A. AGUSTONI, M. BRENNA, R. FARANDA, E. TIRONI Dipartimento di Elettrotecnica

Politecnico di MilanoDipartimento di Elettrotecnica

Clemson, March 13, 2002

Distributed Generation Control Distributed Generation Control Methodologies and Network Methodologies and Network

Reconfiguration: Reconfiguration: Effects on Voltage ProfileEffects on Voltage Profile

A. AGUSTONI, M. BRENNA, R. FARANDA, E. TIRONIDipartimento di Elettrotecnica

Politecnico di Milano, Milan, Italy

G. SIMIOLICESI

Milan, Italy



Distribution test networkDistribution test network L01

L04

L12

L45

L23

L56

Load 1 Load 2 DG1

G ~ DG2

G ~ DG3

G ~

B

C

A

1 2 3

6 5 4

0

HV Network

Load 4

Load 3

Load 6 Load 5

HV/MV Transformer



Voltage Profile in MV Voltage Profile in MV Distribution NetworkDistribution Network

These figures show the voltage diagrams along a 20 kV line in the absence and in the presence of a regulation system. The use of ULTC (Under-Load-Tap-Changers) at the primary sub-station greatly improves the trend along the time axis, but the voltage drop along the line remains almost the same.



Costant Power Factor Control Costant Power Factor Control of Distributed Generationof Distributed Generation

We have limited to ±4% the, voltage drop:Load Generator

Results Objective function

2

1Lk k

k n nr L P x L Qi j i j

i j i j iV

V

2

min ,

1Gkh kh

h kr L P x L Qi G i G

iVV

k Lk Gkh k khV V V min maxh k k kh



Costant Power Factor Control Costant Power Factor Control of Distributed Generationof Distributed Generation

Table shows the maximum voltage drop at any node k in the course of one day as a function of a 5 MW generator's position. The space-time diagram of the voltage along the line shows how the generator and the UTLC at the primary sub-station can improve the voltage profiles (surface more flat).

PosNode 1 2 3

1 0.0055 0.0055 0,0055

2 0.0196 –0.0084 –0.0084

3 0.0266 0.0110 –0.0195



Constant Voltage Control of Constant Voltage Control of Distributed GenerationDistributed Generation

Condition

Generator Reactive Power

2

1

1

h n n

i j G i j hi j i j i

GhT h

ii

r L P P x L Q V

Qx L

h hh h



Constant Voltage Control of Constant Voltage Control of Distributed GenerationDistributed Generation

To keep the rated voltage at the node where a 5 MW DG is inserted h = 0 corresponds. By carrying out the procedure described we obtain the results in table. The graph shows that constant voltage control further improves the voltage profiles along the line, but that, especially with changes in the load, it maintains the voltage most stable at the node where the generator is inserted.

PosNode 1 2 3

1 0 0.0035 0.0035

2 0.0141 0.0071 0.0071

3 0.0212 0 0

QG [Mvar] 4.4049 3.1803 1.9557



Network reconfigurationNetwork reconfiguration

L45 L56 L04 C

L01 L12 L23

Load 1 Load 2 DG1

G ~ DG2

G ~ DG3

G ~

B

A

1 2 3

6 5 4

0

HV Network

Load 4

Load 3

Load 6 Load 5

HV/MV Transformer

L36




L45 L04 C

L01 L12 L23

Load 1 Load 2 DG1

G ~ DG2

G ~ DG3

G ~

B

A

1 2 3

6 5 4

0

HV Network

Load 4

Load 3

Load 6 Load 5

HV/MV Transformer

L36




L56 L04 C

L01 L12 L23

Load 1 Load 2 DG1

G ~ DG2

G ~ DG3

G ~

B

A

1 2 3

6 5 4

0

HV Network

Load 4

Load 3

Load 6 Load 5

HV/MV Transformer

L36




L45 L56

L01 L12 L23

Load 1 Load 2 DG1

G ~ DG2

G ~ DG3

G ~

B

A

1 2 3

6 5 4

0

HV Network

Load 4

Load 3

Load 6 Load 5

HV/MV Transformer

L36



Network reconfigurationNetwork reconfigurationWe want to insert in 3 two 5 MW groups with a power factor of 0.9; that is, with total power exceeding the line's total load, but such as not to overload the line. The power flow has now been inverted, and the voltage at the end of L1 is consequently greater than at the beginning that are unacceptable for the proper operation of the electric power system. By operating a network reconfiguration the optimal network configuration, that is the one that minimizes voltage variations at the nodes, is the one that involves shifting loads 5 and 6 from line L2 to line L1.



ConclusionConclusion• The introduction of generators into distribution networks,

built and operated in such a way that they are passive, alters the power flows and consequently the voltage profiles.

• It has been pointed out that the correct positioning of the generators may lead to an improvement in the voltage profiles, both in terms of space (along the line) and in terms of time (with variations in absorption). In the second case, a decisive factor is the type of generator control: indeed, as we have seen, constant voltage control greatly reduces the voltage variations during the day, but is generally speaking more expensive to operate than constant power factor control. How economical it is will therefore depend on the sensitivity of the loads to voltage variations.



ConclusionConclusion• Should it not be possible to select the position in which to

insert the generator, overvoltages may occur at the point of insertion of the generator. In such an event, the problem can be solved by suitable reconfiguration of the network and more uniform redistribution of the power flows.

• If adequate reconfiguration of the network were not possible, it would be necessary to reduce the maximum injectable power of the generator, or else to adapt line L1 to the new requirements.

A. AGUSTONI, M. BRENNA, R. FARANDA, E. TIRONI Dipartimento di Elettrotecnica

Documents

Transcript of A. AGUSTONI, M. BRENNA, R. FARANDA, E. TIRONI Dipartimento di Elettrotecnica