well-known 24 slots/20 poles three-phase PM machine. The comparison shows that the proposed generator offers reduced torque ripples, improved output voltage quality, and less core loss for the same machine volume.

Multiple-Loop Digital Control Method for a 400-Hz Inverter System Based on Phase Feedback

To keep phase balance and improve output voltage quality, a novel multiple-loop control system in 400-Hz inverter power supply based on unipolar sinusoidal pulse width modulation (SPWM) is proposed. The causes of phase imbalance in a three-phase combined inverter power system are analyzed, and a new multiple-loop control strategy based on phase control is presented to eliminate it. For reducing the total harmonic distortion (THD) of high-power inverter output, unipolar SPWM is added with this new control strategy. The designs of drive circuit and snubber circuit are discussed to eliminate dead time effects and voltage oscillation. The stability of the control system is analyzed and the power system and the control strategies are realized with digital signal processing. Contrastive simulation results indicate the advantages and the correctness of this novel controller for inverter. A three-phase combined inverter system based on a multiple-loop control strategy is constructed, and experimental results show that the inverter system can make a phase difference between each phase less than 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , and the THD of output voltage can be controlled within 2%.

Synchronized Symmetrical Bus-Clamping PWM Strategies for Three Level Inverter: Applications to Low Switching Frequencies

The digital control of three-level voltage source inverter fed high power high performance ac drives has recently become a popular in industrial applications. In order to control such drives, the pulse width modulation algorithm needs to be implemented in the controller. In this paper, synchronized symmetrical bus-clamping pulse width modulation strategies are presented. These strategies have some practical advantages such as reduced average switching frequency, easy digital implementation, reduced switching losses and improved output voltage quality compared to conventional space vector pulse width modulation strategies. The operation of three level inverter in linear region is extended to overmodulation region. The performance is analyzed in terms THD and fundamental output voltage waveforms and is compared with conventional space vector PWM strategies and found that switching losses can be minimized using bus-clamping strategy compared to conventional space vector strategy. The proposed method is implemented using Motorola Power PC 8240 processor and verified on a constant v/f induction motor drive fed from IGBT based inverter.