Grid Connection and Synchronization Inverter Control for Solar Power System Using Synchronously Rotating Reference Frame
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Date
2019-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Grid connected solar PV systems are increasing dramatically from year to year due to the
increase of global interest in renewable energy sources and growth in energy demand. In thesis
work, the designing and modeling of grid connected PV system using synchronously rotating
reference frame (SRRF) has been carried out. In this thesis, the important points and literature
regarding the elements in a PV system, an inverter and grid connection system have been studied
and reviewed.
The photovoltaic model is used to simulate actual PV array characteristics, and an MPPT method
using incremental conductance method is proposed in order to control the DC-DC boost
converter to extract the maximum power from the PV array. The inverter used in this thesis work
is three-phase two-level voltage source inverter (VSI) which is controlled using synchronously dq
reference
frame
with
space
vector
pulse
width
modulation
(SVPWM).
The
control
structure
for
the
inverter is designed by synchronous reference frame with phase locked loop (PLL). The
phase locked loop is used to acquire the available necessary information of grid voltage. An
LCL-filter is used to interconnect the output of inverter to the grid and used to attenuate the total
harmonics distortion (THD) present in the output current and voltage of the inverter. The system
model is developed using MATLAB/SIMULINK environment.
The efficiency of the overall system is around 97% which is improved more than the previous
related work whose efficiency is around 96%. The total harmonic distortion of the grid current is
0.88% which is less than the previous work that is 1.42%. For resistive load change, the THD of
the grid current and inverter current are 0.88%, 0.91% and 0.93%, and 0.86%, 0.87% and 0.87%
for a load of 1.5kW, 2.5kW and 3.5kW respectively. For a nonlinear load change, the THD of
the grid current and inverter current are 0.61%, 0.51% and 0.50%, and 0.12%, 0.12% and 0.12%
for a load of 100Ω, 125Ω and 320Ω and C = 3000µF respectively.
Description
Keywords
DC-DC Converter, MPPT controller, nverter control scheme, Grid synchronization, Phase locked loop (PLL), Grid connected solar PV system