A bipolar photovoltaic system, power system and redundancy protection method

Abstract

The application discloses a bipolar photovoltaic system, a power supply system and a redundancy protection method. The photovoltaic system at least comprises: a first output end, a second output end and a third output end of a power converter are connected with a first end of a direct current positive bus, a first end of a neutral bus and a first end of a direct current negative bus respectively; a first input end and a second input end of a first inverter are connected with a second end of the direct current positive bus and a second end of the neutral bus respectively; a first input end and a second input end of a second inverter are connected with the second end of the neutral bus and a second end of the direct current negative bus respectively; a first controller outputs a first overvoltage alarm signal when at least one of the following conditions is met; a second controller outputs a second overvoltage alarm signal when at least one of the following conditions is met; at least one of the conditions includes: a direct current positive bus voltage greater than or equal to a preset threshold, a direct current negative bus voltage greater than or equal to a preset threshold or a neutral bus voltage greater than or equal to a preset threshold, and the system is timely protected by redundancy when a fault occurs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic power generation, and particularly relates to a bipolar photovoltaic system, a power supply system and a redundancy protection method. BACKGROUND

[0002] At present, photovoltaic power generation is paid more and more attention, and the voltage level is higher and higher. In the traditional photovoltaic power generation, a photovoltaic array outputs direct current, which is converted into alternating current by an inverter and then is connected to a grid or is provided to a load.

[0003] A direct current bus in the traditional photovoltaic system includes a direct current positive bus and a direct current negative bus, that is, a positive input end of the inverter is connected to the direct current positive bus, and a negative input end of the inverter is connected to the direct current negative bus. The voltage between the direct current positive bus and the direct current negative bus is used as the input voltage of the inverter.

[0004] In order to meet the safety standard, the input voltage of the inverter, that is, the voltage on the direct current side, cannot be greater than or equal to the safety requirement, otherwise, the human body and the equipment will be damaged, especially for the power devices inside the inverter, each power device has a corresponding voltage withstand requirement, and if the voltage is greater than or equal to the voltage withstand, the power device will be damaged by breakdown. If the voltage level of the photovoltaic system is higher, the voltage withstand of the power device is a new challenge, and the selection of the power device is more and more difficult.

[0005] Application Content

[0006] The present application provides a bipolar photovoltaic system, a power supply system and a redundancy protection method, which can realize fault detection of the bipolar power supply and redundancy protection in time when a fault occurs.

[0007] The embodiment of the present application provides a bipolar photovoltaic system which is different from the traditional unipolar photovoltaic system. The bipolar photovoltaic system includes three direct current buses, that is, a direct current positive bus, a neutral bus and a direct current negative bus. An input end of a power converter is connected to a photovoltaic array. A first output end, a second output end and a third output end of the power converter are respectively connected to a first end of the direct current positive bus, a first end of the neutral bus and a first end of the direct current negative bus. A first input end and a second input end of a first inverter are respectively connected to a second end of the direct current positive bus and a second end of the neutral bus. A first input end and a second input end of a second inverter are respectively connected to a second end of the neutral bus and a second end of the direct current negative bus.

[0008] In order to comprehensively and reliably protect the bipolar photovoltaic system, the embodiments of the present application can set at least two controllers to perform overvoltage detection, and of course, the number of controllers is not limited to two. For example, the first controller outputs a first overvoltage warning signal when at least one of the following conditions is met; the second controller outputs a second overvoltage warning signal when at least one of the following conditions is met; the at least one condition includes: the DC positive bus voltage is greater than or equal to a preset threshold, the DC negative bus voltage is greater than or equal to a preset threshold, or the neutral bus voltage is greater than or equal to a preset threshold. That is, as long as one of the DC bus voltages is greater than or equal to the preset threshold, both controllers output the corresponding overvoltage warning signal, and even if one of the controllers fails, it does not affect the overvoltage judgment, so that the overvoltage protection measure can be reliably performed. The voltage is reduced to below the preset threshold, that is, the voltage is reduced to the requirement of safety regulations, thereby ensuring the safety of personnel and equipment. The first controller and the second controller are equally important when protecting the bipolar photovoltaic system. The embodiments of the present application perform double overvoltage monitoring on the photovoltaic system through two controllers, thereby achieving redundant protection.

[0009] In a possible implementation, in addition to detecting the ground voltages of the three DC buses respectively, the two controllers also monitor the heartbeat signals of the other party, and output a heartbeat warning signal when the other party is abnormal. Specifically, the first controller outputs a first heartbeat warning signal when the second controller is abnormal; the second controller outputs a second heartbeat warning signal when the first controller is abnormal.

[0010] In a possible implementation, the first controller outputs a first heartbeat warning signal when it does not receive the heartbeat signal sent by the second controller; the second controller outputs a second heartbeat warning signal when it does not receive the heartbeat signal sent by the first controller. In practice, the first controller will send a heartbeat signal in the form of a pulse signal to the second controller, and similarly, the second controller will send a heartbeat signal in the form of a pulse signal to the first controller. Once the heartbeat signal sent by the other party cannot be received, the corresponding heartbeat warning signal is output.

[0011] In a possible implementation, in order to achieve more comprehensive and reliable protection, when any one of the DC bus voltages is overvoltage, or any one of the controllers is abnormal, the drive pulse signal of the power converter is blocked, so that all power devices in the power converter, i.e. the switching tube, stop switching action. This scheme can be implemented by using a logic circuit, which is connected to the first controller and the second controller; the logic circuit blocks the drive pulse signal of the power converter when receiving at least one of the following warning signals; the at least one warning signal includes: the first overvoltage warning signal, the second overvoltage warning signal, the first heartbeat warning signal, or the second heartbeat warning signal. The embodiments of the present application do not limit the logic operation form of the logic circuit, for example, it can be a logical OR or a logical AND.

[0012] In a possible implementation, the logic circuit is a complex programmable logic device (CPLD); the CPLD is specifically configured to perform a logical OR operation on the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, and the second heartbeat alarm signal, and block the driving pulse signal for the power converter when the result of the logical OR operation is true. The logical OR operation corresponds to each alarm signal being active at a high level, and the driving pulse signal is blocked when one of the alarm signals is at a high level.

[0013] In a possible implementation, the logic circuit is a complex programmable logic device (CPLD); the CPLD is specifically configured to perform a logical AND operation on the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, and the second heartbeat alarm signal, and block the driving pulse signal for the power converter when the result of the logical AND operation is false. The logical AND operation corresponds to each alarm signal being active at a low level, and the driving pulse signal is blocked when one of the alarm signals is at a low level. The low level has stronger anti-interference capability, and thus the result of the protection action is more accurate.

[0014] In a possible implementation, the first controller compares the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground with a preset threshold value, and outputs the first overvoltage alarm signal when at least one of the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground is greater than or equal to the preset threshold value. The first controller can compare the voltages of the three DC buses with the preset threshold value when overvoltage occurs, that is, three different comparisons are performed, and the first overvoltage alarm signal is output when at least one of the three different comparison results is true.

[0015] In a possible implementation, to reduce the number of comparisons, the maximum value of the voltages of the three DC buses to ground can be obtained first, and the maximum value is compared with the preset threshold value. The first controller is specifically configured to obtain the maximum value of the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, and the absolute value of the neutral bus voltage to ground, and output the first overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold value.

[0016] In a possible implementation, the second controller is specifically configured to respectively compare the absolute value of the DC positive bus-to-ground voltage, the absolute value of the DC negative bus-to-ground voltage, or the absolute value of the neutral bus-to-ground voltage with a preset threshold value, and output a second overvoltage alarm signal when at least one of the absolute value of the DC positive bus-to-ground voltage, the absolute value of the DC negative bus-to-ground voltage, and the absolute value of the neutral bus-to-ground voltage is greater than or equal to the preset threshold value. The second controller can compare the voltages of the three DC buses with the preset threshold value when overvoltage occurs, that is, three different comparisons are performed, and the second overvoltage alarm signal is output as long as one of the three different comparison results is true.

[0017] In a possible implementation, to reduce the number of comparisons, the maximum value of the voltages of the three DC buses can be obtained first, and then the maximum value is compared with the preset threshold value. That is, the second controller obtains the maximum value among the absolute value of the DC positive bus-to-ground voltage, the absolute value of the DC negative bus-to-ground voltage, and the absolute value of the neutral bus-to-ground voltage, and outputs the second overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold value.

[0018] In a possible implementation, the voltage sampling circuit collects the voltage between the DC positive bus and the neutral bus, the voltage between the DC negative bus and the neutral bus, and the voltage between the neutral bus and the ground; and the first controller and the second controller are both specifically configured to obtain the DC positive bus-to-ground voltage according to the voltage between the DC positive bus and the neutral bus and the voltage between the neutral bus and the ground, and obtain the DC negative bus-to-ground voltage according to the voltage between the DC negative bus and the neutral bus and the voltage between the neutral bus and the ground.

[0019] The above embodiments provide a bipolar photovoltaic system including three DC buses. It should be understood that the bipolar power supply can be applied not only in the field of photovoltaic power generation, but also in the fields of wind power generation and energy storage power supply, that is, the embodiments of the present application also provide a power supply system, which includes a first inverter, a second inverter, a first controller, and a second controller; a first end of a DC positive bus is configured to be connected to a first output end of a DC power supply, a first end of a neutral bus is configured to be connected to a second output end of the DC power supply, and a first end of a DC negative bus is configured to be connected to a third output end of the DC power supply; a second end of the DC positive bus is connected to a first input end of the first inverter, and a second end of the neutral bus is connected to a second input end of the first inverter; a second end of the neutral bus is connected to a first input end of the second inverter, and a second end of the DC negative bus is connected to a second input end of the second inverter; the first controller is configured to output a first overvoltage alarm signal when at least one of the following conditions is met; and the second controller is configured to output a second overvoltage alarm signal when at least one of the following conditions is met; the at least one condition includes that the DC positive bus-to-ground voltage is greater than or equal to a preset threshold value, the DC negative bus-to-ground voltage is greater than or equal to the preset threshold value, or the neutral bus-to-ground voltage is greater than or equal to the preset threshold value.

[0020] In a possible implementation, the direct current power source is derived from any one of the following: photovoltaic power generation, wind power generation, or energy storage battery.

[0021] In a possible implementation, the first controller is further configured to output a first heartbeat alarm signal when the second controller is abnormal; and the second controller is further configured to output a second heartbeat alarm signal when the first controller is abnormal.

[0022] In a possible implementation, the first controller is specifically configured to detect that the second controller is abnormal when the second controller does not send a heartbeat signal; and the second controller is specifically configured to detect that the first controller is abnormal when the first controller does not send a heartbeat signal.

[0023] In a possible implementation, the first controller is specifically configured to obtain a maximum value among an absolute value of a direct current positive bus voltage, an absolute value of a direct current negative bus voltage, and an absolute value of a neutral bus voltage, and output a first overvoltage alarm signal when the maximum value is greater than or equal to a preset threshold; and the second controller is specifically configured to obtain a maximum value among the absolute value of the direct current positive bus voltage, the absolute value of the direct current negative bus voltage, and the absolute value of the neutral bus voltage, and output a second overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold.

[0024] In a possible implementation, the first controller is specifically configured to compare the absolute value of the direct current positive bus voltage, the absolute value of the direct current negative bus voltage, or the absolute value of the neutral bus voltage with the preset threshold respectively, and output the first overvoltage alarm signal when at least one of the absolute value of the direct current positive bus voltage, the absolute value of the direct current negative bus voltage, or the absolute value of the neutral bus voltage is greater than or equal to the preset threshold; and the second controller is specifically configured to compare the absolute value of the direct current positive bus voltage, the absolute value of the direct current negative bus voltage, or the absolute value of the neutral bus voltage with the preset threshold respectively, and output the second overvoltage alarm signal when at least one of the absolute value of the direct current positive bus voltage, the absolute value of the direct current negative bus voltage, or the absolute value of the neutral bus voltage is greater than or equal to the preset threshold.

[0025] In a possible implementation, further comprising: a logic circuit connected to the first controller and the second controller; and the logic circuit is configured to block a driving pulse signal to the power converter when at least one alarm signal is received, wherein the at least one alarm signal comprises: the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, or the second heartbeat alarm signal.

[0026] The embodiment of the application further provides a protection method of a bipolar photovoltaic system, the bipolar photovoltaic system comprising: a first input end of a first inverter being connected to a second end of a direct current positive bus, a second input end of the first inverter being connected to a second end of a neutral bus; a first input end of a second inverter being connected to the second end of the neutral bus, a second input end of the second inverter being connected to a second end of a direct current negative bus; monitoring a first overvoltage alarm signal output by a first controller and a second overvoltage alarm signal output by a second controller; judging whether the bipolar photovoltaic system is faulty according to the first overvoltage alarm signal or the second overvoltage alarm signal; the first controller outputting the first overvoltage alarm signal when at least one of the following conditions is met; the second controller outputting the second overvoltage alarm signal when at least one of the following conditions is met; the at least one condition comprising: a direct current positive bus voltage being greater than or equal to a preset threshold, a direct current negative bus voltage being greater than or equal to the preset threshold, or a neutral bus voltage being greater than or equal to the preset threshold.

[0027] In a possible implementation, the method further comprises: determining that the bipolar photovoltaic system is faulty when the first controller outputs a first heartbeat alarm signal or the second controller outputs a second heartbeat alarm signal; the first controller outputting the first heartbeat alarm signal when the second controller is abnormal; the second controller outputting the second heartbeat alarm signal when the first controller is abnormal.

[0028] In a possible implementation, the method further comprises: blocking a driving pulse signal to the power converter when at least one alarm signal is received; the at least one alarm signal comprising: the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, or the second heartbeat alarm signal.

[0029] In a possible implementation, the first controller outputs the first overvoltage alarm signal when the direct current positive bus voltage, the direct current negative bus voltage, or the neutral bus voltage is greater than or equal to the preset threshold, and specifically comprises: obtaining a maximum value among an absolute value of the direct current positive bus voltage, an absolute value of the direct current negative bus voltage, and an absolute value of the neutral bus voltage; outputting the first overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold.

[0030] In a possible implementation, the second controller outputs the second overvoltage alarm signal when the direct current positive bus voltage, the direct current negative bus voltage, or the neutral bus voltage is greater than or equal to the preset threshold, and specifically comprises: obtaining a maximum value among an absolute value of the direct current positive bus voltage, an absolute value of the direct current negative bus voltage, and an absolute value of the neutral bus voltage; outputting the second overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold.

[0031] As can be seen from the above technical solutions, the embodiment of the application has the following advantages:

[0032] The bipolar photovoltaic system at least includes the following two controllers: a first controller and a second controller. The first controller and the second controller simultaneously monitor the voltages of three DC buses to ground, i.e., the voltages of a DC positive bus, a DC negative bus and a neutral bus to ground. When the voltage of any one of the DC buses to ground is greater than or equal to a preset threshold, the first controller and the second controller will both output an overvoltage warning signal. The first controller and the second controller realize redundant control. If one of the controllers fails, the overvoltage judgment will not be affected, and the system will take corresponding measures to reduce the voltage to below the preset threshold, thereby protecting the safety of the bipolar photovoltaic system, i.e., reducing the voltage to the requirement of safety regulations, thereby ensuring the safety of personnel and equipment. It should be noted that the first controller and the second controller are equally important when protecting the bipolar photovoltaic system. The bipolar photovoltaic system does not increase the voltage level of the safety regulations, so the voltage borne by the power device can be reduced, and the power device is easy to select. However, the total voltage of the DC bus is the voltage after the two-pole bus is connected in series, so the total voltage of the DC bus is high, thereby reducing the power consumption on the DC bus and improving the power conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A schematic diagram of a bipolar photovoltaic system provided by an embodiment of the present application;

[0034] Figure 2 A schematic diagram of a bipolar system applied to wind power generation provided by an embodiment of the present application;

[0035] Figure 3 A schematic diagram of a bipolar system applied to an energy storage battery provided by an embodiment of the present application;

[0036] Figure 4 A schematic diagram of another bipolar photovoltaic system provided by an embodiment of the present application;

[0037] Figure 5 A schematic diagram of still another bipolar photovoltaic system provided by an embodiment of the present application;

[0038] Figure 6 A schematic diagram of a redundant protection using the maximum value of an absolute value provided by an embodiment of the present application;

[0039] Figure 7 A schematic diagram of still another bipolar photovoltaic system provided by an embodiment of the present application;

[0040] Figure 8 A schematic diagram of another bipolar photovoltaic system provided by an embodiment of the present application;

[0041] Figure 9A schematic diagram of a power supply system provided by an embodiment of the present application;

[0042] Figure 10 A schematic diagram of a bipolar power supply system in the field of fans provided by an embodiment of the present application;

[0043] Figure 11 A schematic diagram of a bipolar power supply system in the field of energy storage provided by an embodiment of the present application;

[0044] Figure 12 A flow chart of a protection method for a bipolar photovoltaic system provided by an embodiment of the present application;

[0045] Figure 13 A flow chart of another protection method for a bipolar photovoltaic system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0046] The terms "first", "second", etc. in the following description are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0047] In addition, in the present application, the orientation terms such as "upper", "lower", etc. can include but are not limited to the orientation defined by the relative placement of the components in the drawings, and it should be understood that these directional terms can be relative concepts, which are used for relative description and clarification, and can be changed accordingly according to the change of the placement of the components in the drawings.

[0048] In the present application, unless otherwise specified and limited, the term "connection" should be understood broadly, for example, "connection" can be fixed connection, or detachable connection, or integral; can be directly connected, or indirectly connected through an intermediate medium. In addition, the term "coupling" can be an electrically connected manner for realizing signal transmission. "Coupling" can be direct electrical connection, or indirect electrical connection through an intermediate medium.

[0049] Bipolar photovoltaic system embodiments

[0050] In order for those skilled in the art to better understand the technical solutions provided by the embodiments of the present application, the bipolar photovoltaic system provided by the embodiments of the present application is introduced as follows.

[0051] Referring to Figure 1 The figure is a schematic diagram of a bipolar photovoltaic system provided by an embodiment of the present application.

[0052] The bipolar photovoltaic system provided by the embodiment of the present application is different from the traditional unipolar photovoltaic system in that the bipolar photovoltaic system comprises three bus bars, namely, a direct current positive bus bar BUS+, a neutral bus bar M and a direct current negative bus bar BUS-.

[0053] The input end of the power converter 200 is used to connect the photovoltaic array 100, the first output end of the power converter 200 is connected to the first end of the direct current positive bus bar BUS+, the second output end of the power converter 200 is connected to the first end of the neutral bus bar M, and the third output end of the power converter 200 is connected to the first end of the direct current negative bus bar BUS-.

[0054] Moreover, the bipolar photovoltaic system comprises at least two inverters, namely, a first inverter 300 and a second inverter 400.

[0055] The first input end of the first inverter 300 is connected to the second end of the direct current positive bus bar BUS+, and the second input end of the first inverter 300 is connected to the second end of the neutral bus bar M.

[0056] The first input end of the second inverter 400 is connected to the second end of the neutral bus bar M, and the second input end of the second inverter 400 is connected to the second end of the direct current negative bus bar BUS-.

[0057] For example, the voltage of BUS+ is +1500V, and the voltage of BUS- is -1500V, so the voltage level of the bipolar photovoltaic system is 1500V. However, the total voltage of the direct current bus bar after the series connection of BUS+ and BUS- is 3000V. Therefore, the bipolar photovoltaic system provided by the embodiment of the present application can be applied to 1500V safety regulations, thereby reducing the voltage resistance requirement of the power tube in the power converter and the inverter. For example, the voltage level of the input end of the first inverter 300 and the second inverter 400 is 1500V, the input voltage of the first inverter 300 is between the voltage of the neutral bus bar and the voltage of BUS+, and the input voltage of the second inverter 400 is between the voltage of BUS- and the voltage of the neutral bus bar. Generally, the neutral bus bar M is substantially equal to the ground potential. For example, when the M is equal to the ground potential, the input voltage of the first inverter 300 is 0-1500V, and the input voltage of the second inverter 400 is -1500V-0.

[0058] Therefore, the voltage resistance level of the power tube inside is reduced relative to the traditional 3000V input voltage. The bipolar photovoltaic system provided by the embodiment of the present application can effectively reduce the voltage level borne by the power device without reducing the total voltage of the bus bar, thereby facilitating the selection of the power device.

[0059] The load or energy storage battery can be connected between BUS+ and M or between BUS- and M, such as Figure 1As shown, the energy storage battery BAT1 is connected between the BUS+ and M, the energy storage battery BAT2 is connected between the BUS- and M, the load 1 is connected between the BUS+ and M, and the load 2 is connected between the BUS- and M.

[0060] In order to make the person skilled in the art better understand the advantages of the bipolar photovoltaic system provided by the embodiments of the present application, see Figure 2 , which is a schematic diagram of a conventional unipolar photovoltaic system.

[0061] The power converter 200 includes two output terminals, the first output terminal of the power converter 200 is connected to the DC positive bus BUS+, and the second output terminal of the power converter 200 is connected to the DC negative bus BUS-. Similarly, the inverter 1000 includes two input terminals, the first input terminal of the inverter 1000 is connected to the BUS+, and the second input terminal of the inverter 1000 is connected to the BUS-. The input terminal of the power converter 200 is connected to the photovoltaic array 100.

[0062] In comparison Figure 1 , and Figure 2 It can be found that Figure 2 As shown in the unipolar photovoltaic system, two DC buses are included, which are BUS+ and BUS-. If the total DC bus voltage continues to be 3000V, the voltage level connected to the input terminal of the inverter 1000 is 3000V, and the withstand voltage of the power tube inside the inverter 1000 is twice that of Figure 1 As shown in the single inverter, the withstand voltage of the power tube is twice. Therefore, Figure 1 As shown in the bipolar photovoltaic system, the voltage drop borne by the power device can be reduced, which is beneficial to the selection of the device.

[0063] Because the distance between the power converter and the subsequent inverter may be far in actual work, the loss on the power cable corresponding to the DC bus is relatively large. Therefore, in order to improve the power generation efficiency, it is necessary to reduce the loss as much as possible. Figure 1 The corresponding total DC bus voltage is 3000V, the higher the voltage, the smaller the corresponding current, and thus the loss on the DC bus can be reduced.

[0064] In order to meet the safety requirements, the voltage of BUS+ to ground, the voltage of BUS- to ground, and the voltage of M to ground cannot be greater than or equal to the preset threshold value, and each voltage needs to be strictly monitored to ensure the safety of the person and the equipment.

[0065] In order to ensure safe and reliable operation, the bipolar photovoltaic system provided in the embodiments of the present application is provided with a redundant protection mechanism, for example, two controllers are arranged to monitor the voltage of BUS+ to ground, the voltage of BUS- to ground and the voltage of M to ground, so that when one of the controllers fails, the other controller can reliably alarm. The redundant protection scheme provided in the embodiments of the present application is introduced below.

[0066] Referring to Figure 3 , the figure is a schematic diagram of another bipolar photovoltaic system provided in the embodiments of the present application.

[0067] The connection mode of the photovoltaic array 100, the power converter 200, the first inverter 300 and the second inverter 400 in the embodiments is the same as that of Figure 1 , and will not be described here again.

[0068] The bipolar photovoltaic system provided in the embodiments comprises, in addition to the power converter 200, the first inverter 300 and the second inverter 400, a first controller 300 and a second controller 400,

[0069] The first controller CPU1 is configured to output a first overvoltage alarm signal when at least one of the following conditions is met;

[0070] The second controller CPU1 is configured to output a second overvoltage alarm signal when at least one of the following conditions is met;

[0071] The at least one condition comprises that the voltage of BUS+ to ground is greater than or equal to a preset threshold, the voltage of BUS- to ground is greater than or equal to the preset threshold, or the voltage of M to ground is greater than or equal to the preset threshold. In the embodiments of the present application, the value range of the preset threshold is not specifically limited and can be set according to actual needs, for example, it can be set to 110% of the voltage level, for example, for a system with a voltage level of 1500V, the preset threshold can be set to 1650V, that is, when the voltage of BUS+ to ground is greater than or equal to 1650V, the first overvoltage alarm signal is output, indicating that the voltage of BUS+ to ground is too high and an overvoltage failure occurs.

[0072] It should be noted that the output of the first overvoltage alarm signal by the first controller CPU1 refers to the output of an effective overvoltage alarm signal, for example, if a high level indicates an overvoltage failure, then the output of the first overvoltage alarm signal by the first controller CPU1 in a high level represents that the first overvoltage alarm signal is output. If the first overvoltage alarm signal output by the first controller CPU1 is in a low level, it indicates that the first overvoltage alarm signal is invalid, that is, it is not effectively output and is not considered as an overvoltage failure. Similarly, the output of the second overvoltage alarm signal by the second controller CPU2 is similar.

[0073] If the low level indicates that an overvoltage fault occurs, the first controller CPU1 outputs the first overvoltage alarm signal with a low level, which represents that the first overvoltage alarm signal is valid. If the first overvoltage alarm signal output by the first controller CPU1 is high, it indicates that the first overvoltage alarm signal is invalid, i.e., not effectively output, and is not considered as an overvoltage fault. Similarly, the second controller CPU2 outputs the second overvoltage alarm signal.

[0074] That is, if the voltage of any one of the three DC buses BUS+, BUS- and M with respect to the ground is greater than or equal to the preset threshold, it is determined that an overvoltage fault occurs, and an alarm needs to be given and measures need to be taken to reduce the voltage to below the preset threshold.

[0075] The application embodiment does not specifically limit the voltage acquisition method, which can be realized by a voltage sampling circuit or detected by an integrated voltage sensor.

[0076] The application embodiment does not specifically limit the specific value of the preset threshold, which is generally related to the voltage level of the input end of a single inverter, for example:

[0077] The application embodiment does not specifically limit the specific implementation of the first controller CPU1 and the second controller CPU2, which can be a single-chip microcomputer, a microprocessor, a field programmable gate array (FPGA) or a digital signal processor (DSP).

[0078] Generally, the first controller CPU1 and the second controller CPU2 work simultaneously to prevent the other one from normally performing the protection work when one of them fails.

[0079] Since the bipolar photovoltaic system provided by the application embodiment includes two controllers, i.e., the first controller and the second controller, the first controller and the second controller simultaneously monitor the voltages of the three DC buses BUS+, BUS- and M with respect to the ground. When the voltage of any one of the three DC buses with respect to the ground is greater than or equal to the preset threshold, the first controller and the second controller will output an overvoltage alarm signal. The first controller and the second controller realize redundant control, and if one of them fails, the overvoltage judgment will not be affected, and the system will take corresponding measures to reduce the voltage to below the preset threshold, thereby protecting the safety of the bipolar photovoltaic system, i.e., reducing the voltage to the requirement of safety regulations, thereby ensuring the safety of the human body and equipment.

[0080] It should be noted that the first controller CPU1 and the second controller CPU2 are equally important when protecting the bipolar photovoltaic system.

[0081] The following describes a feasible implementation mode in combination with the drawings. The first controller and the second controller monitor each other whether the other one is working normally in addition to monitoring the voltage of the three DC buses to the ground, and need to output a heartbeat alarm signal when an exception occurs.

[0082] Referring to Figure 4 The figure is a schematic diagram of another bipolar photovoltaic system provided by the embodiment of the application.

[0083] The first controller CPU1 in the bipolar photovoltaic system provided by the embodiment is further configured to output a first heartbeat alarm signal T1 when the second controller CPU2 is abnormal.

[0084] The second controller CPU2 is further configured to output a second heartbeat alarm signal T2 when the first controller CPU1 is abnormal.

[0085] In a specific implementation, the first controller CPU1 outputs the first heartbeat alarm signal T1 when the first controller CPU1 does not receive the heartbeat signal sent by the second controller; and the second controller CPU2 outputs the second heartbeat alarm signal T2 when the second controller CPU2 does not receive the heartbeat signal sent by the first controller.

[0086] It should be noted that the first controller CPU1 outputting the first heartbeat alarm signal means outputting an effective heartbeat alarm signal. For example, if a high level indicates that a heartbeat fault occurs, the first controller CPU1 outputs a high-level first heartbeat alarm signal to represent that the first heartbeat alarm signal is output. If the first heartbeat alarm signal output by the first controller CPU1 is a low level, it means that the first heartbeat alarm signal is invalid, i.e., not effectively output, and is not regarded as a heartbeat fault. Similarly, the second controller CPU2 outputting the second heartbeat alarm signal is similar.

[0087] On the contrary, if a low level indicates that a heartbeat fault occurs, the first controller CPU1 outputs a low-level first heartbeat alarm signal to represent that the effective first heartbeat alarm signal is output. If the first heartbeat alarm signal output by the first controller CPU1 is a high level, it means that the first heartbeat alarm signal is invalid, i.e., not effectively output, and is not regarded as a heartbeat fault. Similarly, the second controller CPU2 outputting the second heartbeat alarm signal is similar.

[0088] When working normally, the second controller CPU2 sends a heartbeat signal to the first controller CPU1. When the first controller CPU1 does not receive the heartbeat signal sent by the second controller CPU2, it is determined that the second controller CPU2 is abnormal, and the first controller CPU1 outputs the first heartbeat alarm signal T1, i.e., the first heartbeat alarm signal T1 is used to represent that the second controller CPU2 is abnormal.

[0089] Similarly, the first controller CPU1 sends a heartbeat signal to the second controller CPU2, and when the second controller CPU2 cannot receive the heartbeat signal sent by the first controller CPU1, it is determined that the first controller CPU1 is abnormal, and a second heartbeat alarm signal T2 is output, that is, the second heartbeat alarm signal T2 is used to represent that the first controller 400 is abnormal.

[0090] The specific embodiment of the heartbeat signal can be a pulse signal, that is, when the first controller CPU1 cannot receive the pulse signal sent by the second controller CPU2, it is determined that the second controller CPU2 is abnormal. Similarly, when the second controller CPU2 cannot receive the pulse signal sent by the first controller CPU1, it is determined that the first controller CPU1 is abnormal. That is, when the first controller CPU1 and the second controller CPU2 monitor that the pulse signal sent by the other party disappears, it is determined that the other party is abnormal, and the corresponding heartbeat alarm signal is output.

[0091] In addition, the bipolar photovoltaic system provided by the embodiment of the present application can also include a logic circuit 2000.

[0092] The first controller CPU1 is connected to the logic circuit 2000, and the second controller CPU2 is also connected to the logic circuit 2000.

[0093] The logic circuit 2000 is used to block the drive pulse signal to the power converter 200 when at least one alarm signal is received, wherein the at least one alarm signal includes the first overvoltage alarm signal S1, the second overvoltage alarm signal S2, the first heartbeat alarm signal T1 or the second heartbeat alarm signal T2.

[0094] In normal operation, the logic circuit 2000 sends a drive pulse signal to each power tube in the power converter 200, for example, a drive pulse signal can be sent to the gate of the power tube, so as to control the switching state of each power tube, so that the power converter 200 completes the voltage conversion. The specific implementation form of the power converter 200 is not limited in the embodiment of the present application, for example, the power converter 200 can include a boost circuit, which boosts the output voltage of the photovoltaic array 100 and provides an input end for the subsequent inverter.

[0095] However, when the logic circuit 2000 receives any alarm signal, the power converter 200 needs to be controlled to stop working, and specifically, the drive pulse signal to the power converter 200 can be blocked, and one possible implementation form is that all drive pulse signals sent to the power converter 200 are set to low level. That is, when the voltage of any DC bus to ground is greater than or equal to a preset threshold, or when any controller is abnormal, the logic circuit 2000 blocks the drive pulse signal of the power converter 200, so as to protect.

[0096] The embodiment of the present application does not specifically limit the specific implementation form of the logic circuit 2000, for example, can be a complex programmable logic device (CPLD) or FPGA.

[0097] The following takes the logic circuit provided by the embodiment of the present application as the CPLD as an example for introduction.

[0098] Referring to Figure 5 , the figure is a schematic diagram of another bipolar photovoltaic system provided by the embodiment of the present application.

[0099] Figure 5 The difference between Figure 4 is that the logic circuit in Figure 5 is implemented by the CPLD.

[0100] The embodiment of the present application does not specifically limit whether the logic operation of the CPLD 2000 is the logic or operation or the logic and operation.

[0101] The following respectively introduces two specific implementation modes.

[0102] The first kind is that the logic operation is the logic or operation.

[0103] The logic or operation is suitable for each alarm signal being high level effective, and the CPLD 2000 is specifically used for performing the logic or operation on the first overvoltage alarm signal S1, the second overvoltage alarm signal S2, the first heartbeat alarm signal T1 and the second heartbeat alarm signal T2, that is, performing the logic or operation on the four alarm signals, and blocking the driving pulse signal to the power converter 200 when the result of the logic or operation is true. For example, the high level corresponds to the logic 1, and the low level corresponds to the logic 0, then when the alarm signal corresponding to the logic 1 exists, the result after the logic or is 1, that is, the CPLD 2000 blocks the driving pulse signal to the power converter 200. For example, the overvoltage fault occurs, the first overvoltage alarm signal S1 is 1, the second overvoltage alarm signal S2 is 1, the two heartbeat signals are normal, that is, the first heartbeat alarm signal T1 is 0 and the second heartbeat alarm signal T2 is 0, then the result of the logic or operation of the CPLD 2000 is 1, and the driving pulse signal to the power converter 200 is blocked.

[0104] The second kind is that the logic operation is the logic and operation.

[0105] The logical AND operation is suitable when all alarm signals are active low. Specifically, the CPLD2000 performs a logical AND operation on the first overvoltage alarm signal S1, the second overvoltage alarm signal S2, the first heartbeat alarm signal T1, and the second heartbeat alarm signal T2. That is, it performs a logical AND operation on all four alarm signals. When the result of the logical AND operation is false, the drive pulse signal to the power converter 200 is blocked. For example, a high level corresponds to logic 1, and a low level corresponds to logic 0. If one alarm signal corresponds to 0, the result of the logical AND operation is 0, meaning the CPLD2000 blocks the drive pulse signal to the power converter 200. For example, when the maximum absolute value monitored by the first controller CPU1 is greater than a preset threshold, the first overvoltage alarm signal S1 is 0, the second overvoltage alarm signal S2 is 0, and both heartbeat signals are normal (i.e., the first heartbeat alarm signal T1 is 1, and the second heartbeat alarm signal T2 is 1). The result of the logical OR operation of the CPLD2000 is 0, thus blocking the drive pulse signal to the power converter 200.

[0106] For example, when the logical operation is a logical AND operation, when the first controller CPU1 receives a heartbeat signal from the second controller CPU2, the first heartbeat alarm signal T1 output by the first controller CPU1 is at a high level; when the first controller CPU1 does not receive a heartbeat signal from the second controller CPU2, the first heartbeat alarm signal T1 output by the first controller CPU1 is at a low level. The second controller CPU2 outputs a second heartbeat alarm signal T1 in a similar manner, and will not be described in detail here.

[0107] Since low-level signals have stronger anti-interference capabilities than high-level signals, in order to better achieve redundant protection, each alarm signal can use a low level as the effective signal, and the logic circuit can use a logical OR operation.

[0108] The following describes the specific method by which the first controller implements overvoltage detection.

[0109] One possible implementation is that, since the voltage of the DC bus to ground may be positive or negative during actual operation, the first controller needs to compare the absolute values ​​of the voltages of the three DC buses to ground with preset thresholds respectively. That is, when at least one of the absolute values ​​of the voltages of the positive DC bus to ground, the negative DC bus to ground, or the neutral bus to ground is greater than or equal to the preset threshold, the first controller outputs a first overvoltage alarm signal.

[0110] Another simpler and easier-to-implement method is as follows: The first controller first obtains the maximum absolute value of the voltages to ground of the three DC buses, compares the maximum absolute value with a preset threshold, and if the maximum absolute value is greater than or equal to the preset threshold, it indicates an overvoltage fault, and the first overvoltage alarm signal S1 is output. That is, the first controller outputs the first overvoltage alarm signal S1 when the maximum absolute value of the voltages to ground of the DC positive bus, the DC negative bus, and the neutral bus is greater than or equal to the preset threshold.

[0111] The following describes the specific method by which the second controller implements overvoltage detection.

[0112] One possible implementation is that, since the voltage of the DC bus to ground may be positive or negative during actual operation, the second controller needs to compare the absolute values ​​of the voltages of the three DC buses to ground with preset thresholds respectively. That is, when at least one of the absolute values ​​of the voltages of the positive DC bus to ground, the negative DC bus to ground, or the neutral bus to ground is greater than or equal to the preset threshold, the second controller outputs a second overvoltage alarm signal S2.

[0113] Another simpler and easier-to-implement method is as follows: the second controller first obtains the maximum absolute value of the voltages to ground of the three DC buses, compares the maximum absolute value with a preset threshold, and if the maximum absolute value is greater than or equal to the preset threshold, it indicates an overvoltage fault, and then outputs a second overvoltage alarm signal S2. That is, the second controller outputs the second overvoltage alarm signal S2 when the maximum absolute value of the voltages to ground of the DC positive bus, the DC negative bus, and the neutral bus is greater than or equal to the preset threshold.

[0114] In practical implementation, the voltages of the three DC buses to ground can be obtained directly, or the voltages of the positive DC bus to the neutral bus and the neutral bus to ground can be obtained. Then, based on the voltages of BUS+ to M and M to ground, the voltage of BUS+ to ground can be obtained. Since the voltage of BUS+ to M is a half-bus voltage, similarly, the voltage of BUS- to M is also a half-bus voltage. Half-bus voltages are generally voltages that need to be detected in photovoltaic systems. Therefore, this embodiment can utilize the half-bus voltages to obtain the voltages of BUS+ to ground, BUS- to ground, and M to ground. A specific implementation method is described below with reference to the accompanying drawings.

[0115] See Figure 6 The figure is a schematic diagram of a method for redundancy protection using the maximum absolute value provided in an embodiment of this application.

[0116] The bipolar photovoltaic system provided in this application embodiment also includes a voltage sampling circuit 3000.

[0117] The voltage sampling circuit 3000 is configured to sample the voltage of the positive DC bus relative to the neutral bus, the voltage of the negative DC bus relative to the neutral bus, and the voltage of the neutral bus relative to the ground. It should be understood that the voltage sampling circuit can be configured to sample the voltage of each of the three DC buses relative to the ground, or the voltage sampling circuit can be shared by the three DC buses. The voltage sampling circuit sends the sampled voltage of BUS+ relative to M, the voltage of BUS- relative to the ground, and the voltage of M relative to the ground to the first controller CPU1 and the second controller CPU2.

[0118] The first controller CPU1 and the second controller CPU2 are both configured to obtain the voltage of the positive DC bus BUS+ relative to the ground based on the voltage of the positive DC bus BUS+ relative to the neutral bus M and the voltage of the neutral bus M relative to the ground, and obtain the voltage of the negative DC bus BUS- relative to the ground based on the voltage of the negative DC bus BUS- relative to the neutral bus M and the voltage of the neutral bus M relative to the ground.

[0119] Specifically, the voltage of BUS+ relative to M and the voltage of M relative to the ground are summed to obtain the voltage of BUS+ relative to the ground. The voltage of BUS- relative to M and the voltage of M relative to the ground are summed to obtain the voltage of BUS- relative to the ground.

[0120] In addition, the first controller CPU1 and the second controller CPU2 can obtain the absolute values of the voltage of the positive DC bus relative to the ground, the voltage of the negative DC bus relative to the ground, and the voltage of the neutral bus relative to the ground by using an absolute value function. The first controller CPU1 and the second controller CPU2 can obtain the maximum value of the absolute values of the voltage of the positive DC bus relative to the ground, the voltage of the negative DC bus relative to the ground, and the voltage of the neutral bus relative to the ground by using a maximum value function. It should be understood that the maximum value of the absolute values of the voltage of the three DC buses relative to the ground can be the absolute value of the voltage of any one of the DC buses relative to the ground, for example, the absolute value of the voltage of BUS+ relative to the ground can be the maximum, or the absolute value of the voltage of M relative to the ground can be the maximum, or the absolute value of the voltage of BUS- relative to the ground can be the maximum. Therefore, in order to more simply determine whether overvoltage occurs, it can not be necessary to compare the absolute values of the voltages of the three buses relative to the ground with a preset threshold, but it can be necessary to compare the maximum value of the absolute values with the preset threshold to determine whether overvoltage occurs.

[0121] In addition, the first controller CPU1 and the second controller CPU2 can compare the maximum value of the absolute values with a preset threshold, and when the maximum value of the absolute values is greater than or equal to the preset threshold, an overvoltage alarm signal is output. That is, when the first controller CPU1 determines that the maximum value of the absolute values is greater than or equal to the preset threshold, the first overvoltage alarm signal S1 is output. When the second controller CPU2 determines that the maximum value of the absolute values is greater than or equal to the preset threshold, the second overvoltage alarm signal S2 is output.

[0122] The first controller CPU1 and the second controller CPU2 compare the maximum value of the absolute value with the preset threshold value respectively, that is, only one size is determined, which is simple and convenient, and the three DC bus voltages are not compared with the preset threshold value respectively.

[0123] For the detection of the heartbeat of the other controller by the first controller CPU1 and the second controller CPU2, a heartbeat module can be included in each controller, which is used to generate a heartbeat signal and send the generated heartbeat signal to the other controller, so as to facilitate the other controller to monitor whether the heartbeat signal is normal, and when it is not normal, it is determined that an exception occurs. Generally, when the heartbeat signal of the other controller is monitored to disappear, it is determined that the other controller has an exception, and a corresponding heartbeat alarm signal is output.

[0124] When the CPLD 2000 receives any valid alarm signal, the driving pulse signal to the power converter 200 is blocked.

[0125] From Figure 6 It can be seen that the voltage signals input by the first controller CPU1 and the second controller CPU2 are the same, that is, the three DC bus voltages are monitored. Therefore, redundant protection for overvoltage can be realized. Moreover, the two controllers monitor the heartbeat signal of the other controller, so as to monitor whether the other controller can work normally, and when one of them has a problem, an alarm is given in time, and the CPLD 2000 performs a protection action.

[0126] The bipolar photovoltaic system provided by the above embodiment of the application includes two controllers, and the two controllers simultaneously monitor whether the three DC bus voltages are overvoltage, and when overvoltage occurs in any bus, an alarm is given, and the logic circuit blocks the driving pulse signal to the power converter, and the power converter stops working, thereby avoiding the overvoltage of the output voltage of the power converter to affect the inverter in the rear stage, and further avoiding affecting the load. Since the two controllers work simultaneously, the redundancy of the two controllers can be realized, so that when overvoltage failure occurs, comprehensive and effective identification and protection can be ensured. In addition, the two controllers can also monitor the heartbeat signal of the other controller, and when the heartbeat signal of one of them disappears, an alarm is given, and the logic circuit also blocks the driving pulse signal of the power converter, so that the power converter stops working and protects the bipolar photovoltaic system.

[0127] In actual application, the alternating current output by the first inverter 300 and the second inverter 400 can be connected to the alternating current grid, and the grid can be connected through two independent isolation transformers or a multi-winding transformer. The following will be introduced respectively with reference to the accompanying drawings.

[0128] Referring to Figure 7 , the figure is a schematic diagram of another bipolar photovoltaic system provided by the embodiment of the application.

[0129] Figure 7 The output end of the first inverter 300 is connected to the first transformer 500, that is, the first inverter 300 is connected to the power grid through the first transformer 500.

[0130] The output end of the second inverter 400 is connected to the second transformer 600, that is, the second inverter 400 is connected to the power grid through the second transformer 600.

[0131] The functions of the first transformer 500 and the second transformer 600 are mainly to realize electrical isolation, and can also realize voltage transformation.

[0132] In addition, in order to save space and reduce cost, the first inverter 300 and the second inverter 400 can share the same transformer, that is, a multi-winding transformer.

[0133] Referring to Figure 8 , which is a schematic diagram of another bipolar photovoltaic system provided by the embodiment of the present application.

[0134] Figure 8 In the figure, the output end of the first inverter 300 and the output end of the second inverter 400 are both connected to the multi-winding transformer 700, wherein the output end of the first inverter 300 is connected to the first primary winding of the multi-winding transformer 700, the output end of the second inverter 400 is connected to the second primary winding of the multi-winding transformer 700, and the secondary winding of the multi-winding transformer 700 is connected to the power grid. That is, the first inverter 300 and the second inverter 400 are connected to two different primary windings of the multi-winding transformer 700, and the two different primary windings share the same secondary winding.

[0135] Power system embodiment

[0136] The above embodiment introduces an implementation scheme of a bipolar power system applied to a photovoltaic power generation field, and the redundancy protection scheme provided by the embodiment of the present application is not only suitable for a bipolar photovoltaic system, but also suitable for a wind power bipolar power generation system and a storage bipolar system. The following describes the respective figures.

[0137] Referring to Figure 9 , which is a schematic diagram of a power system provided by the embodiment of the present application.

[0138] The power system provided by the embodiment of the present application comprises three direct-current buses BUS+, M and BUS-, and further comprises two inverters and two controllers.

[0139] The first end of the direct-current positive bus BUS+ is used for connecting the first output end of the direct-current power supply 4000, the first end of the neutral bus is used for connecting the second output end of the direct-current power supply 4000, and the first end of the direct-current negative bus BUS- is used for connecting the third output end of the direct-current power supply 4000.

[0140] The first input end of the first inverter 300 is connected to the second end of the direct current positive bus BUS+, and the second input end of the first inverter 300 is connected to the second end of the neutral bus M;

[0141] The first input end of the second inverter 400 is connected to the second end of the neutral bus M, and the second input end of the second inverter 400 is connected to the second end of the direct current negative bus BUS-;

[0142] The first controller CPU1 is configured to output a first overvoltage alarm signal when at least one of the following conditions is met:

[0143] The second controller CPU2 is configured to output a second overvoltage alarm signal when at least one of the following conditions is met:

[0144] The at least one condition includes that the voltage of the direct current positive bus BUS+ to ground is greater than or equal to a preset threshold, the voltage of the direct current negative bus BUS- to ground is greater than or equal to the preset threshold, or the voltage of the neutral bus M to ground is greater than or equal to the preset threshold.

[0145] The bipolar photovoltaic system provided in the embodiment includes two controllers, i.e., the first controller and the second controller. The first controller and the second controller simultaneously monitor the voltages of the three direct current buses BUS+, BUS- and M to ground. When the voltage of any one of the direct current buses to ground is greater than or equal to a preset threshold, the first controller and the second controller will both output an overvoltage alarm signal. The first controller and the second controller realize redundant control. If one of the controllers fails, the overvoltage judgment will not be affected, and the system will take corresponding measures to reduce the voltage to below the preset threshold, thereby protecting the safety of the bipolar photovoltaic system, i.e., reducing the voltage to the requirement of safety regulations, thereby ensuring the safety of personnel and equipment.

[0146] The bipolar power supply system provided in the embodiment can reduce the voltage drop borne by the power device, which is beneficial to the selection of the device. Because in actual work, the distance between the power converter and the subsequent inverter can be relatively far, the loss on the power cable corresponding to the direct current bus is relatively large. Therefore, in order to improve the power generation efficiency, it is necessary to reduce the loss as much as possible. Because the direct current bus adopts three buses and corresponds to two inverters, the voltage corresponding to each inverter is half of the total voltage of the direct current bus, i.e., the half bus voltage. Therefore, the voltage borne can be reduced. However, the system does not reduce the total voltage of the direct current bus, for example, continues to be 3000V. Because the higher the total voltage of the direct current bus is, the smaller the corresponding current is, and the smaller the current is, the lower the corresponding loss is, the power consumption on the direct current bus can be reduced.

[0147] The bipolar power supply system provided by the embodiment of the present application can be applied in the photovoltaic power generation field, that is, the direct current power source is derived from any one of the following: photovoltaic power generation, wind power generation or energy storage battery. In the wind power generation field, for example, the source of the direct current power supply connected with the power converter can be the fan 800.

[0148] Referring to Figure 10 , the figure is a schematic diagram of a bipolar power supply system in the fan field provided by the embodiment of the present application.

[0149] The direct current output by the fan 800 is converted by the power converter 200 and then output to the three direct current buses BUS+, M and BUS-. It should be understood that if the fan 800 is internally integrated with a power conversion circuit, the power converter 200 in the system can be removed and is not a necessary device. If the power generated by the fan 800 needs to be connected to the power grid, the output ends of the first inverter 300 and the second inverter 400 can be connected to the power grid through a transformer, and the specific implementation of the transformer can be referred to Figure 7 and Figure 8 The corresponding two specific implementation modes will not be described here.

[0150] In addition, referring to Figure 11 , the figure is a schematic diagram of a bipolar power supply system in the energy storage field provided by the embodiment of the present application.

[0151] The direct current output by the energy storage battery 900 is converted by the power converter 200 and then output to the three direct current buses BUS+, M and BUS-. If the direct current output by the energy storage battery 900 needs to be connected to the power grid, the power converter 200 needs to be used for voltage conversion first, for example, the power converter 200 includes a boost circuit, the output voltage of the energy storage battery 900 is boosted and then output, the first inverter 300 is used for converting the direct current between BUS+ and M into alternating current, and the second inverter 400 is used for converting the direct current between M and BUS- into alternating current. The output ends of the first inverter 300 and the second inverter 400 can be connected to the power grid through a transformer, and the specific implementation of the transformer can be referred to Figure 7 and Figure 8 The corresponding two specific implementation modes will not be described here.

[0152] No matter whether it is a fan, photovoltaic or energy storage battery, the power supply system provided by the embodiment of the present application can realize redundancy protection, which can realize redundancy protection of overvoltage and redundancy protection of two controllers. The redundancy protection of the power supply system shown in Figure 10 and Figure 11 will be briefly described below, and the detailed process can be referred to the specific description of the embodiment of the photovoltaic system.

[0153] The first controller is further configured to output a first heartbeat alarm signal when the second controller is abnormal.

[0154] The second controller is further configured to output a second heartbeat alarm signal when the first controller is abnormal.

[0155] The first controller is specifically configured to detect that the second controller is abnormal when the first controller does not receive the heartbeat signal sent by the second controller.

[0156] The second controller is specifically configured to detect that the first controller is abnormal when the second controller does not receive the heartbeat signal sent by the first controller.

[0157] The first controller is specifically configured to output a first overvoltage alarm signal when a maximum value of an absolute value of a DC positive bus voltage, an absolute value of a DC negative bus voltage and an absolute value of a neutral bus voltage is greater than or equal to a preset threshold value.

[0158] The second controller is specifically configured to output a second overvoltage alarm signal when at least one of the absolute value of the DC positive bus voltage, the absolute value of the DC negative bus voltage or the absolute value of the neutral bus voltage is greater than or equal to the preset threshold value.

[0159] The method further includes: a logic circuit connected to the first controller and the second controller; and the logic circuit is configured to block a driving pulse signal to the power converter when at least one alarm signal is received.

[0160] The at least one alarm signal includes the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal or the second heartbeat alarm signal.

[0161] It should be noted that the power converter, the first inverter and the second inverter introduced in each of the above embodiments can realize bidirectional work, that is, energy can be transferred from the power converter to the inverter, and energy can also be transferred from the inverter to the power converter. For example, for an energy storage system, the energy of the power grid can be used to charge the energy storage battery.

[0162] A protection method embodiment

[0163] Based on the bipolar photovoltaic system provided in the above embodiments, the embodiment of the present application further provides a protection method of a bipolar photovoltaic system, which will be described in detail below with reference to the accompanying drawings.

[0164] Referring to Figure 12 The figure is a flowchart of a protection method of a bipolar photovoltaic system provided in the embodiment of the present application.

[0165] The protection method of the bipolar photovoltaic system provided in the embodiment includes: a first input end of a first inverter is connected to a second end of a direct current positive bus, and a second input end of the first inverter is connected to a second end of a neutral bus; a first input end of a second inverter is connected to the second end of the neutral bus, and a second input end of the second inverter is connected to a second end of a direct current negative bus; for a schematic diagram of the bipolar photovoltaic system, refer to the corresponding drawing of the system embodiment, which will not be described here.

[0166] S1201: monitoring a first overvoltage alarm signal output by a first controller and a second overvoltage alarm signal output by a second controller.

[0167] The first controller outputs the first overvoltage alarm signal when at least one of the following conditions is met:

[0168] The second controller outputs the second overvoltage alarm signal when at least one of the following conditions is met:

[0169] The at least one condition includes: a voltage of the direct current positive bus with respect to ground is greater than or equal to a preset threshold, a voltage of the direct current negative bus with respect to ground is greater than or equal to the preset threshold, or a voltage of the neutral bus with respect to ground is greater than or equal to the preset threshold.

[0170] It should be understood that when overvoltage occurs in the voltage of any one of the direct current buses with respect to ground, the first overvoltage alarm signal output by the first controller is valid, which has been introduced in the embodiment of the photovoltaic system and will not be described here. Similarly, the second overvoltage alarm signal output by the second controller is also valid, and when an invalid signal is output, it indicates that no overvoltage occurs.

[0171] S1202: determining whether a fault occurs in the bipolar photovoltaic system according to the first overvoltage alarm signal or the second overvoltage alarm signal.

[0172] When overvoltage fault occurs, the drive pulse signal of the power converter can be blocked, that is, the power transmission from the power converter to the inverter is stopped, and the power converter stops working, so as to protect the electrical equipment in the subsequent stage, such as the inverter and the load.

[0173] Since the protection method of the bipolar photovoltaic system provided in the embodiment, the voltages of three direct current buses, that is, the voltages of the three direct current buses BUS+, BUS- and M with respect to ground are monitored by two controllers at the same time, when the voltage of any one of the direct current buses with respect to ground is greater than or equal to a preset threshold, the first controller and the second controller will both output an overvoltage alarm signal, and if a fault occurs in one of the controllers, the overvoltage judgment will not be affected, so as to realize redundant protection, and the system will take corresponding measures to reduce the voltage to below the preset threshold, so as to protect the safety of the bipolar photovoltaic system, that is, to reduce the voltage to the requirement of safety regulations, so as to ensure the safety of the human body and the equipment.

[0174] In addition, the protection method provided by the embodiment of the application can further monitor the heartbeat signals of the two controllers, so as to determine whether the two controllers work normally. The method of the embodiment of the application can be executed in a logic circuit, such as a CPLD or an FPGA, or can be executed in a processor, and the embodiment of the application is not limited in this regard.

[0175] Referring to Figure 13 FIG. 4 is a flowchart of another protection method of a bipolar photovoltaic system provided by the embodiment of the application.

[0176] S1301: receiving a first overvoltage alarm signal and a first heartbeat signal sent by a first controller;

[0177] S1302: receiving a second overvoltage alarm signal and a second heartbeat signal sent by a second controller.

[0178] It should be understood that S1301 and S1302 have no sequence. In addition, the first overvoltage alarm signal and the first heartbeat signal also have no sequence, and can exist simultaneously or not simultaneously, for example, the voltages of three DC buses are normal, but the heartbeat of one of the controllers is abnormal. The embodiment of the application is not limited in this regard.

[0179] When the first controller outputs the first heartbeat alarm signal or the second controller outputs the second heartbeat alarm signal, it is determined that the bipolar photovoltaic system has a fault; the first controller outputs the first heartbeat alarm signal when the second controller is abnormal; and the second controller outputs the second heartbeat alarm signal when the first controller is abnormal.

[0180] S1303: blocking a driving pulse signal to a power converter when at least one alarm signal is received;

[0181] The at least one alarm signal includes the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal or the second heartbeat alarm signal.

[0182] The valid alarm signal is a high level or a low level, and the high level or the low level is valid, for example, the high level represents that the alarm signal is valid, and when the high level alarm signal is received, it is indicated that the valid alarm signal is received, for example, when the high level voltage alarm signal is received, it is indicated that the overvoltage fault occurs, and when the high level heartbeat alarm signal is received, it is indicated that one of the controllers is abnormal. If the invalid alarm signal is received, it is equivalent to that no alarm signal is received, for example, when the high level is valid, if the low level signal is received, it is equivalent to that no alarm signal is received.

[0183] The first controller outputs a first overvoltage alarm signal when the DC positive bus voltage, the DC negative bus voltage or the neutral bus voltage is greater than or equal to a preset threshold value, specifically comprising:

[0184] The maximum value among the absolute value of the DC positive bus voltage, the absolute value of the DC negative bus voltage and the absolute value of the neutral bus voltage is obtained; when the maximum value is greater than or equal to a preset threshold value, a first overvoltage alarm signal is output.

[0185] The second controller outputs a second overvoltage alarm signal when the DC positive bus voltage, the DC negative bus voltage or the neutral bus voltage is greater than or equal to a preset threshold value, specifically comprising:

[0186] The maximum value among the absolute value of the DC positive bus voltage, the absolute value of the DC negative bus voltage and the absolute value of the neutral bus voltage is obtained; when the maximum value is greater than or equal to a preset threshold value, a second overvoltage alarm signal is output.

[0187] The protection method provided by the embodiments of the present application can further enable the two controllers to monitor the heartbeat signals of each other, and when the heartbeat signal of one side disappears, an alarm is given, and the logic circuit can block the driving pulse signal of the power converter to stop the power converter from working, thereby protecting the bipolar photovoltaic system.

[0188] It should be understood that, in the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" is used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, "A and / or B" can represent three cases of only A, only B and A and B existing at the same time, wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects. "At least one of the following" or the like refers to any combination of these items, including single item or any combination of multiple items. For example, at least one of a, b or c can represent a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b and c can be single or multiple.

[0189] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the foregoing embodiments of the present application have been described in detail, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A bipolar photovoltaic system, characterized in that, At least including: Power converter, first inverter, second inverter, first controller and second controller; The input terminal of the power converter is used to connect to the photovoltaic array, the first output terminal of the power converter is connected to the first terminal of the DC positive bus, the second output terminal of the power converter is connected to the first terminal of the neutral bus, and the third output terminal of the power converter is connected to the first terminal of the DC negative bus. The first input terminal of the first inverter is connected to the second terminal of the DC positive bus, and the second input terminal of the first inverter is connected to the second terminal of the neutral bus. The first input terminal of the second inverter is connected to the second terminal of the neutral bus, and the second input terminal of the second inverter is connected to the second terminal of the DC negative bus. The first controller is configured to output a first overvoltage alarm signal when at least one of the following conditions is met; The second controller is configured to output a second overvoltage alarm signal when at least one of the following conditions is met; The at least one of the following includes: the DC positive bus voltage to ground is greater than or equal to a preset threshold, the DC negative bus voltage to ground is greater than or equal to the preset threshold, or the neutral bus voltage to ground is greater than or equal to the preset threshold; The first controller is further configured to output a first heartbeat alarm signal when the second controller malfunctions; The second controller is also configured to output a second heartbeat alarm signal when the first controller malfunctions; The bipolar photovoltaic system further includes: a logic circuit connected to the first controller and the second controller; The logic circuit is configured to block the drive pulse signal to the power converter when at least one of the following alarm signals is received; The at least one alarm signal includes: a first overvoltage alarm signal, a second overvoltage alarm signal, a first heartbeat alarm signal, or a second heartbeat alarm signal.

2. The photovoltaic system according to claim 1, characterized in that, The first controller is specifically used to output a first heartbeat alarm signal when it does not receive a heartbeat signal from the second controller; The second controller is specifically used to output a second heartbeat alarm signal when it does not receive a heartbeat signal from the first controller.

3. The photovoltaic system according to claim 1, characterized in that, The logic circuit is a complex programmable logic device (CPLD); the CPLD is specifically used to perform a logical OR operation on the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, and the second heartbeat alarm signal, and when the result of the logical OR operation is true, it blocks the drive pulse signal supplied to the power converter.

4. The photovoltaic system according to claim 1, characterized in that, The logic circuit is a complex programmable logic device (CPLD); the CPLD is specifically used to perform a logical AND operation on the first overvoltage alarm signal, the second overvoltage alarm signal, the first heartbeat alarm signal, and the second heartbeat alarm signal, and when the result of the logical AND operation is false, the drive pulse signal supplied to the power converter is blocked.

5. The photovoltaic system according to any one of claims 1-4, characterized in that, The first controller is specifically configured to compare the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground with the preset threshold, and output the first overvoltage alarm signal when at least one of the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, or the neutral bus voltage to ground is greater than or equal to the preset threshold.

6. The photovoltaic system according to any one of claims 1-4, characterized in that, The first controller is specifically used to obtain the maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground, and outputs the first overvoltage alarm signal when the maximum value is greater than or equal to the preset threshold.

7. The photovoltaic system according to any one of claims 1-4, characterized in that, The second controller is specifically used to compare the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground with the preset threshold. When at least one of the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground is greater than or equal to the preset threshold, the second overvoltage alarm signal is output.

8. The photovoltaic system according to any one of claims 1-4, characterized in that, The second controller is specifically used to obtain the maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground. When the maximum value is greater than or equal to the preset threshold, the second overvoltage alarm signal is output.

9. The photovoltaic system according to any one of claims 1-4, characterized in that, Also includes: Voltage sampling circuit; The voltage sampling circuit is used to collect the voltage between the DC positive bus and the neutral bus, the voltage between the DC negative bus and the neutral bus, and the voltage between the neutral bus and ground. Both the first controller and the second controller are specifically configured to obtain the DC positive bus voltage to ground based on the voltage of the DC positive bus to the neutral bus and the voltage of the neutral bus to ground, and to obtain the DC negative bus voltage to ground based on the voltage of the DC negative bus to the neutral bus and the voltage of the neutral bus to ground.

10. A power supply system, characterized in that, include: First inverter, second inverter, first controller, and second controller; The first end of the DC positive bus is used to connect to the first output terminal of the DC power supply, the first end of the neutral bus is used to connect to the second output terminal of the DC power supply, and the first end of the DC negative bus is used to connect to the third output terminal of the DC power supply. The first input terminal of the first inverter is connected to the second terminal of the DC positive bus, and the second input terminal of the first inverter is connected to the second terminal of the neutral bus. The first input terminal of the second inverter is connected to the second terminal of the neutral bus, and the second input terminal of the second inverter is connected to the second terminal of the DC negative bus. The first controller is configured to output a first overvoltage alarm signal when at least one of the following conditions is met; The second controller is configured to output a second overvoltage alarm signal when at least one of the following conditions is met; The at least one of the following includes: the DC positive bus voltage to ground is greater than or equal to a preset threshold, the DC negative bus voltage to ground is greater than or equal to the preset threshold, or the neutral bus voltage to ground is greater than or equal to the preset threshold; The first controller is also used to output a first heartbeat alarm signal when it detects an abnormality in the second controller; The second controller is also used to output a second heartbeat alarm signal when the first controller is detected to be malfunctioning; The power supply system also includes: Logic circuitry connected to the first controller and the second controller; The logic circuit is configured to block the drive pulse signal to the power converter when at least one of the following alarm signals is received; The at least one alarm signal includes: a first overvoltage alarm signal, a second overvoltage alarm signal, a first heartbeat alarm signal, or a second heartbeat alarm signal.

11. The power supply system according to claim 10, characterized in that, The DC power source is derived from any of the following: photovoltaic power generation, wind power generation, or energy storage battery.

12. The power supply system according to claim 10, characterized in that, The first controller is specifically used to detect an anomaly in the second controller when it does not receive a heartbeat signal from the second controller; The second controller is specifically used to detect an anomaly in the first controller when it does not receive a heartbeat signal from the first controller.

13. The power supply system according to any one of claims 10-12, characterized in that, The first controller is specifically used to obtain the maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground. When the maximum value is greater than or equal to the preset threshold, the first overvoltage alarm signal is output. The second controller is specifically used to obtain the maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground. When the maximum value is greater than or equal to the preset threshold, the second overvoltage alarm signal is output.

14. The power supply system according to any one of claims 10-12, characterized in that, The first controller is specifically configured to compare the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground with the preset threshold, and output the first overvoltage alarm signal when at least one of the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, or the neutral bus voltage to ground is greater than or equal to the preset threshold. The second controller is specifically used to compare the absolute value of the DC positive bus voltage to ground, the absolute value of the DC negative bus voltage to ground, or the absolute value of the neutral bus voltage to ground with the preset threshold, and output the second overvoltage alarm signal when at least one of the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, or the neutral bus voltage to ground is greater than or equal to the preset threshold.

15. A protection method for a bipolar photovoltaic system, characterized in that, The bipolar photovoltaic system includes: a first input terminal of a first inverter connected to the second terminal of a DC positive bus, and a second input terminal of the first inverter connected to the second terminal of a neutral bus; a first input terminal of a second inverter connected to the second terminal of the neutral bus, and a second input terminal of the second inverter connected to the second terminal of a DC negative bus. The method includes: Monitor the first overvoltage alarm signal output by the first controller and the second overvoltage alarm signal output by the second controller; Determine whether the bipolar photovoltaic system has malfunctioned based on the first overvoltage alarm signal or the second overvoltage alarm signal; The first controller outputs a first overvoltage alarm signal when at least one of the following conditions is met; the second controller outputs a second overvoltage alarm signal when at least one of the following conditions is met; the at least one condition includes: the DC positive bus voltage to ground is greater than or equal to a preset threshold, the DC negative bus voltage to ground is greater than or equal to the preset threshold, or the neutral bus voltage to ground is greater than or equal to the preset threshold; The method further includes: The bipolar photovoltaic system is determined to be faulty when the first controller outputs a first heartbeat alarm signal or the second controller outputs a second heartbeat alarm signal; the first controller outputs a first heartbeat alarm signal when the second controller is abnormal; the second controller outputs a second heartbeat alarm signal when the first controller is abnormal. When at least one of the following alarm signals is received, the drive pulse signal to the power converter is blocked; The at least one alarm signal includes: a first overvoltage alarm signal, a second overvoltage alarm signal, a first heartbeat alarm signal, or a second heartbeat alarm signal.

16. The method according to claim 15, characterized in that, The first controller outputs a first overvoltage alarm signal when the DC positive bus voltage to ground is greater than or equal to a preset threshold, the DC negative bus voltage to ground is greater than or equal to the preset threshold, or the neutral bus voltage to ground is greater than or equal to the preset threshold. Specifically, this includes: The maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground is obtained. When the maximum value is greater than or equal to the preset threshold, the first overvoltage alarm signal is output.

17. The method according to claim 15, characterized in that, The second controller outputs a second overvoltage alarm signal when the DC positive bus voltage to ground is greater than or equal to a preset threshold, the DC negative bus voltage to ground is greater than or equal to the preset threshold, or the neutral bus voltage to ground is greater than or equal to the preset threshold, specifically including: The maximum value among the absolute values ​​of the DC positive bus voltage to ground, the DC negative bus voltage to ground, and the neutral bus voltage to ground is obtained. When the maximum value is greater than or equal to the preset threshold, the second overvoltage alarm signal is output.

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