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This paper utilised a solid‐state transformer (SST) with an active clamped L‐L type current fed front‐end converter for maximum power extraction (MPE) and voltage boost operation. The proposed system employed perturb and observe (P&O) based MPE and upheld the ZVS operation of all primary side switches and ZCS operation of all secondary side rectifier diodes for various insolation conditions. The proposed system developed a new fundamental extractor titled multi‐level cascaded dual double fundamental signal extractor (MCDDFSE) and is utilized in the control algorithm for synchronization with the utility grid. The main objective of the proposed system was to deliver a compact size, reduced weight and cheaper magnetic components‐based front‐end converter of SST on the photovoltaic (PV) array side and a fast, secure and trustworthy mitigation technique for the grid current harmonics on the utility grid side. The proposed system was trialled on the platform of OPAL‐RT (RT‐LABv2021.3.2.307) for various grid abnormalities and its behaviour was found well within the IEEE 519 standards. [ABSTRACT FROM AUTHOR]

Standalone DC microgrids (SDCMGs) are emerging as prominent solutions to remote customers. As these SDCMGs mainly depend on renewable energy sources to curb carbon emission, reliability of the system is lessened due to their intermittent nature. The battery could offer a solution to this problem as it is inherently enclosed by DC grid for power balancing, but the purpose may not be served completely due to high capital cost and maintenance. Thus, the diesel generator (DG) becomes a major alternative to overcome this issue because of low investment, high compatibility, and flexibility. However, DG inhibits with cranking delay, sluggish response and low fuel efficiency under frequent switching and variable loading scenarios. To suppress the issues, a new power management strategy (PMS) is developed to ensure proper coordination between different sources, storage devices and loads in SDCMG. In addition to this, an effective control scheme is also proposed to achieve seamless regulation of DC bus voltage even under extreme conditions. In this study, different SDCMG configuration is considered for testing and simulation of system is carried out in real‐time digital simulator to prove their viability. A scaled prototype is developed to validate simulation results and authenticate proposed PMS and control scheme. [ABSTRACT FROM AUTHOR]

In this study, an off-board multi-terminal dc charger with active input current shaping for level-3 electric vehicle (EV) charging applications is proposed. The configuration is based on reduced switching state multi-point clamped, three phase improved power factor converter and supplied by the standard ac grid. The topology has the advantage of reduced device count along with reduced maximum device stress. This will increase the speed of EV charging and enables the reduction of capital and maintenance costs of the charging facilities, enhancing further expansion of the eco-friendly transport. In addition, one of the key performance indicator, i.e. the fault ride-through capability, is investigated in the proposed topology under various unbalanced input conditions. Further, steady-state and transient performance of topology during load, as well as, dc-link voltage change is presented. Minimum distorted and balanced line currents are drawn from supply by implementing negative sequence elimination control algorithm. The validation of the proposed topology is verified with simulation and a down-scaled experimental setup. [ABSTRACT FROM AUTHOR]

In this study, a new multi-point clamped (MPC), three-phase two-leg, five-level unidirectional front end high-powerfactor converter is proposed for directly connected wind energy conversion system with a permanent magnet synchronous generator. The proposed topology can be modelled and modulated similarly to other existing MPC structured converters with the omission of clamping diodes and bidirectional switches. The proposed converter has an advantage of reduced power semiconductor device count and maximum device stress. A factor (normalised index) is introduced and comprehensive comparative analysis with N level existing topologies is carried out. The minimum value of the normalised index makes the proposed topology as a suitable option for medium-voltage and high-power applications. Also, the fault ride through capability is one of the key performance indicators is also investigated on proposed topology under voltage sag condition. Further, steady state and transient performance of topology during load as well as dc-link voltage change are presented. Minimum distorted and balanced line currents with unity power factor are drawn from supply by implementing negative sequence elimination control algorithm. The validation of proposed topology is verified with simulation and a down-scaled experimental setup. [ABSTRACT FROM AUTHOR]

Neutral point (NP) clamped (NPC) inverters produce low-frequency NP voltage oscillations when modulated with nearest three-vector (NTV) methods for certain loading conditions. Non-NTV modulations can address these oscillations at the expense of increased switching frequency, output voltage distortion and complexity. This study presents a new generalised algorithm to implement hybrid modulation strategies which can also eliminate NP voltage oscillations using a combination of the aforementioned methods. The proposed algorithm avoids abrupt changeover between the two modulations and ensures minimum contribution of non-NTV operation and hence its drawbacks. Moreover, the algorithm is computationally efficient compared with its counterparts, since it only uses redistributed NTV duty ratios to generate NTV and non-NTV modulations instead of using two separate complex algorithms which result in increased computational burden. A non-NTV method called selected three-vector (STV) modulation is chosen to perform the detailed analysis of above proposed algorithm for hybrid NTV-STV modulation. Additionally, a simplified STV (SSTV) is derived to develop a new hybrid NTV-SSTV modulation strategy which further reduces losses and complexity compared with the hybrid NTV-STV modulation, without affecting the performance of NPC. The proposed algorithm and the derived hybrid modulation strategy are validated using simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this study, an artificial neural-network (ANN)-based space-vector pulse-width modulation (SVPWM) for capacitor voltage balancing of a three-phase three-level neutral-point clamped converter with improved power quality is presented. The neural-network-based controller offers the advantage of very fast implementation of the SVPWM algorithm. This makes it possible to use an application specific integrated circuit chip in place of a digital signal processor. The proposed scheme employs single layer feed-forward neural-networks at different stages along with a control algorithm using modified reference vector for capacitor voltage balancing of an improved power quality three-phase neutral-point clamped converter. In other words, the neural-network receives three-phase voltages and currents as input and generates symmetrical pulse-width modulation waves for three phases of the converter. A simulated digital signal processor (DSP)-based modulator generates the data which are used to train the network by a back-propagation algorithm in the MATLAB Neural Network Toolbox. The simulation of converter with ANN-based space-vector modulator shows excellent performance when compared with that of conventional DSP-based modulator. [ABSTRACT FROM AUTHOR]

Level-shifted pulse-width modulation (LSPWM) technique for single-star bridge cells (SSBCs)-based modular multilevel cascade inverter (MMCI) produces better harmonic performance than the phase-shifted PWM (PSPWM) technique but its applications are limited because of the unequal device conduction periods, which is undesired in high-power applications. To evenly distribute the switching and conduction losses, the switching patterns should be rotated among the H-bridge cells. This study evaluates two possible carrier rotation techniques, which combines the advantages of uniform power distribution among H-bridge cells and equal device conduction periods from PSPWM technique and improved harmonic performance from LSPWM technique. The effectiveness of the two adopted techniques has been established through simulation and experimental studies. To verify the equality in devices conduction periods, algorithms have been proposed. Further, the behaviours of the DC capacitor voltages of individual H-bridges cells of a five-level SSBC-MMCI-based active power filter have been studied with the adopted carrier rotation techniques. [ABSTRACT FROM AUTHOR]

In this study, a modulation strategy is presented using minimum number of switching transitions of optimised switching sequences for balancing of DC-bus capacitor voltages of a three-phase neutral-point clamped bi-directional converter. This new approach is derived from the fact that in front end AC-DC converters, the location of supply voltage vector and reference current vector (magnitude and lag angle) vary depending upon the amount of reactive power compensation and the load current to be supplied by converter. Accordingly, the effect of small and medium vectors (using space vector pulse-width modulation) for same switching state varies in each sector and its regions resulting in DC-bus capacitor voltage unbalancing. This observation along with the detailed analysis of current pattern for both the capacitors within each sector and its regions and its effect on neutral-point voltage deviation forms the basis of proposed approach of maintaining optimised space vector sequences and changing the number of sampling periods within each sector and its regions, thus resulting in DC-bus capacitor voltage balancing. As a result, modified reference current vector spends different amount of time in alternate sectors (moves faster and slower in alternate sectors) but total time for one complete cycle is same as actual current vector. The converter exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum switching losses, reduced ripple factor of the regulated DC output voltage and particularly, the neutral-point voltage deviation under dynamic load conditions both for rectification and inversion modes of operation. [ABSTRACT FROM AUTHOR]