Environmental Engineering Reference
In-Depth Information
21.6 Summary
Based on (Zhong 2012a, 2012b), the harmonics in an inverter system is treated individually
and a harmonic droop control strategy is presented to provide the right harmonic reference
voltage to cancel the harmonic voltage dropped on the output impedance of the inverter, which
reduces the harmonic components in the output voltage. The harmonic droop controller, which
is developed after investigating the basic principles of delivering power to a constant current
source (sink), does not depend on the type of the impedance. This avoids the need for checking
the type for each harmonic frequency, which can be very difficult in practice. The harmonic
droop control strategy also clarifies that the power sharing of inverters should be done at
individual harmonic frequencies, which avoids the difficulty in defining the reactive power
for different frequencies together. The strategy is able to significantly reduce the harmonic
components in the output voltage while accurately sharing the power at the fundamental
frequency. Simulation and experimental results have shown that the harmonic droop controller
is able to considerably improve the THD of the output voltage.
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