Analysis of Dynamic Voltage Stability on The Penetration of Adama Ii Wind Farm in Ethiopian Grid
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Date
2017-09
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Addis Ababa University
Abstract
Wind energy is one of the most available and exploitable forms of renewable energy. The importance
of wind farm penetration is that it can reduce or replace the existing conventional generators. The
integration of wind farm to the existing grid introduces new challenges regarding power system
which need to be addressed. Among power system stability concerns, voltage stability due to the
integration of wind farms is the one that considerably affect the grid.
By now, Ethiopia has wind energy sources with installed capacity of 324 MW that consist of three
wind farms. Among them the largest operational wind farm is Adama II, which has been considered
in this thesis, uses Doubly Fed Induction Generator Wind Turbine (DFIG WT).
In this study, Adama II wind farm is aggregated from 102 wind turbines to single turbine
representation. Thus, the dynamic model of DFIG WT has been developed and verified using load
flow analysis. And the simplified grid model has been developed also. This model is used to analyze
the dynamic voltage stability as regards the penetration of Adama II wind farm in Ethiopian existing
national grid. The modeling, simulation studies and analysis has been done using Power System
Simulator for Engineering (PSS /E) software.
The compliance of the grid code behavior of the wind farm has been investigated based on the
detailed analysis of the contingency scenario of that a bolted symmetrical three-phase fault applied at
the point of common coupling (PCC) for 150 ms. After fault clearance, the voltage recovers to 1.032
p.u at the PCC and within 0.6 second following the fault clearance other buses restored to the super
grid voltage. The active power output and the reactive power restored to 0.9 of the level available
immediately before the fault. The results show that Adama II wind farm integrated to the Ethiopian
power grid fulfills the wind grid code requirements in response to the short circuit event. The thesis
also analyzes the voltage control capability of Adama II wind farm voltage controller on the power
system dynamic voltage stability. To study its influence, wind generator equipped with /without
voltage controller is considered. The voltage at the PCC gradually recovers to 1.038 p.u and 1.059 p.u
with and without voltage controller respectively after the clearance of short circuit fault .It is
observed that the voltage with out voltage control strategy exceeds the normal limit of 1.05 p.u.
Finally, the analysis of wind farm performance in weak grid has been done . It can be observed that
the voltage on the far end substation bus bar is 0.934 p.u and 1.0639 p.u with low and maximum load
respectively. In this case, the results show that voltages are violated the standard voltage range.
The simulation results depict that, the contribution of voltage controller is visible since it enhances
the wind farm capability during the fault as compared with no voltage control is enabled. Therefore,
the wind farm is able to fulfill the control characteristic of the controller that can improve power
system dynamic behavior such as voltage stability as spelt out in international grid codes. And also it
is recommended that EEP has to implement and equipped with voltage controller for all wind farms.
Description
Keywords
wind farm, DFIG, dynamic voltage stability, aggregated wind farm, PSS/E, wind farm penetration, contingency scenario, national grid, PCC, grid code, voltage control