Reactive power control of grid-connected photovoltaic micro-inverter based on third-harmonic injection

<span lang="EN-US">This paper presents four interleaved flyback DC-DC converters. Each flyback converter contains a separate maximum power point tracker (MPPT). The MPP tracker is used to collect the maximum power value from photovoltaic panel by using (P&amp;O) algorithm with an output of reference current. In latest years, the active third-harmonic injection circuit have received much interest, this technique contributed to getting a better quality of injection current into the utility grid and control the reactive power. For converting direct current to three-phase sinusoidal currents, a line-commutated current source inverter type (CSI) with filter is used. The developed micro-inverter of (1000 W) offers an expanded range of reactive power control with balanced three-phase output power and good efficiency 95.07%. The effectiveness of the suggested system is clarified through the MATLAB program simulation. The system proposed in this paper has proven its effectiveness in obtaining reactive power control, nearly sinusoidal three-phase output currents and it is compared with the traditional PV micro-inverter system. The comparison shows that the PV micro-inverter is best in more specification than the traditional PV system such as efficiency and total harmonic distortion (THD) and the system losses.</span>

REACTIVE POWER CONTROL OF THREE-PHASE MODULE INTEGRATED PV MICRO-INVERTER BASED ON BOOST CONVERTER

In recent years, photovoltaic power generation has become a creative technology. This technology uses solar energy to overcome the energy shortages in modern power systems because of increasing environmental problems in traditional power generation systems. It has irreplaceable benefits like pollution reduction and has increasingly been turned into a new path for distributing power generation applications. In traditional PV system design to produced enough DC-bus voltage from PV panels, several PV modules are connected in series connection. However, when certain modules are partially shadowed, the overall power generation of the PV panels often falls significantly, reducing its essential current generation and preventing the output current from reaching its maximum value within that panels. An AC modules strategy was suggested in this paper to solve this drawback. The PV system with an interleaved DC-DC boost converter and maximum power point tracker (MPPT) for each boost converter is used in the DC-DC converter stage. The perturbation and observation (P&O) algorithm is applied to extract sun power. In this paper, a three-phase micro-inverter voltage source inverter type (VSI) of 1000W is designed and simulated. By controlling the direct and quadrature components of inverter output currents, the active and reactive power can be injected into the grid. The system is simulated using MATLAB software and the simulation results show the validity of the suggested Micro-inverter system.

Flyback Photovoltaic Micro-Inverter with a Low Cost and Simple Digital-Analog Control Scheme

The single-stage flyback Photovoltaic (PV) micro-inverter is considered as a simple and small in size topology but requires expensive digital microcontrollers such as Field-Programmable Gate Array (FPGA) or Digital Signal Processor (DSP) to increase the system efficiency, this would increase the cost of the overall system. To solve this problem, based on a single-stage flyback structure, this paper proposed a low cost and simple analog-digital control scheme. This control scheme is implemented using a low cost ATMega microcontroller built in the Arduino Uno board and some analog operational amplifiers. First, the single-stage flyback topology is analyzed theoretically and then the design consideration is obtained. Second, a 120 W prototype was developed in the laboratory to validate the proposed control. To prove the effectiveness of this control, we compared the cost price, overall system efficiency, and THD values of the proposed results with the results obtained by the literature. So, a low system component, single power stage, cheap control scheme, and decent efficiency are achieved by the proposed system. Finally, the experimental results present that the proposed system has a maximum efficiency of 91%, with good values of the total harmonic distortion (THD) compared to the results of other authors.