Systems and methods for DC power line communication in a photovoltaic system

• US 10,187,115 B2
• Filed: 02/15/2017
• Issued: 01/22/2019
• Est. Priority Date: 07/13/2015
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Kahn, Seth M., Razzell, Charles J., Ng, Vincent W.
• Primary Examiner(s): King, Curtis
• Application Number:
  US15/433,958
• Publication Number:
  US 20170163311A1
• Time in Patent Office: 706 Days
• Field of Search: None
• CPC Class Codes: G05F 5/00 Systems for regulating electric variables by detecting deviations in the electric input to the system and thereby controlling a device within the system to obtain a regulated output
• CPC Class Codes: H02S 40/34 comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
• CPC Class Codes: H04B 2203/5412 by modofying wave form of the power source
• CPC Class Codes: H04B 3/542 the information being in digital form
• CPC Class Codes: H04B 3/546 Combination of signalling, telemetering, protection circuits for remote indication of supply or distribution network condition H02J13/00
• CPC Class Codes: H04B 3/548 the power on the line being DC arrangements for feeding power H04L12/10; extracting feeding power from signals H04L25/02
• CPC Class Codes: H04Q 2209/30 using a wired architecture
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02B 10/10 Photovoltaic [PV]
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A method for direct current power line communication in a photovoltaic system includes (a) transferring power between at least one photovoltaic device and a load using a power line, (b) maintaining a magnitude of a current flowing through the power line above a threshold value in a normal operating mode of the photovoltaic system, (c) detecting a change in operation of the power line in response to magnitude of a direct current component of the current flowing through the power line falling below the threshold value, and (d) in response to the detected change in operation of the power line, decoding operating state of the power line to obtain information.

Claims

1. A method for direct current (DC) power line communication in a photovoltaic system, comprising:

transferring power between at least one photovoltaic device and a load using a power line;

performing maximum power point tracking (MPPT) by the load;

detecting MPPT being performed by the load; and

in response to detecting the MPPT being performed by the load, causing the at least one photovoltaic device to remain enabled,

wherein the steps of performing MPPT and detecting MPPT are performed by different respective devices.

2. The method of claim 1, further comprising:

detecting lack of MPPT being performed by the load; and

in response to detecting lack of MPPT being performed by the load, disabling the at least one photovoltaic device.

3. The method of claim 2, further comprising, after the step of the disabling the at least one photovoltaic device:

injecting a signal mimicking MPPT activity onto the power line;

detecting the signal mimicking MPPT activity as MPPT being performed by the load; and

in response to detecting the signal mimicking MPPT activity as MPPT being performed by the load, enabling the at least one photovoltaic device.

4. The method of claim 2, wherein the step of detecting MPPT being performed by the load comprises asserting a detection signal in response to an autocorrelation of an AC component signal exceeding a reference value, the AC component signal representing an alternating current component of voltage across the power line or current through the power line.

5. The method of claim 2, wherein:

the step of performing MPPT by the load comprises modulating at least one of power line voltage amplitude, power line current amplitude, or MPPT perturbation pulse width according to a sequence; and

the step of detecting MPPT being performed by the load comprises detecting the sequence in an electrical signal on the power line.

6. The method of claim 5, wherein the step of detecting the sequence in the electrical signal on the power line comprises asserting a detection signal in response to a cross-correlation of an AC component signal and the sequence exceeding a reference value, the AC component signal representing an alternating current component of voltage across the power line or current through the power line.

7. The method of claim 6, the sequence comprising a pseudo noise code.

8. A photovoltaic system, comprising:

a power line;

at least one photovoltaic device electrically coupled to the power line;

a load electrically coupled to the power line, the load configured to perform maximum power point tracking (MPPT);

a MPPT detector separate from the load and configured to detect MPPT being performed by the load; and

a controller configured to cause the at least one photovoltaic device to remain enabled in response to the MPPT detector detecting MPPT being performed by the load.

9. The photovoltaic system of claim 8, wherein:

the MPPT detector is further configured to detect lack of MPPT being performed by the load; and

the controller is further configured to disable the at least one photovoltaic device in response to the MPPT detector detecting lack of MPPT being performed by the load.

10. The photovoltaic system of claim 9, wherein the MPPT detector is further configured to assert a detection signal in response to an autocorrelation of an AC component signal exceeding a reference value, the AC component signal representing an alternating current component of voltage across the power line or current through the power line.

11. The photovoltaic system of claim 9, wherein:

the load is further configured to modulate at least one of power line voltage amplitude, power line current amplitude, or MPPT perturbation pulse width according to a sequence; and

the MPPT detector is configured to detect MPPT being performed by the load by detecting the sequence in an electrical signal on the power line.