Method and arrangement for determining a load angle of a generator which is connected to an electrical supply network

• US 5,302,906 A
• Filed: 09/21/1992
• Issued: 04/12/1994
• Est. Priority Date: 03/21/1990
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Lerch, Edwin
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): TOBIN, C
• Application Number:
  US07/927,298
• Time in Patent Office: 568 Days
• Field of Search: 322/20, 322/99, 323/207, 323/210, 323/211, 323/212, 324/76, 324/34, 324/650
• US Class Current: 324/650
• CPC Class Codes: H02J 3/24 Arrangements for preventing or reducing oscillations of power in networks by control effected upon a single generator H02P9/00

Abstract

In an electrical supply network containing a generator, critical fluctuations in real power can occur. The load angle of the generator is representative of these fluctuations. The present invention provides a method which measures the real and reactive power flow, the current and the voltage on a line to the generator and feeds these measured values along with reactance values Y_L and Y_Q of the generator and line to a computing device. The computing device determines an output signal δ which represents the load angle of the generator and fluctuations in real power. The output signal δ is provided to an indicating device and/or a reactive power compensator.

Claims

1. A method for controlling fluctuations in real power in an electrical supply network, which includes a generator coupled to the electrical supply network via a line, the method comprising the steps of:

a) detecting measured values of current and voltage at any desired location within the electrical supply network;

b) providing the measured values to a measured value transducer;

c) forming a voltage signal V, a real power flow signal P, and a reactive power flow signal Q in said measured value transducer;

d) performing a reduction of the electrical supply network to determine equivalent variables for the generator and line parallel reactance component Y_Q and for the generator and line series reactance component Y_L ;

e) providing the signals Q, P, V, Y_Q and Y_L to a computing device;

f) determining an angular measure δ

of a load angle of the generator according to the following equation;

##EQU4## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables;

g) providing the angular measure of the load angle δ

to a reactive power compensator; and

h) controlling the real power in the electrical supply network with a reactive power compensator by using the angular measure of the load angle δ

as a controlled variable in the reactive power compensator.

3. The method according to claim 1, wherein the electrical supply network has more than two generators coupled to it, further comprising the steps of:

i) reducing the electrical supply network to a two generator system to determine Y_Q and Y_L.

2. A method for controlling fluctuations in real power in an electrical supply network, which includes a generator coupled to the electrical supply network via a line, the method comprising the steps of:

a) detecting measured values of current and voltage in the electrical supply network;

b) providing the measured values to a measured value transducer;

c) forming a voltage signal V, a real power flow signal P, and a reactive power flow signal Q in said measured value transducer;

d) performing a reduction of the electrical power network to determine equivalent variables for the generator and line parallel reactance component Y_Q and for the generator and line series reactance component Y_L ;

e) providing the signals Q, P, V, Y_Q and Y_L to a computing device;

f) determining an angular measure δ

of the fluctuations in the real power δ

of the generator according to the following equation;

##EQU5## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables;

g) providing the angular measure δ

of the fluctuations in the real power to a control device of a reactive power compensator; and

h) regulating the fluctuations in the real power with the reactive power compensator by using the angular measure δ

of the fluctuations in the real power as a controlled variable in the control device.

4. The method according to claim 2, wherein the electrical supply network has more than two generators coupled to it, further comprising the step of:

i) reducing the electrical supply network to a two generator system to determine Y_Q and Y_L.

5. A method for controlling the real power in an electrical supply network, which includes two generators coupled to the electrical supply network via two lines, the method comprising the steps of:

a) detecting measured values of current and voltage at any desired location in the electrical supply network for each generator;

b) providing the measured values for each generator to a measured value transducer;

c) forming a voltage signal V, a real power flow signal P, and a reactive power flow signal Q for each generator in the measure value transducer;

d) reducing the electrical supply network to determine for each generator equivalent variables for the generator and line parallel reactance component Y_Q and for the generator and line series reactance component Y_L ;

e) providing the signals Q, P, V, Y_Q and Y_L for each generator to a computing device;

f) determining a load angle δ

_a'"'"' δ

_b of each generator according to the following equation;

##EQU6## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables;

g) forming a difference signal Δ

δ

which represents a difference between the load angles δ

_a'"'"' δ

_b of the two generators;

h) providing the difference signal Δ

δ

as a controlled variable to a control device of a reactive power compensator; and

i) regulating the real power in the electrical supply network with the reactive power compensator to damp out fluctuations in the real power, whereby Δ

δ

represents a difference in the angular measure of the load angles of the generators or a difference in fluctuations in the real power of the generators.

6. A device for controlling fluctuations in real power of a generator coupled to an electrical supply network via a line, the device comprising:

a) a plurality of sensors being coupled to the electrical supply network and detecting measured values of current and voltage in the line;

b) a measured value transducer being coupled to the plurality of sensors and forming a voltage signal V, a real power flow signal P, and a reactive power flow signal Q;

c) a plurality of input elements being coupled to the measured value transducer, forming a signal Y_Q for the generator and line parallel reactance component, and forming a signal Y_L for the generator and line series reactance component;

d) a computing device being coupled to the plurality of input elements, receiving the signals V, P, Q, Y_Q and Y_L and determining the load angle δ

of the generator according to the following equation;

##EQU7## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables; and

e) a reactive power compensator being coupled to the computing device, and regulating the fluctuations in the real power in the generator using the load angle δ

as a controlled variable.

7. A device for controlling real power fluctuations in a generator coupled to an electrical supply network via a line comprising:

a) a plurality of sensors being coupled to the electrical supply network, and detecting measured values of current and voltage;

b) a measured value transducer forming a voltage signal V, a real power flow signal P, and a reactive power flow signal Q;

c) a plurality of input elements forming a signal Y_Q for the generator and line parallel reactance component and a signal Y_L for the generator and line series reactance component;

d) a computing device receiving the signals Q, P, V, Y_Q and Y_L from said of plurality of input elements and determining a load angle δ

of the generator according to the following equation;

##EQU8## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables; and

g) a reactive power compensator having a control device being coupled to the computing device, receiving the load angle as a controlled variable, controlling the real power in the generator to damp out fluctuation in the real power.

8. The device according to claim 7 further comprising an indicating device being coupled to the computing device and receiving the load angle from said computing device.

9. A device for controlling real power fluctuations in two generators, the first of which is coupled to an electrical supply network via a first line and the second of which is coupled to the electrical supply network via a second line, the device comprising:

a) a first plurality of sensors being coupled to the electrical supply network via the first line, and detecting measured values of current and voltage in the first line;

b) a second plurality of sensors being coupled to electrical supply network via the second line, and detecting measured values of current and voltage in the second line;

c) a first measured value transducer forming a first voltage signal V, a first real power flow signal P, and a first reactive power flow signal Q for the first generator;

d) a second measured value transducer forming a second voltage signal V, a second real power flow signal P, and a second reactive power flow signal Q for the second generator;

e) a first plurality of input elements forming a first signal Y_Q for the first generator and line parallel reactance component and a first signal Y_L for the first generator and line series reactance component;

f) a second plurality of input elements forming a second signal Y_Q for the second generator and line parallel reactance component and a second signal Y_L for the second generator and line series reactance component;

g) a computing device receiving the first and second signals Q, P, V, Y_Q and Y_L from said first and second plurality of input elements, respectively, and determining a first load angle δ

_a of the first generator and a second load angle δ

_b of the second generator according to the following equation;

##EQU9## where Im denotes an imaginary part, Re denotes a real part and j denotes a complex operator, and Y_Q and Y_L are complex variables, and outputting a difference between the first and second load angles δ

_a'"'"' δ

_b ; and

g) a reactive power compensator having a control device being coupled to the computing device, receiving the difference between the first and second load angles as a controlled variable, controlling the real power in the first and second generators to damp out fluctuations in the real power.