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Single-stage grid-connected PV inverters with a transformerless (TL) concept have been a hot spot research topic in both the academia and industry in the latest years. Dynamic voltage boosting feature through the adjustment of de duty cycle, reduced value of the current and voltage stress across the switches, common-ground (CG)-based circuit architecture and capability of larger number of output voltage levels generation can make these types of inverters an attractive option for an efficient and compact design. In this paper, a novel seven-level (7L)-CG-based TL inverter is proposed, which possesses all the above-mentioned features for a compact design. The working principle and modulation strategy are discussed. Some simulation results are presented to attest a proper performance of the converter.

Transfomerless grid-connected inverters with common-grounded circuit architectures and single-stage dy-namic voltage boosting gain are promising candidates for PV energy conversion applications. In this work, a new five-level (5L) variant of this category of inverters is introduced. Key features of the presented inverter are the reduced current stress profile, modularity, uniform peak voltage stress across the switches, higher power handling capability, and bi-directional power flow operation. The proposed topology is comprised of two input inductors, two capacitors, and ten power switches. Through a modular design with a phase-shifted SPWM technique, the injected grid current can be shared among the modules, while the size of the grid-interface filters can be reduced. The working principle of the converter is discussed, and some simulation and experimental results are presented to validate its feasibility.

Single-source inverters with integrated switched-boost (SB) module and single-stage energy power conversion architecture have become a popular solution in many power electronics applications. This paper presents a novel topology of such types of inverters, which offers a modular design with a dynamic voltage boosting feature over a wide range of input voltages. The basic configuration of the proposed topology is able to generate three output voltage levels. It is comprised of an integrated SB module and a Quasi-H-Bridge (QHB) cell. The QHB cell consists of a self-balanced floating capacitor and four power switches, and the SB cell consists of a boost inductor and a single power switch. A five-level boosted output voltage can be achieved through the differential connection of two identical QHB cells utilizing a single SB module. The circuit description of the proposed topology, a comparative study, and the simulation and measurement results are given to verify the feasibility of this proposal.

Dynamic voltage boosting feature in photovoltaic (PV) grid-integrated application is a necessity to achieve the maximum power point of PV arrays as well as boost the input voltage to the necessary dc-link voltage requirement. Such feature is usually achieved by incorporating a front-end boost or buck-boost dc-dc converter tendem with a conventional two or three-level inverter. However, such an integration cannot efficiently meet many IEEE strict grid codes from the power quality, ground leakage current, and the overall efficiency per power density aspects. The aim of this paper is to present a new five-level (5L) inverter with an integrated single-stage dynamic voltage-boosting concept and a common-grounded (CG) feature. As a result, the concern of ground leakage current is addressed through the provided CG feature, whilst both the power quality and overall efficiency of the system are improved with a 5L single-stage boosted output voltage waveform. To confirm the effectiveness of the proposal, apart from the circuit description, some experimental results are also presented.

Single-stage inverters with a common ac and de ground are emerging topologies which effectively eliminate the high-frequency common mode voltage. However, most of the existing common-ground-type inverters are based on switched-capacitor (SC) circuits which are inherently subjected to several important issues that lead to many practical limitations. Disadvantages such as high current spikes, high capacitor voltage ripples, and distorted ac output voltage with de offset are some significant challenges in these inverters. A new common-ground-type inverter that discard the use of SCs is therefore proposed in this paper. It consists of a single-inductor and an ac output capacitor that are controlled by 8 power switches. Sinusoidal ac voltage generation in both buck and boost modes can be achieved by controlling the inductor with a sinusoidal duty-cycle. Simulations are presented to verify the operation of the proposed topology.

This paper proposes a method to implement gain-scheduled adaptive PI control of wireless charging series-series resonant converter duty cycle control at fixed switching frequency operation. The method is applicable for both voltage mode battery charging control and current mode battery charging control. The gain scheduled PI controller look-up tables are established based on the optimized frequency domain control loop design in the entire equivalent load resistance variation range for the full battery charging cycle including both current mode charging operation and voltage mode charging operation for the voltage mode control. The same gain-scheduled PI control look-up tables are applied for the current mode battery charging control with additional loop gain applied for battery equivalent load resistance variation compensation. In both voltage mode and current mode control scheme, the DC input voltage magnitude variation and the non-linear gain of duty cycle command are both compensated so that the control system performance will not be affected by operation condition changes of DC input voltage and duty cycle level. The proposed gain scheduled PI control ensures that uniformed control loop bandwidth and satisfactory dynamic responses are achieved with sufficient stability margins in the wide range of equivalent load resistance change required for battery charging profile optimization.

This paper presents the rapid prototyping and validation of a Three-Phase Silicon Carbide (SiC) Voltage Source Inverter (VSI) in open-loop control and closed-loop control in TI C2000 microcontroller using PLECS coder real-time control tool. Comparative studies are also conducted to study the crucial factors that impacts the performance of the inverter. In open loop control, the experiment on the effect of using different PWM control strategies in terms of changing the modulation index was investigated. While in closed loop, the verification of the feedback of the PI control were studied to ensure that the output was able to maintain at the desired output level. The simulation results are compared with the hardware measurement results to validate the open and closed loop operations of the inverter. The 3-phase voltage source inverter rapid prototyping hardware platform developed is applicable for university lab teaching and advanced inverter control feature development.

This paper proposes the method to analyze the performance of wireless charging DC/DC resonant converters in various load conditions including the magnetic coupling effect. The equations for design performance analytical calculations are presented for series-series (SS) and series-parallel (SP) wireless charging DC/DC resonant converters. The equations can be applied in switching frequency sensitivity analysis at different magnetic strength and load resistance conditions to compare the performance of the resonant circuit topologies. The analytical calculation results can be used to size the voltage, current, and power rating of wireless charging resonant circuit components. The accuracy of the analytical calculation is validated by duty cycle control of wireless charging resonant converters in PLECS circuit simulation environment. Experimental results are obtained to support the conclusion drawn from the analytical solutions. The proposed method can be applied to study other wireless charging resonant converter topologies.

Switched-capacitor (SC) based inverter topologies are very attractive for renewable energy applications to step-up low dc voltage to higher ac voltage in single-stage without the need of front-end dc-dc converters, thus improving overall system efficiency, reliability and power density. This paper presents a new modular multilevel inverter based on switched-capacitor technique. Herein, series-parallel conversion technique is utilized to effectively self-balance the switched-capacitor voltages. Compared to other latest SC-based MLIs topology, the proposed structure features several advantages such as: low number of conducting semiconductor devices in load current paths and SC Charging paths. In addition, each capacitor is charged for at least half of the fundamental period that reduces voltage ripple and improves the inverter efficiency. Consequently, the presented inverter is suitable for high levels generation to achieve the rated ac voltage directly from a low voltage dc source. The merits and feasibility of the proposed inverter are verified through simulation for seven levels with sinusoidal PWM at different modulation indices and load conditions.

This paper presents the modelling and simulation of an 80kW AC microgrid network in MATLAB/Simulink environment. The network comprises a 50 kW photovoltaic system, a 10 kW fuel cell system, and a 20 kW battery energy storage system (BESS). The model is simulated under four operating conditions: (i) grid-connected mode, (ii) islanded mode (iii) islanded mode with excess power generation from Distributed Energy Resources (DERs) and (iv) islanded mode with limited power generation from DERs. Simulation results of the microgrid during various operating conditions were observed to investigate the charging and discharging characteristics of the battery and the total harmonic distortion of the power network during grid-connected mode and islanded modes.

In this paper, a novel 5-level inverter with common ac and dc ground is proposed for solar photovoltaic (PV) applications. The newly established common-ground-T-type (CGT-type) inverter is a single-stage topology restructured from the combination of a classical T-type inverter and a front-end three-level boost converter. Its distinctive topological structure can effectively eliminate the common mode voltage issue, prevent leakage currents, and ensure a continuous input current in PV systems. More importantly, it requires only two capacitors to realize an ac voltage which can be significantly boosted from a single dc source. A pulse width modulation (PWM) scheme is also established to undertake the following tasks simultaneously: charging of the boost inductor with a constant duty-cycle, and switching of two capacitors for 5-level ac voltage generation. The operation and feasibility of the proposed CGT-type inverter is analyzed and validated through simulation results.

The active neutral-point-clamped (ANPC) inverter is a popular multilevel inverter for various industry applications. In a recent attempt, an improved topology that integrates a flying capacitor to enhance the voltage gain from half to unity has been presented [11]. Retaining the benefit of unity-gain, this paper proposes a new ANPC topology with two improvements. Firstly, the voltage stress of the flying capacitor is reduced by half. Secondly, the charging of the flying capacitor at 0 level is made possible to achieve uniform charging over the power cycle. Comprehensive analysis is presented and experimental results of a prototype are presented for validation. Finally, the extension of the topology with increased number of output voltage levels generation is briefly discussed.

A new family of 7-Level Boost Active Neutral Point Clamped (7L-BANPC) circuits is proposed in this paper. The proposed topology is derived from the conventional ANPC by adding one additional capacitor to boost the voltage and increase the number of output voltage levels. The proposed topology generates seven output voltage levels using one dc source and two flying capacitors. A specific modulation strategy is presented in this study to provide self-balancing for the flying capacitors of the proposed inverter. Theoretical analysis and the operational modes of the proposed 7L-BANPC are presented in this paper. Highlights of the simulation of the proposed inverter are presented to validate the proposed topology. A scaled-down prototype has been built to validate the workability of the proposed topology.

This paper presents a new transformerless inverter topology which is termed as a single-stage common-ground boost inverter (S2CGBI) for single-phase solar photovoltaic (PV) systems. The proposed topology provides a common-ground for both the dc source and ac output to eliminate the leakage current induced by the parasitic capacitance of PV cells. Voltage-boosting is made possible with the incorporation of only one inductor, which renders the realization of single-stage power conversion. The proposed pulse width modulation (PWM) technique is capable of charging the inductor with a constant duty-cycle while guaranteeing ac output generation. The operation of the proposed S2CGBI is analyzed. Simulation and experimental results are provided to validate the effectiveness of the proposed topology and modulation scheme.

Double fed induction machine (DFIM) is preferred in various industrial applications, as it provides variable speed operation with reduced power converter rating and high dynamic stability. On rotor side, back-to-back voltage source converter (VSC) is act as excitation system and controls real and reactive power of the machine. Boost multi-level neutral point clamped (NPC) VSC is emerging in industrial applications due to the high dc link voltage utilization and less current THD. Full power converter redundancy in large rated VSC fed DFIM is challengeable and it is not yet employed in any practical applications such wind power generation and pumped-hydro power units. Therefore, fault-tolerant control (FTC) of VSC is mandatory for the continuous operation of unit by the project authorities of the units. This paper presents the fault tolerant and reconfiguration control approach for a boost NPC converter fed DFIM unit at open circuit faults in all controlled switches/devices. FTC during open-switch faults are investigated with the help of converter output voltage. Fault detection and isolation is achieved through the rotor currents and dc link voltage. A 2 MW DFIM is simulated in Matlab/Simulink environment to verify the operation of the proposed fault tolerant control.

DTC is known for its fast torque response, robustness against parameter variation and simple implementation. The performance of DTC drive, however, deteriorates at low speed due to its poor flux regulation. This paper proposes a technique to improve the flux regulation, and it only requires minor changes to the index of the look-up table. With this method, the simple structure of the DTC is retained and the same look-up table can be used. Experimental results are presented to show the effectiveness and viability of the proposed method. It is shown that flux regulation at low speed is improved and rated flux can be established even at zero speed; improvement in the flux regulation significantly improves the torque dynamic.

This work investigates a linear model predictive control (MPC) in conjunction with a voltage source inverter with a grid-interfacing passive filter. In an ideal grid, standard linear MPC demonstrates fast transient and excellent steady-state performance while respecting the imposed constraints. Nevertheless, its direct application onto the grid-connected converters operating with a distorted grid (e.g. islanded microgrid and marine vessel grid) or with applications that require harmonic current injection would encounter steady-state tracking error [1, 2], leading to unfulfilled application objectives. This shortfall is first demonstrated here using simulation, and then a solution based on plug-in repetitive control (RC) is proposed and investigated. With some assumptions simplifying this investigation, the resulted linear MPC with RC plug-in successfully mitigates the steady-state tracking errors while preserving the applicability of the multi-parametric quadratic-programming — the explicit implementation method that makes the linear MPC feasible in fast sampling applications. It is worth noting here that the notable features of MPC such as simple tuning, fast current response close to the physical limits of the system, and constraints consideration are retained and this makes the proposed control method a powerful alternative to the established grid-converter control techniques.

This paper presents a new technique to minimize the torque ripples inherited in DTC of induction motor. The typical discrete-based DTC imposes delay time which frequently allows the torque to overshoot beyond hysteresis bands. This triggers the selection of reverse voltage vectors which, in turn, cause large torque decrements. The torque ripples become of great significance at low speeds where torque overshoot is most likely to occur due to steep positive torque slope. A multi-level DC link voltage is proposed to vary the DC voltage of Voltage Source Inverter (VSI) according to motor's speed. By varying the DC link voltage, the torque slopes can be controlled and, hence, the torque overshoots can mostly be avoided. Therefore, the torque ripples are significantly minimized. The viability of proposed technique has been validated using MATLAB/Simulink software. Results show the proposed technique yielded over 50% reduction in the RMS torque ripples while maintaining a low switching frequency.

Renewable energy demand increases due to environmentally friendly. Power electronics development enhance the power quality produced. Standalone application multilevel inverter can help in improve rural area which is no electrified. For a multilevel inverter, the output required low total harmonics distortion and voltage boosting character. However, the conventional multilevel inverter are high distortion with high switching frequency. This paper is presenting multilevel inverter with selective harmonics elimination on reduce total harmonics distortion (THD) apply in standalone concept. 9-level cascaded H-bridge multilevel inverter is applied with optimize harmonics stepped waveform (OSHW) to compare performance with sinusoidal pulse width modulation (SPWM). In OSHW, selective harmonics elimination is used to reduce the low harmonics component which is 3rd, 5th and 7th harmonics. Genetic algorithm are applied to solve the non-linear equation on solving the best switching angle. The result show OHSW have lower THD then SPWM. Meanwhile OHSW eliminated low harmonics component by the aid of genetic algorithm which exist due to the low switching frequency.

The nine-switch converter topology with 2 three-phase ac terminals has recently been utilized in the literature for ac to ac power conversion. Nonetheless, the existing control techniques essentially involve complicated linear controller design with special modulation schemes. This paper presents a simple yet high performance controller based on finite control set model predictive control (FCS-MPC) for ac/dc/ac power conversion using nine-switch topology. FCS-MPC algorithm is designed to control two ac terminals independently by making use of 27 combinations of voltage vectors. The first ac terminal which features an active front end rectifier with unity power factor is connected to power grid, while the second ac terminal is used to control three-phase load. Achievement of multiple control objectives within the same converter topology is made feasible by the use of cost function in FCS-MPC algorithm. Simulation results are presented to verify the functionality of the system.

This paper presents a new control scheme that permits arbitrary power sharing between parallel inverters connected to a microgrid operating in island mode. The scheme processes the active and reactive output power information from all the inverters in a central controller that calculates the set-points for each inverter, based on the desired ratios of their output powers. This necessitates adjustment of the inverters' terminal voltages (phase and magnitude) relative to the voltage at the common ac bus. The power-sharing scheme is validated using MATLAB/Simulink simulation from three three-phase parallel inverters connected to a number of passive loads.

This paper presents a three-phase switched-battery multilevel (SBM) inverter for solar photovoltaic (PV) applications. The proposed inverter requires less number of power MOSFETs and gate drivers, and therefore, it is expected to be more compact and reliable than the conventional cascaded H-bridge multilevel (CHBM) inverter. For example, sixty units of power MOSFETs are required to construct a three-phase 11-level CHBM inverter, whilst a SBM inverter with the same number of levels needs only 27 units. The switching losses of the SBM inverter are expected to be lower than that in conventional PWM-controlled inverters because the power MOSFETs in the SBM inverter are switched at a much lower frequency. In addition, the proposed inverter has an integrated charge mode operation which is very suitable for solar PV applications. The performance of an 11-level SBM inverter has been evaluated using PSIM software and the simulation results confirm that the proposed inverter is capable of producing low total harmonic distortion (THD) AC voltages without the need of bulky filters.

This paper presents a new topology based on the series resonant converter (SRC) for high-voltage application. The proposed topology consists of two series resonant tanks. Each series resonant tank is built up by connecting a tank capacitor in series to a high-voltage transformer with the leakage inductance of the high-voltage transformer is absorbed as resonant inductor. Therefore, two high-voltage transformers are used in this topology with their primary windings are connected in series and secondary output are rectified and mixed before supply to load. The series resonant tanks are energized alternately by controlling two IGBT switches with pulse frequency modulation (PFM). This topology is operating in discontinuous conduction mode (DCM) with all IGBT switches are operating in zero current switching (ZCS) condition and hence no switching loss occurs. Moreover, this topology has low conduction loss as it requires only half number of IGBT switches compared to conventional full-bridge inverter based SRC. The effectiveness of the proposed topology is verified by simulation using OrCAD PSpice and the simulation results are presented.

This paper presents a novel topology based on the zero current switching series resonant (ZCS-SR) converter for high-voltage application. The proposed topology consists of two series resonant tanks. Each series resonant tank is built up by connecting a tank capacitor in series to a high-voltage transformer with the leakage inductance of the high-voltage transformer is absorbed as resonant inductor. Therefore, two high-voltage transformers are used in this topology with their primary windings are connected in series. The secondary output of both transformers are boosted by half-wave voltage multiplier and mixed before supply to load. The series resonant tanks are energized alternately by controlling two IGBT switches with pulse frequency modulation (PFM). This topology is operating in discontinuous conduction mode (DCM) with all IGBT switches are operating in zero current switching (ZCS) condition and hence no switching loss occurs. Moreover, this topology has low conduction loss as it requires only half number of IGBT switches compared to conventional full-bridge inverter based SRC. The effectiveness of the proposed topology is verified by simulation using OrCAD PSpice and the simulation results will be presented.

The conventional pulse frequency modulated (PFM) zero current switching (ZCS) series resonant (SR) inverter fed dc high voltage power supplies have nearly zero switching loss. However, they have limitations like narrow variation of output voltage and poor control at light load. To alleviate these limitations, this paper proposes a multi-output ZCS-SR inverter fed high voltage dc-dc converter. The SR-inverter in the proposed system has four outputs that are connected to a single transformer linked load via four resonant capacitors each of which have distinct capacitance. Due to distinct values of resonant capacitors, the impedance of tank circuit and hence the power transformer rate is different for four outputs. Thus all the four inverter outputs are fed to load in parallel when maximum load power is desired and a single output that has highest tank circuit impedance is fed to load when lowest load power is required and vice versa. For the four inverter outputs there are sixteen possible combinations to feed them to load in parallel, thus the load power increase from its lowest value to highest in sixteen steps. Switching frequency is adjusted within in its narrow limits to adjust the voltage between two nearest steps. The proposed system has been simulated using PSPICE software. The obtained results show that proposed system has several advantages such as wide range of output voltage control, low output voltage ripple over the entire range and low current stress at light load.

This paper proposes a multi-output ZCS-SR inverter fed voltage multiplier based high voltage dc-dc converter to achieve wide range of controllability. The SR-inverter in the proposed system has four outputs that are connected to a single transformer linked load via four resonant capacitors each of which have distinct capacitance. Due to distinct values of resonant capacitors, the impedance of tank circuit and hence the power transfer rate is different for four outputs. Thus all the four inverter outputs are fed to load in parallel when maximum load power is desired and a single output that has highest tank circuit impedance is fed to load when lowest load power is required and vice versa. For the four inverter outputs there are sixteen possible combinations to feed them to load in parallel, thus the load power increase from its lowest value to highest in sixteen steps. Switching frequency is adjusted within in its narrow limits to adjust the voltage between two nearest steps. Proposed high voltage converter have several features such as wide range of control, less voltage ripple and low current stress on power switches. The proposed converter is simulated using PSPICE software and results confirm its better performance.

This paper presents the use of a digitally tuned resonant capacitance control with narrow range frequency modulation to regulate the output voltage of a zero current switching series resonant (ZCS-SR) inverter-fed transformer-linked DC-DC converter for X-ray power supply application. In this control scheme, the series resonant inverter consists of several capacitors which are switched into and out of resonant tank circuit by relays. The capacitance of the resonant tank is modulated digitally by controlling the closure of relays which causes the output voltage to increase or decrease in steps. The output voltage in between any two adjacent steps is adjusted by varying the switching frequency in a narrow range. By modulating both resonant tank capacitance and switching frequency, it is able to regulate the output voltage over a wide range. Furthermore, the switching losses of the proposed system are eliminated with all switches operating under soft switching conditions over the entire range of output voltage. Verification of the proposed system is done by computer simulation using Orcad PSPICE.