This study presents a reduced switch three-phase three-level H-Bridge-based shunt active power filter (SAPF) for the mitigation of current harmonics, the reduction of current unbalance and the injection of reactive power. This recommended SAPF is developed by using two H-bridge and two DC-link capacitors. Compared to the conventional three-level H Bridge-based SAPF, the eight-switch cascaded H bridge (ES-CHB)-based topology saves four semiconductor switches and one DC-link capacitor. The ES-CHB-based SAPF saves the power electronic components and reduces voltage stress across each switch by introducing a small AC capacitor in series with coupling inductor in each phase. This LC circuit also reduces the harmonic stress of SAPF by tuning at the sixth order of current harmonics. The only drawback of the suggested SAPF is the DC link voltage unbalances. To address this problem, a modified feedback control strategy is proposed in this study. The modified controller regulates the DC link voltage at the desired voltage and mitigates the DC link voltage unbalances, by using reactive power flow control and active power flow control, respectively. The performance of the suggested eight-switch three-level CHB-based SAPF is evaluated through MATLAB simulation and experimentally verified through the hardware implementation.

The mutual inductance between the primary and secondary coils is an important parameter in the wireless power transfer system, and the mutual inductance calculation of coils in many complicated circumstances has been studied. However, the mutual inductance calculation of two circular coils in arbitrary relative position with magnetic tiles have not been solved. In this study, an analytical formula of the mutual inductance with respect to the parameters of the system such as arbitrary relative position, geometry, and the properties of the magnetic tiles is proposed. The proposed formula is derived from the proposed parameter vector method, and the proposed parameter vector method can not only be used to explore the tendencies of the mutual inductance in arbitrary relative position, but also provide a fairly concise and general method for mutual inductance calculation. The finite-element analysis and experimental results validated the reliability and accuracy of the proposed formula, and an accuracy of a few parts in a thousand can be readily attainable.

A conventional pulse frequency modulation (PFM) controlled LLC resonant converter requires a wide switching frequency operating range to regulate the output voltage. There are some disadvantages of PFM LLC resonant converters: (i) the design and optimisation of magnetic components and gate driver circuitry are challenging; (ii) due to the variable switching frequency operating range, electro-magnetic interference performance of the converter is degraded; (iii) efficiency degradation; (iv) inability to achieve independent control in multiple-output applications. To address the above-mentioned problems and achieve fixed switching frequency operation, a variable magnetising inductance control (VMIC) strategy is proposed. In the proposed VMIC control strategy, the operating switching frequency of the primary switch is fixed and the duty cycle remains constant at 0.5. At the resonant frequency operating point, the output voltage is independent of both the magnetising inductance and load. In addition, the zero current turn-off operation of the secondary rectifier requires that the switching frequency be designed below the resonant frequency. The operational principles and design considerations of the LLC resonant converter with VMIC are presented. Experimental results from a 200 W prototype are presented to validate the theoretical analysis and the effectiveness of the proposed VMIC control strategy.

A zero voltage switching (ZVS) interleaved high step-up converter with coupled inductor and built-in transformer voltage multiplier cell is introduced in this study. A more flexible design is provided by increasing the voltage conversion ratio by utilising the turns ratios of the coupled inductor and built-in transformer. The ZVS operation of the metal-oxide-semiconductor field-effect transistors (MOSFETs) and absorption of the leakage current are realised through active clamp circuits. Furthermore, the voltage stress across the switching devices is minimised that give rises to implementation of low voltage rated MOSFETs and consequently low conduction losses. Meanwhile, the diode reverse current problem is alleviated by the leakage inductance of the coupled inductor and built-in transformer. All of the abovementioned advantages make the proposed converter as a high efficiency candidate for high current and high step-up applications. Finally, a 600 W, 48–700 V voltage conversion with the conversion efficiency of 97% is fabricated to probe the merits of the proposed converter.

This study presents the full-bridge dc–dc converter (FBDC) operated with customised pulse width modulation (cPWM) for electric vehicle (EV) battery charging. The proposed cPWM retains all the benefits of the popular conventional phase shifted modulation (PSM) with minimal modification in the pulse width while further achieving the zero voltage switching for the active switches of the converter. The cPWM gating technique results in minimal circulating loss and switch conduction loss in comparison to PSM gating technique and higher efficiency. The detailed operation of the converter is presented with analysis. The theoretical waveforms of the converter and power loss analysis are discussed. A 540 W, 80 kHz experimental prototype is developed to validate the theoretical analysis. Finally, the comparison between PSM and cPWM is presented.

In order to construct the voltage-sourced converter high-voltage direct current grids, the high capacity direct current circuit breakers (DCCBs) are in demand. The hybrid DCCB has been the mainstream proposal, where the high-voltage solid-state switch (HVSS) is the key component for breaking the final fault current. Investigating the current commutation between the breaking branch and energy-absorbing branch, a hybrid DCCB with repositioned current commutation module (CCM) and redesigned HVSS is proposed in this study. By analysing the equivalent circuit of the CCM and HVSS, the detailed transient stages during current interruption procedure have been revealed, and the comparisons of different topologies for HVSS are made in-depth. The repositioned CCM can greatly decrease the transient voltage stress for HVSS and CCM whilst the improved HVSS including metal oxide varistor can maintain better interruption performances. Then the actual prototypes are developed to verify the effectiveness of the improved hybrid DCCB topology. In the end, a 500 kV DCCB is realised based on the proposed HVSS, which can ensure the reliability and convenience of the hybrid DCCB.

A three-phase pulse-width modulation (PWM) rectifier can usually maintain operation when open-circuit faults occur in insulated-gate bipolar transistors (IGBTs), which will lead the system to be unstable and unsafe. Aiming at this problem, based on random forests with transient synthetic features, a data-driven online fault diagnosis method is proposed to locate the open-circuit faults of IGBTs timely and effectively in this study. Firstly, by analysing the open-circuit fault features of IGBTs in the three-phase PWM rectifier, it is found that the occurrence of the fault features is related to the fault location and time, and the fault features do not always appear immediately with the occurrence of the fault. Secondly, different data-driven fault diagnosis methods are compared and evaluated, the performance of random forests algorithm is better than that of support vector machine or artificial neural networks. Meanwhile, the accuracy of fault diagnosis classifier trained by transient synthetic features is higher than that trained by original features. Also, the random forests fault diagnosis classifier trained by multiplicative features is the best with fault diagnosis accuracy can reach 98.32%. Finally, the online fault diagnosis experiments are carried out and the results demonstrate the effectiveness of the proposed method, which can accurately locate the open-circuit faults in IGBTs while ensuring system safety.

Model predictive power control (MPPC) is considered as a promising algorithm utilised in grid-connected inverter due to its fast dynamic response, simple control structure and multi-objective optimisation. However, under unbalanced network, the grid current with excessive distortion troubles the application of MPPC. Based on the conventional MPPC, this study proposes a model predictive flexible power control (MPFPC) to reduce the current total harmonic distortion and achieve three flexible targets, including the cancellation of the active- and reactive-power oscillation and the negative-sequence grid current. In this algorithm, the power references are divided into two parts, which are used as reference values for the instantaneous active power control (IAPC) and the instantaneous reactive power control (IRPC), respectively. The three flexible targets are achieved by regulating the ratio of the two parts of power reference. Meanwhile, the grid current of MPFPC is the sum of IAPC and IRPC; therefore, the grid current distortion can be suppressed effectively. Simulation and experimental platform constructed by a three-level inverter are established to validate the effectiveness of MPFPC, and the results exhibit that the MPFPC meets the above expectations.

In this study, an advanced predictive control system is proposed which consists of two cascade predictive controllers; the first one minimises the power losses while the second one minimises the torque ripple. In the first controller, motor losses are formulated as a function of stator-flux linkage components. Then, the optimal stator-flux linkage vector which causes the minimum losses is found by adopting fast-iterative shrinkage thresholding algorithm (FISTA). The second controller is a predictive direct torque controller adopted to control the stator-flux linkage and torque directly. In this controller, torque ripple is formulated as a function of the stator-voltage vector. Then, the optimal voltage vector which causes the minimum torque ripple is found by adopting FISTA. In the second controller, deadbeat control of the stator-flux linkage is considered as a constraint in minimisation of torque ripple. To assess the effectiveness of the proposed control system, performance of the motor is assessed through various experimental tests, where the results confirm that the proposed control system minimises the power losses and torque ripple, simultaneously. The comparative assessment with the recent predictive controllers indicates that the proposed control system has higher efficiency as well as lower torque ripples in all operating points.

Although the control strategy regarding quasi-Z-source inverter (qZSI) has been widely studied, the dynamic response and steady-state accuracy of the system with a non-linear section should be further improved. Based on this, this study proposes an energy shaping control (ESC) method based on the port-controlled Hamiltonian (PCH) model for qZSIs. Firstly, based on the average state-space model, the PCH model of the qZSI system is first built, which is an indispensable preprocessing for the following controller design. Based on the proposed model, the ESC method combining the interconnect matrix with damping configuration is proposed to improve the dynamic response and steady-state accuracy, which is verified through comparing with several existing linear and non-linear control strategies in detail. Finally, simulation and experimental results verify the effectiveness of the proposed method.

This paper depicts a self-tuning adaptive control method along with a novel robust procedure to system identification which is applied to a single-phase full-bridge Inverter with LC filter by Pulse Width Modulation (PWM). Moreover, an LC filter is designed to decrease the disturbing harmonics produced by PWM which, the stability of the filter can be noted as an important issue. On the other hand, a dynamic change of the inverter can lead to instability issues in which the proposed approach can overcome this problem and perform with a great response. Due to the parametric uncertainty on a full-bridge inverter and other disturbing factors, a digital adaptive controller is proposed which is performed by minimum degree pole placement (MDPP) technique combined with Improved Exponential Regressive Least identification (IERLS) algorithm. To prevent the undesired influences of high variance noises and disturbance on the performance of the identification approach, a robust identification algorithm is introduced which is capable of keeping the parametric estimation process in a desired range. Additionally, to deal with the variations of supply DC voltage, a proportional-integral-derivative (PID) controller is designed. Finally, the experimental and simulation results are performed by Matlab-Simulink to show the validation of the work.

This study reveals the energy shaping port-controlled Hamiltonian passivity-based control (PCH-PBC) technique for an interleaved boost power factor correction (IBPFC) converter. First, the mathematical modelling of an IBPFC converter is developed under all possible operating modes. Then, the average state-space model of the system is established with the help of averaging state-space technique. Further, the PCH technique is applied for controller design and the stability analysis of the proposed system is carried out. A proportional-integral (PI) controller is integrated with the PCH-PBC controller to achieve minimum steady-state errors. Finally, a Simulink model of the proposed system is developed using the Simulink toolbox of MATLAB software and its performances are studied under several operating conditions and verified through experimentation. To assess the system performance in terms of efficiency and input current total harmonic distortion (THD), the comparative study is also carried out under different controllers. Based on the simulation outcomes, the proposed controller is compared with the benchmark PI controller, adaptive passivity-based controller in terms of different control parameters. The performances of the controller are also investigated against dynamic variations at the input voltage and the load. It is observed that the proposed PCH-PBC controller achieves robustness against the aforesaid variations.

In this study, a comparative evaluation of a family of isolated Ćuk DC/DC converter with step-up techniques is presented. The voltage gain techniques are the reduced redundant power processing and the voltage multiplier. In addition, a detailed comparative analysis of the converters is showed. This comparison comprises features, such as the principle of operation, voltage gain curves, voltage and current stresses, design methodology, and estimated losses. By these comparisons, the main features and constraints of the analysed converters are identified. Four 200 W prototypes were constructed and evaluated in the laboratory. The isolated Ćuk converter with voltage multiplier showed the best performance and a peak efficiency of 95.86%.

The design of the control system in an inverter-based microgrid (μGs) is a challenging problem due to the large number of parameters involved. Different optimisation methods based on obtaining an approximated mathematical model of the μG can be found in the literature. In these approaches, the non-linearities and uncertainties of the real system are typically not considered, which may result in a non-optimal tuning of the control parameters. In addition, in most applications, the problem has been simplified, assuming that all controllers have the same value for their control parameters. However, in this case, the behaviour of the system is sub-optimal since the particularities of each node of the μG are not taken into account. In this study, an experimental approach for tuning the control parameters of an inverter-based μG is introduced. The approach is based on the methodology of design of experiments and it considers different values for the control parameters of all controllers. In this study, this methodology is applied to the design of a droop-free control scheme; however, it can be easily extended to other control schemes. The validity of the proposal is verified through selected experimental results.

This study presents robust parametric methods for the detection and estimation of grid-connected issues such as islanding, harmonics, and interharmonics. The power system signals are time varying owing to the intermittent nature of renewable energy sources. IEEE and IEC consider signals as stationary, which are negated in a future scenario. Therefore, parametric methods need to be applied for the estimation of these signals. In this study, parametric methods such as estimation of signal parameters via rotational invariant technique (ESPRIT) and multiple signal classifier are implemented in a grid-connected quasi-Z-source inverter, for the mitigation of the aforementioned grid-connected issues. Additionally, a novel ESPRIT-aided support vector machine (ESPRIT-SVM) is proposed for harmonics estimation. A comparative study is also conducted on the different parametric methods using MATLAB/SIMULINK. The proposed method is verified for application in various scenarios such as power mismatch, load switching, and capacitor switching. The simulation results of the proposed ESPRIT-SVM are validated through real-time experiments.

In this study, a non-isolated high gain DC–DC converter is presented. The proposed converter yields a voltage conversion ratio value which is a cubic function of the voltage gain obtained from a boost converter. The proposed converter is synthesised by judiciously interfacing a two-phase interleaved boost converter with voltage-lift capacitor and a quadratic boost converter. Resultantly, the proposed converter yields a practical voltage gain of 21.11. Further, due to the use of interleaving technique, the input current is completely free from ripples. The proposed concept is validated by conducting experiments on 18/380 V, 160 W prototype converter. The experimental results clearly demonstrate that the proposed converter operates at a full-load efficiency of 95.6%. Further, by practically implementing a simple closed-loop control, the output voltage of the converter is quickly regulated against variations in input voltage and load current so as to provide the desired 380 V across the load terminals.

This work deals with the control law design and experimental verification of a grid-forming dispatchable distributed generation based on a back-to-back converter. The proposed system brings several improvements to the prime mover as well as to the microgrid voltage quality. The control strategy is based on an inner current and an outer voltage loop for both sides of the converter. The external loop of the back-to-back input side, which is connected to the generator, is responsible for regulating the DC voltage. On the other hand, in the output side, the voltage loop ensures a high-quality AC waveform to feed the loads. A comprehensive discussion regarding the current controller with harmonic mitigation is performed to justify the controller's choice. It is shown that a suitable current controller significantly improves the disturbance rejection. A feed-forward compensation based on the load current prediction without any additional sensor is proposed to improve the output voltage quality. Experimental results are used to validate the proposed control law and to show the improvements and benefits of the system.

In a photovoltaic array (PVA) tied grid system, PVA and the grid are connected at AC bus (ACB) to feed the power to the grid and the load connected locally at the ACB. The photovoltaic energy conversion system (PVECS) requires an improved dynamic controller to control the grid voltage harmonics under variable solar power and nonlinear unbalanced load conditions. The conventional filtering controllers are unable to remove the sub-harmonics and DC-offset in the input signal. Moreover, their attenuation for the dominant lower order harmonics is unsatisfactory for unbalanced loading conditions and highly nonlinear loads. A MMLSTOGI (mixed multi-level second and third order generalized integrator) based control is used in this work. It effectively mitigates the dominant lower-order harmonics and the DC-offset of load currents and extracts their in-phase and quadrature-phase fundamental components (FCs). The PVA is connected at ACB through interfacing voltage source converter (VSC). The DC-link voltage is ascertained by generating its reference value using an incremental conductance (InC) based maximum power point tracking. The PVA power is feed-forwarded in the control to enhance the dynamics of the system. The control is validated on a developed model in MATLAB SIMULINK background, and using a developed prototype.

The Cauer thermal network has made a realistic physical representation of thermal behaviour of a multi-chip module (MCM) theoretically possible. However, the traditional method assumes the heat conduction is critical, with an approximate one-dimensional heat conduction path for calculation and fixed heat spreading angle to make up for the compensation brought by the approximation. It will limit the accuracy and cause a significant error in estimating the junction temperature of MCM. In this study, the heat spreading angle in the area of two adjacent chips is studied by using a cross-section to change the problem to a two-dimensional heat transfer question. Based on the heat flow got from the results of calculation by using Fourier's law, an expression for heat spreading angle as a function of boundary conditions is given, which is capable of estimating the junction temperature by adjusting effective heat conduction area of an MCM whose thermal behaviour is seriously coupled among neighbour chips. The accuracy of the proposed method and expression is validated by both the finite-element method and experimental results and they both show a good agreement with the calculation.

A new non-isolated high-voltage gain single switch quadratic modified single-ended primary-inductor capacitor (SEPIC) DC–DC converter is proposed in this study. The proposed converter consists of a modified SEPIC converter along with a boosting module to obtain a high-voltage gain at a low-duty ratio. It has all advantages of the SEPIC converter such as continuous input current, which makes it applicable for renewable energy sources such as photovoltaic systems. The proposed converter is able to attain a higher voltage gain in comparison with similar previous transformer-less DC–DC converters. Also, unlike high-voltage transformer-based DC–DC converters, it does not suffer from leakage inductances. Also, the proposed converter presents low-voltage stress across the switch and output diode. The proposed converter is controlled through a single switch and there is no limitation for a range of duty ratios. The voltage gain analysis of the proposed converter is done in continuous conduction mode and discontinuous conduction mode, also comparative analysis is done with the existing topologies with similar features. The proposed converter is designed for 400 V DC microgrid applications. The theoretical analysis of the proposed converter is verified by the experimental investigation in the laboratory.

Conventional switching table-based direct power control (DPC) usually suffers from higher power ripples due to the heuristic nature of the switching table. This study presents a novel model predictive DPC (MPDPC) strategy for grid-connected three-level inverters. In the proposed MPDPC strategy, a new synchronous frame-based predictive model is first developed and the conjugate of the complex power is then chosen as the control variable to simplify the analysis. Based on the newly developed predictive model, new principles of the voltage vector selection are further derived with the strict analytical proof to match all the control requirements, including the active and reactive power control, neutral point potential balance control, as well as the avoidance of the high voltage jumps. Finally, experimental results are provided to support the theoretical study and confirm the effectiveness of the proposed MPDPC strategy, as well as to demonstrate better performance in both steady-state and dynamic responses over the conventional DPC.

To charge the battery of electric vehicles (EVs), inductive power transfer (IPT) system has been considered to be more appropriate than traditional plug-in system especially for its security and convenience. This study proposes a hybrid IPT system for EVs charging applications adopting one transmitter coil with series compensation and two receiver coils with series compensation and LCL compensation. With the help of the two receiver coils and proper parameters design, the proposed system can naturally obtain constant current (CC) and constant voltage (CV) outputs and the maximum output power can be naturally limited which can prevent the system from possible overload. Therefore, the reliability of the proposed system is increased. Since the mode switching process can be automatically realised according to the value of battery equivalent load without extra control strategy and circuit, the fixed-frequency control can be used. Therefore, not only zero phase angle condition, but also the soft switching can be achieved. The theoretical analysis is presented with the design process of the IPT coils and resonance parameters for required battery charging profile. The performance of the system is verified by a 3.3 kW experimental prototype. The experimental results coincide well with the theoretical analysis.

This study presents active switched passive network-based high-gain DC–DC converters. The active switched network is formulated using two inductors, one capacitor and two diodes. Hence, the network is named as a 2L–C–2D network. Using ten components, an asymmetric high-gain DC-DC converter is proposed. This converter achieves a gain of 29 at an 80% duty ratio. In the asymmetric converter structure by replacing the inductor by another 2L–C–2D network, the symmetric converter structure is proposed using 14 components. This converter structure achieves the gain of 49 at the same 80% duty ratio. Apart from increasing the voltage gain, the 2L–C–2D network helps to reduce the voltage and current stresses of the converter. The utilisation of two semiconductor switches in the proposed converter structures permits a fault ride-through capability even when any one of the switches fails. Operations of the converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are discussed, and the boundary condition between CCM and DCM is derived. To limit the effect of parasitic elements on the converter performance, SiC-based semiconductor devices are used in the 500 W hardware prototype. The maximum efficiency of 92.8% is achieved in the case of a symmetric converter.

This work proposes a cost effective with a compact power electronic interface for plug-in electric vehicles (PEVs), which has the ability to achieve the all modes of vehicle operation, including plug-in charging, propulsion (PR) and regenerative braking (RB) for on-board applications. The proposed converter for PEVs has minimum component count as well as step-up and step-down operation ability depending upon the system requirement. The capability of the proposed converter to work in both the modes allows wide range of battery parameters selection, efficient DC-link voltage regulation and offers more flexibility in RB. Moreover, a current sensing based (without voltage sensor) non-linear carrier control (NLCC) technique for power factor correction has also developed in this work. This control scheme improves the reliability and stability of system by reducing the feedback circuitry. A prototype of the proposed charging system is established and analysed to an authenticate the effectiveness of developed system under steady state and dynamic conditions.

This study presents a concept of modulation of a single-phase seven-level neutral point clamped (NPC) converter with natural DC-link voltage balance and symmetrical DC-link capacitors discharge. The method is analysed in a single-phase full-bridge inverter composed of four-level diode-clamped legs (4L-FBCLD) which utilises three capacitors in a DC-link. Under the classic pulse width modulation (PWM) technique, the discharge of DC-link capacitors is unequal in a converter operating with active power. The proposed modulation assures symmetrical discharge of the DC-link capacitors and is achieved in a two-stage design. In the first stage, the carrier-based phase disposition PWM technique with modified carriers is used. In the second stage, the pulses are directed to suitable switches with the use of a state-machine decoder. The switching patterns are different in each level of modulation and are used to trigger natural balancing in the converter on the first and third level of modulation. This study presents the concepts of switching patterns, PWM generation, as well as the simulation and results of the experiment. The latter demonstrates the operation and feasibility of the 4L-FBCLD, symmetrical DC-link capacitor discharge and natural balancing in the converter.

The active clamp flyback (ACF) converter utilising gallium nitride (GaN) devices with high-switching frequency and high efficiency is impressive in system miniaturisation for AC–DC adapters. Owing to poor reverse conduction of GaN devices, the improper dead time between two switches can cause large power consumption in high frequency. This study proposes a dynamic dead time optimisation technique for GaNs ideal zero-voltage switching (ZVS) to address the issue. It adjusts the clamp switch on time to avoid large reverse conduction voltage stress on the main switch in different loads conditions. In addition, a new control scheme for clamp switch is introduced for enhancing efficiency in light to medium load. These techniques are experimentally verified on a 45 W (20 V/2.25 A) prototype of an ACF converter with a field-programmable gate array. The controller enables the system to operate at 1 MHz and dynamically modulates the dead-time under universal input and full load. With the light load ZVS control scheme, the system can achieve a maximum efficiency of 94.12 and 80.23% in the worst case. The prototyped converter can achieve power density (exclude case and controller) of 18 W/in³.

Three-port isolated dc–dc converter, as an active exploration and trial of photovoltaic access to dc distribution system, has the advantages of superior control flexibility and high reliability. Due to the changes in the phase-shift (PS) angle, the conventional PS control method cause transient dc bias in inductor current and magnetisation current, further increasing the current stress of switches and threatening the safe operation of the converter. Based on superposition theorem analysis, this study discusses the formation mechanism of transient dc bias, constructs a mathematical model of drive signals, and proposes two typical combination strategies of drive signals. The proposed method can simultaneously suppress the dc bias of port inductor and transformer magnetisation inductor in one switching cycle by changing the duty ratio of square wave voltage or adding the zero-voltage phase related to the PS angle. By simulating the PS angle change and output power fluctuation, the dynamic characteristics under conventional PS control and the proposed strategy are compared and discussed. The simulation and experimental waveforms show that the proposed method is not only suitable for the multi-step step change of PS angle, but also sufficient for the continuous evolution of the PS angle.

This work introduces a novel non-isolated boost DC–DC converter with high-voltage gain and high efficiency. The magnetic coupling and voltage lift circuit technique has been utilised to enhance the voltage conversion ratio. In order to decrease the peak voltage across the active switch, the voltage lift circuit acts as a clamp circuit. The zero current switching in the OFF-state and the zero voltage switching in the ON-state of diodes are other advantages of the suggested converter which leads to approach high efficiency by decreasing the conduction losses. In addition, only one power metal–oxide–semiconductor field-effect transistor with lower ON-state resistance is employed, which can provide the simple control circuit of the proposed topology. For demonstrating the performance of the proposed structure, the principle of operation modes and comparison results with other previous works is carried out. Finally, experimental results with a 200 W power level at 25 kHz operating frequency are prepared, which validate the usefulness of the proposed converter.

This study presents a solar photovoltaic (PV)-battery-integrated multi-input converter (PBMIC) based two-stage off-grid system for catering household ac appliances in areas where the grid is not available. The proposed single-stage PBMIC facilitates the control of both PV array and the battery along with adequate voltage boosting by employing only two controlled switches. This reduces cost for semiconductor devices along with associated accessories and also reduces a number of power converter stages required for the overall system. Owing to the adequate voltage boosting capability, the proposed system facilitates the use of low-voltage levels for both PV and battery, thereby eliminating the problems associated with the series connection of multiple units of them. The topological configuration of the PBMIC under different modes of operation is analysed. Furthermore, a novel control scheme that allows the converter to operate in various modes necessary for an off-grid system along with a seamless transition between these modes is also devised. A 400 W prototype of the complete off-grid system formed by connecting a full-bridge dc–ac inverter at the output of PBMIC is fabricated for conducting experimental studies. The validity of the complete system is substantiated by comprehensive simulation and experimental performance.

Three-phase passive (or uncontrolled) rectifiers are typically placed at the front end of the overall power conditioning circuit for AC to DC conversion in low-cost, small-scale renewable-energy systems, e.g. residential purposes wind turbines. Whenever a diode in one leg or multiple legs becomes faulty, offering an open circuit to the flow of current in both directions, it severely affects the power quality at the grid-side and may lead to the permanent disconnection of the power contributing unit from the grid. Even under a normal voltage rectification mode, an unbalance fault on the generator side may cause similar behaviour. To address these issues, this study presents a novel spectral analysis based fault detection and diagnosis (FDD) method for unbalance and open-circuited faults in the 3-phase uncontrolled rectifier. The proposed FDD algorithm accurately identifies the fault location based on magnitude and phase angles of different harmonic components of the filtered rectified voltage and specifically devised thresholds. The effectiveness of the proposed FDD algorithm is demonstrated through exhaustive MATLAB simulations of the grid-connected power conditioning unit with variable 3-phase supply. Subsequently, the hardware implementation of the overall experiment is demonstrated under a fixed voltage, and a fixed frequency source fed 3-phase uncontrolled rectifier.

Parasitic capacitances in transformers consist of three main groups: winding-to-winding, layer-to-layer, and stray capacitances. Stray capacitance is also made of turn-to-turn and turn-to-core capacitances. This study presents a novel analytical method for calculating the values of turn-to-turn, turn-to-core, and stray capacitances in each winding, and employs the results to calculate the equivalent parasitic capacitance especially for high-voltage switching transformers. The proposed analytical method introduces an explicit formula in terms of the winding and core dimensions. This formula can be applied in performance analysis and design optimisation methods. By utilising the proposed formula, calculation of the equivalent parasitic capacitance neither takes a great deal of time nor requires a particular computer system. The analytical results are verified by simulation results using the finite-element method and experimental results achieved by a practical prototype of a high-voltage switching transformer employed in a 390 W, 15 kV inductor–capacitor–inductor–capacitor resonant converter.