This paper proposes a switched-capacitor multilevel
inverter for high frequency AC power distribution systems. The proposed
topology produces a staircase waveform with higher number of output levels
employing fewer components compared to several existing switched capacitor
multilevel inverters in the literature. This topology is beneficial where
asymmetric DC voltage sources are available e.g. in case of renewable energy
farms based AC microgrids and modern electric vehicles. Utilizing the available
DC sources as inputs for a single inverter solves the major problem of
connecting several inverters in parallel. Additionally, the need to stack
voltage sources, like batteries or super-capacitors, in series which demand charge
equalization algorithms, are eliminated as the voltage sources employed share a common ground. The
inverter inherently solves the problem of capacitor voltage balancing as each
capacitor is charged to the value equal to one of input voltage every cycle.
State analysis, losses and the selection of capacitance are examined.
Simulation and experimental results at different distribution frequencies, power
levels and output harmonic content are provided to demonstrate the feasibility
of the proposed multilevel inverter topology.
KEYWORDS:
1.
H-bridge
2.
HFAC power
distribution
3.
High frequency
DC/AC Inverter
4.
Multilevel
inverter
5.
Selective
harmonic elimination
6.
Switched-capacitor
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1: Proposed 7 level SCMLI topology
Fig.
2: Simulation waveforms at 400 Hz including nonidealities
:
(a) output voltage and current (b) switched capacitor
voltage
and current
CONCLUSION:
A
novel SCMLI topology for HFAC PDS has been proposed in this paper. The topology
is applicable where unequal DC input sources are at disposal. Such scenarios
are common in large renewable energy farms and electric vehicle networks. It is
more convenient to employ multiple DC sources as input to a single inverter
than to employ several inverters in parallel with their respective solitary DC
input sources. This topology does not stack up the voltage sources in series
and therefore does not require voltage balancing circuits. Since the switched capacitors
employed copy the input voltage every cycle, the problem of voltage balancing
has also been eliminated. The harmonic content in the waveform is analyzed and
is found to be minimum. The proposed topology obtains higher number of voltage
levels compared to several existing topologies. This paper utilizes the
proposed topology for high frequency AC distribution. However, the same topology
can be employed for 50 Hz / 60 Hz distribution by employing a larger switched capacitor.
It is shown that the number of output voltage levels exponentially increase
with increase in the employed input voltage sources and SCs. In the hardware
results, it is shown that the 5th and 7th harmonics are minimized to very low value
of 1V each. Results at different distribution frequencies and power levels are
presented.
REFERENCES:
[1]
Patel, Mukund R.,“High-Power High-Voltage Systems”, Spacecraft Power Systems, CRC
press, 2004, ch. 22, sec. 22.7, pp. 539-543.
[2]
Luk, Patrick Chi-Kwong, and Andy Seng Yim Ng. ”High Frequency AC Power
Distribution Platforms.” Power Electronics in Smart Electrical Energy Networks.
Springer London, 2008. pp. 175-201.
[3]
Z. Ye, P. K. Jain and P. C. Sen, ”A Two-Stage Resonant Inverter With Control of
the Phase Angle and Magnitude of the Output Voltage,” in IEEE Trans. Ind.
Electron., vol. 54, no. 5, pp. 2797-2812, Oct. 2007.
[4]
J. A. Sabate, M. M. Jovanovic, F. C. Lee and R. T. Gean, ”Analysis and
design-optimization of LCC resonant inverter for high-frequency AC distributed
power system,” in IEEE Trans. Ind. Electron., vol. 42, no. 1,pp. 63-71, Feb
1995.
[5]
Status of 20 kHz Space Station Power Distribution Technology, NASA Publication,
TM 100781.
