# US 11,309,802 B2 · Transformers, converters, and improvements to the same

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- Number: US 11,309,802 B2
- Document ID: US11309802B2
- Status: Granted
- Kind: B2
- Application number: 17/262,523
- Filed: 2019-07-23
- Published: 2021-09-02
- Granted: 2022-04-19
- Earliest claimed: 2018-07-23
- Assignees: Georgia Tech Research Corporation
- Applicants: Georgia Tech Research Corporation
- Inventors: Liran Zheng; Deepakraj M. Divan; Rajendra Prasad Kandula; Karthik Kandasamy
- Web page: https://patentgrep.com/patent/US11309802B2

## CPC

- H02M 3/33561: {having more than one ouput with independent control}
- H02M 5/458: using semiconductor devices only
- H02J 3/381: {Dispersed generators}
- 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 1/44: Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
- H02M 3/33584: {Bidirectional converters}
- H02M 5/225: {comprising two stages of AC-AC conversion, e.g. having a high frequency intermediate link}
- H02M 7/537: using semiconductor devices only, e.g. single switched pulse inverters
- H02J 2101/24: Photovoltaics
- H02M 1/0077: {Plural converter units whose outputs are connected in series}
- 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
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- 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)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A soft-switching solid-state power transformer, including: a high-frequency (HF) transformer comprising first and second winding connections; a first auxiliary resonant circuit coupled to the first winding connection, the first auxiliary resonant circuit comprising: a resonant capacitor coupled across the first winding connection, a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor, and a damping feature coupled across the first winding connection in series with the resonant capacitor and the resonant inductor; a first current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising reverse blocking switches configured to conduct current in one direction and block voltage in both directions; a second auxiliary resonant circuit coupled to the second winding connection; and a second CSI bridge coupled to the second auxiliary resonant circuit, the second CSI bridge comprising reverse blocking switches.

## Claims

### Claim 1

A soft-switching solid-state power transformer comprising:
a high-frequency (HF) transformer comprising first and second winding connections;
a first auxiliary resonant circuit coupled to the first winding connection of the HF transformer;
a second auxiliary resonant circuit coupled to the second winding connection of the HF transformer;
a first current-source inverter (CSI); and
a second CSI bridge;
wherein the first auxiliary resonant circuit comprises:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor; and
a damping feature coupled across the first winding connection in series with the resonant capacitor and the resonant inductor;
wherein the first CSI bridge is coupled to the first auxiliary resonant circuit and comprises reverse blocking switches configured to conduct current in one direction and block voltage in both directions; and
wherein the second CSI bridge is coupled to the second auxiliary resonant circuit and comprises reverse blocking switches configured to conduct current in one direction and block voltage in both directions.

### Claim 2 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein the first auxiliary resonant circuit further comprises a reverse blocking switch coupled across the first winding connection in series with the resonant inductor and in parallel to the resonant capacitor.

### Claim 3 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein the damping feature comprises a damping diode and in series with the resonant capacitor and the resonant inductor.

### Claim 4 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein the damping feature comprises a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor.

### Claim 5 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein the first CSI bridge comprises at least two phase legs; and
wherein each phase leg comprises a pair of the reverse blocking switches.

### Claim 6 (depends on 5)

The soft-switching solid-state power transformer of claim 5, wherein the first CSI bridge comprises three-phase legs; and
wherein each of the three-phase legs is configured to couple to a different phase of an AC power supply.

### Claim 7 (depends on 6)

The soft-switching solid-state power transformer of claim 6, wherein the first CSI bridge further comprises a fourth phase leg configured to couple to a neutral connection of the AC power supply.

### Claim 8 (depends on 5)

The soft-switching solid-state power transformer of claim 5 further comprising a first filter coupled to the at least two phase legs of the first CSI bridge.

### Claim 9 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein each of the reverse blocking switches comprise an insulated gate bipolar transistor (IGBT) series with a diode or a reverse blocking IGBT (RB-IGBT).

### Claim 10 (depends on 1)

The soft-switching solid-state power transformer of claim 1, wherein the second CSI bridge comprises at least two phase legs; and
wherein each phase leg comprises a pair of the reverse blocking switches.

### Claim 11 (depends on 10)

The soft-switching solid-state power transformer of claim 10, wherein the at least two phase legs are configured to couple to a load.

### Claim 12 (depends on 11)

The soft-switching solid-state power transformer of claim 11, wherein the load is a single-phase AC load or a DC load.

### Claim 13 (depends on 11)

The soft-switching solid-state power transformer of claim 11, wherein the load is a three-phase AC load; and
wherein the second CSI bridge comprises three-phase legs configured to couple to different phases of the load.

### Claim 14 (depends on 13)

The soft-switching solid-state power transformer of claim 13, wherein the second CSI bridge further comprises a fourth phase leg configured to couple to a neutral connection of the load.

### Claim 15 (depends on 1)

The soft-switching solid-state power transformer of claim 1 further comprising:
a first filter; and
a second filter;
wherein the first CSI bridge comprises at least two phase legs;
wherein each phase leg of the first CSI bridge comprises a pair of the reverse blocking switches;
wherein the second CSI bridge comprises at least two phase legs;
wherein each phase leg of the second CSI bridge comprises a pair of the reverse blocking switches;
wherein the first filter is coupled to the at least two phase legs of the first CSI bridge; and
wherein the second filter is coupled to the at least two phase legs of the second CSI bridge.

### Claim 16

A soft-switching solid-state power transformer comprising:
a high-frequency (HF) transformer comprising first and second winding connections;
a first auxiliary resonant circuit coupled to the first winding connection of the HF transformer;
a second auxiliary resonant circuit coupled to the second winding connection of the HF transformer;
a first current-source inverter (CSI); and
a second CSI bridge;
wherein the first auxiliary resonant circuit comprises:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor; and
a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor;
wherein the second auxiliary resonant circuit comprises:
a resonant capacitor coupled across the second winding connection;
a resonant inductor coupled across the second winding connection in parallel with the resonant capacitor of the second auxiliary resonant circuit; and
a damping feature coupled across the second winding connection in series with the resonant capacitor of the second auxiliary resonant circuit and the resonant inductor of the second auxiliary resonant circuit;
wherein the first CSI bridge is coupled to the first auxiliary resonant circuit and comprises reverse blocking switches configured to conduct current in one direction and block voltage in both directions; and
wherein the second CSI bridge is coupled to the second auxiliary resonant circuit and comprises reverse blocking switches configured to conduct current in one direction and block voltage in both directions.

### Claim 17

A reactive power compensator, comprising:
a high-frequency (HF) transformer comprising first, second and third winding connections;
a first auxiliary resonant circuit coupled to the first winding connection of the HF transformer, the first auxiliary resonant circuit comprising:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor; and
a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor;
a first current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising reverse blocking switches configured to conduct current in one direction and block voltage in both directions;
a second auxiliary resonant circuit coupled to the second winding connection of the HF transformer;
a second CSI bridge coupled to the second auxiliary resonant circuit, the second CSI bridge comprising reverse blocking switches configured to conduct current in one direction and block voltage in both directions;
a third auxiliary resonant circuit coupled to the third winding connection of the HF transformer; and
a third CSI bridge coupled to the third auxiliary resonant circuit, the third CSI bridge comprising reverse blocking switches configured to conduct current in one direction and block voltage in both directions.

### Claim 18 (depends on 17)

The reactive power compensator of claim 17, wherein:
the second auxiliary resonant circuit further comprises:
a resonant capacitor coupled across the second winding connection;
a resonant inductor coupled across the second winding connection in parallel with the resonant capacitor of the second auxiliary resonant circuit; and
a synchronous rectifier coupled across the second winding connection in series with the resonant capacitor of the second auxiliary resonant circuit and the resonant inductor of the second auxiliary resonant circuit; and
the third auxiliary resonant circuit further comprises:
a resonant capacitor coupled across the third winding connection;
a resonant inductor coupled across the third winding connection in parallel with the resonant capacitor of the third auxiliary resonant circuit; and
a synchronous rectifier coupled across the third winding connection in series with the resonant capacitor of the third auxiliary resonant circuit and the resonant inductor of the third auxiliary resonant circuit.

### Claim 19 (depends on 18)

The reactive power compensator of claim 18, wherein the first auxiliary resonant circuit further comprises a reverse blocking switch coupled across the first winding connection in series with the resonant inductor and in parallel to the resonant capacitor.

### Claim 20 (depends on 19)

The reactive power compensator of claim 19, wherein the first, second, and third CSI bridges comprise two phase legs, each phase leg comprising a pair of the reverse blocking switches.

### Claim 21 (depends on 20)

The reactive power compensator of claim 20, wherein first, second, and third CSI bridges are configured to couple to different phases of a three-phase AC power supply.

### Claim 22 (depends on 21)

The reactive power compensator of claim 21 wherein the two-phase legs of each of the first, second, and third CSI bridges are configured to couple to a phase connection and a common neutral connection.

### Claim 23

A stacked converter comprising:
a first and second converter module, each of the first and second converter modules comprising:
a high-frequency (HF) transformer comprising first and second winding connections;
a first auxiliary resonant circuit coupled across the first winding connection of the HF transformer, the first auxiliary resonant circuit comprising:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor;
a reverse blocking switch coupled across the first winding connection in series with the resonant inductor and in parallel to the resonant capacitor; and
a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor; and
a first current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising first, second, and third phase legs; and
a shared capacitor, the shared capacitor coupled to the second phase leg of the first CSI bridge of each of the first and second converter modules.

### Claim 24 (depends on 23)

The stacked converter of claim 23 further comprising a shared battery coupled to the second phase leg of the first CSI bridge of each of the first and second converter modules.

### Claim 25 (depends on 23)

The stacked converter of claim 23 further comprising:
a first photovoltaic panel connected to a first phase leg of the first converter module; and
a second photovoltaic panel connected to the first phase leg of the second converter module.

### Claim 26 (depends on 23)

The stacked converter of claim 23, wherein each of the first and second converter modules further comprises:
a second auxiliary resonant circuit coupled across to the second winding connection of the HF transformer, and
a second current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising two phase legs.

### Claim 27

A stacked converter comprising:
a first and second converter module, each of the first and second converter modules comprising:
a high-frequency (HF) transformer comprising first and second winding connections;
a first auxiliary resonant circuit coupled across the first winding connection of the HF transformer; and
a first current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising first, second, and third phase legs;
wherein the first auxiliary resonant circuit comprises:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor; and
a damping feature coupled across the first winding connection in series with the resonant capacitor and the resonant inductor; and
a shared battery, the shared battery coupled to the second phase leg of the first CSI bridge of each of the first and second converter modules.

### Claim 28 (depends on 27)

The stacked converter of claim 27, wherein the damping feature of each first auxiliary resonant circuit comprises a damping diode coupled across the first winding connection in series to the resonant capacitor and the resonant inductor.

### Claim 29 (depends on 27)

The stacked converter of claim 27, wherein the damping feature of each first auxiliary resonant circuit comprises a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor.

### Claim 30

A modular-stacked multi-stage converter comprising:
a first stage and a second stage, each of the first stage and the second stage comprising:
a first and second converter module, each of the first and second converter modules comprising:
a high-frequency (HF) transformer comprising first and second winding connections;
a first auxiliary resonant circuit coupled across the first winding connection of the HF transformer; and
a first current-source inverter (CSI) bridge coupled to the first auxiliary resonant circuit, the first CSI bridge comprising three phase legs;
wherein the first auxiliary resonant circuit comprises:
a resonant capacitor coupled across the first winding connection;
a resonant inductor coupled across the first winding connection in parallel with the resonant capacitor; and
a damping feature coupled across the first winding connection in series with the resonant capacitor and the resonant inductor; and
a shared capacitor, the shared capacitor coupled to the second phase leg of the first CSI bridge of each of the first and second converter modules of each of the first and second stages.

### Claim 31 (depends on 30)

The modular-stacked multi-stage converter of claim 30, wherein each first auxiliary resonant circuit further comprises a reverse blocking switch coupled across the first winding connection in series with the resonant inductor and in parallel to the resonant capacitor.

### Claim 32 (depends on 30)

The modular-stacked multi-stage converter of claim 30, wherein the damping feature of each first auxiliary resonant circuit comprises a damping diode coupled across the first winding connection in series to the resonant capacitor and the resonant inductor.

### Claim 33 (depends on 30)

The modular-stacked multi-stage converter of claim 30, wherein the damping feature of each first auxiliary resonant circuit comprises a synchronous rectifier coupled across the first winding connection in series with the resonant capacitor and the resonant inductor.