A Low Cost Dynamic Voltage Stabilization Scheme for Standalone Wind Induction Generator System

1. A Low Cost Dynamic Voltage Stabilization Scheme for Standalone Wind Induction Generator System By Dr.A.M.Sharaf, Senior member IEEE; and Liang Zhao, Student

2. Outline • 1.Introduction • 2.Standalone Wind Energy System • 3.Dynamic Series Switched Capacitor Compensation including two parts: Digital Simulation Models and Dynamic Simulation Results • 4.Conclusions • 5.Future Study • Reference

3. 1. Introduction • Wind energy has become one of the most significant, alternative energy resources. • Most wind turbines(15-200kw) use the three phase asynchronous induction generator for its low lost, reliable and less maintenance. • However, the voltage stability of a wind driven induction generator system is fully dependent on wind gusting conditions and electrical load changes[1-3]. • New interface technology is needed such as DSSC and other compensation scheme[1-3].

4. DSSC is a low cost dynamic series switched capacitor (DSSC) interface compensation scheme. Capacitance in parallel or series of the DSSC scheme are interfaced with the output feeder lines. DSSC scheme can be used to improve the induction generator voltage stability and ensure dynamic voltage stabilization under varying wind and load conditions, thus prevent loss of severe generator bus voltage excursions. IntroductionWhat is DSSC?

5. 2. Standalone Wind Energy System Figure 1 shows Standalone Wind Energy Conversion Scheme Diagram with Hybrid Load and Dynamic Series Switched Capacitor Compensations

6. 2. Standalone Wind Energy System Figure 2 shows Low Cost Dynamic Series Switched Capacitor (DSSC) Stabilization Scheme using Gate Turn off GTO switching Device

7. 2. Standalone Wind Energy System Figure 3 shows the Hybrid Electrical Load

8. 3. Dynamic Series Switched Capacitor Compensation3.1 Digital Simulation Models • A sample test standalone wind induction generator system (WECS) is modeled using the Matlab/ Simulink/ SimPower Blockset software environment.

9. 3. Dynamic Series Switched Capacitor Compensation3.1 Digital Simulation Models Figure 4 shows the Unified Systems Matlab/Simulink Functional Model

10. 3. Dynamic Series Switched Capacitor Compensation3.1 Digital Simulation Models Figure 5 shows Tri-loop Error Driven PID Controlled PWM Switching Scheme

11. 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Linear and non-linear load excursions Figure 6 in next slide depicts the digital simulation dynamic response to both in linear and nonlinear load excursion. • From time interval 0.1s to 0.3s, we applied 50% (100kVA) linear load; from 0.4s-0.6s, we applied 60% (120kVA) non-linear load. • So the DSSC can stabilize for both linear and nonlinear load excursions and ensure the generator bus stabilization

12. Without DSSC Compensation With DSSC Compensation 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Figure 6

13. 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Under inrush induction motor load excursion Figure 7 in the next slide shows the dynamic simulation response to the induction motor load excursions. • From time 0.2s to0.4s, we applied about 20% (20kVA) induction motor load. • From the figure we can see that DSSC did not compensate for this inrush motor load excursions adequately.

14. Without DSSC Compensation With DSSC Compensation 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Figure 7

15. 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Under wind excursion • Figure 8 in the next slide shows the dynamic simulation response to wind excursions • From 0.3s-0.6s, the wind speed was decreased to 6m/s from initial value 10m/s. • From figure 8 we can see that DSSC did compensate wind excursion, the voltage at generate bus keeps 1.0pu.

16. Without DSSC Compensation With DSSC Compensation 3. Dynamic Series Switched Capacitor Compensation3.2 Dynamic Simulation Results Figure 8

17. 4. Conclusions • The low cost DSSC compensation scheme is very effective for the voltage stabilization under linear, non-liner passive load excursions as well as wind speed excursions • But it can not compensate adequately for large inrush dynamic excursions such as induction motor. • The proposed low cost DSSC voltage compensation scheme is only suitable for isolated wind energy conversion systems feeding linear and non-linear passive type loads

18. 5. Future Study • Another new compensation scheme that can compensate for a large inrush induction motor excursion will be studied in my future research. • That scheme will be very effective for bus voltage stabilization under linear, non-liner, inrush motor loadexcursions and wind excursions.

19. Reference • [1]. K.Natarajan, A.M Sharaf, S.Sivakumarand and S.Nagnarhan, “Modeling and Control Design for Wind Energy Conversion Scheme using Self-Excited Induction Generator”, IEEE Trans. On E.C., Vol.2, pp.506-512, Sept.1987. • [2]. S.P.Singh, Bhim Singh and M.P.Jain, “Performance Characteristic and Optimum Utilization of a Cage Machine as a Capacitor excited Induction Generator”, IEEE Trans. On E.C., Vol. 5, No.4, pp.679-685, Dec.1990 • [3]. A.Gastli, M.akherraz, M. Gammal, “Matlab/Simulink/ANN Based Modeling and Simulation of A Stand-Alone Self-Excited Induction Generator”, Proc. of the International Conference on Communication, Computer and Power, ICCCP’98, Dec.7-10 1998, Muscat, Sultanate of Oman, pp.93-98