System and method for managing recovery of control in an electrical system
A method of managing recovery from an event in an electrical circuit leading to a loss of control of an inverter in the electrical circuit is disclosed, the method comprising sampling a parameter of operation before the event, monitoring for occurrence of the event, calculating an estimated value of the parameter at a time after the event based on an extrapolation of the monitored parameter and controlling the inverter using the estimated value of the parameter.
1. A method of managing recovery from an event in an electrical circuit leading to a loss of control of an inverter in the electrical circuit, the method comprising:
sampling a parameter of operation before the event;
monitoring for an occurrence of the event;
disabling the inverter in response to the occurrence of the event;
calculating an estimated value of the parameter at a time after the event based on an extrapolation of the parameter;
controlling the inverter using the estimated value of the parameter; and
re-enabling the inverter using the estimated value of the parameter.
2. The method as claimed in claim 1 in which the event is a transient in a current in the electrical circuit.
3. The method as claimed in claim 1 in which the parameter is sampled and stored for multiple sample periods before the event.
4. The method as claimed in claim 3 in which the estimated value of the parameter is based on the parameter from one or more sample periods.
5. The method as claimed in claim 1 in which the parameter is related to a phase angle of alternating supply voltages of the electrical circuit.
6. The method as claimed in claim 5 in which the estimated value of the parameter is derived from an estimate of a reference frame angle controlling a three phase alternating current from the inverter.
7. The method as claimed in claim 6 in which the parameter in a first sample period is used to produce the estimated value as an angle of the alternating supply voltages, and the parameter in a second sample period is used with the parameter from the first sample period to derive an estimate of a frequency of the alternating supply voltages for synchronizing the control of the inverter to the alternating supply voltages.
8. The method as claimed in claim 1 in which the electrical circuit comprises a d.c. source connected to one side of the inverter, for example a renewable energy source such as a photovoltaic array.
9. The method as claimed in claim 1 in which the electrical circuit comprises an additional inverter supplying a motor is connected to another side of the inverter.
10. The method as claimed in claim 1 in which a voltage demand to the inverter coincident with the estimated value of the parameter is set at a non-zero value less than a voltage before the event, for example half the voltage before the event.
11. A system for managing recovery from an event in an electrical circuit leading to a loss of control of an inverter in the electrical circuit, the system comprising:
means for sampling a parameter of operation before the event;
an overcurrent disabling system for monitoring for an occurrence of the event;
means for disabling the inverter in response to the occurrence of the event;
means for calculating an estimated value of the parameter at a time after the event based on an extrapolation of the parameter; and
a space vector modulator for controlling the inverter using the estimated value of the parameter and for re-enabling the inverter using the estimated value of the parameter.
12. The system as claimed in claim 11 in which the event is a transient in a current in the electrical circuit.
13. The system as claimed in claim 11 in which the means for sampling are operable to sample the parameter and stored it for multiple sample periods before the event.
14. The system as claimed in claim 13 in which the means for calculating are operable to estimate the estimated value of the parameter based on the parameter from one or more sample periods.
15. The system as claimed in claim 11 in which the parameter is related to a phase angle of alternating supply voltages of the electrical circuit.
16. The system as claimed in claim 15 in which the estimated value of the parameter is derived from an estimate of a reference frame angle controlling a three phase alternating current from the inverter.
17. The system as claimed in claim 16 in which the means for calculating are operable to use the parameter in a first sample period to produce the estimated value as an angle of the alternating supply voltages, and use the parameter in a second sample period with the parameter from the first sample period to derive an estimate of the frequency of the alternating supply voltages for synchronizing control of the inverter to the alternating supply voltages.
18. The system as claimed in claim 11 in which the electrical circuit comprises a d.c. source connected to one side of the inverter, for example a renewable energy source such as a photovoltaic array.
19. The system as claimed in claim 11 in which the electrical circuit comprises an additional inverter supplying a motor connected to another side of the inverter.
20. The system as claimed in claim 11 in which a voltage demand to the inverter coincident with the estimated value of the parameter is set at a non-zero value less than a voltage before the event, for example half the voltage before the event.