ABSTRACT:
A three-phase single-stage solar energy conversion system
(SECS) integrated into a weak distribution network is presented. The grid
integration and maximum power point operation of the photovoltaic (PV) array
are achieved by a voltage source converter. The SECS is capable of feeding
distortion-free and balanced grid currents with power factor correction, even
at adverse grid side, PV array side, and load side operating conditions. The
integration of SECS into the weak grid having distorted, unbalanced, and
varying grid voltages is achieved while maintaining the power quality. The dc
offset introduced in the sensed grid voltages is also effectively eliminated.
For swift system response to changes in load currents, their fundamental
weights are swiftly extracted. In the absence of solar irradiance, the power is
imported from the utility to supply the local loads, and the system continues
to execute its power quality improvement functions. In case of loss of PV power
or large voltage deviations, the dc-link voltage is adaptively varied according
to the grid voltage changes, increasing system reliability, and reducing
operating losses. The efficacy of the SECS is validated through test results at
different operating scenarios.
KEYWORDS:
1.
Maximum power
point (MPP) tracking
2.
Power quality
3.
Single-stage
photovoltaic (PV) system
4.
Weak grid
integration
SOFTWARE: MATLAB/SIMULINK
SCHEMATIC DIAGRAM:
Fig. 1. System configuration.
EXPECTED SIMULATION RESULTS:
Fig.2.
Performance at grid voltages distortion while (a), (b) SECS is out of operation
while (c), (d) SECS is in operation.
Fig.
3. DC offset elimination performance of GVP stage.
Fig.
4. Performance at grid voltages unbalance while (a), (b) SECS is OFF while (c),
(d) SECS is in operation.
Fig.
5. Dynamic response of the system. (a) Irradiance reduction. (b) Irradiance increment.
Fig.
6. SECS response at rapid changeover. (a), (c) PV to DSTATCOM operation. (b),
(d) DSTATCOM to PV operation.
CONCLUSION:
The
performance of a single-stage PV system with PV array power delivery directly
at the dc-link capacitor of VSC, equipped to operate in weak grid conditions,
with resilience against the grid side, PV array side, and load side
disturbances, is demonstrated. The presented GVP stage has successfully eliminated
the adverse effects of distorted, unbalanced, and varying grid voltages from
the grid currents. Furthermore, the dc offset rejection from the acquired grid
voltages has been validated. The SECS has also demonstrated the features of
grid currents balancing, power factor correction, and harmonics reduction to
meet the IEEE 519 standard, at various operating conditions. A DNLMS algorithm
has been modified and applied for rapid extraction of the fundamental weights
from the load currents. Its accuracy and response speed under sudden load disturbances
have been found satisfactory. The MPP tracking has been successfully carried
out at various irradiance levels, using an INC-based technique, which has
provided the reference value formaintaining the dc-link voltage to the PV array
MPP. With the change in the operating conditions, the SECS has demonstrated the
smooth transfer of the dc-link voltage regulation from the INC technique to an
adaptive strategy, which has generated the reference value according to the
grid voltage level. This enabled the optimum operation of the SECS as a
DSTATCOM in low-irradiance periods, enhancing the system utilization. The grid
currents are demonstrated to vary swiftly at PV power fluctuations and the grid
voltage deviations due to effective use of a PVFF term, and hence, dc-link
voltage is not disturbed from MPP. The system robustness at weak grid
conditions, PV side, and load side fluctuations has been validated by test
results.
REFERENCES:
[1]
A. J. Waldau, I. Kougias, N. Taylor, and C. Thiel, “How photovoltaics can
contribute to GHG emission reductions of 55% in the EU by 2030,” Renewable
Sust. Energy Rev., vol. 126, Jul. 2020, Art. no. 109836.
[2]
A. A. Almehizia, H. M. K. Al-Masri, and M. Ehsani, “Feasibility study of sustainable
energy sources in a fossil fuel rich country,” IEEE Trans. Ind. Appl.,
vol. 55, no. 5, pp. 4433–4440, Sep./Oct. 2019.
[3]
O. M. Akeyo, V. Rallabandi, N. Jewell, and D. M. Ionel, “The design and
analysis of large solar PV farm configurations with DC-Connected battery
systems,” IEEE Trans. Ind. Appl., vol. 56, no. 3, pp. 2903–2912, May/Jun.
2020.
[4]
F.Hafiz, M. A.Awal, A. R. d. Queiroz, and I. Husain, “Real-time stochastic optimization
of energy storage management using deep learning-based forecasts for
residential PV applications,” IEEE Trans. Ind. Appl., vol. 56, no. 3,
pp. 2216–2226, May/Jun. 2020.
[5]
M. A.Mahmud, T. K. Roy, S. Saha,M. E. Haque, and H. R. Pota, “Robust nonlinear
adaptive feedback linearizing decentralized controller design for islanded DC
microgrids,” IEEE Trans. Ind. Appl., vol. 55, no. 5, pp. 5343–5352,
Sep./Oct. 2019.
