A power line communication system

Abstract

The application relates to the field of power line communication, and discloses a power line communication system. The power line communication system can comprise a power conversion device, a signal isolation circuit, a signal adjustment circuit, a transformer and an operation circuit. The output end of the power conversion device is connected with a power line through the signal isolation circuit, the signal isolation circuit can be used for isolating an input signal of the power line to obtain a first noise signal of the power conversion device. The first input end of the signal adjustment circuit is connected with the output end of the power conversion device, the signal adjustment circuit can be used for inverting the phase of the first noise signal and outputting a second noise signal. The input end of the transformer is connected with the power line, the transformer can be used for filtering a power signal in the input signal of the power line to output a first signal. The operation circuit can be used for outputting a first communication signal according to the first signal and the second noise signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power line communication, and particularly relates to a power line communication system. BACKGROUND

[0002] Power line communication (PLC) refers to a communication technology that utilizes power lines as a communication medium and transmits signals through a carrier wave. PLC can be applied in various fields. For example, in a photovoltaic power generation system, communication is performed between an inverter and a host through power lines. The host can send control signals to the inverter through the power lines to schedule the inverter, and the inverter can send service signals to the host through the power lines to report the device status.

[0003] With the evolution of the power of the photovoltaic power generation system, the power of the inverter is continuously increasing. Since the communication signals are integrated on the power lines, the increase in the power of the inverter will inevitably cause the noise on the PLC communication frequency band to deteriorate, and the PLC communication performance will also deteriorate. In order to solve the noise problem, the current inverter usually uses an analog circuit in the output stage of the inverter to suppress power supply noise. However, as the photovoltaic subarray becomes larger and larger, the communication distance of the PLC system is also increasing. In the scenario of long-distance communication, the communication frequency band of the PLC system is relatively low, and the analog circuit has a large volume at low frequency. Therefore, a large board area is usually occupied, which is not conducive to the miniaturization design of the device. SUMMARY

[0004] The present application provides a power conversion device and a power line communication system. The power conversion device can effectively reduce the influence of power supply noise on communication signals and improve the reliability of communication signals under the premise of realizing small size design.

[0005] In a first aspect, the present application provides a power line communication system, which can include a power conversion device, a signal isolation circuit, a signal adjustment circuit, a transformer, and an operation circuit. The output end of the power conversion device is connected to the power line through the signal isolation circuit, and the signal isolation circuit can be used to isolate the input signal of the power line to obtain the first noise signal of the power conversion device. The first input end of the signal adjustment circuit is connected to the output end of the power conversion device, and the signal adjustment circuit can be used to invert the phase of the first noise signal and output the second noise signal. The input end of the transformer is connected to the power line, and the transformer can be used to filter out the power signal in the input signal of the power line to output the first signal. The operation circuit can be used to output the first communication signal according to the first signal and the second noise signal.

[0006] In the above scheme, the first communication signal is separated from the first noise signal, and the first noise signal is collected. Then, the signal adjusting circuit outputs the second noise signal by inversely phase-shifting the first noise signal. In this way, the operation circuit can output the first communication signal according to the second noise signal and the first signal output by the transformer. Thus, the power conversion device power noise can be suppressed, thereby effectively reducing the influence of the first communication signal and improving the reliability of the communication signal. Moreover, compared with the prior art, the signal isolation circuit in the present application occupies relatively small space, thus helping to realize the miniaturization design of the system.

[0007] In some possible embodiments, the first signal specifically can include the first noise signal and the first communication signal. In this way, after the operation circuit superimposes the first signal and the second noise signal, the second noise signal can cancel the first noise signal in the first signal, thereby outputting the first communication signal.

[0008] In some possible embodiments, the signal isolation circuit specifically can include, but is not limited to, an isolation capacitor or an isolation inductor.

[0009] Exemplarily, the signal isolation circuit specifically can be a differential mode capacitor or a differential mode inductor.

[0010] In some possible embodiments, the signal isolation circuit can be integrated in the power conversion device, thereby saving the board space in the power conversion device and helping to reduce the volume of the power conversion device.

[0011] In some possible embodiments, the signal adjusting circuit can also be used to adjust the amplitude of the first noise signal, so that the amplitude of the second noise signal output by the signal adjusting circuit can be closer to the amplitude of the first noise signal, and the second noise signal can more effectively cancel the first noise signal in the first signal.

[0012] In some possible embodiments, the signal adjusting circuit can also include a second input end, the second input end of the signal adjusting circuit can be connected with the output end of the operation circuit, and the signal adjusting circuit specifically can be used to adaptively adjust the amplitude of the first noise signal according to the target value of the first communication signal. This design can effectively improve the noise filtering effect, so that the accuracy of the first communication signal output by the operation circuit is higher, and the communication reliability of the system is further improved.

[0013] In some possible embodiments, the power line communication system can also include a sampling circuit, an input end of the sampling circuit can be connected with an output end of the power conversion device, and an output end can be connected with a first input end of the signal adjusting circuit. The sampling circuit specifically can be used to collect the first noise signal isolated by the signal isolation circuit and output to the signal isolation circuit.

[0014] In a specific implementation, the sampling circuit can include an automatic gain controller and an analog-to-digital converter connected to the automatic gain controller, the automatic gain controller can be connected to the output of the power conversion device, and the analog-to-digital converter can be connected to the output of the signal adjustment circuit. The automatic gain controller can automatically control the amplitude of the first noise signal by changing the input-output compression ratio, thereby providing conditions for the analog-to-digital converter to sample in the optimal linear region, and realizing a high-fidelity design of noise signal acquisition.

[0015] In some possible embodiments, the signal adjustment circuit includes but is not limited to a digital filter. The signal adjustment circuit can adaptively adjust the phase and amplitude of the first noise signal according to the circuit structure design of the power conversion device, compensate for system differences caused by the circuit structure, make the phase of the adjusted second noise signal closer to the inverse phase of the first noise signal, and make the amplitude of the second noise signal closer to the amplitude of the first noise signal. In this way, the second noise signal can more effectively cancel out the first noise signal in the first signal after entering the operation circuit.

[0016] In some possible embodiments, the operation circuit includes but is not limited to a multiplier.

[0017] In some possible embodiments, the power conversion device includes but is not limited to an inverter, an energy storage battery, etc. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A schematic diagram of a power line communication system provided by an embodiment of the present application;

[0019] Figure 2 A structural schematic diagram of a photovoltaic power generation system;

[0020] Figure 3 A partial architecture diagram of a power line communication system provided by an embodiment of the present application;

[0021] Figure 4 A partial structural schematic diagram of a power line communication system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. However, the example embodiments can be implemented in various forms, and should not be understood as being limited to the embodiments set forth herein. The same reference numerals in the drawings represent the same or similar structures, and thus repeated description thereof will be omitted. The expressions of position and direction described in the embodiments of the present application are described with reference to the drawings, but can be changed as needed, and the changes made are included in the scope of protection of the present application. The drawings of the embodiments of the present application are only used to illustrate the relative positional relationship and do not represent the true proportions.

[0023] It should be noted that specific details are set forth in the following description in order to facilitate understanding of the present application. However, the embodiments of the present application can be implemented in various other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotations of the embodiments of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0024] PLC refers to a communication technology that uses power lines as a communication medium and transmits signals through a carrier wave. One major advantage of PLC over other communication technologies is that PLC can use existing power lines as a transmission medium, without the need to lay new lines, thereby greatly reducing the upfront deployment cost, and also eliminating the need for separate line maintenance, further reducing the maintenance cost in the later stage.

[0025] Based on the State Grid Low Voltage Power Line Broadband Carrier Communication Interconnection Technical Specification, the institute of electrical and electronics engineers (IEEE) 1901.1 standard is officially released and implemented. The standard divides the PLC protocol stack into the following layers: application layer, transport layer, network layer, data link layer, and physical layer. Among them, the data link layer includes a network management sublayer and a medium access control (MAC) sublayer. The network management sublayer is responsible for the aggregation and fragmentation of application layer messages, network management, and the update and maintenance of routing, and the MAC sublayer is responsible for occupying the physical channel to provide reliable communication. The physical layer is responsible for transmitting the data from the MAC sublayer to the power line after encoding and modulation, and returning the signal received from the power line to the MAC sublayer after demodulation and decoding.

[0026] Reference Figure 1 As shown in the drawings, Figure 1A schematic diagram of a PLC system is provided in the embodiments of the present application. The electronic device roles in the PLC system for communication can include a central coordinator (CCO), a proxy coordinator (PCO), and a station (STA). The CCO can schedule or control one or more STAs by sending control frames to the one or more STAs, for example, the control frames can be used to indicate the maximum power configured for the one or more stations. The one or more STAs can report their device states to the CCO by sending traffic frames to the CCO. The PCO can assist the STAs that are far away from the CCO to access the PLC network, and can also manage the device states of the STAs under the PCO and report the device states of the STAs under the PCO to the CCO. It should be noted that the PCO in the embodiments of the present application can also be referred to as a proxy station, and the STA can also be referred to as a discovery station. Unless otherwise specified, the station in the embodiments of the present application refers to the discovery station (STA).

[0027] The PLC can be applied in various scenarios, such as in Figure 2 As shown in a photovoltaic power generation system, direct current generated by a photovoltaic panel is collected to an inverter, and is converted to alternating current by the inverter and then transmitted to a combiner box. The combiner box collects alternating current output by multiple inverters and transmits the alternating current to a transformer, which converts the alternating current to high-voltage power and then transmits the high-voltage power to a power grid. A host is connected between the combiner box and the transformer, and can be used to schedule the inverters and receive device states of the inverters. Here, the host and the inverters are respectively the central coordinator and the station in the PLC system described above.

[0028] With the evolution of the power of the photovoltaic power generation system, the power of the inverter is increasing. Since the communication signal is integrated on the power line, the increase in the power of the inverter will inevitably cause the noise on the PLC communication frequency band to deteriorate, and the PLC communication performance will also deteriorate. In order to solve the noise problem, the current inverter usually uses an analog circuit in the output stage to achieve the suppression effect on the power noise. However, as the photovoltaic subarray becomes larger, higher requirements are put forward for the communication distance and the communication latency of the PLC system. In the scenario of long-distance communication, the communication frequency band of the PLC system is relatively low, and the analog circuit has a large size at low frequency, so it usually occupies a large board area and has a high cost.

[0029] In view of this, the embodiments of the present application provide a PLC system, which can effectively reduce the influence of power noise on the communication signal and improve the reliability of the communication signal on the premise of realizing small size design. The embodiments of the present application will be described in further detail below with reference to the drawings and specific embodiments.

[0030] Referring to Figure 3 , Figure 3A partial architecture diagram of a power line communication system is provided in the embodiments of the present application. In the embodiments of the present application, the PLC system can include a power conversion device and a peer device, the power conversion device can communicate with the peer device through a power line, and the peer device can transmit a first communication signal to the power conversion device through the power line. For example, the power conversion device in the embodiments of the present application can be a station, and the peer device can be a central coordinator, in which case the first communication signal can be a control frame. Alternatively, the power conversion device in the embodiments of the present application can be a central coordinator, and the peer device can be a station, in which case the first communication signal can be a service frame.

[0031] The PLC system can further include a signal isolation circuit, a signal adjustment circuit, a transformer, and an operation circuit. The output end of the power conversion device can be connected with the power line through the signal isolation circuit, and the signal isolation circuit can be used to isolate the input signal of the power line to obtain a first noise signal of the power conversion device. Since the power conversion device has a power supply inside, the output end of the power conversion device and the power line will inevitably have power supply noise, and the first noise signal herein is the power supply noise. The input end of the transformer can also be connected with the power line, and the transformer can be used to filter the power signal in the input signal of the power line to output a first signal. In the embodiments, the first signal can include the first noise signal and the first communication signal.

[0032] The first input end a1 of the signal adjustment circuit can be connected with the output end of the power conversion device, and the signal adjustment circuit can be used to invert the first noise signal and output a second noise signal obtained after inversion.

[0033] The operation circuit includes a first input end b1 and a second input end b2, the first input end b1 of the operation circuit can be connected with the output end of the transformer, and the second input end b2 of the operation circuit can be connected with the output end of the signal adjustment circuit. The operation circuit can be used to output the first communication signal according to the first signal output by the transformer and the second noise signal output by the adjustment circuit, so as to achieve the suppression effect of the power supply noise of the power conversion device, thereby effectively reducing the influence of the power supply noise on the first communication signal and improving the reliability of the first communication signal.

[0034] In some possible embodiments of the present application, the PLC system can further include a sampling circuit, the input end of the sampling circuit can be connected with the output end of the power conversion device, and the output end can be connected with the first input end of the signal adjustment circuit. The sampling circuit can be used to collect the first noise signal isolated by the signal isolation circuit and output to the signal isolation circuit. In addition, the power conversion device can further include a control circuit, the control circuit can be connected with the output end of the operation circuit, and the control circuit can be used to demodulate the first communication signal and perform subsequent processing.

[0035] Reference Figure 4 as shown, Figure 4A partial structure diagram of a power line communication system is provided in the embodiments of the present application. In the embodiments of the present application, the specific type of the power conversion device is not limited, for example, the power conversion device can be an inverter, an energy storage battery, etc. The signal isolation circuit includes but is not limited to an isolation capacitor or an isolation inductor, and specifically can be a differential mode capacitor, a differential mode inductor, a common mode capacitor or a common mode inductor, etc. The signal isolation circuit can be integrated in the power conversion device, so that the board space of the signal isolation circuit in the power conversion device can be saved, thereby helping to reduce the volume of the power conversion device. Of course, in other embodiments, the signal isolation circuit can be arranged outside the power conversion device, and the specific design can be made according to the structure layout of the power conversion device, which is not limited in the present application.

[0036] In the specific arrangement of the sampling circuit, the sampling circuit can include an automatic gain controller (AGC) and an analog to digital converter (ADC), wherein the input end of the automatic gain controller is connected with the output end of the power conversion device, the output end is connected with the input end of the analog to digital converter, and the output end of the analog to digital converter is connected with the input end of the signal adjustment circuit. The automatic gain controller can automatically control the amplitude of the first noise signal by changing the input-output compression ratio, thereby providing conditions for the analog to digital converter to sample in the optimal linear region, and realizing high-fidelity design of noise signal acquisition.

[0037] In the embodiments of the present application, the signal adjustment circuit includes but is not limited to a digital filter, which can adaptively adjust the phase of the first noise signal according to the circuit structure design of the power conversion device, compensate for the system difference caused by the circuit structure, and make the phase of the adjusted second noise signal more close to the inverse phase of the first noise signal.

[0038] Continuing to refer to Figure 4 In the specific arrangement of the operation circuit, the operation circuit can be realized by a multiplier, at this time, the operation circuit can superimpose the input first signal and the second noise signal, offset or partially offset the first noise signal in the first signal, and output the first communication signal.

[0039] In some possible embodiments, the signal adjustment circuit can also be used to adjust the amplitude of the first noise signal, so that the amplitude of the second noise signal output by the signal adjustment circuit can be more close to the amplitude of the first noise signal, and further can make the second noise signal more effectively offset the first noise signal in the first signal.

[0040] It can be understood that if the second noise signal and the first noise signal in the first signal are not completely cancelled out, some noise signals will inevitably exist in the first communication signal output by the operation circuit. In order to reduce the influence of these noise signals on the first communication signal, in some possible embodiments, the signal adjusting circuit can further include a second input end a2, the second input end a2 of the signal adjusting circuit can be connected with the output end of the operation circuit, and the signal adjusting circuit can be specifically used for adaptively adjusting the phase and amplitude of the first noise signal according to the target value of the first communication signal, and outputting the second noise signal, wherein the target value of the first communication signal includes but is not limited to the signal-to-noise ratio of the first communication signal. With this design, the filtering effect of the noise signal can be effectively improved, so as to improve the accuracy of the first communication signal output by the operation circuit, and further improve the communication reliability of the PLC system.

[0041] In addition, in the embodiments of the present application, the sampling circuit, the signal adjusting circuit, the operation circuit and the like can be integrated in the power conversion device, or can also be arranged outside the power conversion device, such as in the controller of the power conversion device, and the present application does not limit this, and the specific design can be made according to the structure layout of the power conversion device.

[0042] In summary, the PLC system provided by the embodiments of the present application can separate the power supply noise of the power conversion device from the communication signal, can effectively suppress the power supply noise, and can solve the problem of communication performance deterioration caused by power evolution of the power conversion device, and can effectively improve the communication reliability of the PLC system.

[0043] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A power line communication system, characterized by, The power line communication system comprises a power conversion device, a signal isolation circuit, a signal adjustment circuit, a transformer and an operation circuit, wherein an output end of the power conversion device is connected with a power line through the signal isolation circuit, the signal isolation circuit is used for obtaining a first noise signal of the power conversion device by isolating an input signal of the power line; a first input end of the signal adjustment circuit is connected with the output end of the power conversion device, the signal adjustment circuit is used for inverting a phase of the first noise signal and outputting a second noise signal; an input end of the transformer is connected with the power line, the transformer is used for filtering a power signal in the input signal of the power line and outputting a first signal; the operation circuit outputs a first communication signal according to the first signal and the second noise signal.

2. The power line communication system of claim 1, wherein, The first signal comprises the first noise signal and the first communication signal.

3. The power line communication system of claim 1 or 2, wherein The signal isolation circuit comprises an isolation capacitor or an isolation inductor.

4. The power line communication system of any one of claims 1 to 3, wherein, The signal isolation circuit is integrated in the power conversion device.

5. The power line communication system of any one of claims 1 to 4, wherein, The signal adjustment circuit is also used for adjusting an amplitude of the first noise signal.

6. The power line communication system of claim 5, wherein, a second input end of the signal adjustment circuit is connected with an output end of the operation circuit, and the signal adjustment circuit is specifically used for adjusting the amplitude of the first noise signal according to a target value of the first communication signal.

7. The power line communication system of any one of claims 1 to 6, wherein, The power line communication system further comprises a sampling circuit, an input end of the sampling circuit is connected with an output end of the power conversion device, an output end of the sampling circuit is connected with the first input end of the signal adjustment circuit, and the sampling circuit is used for collecting the first noise signal isolated by the signal isolation circuit and outputting.

8. The power line communication system of claim 7, wherein, The sampling circuit comprises an automatic gain controller and an analog-to-digital converter connected with the automatic gain controller, the automatic gain controller is connected with the output end of the power conversion device, and the analog-to-digital converter is connected with the input end of the signal adjustment circuit.

9. The power line communication system of any one of claims 1 to 8, wherein, The signal adjustment circuit comprises a digital filter.

10. The power line communication system of any one of claims 1 to 9, wherein, The power conversion device comprises an inverter.

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