ABSTRACT:
This document
presents a Proportional + Resonant (PR) controller design for regulating the
active and reactive power output of a three-phase AC Micro-Grid inverter
system. The system employs a Voltage Sourced Inverter (VSI). The VSI is
configured to operate as a current source through an interface L-filter. The
power is controlled indirectly by controlling the inverter’s output current.
The stationary reference frame strategy is adopted for the design of the PR
controller. A model of a grid connected AC inverter and a detailed design of
the inverter’s PR based control scheme are presented. The control scheme is
developed and simulated in MATLAB/Simulink software environment. The control
algorithm code is generated for a target device. Using Processor In-the Loop
(PIL) simulation, functional equivalence testing is performed between the
simulated control algorithm and the compiled algorithm code on the target
device. Results in both normal and PIL simulations are discussed from the
viewpoint of steady state and dynamic performance of the controller.
KEYWORDS:
1. Stationary
Reference Frame
2. Processor
In-the Loop
3. Feedback
Control
4. Voltage
Sourced Inverter
5. Alpha-Beta
transformation
6. Proportional
Resonant controller
SOFTWARE: MATLAB/SIMULINK
SCHEMATIC DIAGRAM:
Figure 1 Schematic
diagram for a three-phase grid connected VSI
Figure.2 Three-Phase
grid voltages (Vabc)
Figure 3 Normal
simulation α-axis current tracking due to a step change in Pref at
t = 0.5s
Figure 4 Normal simulation
system’s response tracking active power reference signal due to a step change
in Pref at t = 0.5s
Figure 5 PIL
simulation α-axis current tracking due to a step change in Pref at
t = 0.5s
Figure 6 PIL simulation system’s
response tracking active power reference signal due to a step change in Pref
at t = 0.5s
CONCLUSION:
This
paper has presented the effectiveness of using the Proportional Resonant (PR)
control strategy to control active and/or reactive power transfer between the Micro-Grid
and the transmission grid system. The PR controller tracks stationary frame
reference currents calculated from the active (PC(t)) and reactive (QC(t))
PI controller actuating power outputs using d-q frame power
equations. Consequently this improves the performance of the control loop as
opposed to reference currents calculated directly from αβ frame power
equations. The PR controller tracks reference currents with a very small
steady-state error and reduced harmonic distortion. Model development and
simulations were done using the MATLAB/Simulink software environment.
Functional equivalence testing was performed between the simulated control
algorithm and the compiled algorithm code on the real hardware target device.
Same results were obtained for both normal and PIL simulation modes.
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