5KW 3-Phase Grid Tied Solar Inverter
3
1
Introduction
1.1
Overview
This solar inverter is a power conditioning equipment that converts DC solar electric (photovolatic
or PV) power into ac utility-grade electricity that can be sold to local power company. The inverter
performs Maximum Power Point Tracking (MPPT) and extracts out the maximum power possible
from the solar PV string connected at its input.
Figure 1: A typical roof-top solar PV system
This inverter can only be used with a solar PV string (PV modules connected in series) with open
circuit dc voltage less than 1000 V DC. This inverter
CANNOT
be used with any other regular dc
voltage source. Note that the present inverter uses zero residual current transformerless topology due
to which any sort of PV modules (Mono-crystalline PV, Poly-Crystalline PV, thin film PV) can be
connected to the inverter. A typical roof-top solar PV system is shown in Figure 1 on page 3. In
Distribution Box, typically a separate DC circuit breaker is installed between inverter and PV string
and a separate AC circuit breaker is typically installed between inverter and grid utility.
1.2
Factors Affecting The Performance of Inverter
There are a lot of factors that can influence the performance of this inverter.
1.2.1
Rating for PV modules
PV modules are rated at ideal factory conditions, such as specified illumination (1000
W/m
2
), spec-
trum of light and temperature (25
0
C
/ 77
0
F
). This is called the STC (Standard Test Condition)
rating and is the figure that appears on the specification label of PV module. Generally speaking,
only around 60% to 70% of its peak STC-rated output will be produced from the PV modules due to
unpredicted environmental factors.
1.2.2
Temperature and Power Reduction:
Environment temperature affects the power output of PV modules. Higher the temperature, lower
the power output of PV module. Comparing the pole-mounted PV array, roof-mounted PV module
array generates less power due to less air circulation and and excessive heat from the roof top.
©
Pyramid Electronics