This study presents a universal lighting driver for unknown connected light emitting diode (LED) arrays by using a single-ended primary inductor converter (SEPIC) DC/DC converter and a T–S fuzzy model-based current controller. Driving and lighting an LED array with unknown series and parallel connection is a significant research for universal adaptable applications. To this end, the input voltage of the LED array is up/down adjusted by the SEPIC DC/DC converter, whereas exact LED lighting current control is realised by the proposed T–S fuzzy parallel distributed integral compensation control method. For easier implementation, a linear-simplified fuzzy observer is introduced under output feedback. Asymptotic convergence is guaranteed by strict stability analysis and linear matrix inequality gain design. Moreover, the fuzzy lighting current controller does not require the electrical model and arrangement of the LED array. In addition, even if we take uncertainty, disturbance and rapidly changing reference current into consideration, the high robustness and transient response performance are still assured via robust gain design. Finally, the satisfactory performance is shown from experimental results.

In this study, an improved performance three-phase neutral-point clamped bidirectional rectifier with modified control scheme is proposed. The proposed control strategy takes into consideration the amount/degree of deviation of source voltage from desired rated value during supply perturbation and accordingly modifies the reference current template for each phase individually which is termed as compensated reference current. In other words, magnitude, shape and phase of compensated reference current waveform for each phase are different depending on amount of deviation of that phase. A complete mathematical model of rectifier using pulse width modulation technique is developed. The performance of the converter is evaluated in terms of near unity input power factor, low input current total harmonic distortion, reduced ripple factor of the regulated DC output voltage and particularly the neutral-point voltage balance under different load conditions both for rectification and inversion modes of operation. It is shown that the three-level AC to DC converter with the proposed control scheme displays better performance under source voltage perturbations such as voltage sag, swell, unbalance, harmonics, frequency variations as well as phase angle deviations which are regularly encountered in practical environment.

This study presents an interleaved high step-up DC–DC converter based on three-winding high-frequency coupled inductor and voltage multiplier cell (VMC) techniques. The primary and secondary windings of each coupled inductor are inserted in the same phase and the third winding is inserted in the other phase. The VMC in each phase consists of two diodes, two capacitors, the secondary winding of the same phase coupled inductor and the third winding of the other phase coupled inductor. The voltage gain is increased and the output voltage is clamped across the capacitors of the VMCs. Then, the voltage across the power metal oxide semiconductor field effect transistors (MOSFETs) is decreased. The leakage inductance of the coupled inductors controls the output diode falling rate, which alleviates reverse recovery problems. The power MOSFETs are turned-on under zero current switching that helps to conversion efficiency improvement. Three modes of operation named as continuous conduction mode, discontinuous conduction mode and boundary conduction mode are investigated for the proposed converter. The carried mathematical analysis and satisfying operation of the proposed converter are verified via experimental results of an 870 W 60 V-input to 590 V-output laboratory prototype with 95.2% conversion efficiency.

This study is devoted to study and propose a single-phase trans-Z-source-based AC–AC converter with unique features of traditional trans-Z-source converter such as inverted and non-inverted boost and inverted buck output voltage. Output and input operate with same-shared ground, which is very useful in protection. Every aspect of proposed converter is analysed and studied. To prevent current and voltage spikes that are some of the main problems of AC–AC converters, safe commutation is employed. To evaluate the performance of the converter, MATLAB/SIMULINK software is utilised. Moreover, a laboratory prototype of proposed converter is implemented to verify the converter analysis and simulation results.

The study provides improved modifications of the positive output super-lift Luo converter that allows significantly increase the voltage transfer gain by the modest means. In the simplest case this increase is provided by replacing the inductor by the switched-inductor structure consisting of two inductors and three diodes. This allows getting practically double increase in the line-to-output voltage ratio at the high values of duty cycle. Analysis of steady-state and transient conditions shows that the zeros of the transfer function for the converter, as well as for the conventional boost converter, are positive. The study indicates possible ways to further increase the output voltage ratio without additional switches – by the use of magnetically coupled inductors and diode-capacitor voltage multipliers. Simulation and experimental results confirm the theoretical analysis and the advantages of the proposed converters.

DC–DC converters with high-voltage gain and low-input current ripple have attracted much attention in photovoltaic, fuel cells and other renewable energy system applications. Conventional boost–flyback converter can achieve high-voltage set-up ratio; however, its input current is pulsing and the voltage stress across output diode of flyback-cell is high. In this study, by incorporating coupled-inductor into the boost-cell of boost–flyback converter, the voltage stress across the output diode is effectively reduced. Passive snubber circuit is utilised to suppress the voltage spike across power switch, low-voltage-rated metal–oxide semiconductor field effect transistor (MOSFET) with low R _{ds_on} can thus be used to reduce the conduction loss of power MOSFET. In addition, ripple-free input current can be achieved, which makes the design of electromagnetic interference filter easy. Steady-state characteristics of the proposed converter are analysed, and experimental results are given to verify the analysis results.

This study presents a new reference current estimation method using proposed robust extended complex Kalman filter (RECKF) together with model predictive current (MPC) control strategy in the development of a three-phase shunt active power filter (SAPF). A new exponential function embedded into the RECKF algorithm helps in the estimation of in phase fundamental component of voltage (v_h ) at the point of common coupling considering grid perturbations such as distorted voltage, measurement noise and phase angle jump and also for the estimation of fundamental amplitude of the load current (i_h ). The estimation of these two variables (v_h , i_h ) is used to generate reference signals for MPC. The proposed RECKF-MPC needs less number of voltage sensors and resolves the difficulty of gain tuning of proportional–integral (PI) controller. The proposed RECKF-MPC approach is implemented using MATLAB/SIMULINK and also Opal-RT was used to obtain the real-time results. The results obtained using the proposed RECKF together with different variants of Kalman filters (Kalman filter (KF), extended KF (EKF) and extended complex KF (ECKF)) and PI controller are analysed both in the steady state as well as transient state conditions. From the above experimentation, it was observed that the proposed RECKF-MPC control strategy outperforms over PI controller and other variants of Kalman filtering approaches in terms of reference tracking error, power factor distortion and percentage total harmonic distortion in the SAPF system.

This study presents a novel power factor correction (PFC) technique using a canonical switching cell (CSC) converter applicable to multi-output switched mode power supply (SMPS) used in personal computers (PCs). The CSC converter at the front end of this single-phase fed SMPS operates in discontinuous conduction mode that offers inherent PFC for wide range of varying input voltages. It is cascaded to an isolated half-bridge multi output dc–dc converter for obtaining multiple dc voltages that are stiffly regulated and isolated from each other as per the requirement of the PC. The proposed SMPS is designed, modelled and its performance is investigated under steady state and dynamic operating conditions for varying input voltages and loads. It is found that the proposed design is able to offer excellent power factor and low total harmonics distortion at the utility interface as shown in investigations carried on simulation and experimental studies. A comparison of conventional SMPS with proposed PFC-based SMPS vividly brings out the merits of the latter. Further, a comparison is made with other types of front end converters to investigate the relative merits and demerits of the CSC converter over other front end converters.

This study proposes a simple digital current control technique for single-phase grid-connected voltage source converters. Unlike conventional strategies, the proposed method does not require any proportional-integral or proportional-resonant controller, fictitious phase generation, reference frame transformation and decoupling network; thus, it has the advantages of simplicity and reduced computational efforts. The suggested digital technique only uses a simple proportional controller in its structure and can be directly implemented on available digital signal processors. A digital controller parameter design procedure is proposed which ensures stability and near-zero steady-state error under all circumstances. Simulation and experimental results confirm that the proposed technique provides a fast and accurate current tracking with minimum harmonic distortions.

In transfomerless photovoltaic (PV) grid-connected inverter application, to reduce leakage current and to increase efficiency, many inverter topologies have been proposed. The method for increasing efficiency and reducing leakage current is evaluated and analysed in the present study. The operation of transfomerless PV inverter topologies with high-performance such as full-bridge, H5, H6, HERIC and paralleled-buck topology is analysed to calculate switching losses, conduction losses and free-wheeling losses. Device total losses for inverter topology are calculated according to the switching frequency and the output power. Also, a novel high-frequency model of inverter topology is proposed using the leg voltage and high-frequency equivalent circuit. The relation between the parasitic capacitor voltage and its leakage current is explained using the proposed high-frequency model. Also, the magnitude of the high-frequency voltage in the parasitic capacitor is derived mathematically. Efficiency of the several inverter topology according to the output power is compared and the leakage current is analysed using a novel high-frequency model. Finally, the efficiency and leakage current analysis are verified by simulation tool and 3 kW prototype.

The cross regulation effect in multi-output DC/DC converters offers a reliable support for the grid integration of multilevel inverters by balancing the capacitor voltages. The capacitor voltage balancing by single input dual output boost converter is often realised by conventional three-level switching scheme. The three-level operation benefits lower inductor ripple current, but it limits the maximum possible compensation voltages. In this study, the entire operating modes of the boost converter is presented and all the possible cases which contribute to the voltage balancing are employed for balancing the capacitor voltages in a three-level neutral point clamped inverter. A proportional-integral controller based duty ratio control and pulse delay control are used for DC link voltage regulation and capacitor voltage balancing. Since the classical state-space averaging technique is not suitable for SIDO converters, inductor current ripple averaging technique is utilised for controller design. The circuit simulation is performed in Matlab/Simulink. The digital controller is realised using the Virtex-5FPGA in Labview/CompactRIO module. Both simulation and experimental results are presented to validate the controller performance.

This study proposes a robust and powerful finite control set-model predictive control (MPC) algorithm to control the load current with lower total harmonic distortion and efficient reference tracking. In this control, the cost functions are determined for all the possible switching states of the converter and a switching state is selected corresponding to the minimum cost function for actuating the converter in the next sampling time period. To justify the performance of the proposed MPC scheme, a comprehensive study with the carrier-based pulse-width modulation, hysteresis current control and proposed minimum cost function-based MPC of the three-phase load current has been verified in MATLAB Simulink as well as the validation with dSPACE RTI1104 experimentation. This study validates the robustness of the proposed minimum cost function-based MPC control with a RL-load and three-phase induction motor (IM) load. The simulation and experimental results justifies the proposed MPC algorithm with potential tracking of the RL-load current corresponding to the reference current with lower harmonic contents as well as tracking of predictive torque and flux compared to the nominal torque and reference flux of IM, respectively.

A novel direct torque control strategy is proposed for matrix converter (MC)-based permanent magnet synchronous motor drive systems, which can achieve smooth control of torque and flux with fixed switching frequency. Analytical expression of torque and flux corresponding to different MC voltage vectors are derived. Evaluation functions for torque and flux are established. A master-vector and a slave-vector are selected from a switching table, whose duty cycles are calculated by the evaluation functions. Experiments with a prototype are carried out. The results show that the proposed method can achieve smooth torque and flux performance and fast dynamic response.

In this study, a novel developed structure of a converter based on double flying capacitor multi-cell named progressive double flying capacitor multicell (PDFCM) is proposed. The main advantage of this proposed structure compared with DFCM converter is generation of more output voltage levels while having the same number of devices. This novel converter's structure is based on integration of two extended cells between the conventional cells in DFCM converter. PDFCM converter has various structural states which are named based on the number of units, consisting of two extended cells and one conventional cell. These structural states are changing by the increase of levels depending on the number of cells. Thus, the progressive increase of the number of produced levels of proposed converter is because of the increase in the number of the units. In fact, by appropriate selection of the proposed converter states, the number of levels in output voltage will be higher than those of conventional converters. This converter can be controlled either by open-loop, self-balancing or closed-loop methods. In addition, the switching method is based on space vector modulation. The simulation and experimental results confirm the validity and effectiveness of the presented converter.

In this study, a new high step-up current-fed zero voltage switching (ZVS) dual half-bridge DC–DC converter is proposed. The presented topology is composed of two paralleled boost half-bridge converters. In this converter, only two switches are efficiently utilised such that the adopted scheme has a simpler control circuit, lower losses and lower cost. It is very noteworthy that over the whole range of load and input voltage variations, the switches keep ZVS operation and the output diodes operate in zero current switching (ZCS) condition leading to high overall efficiency. Also, taking the advantage of voltage-doubler circuits, transformers with lower turn-ratio and diodes with lower reverse voltage can be used to build the desired high output voltage. Regarding the mentioned characteristics, the proposed converter can be well nominated for distributed generation systems. In-depth analysis, design and performance comparison of this new converter are illustrated; then for verification purpose, experimental results with an output voltage of 400 V and output current of 2.5 A are presented.