# US 12,119,750 B2 · Redundancy of a resonant converter stage by frequency adaptation

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- Number: US 12,119,750 B2
- Document ID: US12119750B2
- Status: Granted
- Kind: B2
- Application number: 17/753,963
- Filed: 2020-09-18
- Published: 2022-12-01
- Granted: 2024-10-15
- Earliest claimed: 2019-09-20
- Assignees: ABB Schweiz AG
- Applicants: ABB Schweiz AG
- Inventors: Uwe Drofenik; Ki-Bum Park; Thomas Bernhard Gradinger
- Web page: https://patentgrep.com/patent/US12119750B2

## CPC

- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0058: {by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826)}
- H02M 3/01: {Resonant DC/DC converters}
- H02M 1/325: {with means for allowing continuous operation despite a fault, i.e. fault tolerant converters}
- H02M 3/015: {with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuit}
- H02M 3/33571: {Half-bridge at primary side of an isolation transformer}
- H02M 7/4815: {Resonant converters (H02M7/4811 and H02M7/4826 take precedence)}
- H02M 7/493: the static converters being arranged for operation in parallel
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A resonant DC/DC converter which has a first DC link, preferably including a first DC link capacitor; a DC/AC converter which has a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge comprising a plurality of switches each of which may be switched between a conducting state and a non-conducting state. The resonant DC/DC converter also includes an AC intermediate circuit having an input connected to an output of the DC/AC converter and comprising: a transformer, preferably a medium frequency transformer, having a primary side and a secondary side; the primary side comprising at least one primary winding; a first plurality of N capacitors, wherein for each converter bridge, a different one from the first plurality of capacitors is connected between said converter bridge and the at least one primary winding.

## Claims

### Claim 1

A resonant DC/DC converter, comprising:
a first DC link;
a DC/AC converter comprising a first plurality of N>1 converter bridges connected in parallel to the first DC link,
wherein N is an integer,
wherein each converter bridge of the first plurality of N>1 converter bridges comprising a plurality of semiconductor switches, and
wherein each semiconductor switch of the plurality of semiconductor switches may be switched between a conducting state and a non-conducting state;
an AC intermediate circuit connected to the DC/AC converter and comprising:
a transformer having a primary side and a secondary side;
wherein the primary side comprises a plurality of M>1 primary windings,
wherein M is an integer;
a first plurality of N capacitors,
wherein each capacitor of the first plurality of N capacitors is connected between a respective converter bridge of the first plurality of N>1 converter bridges and a common node,
a second plurality of M capacitors,
wherein each capacitor of the second plurality of M capacitors is connected between the common node and a respective primary winding of the plurality of M>1 primary windings;
a control unit configured to switch the plurality of semiconductor switches of the first plurality of N>1 converter bridges between the conducting state and the non-conducting state or vice versa with a switching frequency to supply an AC current or voltage to the AC intermediate circuit;
a plurality of N current sensing means,
wherein, for each converter bridge of the first plurality of N>1 converter bridges, a current sensing means of the plurality of N current sensing means is provided for monitoring a current through the converter bridge of the first plurality of N>1 converter bridges;
wherein the control unit is configured to determine whether the current through a converter bridge of the first plurality of N>1 converter bridges deviates from an expected value; and
wherein the control unit is configured to increase the switching frequency in response to the current through the converter bridge of the first plurality of N>1 converter bridges deviating from the expected value.

### Claim 2 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the control unit is configured to adapt the switching frequency according to an adapted switching frequency for switching a remaining semiconductor switches of the plurality of semiconductor switches of a remaining N−1 converter bridges after the converter bridge of the first plurality of N>1 converter bridges deviates from the expected value.

### Claim 3 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the control unit is configured to determine whether the current through the converter bride of the first plurality of N>1 converter bridges deviates from the expected value by determining whether an absolute value of the current is smaller than a given threshold.

### Claim 4 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the control unit is configured to determine whether the current through the converter bridge of the first plurality of N>1 converter bridges deviates from the expected value by determining whether the current is smaller than 1/100 of a rated, nominal, or maximum current of each converter bridge.

### Claim 5 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the control unit is configured to, upon determination that the current through the converter bridge of the first plurality of N>1 converter bridges deviates from the expected value, deactivate the converter bridge.

### Claim 6 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein for each converter bridge of the first plurality of N>1 converter bridges, the current sensing means of the plurality of N current sensing means is provided between each converter bridge and each capacitor connected between each converter bridge and the plurality of M>1 primary windings.

### Claim 7 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein AC current sensors are used as the plurality of N current sensing means for measuring an AC current output by the first plurality of N>1 converter bridges.

### Claim 8 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the first DC link comprises a first DC link capacitor.

### Claim 9 (depends on 1)

The resonant DC/DC converter according to claim 1, wherein the transformer is a medium frequency transformer configured to operate at a frequency range from 500 Hz to 500 kHz.

### Claim 10

A method for controlling a resonant DC/DC converter, the resonant DC/DC converter comprising:
a first DC link;
a DC/AC converter comprising a first plurality of N>1 converter bridges connected in parallel to the first DC link,
wherein N is an integer,
wherein each converter bridge of the first plurality of N>1 converter bridges comprising a plurality of semiconductor switches,
wherein each semiconductor switch of the plurality of semiconductor switches may be switched between a conducting state and a non-conducting state;
an AC intermediate circuit connected to the DC/AC converter and comprising:
a transformer having a primary side and a secondary side;
wherein the primary side comprises a plurality of M>1 primary windings,
wherein M is an integer;
a first plurality of N capacitors,
wherein each capacitor of the first plurality of N capacitors is connected between a respective converter bridge of the first plurality of N>1 converter bridges and a common node;
a second plurality of M capacitors,
wherein each capacitor of the second plurality of M capacitors is connected between the common node and a primary winding of the plurality of M>1 primary windings; and
a control unit configured to switch the plurality of semiconductor switches of the first plurality of N>1 converter bridges between the conducting state and the non-conducting state or vice versa with a switching frequency to supply an AC current or voltage to the AC intermediate circuit;
wherein the method comprises:
for each converter bridge of the first plurality of N>1 converter bridges, monitoring a current through each converter bridge;
determining whether the current through a converter bridge of the first plurality of N>1 converter bridges deviates from an expected value; and
increasing the switching frequency if the current through the converter bridge of the first plurality of N>1 converter bridges deviates from the expected value.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the switching frequency is adapted to an adapted switching frequency for switching a remaining semiconductor switches of the plurality of semiconductor switches of a remaining N−1 converter bridges after the converter bridge of the first plurality of N>1 converter bridges deviates from the expected value.

### Claim 12 (depends on 10)

The method according to claim 10, wherein determining whether the current through the converter bridge deviates from the expected value is performed by determining whether an absolute value of the current is smaller than a given threshold.

### Claim 13 (depends on 10)

The method according to claim 10, wherein determining whether the current through the converter bridge deviates from the expected value is performed by determining whether the current is smaller than 1/100 of a rated, nominal, or maximum current of each converter bridge.

### Claim 14 (depends on 10)

The method according to claim 10, further comprising: upon determination that the current through the converter bridge deviates from the expected value, deactivating the converter bridge.

### Claim 15 (depends on 10)

The method according to claim 10, further comprising:
providing a plurality of N current sensing means; and
for each converter bridge, measuring the current through each converter bridge of the first plurality of N>1 converter bridges by a current sensing means of the plurality of N current sensing means provided between each converter bridge and each capacitor connected between each converter bridge and the plurality of M>1 primary windings.

### Claim 16 (depends on 10)

A control unit for controlling the resonant DC/DC converter according to the method of claim 10.

### Claim 17 (depends on 10)

A non-transitory computer program product comprising instructions which, when said instructions are executed by a data processing system, cause the data processing system to carry out the method according to claim 10.

### Claim 18 (depends on 10)

The method according to claim 10, wherein the first DC link comprises a first DC link capacitor.

### Claim 19 (depends on 10)

The method according to claim 10, wherein the transformer is a medium frequency transformer configured to operate at a frequency range from 500 Hz to 500 kHz.