# US 10,312,694 B2 · Mode-based output synchronization using relays and a common time source

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- Number: US 10,312,694 B2
- Document ID: US10312694B2
- Status: Granted
- Kind: B2
- Application number: 15/631,007
- Filed: 2017-06-23
- Published: 2018-12-27
- Granted: 2019-06-04
- Earliest claimed: 2017-06-23
- Assignees: Schweitzer Engineering Laboratories, Inc.
- Applicants: Schweitzer Engineering Laboratories, Inc.
- Inventors: Scott M. Manson
- Web page: https://patentgrep.com/patent/US10312694B2

## CPC

- H02J 3/40: Synchronisation of generators for connection to a network or to another generator
- H02J 3/381: {Dispersed generators}
- H02J 3/44: with means for ensuring correct phase sequence
- H02M 1/42: Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M 7/42: Conversion of DC power input into AC power output without possibility of reversal
- H02J 3/388: Arrangements for the handling of islanding, e.g. for disconnection or for avoiding the disconnection of power
- H02J 2101/10: Dispersed power generation using fossil fuels, e.g. diesel generators
- H02J 2101/24: Photovoltaics
- H02J 2101/28: Wind energy
- H02J 2105/10: Local stationary networks having a local or delimited stationary reach
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- Y02E 10/76: Power conversion electric or electronic aspects
- Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y04S 10/18: using switches, relays or circuit breakers, e.g. intelligent electronic devices [IED]
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- 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)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

The present disclosure pertains to systems and methods for selectively synchronizing one or more power conversion units of one or more distributed energy resources with a common time source when in an islanded state and with a measured phase angle of a grid when in a grid-connected state. In various embodiments, detecting whether the distributed energy resource is in a grid-connected state or an islanded state comprises microprocessor based analysis of measurement and monitoring data collected by intelligent electronic devices associated with the grid.

## Claims

### Claim 1

A method for phase alignment of a power conversion unit of distributed energy resource, comprising:
receiving timing signal from an external common time source;
receiving a signal from an external controller that a distributed energy resource (DER) is in a grid-connected state in which the output of one or more power conversion units of the DER are providing power to a power grid;
determining a phase angle of power on the power grid;
adjusting, while in the grid-connected state, a phase angle of the one or more power conversion units within the DER to correspond to the determined phase angle of the power on the power grid;
receiving a signal from an external controller that the DER is in an islanded state in which the DER is no longer electrically connected to the power grid; and
maintaining, while in the islanded state, the phase angle of the one or more power conversion units within the DER based on the received timing signal from the external common time source.

### Claim 2 (depends on 1)

The method of claim 1, wherein receiving the timing signal from the external common time source comprises receiving one of an Inter-Range Instrumentation Group (IRIG) time code and/or Precision Time Protocol (PTP) signal.

### Claim 3 (depends on 1)

The method of claim 1, wherein adjusting the phase angle of the one or more power conversion units comprises modifying one or more firing timings of one or more grid-tie inverters.

### Claim 4 (depends on 1)

The method of claim 1, wherein determining the phase angle of power on the power grid comprises receiving data from a transformer measurement of the power grid.

### Claim 5 (depends on 1)

The method of claim 1, wherein in the islanded state, the one or more power conversion units of the DER remain connected to a microgrid and are configured to continue to supply power to at least one load connected to the microgrid.

### Claim 6 (depends on 1)

The method of claim 1, wherein the DER is electrically connected to the power grid via a microgrid, wherein the microgrid can be selectively disconnected from at least one of the power grid and the DER.

### Claim 7

A controller for a power system comprising:
at least one communication port to receive monitoring information from at least one intelligent electronic device (IED) monitoring at least one electrical component associated with at least one of a microgrid and a macrogrid;
a state determination subsystem to determine, based on received monitoring information from the IED, periods during which a distributed energy resource (DER) of the microgrid is connected to the macrogrid in a grid-connected state and periods during which the DER is disconnected from the macrogrid in an islanded state; and
a phase angle control system to indicate that a common time source should be used to maintain a phase angle of an output of a power conversion unit of the DER based on determination that the DER is in the islanded state.

### Claim 8 (depends on 7)

The controller of claim 7, wherein the monitoring information received by the at least one communication port from the IED comprises at least one of: measurement data from a power transformer (PT) of at least one phase line of the macrogrid and data from a breaker monitoring relay.

### Claim 9 (depends on 7)

The controller of claim 7, wherein the phase angle control system is configured to communicate with a phase lock loop controller of the DER.

### Claim 10 (depends on 7)

The controller of claim 7, wherein the phase angle control system is further configured to provide a common time source signal to the DER.

### Claim 11

A system comprising:
a plurality of distributed energy resources (DERs) selectively connected to a macrogrid, wherein each of the plurality of DERs comprises:
a power conversion unit to convert power from one of a DC source and an AC source into output AC power for connection of the DER to the macrogrid;
a phase angle adjuster to adjust the phase angle of the output AC power; and
a common time source receiver to receive a common time source signal;
a plurality of IEDs configured to monitor at least a phase angle of the macrogrid and a connection state of each DER with the macrogrid; and
a DER controller in communication with each of the plurality of DERs, the DER controller configured to:
identify a status of each DER as one of (i) grid-connected, in which the DER is connected to the macrogrid, or (ii) islanded, in which the DER is disconnected from the macrogrid; and
direct the phase angle adjuster of each DER to synchronize the phase angle of output AC power with the phase angle of the macrogrid when the DER is grid-connected, and
direct the phase angle adjuster of each DER to synchronize the phase angle of output AC power using the common time source signal when the DER is islanded.

### Claim 12 (depends on 11)

The controller of claim 11, wherein the DER controller is further configured to selectively reconnect at least two of the islanded DERs to the macrogrid in parallel, wherein the at least two islanded DERs remained synchronized with the macrogrid while islanded via the phase angle adjuster using the common time source signal.

### Claim 13

A system comprising:
a power conversion unit for a distributed energy resource (DER) to convert power from one of a DC source and an AC source into output AC power for connection of the DER to a power grid;
a phase angle adjuster to adjust the phase angle of the output AC power;
a DER state identifier to receive an indication that the DER is in one of (i) a grid-connected state in which the DER is connected to the power grid, or (ii) in an islanded state in which the DER is disconnected from at least a portion of the power grid; and
phase alignment controller in communication with the phase angle adjuster to cause the phase angle adjuster to adjust the phase angle of the output AC power based on:
a measured value from the power grid in a grid-connected state, and
a common time source signal in an islanded state.

### Claim 14 (depends on 13)

The system of claim 13, wherein the phase angle adjuster comprises a phase locked loop.

### Claim 15 (depends on 13)

The system of claim 13, wherein power conversion unit is configured to output AC power for connection of the DER to a power grid via a microgrid, wherein the microgrid has at least one load independent of the power grid.

### Claim 16 (depends on 13)

The system of claim 13, wherein in the islanded state, the power conversion unit is configured to output AC power to the at least one independent load on the microgrid while electrically disconnected from the power grid.

### Claim 17 (depends on 13)

The system of claim 13, wherein power conversion unit comprises a grid-tie inverter configured to convert DC power into output AC power.

### Claim 18 (depends on 17)

The system of claim 17, wherein the phase angle adjuster comprises a phase locked loop connected to at least one of an internal thyristor and an insulated-gate bipolar transistor (IGBT) of the grid-tie inverter.

### Claim 19 (depends on 13)

The system of claim 13, wherein the DER state identifier is configured to receive measurement data from an intelligent electronic device monitoring at least one electrical component associated with the power grid.

### Claim 20 (depends on 19)

The system of claim 19, wherein the DER state identifier is configured to receive measurement data from an intelligent electronic device monitoring a voltage of a transformer on the power grid.

### Claim 21 (depends on 13)

The system of claim 13, wherein the phase angle adjustor is configured to adjust the phase angle of the output AC power of the power conversion unit to match a phase angle from measured voltage of a transformer of the power grid when in the grid-connected state.