Method and device for estimating grid properties of a power grid

Patent metadata

Field	Value
Publication number	US-10296669-B2
Application number	US-201414318598-A
Country	US
Kind code	B2
Filing date	Jun 28, 2014
Priority date	Jul 18, 2013
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method for estimating grid properties of a power grid coupled to a generator at a point of common coupling is provided. First, a voltage V PCC at the point of common coupling is measured. Second, a current I PCC at the point of common coupling is measured. Third, the grid properties are estimated by a grid model using as input parameters the measured voltage V PCC at the point of common coupling, the measured current I PCC at the point of common coupling and the determined phase angle. Advantageously, the absolute phases of the voltage and the current at the point of common coupling are not necessary, which makes the present method less prone to errors due to measurement noise. Further, a device and a computer program product are provided.

First claim

The invention claimed is:

1. A method of controlling a generator of a power grid, comprising:
measuring, by a device, a magnitude of a voltage (V PCC ) and a magnitude of a current (I PCC ) at a point of common coupling (PCC) coupled to a generator of a power grid;
determining a phase angle (α) between the voltage (V PCC ) at the point of common coupling (PCC) and the current (I PCC ) at the point of common coupling (PCC);
estimating, by a processor of the device, grid properties (Z G , V G ) by a grid model using as input parameters the magnitude of the voltage (V PCC ) at the point of common coupling (PCC), the magnitude of the current (I PCC ) at the point of common coupling (PCC) and the phase angle α;
generating, by the device, a control signal representative of the estimated grid properties; and
controlling the generator by a controller, wherein the controller is configured to control the generator in dependence on the estimated grid properties (Z G , V G ) using the control signal.

2. The method of claim 1 ,
wherein the grid properties (Z G , V G ) include grid impedance (Z G ) and a grid voltage (V G ) of the power grid.

3. The method of claim 1 ,
wherein the voltage (V PCC ) at the point of common coupling (PCC) and the current (I PCC ) at the point of common coupling (PCC) are measured at a fundamental frequency of the power grid.

4. The method of claim 1 , further comprising:
a) measuring the voltage (V PCC ) at the point of common coupling (PCC) at N different working points of the power grid, N≥3,
b) measuring the current (I PCC ) at the point of common coupling (PCC) at the N different working points,
c) determining the phase angle (α) between the measured voltage (V PCC ) at the point of common coupling (PCC) and the measured current (I PCC ) at the point of common coupling (PCC) for each of the N different working points, and
d) estimating the grid properties (Z G , V G ) by the grid model using as input parameters the measured voltage (V PCC ) at the point of common coupling (PCC), the measured current (I PCC ) at the point of common coupling (PCC) and the phase angle (α) for the N different working points.

5. The method of claim 4 ,
wherein step d) includes eliminating absolute phases of the measured voltage (V PCC ) at the point of common coupling (PCC) and the measured current (I PCC ) at the point of common coupling (PCC).

6. The method of claim 4 ,
wherein the grid properties (Z G , V G ) include a resistive part (R) of the grid impedance (Z G ), a reactive part (X) of the grid impedance (Z G ) and the grid voltage (V G ) of the power grid.

7. The method of claim 6 ,
wherein the resistive part (R) of the grid impedance (Z G ), the reactive part (X) of the grid impedance (Z G ) and the grid voltage (V G ) are determined by solving the following equation for three different working points:
( V G ) 2 =|V PCC ( i )| 2 +( R 2 +X 2 )·| I PCC ( i )| 2 −2·| V PCC ( i )|·| I PCC ( i )|·( R ·cos(α( i ))+ X ·sin(α( i )))

i=1,2,3;
wherein V PCC indicates the measured voltage at the point of common coupling (PCC), I PCC indicates the measured current at the point of common coupling (PCC), and α indicates the phase angle between the measured voltage at the point of common coupling (PCC) and the measured current at the point of common coupling (PCC).

8. The method of claim 6 ,
wherein the resistive part (R) of the grid impedance (Z G ), the reactive part (X) of the grid impedance (Z G ) and the grid voltage (V G ) are determined by solving the following equation for three different working points:

(

V
G

)

2

=



V
PCC

⁡

(
i
)



2

+

(

R
2

+

X
2

)

·

(

P
2

⁡

(
i
)

+

Q
2

⁡

(
i
)

)



V
PCC

⁡

(
i
)



2

-

2
·

(

R
*

P
⁡

(
i
)

⁢
X
*

Q
⁡

(
i
)

)

,

⁢

⁢

i
=
1

,
2
,
3

wh

Assignees

• Siemens Ag

Inventors

• Andresen Bjorn
• Egedal Per
• Obradovic Dragan
• Scheiterer Ruxandra
• Szabo Andrei

Classifications

• H02J3/00142 Primary

  Oscillations concerning frequency · CPC title

• G01R27/16 Primary

  Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line · CPC title

• G01R19/00

  Arrangements for measuring currents or voltages or for indicating presence or sign thereof (G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24) · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G06F17/5009 Primary

  Physics · mapped topic