ABSTRACT:
In
this paper, modeling, simulation and experimental study of a 10kW three-phase
grid connected inverter are presented. The mathematical model of the system is
derived, and characteristic curves of the system are obtained in MATLAB with
m-file for various switching frequencies, dc-link voltages and filter
inductance values. The curves are used for parameter selection of three-phase
grid connected inverter design. The parameters of the system are selected from
these curves, and the system is simulated in Simulink. Modeling and simulation
results are verified with experimental results at 10kW for steady state
response, at 5kW for dynamic response and at −3.6 kVAr for reactive power. The
inverter is controlled with Space Vector Pulse Width Modulation technique in
d-q reference frame, and dSPACE DS1103 controller board is used in the
experimental study. Grid current total harmonic distortion value and efficiency are measured 3.59% and 97.6%,
respectively.
KEYWORDS:
1. Grid
Connected Inverter
2. Inverter
Modeling
3. Space
Vector Pulse Width Modulation
4. Total
Harmonic Distortion
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Block diagram of the grid connected inverter.
EXPECTED SIMULATION RESULTS:
Fig.
2. THD variation of the grid current for Vdc = 650 V.
Fig.
3. THD variation of the grid current for fsw = 3 kHz.
Fig.
4. THD variation of the grid current for fsw = 9 kHz.
Fig.
5. Three-phase grid currents and voltage for fsw = 3 kHz.
Fig.
6 d-q components of the grid current for fsw = 3 kHz
Fig.
7. Three-phase grid currents and voltage for fsw = 9 kHz
Fig.
8. d-q components of the grid current for fsw = 9 kHz.
Fig.
9. d-q components of grid current.
CONCLUSION:
In
this study, performance of a 10kW three-phase grid connected inverter is
investigated for various filter inductance values, DC-link voltages and
switching frequencies. The system is modeled in m-file, thus characteristic
curves of the inverter are obtained for different parameters. The THD values of
grid current for 3 kHz and 9 kHz with 650V DC-link voltage are 10.22%and 3.41%.
For verification of the modeling results, the system is simulated in Simulink. The
control algorithm is implemented in Embedded Matlab Function in the simulation.
The results are compared at 3 kHz and 9 kHz switching frequency, and modeling
results are verified with simulation results that are 10.22% are 3.44%. In
order to verify the modeling and simulation results, a laboratory prototype
that is controlled by dSPACE DS1103 control board is realized. In the
experimental study, THD values are measured as 10.68 and 3.59%. Furthermore,
dynamic response and reactive power generation capability of the inverter are
presented. The experimental results verify the modeling and simulation results.
This verification shows that the system can be designed for various system and
control parameters using the design curves. The study is realized for 10kW
power but it is possible to obtain the characteristic curves for differen power
values. According to results, the switching frequency or filter inductance
value should be high to meet THD limit. Furthermore, efficiency is another
important performance indicator. The efficiency at rated power and the european
efficiency of the inverter is 97.6% and 97.2%
at 9 kHz.
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