Environmental Engineering Reference
In-Depth Information
1
1
+
sCZ
o
(
s
)
Since the capacitance
C
is often small,
is a low-pass filter with a unity gain for a
wide range of frequencies. As a result,
Z
o
(
s
)
v
o
≈
v
r
and
≈
Z
o
(
s
)
at low frequencies. Indeed, the role of the filter capacitor is negligible.
The impact of the the filter capacitor on the stability is discussed in Chapter 8.
7.8 Summary
The fact that the output impedance of an inverter plays an important role on the THD of the
output voltage offers an alternative to improve the quality of output voltage of an inverter.
Partially based on (Zhong 2012c; Zhong and Zeng 2011), control strategies are presented
to change the output impedance of an inverter from inductive to resistive and capacitive,
respectively. It is shown that when the output impedance is designed as capacitive, it is
possible to minimise the THD of the output voltage. The capacitance of a C-inverter can
be selected to eliminate certain harmonics. Both simulation and experimental results have
demonstrated that C-inverters are able to offer the best voltage quality among R-, L- and
C-inverters.
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