High step-up DC–DC converters are increasingly required in many industrial applications. Conventional topologies operate at extreme duty cycle, high-semiconductor voltage stress, switching loss, and diode reverse recovery problems. This study presents a new non-isolated high gain, boost converter operating with a modest duty cycle by integrating a coupled inductor and switched capacitor technique. Importantly, the structure of the high-voltage side, together with the switched capacitor, reduces the voltage stress of the power switch to less than one third of the output voltage, which in turn helps to reduce the conduction loss by using a low on-resistance (R_ds-on) switch. The diode voltage stress is less than the output voltage which facilitates faster recovery. Furthermore, the converter employs a passive clamp circuit to recycle the leakage energy. The main switch achieves zero current switching (ZCS) turn-on performance and all diodes achieve (ZCS) turn off reducing reverse recovery related losses. As a result, the circuit exhibits high efficiency performance; which is essential for most modern power electronic applications. In this study, the operational principle and performance characteristics of the proposed converter is presented and validated experimentally with a 250 W, 20 V input voltage/190 V output voltage prototype circuit.

To extend the operating range of the snubber assisted zero-voltage and zero-current transition dual-interleaved boost converter beyond its inherent soft-switching limit of D = 0.5, a resonant pulse transformer is proposed instead of the resonant inductor. The 1 : 2 turns ratio of the transformer ensures full discharge of the snubber capacitor at all duty ratio values to facilitate zero-voltage zero-current switching at turn on of the main switching devices. The effectiveness of the topology has been confirmed by SPICE simulation and demonstrated by a 20 kW SiC metal–oxide–semiconductor field-effect transistor converter. The prototype operated at 20 kW, 112 kHz, 320–600 V achieving 98.7% efficiency and achieved 98.2% efficiency at 6 kW. Taking the additional losses in the auxiliary circuit into account, the switching losses at 20 kW are reduced by 74% compared with hard-switching operation, representing a 54% reduction in overall losses.

It is desirable to measure rotor quantities such as currents and temperatures in an electrical machine for design verification and condition monitoring purposes. A Bluetooth module which sends data from the rotor was previously reported in literature, but this module was battery powered, and therefore the duration of the tests was limited. This study presents a solution to this problem by developing a rotor-mounted power supply system which can harvest energy from the magnetic field inside the machine, by fixing an external loop to the rotor and making use of the induced voltage in the loop. A full-bridge rectifier, boost converter and battery charging module were developed to supply sufficient power to a bespoke Bluetooth transmission system and associated sensor circuitry.

Power converter reliability is critical for permanent magnet synchronous generator (PMSG) wind turbines. Converter failures are linked to power module thermal loading but studies often neglect turbine dynamics, control and the impact of wind speed sampling rate on lifetime estimation. This study addresses this using a 2 MW direct-drive PMSG wind turbine model with a two-level converter, and simulating junction temperatures (T _j) using a power module thermal equivalent circuit under various synthetic wind speed conditions. These synthetic wind conditions include constant and square wave profiles representing stable and gusty wind conditions. Responses to square wave wind speeds showed that the lower the gust frequency, the higher ΔT _j becomes, demonstrating that low turbulence sites have greater thermal variation in the converter. In contrast, wind speed variations with frequencies >0.25 Hz deliver only small increases in ΔT _j. It is concluded that reasonable approximations of T _j profiles can be made with 0.25 Hz wind speed data, but that lower data rate wind measurements miss essential, damaging characteristics.

Power system (grid) impedance is time varying due to the changing structure of the power system configuration and it can have a considerable influence on the control and stability of grid connected converters. This study presents an online grid impedance estimation method using the output switching current ripple of a space vector pulse-width modulator-based grid connected converter. The proposed impedance estimation method is derived from the discretised system model using two consecutive samples within a single switching period. The estimated impedance is used for islanding detection and online current controller parameter tuning. Theoretical analysis and MATLAB simulation results are presented to verify the proposed method and its effectiveness is validated using experimental testing.

In this study, battery model identification is performed to be applied in electric vehicle battery management systems. Two case studies are investigated: nickel-metal hydride (NiMH), which is a mature battery technology, and lithium-sulfur (Li-S), a promising next-generation technology. Equivalent circuit battery model parameterization is performed in both cases using the Prediction-Error Minimization algorithm applied to experimental data. Performance of the Li-S cell is also tested based on urban dynamometer driving schedule (UDDS). The identification results are then validated against the exact values of the battery parameters. The use of identified parameters for battery state-of-charge (SOC) estimation is also discussed. It is demonstrated that the set of parameters changes with a different battery chemistry. In the case of NiMH, the battery open circuit voltage (OCV) is adequate for SOC estimation whereas Li-S battery SOC estimation is more challenging due to its unique features such as flat OCV-SOC curve. An observability analysis shows that Li-S battery SOC is not fully observable and the existing methods might not be applicable for it. Finally, the effect of temperature on the identification results and the observability are discussed by repeating the UDDS test at 5, 10, 20, 30, 40 and 50 degree Celsius

This study presents a new current-limiting soft-starter for a three-phase induction motor drive system using pulse width modulation (PWM) AC chopper. A novel configuration of three-phase PWM AC chopper using only four insulated gate bipolar transistors (IGBTs) is also proposed. The proposed control strategy does not require zero crossing detection circuits, which employed in thyristorised soft starters. It requires only one current sensor. The duty ratio of the chopper IGBTs is obtained from the closed-loop current control in order to limit the motor starting current at a preset value. Only two complementary gate pulses are obtained from the control circuit to control the four IGBT switches. The proposed control strategy is characterised by a simple control loop; thus, a low-cost processor can be used due to the low-computation burden. The superiority of the proposed strategy is proved theoretically and confirmed experimentally. The experimental work is developed using a laboratory prototype system composed of DSP-DS1104 digital control board and 1.5 HP induction motor. The proposed starter offers a smooth start-up for the motor speed, torque ripple minimisation, less number of semiconductor switches, less switching and conduction losses, less harmonics and improved input power factor.

To analyse stability and non-linear behaviour of the sliding mode controlled non-isolated grid-connected inverter with H6-type (SMCNGCI-H6) system, the discrete model of the SMCNGCI-H6 system is first established based on the quasi-static theory and stroboscopic map method. With the case of folded diagram, a particular non-linear behaviour (state-mutation phenomenon) is observed that the state variable changes from the period-1 state to the period-2 state at a certain switching cycle. Then the root cause of state-mutation phenomenon is explored. Meanwhile, regarding the variation of state-mutation switching cycle with the parameters of sliding mode controller (SMC), a novel criterion (state-mutation switching cycle criterion) is proposed to determine state-mutation switching cycle of the state variable. Finally, the simulation and experimental results prove the validity of the discrete modelling of SMCNGCI-H6 system and the state-mutation switching cycle criterion.

Inverters, as one of the key components of electrical systems, have experienced a great evolution in the last decade, and their performance improvement is a challenge even today, leading to many researches on topologies and control schemes. This study introduces a new multilevel converter topology which is able to supply bidirectional current loads. The proposed structure has fewer power electronic devices such as power switches, driver circuits, power diodes, and DC voltage sources and, can be designed in both symmetric and asymmetric structures. In order to increase the number of output levels and the proposed basic unit development, modular expansion or cascading methods can be used. This study demonstrates that the aforementioned methods have the best results in asymmetric and symmetric structures of the proposed topology, respectively. The comparison between the proposed converter and some previous topologies shows that it has better conditions with respect to the used semiconductor count, switching and conduction losses, and total blocking voltage. The operation and performance of the proposed multi-level converter have been ascertained through simulations and verified experimentally for a single-phase symmetric thirty-one-level inverter which shows the proposed converter's ability in smooth sinusoidal output voltage generation with minimum total harmonic distortion.

An LCL-filter draws much attention in grid-connected applications, but the design faces challenges. The LCL and controller parameters are interdependent and inter-restricted as the grid current quality and control stability rely on the parameters of them both. In the past, researchers found that extra sensors or complex algorithms were required for the stability when the LCL parameters were designed independently. Consequently, the system cost and complexity were increased. Indeed, the LCL-filter with the delay-dependent single-loop current control can be stable if the LCL parameters are properly selected. Based on this thought, this study proposes to design the LCL parameters by considering their impact on the stability and dynamic of the inverter. Extra sensors or complex algorithms are no longer required. Based on establishing the model of the single-loop inverter-side current controlled inverter, the criteria of LCL design are obtained in order to improve the stability and the rejections of low-order and switching current harmonics. Based on those design criteria, a step-by-step procedure is proposed. Selected results have been provided to demonstrate the effectiveness of the proposed design.

In this study, a sliding mode-based controller is designed for regulating the output voltage of a high step-up DC–DC converter with three coupled inductors called Y-source impedance network. As Y-source converter can provide a very high boost at a lower shoot-through duty cycle of the switch and it has one more degree of freedom to achieve voltage boost. In order to accurately analyse the converter operation, the leakage inductance impact on diodes function in addition to other parasitic elements has been modelled. Hence, four different time intervals corresponding to switch and diode conduction have been considered. Also, an exposition of a variable structure control approach is mentioned. The method employs cascaded sliding-mode control (CSMC) to output voltage regulation of the converter. The stability and robustness of the CSMC against the variation of reference voltages and the uncertainties of the load demands have been explained. Simulation and experimental results confirm the capability and effectiveness of the proposed control method.

This study describes the design and implementation of an inverter control algorithm with both the inverter inner controllable impedance and governor-free characteristics. The inverter controlled as a voltage supply works with open-loop power control in grid-connected operation. It is realised that a pulse-width modulation inverter mimics the primary frequency and voltage modulation characterised similarly to a synchronous generator. On the basis of the proposed control algorithm, the inner controllable impedance and governor-free characteristics are analysed mathematically. Simultaneously, the authors analyse the output power characteristics of the proposed inverter and the level of the decoupled power control for designing the inner controllable impedance. When the inverter connects with the stiff grid, it will appear as the output current deviation problem. The generation mechanism of the dc component from the proposed inverter is clearly identified. The current deviation compensation control is analysed and implemented to solve it. Simulations and experimental results are given to verify the idea.

The analysis and design considerations of a soft-switching boost dc/dc converter have been presented. Operating principles of the converter have been completely presented, as well as the thorough analysis of the operating modes. In the analyses, all the equations related to the voltages and currents of the elements have been attained, and by using these equations the maximum values of them have been calculated. In the proposed structure, due to the resonant circuit, which consists of an inductor and two capacitors, the switches are turned on with zero voltage. In addition to the operating modes analysis, the values needed for the resonant elements have been calculated, and the design considerations have been presented in detail. One of the advantages of the proposed converter is the decrease in switching losses, besides the reduction of the voltage and current stresses of the circuit components, due to soft-switching feature. Another advantage of the proposed structure is its high switching frequency. In this literature, in order to evaluate the advantages and disadvantages of the proposed structure, there has been made a comparison with the conventional topologies. Moreover, the correctness of the presented analyses has been validated by experimental and simulation results, using PSCAD/EMTDC software.

This study presents a novel hybrid maximum power point tracking (HMPPT) controller capable of harvesting maximum power from solar panels in a remote power park which can be used for applications such as outdoor uninterruptible power supply, cellular phone and laptop chargers. The proposed HMPPT controller combines two MPPT methods, namely the linear open-circuit voltage method and variable step-size incremental conductance method and it has a simple and robust way of tracking MPP based on the relationship between the solar panel characteristics and load line. A 100 W photovoltaic (PV) generation system with soft switched interleaved flyback (SSIFB) converter is built to implement the proposed HMPPT algorithm. The soft switching of flyback converters in the proposed PV-SSIFB system is achieved by zero voltage switching–pulse width modulation technique. The steady-state performance under various constant irradiations and transient characteristics for rapidly varying irradiations and load changes are investigated. The effectiveness of the controller in the recommended circuit is verified by the simulation results and validated using a prototype model. Both simulation and experimental results show several advantages, namely accuracy, high tracking speed, minimum power loss and increased adaptability for a wide range of irradiations and load.

Nowadays, reduction in number of dc voltage sources alongside boosting property of the output voltage with reduced circuit components are counted as the most important topological features for the new structures of multilevel voltage source inverters. Considering the above, this study presents a new configuration of such converters which can produce a step-up 19-level waveform of the output voltage with a contribution of only two same (symmetric) values of dc voltage sources and 12 power switches. The proposed structure is composed of a switched-capacitor (SC) and a floating-capacitor-based (FCB) cell integrated into two isolated sub-units that have been series with each other as an hybridised platform. Herein, the relevant involved switches of the SC and FCB sub-units are modulated on the basis of an hybridised pulse width modulation technique which facilitates a significant degradation in the total power loss dissipation. An appropriate boosting feature with a self-charge balancing capability of all integrated capacitors, reasonable number of required semiconductor devices, higher efficiency and less complexity are other advantages of the proposed step-up 19-level inverter. To verify the precise performance of the proposed topology under different types of loading conditions, apart from the theoretical analysis, several simulation and experimental results will also be presented.