Method and control arrangement in a power system

1. A method of controlling a magnitude of an electrical parameter in a power system by means of a high voltage electron tube that is parallel connected to a capacitor, the method comprising:

measuring the magnitude of the electrical parameter,

generating a control signal based on the magnitude of the electrical parameter and on a reference magnitude of the electrical parameter that changes dynamically, the control signal being a pulse wave, and

switching the high voltage electron tube by means of the control signal such that the reference magnitude of the electrical parameter is essentially obtained and a variable capacitive compensation in the power system is provided.

2. A method of controlling a magnitude of an electrical parameter in a power system by means of a high voltage electron tube, the method comprising:

measuring the magnitude of the electrical parameter,

generating a control signal based on the magnitude of the electrical parameter and on a reference magnitude of the electrical parameter that changes dynamically, the control signal being a pulse wave, and

switching the high voltage electron tube by means of the control signal such that the reference magnitude of the electrical parameter is essentially obtained

wherein said high voltage electron tube is arranged as a start-up device for connecting a load to the power system,

wherein the switching of the high voltage electron tube comprises switching the high voltage electron tube such that the magnitude of the electrical parameter increases from being essentially zero to an operational magnitude level of the load.

3. The method as claimed in claim 1 , comprising detecting a surge by determining a deviation in the magnitude of the electrical parameter from a predetermined range, wherein the step of switching involves switching the high voltage electron tube such that the surge is essentially removed from the power system.

4. A non-transitory computer program product comprising a computer program stored on a computer readable medium and executable on a computer, which computer program when executed on the computer performs a method of controlling a magnitude of an electrical parameter in a power system by means of a high voltage electron tube that is parallel connected to a capacitor, the method comprising:

measuring the magnitude of the electrical parameter,

generating a control signal based on the magnitude of the electrical parameter and on a reference magnitude of the electrical parameter that changes dynamically, the control signal being a pulse wave, and

switching the high voltage electron tube by means of the control signal such that the reference magnitude of the electrical parameter is essentially obtained and a variable capacitive compensation in the power system is provided.

5. A control arrangement for controlling a magnitude of an electrical parameter in a power system, which control arrangement comprises:

a high voltage electron tube having first connection means and second connection means for connection to the power system,

a control unit arranged to be connected to the high voltage electron tube, and

a measuring unit arranged to measure the magnitude of the electrical parameter in the power system, and to provide a measure of the magnitude of the electrical parameter to the control unit,

wherein the control unit is arranged to generate a control signal in the form of a pulse wave based on the magnitude of the electrical parameter and on a reference magnitude of the electrical parameter, which reference magnitude changes dynamically, and to switch the high voltage electron tube by means of the control signal such that the reference magnitude of the electrical parameter is essentially obtained,

wherein the control arrangement forms a start-up device for connecting a load to the power system, and the control unit is arranged to switch the high voltage electron tube such that the magnitude of the electrical parameter increases from being essentially zero to an operational magnitude level of the load.

6. The control arrangement as claimed in claim 5 , wherein the high voltage electron tube is a cold cathode electron tube.

7. A power system comprising a control arrangement as claimed in claim 5 .

8. The power system as claimed in claim 7 , wherein the control arrangement is arranged to detect a surge in the power system by determining a deviation in the magnitude of the electrical parameter from a predetermined range, wherein the control unit is arranged to switch the high voltage electron tube such that the surge is essentially removed from the power system.

9. A control arrangement for controlling a magnitude of an electrical parameter in a power system, which control arrangement comprises:

a high voltage electron tube having first connection means and second connection means for connection to the power system,

a control unit arranged to be connected to the high voltage electron tube, and

a measuring unit arranged to measure the magnitude of the electrical parameter in the power system, and to provide a measure of the magnitude of the electrical parameter to the control unit,

wherein the control unit is arranged to generate a control signal in the form of a pulse wave based on the magnitude of the electrical parameter and on a reference magnitude of the electrical parameter, which reference magnitude changes dynamically, and to switch the high voltage electron tube by means of the control signal such that the reference magnitude of the electrical parameter is essentially obtained,

wherein the high voltage electron tube is arranged in parallel with the capacitor thereby providing a variable capacitive compensation in the power system.

10. The power system as claimed in claim 9 , wherein the capacitor is series connected with a load in the power system.

11. The power system as claimed in claim 9 , comprising a bypass arrangement for bypassing the control arrangement in case of a fault current in the power system occurs, which fault current has a magnitude above a predetermined threshold.

12. The power system as claimed in claim 1 , wherein the capacitor is series connected with a load in the power system.

13. The power system as claimed in claim 1 , comprising a bypass arrangement for bypassing the control arrangement in case of a fault current in the power system occurs, which fault current has a magnitude above a predetermined threshold.