Weak Grid Integration of a Single-Stage Solar Energy Conversion System With Power Quality Improvement Features Under Varied Operating Conditions Final Year Academic Electrical Projects

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:

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