C4-4

A New Five-Level CSI for Grid Connected Power Conditioner‫ ۔‬Suroso*, Toshihiko Noguchi (Shizuoka University)
1. Introduction
This paper proposes an application of a new five-level
current-source inverter (CSI) as a grid connected power
conditioner. The proposed five-level CSI is composed of anH-bridge inverter connected with a single DC current module
circuit to generate the intermediate level currents of the fivecurrent waveform. The simulation results show that the proposed
five-level CSI works properly injecting a sinusoidal current into
the power grid with a high power factor operation.

2. System Configuration
Fig. 1 presents a circuit configuration of the proposed
five-level CSI connected to the power grid. A low pass filter (Cfand Lf) is used to filter the harmonic components, e.g. switchingharmonics, of the five-level PWM current. The DC current
sources are generated using chopper circuits with only a single
DC power source. The chopper works as a regulated DC current
source for the inverter and the DC current module. The main
inverter is a three-level H-bridge CSI. The DC current moduleconnected in parallel with the main H-bridge CSI to obtain ahigher level number of output current. The DC current module iscomposed by a current source, a unidirectional switch and aconnecting diode. This circuit functions to synthesize theintermediate current levels of the five-level output current.
The chopper simply consists of a controlled power switches(Qc1, Qc2), smoothing inductors (L1, L2) and a free wheeling
diodes (DF). The chopper switch functions to regulate the DC
current flowing through the smoothing inductor, and to reduce
the smoothing inductor size. It should be noted that only a single
DC voltage source (Vin) is connected to the choppers to obtainthe multiple DC current-sources. The inverter works convertingthe DC power into AC power that will be injected into the power
grid. Proportional integral (PI) regulators are independently
applied to regulate the DC currents flowing through thesmoothing inductors. A carrier based sinusoidal modulation
technique is applied to obtain a PWM output current waveform.

Fig. 1 Proposed five-level CSI with grid connection

3. Simulation Results
A proposed five-level CSI operated as a grid connected power
conditioner is tested through a computer simulation using PSIM
software. Fig. 2 shows the waveforms of a five-level PWM
output current (I5level), the current injected into the grid (Iinv), thegrid voltage (VGrid) and the smoothing inductor current
waveforms (IL1, IL2) of the proposed five-level CSI. The figure
also shows the transient waveforms of five-level and inverter
current from 4 A to 8 A. It can be seen that the injected current is
an excellent sinusoidal waveform with small distortion, and theinverter works injecting a sinusoidal current with a unity power
factor operation.

Fig. 2 Simulation result of five-level PWM current, inverter’s current,
grid voltage, and smoothing inductor current waveforms

4. Conclusion
A new five-level CSI working as a grid connected power
conditioner has been proposed. The simulation results show thatthe proposed CSI worked properly injecting a sinusoidal current
to the power grid with a high power factor operation.
(1)(2)

References
Suroso, and T. Noguchi: Journal of Energy Conversion andManagement, Elsevier, Vol. 51, issue 7, p.p 1491-1499, 2010
Suroso, and T. Noguchi: Proceeding of IEEE International
Conference on Power Electronics (IPEC), Hokkaido, Japan, 2010.

平成22年度 電気関係学会東海支部連合大会 （2010年8月30日～31日 於中部大学）