young researchers symposium presentation

1. Combined Centralized and Local Voltage
Control in Active Distribution Networks
May 12, 2016
Young Researchers Symposium 2016
Hamid Soleimani Bidgoli (University of Liège)

2. Centralized controller: inputs and outputs
real-time
centralized
controller
𝑃, 𝑄 , 𝑉
V
(voltage set-point of LTC)
Measurements
(refreshed every ~ 10 s)
Corrections
(updated every ~ 10 s)
𝑃, 𝑄 , 𝑉
𝑃,𝑄,𝑉
𝑄 𝑐𝑜𝑟
2

3. Local controller-reactive power control
𝑄 𝑔
3

4. Why not two-level (centralized-local) controller?
 Fast response after any limit violation by local controller (lower
level);
 Wide coordination of the DGUs by centralized controller (upper
level), in order to adjust and complement the actions taken locally;
improve network reliability, since the local
controllers still act in case of communication
problems between the DGUs and the
centralized controller.
4

5. Two-level (centralized-local) controller
𝑄 𝑔
5

6. Voltage control architectures
Centralized
real-time
controller
Necessary
adjustments
Q
V
LOCAL
CONTROLLER
Q
V
LOCAL
CONTROLLER
Q
V
LOCAL
CONTROLLER
6

7. 𝑚𝑖𝑛
𝑖=0
𝑁 𝑐−1
𝑸 𝑔 𝑘 + 𝑖 − 𝑸 𝑚𝑒𝑎𝑠(𝑘)
𝑾 𝑄
2
+ 𝜺 𝑺
2
subject to :
for 𝑖 = 1, … , 𝑁𝑝 ∶
𝑽 𝑘 + 𝑖 = 𝑽 𝑘 + 𝑖 − 1 + 𝑺 𝑉 𝑸 𝑔 𝑘 + 𝑖 − 1 − 𝑸 𝑔 𝑘 + 𝑖 − 2
−𝜀1 𝟏 +𝑽 𝑚𝑖𝑛
𝑘 + 𝑖 ≤ 𝑽 𝑘 + 𝑖 ≤ 𝑽 𝑚𝑎𝑥
𝑘 + 𝑖 + 𝜀2 𝟏
for 𝑖 = 1, … , 𝑁𝑐 ∶
𝑸 𝑔
𝑚𝑖𝑛 ≤ 𝑸 𝑔 𝑘 + 𝑖 ≤ 𝑸 𝑔
𝑚𝑎𝑥
∆𝑸 𝑔
𝑚𝑖𝑛≤ 𝑸 𝑔 𝑘 + 𝑖 − 𝑸 𝑔 𝑘 + 𝑖 − 1 ≤ ∆𝑸 𝑔
𝑚𝑎𝑥
𝜺 ≥ 0
Formulation of upper-level Model Predictive Control
𝑸 𝑐𝑜𝑟, 𝜺
7

8. Test system and control strategy
 22 DG units controlled
 controls adjusted every 10 s
 Nc = 3
 Np = 3
8

9. Simulation results-local control only
𝑉 𝑚𝑖𝑛
Voltages
Output reactive power
5% voltage drop on the HV
side of the transformer
9

10. Simulation results- both control levels acting
Voltages
Output reactive power
5% voltage drop on the HV
side of the transformer
10
𝑉 𝑚𝑖𝑛

11. Conclusion
 Depending on the DG technical limitations and the regulatory policies, some/all
of DG units can be equipped with the local controller.
 At the lower level, DGU output reactive powers are locally controlled according
to a piecewise linear Q(V) characteristic.
.
This local control provides a fast response to disturbances.
 At the higher (centralized) control level, model predictive control is used to
compute and send reactive power corrections to the local controllers.
.
The Q(V) characteristics of local controllers are updated, steering
them smoothly to produce the desired reactive powers.
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