SHE Control for PV System Connected to the Grid

In this article, we have proposed a new control of a PV system connected to the grid. The goal is to reduce current and voltage harmonicsfor increasing the quality of delivered energy. First, we have modeled a PV panel. Then we have dimensioned the BOOST converter by finding L and C values. Next, we have used Perturb and Observe (P&O) Maximum Power Point Control (MPPT) to improve energy efficiency. Finally, We have developed a control of single-phase H-bridge inverter in order to eliminate the 3rd,5th,7th and 9th harmonics order, and added an LCLTo connect the PV inverter to the grid, an LCL betweenthe inverter and the grid. Theperformance of the proposed system was tested by computing spectrum and THD usingMatlab/Simulink software. The proposed architecture provides better Total Harmonic Distortion (THD) which satisfy the EN50160 requirement the THD must be less than 4.66%. We found that THD was decreased from 61.93% to 0.04%

Analysis and Design of Solar Power System Interface Utility Using ZVS Converter

The solar power generation system with minimal losses, high simplicity and easy control is attempted in this work, by developing a grid-tied zero-voltage switching (ZVS) inverter with a less number of power conversion stages and the least count of passive components, for single-phase applications that are suitable for conversion from low-voltage DC (40-60 V) to line voltage AC (230 VAC; RMS) at average power levels of 175 W and below. The ZVS full-bridge inverter fed from a PV panel is working on higher frequency with an asymmetric auxiliary circuit, which guarantees ZVS at the switching instants of the metal-oxide-semiconductor field-effect transistors (MOSFETs) by supplying the reactive current to these full-bridge semiconductor switches and reducing the switching losses. Checking of the constructional workability and analytical feasibility of the proposed topology with the highest efficiency and the simplest control was the target of this work, which was set on the basis of the results obtained in the MATLAB Simulink environment. The control strategies were planned for the optimum value of the reactive current injected by the auxiliary circuit to guarantee ZVS and use of phase shifted pulsewidth modulation (PWM) with varying frequencies for the full-bridge inverter and half-bridge cyclo-converter. The hybrid maximum power point tracking (MPPT) was part of this plan used to set the power at its maximum value against the environmental changes.Citation: Deshbhratar, R. G., and Renge, M. M. (2018). Analysis and Design of Solar Power System Interface Utility Using ZVS Converter. Trends in Renewable Energy, 4, 83-101. DOI: 10.17737/tre.2018.4.3.005

Design and implementation of a dual-input single-output photovoltaic converter

In many solar inverters, a dc/dc converter is mainly located between the solar arrays and the inverter. This study presents an enhanced maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems that drives solar array voltages to track a reference value and decreases fluctuations and oscillations in PV voltage. Different from the previously presented methods, a novel MPPT method is proposed that ensures tracking accuracy by considering output voltage in addition to input voltage and currents. The proposed method detects dI/dV variations, compares the output voltage with the desired reference to shift operation mode and refreshes step size. The digital filtering, enhanced PI, and perturb-and-observe (P&O) tracking features of the proposed MPPT method make it robust to mitigate source fluctuations and sensitivity to partial shading based oscillations. In order to validate the success of the proposed method, a test rig has been installed with dual boost converters. The performance improvements have been verified by both simulation and experimental results that are compared to InCon and P&O MPPT methods. It is also confirmed by experimental results that the proposed MPPT method provides robust control capability in terms of tracking the reference voltage and rejecting the effects of various shading situations on solar arrays

Triple-Mode Flying Inductor Common-Ground PV Inverter with Reactive Power Capability and Low Semiconductor Component Count

This paper proposes the flying inductor based common ground single-phase PV inverter which can support reactive power to the ac grid. The proposed buck-boost transformerless PV inverter eliminates the leakage current and is suitable for use in on-grid applications which require active and reactive power support. The proposed converter also features a low number of semiconductor devices, no ac type capacitor, acceptable quality of the grid side current even during non-unity power factor operations, reducing switching loss by adopting time-sharing technique, and high efficiency. The converter uses a dead-beat controller in the control loop which has a smooth, accurate and fast response. Experimental results for a 500 W, 100 Vdc and 180 Vdc to 110 Vrms, prototype is provided in a closed-loop system in the presence of the proposed dead-beat controller. The results from the prototype validate the theoretical analysis and the applicability of the proposed structure. The converter exhibits the capability for stepping up the dc to ac power conversion and demonstrates a peak efficiency of 97.2% and 96.8% from 180 Vdc and 100 Vdc, respectively

Buck-boost single-stage microinverter for building integrated photovoltaic systems

Microinverters for Building Integrated Photovoltaic (BIPV) systems must have had a small number of components, be efficient, and be reliable. In this context, a single-phase Buck-Boost Single-stage Microinverter (BBSM) for grid-connected BIPV systems is presented. The concept of topology is extracted from the buck-boost converter. The leakage current in the system is kept under control. It uses an optimal number of active and passive components to function at a high-efficiency level. The suggested topology provides a high level of reliability due to the absence of shoot-through problems. To validate the findings, a simulation in combination with an experimental system for a 70 W system is developed with the design approach. The efficiency of the microinverter, total harmonic distortion of the grid current are measured as 96.4% and 4.09% respectively. Finally, a comparison study has indicated the advantages and disadvantages of the suggested inverter

Transformerless Inverter Topologies for Single-Phase Photovoltaic Systems:A Comparative Review

In photovoltaic (PV) applications, a transformer is often used to provide galvanic isolation and voltage ratio transformations between input and output. However, these conventional iron-and copper-based transformers increase the weight/size and cost of the inverter while reducing the efficiency and power density. It is therefore desirable to avoid using transformers in the inverter. However, additional care must be taken to avoid safety hazards such as ground fault currents and leakage currents, e.g., via the parasitic capacitor between the PV panel and ground. Consequently, the grid connected transformerless PV inverters must comply with strict safety standards such as IEEE 1547.1, VDE0126-1-1, EN 50106, IEC61727, and AS/N ZS 5033. Various transformerless inverters have been proposed recently to eliminate the leakage current using different techniques such as decoupling the dc from the ac side and/or clamping the common mode (CM) voltage (CMV) during the freewheeling period, or using common ground configurations. The permutations and combinations of various decoupling techniques with integrated voltage buck-boost for maximum power point tracking (MPPT) allow numerous new topologies and configurations which are often confusing and difficult to follow when seeking to select the right topology. Therefore, to present a clear picture on the development of transformerless inverters for the next-generation grid-connected PV systems, this paper aims to comprehensively review and classify various transformerless inverters with detailed analytical comparisons. To reinforce the findings and comparisons as well as to give more insight on the CM characteristics and leakage current, computer simulations of major transformerless inverter topologies have been performed in PLECS software. Moreover, the cost and size are analyzed properly and summarized in a table. Finally, efficiency and thermal analysis are provided with a general summary as well as a technology roadmap.</p

Power Converter of Electric Machines, Renewable Energy Systems, and Transportation

Power converters and electric machines represent essential components in all fields of electrical engineering. In fact, we are heading towards a future where energy will be more and more electrical: electrical vehicles, electrical motors, renewables, storage systems are now widespread. The ongoing energy transition poses new challenges for interfacing and integrating different power systems. The constraints of space, weight, reliability, performance, and autonomy for the electric system have increased the attention of scientific research in order to find more and more appropriate technological solutions. In this context, power converters and electric machines assume a key role in enabling higher performance of electrical power conversion. Consequently, the design and control of power converters and electric machines shall be developed accordingly to the requirements of the specific application, thus leading to more specialized solutions, with the aim of enhancing the reliability, fault tolerance, and flexibility of the next generation power systems

Quasi impedance source based high power medium voltage converter for grid integration of distributed energy sources

The next generation of Power Electronics systems would need to be able to work at higher power levels, higher switching frequencies, compact size, and higher ambient temperatures, as well as should have improved energy efficiency than existing Silicon (Si) devices. As a result, new wide bandgap semiconductor technologies must be introduced to address Si's physical limitations. Silicon Carbide (SiC) devices are becoming popular because of their outstanding properties that address all the requirements of the next generation Power Electronics system. On the other hand, the converter topology still plays a major role in deciding the overall system performance. Hence the major objective of this dissertation is to devise new multilevel quasi impedance source (qZS) based converter topologies using SiC devices to achieve a compact, highly efficient, and modular solution for grid integration of Solar PV Energy Source to the utility grid. Other objectives include modification in the PWM methods to address the problem of unequal power-sharing in Solar PV multilevel converters. By using qZS as the front-end power converter several different power converter topologies have been developed and presented in this dissertation. The detailed design, modulation, loss analysis, and control have been developed for multi module cascaded structure. Level-shifted PWM technique is developed at first for two cascaded modules which are similar to the standard Phase opposed disposed Pulse width modulation (PODPWM). However, this control method cannot be directly applied to a higher number of modules. For more than two cascaded modules a unified combined hybrid PWM technique is developed and presented. During normal balanced operation, the power among the modules is unequal. To address the unequal power sharing problem, further modification in the PWM technique is done called the Carrier rotation technique. For providing the isolation between the low voltage PV panels and the high voltage AC grid, a modified Inverter topology, and a new modulation technique is developed. The presented technique, however, is limited to a single module, and more research is needed to implement for cascaded structure. Front-end qZS based single-stage DC-AC-DC converter is developed as an alternative of one of the most popular conventional dual active bridge (DAB) converter. The proposed converter offers reduced component count while maintaining the continuous input current. The detailed operation, modulation technique, simulation, and experimental result are presented to show the superiority of the developed qZS Cascaded Multilevel Converter. The developed power converter has strong commercialization potentia