1. Adama Science and Technology University Department of
Electrical Power and Control Engineering
Scientific Research Methods and Presentation
Title: Direct power control strategy based variable speed pumped
storage system for the reduction of the wind power fluctuation
impact on the grid stability
By: Metasebia Fisseha
2/12/2023
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3. Energy consumption
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The amount of energy
produced globally is higher than
it was previously, there is
currently a shortage of energy.
people need fossil fuels (such
as oil, coal, and natural gas) to
carry out their daily tasks.
Fig1. environment pollution
4. Cont.…
Due to increasing environmental concerns, wind
power generation has undergone rapid growth.
Wind energy production has many advantages; it is
ecofriendly,
sustainable,
space efficient,
incredible domestic potential,
has low operational cost,
revitalizing to rural economies, etc.
However, the major drawback of wind power is its
intermittency and stochastic in nature over time.
As a result, significant wind power fluctuations can be
observed
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6. Cont.…
The aim of control wind turbine in three region : cut
in speed, rated speed and cut out speed to protect
equipment and to extract maximum power.
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Fig3. power verses wind speed
7. Cont.…
The following assumptions are taken:
The power losses in the converters are neglected.
The switching dynamics are also neglected because the
pulse width modulation frequency in three-level VSC
NPC is much greater than the system frequency
Thus, the model of the VSC NPC is developed as in
𝑢𝑑𝑞𝑟 =𝑚𝑑𝑞𝑟
𝑣𝑑𝑐
2
(1)
𝑢𝑑𝑞𝑔 =𝑚𝑑𝑞𝑔
𝑣𝑑𝑐
2
(2)
where udqr, udqg and mdqr, mdqg are converter
injected voltages and modulated signals respectively in
the rotor and grid side converters.
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8. Cont.….
• A direct power control (DPC) strategy is employed
to have fast response and lets the control system
compensate the wind power fluctuations directly
and effectively.
• An external set point, Pset which is the input to the
power control system, The set point depends on the
VSPS capacity and the situation of the power grid.
• Equations of active power and reactive power :
• 𝑝𝑠 = 1.5𝑣𝑠
𝑙𝑚
𝑙𝑠
𝑖𝑞𝑟 (4)
• 𝑄𝑠 = 1.5𝑣𝑠
Φ𝑠
𝑙𝑠
−
𝑙𝑚
𝑙𝑠
𝑖𝑑𝑟 (5)
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9. Cont.….
Fig4. The current control structure of the VSC NPC1
mathematical equations the rotor dynamics model
The PI control of Ki(s)
is defined by:
𝐾𝑖 𝑠 =
𝑃𝑖𝑠+𝐼𝑖
𝑆
(6)
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𝑣𝑞𝑟 = 𝑅𝑟𝑖𝑞𝑟 + 𝐿∗
𝑟
𝑑𝑖𝑞𝑟
𝑑𝑡
+ ω𝑠 − ω𝑟 𝐿𝑟𝑖𝑑𝑟 + 𝐿𝑚𝑖𝑑𝑠 (7)
𝑣𝑑𝑟 = 𝑅𝑟𝑖𝑑𝑟 + 𝐿∗
𝑟
𝑑𝑖𝑑𝑟
𝑑𝑡
-(ω𝑠 − ω𝑟) 𝐿𝑟𝑖𝑞𝑟 + 𝐿𝑚𝑖𝑞𝑠 (8)
10. Cont.….
Fig5. The active power control
structure of the VSC NPC1
Considering the power
command Δpwind to the VSPS
power control unit, it is
computed by
Δ𝑃𝑤𝑖𝑛𝑑 = 𝑃𝑤𝑖𝑛𝑑 − 𝑃𝑠𝑒𝑡
where Pwind is the wind farm
power measured, and Pset an
assumed forecasted power
output. This Pwind is added to
the power command Pop_vsps
to feed the fluctuated wind
power to the control loop for
regulating.
The models and details of the
reactive power control in both
rotor side and grid side
converters and DC voltage
control in the grid side
converter. 10
11. Cont.…
• A grid frequency response is observed with the
deviations of ±0.04Hz while the active power is
regulated to track the wind power fluctuation.
Fig6. grid frequency response associated with
control of the VSPS active power
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12. Cont.…
• when the reference reactive power Q_ref=0pu, the
controller tracks its reference value.
• To maintain the AC voltage at its nominal value of 18 kV,
Thus, 22 MVar is required to be generated and
equivalently Q_ref=0.067pu is suppled at time t=25sec.
Fig7. AC voltage response associated with control of the
VSPS reactive power
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13. Cont.…
CONCLUSION
DPC based VSPS system for the reduction of
wind power fluctuation impact on the grid
stability.
Mathematical models based on phasor model
technique is presented.
The results show that the proposed control
strategy for the VSPS system achieves well-
regulated grid frequency and AC voltage with
small errors of acceptable ranges in the power grid
system in spite of the wind power fluctuations.
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