CN117439430A

CN117439430A - Inverter, power line communication device and photovoltaic system

Info

Publication number: CN117439430A
Application number: CN202311246085.7A
Authority: CN
Inventors: 周力; 水伟
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2023-09-26
Filing date: 2023-09-26
Publication date: 2024-01-23

Abstract

The application provides an inverter, its characterized in that includes magnetic device, signal modulation circuit, current detection unit, assist source, controller, signal transformer and first power line, and magnetic device is arbitrary one in magnetic ring, the transformer. The inverter is communicated with other power equipment through the first power line, the first power line and the second power line are wound on the magnetic device, the controller is used for controlling the auxiliary source to output I2 opposite to the first power line I1 to the second power line, so that magnetic fluxes generated by the I1 and the I2 are at least partially counteracted, the magnetic saturation of the magnetic device is reduced, and the reliability of transmission signals is improved.

Description

Inverter, power line communication device and photovoltaic system

Technical Field

The embodiment of the application relates to a power line communication technology, in particular to an inverter, a power line communication device and a photovoltaic system.

Background

With the development of power electronics, the generation of electric energy by using a novel energy source is widely used. Existing solar photovoltaic systems generally include various power devices for generating electric energy such as a direct current electric energy generating device (e.g., a photovoltaic array), an inverter, and the like, and converting the electric energy. Typically, the power devices are spaced apart a long distance (e.g., 1km between the dc power generation device and the inverter). For signal interaction between remote devices, PLC (power line communication ) is generally used for signal transmission.

In related PLC signal transmission, a magnetic loop is generally disposed on a power line to couple a signal to the power line, or the magnetic loop is used to increase input/output impedance between two power lines to reduce signal attenuation. While power lines typically transmit power while transmitting modulated signals. The electrical energy generally has a relatively high current. Under the condition of large through flow, the magnetic induction intensity of the magnetic ring reaches the maximum value quickly, so that the magnetic ring is saturated, the inductance of the magnetic ring is greatly attenuated, the PLC signal is attenuated, and the reliability of signal transmission is reduced. Thus, how to improve the reliability of PLC signal transmission in a power line communication device becomes a problem.

Disclosure of Invention

The application provides an inverter, which is used for communicating with other power equipment, and the magnetic flux generated by the current on a power line is counteracted by applying the current opposite to the current on the power line to a magnetic ring or a transformer, so that the magnetic saturation of the magnetic ring or the transformer is restrained, the magnetic permeability and the inductance attenuation of the magnetic ring or the transformer are restrained, and the reliability of PLC signal transmission under a large current scene is improved.

In a first aspect, the present application provides an inverter, including a magnetic device, a signal modulation circuit, a current detection unit, an auxiliary source, a controller, a signal transformer, and a first power line, where the magnetic device is any one of a magnetic ring and a transformer; the inverter communicates with other power devices through the first power line; the first power line is wound on one side of the magnetic device; the auxiliary source comprises a first output end and a second output end, one end of the second power line is connected with the first output end, the second power line is wound on the other side of the magnetic device, and the other end of the power line is connected with the second output end; the signal modulation circuit is coupled to the second power line through the signal transformer, and has signal demodulation and modulation functions; the current detection unit is used for detecting a current I1 on the first power line; the controller is used for controlling the auxiliary source to output current I2 to the second power line, and the direction of the I2 is opposite to that of the I1. Because the directions of the I2 and the I1 are opposite, at least part of the magnetic flux generated by the I2 and the magnetic flux generated by the I1 can offset and cancel, and can also cancel completely, the magnetic device can be prevented from reaching magnetic saturation, the inductance attenuation of the magnetic device is further inhibited, the signal attenuation of the PLC signal in the transmission process is prevented, and the stability of the PLC signal transmission is improved.

In a possible implementation manner, the signal transformer includes a primary winding and a secondary winding, an output end of the signal modulation circuit is coupled to the primary winding, and the secondary winding is coupled to the second power line; the ratio of the number of turns of the first power wire wound on the magnetic device to the number of turns of the second power wire wound on the magnetic device is the same as the ratio of the number of turns of the primary winding and the secondary winding of the transformer. The turns ratio of the primary winding and the secondary winding of the magnetic device is equal to that of the primary winding and the secondary winding of the signal transformer, so that impedance matching and signal conversion of the primary winding and the secondary winding of the magnetic device are realized, the types and the number of internal components of the inverter can be reduced, and the structural design of the inverter is simplified.

In one possible implementation, the ampere-turns of the first power wire wound on the magnetic device are the same as the ampere-turns of the second power wire wound on the magnetic device. The magnetic flux generated by the I2 and the magnetic flux generated by the I1 are completely counteracted, so that the degree and effect of inhibiting the magnetic saturation of the transformer are enhanced.

In a possible implementation, the secondary winding of the signal transformer extends out of two signal lines, which are coupled to the second power line by a capacitor, respectively. In one aspect, the two capacitors serve as signal transmission channels to transmit the PLC signal on the second power line to the signal transformer and then to the signal modulation circuit, or the two capacitors serve as signal transmission channels to transmit the PLC signal on the signal transformer to the second power line. On the other hand, the two capacitors have the characteristic of isolating the direct current from the direct current, and thus the current I2 output from the auxiliary source to the second power line can be prevented from flowing to the signal modulation circuit.

In a possible implementation manner, the signal modulation circuit receives a carrier communication signal transmitted by the other power device through the first power line.

In a possible implementation, the power device includes a power conversion circuit, and the current detection unit is located in the power conversion circuit. The current detection unit in the power conversion circuit is multiplexed, so that a plurality of devices are concentrated in one module, the structural compactness of the circuit single board is improved, and the structural design of the circuit single board is optimized.

In a second aspect, the present application provides a power line communication apparatus, where the power line communication apparatus includes a magnetic device, a signal modulation circuit, a current detection unit, an auxiliary source, a controller, a signal transformer, and a first power line, where the magnetic device is any one of a magnetic ring and a transformer; the power device communicates with other power devices through the first power line; the first power line is wound on one side of the magnetic device; the auxiliary source comprises a first output end and a second output end, one end of the second power line is connected with the first output end, the second power line is wound on the other side of the magnetic device, and the other end of the power line is connected with the second output end; the signal modulation circuit is coupled to the second power line through the signal transformer; the current detection unit is used for detecting a current I1 on the first power line; the controller is used for controlling the auxiliary source to output the I2 to the second power line, and the direction of the I2 is opposite to that of the I1. The magnetic flux generated by I2 and the magnetic flux generated by I1 are at least partially offset.

In a possible implementation manner, the signal transformer includes a primary winding and a secondary winding, an output end of the signal modulation circuit is coupled to the primary winding, the secondary winding is coupled to the second power line, and a ratio of a number of turns of the first power line wound on the magnetic device to a number of turns of the second power line wound on the magnetic device is the same as a ratio of numbers of turns of the primary winding and the secondary winding of the transformer.

In a possible implementation manner, the power line communication device includes a power conversion circuit, and the current detection unit is located in the power conversion circuit. The current detection unit in the power conversion circuit is multiplexed, so that a plurality of devices are concentrated in one module, the structural compactness of the circuit single board is improved, and the structural design of the circuit single board is optimized.

In a third aspect, the present application provides a photovoltaic system, the photovoltaic system comprising a plurality of electrical devices, wherein the power line communication device of the second aspect is disposed between every two electrical devices, and the medium-high frequency signal between every two electrical devices is transmitted by using a power line erected between the two electrical devices.

In a possible implementation, the power line communication device is located in the power equipment, for example, may be located in an inverter, and the inverter performs power line communication with other power equipment (such as an MPPT combiner box, a data collector, etc.) through the power line communication device.

In particular, electrical devices include, but are not limited to: photovoltaic module, dc-to-ac converter become, transformer, collection flow box, data acquisition ware. A power line communication device according to the second aspect may be provided between the photovoltaic module and the inverter, and the medium-high frequency signal between the photovoltaic array and the inverter may be transmitted using a power line interposed therebetween. A power line communication device as described in the first aspect may be provided between the transformer and the inverter; the medium-high frequency signals between the inverter and the transformer are transmitted by using a power line erected between the inverter and the transformer. A power line communication device according to the second aspect may be provided between a photovoltaic array and the junction box, and medium-high frequency signals between the photovoltaic array and the junction box are transmitted by power lines erected therebetween. The power line communication device according to the second aspect may be provided between a junction box and the inverter, and power line transmission may be provided between the junction box and the inverter. The data monitor is used for monitoring data of the photovoltaic array and the inverter; a power line communication device according to the second aspect is provided between the data monitor and at least one of the photovoltaic array and the inverter.

The power line communication device provided in the second aspect of the present application and the photovoltaic system provided in the third aspect of the present application may refer to the discussion about the beneficial effects of the first aspect, and are not repeated here.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments of the present application will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present disclosure;

FIG. 2 is a schematic view of another configuration of a photovoltaic system provided in an embodiment of the present application;

FIG. 3 is a schematic view of another configuration of a photovoltaic system provided in an embodiment of the present application;

fig. 4 is a schematic diagram of a prior art inverter;

fig. 5 is a schematic structural diagram of an inverter according to an embodiment of the present disclosure;

fig. 6 is a schematic diagram of another structure of an inverter provided in an embodiment of the present application;

fig. 7 is a schematic view of still another structure of an inverter provided in an embodiment of the present application;

fig. 8 is a schematic diagram of still another structure of an inverter provided in an embodiment of the present application;

fig. 9 is a schematic structural view of a photovoltaic system according to an embodiment of the present disclosure;

fig. 10 is a schematic view of another structure of the photovoltaic system according to the embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

The terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

In the implementation of the application, "and/or" describes the association relationship of the association objects, which means that three relationships may exist, for example, a and/or B may mean that a exists alone, a and B exist together, and B exists alone.

In the embodiments of the present application, words such as "exemplary" or "such as" are used to mean serving as examples, illustrations, or descriptions. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

In the description of the embodiments of the present application, unless otherwise indicated, the meaning of "a plurality" means two or more. For example, a plurality of cables refers to two or more cables; the plurality of devices means two or more devices.

For the purposes of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions in the present application will be clearly and completely described below with reference to the drawings in the present application, and it is apparent that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

Fig. 1 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present application. The photovoltaic system 100 shown in fig. 1 is a solar photovoltaic system. In fig. 1, the photovoltaic system includes a plurality of electric devices including a photovoltaic module 1, an inverter 2, a box transformer 3, and a data collector 4.

The photovoltaic module 1 may include a plurality of photovoltaic modules, and the plurality of photovoltaic modules are generally arranged in an array, which is also called a photovoltaic array. A photovoltaic module is a battery module that converts light energy into direct current electric energy to generate electricity when exposed to sunlight. In particular use, the photovoltaic modules are typically grouped to produce the required dc electrical energy. The inverter 2 is used for converting direct-current electric energy generated by the photovoltaic module into alternating-current electric energy. The tank transformer 3 is used for boosting the alternating current power generated by the inverter 2 and inputting the boosted alternating current power into the power grid 200 for power transmission. The data collector 4 is configured to collect data such as operating parameters and electric energy output of the photovoltaic module 1 and the inverter 2 through the low-voltage side of the box transformer 3, and then monitor the operating states of the photovoltaic module 1 and the inverter 2 (for example, monitor whether the inverter 2 is abnormal or not, control the inverter 2 to be turned on or off, etc.) based on the collected data. In the present embodiment, the inverter 2 may be a string inverter or a distributed inverter. Referring to fig. 2, when the inverter 2 is a distributed inverter, an MPPT (maximum power point tracking ) combiner box 5 is generally disposed between the photovoltaic module 1 and the inverter 2, and is configured to combine the direct current wires output by the photovoltaic module 1, perform direct current conversion, output the direct current signals to the inverter 2, and perform a maximum power tracking function.

Fig. 1 is a schematic structural view of a photovoltaic system including a string inverter, fig. 2 is a schematic structural view of a photovoltaic system including a distributed inverter, and fig. 3 is a schematic structural view of a photovoltaic system including a centralized inverter. In the photovoltaic system 100 shown in fig. 1-3, power lines for power transmission are also included. Specifically, a power line 01 for transmitting the direct current power generated by the photovoltaic module 1 to the inverter 2 is provided between the photovoltaic module 1 and the inverter 2 as shown in fig. 1; a power line 03 for transmitting direct current generated by the photovoltaic module to the MPPT combiner box is arranged between the photovoltaic module 1 and the MPPT combiner box 5 as shown in fig. 2, and a power line 04 for transmitting direct current converged by the MPPT combiner box to the inverter 2 is arranged between the MPPT combiner box 5 and the inverter 2; in the photovoltaic system 100 shown in fig. 1 or 2, a power line 02 for transmitting alternating current generated by the inverter 2 to the box-section 3 is provided between the inverter 2 and the box-section 3; a power line 05 is also provided between the data collector 4 and the inverter 2. The power lines 01, 03, 04 may be dc cables. The power lines 02, 05 may be ac cables.

In addition to the power transmission, signal transmission, i.e. data interaction, is usually performed between any two devices. In the long-distance signal transmission between devices, that is, when the distance between two devices is greater than 1KM, signal interaction is generally performed by adopting a PLC (power line communication ) or a carrier communication mode. That is, the distance between any two power devices included in the photovoltaic system shown in the application is larger, and when long-distance signal transmission is needed, a PLC transmission mode can be adopted. That is, the signal to be transmitted is modulated and then coupled to the power line for transmission (e.g., when the power line transmits dc power, the modulated signal is coupled to the positive cable and the negative cable for transmission; when the power line transmits ac power, the modulated signal is coupled to the live and neutral wires for transmission, or the modulated signal is coupled between the live and ground wires for transmission). Illustratively, when a signal is transmitted between MPPT combiner box 5 and inverter 2, such as when MPPT combiner box 5 sends a signal to inverter 2, the MPPT combiner box modulates the signal and then couples it to power line 04 to transmit the signal to inverter 2. After receiving the modulated signal, the inverter 2 demodulates the modulated signal to obtain data. Illustratively, when the inverter 2 sends a signal to the data collector 4, the inverter 2 modulates the signal and couples the modulated signal to the power line 05 to transmit the signal to the data collector 4, and the data collector 4 demodulates the modulated signal to obtain data.

In the existing PLC signal transmission technology, a capacitive direct coupling mode is commonly adopted in the existing coupling device, and the principle of the existing coupling device is mainly realized in that an inverter modulates a PLC signal and then directly connects the modulated PLC signal to a power line through a capacitor. However, the direct coupling mode of the capacitor has strict requirements on the type selection of the capacitor (for example, the impedance requirement of the PLC signal on the power line needs to be met, the PLC signal cannot be attenuated too much), and the voltage difference between the two power lines connected to the inverter can reach 1500V at maximum, so that the type selection of the capacitor also needs to meet the safety requirement so as to reduce the influence on a modulation circuit in the inverter.

In addition, a magnetic ring coupling mode is adopted in the existing PLC signal transmission technology. As shown in fig. 4, in the case of using PLC signals between the MPPT combiner box 5 and the inverter 2, a magnetic ring 10 is typically provided on one (positive or negative) of the power lines 04 on the MPPT combiner box 5 side. The signal input/output of MPPT combiner box 5 passes through the magnetic loop so that the signal input/output can couple a signal to power line 05 through magnetic loop 10. In general, MPPT combiner box 5 transmits a signal to inverter 2 by power line 04, and also transmits dc power by power line 04. Generally, as the current through the magnetic ring 10 increases, the magnetic induction of the magnetic ring 10 increases. When the magnetic induction intensity of the magnetic ring 10 is increased to a certain degree, the magnetic induction intensity is not increased along with the increase of the current. At this time, the magnetic field strength around the magnetic ring 10 continues to increase. Thus, the magnetic permeability of the magnetic ring 10 gradually decreases. The inductance of the magnetic ring 10 is proportional to the magnetic permeability, so that the inductance of the magnetic ring 10 gradually decreases until the magnetic ring 10 reaches magnetic saturation. At this time, the inductance of the magnetic ring 10 tends to be 0. The current transmitted in the photovoltaic system is generally high, which causes the inductance of the magnetic ring 10 to be attenuated sharply, and thus causes the transmitted signal to be attenuated, reducing the reliability of the transmitted signal.

The permeability μ is a physical quantity representing the magnetism of a magnetic medium, and represents resistance to magnetic flux generated by a current flowing through a space or a coil in a core space or its ability to conduct magnetic lines in a magnetic field. The calculation formula of the magnetic permeability mu is as follows: μ=b/H (B is magnetic induction, H is magnetic field). When the passing current is small, B also becomes larger as the current increases, and H is proportional to the current. When the current increases to a certain extent, B reaches a maximum value. That is, B does not increase when the current increases to some extent, i.e., the magnetic ring 10 reaches magnetic saturation with the increase in current, while H still increases, so that μ decreases. That is, the magnetic permeability μ gradually decreases as the current increases.

The magnetic ring inductance calculation formula is L=mu.N≡2A/L (wherein L represents magnetic ring inductance, mu represents magnetic permeability, N represents coil turns, A represents magnetic ring sectional area, and L represents magnetic path length), so that the magnetic ring inductance L is proportional to the magnetic permeability mu, the magnetic ring inductance L is gradually reduced along with the increase of current, and the attenuation of a PLC signal is caused.

When PLC signal transmission is performed in the high current scenario as shown above, a magnetic ring with higher initial permeability, that is, larger inductance is generally adopted, which results in larger volume of the magnetic ring, higher requirements on materials of the magnetic ring and magnetic ring technology, structural space pressure on design of products, and higher cost of the magnetic ring, thereby increasing the cost of PLC signal transmission and complexity and cost of space structure of the power system.

Based on the above PLC transmission mode, the inverter provided in the present application is used for PLC signal transmission between any two power devices of the above photovoltaic system 100. It should be noted that, the inverter provided in the application is not limited to PLC signal transmission between any two devices of the photovoltaic module 1, the inverter 2, the transformer 3, the data collector 4, and the MPPT combiner box 5 in the photovoltaic system 100, and may also be applied to PLC signal transmission between other devices not shown included in the photovoltaic system 100.

In the inverter provided by the application, the magnetic flux generated by the part I1 can be offset by applying the current I2 opposite to the current direction in the power line and the magnetic flux generated by the part I1, so that the signal attenuation caused by the magnetic flux generated by the magnetic device is reduced, the volume requirement on the magnetic device is reduced, and the stability of PLC signal transmission is improved.

The inverter shown in the present application will be specifically described below by way of the embodiment shown in fig. 5 to 8.

As shown in fig. 5, an inverter 2 includes a signal modulation circuit 210, a controller 220, an auxiliary source 230, a current detection unit 240, a transformer 250, a signal transformer 260, and a first power line 04. For convenience of distinction, the power lines are shown as solid lines in the drawing, and the signal lines are shown as broken lines in the drawing. The current detection unit 240 and the controller 220 perform signal transmission through a signal line 09, and the controller 220 and the signal modulation circuit 210 perform signal transmission through a signal line 08. The inverter communicates with the MPPT combiner box 5 through a power line 04, the power line 04 being used to transmit dc power. The power line 04 is wound on one side of the transformer 250, constituting a primary winding of the transformer 250. The auxiliary source 230 includes a first output terminal V231 and a second output terminal V232, one end of the power line 07 is connected to the first output terminal V31, a secondary winding of the transformer 250 is wound on the other side of the transformer 250, and the other end of the power line 07 is connected to the second output terminal V232. The signal modulation circuit 210 is coupled to the power line 07 through the signal transformer 260 and the signal line 011, and the signal modulation circuit 210 has a modulation and demodulation function of the PLC signal. The current detecting unit 240 is configured to acquire a current value I1 on the power line 04, and then send the value of I1 to the controller 220 through the signal line 010, and the controller 220 calculates a value of I2 according to the value of I1 and controls the auxiliary source 230 to output the current I2 to the power line 07.

It should be noted that the controller 220 may be a general-purpose central processing unit (central processing unit, CPU), a general-purpose processor, a digital signal processing unit (digital signal processing, DSP), an application specific integrated circuit (application specific integrated circuits, ASIC), a field programmable gate array (field programmable gate array, FPGA) or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. The above-described processors may also be a combination of computing functions. For example, the controller 220 may include one or more microprocessor combinations, a combination of a DSP and a microprocessor, or the like.

When communication is performed between the inverter 2 and the MPPT combiner box 5, the power line 04 is used to transmit DC power, and the auxiliary source 230 may be a DC/DC conversion circuit for outputting the DC power I2. If the data collector 4 and the inverter 2 communicate, the power line 05 therebetween is used for transmitting alternating current power, and the auxiliary source may be a DC/AC circuit for outputting alternating current I2.

On the one hand, the inverter 2 may receive PLC signals transmitted by other MPPT combiner boxes 5 through the power line 04. The MPPT combiner box 5 couples the PLC signal to the power line 04, and then couples the PLC signal to the power line 07 through the transformer 250, and then transmits the PLC signal to the signal modulation circuit 210 through the signal line 011 and the signal transformer 260, and the signal modulation circuit 210 demodulates the received PLC signal to obtain an original signal, and then transmits the original signal to the controller 220 through the signal line 08, thereby realizing communication between the inverter 2 and the MPPT combiner box 5.

On the other hand, inverter 2 may transmit a PLC signal to other MPPT combiner boxes 5 through power line 04. The controller 220 can transmit PLC signals to the signal modulation circuit 210 through the signal line 08, and the PLC signals are modulated by the signal modulation circuit 210 and then output to the signal transformer 260, and then coupled to the power line 07 through the signal line 011 to be transmitted to the transformer 250, and further transmitted to other MPPT combiner boxes 5 through the power line 04.

The magnetic flux is denoted by the letter Φ, which relates to the induction intensity B: Φ=b×s (S is the effective cross-sectional area of the magnetic path), it can be seen that the magnetic flux Φ and the magnetic induction B are in direct proportion. When the MPPT combiner box 5 transmits the PLC signal to the inverter 2 through the power line 04, the current I1 on the power line 04 generates a magnetic flux Φ1, and as the current increases, B increases until saturated, so Φ1 increases until saturated. The current detection unit 240 is configured to detect a current I1 on the power line 04, and the controller 220 controls the auxiliary source 230 to output I2 to the power line 07, where the direction of I2 is opposite to that of I1. The auxiliary source 230 outputs a current I2 to the power line 07 in the direction opposite to I1, and the flow directions of the currents I1 and I2 are shown with reference to the arrow directions in fig. 5. The reverse current I2 generates a reverse magnetic flux Φ2.Φ2 and Φ1 can at least partially cancel each other out. Therefore, the magnetic flux of the transformer 250 can be reduced, and the magnetic induction B of the transformer 250 can be reduced, so that the transformer 250 does not reach magnetic saturation, and μ cannot be excessively attenuated along with the increase of I1, so that the reduction of the inductance L is suppressed, and further, the signal attenuation is prevented. If the turns ratio of the primary winding and the secondary winding of the transformer 250 is 1:1, then Φ2 and Φ1 can be completely offset when the values of I2 and I1 are equal. Therefore, the magnetic permeability mu can be realized without excessively large attenuation along with the increase of I1, the requirements on the volume and the inductance of the magnetic device are further reduced, the volume of the power line communication equipment is reduced, and the material cost is reduced.

In other words, the ampere-turns of power line 04 wound on transformer 250 are the same as the ampere-turns of power line 07 wound on transformer 250. Ampere turns are engineering measurement units of magnetomotive force generated by a coil, fm=in (Fm is the ampere turn of the coil, N is the number of turns of the coil, and I is the current flowing through the coil), and the larger the ampere turn is, the stronger the generated magnetic field is. When the ampere-turns of the power line 04 wound on the transformer 250 are the same as the ampere-turns of the power line 07 wound on the transformer 250, the magnetic fluxes Φ1 and Φ2 generated by the I1 and I2 can be completely cancelled, and the effect of inhibiting the magnetic saturation of the transformer is better.

It should be noted that, the magnitude of the reverse current I2 may be dynamically adjusted by the controller 220, or may be obtained through a fixed setting. The magnetic flux phi 2 generated by the I2 and the magnetic flux phi 1 generated by the I1 can be mostly or completely counteracted, so that the magnetic permeability is realized without excessively attenuating along with the increase of the I1.

The signal transformer 260 includes a primary winding and a secondary winding, the output of the signal modulation circuit is coupled to the primary winding, the secondary winding is coupled to the power line 07, and the ratio of the number of turns of the power line 04 wound on the transformer 250 to the number of turns of the power line 07 wound on the magnetic device is the same as the ratio of the number of turns of the primary winding and the secondary winding of the signal transformer to achieve PLC signal conversion and impedance matching between the power line 04 and the power line 07. For example, when the number of turns of the power line 04 on one side of the transformer is 1 and the number of turns of the power line 07 on the other side of the transformer is N, the ratio of the number of turns of the primary winding and the secondary winding of the signal modulation circuit is also 1: n.

In addition, the secondary windings of the signal transformer 260 may be coupled to the power line 07 through capacitors C1, C2, respectively, C1 and C2 as signal transmission paths, and since the capacitors C1, C2 have a characteristic of blocking direct-current, the current I2 output from the secondary source 230 can be prevented from being transmitted to the signal modulation circuit 210 through the signal line 011.

In addition, a resistor R may be provided between the auxiliary source 230 and the transformer 250 to adjust the size of I2. Alternatively, R may be disposed within the secondary source 230.

It should be understood that the transformer 250 described above may be replaced by a magnetic ring. The schematic structure is shown in fig. 6. As shown in fig. 6, the power line 04 passes through the magnetic ring 270, at this time, the winding number of the power line 04 on the magnetic ring 270 is 1, the power line 07 is wound on the other side of the magnetic ring, and the winding number is N. The magnetic ring functions and the signal transmission manner are the same as the working principle of the transformer 250 in the embodiment shown in fig. 5, and play a role of electromagnetic coupling, which is not described herein.

Since the power lines have different winding patterns on the magnetic ring, the current directions of I1 and I2 are also understood differently. As shown in fig. 7, the power line 04 is wound on the magnetic ring 270, and the current direction of I1 and the current direction of I2 are opposite when the current directions of I1 and I2 flowing through the power line 04 and I2 of the power line 07 are on the same surface of the magnetic ring, so that the magnetic flux generated by I1 and the magnetic flux generated by I2 can at least partially cancel, and the magnetic saturation of the magnetic ring 270 is inhibited.

In addition, the current detecting unit 240 may be a separate component, for example, may be a current sensor, or may be located in the power conversion circuit 8 in the inverter 2, and the structure thereof is shown with reference to the schematic diagram of the inverter shown in fig. 8. Or, the current detecting device in the power conversion circuit 8 can be reused as a current detecting unit, so that a plurality of devices are concentrated in one module, the structural compactness of the circuit board is improved, and the structural design of the circuit board is optimized.

Based on the same inventive concept, the present application also provides a power line communication device, the structure of which can be referred to the example of the inverter 2 illustrated in fig. 5. The power line communication device comprises a magnetic device 250, a signal modulation circuit 210, a current detection unit 240, an auxiliary source 230, a controller 220, a signal transformer 260 and a power line 04, wherein the magnetic device is any one of a magnetic ring and a transformer, the power line communication device is communicated with other power equipment through the power line 04, the power line 04 is wound on one side of the magnetic device 250, the auxiliary source 230 comprises a first output end V31 and a second output end V232, one end of the power line 07 is connected with the first output end V31, the power line 07 is wound on the other side of the magnetic device 250, the other end of the power line 07 is connected with the second output end V232, the signal modulation circuit 210 is coupled to the power line 07 through the signal transformer 260, the current detection unit 240 is used for detecting a current I1 on the power line 04, and the controller 220 is used for controlling the auxiliary source 230 to output I2 to the power line 07, and the I2 is opposite to the I1. The magnetic flux generated by I2 at least partially cancels the magnetic flux generated by I1. The signal transformer 260 includes a primary winding and a secondary winding, the output of the signal modulation circuit 210 is coupled to the primary winding, the secondary winding is coupled to the power line 07, and the ratio of the number of turns of the power line 04 wound on the magnetic device 250 to the number of turns of the power line 07 wound on the magnetic device 250 is the same as the ratio of the number of turns of the primary winding and the secondary winding of the transformer.

Based on the same inventive concept, the embodiment of the application also provides a photovoltaic system, which comprises a plurality of electric devices, wherein the inverter is arranged between every two electric devices, and medium-high frequency signals between every two electric devices are transmitted by using a power line erected between the two electric devices. The schematic structure of the photovoltaic system can be seen with reference to fig. 1-3.

Fig. 9 and 10 show a schematic structural view of an inverter located between one inverter 2 and two MPPT combiner boxes 5. The embodiment shown in fig. 9 uses transformer coupling for PLC signaling. When the inverter transmits PLC signals to the MPPT combiner box 51 and the MPPT combiner box 52, the controller 202 transmits signals to the signal modulation circuit 201, the signal modulation circuit 201 modulates the signals and transmits the signals to the power line 063 through the signal transformer 206, the signals are coupled to the transformer 205 through the power line 063, the signals are coupled to the power line 041 through the transformer 205, and the signals are respectively transmitted to the MPPT combiner box 51 and the MPPT combiner box 52 through the power line 041. The power lines 041 and 042 are respectively negative and positive cables for transmitting dc power. The transformer 515 located inside the MPPT combiner box 51 receives the modulated signal transmitted from the inverter 2 through the power line 044, and transmits the modulated signal to the signal modulation circuit 511 through the power line 061 and the signal transformer 515, and the signal modulation circuit 511 demodulates the modulated signal to obtain an original signal. The transformer 525 located inside the MPPT combiner box 52 receives the modulated signal transmitted by the inverter 2 through the power line 041, and transmits the modulated signal to the signal modulation circuit 521 through the power line 062 and the signal transformer 25026, and the signal modulation circuit 521 demodulates the modulated signal to obtain an original signal. During signal transmission, the current detection unit detects the current values I1 and I1' on the power line 041 and 044, and the auxiliary source in the inverter 2 outputs a current I2 opposite to the current direction I1 to the power line 063, and the magnetic flux generated by I2 and the magnetic flux generated by I1 at least partially cancel each other, so that the magnetic saturation of the transformer 205 is suppressed, and the inductance attenuation of the transformer 205 is suppressed. The auxiliary source 523 located in the MPPT combiner box 52 outputs a current I3 opposite to the current I1 to the power line 062, and the magnetic flux generated by I3 at least partially cancels the magnetic flux generated by I1, thereby suppressing the magnetic saturation of the transformer 525 and thus suppressing the inductance attenuation of the transformer 525. The auxiliary source 513 located in the MPPT combiner box 51 outputs a current I4 opposite to the current I1 to the power line 061, and the magnetic flux generated by I4 and the magnetic flux generated by I1' at least partially cancel each other, so as to inhibit the magnetic saturation of the transformer 515, thereby inhibiting the inductance attenuation of the transformer 515.

The embodiment shown in fig. 10 adopts a magnetic ring coupling manner to perform PLC signal transmission, and the PLC signal transmission manner and principle thereof can refer to the PLC signal transmission manner and principle of the embodiment shown in fig. 9, which are not described herein.

The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present application, and the changes and substitutions are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An inverter is characterized by comprising a magnetic device, a signal modulation circuit, a current detection unit, an auxiliary source, a controller, a signal transformer and a first power line;

the inverter is used for communicating with other power equipment through the first power line;

the first power line is wound on one side of the magnetic device;

the auxiliary source comprises a first output end and a second output end, one end of the second power line is connected with the first output end, the second power line is wound on the other side of the magnetic device, and the other end of the second power line is connected with the second output end;

the signal modulation circuit is coupled to the second power line through the signal transformer;

the current detection unit is used for detecting a current I1 on the first power line;

the controller is used for controlling the current output unit to output a current I2 to the second power line, and the direction of the I2 is opposite to that of the I1.

2. The power line communication device of claim 1, wherein the magnetic flux generated by I2 at least partially cancels out of the magnetic flux generated by I1.

3. The inverter of claim 1 or 2, wherein the signal transformer comprises a primary winding and a secondary winding, an output of the signal modulation circuit being coupled to the primary winding, the secondary winding being coupled to the second power line;

the ratio of the number of turns of the first power wire wound on the magnetic device to the number of turns of the second power wire wound on the magnetic device is the same as the ratio of the number of turns of the primary winding and the secondary winding of the transformer.

4. An inverter according to any one of claims 1-3, wherein the ampere-turns of the first power wire wound on the magnetic device are the same as the ampere-turns of the second power wire wound on the magnetic device.

5. An inverter according to claim 3, wherein the secondary winding of the signal transformer extends over two signal lines, each of the two signal lines being capacitively coupled to the second power line.

6. The inverter of claim 1, wherein the signal modulation circuit receives carrier communication signals transmitted by the other power devices over the first power line.

7. The inverter of claim 6, wherein the inverter comprises a power conversion circuit, the current detection unit being located in the power conversion circuit.

8. The power line communication device is characterized by comprising a magnetic device, a signal modulation circuit, a current detection unit, an auxiliary source, a controller, a signal transformer and a first power line, wherein the magnetic device is any one of a magnetic ring and a transformer;

the electric power line communication device communicates with other electric power equipment through the first power line;

the first power line is wound on one side of the magnetic device;

the auxiliary source comprises a first output end and a second output end, one end of the second power line is connected with the first output end, the second power line is wound on the other side of the magnetic device, and the other end of the power line is connected with the second output end;

the controller is used for controlling the auxiliary source to output the I2 to the second power line, and the direction of the I2 is opposite to that of the I1.

9. The power line communication device of claim 8, wherein the signal transformer comprises a primary winding and a secondary winding, an output of the signal modulation circuit being coupled to the primary winding, the secondary winding being coupled to the second power line;

10. A photovoltaic system comprising a plurality of electric devices, wherein the power line communication device according to claim 8 or 9 is provided between each two of the electric devices, and wherein the medium-high frequency signal between each two of the electric devices is transmitted by using a power line interposed therebetween.