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Photovoltaic (PV) is a promising way to meet the increasing global energy demand due to its sustainability, efficiency, and cost-effectiveness. For the wide-scale adoption of PV systems, converters with reliable input sources, stable control strategies and appropriate modulation techniques must be designed. In the literature, various modulation techniques have been developed that help to boost the voltage of the PV modules by implementing shoot-through (ST) in which the upper and lower switches of an inverter conduct simultaneously and short-circuit occurs. Various optimised modulation techniques have been implemented to enhance its performance. Among those, the quasi-Z-source inverter (qZSI) has attracted much attention due to its ability to achieve higher conversion ratios for grid-connected PV applications. In this paper, a detailed comparison of the modulation schemes for the qZSI PV systems has been done to understand the trade-off and select the most suitable approach. Upon the selection of the space vector modulation with unique switching sequences and rearranging upper ST and lower ST states, the inverter can achieve ST with reduced switching losses. Furthermore, a 600 VA three-phase grid-connected system utilizing a three-level neutral-point-clamped qZSI topology is modulated and simulated. It has been demonstrated that the constant boost control offers good performance in terms of reduced voltage stresses on switches, lower total harmonic distortion, and hence, higher efficiency.

This paper proposes a new PWM technique for a reduced-component-count active impedance network (RCC-AIN) three-level inverter to maximize the input/output (I/O) voltage gain. Although the max boost control (MBC) technique offers the same I/O voltage gain, it suffers from the drawback of low-frequency (LF) ripples of the source current. In contrast, the proposed PWM technique is a combination of improved MBC (IMBC) and a new switching state pattern that eliminates this drawback and offers up to 79% reduction in the peak-to-peak ripple value of the source current while maintaining the same I/O voltage gain as MBC. The cumulative sum of ripple components is used to find the exact maximum and minimum peaks of the source current over the fundamental period. The proposed switching pattern doubles the switching frequency of a boosting switch to limit the current spikes of capacitors during state change-over. The RCC-AIN topology was analyzed in various voltage-boosting techniques, and the proposed PWM technique utilizes the full potential of the RCC-AIN topology in a better way. The findings have been verified using theoretical calculations, simulation, and experimental results.

Low voltage stress on the impedance source network devices is the main reason for the advent of DC-linked type quasi-switched boost inverters (DqSBIs). However, the DqSBI has become less attractive due to its low voltage gain. This paper presents a novel PWM control strategy for the DqSBI and its comparative performance evaluation to the conventional inverters. The modified PWM control strategy based DqSBI improves the voltage gain and reduces the conduction loss and the inductor current ripple. Circuit analysis and comparison study between the DqSBI, the quasi-Z-source inverters, and the two-stage inverter with a boost DC-DC converter are presented. 1-kVA three-phase inverter prototypes were set up to compare and evaluate the performance of the DqSBI with the improved PWM method for voltage gains of 0.85 to 1.6. The measured efficiency and total harmonic distortion (THD) values are also presented.

A grid-tied, single stage, three phase, PV system provides higher efficiency than a two-stage PV system. This paper presents a three-phase, single stage, grid-connected PV system with MPPT and reactive power injection capability into the grid using modified capacitor assisted extended boost quasi Z-source inverter (MCAEB q-ZSI) as the grid-tied PV inverter. The adaptability of the inverter for irradiance changes and the boost factor control with its shoot-through duty ratio adjustment made it highly recommended for the grid system. The shoot-through control technique like maximum constant boost control with a third harmonic injection enhances the performance of the inverter by reducing the low order ripples and voltage stress. The fuzzy voltage controller is proposed with the capacitor linearization algorithm to regulate the DC-link voltage. The current approach uses a fuzzy controller to control the real and the reactive power injection into the grid. The performance evaluation of the fuzzy and PI grid controller is carried out for the constant irradiance condition and from the investigation, parameters like boost factor (B), the shoot-through duty ratio(Ds), real power (P), reactive power (Q), power factor and harmonics in the current injection are determined. A laboratory setup of the PV powered grid system is implemented, tested and validated with the simulation results. ABSTRAK: Dalam sistem fotovoltaik (PV) yang bersambung dengan satu peringkat, satu sistem elektronik kuasa yang mempunyai keuntungan dan kecekapan yang tinggi diperlukan untuk menginterupasi dengan utiliti tersebut. Dalam makalah ini, kapasitor yang diubah suai dibantu oleh pemacu kuadratik Z-source yang dilanjutkan (MCAEB q-ZSI) bertindak sebagai unit interfacing antara PV dan grid. Penyesuaian penyongsang untuk perubahan sinaran dan kawalan faktor rangsangan dengan pelarasan nisbah tugas menembak membuatnya sangat disyorkan untuk sistem grid. Teknik kawalan menembak seperti kawalan rangsangan berterusan maksimum dengan suntikan harmonik ketiga meningkatkan prestasi penyongsang dengan mengurangkan aruhan pesanan rendah dan tekanan voltan. Pendekatan semasa menggunakan pengawal kabur untuk mengawal suntikan kuasa sebenar dan reaktif ke grid. Penilaian prestasi pengawal grid fuzzy dan PI dilakukan untuk keadaan iradiasi malar dan dari penyiasatan, parameter seperti faktor rangsangan (B), nisbah tugas menembak (Ds), kuasa nyata (P), kuasa reaktif Q), faktor kuasa dan harmonik dalam suntikan semasa ditentukan.

In this paper, a new topology for cascaded multilevel inverter based on quasi-Z-source converter is proposed. In the proposed topology the magnitude of output DC voltage is not limited to the sum of magnitude of DC voltage sources. Moreover, the reliability of the circuit due to capability of short circuit by Z-source network is increased. The quasi-Z- source converter in different modes is analyzed and the voltage gain is obtained. Also, the values of quasi-Z-source network components are designed. In the proposed topology, the number of DC voltage sources, the number of switches, installation area and cost in comparison with conventional multilevel inverters are significantly reduced. Three algorithms to determine the magnitude of DC voltage sources are proposed. Then the optimal structures for the minimum number of switches and DC voltage sources to generate the maximum voltage levels are presented. Moreover, the control method for the proposed topology is described. To verify the performance of the proposed topology, simulation and experimental results of proposed topology are presented.

In this paper, an embedded half-bridge Z-source inverter based on gamma structure is proposed. In contrast with the classical half-bridge inverter, the proposed inverter can generate zero voltage levels in output. High voltage gain and low voltage stress on capacitors are the main advantages of the proposed converter. The value of the boost factor in the proposed structure is increased by changing both the shoot-through (ST) duty cycle and turns ratio of the transformer. The operating principle of the proposed converter in four operating modes is presented. We also calculate the critical inductance and compare the proposed converter with conventional topologies. In addition, power loss and THD analysis are presented. Finally, PSCAD/EMTDC software is used to verify the correct operation of the proposed inverter and the experimental results.

A new modulation strategy has been introduced in this paper in order to enhance the boost factor for the three-level quasi-switched boost T-type inverter (3L-qSBT2I). Under this approach, the component rating of power devices is significantly decreased. Moreover, the use of a larger boost factor produces a smaller shoot-through current. This benefit leads to reducing the conduction loss significantly. Furthermore, the neutral voltage unbalance is also considered. The duty cycle of two active switches of a quasi-switched boost (qSB) network is redetermined based on actual capacitor voltages to recovery balance condition. Noted that the boost factor will not be affected by the proposed capacitor voltage balance strategy. The proposed method is taken into account to be compared with other previous studies. The operation principle and overall control strategy for this configuration are also detailed. The simulation and experiment are implemented with the help of PSIM software and laboratory prototype to demonstrate the accuracy of this strategy.

In recent years, the three-level T-Type inverter has been considered the best choice for many low and medium power applications. Nevertheless, this topology is known as a buck converter. Therefore, in this paper, a new topology incorporating the dc-link type quasi-switched boost network with the traditional three-level T-type inverter is proposed to overcome the limit of traditional three-level T-Type inverter. The space vector pulse width modulation scheme is considered to control this topology, which provides some benefits such as enhancing modulation index and reducing the magnitude of common-mode voltage. For this scheme, the zero, medium, and large vectors are utilized to generate the output voltage. The shoot-through state which is adopted by turning on all power switches of inverter leg is inserted into zero vector to boost the dc-link voltage. As a result, there is no distortion at the output waveform. The control signal of intermediate network power switches is also detailed to improve the boost factor and voltage gain. As a result, the voltage stress on power devices like capacitors, diodes, and switches is decreased significantly. To demonstrate the outstanding of proposed structure and its control strategy, some comparisons between the proposed method and other ones are performed. Simulation and experimental prototype results are conducted to verify the accuracy of the theory and effectiveness of the inverter.

In this paper, a new topology for boost Z-source inverterbased on switched-inductor cell is proposed. The operating modes of the proposed inverter are analyzed and also a suitable control method to generate the trigger signals of the inverter is presented. Having a common earth between the input source and inverter and capability to generate a higher voltage gain by using lower amounts of the duty cycles are some advantages of the proposed Z-source inverter. Comparison of the proposed inverter with conventional Z-source inverters is presented from different points of the view. Finally, the accuracy performance of the proposed inverter is reconfirmed through the simulation results in EMTDC/PSCAD software program.

Este trabalho apresenta o cálculo dos esforços de corrente nos semicondutores do inversor fonte Z trifásico operando com a modulação Boost Simples. O inversor fonte Z possui uma malha de impedância conhecida como malha Z, que possibilita realizar as funções CC-CC elevador e CC-CA em um único estágio. Por possuir essa característica, este conversor se torna uma opção interessante em aplicações com células fotovoltaicas. Serão apresentadas as etapas de operação e as equações que regem o funcionamento do inversor operando com a modulação Boost Simples para que se possa entender o desenvolvimento do equacionamento dos valores médio e eficaz nos semicondutores. A etapa Boost é definida por uma nova etapa conhecida como shoot-through, em que os semicondutores do mesmo braço conduzem simultaneamente. Esta característica altera profundamente o comportamento das correntes, exigindo um cálculo complexo dos esforços. Para validar os cálculos, os resultados teóricos são comparados com os resultados obtidos na simulação, assim como os dados experimentais.