Grid‐tie inverter topology with maximum power extraction from two photovoltaic arrays

Abstract

This study presents a transformerless topology for a grid-tied single-phase inverter capable of performing the simultaneous maximum power point tracking of two independent and series connected photovoltaic sources. This topology is derived from the neutral point clamped multilevel inverter in half-bridge configuration. The use of a half-bridge topology reduces the leakage current to very low values, whereas the multilevel topology presents an output voltage quality similar to that of a full-bridge inverter. To simultaneously track the maximum power of both photovoltaic sources, a generation control circuit is used. With this topology, it is possible to improve the performance of the converter under partial shadowing conditions, very common in photovoltaic facilities operating in residential areas. A 5 kW prototype of this topology has been implemented and tested in the laboratory.

An optimal current control scheme in grid‐tied hybrid energy system with active power filter for harmonic mitigation

“…The FLPID feedback controller acts as a dc‐link controller to maintain the dc‐link bus voltage at a constant value, which is shown in Figure A. The maximum power point tracking (MPPT) technique is executed by using an incremental conductance strategy for both PV and wind energy systems . The DC bus is tied to AC bus terminals via three‐phase VSI.…”

A Simplified PWM Strategy for a Neutral-Point-Clamped (NPC) Three-Level Converter With Unbalanced DC Links

“…Content may change prior to final publication. can be represented by (20) instead of (13) and (14). The maximum linear modulation index of the other sectors is also 1.15 as the sector 1.…”

“…12, the reference average current of the NP potential is obtained through the unbalanced coefficient feedback control with PI controller. The principles of selecting the reference unbalanced coefficient k ref are important to improve the system efficiency, for example, up and down solar panels' independent MPPT algorithm [20]- [23] can be adopted to adjust k ref in the field of photovoltaic generation. Then, T ∆ can be calculated by substituting the obtained reference average current of the NP potential in (31) with the process of amplitude limiting.…”

“…For the three-level NPC converter with unbalanced dc-links, there exists the same problem owing to the break of the voltage-second rule if the conventional SVPWM is adopted. In the field of photovoltaic generation, two independent and series connected photovoltaic sources are usually straight forward to the upper and lower dc-links [20]. The two dc-link voltages are sometimes far different due to problems such as different orientation of PV panels, partial shadows or accumulated dust.…”

“…In these cases, the low order harmonics produced by the grid-tied inverters will pollute the grid seriously. A topology formed by a NPC inverter in a half-bridge configuration and a classical buck-boost dc-dc converter is proposed in [20] to solve the partial shadowing problem effectively, but extra dc-dc converter will make it expensive. Besides, the up and down dc-links need to adjust independently, i.e., the voltages of two solar panels should be adjusted independently to realize their MPPT [20]-[23] control simultaneously.…”