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The multi-string photovoltaic (PV) inverter is of interest for building grid-connected PV systems because it offers a number of advantages compared to conventional centralized or single-stage inverters. Optimal operation of the system can be achieved since the maximum power point (MPP) of each string is controlled by a local dc-dc converter input stage. The input dc-dc converter also provides voltage...
Solar converters to feed the energy from the solar module into the AC grid consist of a DC/DC and a three phase DC/AC converter decoupled by a capacitor in the DC link which is to be minimized. A current fed instead of a voltage fed full bridge DC/DC converter is chosen and leads to a higher efficiency. Furthermore undesirable voltage spikes can be avoided by the use of this topology. This paper presents...
This paper presents a review of some techniques for islanding detection, especially by using inverter based DG applications and it also focuses on several islanding detection methods for a single-phase current-control voltage inverter working with a PV system connected into the grid. It is deliberated a single-phase inverter with maximum power of 5 kW. Islanding detection methods are investigated,...
This paper proposes a versatile system to test and measure systematically the real evolution for the I-V characteristic curves of photovoltaic (PV) modules or arrays. The system employs a novel circuit solution based on DC-DC converters that shows several advantages with regard to classical methods: simple structure, scalability, fast response and low cost. The measure of the desired characteristics...
European efficiency definition demonstrates that photovoltaic generators operate in average between 30% and 100% of its rated power 80% of its working time. Nowadays, converters are designed with a maximal efficiency working point, but often, this point does not fit with the correct power range. This paper presents a structure with a parallel connection of n converters to obtain higher conversion...
This paper presents a novel modulation for a two-stage dc-ac power converter with high-frequency isolation installed in a photovoltaic stand-alone system. The presented modulation, which is designed for the converter discontinuous conduction mode of operation, solves the problem of connection to a grid, and permits a bidirectional power flow. In this document is described the modulation strategy and...
This paper presents the analysis and implementation of an LCLC resonant converter working as maximum power point tracker (MPPT) in a PV system. This converter must guarantee a constant DC output voltage and must vary its effective input resistance in order to extract the maximum power of the PV generator. Preliminary analysis concludes that not all resonant load topologies can achieve the design conditions...
This paper presents a new class of pulsewidth modulation (PWM) DC-to-DC converters with quadratic conversion ratios for photovoltaic applications without a transformer. The aim of these structures is to obtain at the same time high conversion ratio and excellent efficiency for a wide source voltage range. The DC voltage conversion ratios of these converters have a quadratic dependence on duty cycle...
Photovoltaic (PV) inverters convert the DC current of solar generators into AC current and feed it into the grid. There are three basic inverter topologies: inverters with low frequency (50/60 Hz) transformer (LF), inverters with high frequency transformer (HF) and transformer-less inverters (TL). The European market is dominated by transformer-less types (80%), in Japan approx. 50% of the inverters...
This paper investigates the interactions which arise between grid connected photovoltaic inverter systems and the electrical grid. In particular, it considers the effect of grid voltage harmonics and grid impedance on the current control performance of grid connected inverter systems. In these photovoltaic inverter systems it is usual to control unity power factor, sinusoidal, current into the grid...
Grid codes are being revised to include additional requirements for renewable energy, as the installed power increases. Therefore it is needed to develop control systems that are able to fulfil those new requirements, which usually include the ability to operate under unbalanced grid voltages without polluting the grid, among others. This paper presents a three-phase inverter for connection of photovoltaic...
In this paper the implementation and the performance of 1200 V / 30 A / 65 mOmega normally-off SiC-JFETs in photovoltaic inverters (PV-inverters) is shown and compared with Si-IGBTs. The JFETs' low switching energy and on-resistance lead to an improvement of efficiency and a reduction of costs and weight of PV-inverters.
In this paper a DC power plant for base transceiver station power supply is investigated. The supply system employs clean alternative energy sources, namely photovoltaic (PV) modules, wind turbines, a fuel cell as backup generator and a storage battery bank. A detailed description is made and experimental data are shown of a prototype system where the PV modules are directly connected to the DC bus...
Grid connected solar inverters are used to feed energy generated by a photovoltaic generator into the mains. High efficiency is a major requirement. Furthermore a low total harmonic distortion (THD) of the output current is needed to comply with regulations. This paper presents the control for a new highly efficient inverter topology. Due to disturbances of the grid voltage and non-linear effects...
A novel MPPT algorithm for three-phase grid-connected photovoltaic generation systems is presented in this paper. Reference is made to a conversion scheme consisting in two balanced arrays of PV modules, each one feeding a standard 2-level three-phase voltage source inverter (VSI). The dc-link voltages of each VSI are regulated according with the requirement of the proposed MPPT algorithm, based on...
The grid-connected photovoltaic (PV) systems are an important part of renewable energy sources and their integration is getting more and more widespread. In order to improve the efficiency, practicality and reliability of the PV systems, many kinds of new inverter topologies have been proposed to avoid using a grid isolation transformer. The NPC topology and two other derived topologies are presented...
In this paper a methodology of sizing optimization of the stand-alone hybrid energy systems is presented. This approach makes use of a deterministic algorithm to suggest, among a list of commercially available system devices, the optimal number and type of units ensuring that the total costs of the autonomous hybrid wind/PV/Diesel, wind/Diesel and PV/Diesel energy systems are minimized while guaranteeing...
The major idea pointed out in this paper concerns the combination of a photovoltaic (PV) grid-feeding inverter with a motor control unit for two-axis solar trackers. The integration of a PV or concentrating PV (CPV) two-axis tracker position control unit, i.e. power electronics to supply the drives as well as sun tracking algorithms, into a specially designed grid-feeding inverter turns it into a...
The design of a hybrid solar/wind/Biomass electrical energy supply system is presented. Power requirements for a typical Algerian isolated village and the sizing of the electrical circuit are described. Some simulation results on PV solar panels and wind turbines behavior for different temperatures and wind speeds respectively are also given. A power flow strategy is also proposed. The objective is...
Within the framework of photovoltaic systems connected to the grid, the potential of innovative semiconductor technologies with special focus on SiC devices will be analyzed. The properties of a SiC D-MOSFET will be experimentally examined firstly as a discrete element and then in a laboratory prototype of a highly efficient inverter circuit. The gain on efficiency and possible increase on the switching...
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