HIGH VOLTAGE DC SYSTEMS

A high voltage DC (HVDC) system can include a generator configured to output alternating current (AC), a rectifier connected to the generator via AC phase lines, the rectifier configured to convert the AC to DC to output the DC to DC feeder lines, and a crowbar system. The crowbar system can include a switch module operatively connected to the AC phase lines to prevent AC from flowing to the rectifier in a cutoff state. The crowbar system can be configured to determine whether at least one cutoff condition exists. The at least one cutoff condition can be or include one or more of a DC overcurrent downstream of the rectifier, a DC overvoltage downstream of the rectifier, an AC overcurrent from the generator, or an arc fault. The crowbar system can be configured to control the switch module to the cutoff state if the at least one cutoff condition exists.

FIELD

This disclosure relates to high voltage DC systems

BACKGROUND

For high voltage DC (HVDC) generator/rectifier systems, fault conditions such as feeder short circuits or arc fault require fast protection response to limit structure, panel, and equipment damage. Additionally, contactors required to open and isolate for the anomalous short circuit or arc fault condition can become significantly degraded after performing function to break the anomalous condition. Existing designs can leverage a crowbar system to short the source generator three phase output for fast protection response to limit AC voltage levels. However, overcurrent conditions, DC overvoltage conditions, and arc fault conditions can become more of a damage and safety issue at higher system voltage levels.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved HVDC systems. The present disclosure provides a solution for this need.

SUMMARY

In accordance with at least one aspect of this disclosure, a high voltage DC (HVDC) system can include a generator configured to output alternating current (AC), a rectifier connected to the generator via AC phase lines, the rectifier configured to convert the AC to DC to output the DC to DC feeder lines, and a crowbar system. The crowbar system can include a switch module operatively connected to the AC lines to prevent AC from flowing to the rectifier in a cutoff state. The crowbar system can be configured to determine whether at least one cutoff condition exists. The cutoff condition can be or include one or more of a DC overcurrent downstream of the rectifier, DC overvoltage downstream of the rectifier, an AC overcurrent from the generator, an AC overvoltage from the generator, or an arc fault. The crowbar system can be configured to control the switch module to the cutoff state if the at least one cutoff condition exists.

In certain embodiments, the AC phase lines can include three AC lines for three phase power or six AC lines for six phase power. The switch module can be configured to short each AC line together to cause phase summation to cancel the current to the rectifier.

In certain embodiments, the crowbar system can include a DC overcurrent sense module operatively connected to the rectifier and/or the DC feeder lines to sense a DC side current on the one or more DC lines. The DC side overcurrent sense module can be configured to control the switch module to activate the switch module to short each AC line together in the cutoff state when the DC side current is above a DC side overcurrent threshold.

The crowbar system can include an AC side overcurrent sense module operatively connected to the generator and/or the AC phase lines to sense an AC side current on the AC phase lines. The AC side overcurrent sense module can be configured to control the switch module to activate the switch module to short each AC line together in the cutoff state when an AC side current is above an AC side overcurrent threshold.

In certain embodiments, the crowbar system can include an AC side overvoltage sense module operatively connected to the AC phase lines to sense an AC side voltage on the AC phase lines. The AC side overvoltage sense module can be configured to control the switch module to activate the switch module to short each AC line together in the cutoff state when the AC side voltage is above an AC side overvoltage threshold.

In certain embodiments, the AC side overvoltage sense module can be connected to the AC phase lines between the switch module and the rectifier. In certain embodiments, the AC overcurrent sense module is connected to the AC phase lines between the generator and the switch module.

In certain embodiments, the crowbar system can include an arc sense module configured to sense an arc fault in the system. The arc sense module can be configured to control the switch module to activate the switch module to short each AC line together in the cutoff state when an arc fault is detected.

In certain embodiments, the system can include a generator control unit (GCU) operatively connected to the crowbar system to receive one or more signals from the crowbar system. The GCU can be operatively connected to the generator to control generator output. The crowbar system can be configured to send a fault signal to the GCU in the cutoff state to cause the GCU to reduce generator voltage output and/or to shut down the generator to cease generator voltage output.

In certain embodiments, the generator is a variable frequency generator, and the GCU can be configured to control excitation energy input to the generator to control the generator output. In certain embodiments, the system can include one or more contactors on each DC line between the rectifier and a DC bus, wherein the GCU is configured to control the contactors to allow or prevent DC voltage to the DC bus.

In accordance with at least one aspect of this disclosure, an aircraft can include a high voltage DC (HVDC) system. The HVDC system can be any suitable embodiment of a system disclosed herein, e.g., as described above.

In accordance with at least one aspect of this disclosure, a method can include sensing whether an overcurrent exists in a high voltage generator system, and shorting multiple phases together in response to an overcurrent in order to cancel current output to protect downstream equipment. The method can include any other suitable method(s) and/or portion(s) thereof.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a system in accordance with the disclosure is shown inFIG.1and is designated generally by reference character100. Other embodiments and/or aspects of this disclosure are shown inFIG.2. Certain embodiments described herein can be used to rapidly protect one or more electrical components from an overcurrent, overvoltage, and/or arc fault, e.g., in a high voltage scenario, faster than a generator controller can react, for example. Any suitable use or application is contemplated herein.

In accordance with at least one aspect of this disclosure, referring toFIG.1, a high voltage DC (HVDC) system100can include a generator101configured to output alternating current (AC). The system100can include a rectifier103connected to the generator101via AC phase lines105a,105b,105c(e.g., 3 phase or 6 phase). The rectifier103can be configured to convert the AC to DC to output the DC to DC feeder lines107a,107b. The system100can include a crowbar system109. The crowbar system109can include a switch module111operatively connected to the AC phase lines105a,105b,105c(or additional phase sets) to prevent AC from flowing to the rectifier103in a cutoff state.

The crowbar system109can be configured to determine whether at least one cutoff condition exists. The at least one cutoff condition can be or include one or more of (e.g., any combination of, all of) an AC overcurrent from the generator101, a DC overcurrent downstream of the rectifier103, a DC overvoltage downstream of the rectifier, an arc fault (e.g., anywhere in the system100). Any other suitable condition, (e.g., AC overvoltage) is also contemplated herein has a cutoff condition. The crowbar system109can be configured to control the switch module111to the cutoff state if the at least one cutoff condition exists.

The AC phase lines105a, b, c can include three AC lines105a, b, c for three phase power. The switch module111can be configured to short each AC line105a, b, c together (e.g., as shown inFIG.1) to cause three phase summation to cancel the current to the rectifier103. Any other suitable redirection of elimination of power from the generator101(such as additional phase sets) is contemplated herein.

In certain embodiments, the crowbar system109can include a DC overcurrent sense module113operatively connected to the rectifier103and/or the DC feeder lines107a,107bto sense a DC side current on the DC feeder lines107a, b. The DC side overcurrent sense module113can be configured to control the switch module111to activate the switch module111to short each AC line105a, b, c together in the cutoff state when the DC side current is above a DC side overcurrent threshold. Referring toFIG.2, the crowbar system109can include a DC overvoltage sense module220operatively connected to the system DC Point of Regulation (POR) and/or the DC lines107a,107bto sense a DC side voltage on the DC feeder lines107a, b. The DC side overvoltage sense module220can be configured to control the switch module111to activate the switch module111to short each AC line105a, b, c together in the cutoff state when the DC side voltage is above a DC side overvoltage threshold.

The crowbar system109can include an AC side overcurrent sense module115operatively connected to the generator101and/or the AC phase lines105a, b, c (e.g., via the same number of respective sense lines, e.g., as shown) to sense an AC side current on the AC phase lines105a, b, c (e.g., individually or as a group). The AC side overcurrent sense module115can be configured to control the switch module111to activate the switch module111to short each AC line105a, b, c together in the cutoff state when an AC side current is above an AC side overcurrent threshold.

In certain embodiments, the crowbar system109can include an AC side overvoltage sense module117operatively connected to the AC phase lines105a, b, c (e.g., via the same number of respective sense lines, e.g., as shown) to sense an AC side voltage on the AC phase lines105a, b, c (e.g., individually or as a group). The AC side overvoltage sense module117can be configured to control the switch module111to activate the switch module111to short each AC line together105a, b, c in the cutoff state when the AC side voltage is above an AC side overvoltage threshold.

In certain embodiments, the AC side overvoltage sense module117can be connected to the AC phase lines105a, b, c between the switch module111and the rectifier103. In certain embodiments, the AC overcurrent sense module115is connected to the AC phase lines105a, b, c between the generator101and the switch module111. Any other suitable connection is contemplated herein.

In certain embodiments, the crowbar system109can include an arc sense module119configured to sense an arc fault in the system100(e.g., at utilization equipment or damaged wire). The arc sense module119can be configured to control the switch module111to activate the switch module111to short each AC line105a, b, c together in the cutoff state when an arc fault is detected. The arc sense module119can include arc sense logic (e.g., using current sensing, voltage sensing, visual sensors, etc.) at any suitable location (e.g., the DC side of the rectifier103).

In certain embodiments, the system100can include a generator control unit (GCU)121operatively connected to the crowbar system109to receive one or more signals from the crowbar system109. The GCU121can be operatively connected to the generator101to control generator output. The crowbar system109can be configured to send a fault signal to the GCU121in the cutoff state to cause the GCU121to reduce generator voltage output and/or to shut down the generator101to cease generator voltage output.

In certain embodiments, the generator101is a variable frequency generator (VFG), and the GCU121can be configured to control excitation energy input to the generator101to control the generator output. In certain embodiments, the system100can include one or more contactors123a,123bon each DC line between the rectifier103and a DC bus125. The GCU121can be configured to control the contactors123a, b to allow or prevent DC voltage to the DC bus125.

Any suitable module(s) of this disclosure can include any suitable hardware and/or software module(s) configured to perform the disclosed function. Embodiments of modules (e.g., modules111,113,115,117,119,220) can be configured to react quickly enough (e.g., such as sub 50 ms response time) to minimize or avoid damage to components in a cutoff condition. For example, embodiments can include one or more analog circuit modules configured to react quickly enough, or the modules can include suitable fast reacting firmware.

In accordance with at least one aspect of this disclosure, an aircraft (not shown) can include a high voltage DC (HVDC) system. The HVDC system can be any suitable embodiment of a system, e.g., system100, disclosed herein, e.g., as described above.

In accordance with at least one aspect of this disclosure, a method can include sensing whether an overcurrent exists in a high voltage generator system, and shorting multiple phases together in response to an overcurrent in order to cancel current output to protect downstream equipment. The method can include any other suitable method(s) and/or portion(s) thereof.

Traditional systems use the GCU to handle overcurrent conditions, for example, which traditionally reacts on the order of seconds. In lower voltage systems, e.g., below 270 V, for example, this reaction time can be sufficient. But higher voltages benefit from rapid response (e.g., such as sub 50 ms to avoid damage). Therefore, because traditional generator control response times to overcurrent is sufficient in lower voltage systems, traditional systems need not apply crowbar system as there is less damage concern.

Embodiments can include a crowbar system (e.g., a solid state limiter) that reacts quick to overcurrent in one or more locations. Embodiments can include a high voltage DC (HVDC) system overvoltage, overcurrent, and arc fault (OV-OC-Arc) limiter crowbar system. Embodiments can utilize the crowbar method for dissipating HVDC generator/rectifier system high voltage, current and/or arc fault conditions.

In embodiments, current level thresholds and/or arc event conditions can be monitored as a method for detecting anomalous conditions and facilitating fast protection energy dissipation with source isolation response to limit fault durations. Embodiments include an HVDC OV-OC-Arc limiter crowbar approach can provide an independent device current limiting function for managing HVDC fault current and/or arc fault conditions, for example. Embodiments can quickly dampen the sourcing power, with GCU excitation coordination, to allow system level contactor isolation coordination at lower energy level.

In embodiments, generator current and/or rectifier current output current can be monitored by the HVDC current/arc limiter crowbar, and if defined abnormal levels for a given system are detected, the HVDC OV-OC-Arc Limiter Crowbar can trigger to short the generator power feeds and additionally coordinate GCU de-excitation of the channel. Reset can be automated with dedicated customer preference rules (e.g., such as once per flight cycle), or manually via a flight deck switch. Voltage levels illustrated are for a 230 Vac VFG and +/- 270 Vdc rectifier example, but the embodiments can be scaled for other architecture power levels such as 270 Vdc to ground systems and +/- 540 V for electric propulsion. Any suitable voltage system for application of embodiments is contemplated herein.

Embodiments provide a method for managing HVDC fault voltage/current/arc conditions, for example. Embodiments can provide benefits that include fast overvoltage, overcurrent, and arc fault response for HVDC to limit structure, panel, equipment damage, independent functionality to support any potential safety requirements, and extended contactor life thru reduce energy isolation coordination. Any other suitable benefits are contemplated herein.