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This paper proposes a switching strategy for the Z-source inverter (ZSI), which has unequal short-through intervals to reduce the current ripple in the inductor of its impedance source. A size reduction of the inductor of the ZSI is one of the important issues in improving the power density of the ZSI, and the inductor current ripple reduction is required to achieve it. The proposed method can reduce the inductor current ripple by 27.8% compared with the conventional method that has equal short-through intervals without increasing the number of inverter switching. The proposed operation and ripple reduction were confirmed in experiments with a 3-kW-class laboratory prototype. Its result agreed to the calculated results, and it was confirmed that there is no increase in circuit losses caused by the application of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a step in microlevel photovoltaic (PV) summation technology for combining unsymmetrical PV modules with differences in specification and age, relocation on nonfertile land, or multilocation mounting by designing an add-on modular hardware interface to a multi-input single-output (MISO) dc bus, using an MISO controller employing a suitable maximum power point (MPP) tracker under partial shading/long distance/mismatching PV module conditions along with a sensor-less PV vector control inverter (PV–VCI) driving a three-phase asynchronous squirrel cage induction motor dedicated to irrigation, with the facility of autoconfiguration/autotuning at the beginning. A PV source gets automatically added/removed in a ramp profile in proportion to the load in steps, thus keeping on only when required, enabling high efficiency, minimum heating, and prolonged life as that of a PV module. The contribution includes a reduced PV energy cost per watt by 24.10%, improved return on investment by 27.48%, improved water discharge yield by 11.06%, and improved MPP tracker impact by 14.59% with 90.88% MISO system efficiency compared to a normal scheme. [ABSTRACT FROM AUTHOR]

This paper investigates a multilevel inverter composed of series/parallel-connected H-bridges. The presented structure can be used for applications in which the use of semiconductor switches with low-voltage and low-current ratings is intended. A comprehensive system model, an overall control strategy to adjust the output voltage with constant magnitude and frequency, and a level-shifted PWM (LS-PWM) strategy based on a voltage vectors unidimensional analysis and a plane analysis are presented. The LS-PWM is capable of mitigating the low-frequency circulating current, thus generating multilevel voltage signals with low harmonic distortion, maximum number of levels, and low dv/dt. In addition, considering a wide range of values of voltages and currents and various power levels, the total converter losses are reduced compared with the conventional multilevel converters. Two multilevel conventional inverters with the same number of semiconductor switches are used for comparison. Simulation and experimental results demonstrate the feasibility of the studied converter. [ABSTRACT FROM AUTHOR]

This paper proposes a novel bidirectional inverter, named series ac-link inverter. This three-phase inverter belongs to a new class of partial resonant ac-link converters in which the link is formed by a series ac inductor/capacitor (LC) pair having low reactive ratings. The input and output of this converter can be either dc, ac, single-phase, or multiphase. Therefore, they can appear as dc–dc, dc–ac, ac–dc, and ac–ac configurations. In all of these configurations, the ac capacitor is the main energy-storage element, and the inductor is merely added to facilitate the zero-current turnoff of the switches and their soft turn-on. Due to the zero-current turnoff of the switches in the proposed converter, the use of SCRs with natural commutation is possible as well. Since the current and voltage of the link are both alternating, no bulky dc-electrolytic capacitors are required in this converter. This paper mainly focuses on bidirectional dc to three-phase ac conversion. This single-stage inverter can step up or step down the voltage in a wide range. If galvanic isolation is required a single-phase high-frequency transformer can be added to the link. In the proposed inverter, the power can flow in both directions, and therefore, it is an excellent candidate for battery-utility interface and electric vehicle applications. In this paper, the principles of the operation of the proposed inverter, along with its design and analysis, are studied. Moreover, the performance of the proposed configuration is evaluated in this paper. Both simulation and experimental results are included. [ABSTRACT FROM AUTHOR]

This paper proposes a new circuit configuration and a control scheme for a single-phase current-source inverter with a power decoupling circuit which is called as the active buffer. The proposed inverter achieves a low-dc-input voltage ripple and also provides a sinusoidal current that can achieve unity power factor, without large passive components in the dc bus such as smoothing inductors and electrolytic capacitors. These components are conventionally required in order to decouple the power pulsation caused by the single-phase power source. In this paper, the fundamental operations of the proposed inverter are demonstrated experimentally. From the experimental results, the input voltage ripple is 8.87%, and the output current total harmonic distortion is 4.24%. In addition, an output power factor of 99% and a maximum efficiency of 94.9% are obtained. Finally, it is confirmed that the maximum power densities of the conventional circuit and the proposed circuit are 2.75 kW/L at the switching frequency of 70 kHz and 4.86 kW/L at the switching frequency of 80 kHz, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a variable switching point predictive current control (VSP $^2$CC) for the quasi-Z-source inverter (qZSI). The proposed VSP $^2$CC aims to remove the output current error on the ac side, as well as the inductor current and capacitor voltage errors of the quasi-Z-source network on the dc side of the converter. Unlike the previously presented direct model predictive control (MPC) strategies for the qZSI, the proposed control scheme can directly apply the switching signals not only at the discrete time instants, but at any time instant within the sampling interval. Consequently, the shoot-through state can be applied for a shorter time than the sampling interval, resulting in lower output and inductor currents ripples. Experimental results based on field programmable gate array are provided to verify the effectiveness of the introduced control method. As it is shown, the proposed method leads to lower inductor current ripples and less output current total harmonic distortion when compared with the conventional direct MPC. [ABSTRACT FROM AUTHOR]

This paper identifies the characteristics of a current source inverter operating in discontinuous conduction mode, and proposes a new multiobjective pulse-width modulation (PWM) method to mitigate voltage boosting and harmonic distortion effects. The method takes into account load impedance effects. Controls are also developed to enable transition between the multiobjective PWM method and conventional PWM as the current source inverter operates in discontinuous and continuous modes of operation. The concept is verified experimentally on a 3 kW test bed. [ABSTRACT FROM AUTHOR]

The conventional current-source inverter has two major problems: unidirectional power flow and voltage boost operation, which make it impossible to be used in many applications, such as hybrid electric vehicles and general-purpose variable-speed motor drives. Z-source inverters (ZSIs) can solve both problems. Quasi-ZSIs (qZSIs) were recently proposed as an important improvement to traditional ZSIs. Besides the advantages inherited from ZSIs, qZSIs also have several of their own merits. This paper presents a comprehensive study on the new features of current-fed qZSI, including the advantageous buck–boost function, improved reliability, reduced passive component ratings, and unique regeneration capability. The current-fed qZSIs are bidirectional with an additional diode, unlike the voltage-fed ZSI that needs a switch to achieve bidirectional power flow. A modified space vector pulse-width-modulation method is proposed, and the available operating regions for motoring and regeneration operation are analyzed in this paper. Since the current-fed qZSI has the same operation as the current-fed ZSI, many results of this paper are also applicable to the current-fed ZSI. A reverse-blocking insulated-gate bipolar-transistor-based current-fed qZSI prototype was developed in the laboratory. Simulation and experimental results are shown to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel 3 $\phi$ stand-alone solar photovoltaic (PV) system configuration that uses high-gain high-efficiency $(\approx\! 96\%)$ dc–dc converters both in the forward power stage and the bidirectional battery interface. The high-voltage-gain converters enable the use of low-voltage PV and battery sources. This results in minimization of partial shading and parasitic capacitance effects on the PV source. Series connection of a large number of battery modules is obviated, preventing the overcharging and deep discharging issues that reduce the battery life. In addition, the proposed configuration facilitates “required power tracking (RPT)” of the PV source as per the load requirements, eliminating the use of expensive and “difficult to manage” dump loads. High-performance inverter operation is achieved through $abc$ to $dq$ reference frame transformation, which helps in generating precise information about the load's active power component for RPT, regulation of ac output voltage, and minimization of control complexity. Inverter output voltage is regulated by controlling the modulation index of sinusoidal pulsewidth modulation, resulting in a stable and reliable system operation. The active power demand is controlled by regulating the dc link voltage. All the analytical, simulation, and experimental results of this work are presented. [ABSTRACT FROM PUBLISHER]