Performance Improvement of Weak Grid-connected Wind Energy System Using FLSRF Controlled DSTATCOM

 Abstract

Wind Energy (WE) is emerging as a Green and Clean Energy source. The power quality (PQ) significantly deteriorates when WE sources are connected to the weak ac grid. This is due to the variable wind speed, the impedance of weak grids and non-linear loads. This paper proposes a methodology to improve the PQ in the weak grid with WE penetration using additional distribution static compensator (DSTATCOM). Fuzzy Logic (FL) controller is implemented in the conventional Synchronous Reference Frame (SRF) scheme to minimize the oscillations in the voltage signals. Also, a feed-forward block of the WE source is incorporated in the FLSRF control scheme for adapting changes associated with the wind speed. The proposed control scheme accommodates the changes related to the grid’s strength, wind speed, load currents and DC-link voltage dynamics to estimate the switching signals for the DSTATCOM. The MATLAB simulation and experimental studies established the effectiveness of the proposed method for enhancing the PQ performance of weak grid-connected WE sources in the presence of non-linear loads.

Index Terms—DSTATCOM, Fuzzy Logic, Synchronous Reference Frame, SCR, PQ, Weak Grid, Wind Energy Source.

Block Diagram:

Fig. 1. The system configuration

Expected Simulation Results:

Fig. 2. Response of FLSRF controlled DSTATCOM under rated 15m/s wind

speed and presence of NL loads.

Fig. 3. Updation of Wind-feed forward term under unbalanced NL load.

CONCLUSION

The FLSRF controlled DSTATCOM has been implemented successfully for mitigating the challenges associated with WE penetration in the remotely located grid in the presence of unbalanced linear and non-linear loads. The proposed method has been successfully examined for different remote location loads for a grid with an SCR of 2.74 under the rated (15 m/s) and minimum (7.5 m/s) wind speed. The FLSRF control provides excellent control over the unpredictability and variability existing in the weak system. The incorporated additional feedforward block performs well for adapting changes in the wind speed. The proposed control also increases DSTATCOM reactive power capability by managing the reactive power flow to maintain the voltage within stability range and active power at POC. Hence, the size of DSTATCOM has reduced to 58% (reduction in size by 42%). The proposed FLSRF controlled DSTATCOM method maintains voltage stability, stable terminal and DC-link voltage, load balancing, power factor, grid current and voltage harmonics as per the IEEE- 519-2014 and EN-50160 standards.

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