Detecting ground faults on non-isolated dc systems
AssigneePika Energy LLC
InventorJoshua Daniel Kaufman
Life of this patent
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Abstract
A power conversion topology and control method intended for use with a DC bus is disclosed, providing a means to prevent the flow of ground fault current while detecting a fault condition and optionally continuing to operate the DC bus. In one control configuration, a DC-DC power stage with an active current control loop drives differential current to zero, and a separate voltage control loop maintains the desired differential bus voltage. Absolute bus voltage with respect to ground is monitored in order to detect fault conditions. In another configuration, the absolute voltage of the bus with respect to ground is controlled and differential bus current is monitored to detect ground fault conditions.
Claims21
(canceled)
A method of detecting ground fault currents comprising:
- providing a DC bus where ground fault currents are to be detected, the rails of the bus being tied to ground through a high impedance;
- providing a power converter capable of independently driving each rail of the bus from a source;
- controlling an absolute voltage of the DC bus with respect to ground;
- and
- monitoring differential bus current to detect ground fault conditions.
A method of detecting ground fault currents in a DC bus having rails tied to ground through a high impedance, the method comprising:
- independently driving each rail of the bus from a source;
- controlling an absolute voltage of the DC bus with respect to ground;
- and
- monitoring differential bus current to detect ground fault conditions.
A DC-DC power stage comprising:
- means for controlling the absolute voltage of the bus with respect to ground;
- and
- means to monitor differential bus current to detect ground fault conditions.
A circuit comprising:
- an AC stage having a plurality of half bridges driven independently by pulse-width-modulated signals to couple to an AC source of power;
- a DC-DC stage having a plurality of half bridges driven independently by pulse-width-modulated signals, the AC and DC-DC stages coupled via an internal DC link capacitor coupled between internal DC rails;
- a DC output stage having a positive rail and a negative rail coupled to ground via high-impedance grounding resistors, the rails coupled to respective half bridges of the DC-DC stage to receive positive and negative DC voltages respectively;
- and
- a differential sensor coupled to the DC output stage positive and negative rails to measure a difference in current, wherein an absolute voltage of the DC bus is controlled with respect to ground.
An AC to DC power converter comprising:
- an AC stage having multiple half-bridges disposed between shared internal rails to couple to an corresponding multiple legs of an AC supply;
- an internal DC stage joined to the AC stage by an internal DC link capacitor coupled between the shared internal rails, the internal DC stage having two half-bridges coupled between the shared internal rails;
- an output DC stage having output rails coupled to respective half-bridges of the internal DC stage via an output filter;
- and
- a current sensor coupled to detect a difference in current between the output rails, wherein an absolute voltage of the DC bus is controlled with respect to ground.
An AC to DC power converter comprising:
- a pair of internal DC bus rails;
- a plurality of buck/boost converters, one for each phase of an AC supply, disposed between the internal DC bus rails;
- a pair of output DC bus rails coupled to the internal DC bus rails;
- a voltage detector coupled to detect a voltage across each of the output DC bus rails with respect to ground;
- and
- a current sensor coupled to detect a difference in current between the output DC bus rails, wherein an absolute voltage of the output DC bus rails is controlled with respect to ground.
Dependencies are inferred from the claim text.