The supercapacitor-assisted low-dropout (SCALDO) regulator is a unique new design approach to develop high efficiency, high current and low noise DC–DC converters, where a supercapacitor (SC) is used in the series path of a low dropout (LDO) regulator to act as a lossless voltage dropper. In the published literature, there has been much discussion about the stability of an LDO regulator, where different approaches are applied to frequency compensate depending on the LDO architecture. Given the case that the SCALDO technique is a combination of an LDO regulator and an SC, this study presents an analysis and experimental validation of the stability, based on a 12–5 V SCALDO prototype, proving that the effect of the SC energy recovery method does not make the overall regulator carry a stability issue in general.

This study proposes a high performance multichannel sequential display light emitting diode (LED) driver with pulse width modulated dimming control. A synchronous integral control strategy is developed for achieving optimal transient performances for the channel voltages and ideal rectangular waveforms for the LED current, which will help to maintain high efficiency and extend the lifetime of the LEDs. By synchronous integral control, each channel has a corresponding integrator whose input and output are turned on and off synchronously with the LED string. The proposed driver topology and control strategy are supported by detailed analysis on stability and transient response during on-time interval of a channel by using the averaged state-space model. The effectiveness of the design method is demonstrated with simulation. A three-channel LED driver is constructed to experimentally validate the high efficiency and high performance of the proposed topology and control strategy with desired LED current waveform and nearly constant channel voltages.

A new low-cost energy-saving concept in the modern light-emitting diode (LED) illumination system is developed and implemented using an isolated single-ended primary inductance converter (SEPIC). The dimming scheme presented in this study is a single-step with negligible distortion in the AC mains current as compared to the traditional low-cost triode for alternating current (TRIAC) dimming system, which distorts the AC mains current wave-shape beyond sinusoidal nature due to the phase-cut techniques. This dimming concept is completely retrofitted, no additional arrangement is required to initiate the dimming as compared to a TRIAC dimmer or other controllers. The isolated SEPIC converter is modelled and analysed in detail using the state-space average technique. The stability of the designed converter and overall closed-loop control are verified using Bode-plot analysis. The full load converter efficiency is found around 93%, which is much higher than the conventional flyback topology-based LED driver. The concept presented in this study is tested with the help of a laboratory prototype with an LED load of 60 W.

In this study, the analysis and design of a coupled-inductor (CL)-based ultra-high step-up single-switch DC–DC converter are presented. With the aid of the CL and voltage multiplier cell, the suggested topology can obtain ultra-high-voltage gain without a large turn ratio and extreme duty cycle. A passive clamp circuit is utilised in the structure of the introduced converter for not only alleviating voltage spike on the main switch effectively but also recycle the leakage inductance energy. So low-voltage rating and low on-state resistance metal oxide semiconductor field-effect transistor is allowed to increase efficiency and lower the conduction losses. The input current ripple of the suggested topology is very low due to connecting an inductor to the suggested structure input section, which is very friendly and desirable to the photovoltaic and fuel cell applications. The suggested converter steady-state analysis, operation principle, theoretical efficiency analysis, and design procedure are described comprehensively in this study. Furthermore, the suggested converter superiority is illustrated over various alike recently introduced the most important DC–DC structures in the comparison study. Finally, a laboratory prototype is fabricated with a 225 W output power to confirm the theoretical analysis of the introduced converter.

The technique of single-source cascaded H-bridge multilevel inverter (MLI) has been reported in previous works. In this study, a self-balanced series/parallel switched-capacitor (SC) is introduced to further develop this type of MLIs to generate more output levels. Each cascaded H-bridge is fed by an SC unit. All components in each SC unit withstand the same voltage stress, but different SC units address different voltages. With this asymmetric feature, different H-bridges are responsible for providing levels with different voltage intervals so that the cascaded MLI can generate numerous levels with a single dc source and fewer components. Compared with the conventional asymmetrical cascaded MLIs, just a single dc source is required, capacitors’ voltages are balanced automatically, high boosting ability and more output levels are achieved with SC technique in the proposed MLIs. To synthesise the output voltage as close as possible to sinusoidal shape but with less switching loss, comparative analysis of nearest level control and equal area criterion is provided to modulate the proposed MLI with 13-level output. Experimental results demonstrate that the proposed MLI has high efficiency and low harmonics.

A novel topological family of multi-level inverters with flyback high frequency link is proposed in this study. The inverters can transfer high DC voltage into regulated sinusoidal voltage with low total harmonic distortion (THD). The circuit configuration consists of high DC input voltage, DC-link capacitors, novel multi-level conversion unit, high frequency flyback transformer, cyclo-converter, output filter capacitor and AC load. This topological family includes diode-clamp type full-wave mode, hybrid-clamp half-bridge mode, multi-end mode and improved multi-end mode. To achieve reliable multi-level inversion and overcome DC-link capacitor voltages unbalance, multi-carrier modulation and DC-link capacitor voltage balancing strategy are presented. In addition, steady principle and AC small-signal model are analysed. Simulation and experimental results are given to prove that the novel flyback high frequency isolated multi-level inverters have the following advantages such as the high frequency electrical isolation, the bi-directional power flow, the two-stage power conversion (DC-high frequency AC (HFAC) - low frequency AC (LFAC)), the lower voltage stress of power switches and the low THD of output voltage.

This study presents a set of four cascaded step-up DC–DC converter with the quasi-Z source (qZS). By associating the voltage step-up cells at the input that qZS converter, depending on the configuration, their gain can multiply different factors that each cell with the qZS converter voltage gain. In addition, voltage and current stresses on components change. To evaluate the proposed converters the following characteristics are observed: the principle of operation, the voltage gain of the converters, low voltage and comparative evaluation. In order to demonstrate the simplicity of operation of the proposed converters to higher-order topology, qZS with boost factor and super-lift cells is modelled and controlled. Finally, to validate the theoretical analyses, two prototypes of 200 W were implemented experimentally.

In wide voltage range applications, traditional LLC converters suffer from the following issues: (i) to cover a wide voltage gain operating range, the required switching frequency range is also large, which challenges the design and optimisation of magnetic components, gate driver circuitry, and electro-magnetic interference filter; (ii) a small magnetising inductance is preferred in wide voltage gain range application, which leads to the increase of circuit circulating current and corresponding conduction loss; (iii) passive elements are determined based on the minimum switching frequency, so bulky passive elements are required to satisfy the required operation range. To solve these problems, in this study, a full-bridge LLC (FBLLC) resonant converter with two operation modes, namely full-bridge operation and frequency doubler operation, is proposed for wide voltage gain range application. The FBLLC converter discussed in this study can be designed in half of the input voltage range when compared with the conventional method, so smaller switching frequency operating range and higher efficiency operation are guaranteed. In addition, the smooth mode transition is achieved by introducing switching frequency feedforward control and small output voltage overshoot or undershoot is observed. A 150 W experimental prototype was built to validate the theoretical analysis.

The most common two challenges in high-voltage direct current (HVDC) multi-terminal transmission are the DC fault isolation and the DC voltage stepping up/down. Additionally, interconnecting voltage source converter (VSC)- and line commutated converter (LCC)-based HVDC network topologies has been challenging. This study introduces a new DC–DC converter topology concept connecting both LCC- and VSC-based HVDC networks with bidirectional power flow without operation stoppage. The proposed topology is formed of two front-to-front connected bridges with an AC-link formed of a capacitor and an inductor (which can be replaced by a transformer for voltage step-up/step-down). The LCC-HVDC network bridge is formed of insulated gate commutated thyristors while the VSC-HVDC network bridge is formed of insulated gate bipolar transistors. Therefore, ON/OFF switching of both bridges and bi-directional power flow are possible. Moreover, the reactive power transfer is nullified at rated active power exchange between the proposed converter bridges. The proposed concept's detailed analysis and control equations are introduced. Different operation scenarios are simulated in addition to scaled-down experimentation to test the applicability of power transfer scenarios without operation stoppage in normal operation.

This study proposes a diagnosis method for open-circuit faults of six-phase permanent magnet synchronous motor. When the open-circuit fault occurs in the single-bridge arm or the double-bridge arm, wavelet transform extracts the trigger signal of fault, and the z ₁–z ₂ plane current component is analysed. Seven kinds of fault modes are defined by analysing the characteristics of the scatter plot of the z ₁–z ₂ plane current component. The fractal dimension of the z ₁–z ₂ plane current component scatter plot is calculated to accurately quantify the fault modes. Moreover, 13 fault areas are defined by analysing the current centroid position of the z ₁–z ₂ plane current component. First, the diagnosis of two particular kinds of fault modes is completed by selecting the fault area. Besides, the diagnosis of the remaining five kinds of fault modes is completed by combining the fault area and the fault mode. The conditions for judging all open-circuit faults are summarised to establish a fault database. All the open faults can be diagnosed by searching the fault database by the proposed method. Finally, the effectiveness of the method is verified by experiments.

A novel snapback-free and low-loss shorted-anode lateral insulated bipolar transistor (SA-LIGBT) based on silicon on insulator with self-driving auxiliary gate (SAG) in the anode is proposed, named as SAG-LIGBT. The SAG is characterised by metal oxide semiconductor (MOS) structure in the anode, and the gate of the MOS is shorted with the anode electrode, thus self-driving without extra gate signal is achieved. At anode voltage V _A = 0, the P-base serving as a barrier to hinder electrons flowing into the N + anode. At V _A = V _on of the forward conduction, the P-base is depleted to intrinsic, and the anode resistance R _SA is increased from R _P-base to R _intrinsic. At V _A = V _bus of the turn-off state, the P-base is fully depleted and an electron accumulation layer is formed under the SiO₂, thus the R _SA is decreased from R _intrinsic to R _n-channel to provide a low-resistance path for electron current. Consequently, the device not only eliminates the snapback effect but also reduces the turn-off energy loss E _off. Therefore, a better trade-off is obtained between V _on and E _off. At the same V _on, the E _off of SAG-LIGBT is decreased by 57 and 66% compared with separated shorted-anode LIGBT (SSA-LIGBT) and SA-LIGBT, respectively. Moreover, the SAG-LIGBT exhibits the shorter T _off of 80 ns than the SSA-LIGBT and vertical P-collector and N-buffer LIGBT at J _A = 100 A/cm².

This study proposed a dual-output AC–DC converter based on three-port bridgeless power factor corrector (TPB-PFC) and a non-isolated resonant DC-transformer (Ni-DCX) for dual-output DC voltage applications. A constant DC output voltage and a variable DC output voltage are provided simultaneously by the proposed AC–DC converter. Based on the TPB-PFC converter, a stacked power conversion structure with reduced power conversion stage is presented. Therefore, lower power losses and higher efficiencies are achieved. Meanwhile, soft switching of all the power devices in the Ni-DCX is achieved with open-loop controlled and optimised operation of the Ni-DCX, resulting in easy control and higher efficiency. In addition, switching losses of the TPB-PFC are reduced thanks to the three-level characteristic. Operation principles and characteristics of both TPB-PFC and Ni-DCX converter, and modulation and control strategies of the proposed AC–DC converter are analysed in detail. Feasibility and effectiveness of the proposed solutions are verified experimentally with a 2 kW dual-output AC–DC prototype.

This study proposes a new approach for the detection of broken rotor bar (BRB) fault in three phase induction motor drive using Hilbert transform (HT) and artificial neural networks (ANNs), where the machine is controlled by direct torque control (DTC). HT is preferred to develop the stator current envelope. The sideband frequency and its amplitude of the samples are the input for the ANN. By using fast Fourier transform, the amplitude and frequency components are extracted and the severity of fault is determined by comparing the magnitude of an average of sideband frequency with the fundamental frequency. High accuracy identification of fault is found by ANN, where the results are trained and tested to a minimum mean square error that will detect the number of BRB in the induction motor. DTC is adopted for a suitable control technique in the industrial drives system to maintain good performance in torque control. The performance of the proposed method is verified by using MATLAB/SIMULINK and experimental tests.

This study presents a high boost DC–DC converter, integrates voltage multiplier cell, voltage lift capacitor, and coupled-inductor techniques to achieve a high-voltage gain. The proposed topology has the capability of extension without utilising any additional winding for a very large voltage conversion ratio. With utilising a passive clamp circuit and without requiring higher duty cycle values, the suggested converter obtains a large conversion ratio, low conduction losses, and reduced voltage stress of semiconductors with a steady value for the whole range of duty cycle. The converter operation principle is discussed and its steady-state operation is analysed in detail. Also, theoretic efficiency calculation and design guidelines of the topology are explained. Then, the proposed DC–DC converter is compared with similar configurations to indicate its advantages. Eventually, the validity of theoretic analysis is verified using experimental measurement results of the implemented prototype with a power rating of 226 W.

In recent decades, switched reluctance motors (SRMs) have been attracting increasing attention as a promising type of traction motors for electric vehicle propulsion, owing to their robust construction, elimination of permanent magnets. However, their phase inductance profile contains significant high-order harmonics, which generates input-current and torque ripples under SRM drive with the conventional square phase-current waveform. This study solves this problem by proposing a novel phase-current waveform in replacement of this square waveform. The proposed waveform is a predetermined waveform that can be stored as a look-up table in the inverter controller and can be magnified or attenuated to adjust the output torque, similarly as the conventional square waveform. Certainly, SRMs generally exhibit magnetic non-linearity due to magnetic saturation, which complicates the analysis. Therefore, the proposed waveform is analytically derived under the assumption that the magnetisation of the motor remains below the saturation level because vehicle propulsion tends to require a torque output far smaller than the maximum rating of the motor in normal vehicle travel. The proposed phase-current waveform is experimentally tested in comparison with the conventional square phase-current waveform. Consequently, the proposed waveform revealed smaller ripples in both the input-current and torque, supporting the effectiveness of the proposed phase-current waveform.

This study provides a detailed analysis of a dc to ac conversion unit as a building block of a modular multilevel converter for grid integration of photovoltaic (PV) systems. Each conversion unit contains a PV-linked multi-active-bridge (MAB) dc–dc converter followed by a grid-connected single-phase cascaded inverter. Using MAB topology can reduce the size and cost of the entire system as more conversion cells are connected to the same transformer. To integrate the PV outputs and maintain the maximum power point tracking (MPPT), different conversion cell topologies are feasible for the MAB converter. This study provides a comparison between the feasible topologies of the conversion cells in terms of the conversion efficiency, reliability, power transfer ability, cost, size, control complexity and generated ripple. The steady-state operation and the control technique of the selected topology are presented in detail. Some control techniques are introduced to improve the system's efficiency and MPPT performance of the conversion cell. A prototype of the conversion cell is developed to validate the proposed topology and the control techniques.

The stand-alone solar photovoltaic water pumping system (SPVWPS) remains idle for a significant period of time, when irrigation is not required and when sun is not available. Due to this large idle period, the effective utilisation of SPVWPS assets, i.e. solar photovoltaic array, power electronics converter, and motor, is poor. This study presents an approach to increase the effective utilisation of SPVWPS under the aforementioned idle period. It is proposed to interface the grid with SPVWPS without adding extra power electronic interface. An innovative integrated photovoltaic inverter is constructed using existing SPVWPS components. The inverter enables the transfer of active power and exchange of reactive power with the grid during an idle period of SPVWPS. The three legs of the voltage source inverter (VSI) are interleaved with motor windings. The VSI switches are controlled with synchronous pulse width modulation to force a cophasal current in the motor windings. This accompanies a net motor torque to zero under grid-interactive operation. Hence, the three-phase VSI operates as a single-phase grid synchronise converter, and the motor windings are used as filter inductance. The control system is presented to establish grid-interactive functionality. A prototype is developed to verify system performance. The control system is implemented using the ARM Cortex-M4 microcontroller.

Reliability is one of the significant worries of multilevel inverter (MLI) owing to the higher number of capacitors and switches. In this regard, fault-tolerant single-phase MLI topology with improved reliability is proposed in this work. Apart from the reduced device count, the proposed topology has fault-tolerant characteristics without any extra switches or legs. Moreover, the voltage of the capacitor is balanced under pre and post-fault operation without any external circuit. Less number of the turn-on devices and power losses promise higher reliability of the proposed topology in comparison with recently proposed topologies. The reliability of the proposed topology, as well as recently proposed topologies, has been evaluated. A detailed quantitative comparison of the proposed inverter topology has been carried out with the recent literature. The robustness and effectiveness of the proposed topology are carried out under various operating conditions in the SIMULINK environment. Finally, an experimental test bench of the proposed topology is built and the obtained experimental results validate the simulation results.

This study proposes a new method leading to a reduction in the current and torque ripple of an induction motor (IM) drive controlled by predictive torque control (PTC). The method lies within the optimisation of a DC-link voltage magnitude by the PTC cost function. Using a three-phase silicon-controlled rectifier, the DC-link voltage can be adjusted in such way that the current and torque ripple, caused mainly by treating the inverter as a source of only eight voltage vectors, is significantly reduced. The DC-link optimisation algorithm is integrated into the PTC that is used for the torque and flux control. In another prediction stage, the influence of the DC-link voltage on the torque and flux ripple is directly evaluated and then optimised by a second cost function. The theoretical analysis of the DC-link voltage influence on the drive behaviour is supported by simulation and experimental results conducted on a 5.5 kW IM drive, which confirm the benefits of the PTC with the DC-link voltage optimisation, especially if the drive operates in a region below the nominal speed.

A voltage-controlled canonical switching cell-derived DC–DC converter with improved power quality feeding a variable speed permanent magnet brushless direct current (PMBLDC) motor-drive system for home appliances, is presented in this study. The converter is operating in the continuous conduction mode (CCM). This converter has less stress on the converter devices due to CCM of operation. A single converter is used for both the power factor correction (PFC) and the speed control of the drive, thus reducing the number of elements in the system. The speed control, along with PFC in this system is achieved via a PI controller having speed reference as an input. This system is capable of providing the low speed to rated speed operation while maintaining a unity power factor. The Hall-effect sensor-based electronic commutation of a PMBLDC motor-drive is implemented at the fundamental frequency. This significantly improves efficiency by reducing the switching losses of the voltage source inverter. A prototype of it is developed in the laboratory for implementation of the scheme. Simulated and real-time experimental results of the scheme are presented here for performance validation at various dynamic and steady-state operating conditions.

This study presents the cascaded variable structure control approach with respect to the non-minimum phase nature of the DC–DC Z-source converter (ZSC). The method is based on the sliding mode control technique for output voltage regulation. The control-to-output transfer function of the ZSC contains a right-half-plane (RHP) zero in continuous conduction mode. The RHP zero, obtained by a linearised small-signal model, results in frequency response limitation. In this case, the converter output voltage control should be studied regarding to the RHP zero effect. To alleviate this effect and enhance the dynamic performance, the cascaded sliding mode control method is proposed. The cascaded sliding mode controller guarantees asymptotically minimum phase stability as well as robustness against input voltage variation and load resistance uncertainty. The capability and effectiveness of the proposed control method are supported by experimental results.

A metal-rim-connected inductive coupler with series-none compensation topology is proposed for smartwatch applications. By cross-connecting the receiving coil to the metal rim with a 1 mm slot, the direction of the induced current on the metal rim is transformed to be the same as the current flowing on the receiving coil, leading to a strong magnetic coupling between the transmitting coil and receiving coil. Considering the space limitation in the smartwatch, non-compensation components are needed inside the smartwatch and only a series capacitance is integrated on the transmitter side. A prototype of the proposed inductive coupler has been built and the wireless power transfer through metal rim has been validated via experiment. The experimental results show that the prototype achieves 5 W output power with 87.4% coil-to-coil efficiency.

The present work deals with the design of an efficient and inexpensive autonomous photovoltaic array-based water pumping system utilising a new configuration of a single-input balanced dual supply buck–boost DC–DC converter. A four-phase switched reluctance motor (SRM) drive is selected to pump the water effectively and to make the system reliable. The utilised DC–DC converter can provide two balanced outputs using a single solar power source. It offers continuous output supply with minimum ripple to the SRM pump. The new control logic is also discussed in this work to provide equal voltages for two capacitors of the split converter in both starting and steady-state conditions. An improved perturb and observer-based maximum power point tracking control is also utilised to enhance the solar output power at varying irradiance. Moreover, owing to the pulse-width modulation switching of a split converter, a reduction is achieved in the size of split DC-link capacitors. The MATLAB/Simulink-based simulation is done to validate the real-time implementation of a developed system. These obtained responses are again validated through test results obtained via the developed prototype.

DC–DC converters are important in medium-voltage direct current (MVDC) distribution networks. For the scenarios where energy flows unidirectionally from MVDC distribution networks to low-voltage direct current (LVDC) loads, the DC–DC converter, which composes of a modular multilevel converter (MMC) on the MVDC side, an uncontrolled rectifier on the LVDC side and a high-frequency transformer as the AC link, is the most cost-efficient candidate. In this study, a new modulation method with quasi-triangular AC-link current is presented to realise zero-voltage turning-on for all switches on the MVDC side, as well as zero-current-switching for the uncontrolled rectifier on the LVDC side. Besides, by adding simple and low-cost voltage-balancing D-L auxiliary circuits between adjacent submodules (SMs), all SM capacitor voltages can be well balanced without voltage sensors. The validity and effectiveness of the proposed method are verified by the simulation and experimental results.

In this study, a novel smooth least mean square (LMS) algorithm for controlling PV inverter has been proposed to estimate the reference current for synchronisation of solar photovoltaic (SPV) to the grid. The proposed control extracts both active and reactive fundamental components of the load current with improved convergence rate. These currents are compared with sensed grid currents to generate gating pulses for a voltage source converter. It also compensates the load harmonics, reduces voltage fluctuation at point of common coupling and supplies the reactive power demand of the local load. The algorithm has been tested under steady state and transient conditions for input variation as well as load variation under the power factor correction mode of operation. The algorithm has been developed in MATLAB/Simulink. Further, the efficacy of the proposed control algorithm has been tested on prototype hardware setup developed in the laboratory using dSPACE1104. The total harmonic distortion at the grid side, obtained from simulated and hardware results are well within the IEEE standards.

The main contribution of this study is to show the effect of light-emitting diode (LED) modelling in the design of offline drives. The authors propose the use of a source voltage and resistance model (SVRM), consisting of a threshold voltage source in series with the characteristic resistance, for the modelling of the LED. The offline drive used for the analysis is the flyback converter operating in discontinuous conduction mode. The equivalent circuit is analysed by superposition and the AC circuit is analysed with phasors. The analysis has proven that the flyback converter can be modelled as a current source feeding the output capacitor in parallel with the load. Likewise, the analysis demonstrated that the current ripple is always greater than the voltage ripple when an LED is used as a load. In order to validate the theoretical analysis, a design methodology for the flyback converter with the SVRM as a load was developed. The designed circuit was simulated in Spice and implemented in a prototype. Experimental results using an LED as load are compared with the same circuit using a simple resistance as load. The experimental results confirm the theoretical analysis with an error of <6.6%.

A single-switch high boost DC–DC converter is introduced in this work. In the suggested topology, a voltage multiplier cell and three-winding coupled inductor (CL) are integrated to obtain an ultra-large conversion ratio. Using a passive clamp circuit and also, no requirement of larger duty cycle values enable the converter to have a very high voltage gain, low conduction loss, and reduced voltage stress of semiconductors. Moreover, the leakage inductance of the CL alleviated diodes reverse recovery problem. Some important merits include ultra-high voltage gain, operating in low duty cycles, reduced voltage stress of semiconductors, continuous input current, high efficiency, and low turn ratio of the CL makes the introduced converter very suitable for renewable energy applications. Steady-state analysis and operation principles of the presented topology are expressed completely in the study. Moreover, the theoretical efficiency analysis and design guidelines of the suggested configuration are presented. Also, the superiority of the presented topology over the state-of-the-art similar DC–DC converters is demonstrated in the comparison study. Eventually, the validity of theoretical analysis is verified using experimental measurement results of the implemented prototype with a power rating of 240 W and an output voltage of 440 V.

This study proposes a new structure of hybrid cascade coupled-inductor high step-up (HCCIHSU) DC/DC converter for renewable energy sources. The proposed topology can provide an ultra-high voltage gain under continuous input current and low voltage stress on semiconductor devices. This converter is a hybrid cascade connection of the boost and buck–boost converters. The HCCIHSU utilises a coupled-inductor (CI) and a voltage multiplier (VM) cell to enhance the voltage gain ratio as a semi-quadratic function. The magnetic energy of the leakage inductor of the CI is recycled to the VM capacitors that reduce the component voltage stress and improve the converter voltage gain. Additionally, the voltage stress on the main power switch is clamped by two passive clamp capacitors. Due to the very high voltage conversion ratio at a reduced turn's ratio, the maximum voltage stresses on the switches and diodes are significantly alleviated, which further improve the efficiency. In this study, detailed steady-state analysis and comparisons with other related converters are provided. Finally, a 160 W/200 V laboratory prototype is built with 24 V input voltage at a switching frequency of 50 kHz to verify the performance of the proposed converter.

A conventional synchronous (rotating) reference frame control requires small-signal models and introduces cross-coupling terms. In this study, a virtual charge-based scheme for grid synchronisation with only current measurements has been proposed for a three-phase grid-connected inverter with a first-order filter. The methodology described in this study curbs the dependency of the inverter on the information of the grid voltage to generate unit vectors from the phase-locked loop. This kind of estimation is especially important during grid voltage sensor failures or a distant point common coupling or weak grid conditions. In the proposed estimation scheme, no noisy differentiation is involved and only the nominal values of the interfacing filter parameters are utilised, making the implementation easier in digital microcontrollers. Also, a current control architecture based on feedback linearisation concept has been explored and embedded with the proposed grid voltage estimation technique, and the corresponding performance has been evaluated via simulation and experimental studies.

This study proposes a new boost inverter based on a switched-capacitor concept with reduced switch count. The basic unit is a five-level topology, which inherently generates the AC output voltage with the self-voltage balancing of the capacitors. A conventional carrier-based sinusoidal modulation technique has been designed to maintain the capacitor voltage up to the input source voltage. The N-level structure of the proposed basic unit is also presented, which has the additional advantage of higher voltage gain with a single input. A detailed comparison with other similar topologies has been carried out. A laboratory prototype has been used to test the workability of the proposed basic unit and its extension for seven-level through several results.