A photovoltaic inverter

Abstract

The present invention provides a photovoltaic inverter, including a first switch group, a second switch group, a DC / DC power conversion circuit, a bus capacitor, a switch state detection circuit and a controller. Among them, one end of the first switch group is used to be connected to the first photovoltaic string, and the other end of the first switch group is used to be connected to the bus capacitor, so that when the first switch group is closed, the controller is powered by the bus capacitor. One end of the second switch group is used to be connected to the second photovoltaic string, and the other end of the second switch group is used to be connected to the input end of the DC / DC power conversion circuit, and the second photovoltaic string includes the first photovoltaic string. After the controller has been powered on and the second switch group has been closed, the switch state detection circuit is used to detect the closed or turned-off state of the first switch group. If the first switch group is still closed, the controller is used to send an alarm signal, and the alarm signal is used to prompt the user to disconnect the first switch group. In this way, the user can be reminded to disconnect the first switch group in time, thereby improving the safety of the photovoltaic power station.

Description

Technical Field

[0001] The present application relates to the field of renewable energy power generation, and in particular to a photovoltaic inverter. Background Art

[0002] In recent years, solar energy has been widely used as a clean and renewable energy source. In a photovoltaic power station, photovoltaic modules convert solar energy into direct current through the photovoltaic effect, and transmit the direct current to the photovoltaic inverter, which further converts the direct current into alternating current with the same frequency as the mains. During the operation of a photovoltaic power station, some photovoltaic strings may have short circuit faults due to long-term exposure to the outdoors. If the photovoltaic inverter cannot identify and eliminate the short circuit fault of the photovoltaic string in time, it may cause the photovoltaic string or even the inverter to burn out, seriously affecting the safety of the photovoltaic power station. Summary of the invention

[0003] The embodiments of the present application provide a photovoltaic inverter that can promptly identify and eliminate short-circuit faults of photovoltaic modules, so as to improve the safety and reliability of photovoltaic power stations.

[0004] In a first aspect, an embodiment of the present application provides a photovoltaic inverter, including a first switch group, a second switch group, a DC / DC power conversion circuit, a bus capacitor, a switch state detection circuit, and a controller. Among them, the first switch group does not have a remote disconnection capability, one end of the first switch group is used to connect to the first photovoltaic string, and the other end of the first switch group is used to connect to the bus capacitor, so that when the first switch group is closed, the controller is powered from the bus capacitor. The second switch group has a remote disconnection capability, one end of the second switch group is connected to the second photovoltaic string, and the other end of the second switch group is connected to the DC input end of the DC / DC power conversion circuit. The first photovoltaic string is part of the second photovoltaic string. The DC output end of the DC / DC power conversion circuit is connected to the bus capacitor. After the controller is powered on and the second switch group is closed, the switch state detection circuit is used to detect the closed or off state of the first switch group. If the first switch group is still closed, the controller is used to send an alarm signal, and the alarm signal is used to prompt the user to disconnect the first switch group.

[0005] In practical applications, for cost considerations, the second switch group has remote disconnection capability, while the first switch group usually does not have remote disconnection capability. In other words, the second switch group can receive the disconnection signal sent to it by the controller, and then disconnect the corresponding switch in the second switch group in time when the current flowing through the second switch group is abnormal. In contrast, the first switch group cannot be controlled by the controller. When the current flowing through the first switch group is abnormal, the first switch group can only be disconnected manually.

[0006] Specifically, before the photovoltaic inverter is connected to the grid, the user first closes the first switch group to power the first photovoltaic component to the DC bus or bus capacitor. With this arrangement, the auxiliary source can draw power from the DC bus or bus capacitor and power the controller to enable the controller to work normally. After the controller works normally, the user closes the second switch group to input the power of the second photovoltaic string into the photovoltaic inverter. After the second switch group is closed, if the second photovoltaic string connected to the photovoltaic inverter is reversely connected, or if the current flowing through some switches in the second switch group is overcurrent, the controller can identify it in time and disconnect the corresponding switch in the second switch group connected in series with the reversed photovoltaic string. However, after the controller is powered on and the second switch group is closed, if the user does not disconnect the first switch group for a long time, once a short circuit fault occurs inside the photovoltaic inverter, the controller cannot identify and disconnect the first switch group in time, resulting in long-term abnormal current flowing through the first photovoltaic string, and in severe cases, it may even cause the first photovoltaic string and the photovoltaic inverter to catch fire and explode.

[0007] Therefore, after the controller is powered on and the second switch group is closed, by setting a switch status detection circuit, the controller can obtain the closed or off status of the first switch group in real time, and promptly issue an alarm signal when the first switch group is closed, thereby reminding the user to disconnect the first switch group, thereby improving the safety and reliability of the photovoltaic power station.

[0008] In practical applications, the second photovoltaic string is generally connected in series with the second switch group through the DC port of the photovoltaic inverter. It is worth mentioning that in this application, the DC port is a general term for function, and a DC port can be further divided into a positive port and a negative port, wherein the positive port is used to connect the positive pole of one or more photovoltaic strings, and the negative port is used to connect the negative pole of one or more photovoltaic strings.

[0009] The present application does not limit the number of switches in the first switch group, that is, there is at least one switch on the connection line between the first photovoltaic string and the DC / DC power converter, and the switch can achieve the effect of connecting and disconnecting the first photovoltaic string. For example, a switch can be connected in series at the positive output end of the first photovoltaic string, or a switch can be connected in series at the negative output end of the first photovoltaic string. Of course, switches can also be connected in series at both the positive output end and the negative output end of the first photovoltaic string, and the present application does not limit this.

[0010] The present application does not limit the number of switches in the second switch group, that is, there is at least one switch on the connection line between each port and the DC / DC power converter, and the details are not repeated here.

[0011] It is worth mentioning that the other end of the first switch group is used to connect to the bus capacitor, which means that the electric energy generated by the first photovoltaic string can be used to charge the bus capacitor through the first switch group, and then the bus capacitor can power the controller. In practical applications, there may be other components between the first switch group and the bus capacitor, such as a DC / DC power converter, etc., which is not limited in this application.

[0012] In one possible implementation, the photovoltaic inverter includes an anti-reverse circuit, wherein the anti-reverse circuit is connected in series with the first switch group and connected between the first photovoltaic string and the bus capacitor, and the anti-reverse circuit is used to prevent reverse current from entering the bus capacitor when the first switch group is closed and the first photovoltaic string is reversely connected. For example, one end of the anti-reverse circuit is used to be connected to the first switch group, and the other end of the anti-reverse circuit is used to be connected to the bus capacitor, or one end of the anti-reverse circuit is used to be connected to the first photovoltaic string, and the other end of the anti-reverse circuit is used to be connected to the first switch group. By setting the anti-reverse circuit, it can be ensured that the first photovoltaic component can be correctly connected to the photovoltaic inverter to charge the DC bus.

[0013] In a possible implementation, one end of the anti-reverse circuit is connected to the DC input end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to connect to the first photovoltaic string, and the switch state detection circuit is used to detect the voltage between the first detection point and the second detection point. Among them, the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor, one of the first detection point and the second detection point is located between the first photovoltaic string and the first switch group, and the other of the first detection point and the second detection point is located between the first switch group and the DC input end of the DC / DC power conversion circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal. Among them, when the anti-reverse circuit is connected to the DC input end of the DC / DC power conversion circuit, part of the circuit of the DC / DC power conversion circuit can be reused, thereby reducing the use of wires and optimizing the internal space of the photovoltaic inverter.

[0014] Such an arrangement can improve the detection accuracy of the voltage between the first detection point and the second detection point, and avoid the influence of the voltage at both ends of the first photovoltaic string and the voltage at the DC input end of the DC / DC power conversion circuit on the detection accuracy.

[0015] In a possible implementation, one end of the anti-reverse circuit is connected to the DC output end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to connect to the first photovoltaic string, and the switch state detection circuit is used to detect the voltage between the first detection point and the second detection point. Among them, the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor, one of the first detection point and the second detection point is located between the first photovoltaic string and the first switch group, and the other of the first detection point and the second detection point is located between the first switch group and the DC output end of the DC / DC power conversion circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

[0016] Such an arrangement can improve the detection accuracy of the voltage between the first detection point and the second detection point, and avoid the influence of the voltage at both ends of the first photovoltaic string and the voltage at the DC output end of the DC / DC power conversion circuit on the detection accuracy.

[0017] In a possible implementation, one end of the first switch group is connected to the DC input end of the DC / DC power conversion circuit through an anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string, and the switch state detection circuit is used to detect the voltage between the first detection point and the second detection point. Among them, the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor, and at least one of the first detection point and the second detection point is located between the first switch group and the anti-reverse circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

[0018] Such an arrangement can improve the detection accuracy of the voltage between the first detection point and the second detection point, and avoid the influence of the voltage at both ends of the first photovoltaic string and the voltage at the DC input end of the DC / DC power conversion circuit on the detection accuracy.

[0019] In a possible implementation, one end of the first switch group is connected to the DC output end of the DC / DC power conversion circuit through an anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string, and the switch state detection circuit is used to detect the voltage between the first detection point and the second detection point. Among them, the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor, and at least one of the first detection point and the second detection point is located between the first switch group and the anti-reverse circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

[0020] Such an arrangement can improve the detection accuracy of the voltage between the first detection point and the second detection point, and avoid the influence of the voltage at both ends of the first photovoltaic string and the voltage at the DC output end of the DC / DC power conversion circuit on the detection accuracy.

[0021] In a possible implementation, one end of the anti-reverse circuit is connected to the DC input end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to be connected to the first photovoltaic string, and the switch state detection circuit is used to detect the current flowing through the third detection point. The third detection point is located between the first photovoltaic string and the first switch group. When the first switch group is closed, the current flowing through the third detection point is greater than the current setting threshold, and the controller is used to send an alarm signal, wherein the current setting threshold is greater than zero and less than the current of the DC input end of the DC / DC power conversion circuit.

[0022] Such an arrangement can improve the current detection accuracy of the third detection point and avoid the influence of the DC input terminal current of the DC / DC power conversion circuit on the detection accuracy.

[0023] In a possible implementation, one end of the first switch group is connected to the DC input end of the DC / DC power conversion circuit through an anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string, and the switch state detection circuit is used to detect the current flowing through the third detection point. The third detection point is located between the first photovoltaic string and the anti-reverse circuit. When the first switch group is closed, the current flowing through the third detection point is greater than the current setting threshold, and the controller is used to send an alarm signal, wherein the current setting threshold is greater than zero and less than the current of the DC input end of the DC / DC power conversion circuit.

[0024] Such an arrangement can improve the current detection accuracy of the third detection point and avoid the influence of the DC input terminal current of the DC / DC power conversion circuit on the detection accuracy.

[0025] In one possible implementation, the first switch group includes an auxiliary contact switch and a main contact switch. The closed and open states of the auxiliary contact switch are the same as those of the main contact switch. One end of the main contact switch is used to be connected to the first photovoltaic string, and the other end of the main contact switch is used to be connected to the bus capacitor. The auxiliary contact switch is connected to the switch state detection circuit. When the auxiliary contact switch is closed, the controller is used to send an alarm signal.

[0026] Specifically, the closed and open states of the main contact switch in the first switch group determine whether the electric energy generated by the first photovoltaic string can be smoothly transmitted to the bus capacitor, and the auxiliary contact switch in the first switch group is mainly used to reflect the closed or open state of the main contact switch. In other words, when the main contact switch is closed, the DC power output by the first photovoltaic string will flow through the main contact switch but not through the auxiliary contact switch.

[0027] With such an arrangement, the switch state detection circuit can indirectly obtain the closed and open states of the main contact switch, thereby avoiding a large current from flowing through the switch state detection circuit, ensuring the detection accuracy of the switch state detection circuit, and reducing the failure probability of the switch state detection circuit.

[0028] In one possible implementation, the switch state detection circuit includes a second resistor, a third resistor and an operational amplifier, one end of the second resistor is used to be connected to a stable voltage source, the other end of the second resistor is used to be connected to an analog ground through the third resistor, the series connection point of the second resistor and the third resistor is used to be connected to the analog ground through an auxiliary contact switch, the series connection point of the second resistor and the third resistor is also used to be connected to an input end of the operational amplifier, and the output end of the operational amplifier is connected to a controller.

[0029] In a possible implementation, when the auxiliary contact switch is closed, the series connection point of the second resistor and the third resistor outputs zero voltage to the operational amplifier, the operational amplifier is used to output a zero level to the controller, and the controller is used to send an alarm signal.

[0030] With such arrangement, as the closing and opening states of the auxiliary contact switch, i.e., the first switch group, change, the voltage outputted to the operational amplifier by the series connection point of the second resistor and the third resistor will also change, thereby enabling the controller to know whether the first switch group is closed, and to promptly send out an alarm signal when the first switch group is closed, to remind the user to disconnect the first switch group.

[0031] In a possible implementation, the photovoltaic inverter includes an indicator light, and if the first switch group is closed so that the controller is powered on by obtaining power from the bus capacitor, the indicator light is on, and the indicator light is used to instruct the user to close the second switch group. After the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to control the color change of the indicator light, and the controller is used to control the flashing frequency change of the indicator light.

[0032] With this arrangement, after the DC power of the second PV string is normally transmitted to the PV inverter, the change in the indicator light status can effectively remind the user to manually disconnect the first switch group. Later, even if a short circuit or overcurrent fault occurs in the first PV string, the second switch group can promptly and reliably eliminate the fault, thereby improving the safety and reliability of the PV system.

[0033] In a possible implementation, the photovoltaic inverter includes a warning light, and after the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to control the warning light to light up.

[0034] With this arrangement, after the DC power of the second PV string is normally transmitted to the PV inverter, the lit warning light can effectively remind the user to manually disconnect the first switch group. Later, even if a short circuit or overcurrent fault occurs in the first PV string, the second switch group can promptly and reliably eliminate the fault, thereby improving the safety and reliability of the PV system.

[0035] In a possible implementation, after the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to send an alarm signal to a client or a host computer.

[0036] With this arrangement, after the DC power of the second PV string is normally transmitted to the PV inverter, the alarm signals of the client and the host computer can effectively remind the user to manually disconnect the first switch group. Later, even if a short circuit or overcurrent fault occurs in the first PV string, the second switch group can promptly and reliably eliminate the fault, thereby improving the safety and reliability of the PV system.

[0037] In a possible implementation, the anti-reverse circuit includes one or more diodes, and the conduction direction of the diode is opposite to the direction of the reverse current.

[0038] In general, the photovoltaic inverter provided in the present application can timely and accurately identify the status of the first switch group through a simple circuit setting, and send an alarm signal when the first switch group is closed to remind the user to disconnect the first switch group, thereby significantly improving the safety and reliability of the photovoltaic power station. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1This is a network diagram of the optical storage system;

[0040] Figure 2a The current flow diagram when the photovoltaic string provided for this application is normally connected;

[0041] Figure 2b A current flow diagram for some photovoltaic strings reversely connected provided for this application;

[0042] Figure 2c The current flow diagram for all photovoltaic strings provided in this application when they are reversely connected;

[0043] Figure 3 A topological diagram of the DC side of a photovoltaic inverter capable of protecting photovoltaic strings provided in this application;

[0044] Figure 4a-4d Several topological diagrams of the DC side of photovoltaic inverters capable of protecting photovoltaic strings provided for this application;

[0045] Figure 5 A topological diagram of the DC side of a photovoltaic inverter capable of protecting photovoltaic strings provided in this application;

[0046] Figure 6a-6d Several topological diagrams of the DC side of photovoltaic inverters capable of protecting photovoltaic strings provided for this application;

[0047] Figures 7a-7d Several topological diagrams of the DC side of the photovoltaic inverter provided in this application that can identify the closed and closed states of the first switch group;

[0048] Figure 8 A topological diagram of the DC side of a photovoltaic inverter capable of identifying the closed and closed states of a first switch group provided in the present application;

[0049] Figure 9a-9b Two topological diagrams of the DC side of the photovoltaic inverter capable of identifying the closed and closed states of the first switch group provided in this application; DETAILED DESCRIPTION

[0050] See also Figure 1 , Figure 1 This is a networking diagram of a photovoltaic storage system in an AC coupling scenario, in which photovoltaic modules convert solar energy into DC power through the photovoltaic effect, and the inverter converts the DC power output by the photovoltaic modules into AC power and further transmits the AC power to the box-type substation. After the box-type substation converts the low-voltage AC power output by the inverter into medium-voltage AC power, it further transmits the AC power to the booster station (grid) or the box-type substation corresponding to the energy storage system. The energy storage system is used to store unstable electrical energy from photovoltaic modules and output stable electrical energy to the grid through the energy storage inverter and the corresponding box-type substation.

[0051] When the PV inverter is connected to the grid for the first time, there may be some or all PV strings that are reversely connected. If not identified and handled in time, it may cause damage to the PV strings or even the PV inverter. Figure 2a , Figure 2b and Figure 2c The flow direction of DC power is analyzed when all PV strings are connected normally, when some PV strings are connected in reverse, and when all PV strings are connected in reverse.

[0052] First, see Figure 2a , Figure 2a The figure is a flow diagram of the direct current generated by the photovoltaic strings when all photovoltaic strings are normally connected to the photovoltaic inverter. Among them, multiple photovoltaic strings are connected in parallel to the direct current / direct current (DC / DC) conversion circuit of the photovoltaic inverter through the DC side switch 10 of the photovoltaic inverter. The number of photovoltaic strings connected to the photovoltaic inverter is n, and n is a positive integer greater than or equal to 1. It is worth mentioning that a photovoltaic string may include one or more photovoltaic panels, and each photovoltaic panel is composed of multiple photovoltaic cells. PVn+ represents the positive pole of photovoltaic string n, and PVn- represents the negative pole of photovoltaic string n. When the photovoltaic module generates direct current, the direct current flows out from PVn+, and passes through the DC / DC conversion circuit and the positive DC bus in turn to charge the bus capacitors C1 and C2, and finally flows into PVn- through the negative DC bus to realize the current loop. It should be noted that, except for Figure 2a In addition to the DC side switch 10, the DC / DC conversion circuit and the bus capacitors C1 and C2 shown in the figure, in actual application, the photovoltaic inverter also includes Figure 2a The DC / AC conversion circuit, LCL filter, relay, etc. not shown are not described in detail in this application.

[0053] Below, see Figure 2b , Figure 2b The figure is the flow diagram of the direct current generated by the photovoltaic strings when some photovoltaic strings are reversely connected. Among them, the photovoltaic strings that are reversely connected are photovoltaic strings 1 and photovoltaic strings 2, that is, Figure 2aIn comparison, PV1+ and PV1- are swapped, and PV2+ and PV2- are also swapped. In this case, when the DC side switch 10 of the photovoltaic inverter is closed, the DC power generated from PV(n-2)+ to PVn+ will be directly injected into PV1- and PV2-, and the DC power flowing out of PV1+ and PV2+ will enter PV(n-2)- to PVn-, forming a current loop (the current in this current loop is called reverse current), which will cause the DC bus to lose power, making it impossible for the auxiliary source of the photovoltaic inverter to draw power from the DC bus or from the bus capacitor and power the controller. Therefore, the controller of the photovoltaic inverter cannot promptly identify whether the photovoltaic string is reversely connected, and which photovoltaic string is reversely connected. Of course, the controller cannot promptly disconnect the switch in the DC side switch 10 of the photovoltaic inverter that is connected in series with the reverse photovoltaic string to eliminate the fault.

[0054] Continue to see Figure 2c , Figure 2c This is the flow diagram of the DC power generated by the photovoltaic strings when all photovoltaic strings are reversely connected. Figure 2a In comparison, PVn+ and PVn- are swapped. In this case, when the DC side switch 10 of the photovoltaic inverter is closed, the DC power generated from PV1+ to PVn+ passes through the diode D1 in the Boost circuit of the DC / DC (direct current / direct current, DC / DC) conversion circuit, which is anti-parallel to the switch tube V1, forming a short circuit loop, which will also cause the DC bus to lose power, so that the auxiliary source of the inverter cannot take power from the DC bus or from the bus capacitor and power the controller. Similarly, the controller of the inverter cannot timely identify whether the photovoltaic string is reversely connected, and the specific location of the reverse connection of the photovoltaic string. Of course, the controller cannot timely disconnect the switch in the DC side switch 10 of the photovoltaic inverter that is connected in series with the reverse photovoltaic string, thereby eliminating the reverse connection fault.

[0055] The following will be specifically combined with the attached Figure 3 To Attachment Figure 6d , the embodiments of the present application are introduced and described.

[0056] First, see Figure 3 , Figure 3A topological diagram of the DC side of a photovoltaic inverter that can timely protect photovoltaic strings is provided in the present application. Specifically, the first photovoltaic string (PV1) is connected to the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11, and the second photovoltaic string (the first photovoltaic string PV1 to the nth photovoltaic string PVn, n is greater than or equal to 2) is connected to the DC / DC power conversion circuit 12 through the second switch group S2, wherein the first photovoltaic string PV1 is part of the second photovoltaic string. It is worth mentioning that, for cost considerations, the first switch group S1 usually does not have remote disconnection capability, while the second switch group S2 has remote disconnection capability. In other words, the second switch group S2 can receive a disconnection signal sent to it by a controller (not shown), and then disconnect the corresponding switch in the second switch group S2 in time when the current flowing through the second switch group S2 is abnormal. In contrast, the first switch group S1 cannot be controlled by the controller, and when the current flowing through the first switch group S1 is abnormal, the first switch group S1 can only be manually disconnected. The working principle of this topology is: before the photovoltaic inverter is connected to the grid, the user first needs to close the first switch group S1. If the connection of the first photovoltaic string PV1 is normal, that is, the first photovoltaic string PV1 is not reversely connected, the anti-reverse circuit 11 can be turned on normally, the DC bus and the bus capacitors C1 and C2 are powered on, so that the auxiliary source (not shown) draws power from the DC bus or the bus capacitors C1 and C2 and supplies power to the controller. Then, the user closes the second switch group S2. At this time, since the controller is powered on, the controller can determine in real time whether there is a reverse-connected photovoltaic string in the second photovoltaic string connected to the DC / DC power conversion circuit 12. If there is a reverse-connected photovoltaic string in the second photovoltaic string, the controller can disconnect the switch in the second switch group S2 that is connected in series with the reverse-connected photovoltaic string, thereby eliminating the reverse connection fault. If the second photovoltaic strings are all connected to the photovoltaic inverter normally, the user needs to continue to disconnect the first switch group S1. The specific reasons will be described in detail below.

[0057] exist Figure 3 In the embodiment, the first photovoltaic string PV1 is connected to the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. In practical applications, the first photovoltaic string PV1 can also be connected to the DC / DC power conversion circuit 12 through the anti-reverse circuit 11 and the first switch group S1.

[0058] It should also be noted that in Figure 3In the embodiment, the first switch group S1 includes two switches, wherein the two switches are respectively connected to the anti-reverse circuit 11 through the positive pole PV1+ of the first photovoltaic string and the negative pole PV1- of the first photovoltaic string. In practical applications, the number of switches in the first switch group S1 is not limited to two, that is, the number of switches in the first switch group S1 can be one or more, and the present application does not impose any restrictions on this. When there is only one switch in the first switch group S1, the switch can be connected to the positive pole PV1+ of the first photovoltaic string or to the negative pole PV1- of the first photovoltaic string, and the present application does not impose any restrictions on this. Based on the same principle, the present application does not impose any restrictions on the number of switches in the second switch group S2, that is, there can be one switch or multiple switches on the connection line between each photovoltaic string and the DC / DC power conversion circuit 12.

[0059] Next, we will combine Figure 4a , specifically showing a structure of the anti-reverse circuit 11. Among them, the anti-reverse circuit 11 includes a first resistor R1 and a diode D1, one end of the first resistor R1 is connected to the positive pole PV1+ of the first photovoltaic string, the other end of the first resistor R1 is connected to the DC input end of the DC / DC power conversion circuit 12, the anode of the diode D1 is connected to the DC input end of the DC / DC power conversion circuit 12, and the cathode of the diode D1 is connected to the negative pole PV1- of the first photovoltaic string. Such a setting can ensure that the first photovoltaic string PV1 is normally connected to the photovoltaic inverter, avoid reverse current from entering the bus capacitors C1 and C2, and enable the controller to obtain power supply normally and power on. Based on the same principle, the structure of the anti-reverse circuit 11 can also refer to Figure 4b .and Figure 4a The structure shown is different in that Figure 4b In the embodiment, the anode of the diode D1 is connected to the positive electrode PV1+ of the first photovoltaic string, the cathode of the diode D1 is connected to the DC input end of the DC / DC power conversion circuit 12, one end of the first resistor R1 is connected to the negative electrode PV1- of the first photovoltaic string, and the other end of the first resistor R1 is connected to the DC input end of the DC / DC power conversion circuit 12.

[0060] Next, we will combine Figure 4c , specifically showing another structure of the anti-reverse circuit 11. Figure 4a and Figure 4b The structure shown is different in that Figure 4cThe anti-reverse circuit 11 shown includes two diodes, namely, a diode D1 and a diode D2, wherein the anode of the diode D1 is connected to the positive electrode PV1+ of the first photovoltaic string, the cathode of the diode D1 is connected to the DC / DC power conversion circuit 12, the anode of the diode D2 is connected to the DC / DC power conversion circuit 12, and the cathode of the diode D2 is connected to the negative electrode PV1- of the first photovoltaic string. By arranging two diodes in the anti-reverse circuit 11, even if one of the two diodes has a short-circuit fault, the anti-reverse circuit 11 can still work, that is, it is ensured that the current output by the first photovoltaic string can flow through the DC bus and the bus capacitors C1 and C2, and then the controller is powered on through the auxiliary source, so that the controller has the ability to identify the reverse connection fault of the photovoltaic string.

[0061] Next, we will combine Figure 4d , specifically showing another structure of the anti-reverse circuit 11. Figure 4a , Figure 4b and Figure 4c The structure shown is different in that Figure 4d The anti-reverse circuit 11 shown is a full-bridge circuit. Specifically, the anti-reverse circuit 11 includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm includes a diode D1 and a diode D2 connected in series, and the second bridge arm includes a diode D3 and a diode D4 connected in series, wherein the positive electrode PV1+ of the first photovoltaic string is connected to the series connection point of the diode D1 and the diode D2 through the first switch group S1, the negative electrode PV1- of the first photovoltaic string is connected to the series connection point of the diode D3 and the diode D4 through the first switch group S1, the cathode of the diode D1 is connected to the cathode of the diode D3, and the parallel connection point of the diode D1 and the diode D3 is connected to the DC / DC power conversion circuit 12, the anode of the diode D2 is connected to the anode of the diode D4, and the parallel connection point of the diode D2 and the diode D4 is connected to the DC / DC power conversion circuit 12. Such a setting can also ensure that the current output by the first photovoltaic string can flow through the DC bus and the bus capacitors C1 and C2, and then the controller is powered on through the auxiliary source, so that the controller has the ability to identify the reverse connection fault of the photovoltaic string. same Figure 4c The structure shown is similar in that even if one of the diodes D1 and D4 has a short circuit fault, the anti-reverse circuit 11 can still work normally. At the same time, it is worth mentioning that in actual applications, resistors can also be connected in series on the first bridge arm and the second bridge arm to achieve the function of current limiting, and this application does not limit this.

[0062] In the above embodiment, the first photovoltaic string PV1 is connected to the input end of the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. In practical applications, the first photovoltaic string PV1 can also be connected to the output end of the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. Figure 5 and Figure 6a-6d The embodiments of the present application are described.

[0063] See also Figure 5 , Figure 5 A topological diagram of the DC side of a photovoltaic inverter that can timely identify the reverse connection of photovoltaic strings is provided in this application. Figure 3 The difference is that in Figure 5 In the embodiment, the first photovoltaic string PV1 is connected to the output end of the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. The output end of the DC / DC power conversion circuit 12 is used to connect the bus capacitor. Figure 3 The relevant description is not repeated here.

[0064] exist Figure 5 In the embodiment, the first photovoltaic string PV1 is connected to the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. In practical applications, the first photovoltaic string PV1 can also be connected to the DC / DC power conversion circuit 12 through the anti-reverse circuit 11 and the first switch group S1.

[0065] It should also be noted that in Figure 5 In the embodiment, the first switch group S1 includes two switches, wherein the two switches are respectively connected to the anti-reverse circuit 11 through the positive pole PV1+ of the first photovoltaic string and the negative pole PV1- of the first photovoltaic string. In practical applications, the number of switches in the first switch group S1 is not limited to two, that is, the number of switches in the first switch group S1 can be one or more, and the present application does not impose any restrictions on this. When there is only one switch in the first switch group S1, the switch can be connected to the positive pole PV1+ of the first photovoltaic string or to the negative pole PV1- of the first photovoltaic string, and the present application does not impose any restrictions on this. Based on the same principle, the present application does not impose any restrictions on the number of switches in the second switch group S2, that is, there can be one switch or multiple switches on the connection line between each photovoltaic string and the DC / DC power conversion circuit 12.

[0066] Similarly, Figure 4a-4d The difference between the topology shown is that Figure 6a-6d In the embodiment, the first photovoltaic string PV1 is connected to the output end of the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11. Figure 4a-4d The specific description is omitted here.

[0067] As mentioned above, the first switch group S1 does not have the ability to be remotely disconnected. Therefore, after the controller is powered on and the second switch group S2 is closed, if the user does not disconnect the first switch group S1 for a long time, once a short circuit or reverse connection fault occurs inside the photovoltaic inverter, the controller cannot identify and disconnect the first switch group S1 in time, resulting in long-term abnormal current flowing through the first photovoltaic string PV1. In severe cases, it may even cause the first photovoltaic string PV1 and the photovoltaic inverter to catch fire and explode. It can be seen that after the second photovoltaic string is normally connected to the photovoltaic inverter, the user still needs to continue to disconnect the first switch group S1. However, since the actual installation scenario of the photovoltaic inverter is uncontrollable, there is a situation where the user forgets to disconnect the first switch group S1.

[0068] In order to remind the user to disconnect the first switch group S1, the photovoltaic inverter includes an indicator light. After the first switch group S1 is closed, if the first photovoltaic string PV1 is normally connected to the photovoltaic inverter, the first photovoltaic string PV1 can smoothly transmit DC power to the DC bus or bus capacitors C1 and C2, so that the controller is powered and powered on. At this time, the controller is used to control the indicator light to light up. The lighted indicator light is used to indicate that the controller in the photovoltaic inverter is working normally, thereby reminding the user to continue to close the second switch group S2. After the second switch S2 is closed, the indicator light is also used to remind the user to continue to disconnect the first switch group S1. For example, after the second photovoltaic string is normally connected to the photovoltaic inverter, if the user forgets to disconnect the first switch group S1, the controller can send an alarm signal, and the alarm signal includes a change in the color of the indicator light or a change in the flashing frequency, thereby reminding the user to continue to disconnect the first switch group S1. After the first switch group S1 is disconnected, the second photovoltaic string is connected to the photovoltaic inverter only through the second switch group S2 which can be disconnected remotely. Subsequently, even if the photovoltaic string connected to the photovoltaic inverter has reverse connection or overcurrent faults, the controller of the photovoltaic inverter can identify and eliminate the faults in time.

[0069] In addition, in order to effectively remind the user to disconnect the first switch group S1, the photovoltaic inverter may also include a warning light. After the second photovoltaic string is normally connected to the photovoltaic inverter, if the user forgets to disconnect the first switch group S1, the warning light is used to remind the user to disconnect the first switch group S1. For example, after the second photovoltaic string is normally connected to the photovoltaic inverter, if the first switch group S1 is closed, the controller is used to send an alarm signal, and the alarm signal includes the alarm light turning on. The turned-on alarm light is used to remind the user to disconnect the first switch group S1. After the first switch group S1 is disconnected, the controller is used to control the alarm light to turn off. The turned-off alarm light is used to indicate that the photovoltaic inverter can be safely connected to the grid. In actual application, the alarm light can be set to a more eye-catching color, and there is no specific limitation.

[0070] In addition, in order to effectively remind the user to disconnect the first switch group S1, the controller can also send an alarm signal to the application, or the client, or the host computer. For example, after the second photovoltaic string is normally connected to the photovoltaic inverter, if the user forgets to disconnect the first switch group S1, the controller is used to send an alarm signal to the application (App) on the user's mobile phone that the first switch group S1 is not disconnected, so that the user can promptly know the status of the first switch group S1 and manually disconnect the first switch group S1, so that the photovoltaic inverter can be safely connected to the grid.

[0071] Furthermore, in order to enable the controller to accurately obtain the state of the first switch group S1, the photovoltaic inverter further includes a switch state detection circuit. The state detection principle of the first switch group S1 will be specifically described below in conjunction with FIGS. 7 to 9.

[0072] See also Figure 7a ,and Figure 3 The difference between the topology shown is that Figure 7a It also includes a switch state detection circuit, wherein the switch state detection circuit is a voltage detection circuit 13. Specifically, one end of the first switch group S1 is connected to the DC input end of the DC / DC power conversion circuit 12 through an anti-reverse circuit 11 (the specific structure is referred to above, not listed one by one), and the other end of the first switch group S1 is used to be connected to the first photovoltaic string PV1, and the switch state detection circuit 13 is used to detect the voltage between the first detection point P1 and the second detection point P2. Among them, the first detection point P1 is located between the positive pole PV1+ of the first photovoltaic string and the bus capacitors C1 and C2, the second detection point P2 is located between the negative pole PV1- of the first photovoltaic string and the bus capacitors C1 and C2, and at least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the anti-reverse circuit 11. When the first switch group S1 is closed, the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input end of the DC / DC power conversion circuit 12, and the controller is used to send the above-mentioned alarm signal.

[0073] Specifically, when the first switch group S1 is closed, the connection line between the first photovoltaic string PV1 and the DC input terminal of the DC / DC power conversion circuit 12 is turned on, and the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input terminal of the DC / DC power conversion circuit 12. Among them, the voltage of the DC input terminal of the DC / DC power conversion circuit 12 can be equivalent to the voltage output by the second photovoltaic string to the DC input terminal of the DC / DC power conversion circuit 12. When the first switch group S1 is disconnected, the connection line between the first photovoltaic string PV1 and the DC input terminal of the DC / DC power conversion circuit 12 is not turned on, and at this time, the voltage between the first detection point P1 and the second detection point P2 is approximately equal to zero.

[0074] It is worth mentioning that at least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the anti-reverse circuit 11 means that at least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the output end of the anti-reverse circuit 11. In other words, the detection point located inside the anti-reverse circuit 11 also belongs to "located between the first switch group S1 and the anti-reverse circuit 11".

[0075] Such a setting can improve the detection accuracy of the voltage between the first detection point P1 and the second detection point P2, and avoid the influence of the voltage across the first photovoltaic string PV1 and the voltage at the DC input end of the DC / DC power conversion circuit 12 on the detection accuracy. For example, if the first detection point P1 and the second detection point P2 are both set between the first photovoltaic string PV1 and the first switch group S1, no matter whether the first switch group S1 is closed or open, as long as there is a voltage across the first photovoltaic string PV1 connected to the photovoltaic inverter, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the first photovoltaic string PV1, that is, the detection result of the voltage between the first detection point P1 and the second detection point P2 is difficult to reflect the state of the first switch group S1. For example, if the first detection point P1 and the second detection point P2 are both set between the output end of the anti-reverse circuit 11 and the DC input end of the DC / DC power conversion circuit 12, when the second switch group S2 is closed, no matter whether the first switch group S1 is closed or open, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage of the DC input end of the DC / DC power conversion circuit 12. That is to say, the detection result of the voltage between the first detection point P1 and the second detection point P2 is also difficult to reflect the state of the first switch group S1.

[0076] See also Figure 7b , which is different from the topology shown in 7a, Figure 7bIn the embodiment, the connection positions of the anti-reverse circuit 11 (the specific structure is described above and not listed one by one) and the first switch group S1 are swapped. One end of the anti-reverse circuit 11 is connected to the DC input end of the DC / DC power conversion circuit 12 through the first switch group S1, and the other end of the anti-reverse circuit 11 is used to connect to the first photovoltaic string PV1, and the voltage detection circuit 13 is used to detect the voltage between the first detection point P1 and the second detection point P2. Among them, the first detection point P1 is located between the positive pole PV1+ of the first photovoltaic string and the bus capacitors C1 and C2, the second detection point P2 is located between the negative pole PV1- of the first photovoltaic string and the bus capacitors C1 and C2, one of the first detection point P1 and the second detection point P2 is located between the first photovoltaic string PV1 and the first switch group S1, and the other of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the DC input terminal of the DC / DC power conversion circuit 12. When the first switch group is closed, the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input terminal of the DC / DC power conversion circuit 12, and the controller is used to send an alarm signal (see above).

[0077] Specifically, when the first switch group S1 is closed, the connection line between the first photovoltaic string PV1 and the DC input terminal of the DC / DC power conversion circuit 12 is turned on, and the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input terminal of the DC / DC power conversion circuit 12. Among them, the voltage of the DC input terminal of the DC / DC power conversion circuit 12 can be equivalent to the voltage output by the second photovoltaic string to the DC input terminal of the DC / DC power conversion circuit 12. When the first switch group S1 is disconnected, the connection line between the first photovoltaic string PV1 and the DC input terminal of the DC / DC power conversion circuit 12 is not turned on, and at this time, the voltage between the first detection point P1 and the second detection point P2 is approximately equal to zero.

[0078] Such a setting can improve the detection accuracy of the voltage between the first detection point P1 and the second detection point P2, and avoid the influence of the voltage across the first photovoltaic string PV1 and the voltage at the DC input end of the DC / DC power conversion circuit 12 on the detection accuracy. For example, if the first detection point P1 and the second detection point P2 are both set between the first photovoltaic string PV1 and the first switch group S1, no matter whether the first switch group S1 is closed or open, as long as there is a voltage across the first photovoltaic string PV1 connected to the photovoltaic inverter, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the first photovoltaic string PV1, that is, the detection result of the voltage between the first detection point P1 and the second detection point P2 is difficult to reflect the state of the first switch group S1. For example, if the first detection point P1 and the second detection point P2 are both set between the first switch group S1 and the DC input end of the DC / DC power conversion circuit 12, when the second switch group S2 is closed, no matter whether the first switch group S1 is closed or open, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage of the DC input end of the DC / DC power conversion circuit 12. That is to say, the detection result of the voltage between the first detection point P1 and the second detection point P2 is also difficult to reflect the state of the first switch group S1.

[0079] See also Figure 7c , which is different from the topology shown in 7a, Figure 7c In the embodiment, one end of the first switch group S1 is connected to the DC output end of the DC / DC power conversion circuit 12 through the anti-reverse circuit 11 (the specific structure is described above and not listed one by one), and the other end of the first switch group S1 is used to be connected to the first photovoltaic string PV1, and the voltage detection circuit 13 is used to detect the voltage between the first detection point P1 and the second detection point P2. Among them, the first detection point P1 is located between the positive pole PV1+ of the first photovoltaic string and the bus capacitors C1 and C2, and the second detection point P2 is located between the negative pole PV1- of the first photovoltaic string and the bus capacitors C1 and C2. At least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the anti-reverse circuit 11. When the first switch group S1 is closed, the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input end of the DC / DC power conversion circuit 12, and the controller is used to send an alarm signal (see above).

[0080] Specifically, when the first switch group S1 is closed, the connection line between the first photovoltaic string PV1 and the DC output terminal of the DC / DC power conversion circuit 12 is turned on. Due to the existence of the anti-reverse circuit 11, although the DC output terminal voltage of the DC / DC power conversion circuit 12 is greater than the DC input terminal voltage of the DC / DC power conversion circuit 12, the voltage between the first detection point P1 and the second detection point P2 is still equal to the DC input terminal voltage of the DC / DC power conversion circuit 12. When the first switch group S1 is turned off, the connection line between the first photovoltaic string PV1 and the DC output terminal of the DC / DC power conversion circuit 12 is not turned on. At this time, the voltage between the first detection point P1 and the second detection point P2 is approximately equal to zero.

[0081] It is worth mentioning that at least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the anti-reverse circuit 11 means that at least one of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the output end of the anti-reverse circuit 11. In other words, the detection point located inside the anti-reverse circuit 11 also belongs to "located between the first switch group S1 and the anti-reverse circuit 11".

[0082] Such a setting can improve the detection accuracy of the voltage between the first detection point P1 and the second detection point P2, and avoid the influence of the voltage across the first photovoltaic string PV1 and the voltage at the DC output end of the DC / DC power conversion circuit 12 on the detection accuracy. For example, if the first detection point P1 and the second detection point P2 are both set between the first photovoltaic string PV1 and the first switch group S1, no matter whether the first switch group S1 is closed or open, as long as there is a voltage across the first photovoltaic string PV1 connected to the photovoltaic inverter, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the first photovoltaic string PV1, that is, the detection result of the voltage between the first detection point P1 and the second detection point P2 is difficult to reflect the state of the first switch group S1. For example, if the first detection point P1 and the second detection point P2 are both set between the output end of the anti-reverse circuit 11 and the DC output end of the DC / DC power conversion circuit 12, when the second switch group S2 is closed, no matter whether the first switch group S1 is closed or open, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the bus capacitors C1 and C2, or the DC output end voltage of the DC / DC power conversion circuit 12, or the DC bus voltage. That is to say, the detection result of the voltage between the first detection point P1 and the second detection point P2 is also difficult to reflect the state of the first switch group S1.

[0083] See also Figure 7d , which is different from the topology shown in 7c, Figure 7dIn the figure, one end of the anti-reverse circuit 11 (the specific structure is shown above and not listed one by one) is connected to the DC output end of the DC / DC power conversion circuit 12 through the first switch group S1, and the other end of the anti-reverse circuit 11 is used to be connected to the first photovoltaic string PV1, and the voltage detection circuit 13 is used to detect the voltage between the first detection point P1 and the second detection point P2. Among them, the first detection point P1 is located between the positive pole PV1+ of the first photovoltaic string and the bus capacitors C1 and C2, the second detection point P2 is located between the negative pole PV1- of the first photovoltaic string and the bus capacitors C1 and C2, one of the first detection point P1 and the second detection point P2 is located between the first photovoltaic string and the first switch group S1, and the other of the first detection point P1 and the second detection point P2 is located between the first switch group S1 and the DC output end of the DC / DC power conversion circuit 12. When the first switch group S1 is closed, the voltage between the first detection point P1 and the second detection point P2 is equal to the voltage of the DC input end of the DC / DC power conversion circuit 12, and the controller is used to send an alarm signal (see above).

[0084] Specifically, when the first switch group S1 is closed, the connection line between the first photovoltaic string PV1 and the DC output terminal of the DC / DC power conversion circuit 12 is turned on. Due to the existence of the anti-reverse circuit 11, although the DC output terminal voltage of the DC / DC power conversion circuit 12 is greater than the DC input terminal voltage of the DC / DC power conversion circuit 12, the voltage between the first detection point P1 and the second detection point P2 is still equal to the DC input terminal voltage of the DC / DC power conversion circuit 12. When the first switch group S1 is turned off, the connection line between the first photovoltaic string PV1 and the DC output terminal of the DC / DC power conversion circuit 12 is not turned on. At this time, the voltage between the first detection point P1 and the second detection point P2 is approximately equal to zero.

[0085] Such a setting can improve the detection accuracy of the voltage between the first detection point P1 and the second detection point P2, and avoid the influence of the voltage across the first photovoltaic string PV1 and the voltage at the DC output end of the DC / DC power conversion circuit 12 on the detection accuracy. For example, if the first detection point P1 and the second detection point P2 are both set between the first photovoltaic string PV1 and the first switch group S1, no matter whether the first switch group S1 is closed or open, as long as there is a voltage across the first photovoltaic string PV1 connected to the photovoltaic inverter, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the first photovoltaic string PV1, that is, the detection result of the voltage between the first detection point P1 and the second detection point P2 is difficult to reflect the state of the first switch group S1. For example, if the first detection point P1 and the second detection point P2 are both set between the first switch group S1 and the DC output end of the DC / DC power conversion circuit 12, when the second switch group S2 is closed, no matter whether the first switch group S1 is closed or open, there is a voltage between the first detection point P1 and the second detection point P2, and the voltage is approximately equal to the voltage across the bus capacitors C1 and C2, or the DC output end voltage of the DC / DC power conversion circuit 12, or the DC bus voltage. That is to say, the detection result of the voltage between the first detection point P1 and the second detection point P2 is also difficult to reflect the state of the first switch group S1.

[0086] It is worth mentioning that Figures 7a to 7d The voltage detection circuits 13 shown all include an operational amplifier, wherein the positive input terminal of the operational amplifier is used to connect to the first detection point P1, the negative input terminal of the operational amplifier is used to connect to the second detection point P2, and the output terminal of the operational amplifier is used to transmit the signal of the voltage between the first detection point P1 and the second detection point P2 to the controller, so that the controller can know the closed or open state of the first switch group S1 and send an alarm signal when the first switch group S1 is closed, so that the user can disconnect the first switch group S1 in time. In practical applications, a current limiting resistor can be set between the positive input terminal of the operational amplifier and the first detection point P1, and a current limiting resistor can also be set between the negative input terminal of the operational amplifier and the second detection point P2, and this application does not limit this.

[0087] in addition, Figures 7a to 7d The operational amplifier is mainly used to achieve voltage changes and increase the output current capability. Therefore, in practical applications, the operational amplifier can also be converted into other devices with similar functions.

[0088] See also Figure 8 ,and Figure 3 The difference between the topology shown is that Figure 8It also includes a switch state detection circuit, wherein the switch state detection circuit is a current detection circuit 14. Specifically, the first photovoltaic string PV1 is connected to the DC input terminal of the DC / DC power conversion circuit 12 through the first switch group S1 and the anti-reverse circuit 11 in sequence, and the current detection circuit 14 is used to detect the current flowing through the third detection point P3, wherein the third detection point P3 is located between the first photovoltaic string PV1 and the anti-reverse circuit 11, when the first switch group S1 is closed, the current flowing through the third detection point P3 is greater than the current setting threshold, and the controller is used to send an alarm signal (see above), wherein the current setting threshold is greater than zero and less than the current of the DC input terminal of the DC / DC power conversion circuit 12.

[0089] Specifically, when the first switch group S1 is closed, the connection line between the first photovoltaic string PV1 and the DC input end of the DC / DC power conversion circuit 12 is turned on, and the current detection circuit 14 can detect the current at the third detection point P3. When the first switch group S1 is disconnected, the connection line between the first photovoltaic string PV1 and the DC input end of the DC / DC power conversion circuit 12 is not turned on, and the third detection point P3 cannot detect the current.

[0090] By setting the third detection point P3 between the first switch group S1 and the anti-reverse circuit 11, the current detection accuracy of the third detection point P3 can be improved, and the influence of the DC input terminal current of the DC / DC power conversion circuit on the detection accuracy can be avoided.

[0091] It is worth mentioning that in practical applications, the connection between the first switch group S1 and the anti-reverse circuit 11 can also be reversed, that is, the first photovoltaic string PV1 is connected to the DC input end of the DC / DC power conversion circuit 12 through the anti-reverse circuit 11 and the first switch group S1 in sequence. In addition, the first switch group S1 and the anti-reverse circuit 11 can also be connected to the DC output end of the DC / DC power conversion circuit 12 after being connected in series.

[0092] in addition, Figure 8 The detection circuit 14 includes a current sampling module and an operational amplifier. The current sampling module is used to collect the current flowing through the third detection point P3 and transmit the collected current signal to the operational amplifier. The operational amplifier processes the current signal and then transmits it to the controller.

[0093] See also Figure 9a ,and Figure 3 The topology shown differs in that, on the one hand, Figure 9aIt also includes a switch state detection circuit. On the other hand, the first switch group S1 includes a main contact switch S11 and an auxiliary contact switch S12. Among them, the switch state detection circuit includes a resistor network 15 and an operational amplifier. One end of the resistor network 15 is used to connect to the auxiliary contact switch S12, and the other end of the resistor network 15 is used to connect to the input end of the operational amplifier. The operational amplifier is used to transmit its output signal (which will be described in detail later) to the controller, so that the controller can know the closed or open state of the first switch group S1 and send an alarm signal when the first switch group S1 is closed (see above). It is worth mentioning that the main contact switch S11 and the auxiliary contact switch S12 have the same closed and open states, wherein the main contact switch S11 is used to pass current, and the auxiliary contact switch S12 is used to reflect the closed or open state of the main contact switch S11. Specifically, Figure 9a In the circuit, one end of the main contact switch S11 is used to connect to the first photovoltaic string PV1, and the other end of the main contact switch S11 is used to connect to the bus capacitors C1 and C2 through the anti-reverse circuit 11 and the DC / DC power conversion circuit 12. In other words, the closed and open states of the main contact switch S11 determine whether the electric energy generated by the first photovoltaic string PV1 can be smoothly transmitted to the bus capacitors C1 and C2. When the main contact switch S11 is closed, the direct current output by the first photovoltaic string PV1 will flow through the main contact switch S11 but not through the auxiliary contact switch S12. In this way, the switch state detection circuit can indirectly obtain the closed and open states of the main contact switch S11, thereby avoiding a large current from flowing through the switch state detection circuit, ensuring the detection accuracy of the switch state detection circuit, and reducing the failure probability of the switch state detection circuit.

[0094] It should be noted that, in actual application, the other end of the main contact switch S11 is connected to the bus capacitors C1 and C2, including direct connection and indirect connection. Figure 9a Only the indirect connection between the two is shown, and this application does not limit this. That is to say, the other end of the main contact switch S11 is connected to the bus capacitors C1 and C2 is a functional description, and its essence is: the state of the main contact switch S11 determines whether the DC power generated by the first photovoltaic string PV1 can be smoothly transmitted to the bus capacitors C1 and C2.

[0095] In order to better introduce Figure 9a Please refer to the working principle of the switch status detection circuit in Figure 9b , Figure 9b exist Figure 9aThe topology of the resistor network 15 in the switch state detection circuit is specifically shown on the basis of FIG. Among them, the resistor network 15 includes a second resistor R2 and a third resistor R3 with equal resistance values, one end of the second resistor R2 is used to be connected to a stable voltage source (VoltCurrent Condenser, VCC), the other end of the second resistor R2 is used to be connected to the analog ground (Ana log Ground, AGND) through the third resistor R3, the series connection point of the second resistor R2 and the third resistor R3 is used to be connected to AGND through the auxiliary contact switch S12, and the series connection point of the second resistor R2 and the third resistor R3 is also used to be connected to the positive input terminal of the operational amplifier, and the negative input terminal of the operational amplifier is connected to the output terminal of the operational amplifier. When the auxiliary contact switch S12 is disconnected, the voltage output from the series connection point of the second resistor R2 and the third resistor R3 to the positive input terminal of the operational amplifier is 1 / 2VCC, that is, both ends of the second resistor R2 and the third resistor R3 bear the divided voltage of 1 / 2VCC. When the auxiliary contact switch S12 is closed, the third resistor R3 is bypassed, and the voltage output from the series connection point of the second resistor R2 and the third resistor R3 to the positive input terminal of the operational amplifier is 0, that is, the second resistor R2 bears the voltage of VCC alone. Based on this, the switch state detection circuit can output different voltage / current signals to the controller, so that the controller can determine the closed or open state of the auxiliary contact switch S12. For example, when the auxiliary contact switch S12 is closed, the voltage output from the series connection point of the second resistor R2 and the third resistor R3 to the positive input terminal of the operational amplifier is 0, and the switch state detection circuit outputs a voltage signal of 0 level to the controller, and the controller is used to send an alarm signal (see above), thereby reminding the user to disconnect the first switch group S1 in time.

[0096] It is worth mentioning that in actual application, the resistance values ​​of the second resistor R2 and the third resistor R3 may not be equal. Based on this, when the auxiliary contact switch S12 is disconnected, the voltage output from the series connection point of the second resistor R2 and the third resistor R3 to the positive input terminal of the operational amplifier is no longer 1 / 2VCC. The specific voltage value can be determined according to the node voltage method, and this application does not limit this.

[0097] in addition, Figure 9b The operational amplifier is mainly used to achieve voltage changes and improve the output current capability. Therefore, in practical applications, the operational amplifier can also be converted into other devices with similar functions, without specific limitation.

[0098] The above specific implementation methods further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the present invention should be included in the scope of protection of the present invention.

Claims

1. A photovoltaic inverter, characterized in that: The photovoltaic inverter includes a first switch group, a second switch group, a DC / DC power conversion circuit, a bus capacitor, a switch state detection circuit and a controller; wherein, The first switch group does not have a remote disconnection capability, one end of the first switch group is used to be connected to the first photovoltaic string, and the other end of the first switch group is used to be connected to the bus capacitor, so that when the first switch group is closed, the controller is powered by the bus capacitor. The second switch group has a remote disconnection capability, one end of the second switch group is used to be connected to the second photovoltaic string, and the other end of the second switch group is used to be connected to the DC input end of the DC / DC power conversion circuit, wherein the first photovoltaic string is a part of the second photovoltaic string; The DC output terminal of the DC / DC power conversion circuit is connected to the bus capacitor; After the controller is powered on and the second switch group is closed, the switch status detection circuit is used to detect the closed or open state of the first switch group. If the first switch group is still closed, the controller is used to send an alarm signal, and the alarm signal is used to prompt the user to disconnect the first switch group.

2. The photovoltaic inverter according to claim 1, characterized in that: The photovoltaic inverter includes an anti-reverse circuit, which is connected in series with the first switch group and connected between the first photovoltaic string and the bus capacitor. The anti-reverse circuit is used to prevent reverse current from entering the bus capacitor when the first switch group is closed and the first photovoltaic string is reversely connected.

3. The photovoltaic inverter according to claim 2, characterized in that: One end of the anti-reverse circuit is connected to the DC input end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the voltage between a first detection point and a second detection point, wherein the first detection point is located between the positive electrode of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative electrode of the first photovoltaic string and the bus capacitor, one of the first detection point and the second detection point is located between the first photovoltaic string and the first switch group, and the other of the first detection point and the second detection point is located between the first switch group and the DC input end of the DC / DC power conversion circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

4. The photovoltaic inverter according to claim 2, characterized in that: One end of the anti-reverse circuit is connected to the DC output end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the voltage between a first detection point and a second detection point, wherein the first detection point is located between the positive electrode of the first photovoltaic string and the bus capacitor, the second detection point is located between the negative electrode of the first photovoltaic string and the bus capacitor, one of the first detection point and the second detection point is located between the first photovoltaic string and the first switch group, and the other of the first detection point and the second detection point is located between the first switch group and the DC output end of the DC / DC power conversion circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

5. The photovoltaic inverter according to claim 2, characterized in that: One end of the first switch group is connected to the DC input end of the DC / DC power conversion circuit through the anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the voltage between a first detection point and a second detection point, wherein the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, and the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor. At least one of the first detection point and the second detection point is located between the first switch group and the anti-reverse circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

6. The photovoltaic inverter according to claim 2, characterized in that: One end of the first switch group is connected to the DC output end of the DC / DC power conversion circuit through the anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the voltage between a first detection point and a second detection point, wherein the first detection point is located between the positive pole of the first photovoltaic string and the bus capacitor, and the second detection point is located between the negative pole of the first photovoltaic string and the bus capacitor. At least one of the first detection point and the second detection point is located between the first switch group and the anti-reverse circuit. When the first switch group is closed, the voltage between the first detection point and the second detection point is equal to the voltage of the DC input end of the DC / DC power conversion circuit, and the controller is used to send an alarm signal.

7. The photovoltaic inverter according to claim 2, characterized in that: One end of the anti-reverse circuit is connected to the DC input end of the DC / DC power conversion circuit through the first switch group, and the other end of the anti-reverse circuit is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the current flowing through the third detection point P3, wherein the third detection point P3 is located between the first photovoltaic string and the first switch group. When the first switch group is closed, the current flowing through the third detection point P3 is greater than the current setting threshold, and the controller is used to issue an alarm signal, wherein the current setting threshold is greater than zero and less than the current of the DC input end of the DC / DC power conversion circuit.

8. The photovoltaic inverter according to claim 2, characterized in that: One end of the first switch group is connected to the DC input end of the DC / DC power conversion circuit through the anti-reverse circuit, and the other end of the first switch group is used to be connected to the first photovoltaic string. The switch state detection circuit is used to detect the current flowing through the third detection point P3, wherein the third detection point P3 is located between the first photovoltaic string and the anti-reverse circuit. When the first switch group is closed, the current flowing through the third detection point P3 is greater than the current setting threshold, and the controller is used to issue an alarm signal, wherein the current setting threshold is greater than zero and less than the current at the DC input end of the DC / DC power conversion circuit.

9. The photovoltaic inverter according to claim 2, characterized in that: The first switch group includes an auxiliary contact switch and a main contact switch. The closed and open states of the auxiliary contact switch are the same as those of the main contact switch. One end of the main contact switch is used to be connected to the first photovoltaic string, and the other end of the main contact switch is used to be connected to the bus capacitor. The auxiliary contact switch is connected to the switch state detection circuit. When the auxiliary contact switch is closed, the controller is used to send an alarm signal.

10. The photovoltaic inverter according to claim 9, characterized in that: The switch state detection circuit includes a second resistor, a third resistor and an operational amplifier, one end of the second resistor is used to be connected to a stable voltage source, the other end of the second resistor is used to be connected to an analog ground through the third resistor, the series connection point of the second resistor and the third resistor is used to be connected to the analog ground through the auxiliary contact switch, the series connection point of the second resistor and the third resistor is also used to be connected to an input end of the operational amplifier, and the output end of the operational amplifier is connected to the controller.

11. The photovoltaic inverter according to claim 10, characterized in that: When the auxiliary contact switch is closed, the series connection point of the second resistor and the third resistor outputs zero voltage to the operational amplifier, and the operational amplifier is used to output a zero point level to the controller, and the controller user sends the alarm signal.

12. The photovoltaic inverter according to any one of claims 1 to 11, characterized in that: The photovoltaic inverter includes an indicator light. If the first switch group is closed so that the controller is powered on by the bus capacitor, the indicator light is on. The indicator light is used to instruct the user to close the second switch group. After the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to control the color change of the indicator light, and the controller is used to control the flashing frequency change of the indicator light.

13. The photovoltaic inverter according to any one of claims 1 to 11, characterized in that: The photovoltaic inverter includes a warning light. After the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to control the warning light to light up.

14. The photovoltaic inverter according to any one of claims 1 to 11, characterized in that: After the second switch group is closed, if the first switch group is still closed, the controller is used to send an alarm signal, including: the controller is used to send an alarm signal to an application, or a client, or a host computer.

15. The photovoltaic inverter according to claim 2, characterized in that: The anti-reverse circuit includes one or more diodes, and the conduction direction of the diodes is opposite to the direction of the reverse current.

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