ABSTRACT:
This paper presents a transformerless static
synchronous compensator (STATCOM) system based on multilevel H-bridge converter
with star configuration. This proposed control methods devote themselves not
only to the current loop control but also to the dc capacitor voltage control. With
regards to the current loop control, a nonlinear controller based on the
passivity-based control (PBC) theory is used in this cascaded structure STATCOM
for the first time. As to the dc capacitor voltage control, overall voltage
control is realized by adopting a proportional resonant controller. Clustered
balancing control is obtained by using an active disturbances rejection
controller. Individual balancing control is achieved by shifting the modulation
wave vertically which can be easily implemented in a field-programmable gate
array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed
and a series of verification tests are executed. The experimental results prove
that H-bridge cascaded STATCOM with the proposed control methods has excellent
dynamic performance and strong robustness. The dc capacitor voltage can be
maintained at the given value effectively.
KEYWORDS
1.
Active
disturbances rejection controller (ADRC)
2.
H-bridge
cascaded
3.
Passivity-based
control (PBC)
4.
Proportional resonant (PR) controller
5.
Shifting
modulation wave
6.
Static synchronous compensator (STATCOM).
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig
1.Configuration of the experimental system.
EXPECTED SIMULATION RESULTS:
Fig.
2. Experimental results verify the effect of PBC in steady-state process. (a)
Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.
(b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of
grid.
Fig.
3. Experimental results show the dynamic performance of STATCOM in the dynamic process.
Ch1: reactive current; Ch2: compensating current; Ch3: residual current of
grid.
Fig.
4. Experimental results in the startup process and stopping process. (a) Ch1:
reactive current; Ch2: compensating current; Ch3: residual current of grid. (b)
Ch1: reactive current; Ch2: compensating current; Ch3: residual current of
grid.
Fig.
5. Experimental waveforms for testing overall voltage control in the
startup
process.
CONCLUSION:
This
paper has analyzed the fundamentals of STATCOM based on multilevel H-bridge
converter with star configuration. And then, the actual H-bridge cascaded
STATCOM rated at 10 kV 2 MVA is constructed and the novel control methods are also
proposed in detail. The proposed methods has the following characteristics.
1)
A PBC theory-based nonlinear controller is first used in STATCOM with this
cascaded structure for the current loop control, and the viability is verified
by the experimental results.
2)
The PR controller is designed for overall voltage control and the experimental
result proves that it has better performance in terms of response time and
damping profile compared with the PI controller.
3)
The ADRC is first used in H-bridge cascaded STATCOM for clustered balancing
control and the experimental results verify that it can realize excellent
dynamic compensation for the outside disturbance.
4)
The individual balancing control method which is realized by shifting the
modulation wave vertically can be easily implemented in the FPGA.
The experimental results have confirmed that the
proposed methods are feasible and effective. In addition, the findings of this
study can be extended to the control of any multilevel voltage source
converter, especially those with H-bridge cascaded structure.
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