ACTIVE FILTERING AND STABILITY ANALYSIS FOR HYBRID RENWEABLE

Abstract

A nanogrid is a stand alone system that uses
renewable and non-renewable sources to supply power to
local loads. A nanogrid is similar to the microgrid concept
[1], but smaller in size than a microgrid. It has a capacity
in the order of 2-20 kW. However, there are some
considerations to improve the system response and extend
the functionality towards harmonics mitigation.
The performance of the nanogrid is not totally satisfactory
as large over shoot may occur in the output voltage, and
current disturbances may occur at load side.
A power electronics system can become unstable when the
source interface converters are connected to load interface
converters rather than resistive loads. In this paper, a
passive filter is designed to damp out the over shoot of the
output voltage and to suppress the current disturbances
from the load side. Also the system still has low-order
harmonics in the load voltage at frequencies that are lower
than the resonance frequency of the filter. To solve this
problem, active filter is used to inject the same amplitude of
harmonic voltages with an opposite sign to cancel out the
grid harmonics.