IMPROVING INVERTER OUTPUT CURRENT CONTROLLER UNDER UNBALANCED CONDITIONS BY USING VIRTUAL IMPEDANCE
Nowadays, three-phase inverters have been commonly used in power system, especially in renewable energy and motor drives application. In many applications, the inverter has to generate balanced sinusoidal three-phase current. In grid-tied inverter, usually the voltage grid is unbalanced. This unb...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/55213 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Nowadays, three-phase inverters have been commonly used in power system,
especially in renewable energy and motor drives application. In many applications, the
inverter has to generate balanced sinusoidal three-phase current. In grid-tied inverter,
usually the voltage grid is unbalanced. This unbalance produces unbalanced output
currents of inverter. Unbalanced three-phase currents contain positive and negative
sequence currents, that produces low frequency oscillation in DC side. The most
common method to suppress this unbalance is the dual synchronous frame control
method. This method is complicated due to the existence of sequence transformation
block. This research proposes a novel method to balance the inverter output current
under unbalanced ac side conditions. The proposed method is based on virtual
impedance concept that is inserted in series to the inverter output. The proposed virtual
impedance is an additional control algorithm that changes the inverter behavior into
the one that has a real impedance connected on it. As it is virtual, the virtual impedance
can be designed in such a way so that just the unbalanced signal is affected. Simulation
and experimental results are included to show the effectiveness of the proposed
method. |
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