Photovoltaic power generation control method, main control device and photovoltaic system

Abstract

A photovoltaic power generation control method, a main control device and a photovoltaic system. The method comprises: sending a first communication signal, wherein the first communication signal comprises an adjustment instruction and an operation permission instruction, the adjustment instruction is used for controlling a power converter to adjust an output voltage characteristic value thereof, and the operation permission instruction is used for controlling the operating state of the power converter; a plurality of power converters are connected in series to form a photovoltaic string and are connected to an inverter; and when the power converter does not receive the operation permission instruction within a first preset time, an output of the power converter is in a limited state.

Description

Control method of photovoltaic power generation, master control device and photovoltaic system

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 202411018120.4, filed on July 26, 2024, and entitled "Control method of photovoltaic power generation, master control device and photovoltaic system", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of photovoltaic power generation, and in particular to a control method of photovoltaic power generation, a master control device and a photovoltaic system. BACKGROUND

[0004] Due to the renewable and clean nature of solar energy, photovoltaic power generation technology has developed rapidly. String-type photovoltaic systems have been widely used in the field of photovoltaic power generation due to their mature technology, high conversion efficiency and low price. In order to avoid the problem of loss of system power generation caused by the existence of the "barrel effect" of directly connected photovoltaic modules, a power converter is generally configured for each photovoltaic module. The outputs of multiple power converters are connected in series to form a photovoltaic string, which is then connected to the input end of an inverter. The power converter can adjust the output voltage and output current of the photovoltaic module to achieve maximum power point tracking of the photovoltaic module and improve the system power generation efficiency.

[0005] In order to ensure the safe operation of the system, the sum of the output voltages of the power converters on the photovoltaic string needs to be lower than the upper limit value of the direct current input voltage of the inverter. Therefore, it is necessary to set the output voltage characteristic value of the power converter to limit its output voltage characteristic. In related technologies, the output voltage characteristic value of the power converter is a fixed value and cannot be adjusted. Therefore, the power generation efficiency of the photovoltaic system is low. SUMMARY

[0006] According to various embodiments of the present application, a control method of photovoltaic power generation, a master control device and a photovoltaic system are provided.

[0007] In a first aspect, the embodiments of the present application propose a control method of photovoltaic power generation, which comprises:

[0008] sending a first communication signal; the first communication signal comprises an adjustment instruction and an allowed operation instruction, the adjustment instruction is used to control the power converter to adjust its output voltage characteristic value, and the allowed operation instruction is used to control the working state of the power converter; a plurality of power converters are connected in series to form a photovoltaic string and are connected with an inverter;

[0009] When the power converter does not receive the allowed operation instruction within a first preset time, the output of the power converter is in a limited state.

[0010] In some embodiments, the second communication signal comprises the run instruction and does not comprise the adjustment instruction before the first communication signal is sent;

[0011] The second communication signal is stopped from being sent and the first communication signal is started to be sent every second preset time or when there is a power converter in the voltage limiting state.

[0012] In some embodiments, the first preset time is less than the second preset time.

[0013] In some embodiments, the time interval between the last time the second communication signal is sent before the first communication signal is sent and the second communication signal is sent again is greater than the first preset time.

[0014] In some embodiments, the first communication signal is sent at least once within the first preset time since the second communication signal is stopped from being sent, the time interval between the first time the first communication signal is sent and the second communication signal is started to be sent again is less than the first preset time, and the time interval between the last time the first communication signal is sent and the second communication signal is sent last time before the first communication signal is sent is less than the first preset time.

[0015] In some embodiments, the method further comprises:

[0016] When there is a power converter in the photovoltaic string that has not received the first communication signal, the first communication signal is sent to the photovoltaic string again;

[0017] When there is no power converter in the photovoltaic string that has not received the first communication signal, the second communication signal is started to be sent to the photovoltaic string again.

[0018] In some embodiments, the control of the inverter determines whether there is a power converter in the photovoltaic string that has not received the first communication signal according to input electrical parameters of the inverter.

[0019] In some embodiments, when it is detected that the direct current input voltage and / or the direct current input current of the inverter abnormally decreases, it is determined that there is a power converter in the photovoltaic string that has not received the first communication signal.

[0020] In some embodiments, the first communication signal carries an adjustment coefficient, and the adjustment instruction controls the power converter to adjust the output voltage characteristic value according to the adjustment coefficient.

[0021] Or, the adjustment instruction controls the power converter to adjust the output voltage characteristic value according to a preset adjustment coefficient of the power converter.

[0022] In some embodiments, the controller controls the inverter to apply a perturbation to the DC input of the inverter, and determines whether there is a power converter in the voltage-limited state in the photovoltaic string connected to the inverter.

[0023] In some embodiments, the controller controls the inverter to apply a perturbation to the DC input of the inverter in the direction of increasing and / or decreasing the DC input voltage of the inverter, and determines whether there is a power converter in the voltage-limited state according to the change of the DC input power of the inverter before and after the perturbation.

[0024] In the second aspect, the embodiments of the present application provide an inverter applied to a photovoltaic system, the photovoltaic system further comprising at least one photovoltaic string connected to the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic DC power sources connected to the power converters correspondingly, and the inverter comprising:

[0025] a first signal sending module configured to send a first communication signal, the first communication signal comprising an adjustment instruction and an operation permission instruction, the adjustment instruction being used to control the power converter to adjust an output voltage characteristic value thereof, and the operation permission instruction being used to control a working state of the power converter;

[0026] When the power converter does not receive the operation permission instruction within a first preset time, the output of the power converter is in a limited state.

[0027] In the third aspect, the embodiments of the present application provide a master control device applied to a photovoltaic system, the photovoltaic system further comprising at least one photovoltaic string and an inverter connected to the photovoltaic string, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic DC power sources connected to the power converters correspondingly, and the master control device comprising:

[0028] a second signal sending module configured to send a first communication signal, the first communication signal comprising an adjustment instruction and an operation permission instruction, the adjustment instruction being used to control the power converter to adjust an output voltage characteristic value thereof, and the operation permission instruction being used to control a working state of the power converter;

[0029] When the power converter does not receive the operation permission instruction within a first preset time, the output of the power converter is in a limited state.

[0030] In some embodiments, the second signal sending module sends a second communication signal comprising the operation permission instruction and not comprising the adjustment instruction before sending the first communication signal.

[0031] The second signal sending module stops sending the second communication signal and starts sending the first communication signal every second preset time or when there is a power converter in the voltage-limited state.

[0032] In some embodiments, the second signal sending module sends the first communication signal at least once within a first preset time after stopping sending the second communication signal, and the time interval between the first time of sending the first communication signal and the time of resuming sending the second communication signal is less than the first preset time; the time interval between the last time of sending the first communication signal and the last time of sending the second communication signal before sending the first communication signal is less than the first preset time.

[0033] In some embodiments, the second signal sending module resumes sending the second communication signal to the photovoltaic string when there is no power converter in the photovoltaic string that has not received the first communication signal.

[0034] In some embodiments, the second signal sending module resumes sending the second communication signal to the photovoltaic string when there is no power converter in the photovoltaic string that has not received the first communication signal.

[0035] In some embodiments, the second signal sending module resumes sending the second communication signal to the photovoltaic string when there is no power converter in the photovoltaic string that has not received the first communication signal.

[0036] In some embodiments, the method further comprises:

[0037] The third signal sending module is configured to send an operation state query instruction, and the operation state query instruction is used to query a determination result of whether there is a power converter in the photovoltaic string that has not received the first communication signal.

[0038] In some embodiments, the method further comprises:

[0039] The fourth signal sending module is configured to send a state determination instruction, and the state determination instruction is used to control the inverter to determine whether there is a power converter in the photovoltaic string connected to the inverter that is in a voltage limiting state.

[0040] In a fourth aspect, an embodiment of the present application provides a photovoltaic system, comprising an inverter and at least one photovoltaic string connected to the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct-current power sources connected to the power converters correspondingly, and the inverter performs the steps of the method according to the first aspect.

[0041] In a fifth aspect, an embodiment of the present application provides a photovoltaic system, comprising an inverter, at least one photovoltaic string connected to the inverter, and a master control device connected to the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct-current power sources connected to the power converters correspondingly, and the master control device performs the steps of the method according to the first aspect.

[0042] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description only constitute the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained on the basis of the disclosed drawings without any creative effort.

[0044] FIG. 1 is a structural schematic diagram of a photovoltaic system in a first embodiment provided by the present application.

[0045] FIG. 2 is a structural schematic diagram of a photovoltaic system in a second embodiment provided by the present application.

[0046] FIG. 3 is a flow schematic diagram of a control method of photovoltaic power generation in some embodiments provided by the present application.

[0047] FIG. 4 is a schematic diagram of an adjustment method of an output voltage characteristic value in some embodiments provided by the present application.

[0048] FIG. 5 is a schematic diagram of an adjustment method of an output voltage characteristic value in some other embodiments provided by the present application.

[0049] FIG. 6 is a structural schematic diagram of a master control device in some embodiments provided by the present application.

[0050] FIG. 7 is a structural schematic diagram of an inverter in some embodiments provided by the present application. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be described and explained in the following with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and should not be used to limit the present application. Based on the embodiments provided by the present application, all other embodiments obtained by those skilled in the art without any creative effort shall fall within the scope of the present application. In addition, it should be understood that although the effort made in this development process can be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, some design, manufacture or production changes based on the technical content disclosed in the present application are only routine technical means, and should not be understood as the content disclosed in the present application is insufficient.

[0052] Reference within this application to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X employs A or B" means that X employs A or B or both. The term "a" or "an" is defined as one or more unless explicitly indicated to the contrary or the

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting. Except to the extent necessary or inherent in the processes themselves, capital terms such as "comprise", "comprises", "comprising", "include", "includes", "including", "contain", "contains", "containing", "have", "has", "having", "may", "might", "must", "need", "or", "shall", "shalls", "should", "shouldn't", "will", and "would" are not intended to be limiting. The term "connected" is not intended to be limited to direct connection unless otherwise indicated. The term "multiple" means two or more. The term "and / or" means that the associated objects can exist separately or in combination. The terms "first", "second", "third", etc. are used to distinguish similar objects, not to indicate a specific order.

[0054] FIG. 1 is a schematic diagram of a photovoltaic system according to a first embodiment of the application. As shown in FIG. 1, the photovoltaic system includes at least one photovoltaic string 100 and an inverter 200 connected to the photovoltaic string 100, the photovoltaic string 100 including a plurality of power converters 102 connected in series and photovoltaic DC power sources 101 connected to the power converters 102 correspondingly.

[0055] The photovoltaic DC power sources 101 are connected to the input terminals of the power converters 102 for providing DC power. The photovoltaic DC power sources 101 can be any one of a single photovoltaic module, a single photovoltaic cell sub-string, a plurality of photovoltaic modules connected in series and / or in parallel, and a plurality of photovoltaic cell sub-strings connected in series and / or in parallel.

[0056] The power converter 102 is used to realize direct current conversion, and outputs of a plurality of power converters 102 are connected in series to provide direct current output by the photovoltaic direct current power supply 101 to the inverter 200. The power converter 102 can adjust the working point of the photovoltaic direct current power supply 101 to make the photovoltaic direct current power supply 101 work at the maximum power point, for example, by using a buck, boost, buck-boost circuit or the like.

[0057] The inverter 200 is used to invert the direct current provided by the photovoltaic string 100 into alternating current and provide the alternating current to the power grid or load.

[0058] In some embodiments, the inverter 200 can communicate with each power converter 102, for example, by using a PLC (Power Line Communication), wireless or the like to communicate, can provide a control signal to each power converter 102 to control the working state of each power converter 102, and can quickly shut down the power output of each power converter when needed.

[0059] FIG. 2 is a structural schematic diagram of a photovoltaic system in a second embodiment provided by the present application. As shown in FIG. 2, the photovoltaic system includes at least one photovoltaic string 100, an inverter 200 connected with the photovoltaic string 100, and a master control device 300 connected with the inverter 200, and the photovoltaic string 100 includes a plurality of power converters 102 connected in series and photovoltaic direct current power supplies 101 connected with the power converters 102 correspondingly.

[0060] In some embodiments, the master control device 300 includes an MCU (Micro Controller Unit) and a communication module or the like. The master control device 300 is in communication connection with the inverter 200, communicates with the inverter 200 by using the communication module, for example, by using a PLC, wireless or the like to communicate, and the communication module is realized by using a communication chip or the like.

[0061] In some embodiments, the master control device 300 is in communication connection with each power converter 102, and the master control device 300 can communicate with each power converter 102, for example, by using a PLC, wireless or the like to communicate. The master control device 300 can provide a control signal to each power converter 102 to control the working state of each power converter 102, and can quickly shut down the power output of each power converter when needed, and the master control device 300 can be a transmitter for example.

[0062] In at least some embodiments, the power converter 102 is provided with a switchable MPPT (Maximum Power Point Track) control loop and an output voltage control loop. When the power converter 102 operates in an MPPT state, the MPPT control loop of the power converter 102 functions to control the corresponding connected photovoltaic DC power supply 101 to operate at a maximum power point, thereby achieving maximum utilization of photovoltaic DC power supply energy. At this time, the actual output voltage of the power converter 102 is less than an output voltage characteristic value of the power converter 102, which can be an upper limit value of the output voltage of the power converter 102. When the power converter 102 operates in a voltage limiting state, the output voltage control loop of the power converter 102 functions to control the output voltage of the power converter 102 to be equal to the output voltage characteristic value. At this time, the output power of the photovoltaic DC power supply is in a limited state, resulting in energy loss.

[0063] For system operation safety, the sum of the output voltages of the power converters needs to be less than the upper limit value of the DC input voltage of the inverter (the maximum input voltage allowed for normal operation of the inverter). The sum of the output voltage characteristic values of the power converters can be equal to or less than the upper limit value of the DC input voltage of the inverter. The DC input voltage is generally controlled by the inverter and stabilized at a set value (which is less than the upper limit value of the DC input voltage of the inverter). During system operation, the power converters operate in the MPPT state. When the photovoltaic DC power supply is abnormal (such as being shaded or malfunctioning) or a power converter is tripped due to a fault, the output voltage of part of the power converters rises. When it rises to the corresponding output voltage characteristic value, the power converter operates in the voltage limiting state, resulting in loss of power generation. At this time, the output voltage characteristic value of the power converter in the voltage limiting state needs to be adjusted so that it switches to the MPPT state.

[0064] The present application proposes a photovoltaic power generation control method, which can be applied to the inverter in the first embodiment or the master control device in the second embodiment to control adjustment of the output voltage characteristic value and operating state of the corresponding power converter. Taking the case where the method is applied to the master control device as an example, the method includes: sending a first communication signal; the first communication signal includes an adjustment instruction and an allowed operation instruction, the adjustment instruction being used to control the power converter to adjust its output voltage characteristic value, and the allowed operation instruction being used to control the operating state of the power converter.

[0065] In some embodiments, the master control device can broadcast the first communication signal to the photovoltaic string in which the power converter in the voltage limiting state is located through a communication mode such as PLC or wireless communication.

[0066] In some embodiments, the adjustment instruction is used to control all power converters in the photovoltaic string to adjust their output voltage characteristic values.

[0067] All power converters in the photovoltaic string respond to the first communication signal after receiving the first communication signal, and adjust the output voltage characteristic value according to the adjustment instruction included in the first communication signal, so that the output voltage characteristic value can be adjusted in time, and the power generation of the photovoltaic system will not be affected by the output voltage characteristic value of the power converter.

[0068] Based on the above method, by sending the first communication signal including the adjustment instruction and the allowed operation instruction to the power converter, the power converter responds to the received first communication signal, and adjusts the output voltage characteristic value according to the adjustment instruction included in the first communication signal, so that the output voltage characteristic value can be adjusted in time, and the power generation of the photovoltaic system will not be affected by the output voltage characteristic value of the power converter. Still, the maximum power can be generated under the current situation, which is beneficial to improve the system power generation efficiency. At the same time, the power converter controls its working state according to the allowed operation instruction included in the first communication signal.

[0069] Further, the adjustment instruction and the allowed operation instruction are combined in the first communication signal, which improves the communication efficiency and reduces the channel occupancy rate compared with sending them separately.

[0070] Before sending the first communication signal, the master control device periodically sends a second communication signal including the allowed operation instruction and not including the adjustment instruction to the power converter, to control the working state of each power converter.

[0071] Specifically, the power converter 102 monitors the second communication signal from the master control device 300 in real time, and when receiving the allowed operation instruction in the second communication signal, the power converter 102 works normally, and when not receiving the allowed operation instruction within a first preset time, the output of the power converter 102 is in a limited state.

[0072] It can be understood that the output of the power converter 102 in the limited state means that the power converter 102 closes its power output or the output voltage of the power converter 102 is not higher than a voltage threshold, for example, the upper limit value of the standby voltage of the power converter. Specifically, for example, when the output of the power converter 102 is in the limited state, the output voltage is 1V, and the output current is less than 10mA.

[0073] In some embodiments, when there is a power converter in the voltage limiting state, the master control device stops sending the second communication signal and starts sending the first communication signal. When there is no power converter in the voltage limiting state, the master control device still continues to send the second communication signal.

[0074] The power converter can timely adjust the output voltage characteristic value, so that the power generation of the photovoltaic system will not be affected by the output voltage characteristic value of the power converter, and the photovoltaic system can still generate maximum power under the current condition. Meanwhile, the master control device sends the adjustment instruction when the power converter is in the voltage limiting state, further reducing the occupation of the communication channel and the data amount on the communication link.

[0075] Since the first communication signal includes the operation permission instruction, the master control device can no longer send the second communication signal during the period (during which the first communication signal is sent).

[0076] In at least some of the above embodiments, the time interval between the last time the second communication signal is sent before the first communication signal is sent and the time when the second communication signal is sent again is greater than the first preset time.

[0077] In at least some of the above embodiments, within the first preset time since the second communication signal is stopped being sent, the first communication signal is sent at least once, the time interval between the first time the first communication signal is sent and the time when the second communication signal is started to be sent again is less than the first preset time, and the time interval between the last time the first communication signal is sent and the last time the second communication signal is sent before the first communication signal is sent is less than the first preset time.

[0078] The limitation of the sending time of the first communication signal and the second communication signal ensures that when the power converter does not receive the operation permission instruction, it also does not receive the adjustment instruction, so that whether the power converter does not receive the first communication signal can be determined according to the working state of the power converter.

[0079] In some embodiments, when there is a power converter in the photovoltaic string that does not receive the first communication signal, the first communication signal is sent to the photovoltaic string again; and when there is no power converter in the photovoltaic string that does not receive the first communication signal, the second communication signal is started to be sent to the photovoltaic string again.

[0080] When there is a power converter that does not receive the first communication signal, the first communication signal carrying the adjustment instruction and the operation permission instruction is sent again to avoid the overvoltage problem that may be caused by some power converters that do not receive the adjustment instruction.

[0081] In some embodiments, the inverter can be controlled to determine whether there is a power converter in the photovoltaic string that does not receive the first communication signal according to input electrical parameters of the inverter.

[0082] The input electrical parameters of the inverter include input voltage, input current, etc.

[0083] When the power converter does not receive the permission-to-run instruction again within the first preset time since the last time it received the permission-to-run instruction, it will power down, stop power output, and cause the input voltage or input current of the inverter to drop. If the power converter does not receive the permission-to-run instruction in the first communication signal, it necessarily means that it also does not receive the adjustment instruction carried in the first communication signal. Therefore, when it is detected that the DC input voltage and / or DC input current of the inverter abnormally drops, it is determined that there is a power converter in the photovoltaic string that does not receive the first communication signal.

[0084] In at least some of the above embodiments, the master control device sends the adjustment instruction together with the permission-to-run instruction in the same signal, and can determine whether there is a power converter that does not receive the adjustment instruction according to the input parameters of the inverter. If there is, it will send the adjustment instruction again, so as to further prevent the DC input overvoltage problem and improve the reliability of the system.

[0085] In some embodiments, the inverter applies a disturbance to the DC input of the inverter at a certain preset time interval to determine whether there is a power converter in the photovoltaic string connected to the inverter that is in a voltage limiting state.

[0086] The method for determining whether there is a power converter in the photovoltaic string that is in a voltage limiting state is described in detail below.

[0087] The inverter applies a disturbance to the DC input voltage, and determines whether there is a power converter in a voltage limiting state according to the change in the DC input power of the inverter before and after the disturbance.

[0088] Specifically, in some embodiments, the inverter can apply a disturbance in the direction of increasing the DC input voltage. If the DC input power of the inverter after the disturbance is less than the DC input power before the disturbance, it is considered that there is a power converter in the photovoltaic string that is in a voltage limiting state. Otherwise, it is considered that there is no power converter in the photovoltaic string that is in a voltage limiting state.

[0089] In some embodiments, the inverter can apply a disturbance in the direction of decreasing the DC input voltage. If the DC input power of the inverter after the disturbance is greater than the DC input power before the disturbance, it is considered that there is a power converter in the photovoltaic string that is in a voltage limiting state. Otherwise, it is considered that there is no power converter in the photovoltaic string that is in a voltage limiting state.

[0090] In some embodiments, the inverter can apply a perturbation in the direction of increasing and decreasing the DC input voltage respectively, if the DC input power of the inverter after the perturbation is smaller than the DC input power before the perturbation when the perturbation is applied in the direction of increasing the DC input voltage, and the DC input power of the inverter after the perturbation is larger than the DC input power before the perturbation when the perturbation is applied in the direction of decreasing the DC input voltage, it is considered that there is a power converter in the voltage limiting state in the photovoltaic string; otherwise, it is considered that there is no power converter in the voltage limiting state in the photovoltaic string. By applying the perturbation in the two directions of voltage increasing and decreasing respectively, the accuracy of the judgment can be improved.

[0091] In some embodiments, the adjustment coefficient is carried in the first communication signal, and the power converter can adjust the output voltage characteristic value according to the adjustment coefficient in the first communication signal, for example, the adjusted output voltage characteristic value is the product of the current output voltage of the power converter and the adjustment coefficient.

[0092] In some other embodiments, the adjustment coefficient is not included in the first communication signal, and the power converter adjusts the output voltage characteristic value according to the adjustment coefficient preset by itself, for example, the adjusted output voltage characteristic value is the product of the current output voltage of the power converter and the adjustment coefficient.

[0093] In some embodiments, the adjustment coefficient in the first communication signal is equal to the adjustment coefficient preset by itself.

[0094] In general, the adjustment coefficient in the first communication signal and the adjustment coefficient preset by the power converter itself are both greater than 1. When the inverter needs to lower the upper limit value of the DC input voltage, the adjustment coefficient may be less than 1.

[0095] In some embodiments, the adjustment coefficient is, for example, the ratio of the upper limit value of the DC input voltage of the inverter to the current DC input voltage.

[0096] The adjustment method of the output voltage characteristic value will be described in detail below with reference to FIGS. 4-5.

[0097] In some embodiments, each power converter is provided with an output voltage characteristic value, and the output voltage characteristic value is taken as the upper limit value of the output voltage of the power converter. The PV curve of the output power P and the output voltage Vo of the power converter is shown in FIG. 4, between points a and b (constant power interval), the power converter works in the MPPT state, and the maximum output power is P mpp ; between points b and c (voltage limiting interval), the power converter works in the voltage limiting state, and the output voltage characteristic value is V lim0 . In this interval, the output voltage of the power converter is limited to the output voltage characteristic value V lim0When adjusting the output voltage characteristic value, the output voltage characteristic value can be adjusted from V lim0 to V lim0 , for example. The output voltage characteristic value V lim0 is the product of the current output voltage of the power converter and the adjustment coefficient, and the adjusted PV curve is shown as curve S1 in the figure, for example.

[0098] In some other embodiments, each power converter is provided with multiple output voltage characteristic values. The PV curve of the output power P and the output voltage Vo of the power converter is shown in FIG. 5. Between points d and e (the constant power interval), the power converter operates in the MPPT state, and the maximum output power is P mpp ; between points e and f (the voltage limiting interval), the power converter operates in the voltage limiting state, and the output power of the power converter at point f is 0. The power converter includes a minimum output voltage characteristic value V lim1 corresponding to point e, a maximum output voltage characteristic value V lim2 corresponding to point f, and any number of output voltage characteristic values between the minimum output voltage characteristic value V lim1 and the maximum output voltage characteristic value V lim2 , wherein the maximum output voltage characteristic value V lim2 is the upper limit of the output voltage of the power converter.

[0099] When adjusting the output voltage characteristic value, the adjustment instruction controls the power converter to adjust at least part of the output voltage characteristic value according to the adjustment coefficient.

[0100] In some embodiments, the multiple output voltage characteristic values of the power converter are adjusted by the same ratio. The adjusted output voltage characteristic values are shown as curves S2 and S2’ in FIG. 5, for example.

[0101] Specifically, the adjusted maximum output voltage characteristic value V lim2 is the product of the current output voltage of the power converter and the adjustment coefficient, and the same ratio adjustment of the other output voltage characteristic values can not change the droop characteristic of the PV curve of the power converter, and the power reduction speed remains the same before and after adjustment.

[0102] In some embodiments, the multiple output voltage characteristic values of the power converter can be adjusted by different ratios.

[0103] In some embodiments, if the output voltage characteristic value calculated according to a certain output voltage characteristic value and the adjustment coefficient is greater than the maximum output voltage characteristic value V lim2 , the output voltage characteristic value is adjusted to the maximum output voltage characteristic value V lim2For example, as shown by curve S3 in FIG. 5, so as to ensure that the DC input voltage of the inverter does not exceed the upper limit of the DC input voltage.

[0104] In some embodiments, the minimum output voltage characteristic value V lim2 is kept unchanged, and the maximum output voltage characteristic value V lim1 is adjusted according to the adjustment coefficient, and other output voltage characteristic values are determined according to the minimum output voltage characteristic value V lim1 , the maximum output voltage characteristic value V lim2 , the maximum output power P mpp , and the slope of the PV curve determined by the three.

[0105] In some embodiments, the minimum output voltage characteristic value V lim1 may also be controlled, the maximum output voltage characteristic value V lim2 is adjusted according to the adjustment coefficient, and the adjusted maximum output voltage characteristic value V lim2 may be the product of the current output voltage of the power converter and the adjustment coefficient, and other output voltage characteristic values are determined according to the minimum output voltage characteristic value V lim1 , the adjusted maximum output voltage characteristic value V lim2 , the maximum output power P mpp , and the slope of the PV curve determined by the three.

[0106] The adjustment mode of the at least one output voltage characteristic value described above adjusts the change speed of the DC input power of the inverter through the slope of the PV curve determined again, so as to adapt to different application scenarios and improve the application range, under the premise that the DC input voltage of the inverter does not exceed the upper limit.

[0107] In some embodiments, an upper limit value of the output voltage characteristic value of each power converter can be set, such as the output voltage upper limit value Voh in FIG. 4 and FIG. 5. When the output voltage characteristic value calculated by the power converter according to the current output voltage and the adjustment coefficient is greater than the output voltage upper limit value Voh, the output voltage characteristic value is set to the output voltage upper limit value Voh, for example, as shown by curve S5 in FIG. 4.

[0108] The output voltage upper limit value Voh may be, for example, the rated output voltage of the power converter.

[0109] In some other embodiments, the master control device does not consider whether there is a power converter in the voltage limiting state, and the master control device stops sending the second communication signal and starts sending the first communication signal every second preset time.

[0110] In some embodiments, the first preset time is less than the second preset time. In some embodiments, the first preset time is less than the second preset time.

[0111] In some embodiments, the time interval between the last time the second communication signal is sent before the first communication signal is sent and the time the second communication signal is sent again is greater than the first preset time.

[0112] In some embodiments, within the first preset time since the second communication signal is stopped being sent, the first communication signal is sent at least once, the time interval between the first time the first communication signal is sent and the time the second communication signal is started to be sent again is less than the first preset time, and the time interval between the last time the first communication signal is sent and the last time the second communication signal is sent before the first communication signal is sent is less than the first preset time.

[0113] According to embodiments of the present application, a master control device is also provided to implement the above control method. As shown in FIG. 2, the master control device is applied to a photovoltaic system. As shown in FIG. 6, the master control device 300 includes:

[0114] a second signal sending module 302, configured to send a first communication signal; the first communication signal includes an adjustment instruction and an enable operation instruction, the adjustment instruction is used to control a power converter to adjust an output voltage characteristic value thereof, and the enable operation instruction is used to control a working state of the power converter.

[0115] When the power converter does not receive the enable operation instruction within a first preset time, the output of the power converter is in a limited state.

[0116] In some embodiments, the second signal sending module, before sending the first communication signal, sends a second communication signal including the enable operation instruction and not including the adjustment instruction.

[0117] The second signal sending module stops sending the second communication signal and starts to send the first communication signal every second preset time or when there is a power converter in a voltage-limited state.

[0118] In some embodiments, the time interval between the last time the second communication signal is sent before the first communication signal is sent and the time the second communication signal is sent again is greater than the first preset time.

[0119] In some embodiments, within the first preset time since the second communication signal is stopped being sent, the first communication signal is sent at least once, the time interval between the first time the first communication signal is sent and the time the second communication signal is started to be sent again is less than the first preset time, and the time interval between the last time the first communication signal is sent and the last time the second communication signal is sent before the first communication signal is sent is less than the first preset time.

[0120] In some embodiments, when there is a power converter in the photovoltaic string that has not received the first communication signal, the second signal sending module sends the first communication signal to the photovoltaic string again.

[0121] When there is no power converter in the photovoltaic string that has not received the first communication signal, the second signal sending module resumes sending the second communication signal to the photovoltaic string.

[0122] In some embodiments, further comprising:

[0123] A third signal sending module for sending an operation state query instruction, the operation state query instruction being used to query a judgment result of whether there is a power converter in the photovoltaic string that has not received the first communication signal.

[0124] In some embodiments, further comprising:

[0125] A fourth signal sending module for sending a state judgment instruction, the state judgment instruction being used to control the inverter to judge whether there is a power converter in the photovoltaic string connected to the inverter that is in a voltage limiting state.

[0126] Since the processing and functions realized by the master control device of the above-mentioned embodiments correspond to the embodiments, principles and examples of the foregoing control method, the description of the present embodiment does not elaborate on the details, which can be referred to the relevant description in the foregoing embodiments, and will not be repeated here.

[0127] According to the embodiments of the present application, an inverter for realizing the above-mentioned control method is also provided, which is applied to the photovoltaic system as shown in FIG. 1, as shown in FIG. 7, the inverter 200 comprises:

[0128] A first signal sending module 202 for sending a first communication signal; the first communication signal comprises an adjustment instruction and an allowed operation instruction, the adjustment instruction being used to control a power converter to adjust its output voltage characteristic value, and the allowed operation instruction being used to control the working state of the power converter.

[0129] When the power converter has not received the allowed operation instruction within a first preset time, the output of the power converter is in a limited state.

[0130] The above-mentioned various modules can be realized by a processor and the like hardware. Since the processing and functions realized by the inverter of the above-mentioned embodiments correspond to the embodiments, principles and examples of the foregoing control method, the description of the present embodiment does not elaborate on the details, which can be referred to the relevant description in the foregoing embodiments, and will not be repeated here.

[0131] The application provides a photovoltaic system, as shown in Fig. 1, comprising an inverter 200 and at least one photovoltaic string 100 connected with the inverter 200, the photovoltaic string 100 comprising a plurality of power converters 102 connected in series and photovoltaic direct-current power sources 101 connected with the power converters 102 correspondingly, and the inverter 200 performs the steps of the control method of the photovoltaic power generation.

[0132] Since the processing and functions realized by the photovoltaic system of the above-mentioned embodiment correspond to the embodiments, principles and examples of the aforementioned control method, the description of the present embodiment does not describe the related descriptions in the foregoing embodiments, which will not be repeated here.

[0133] The application provides a photovoltaic system, as shown in Fig. 2, comprising an inverter 200, at least one photovoltaic string 100 connected with the inverter 200, and a master control device 300 connected with the inverter 200, the photovoltaic string 100 comprising a plurality of power converters 102 connected in series and photovoltaic direct-current power sources 101 connected with the power converters 102 correspondingly, and the master control device 300 performs the steps of the control method of the photovoltaic power generation.

[0134] Since the processing and functions realized by the photovoltaic system of the above-mentioned embodiment correspond to the embodiments, principles and examples of the aforementioned control method, the description of the present embodiment does not describe the related descriptions in the foregoing embodiments, which will not be repeated here.

[0135] The technical features of the above-mentioned embodiments can be combined in any way, and in order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered that it is within the scope of the present application.

[0136] The above-mentioned embodiments only express several implementation manners of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are within the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A control method of photovoltaic power generation, characterized by, The method comprises: sending a first communication signal; the first communication signal comprises adjustment instructions and operation permission instructions, the adjustment instructions are used for controlling the power converter to adjust the output voltage characteristic value, and the operation permission instructions are used for controlling the working state of the power converter; a plurality of power converters are connected in series to form a photovoltaic string and are connected with an inverter; when the power converter does not receive the operation permission instructions within a first preset time, the output of the power converter is in a limited state.

2. The method of claim 1, wherein, sending a second communication signal comprising the operation permission instructions and not comprising the adjustment instructions before sending the first communication signal; every second preset time or when there is a power converter in a voltage limiting state, stopping sending the second communication signal and starting to send the first communication signal.

3. The method of claim 2, wherein, The first preset time is less than the second preset time.

4. The method of claim 2, wherein, The time interval from the last time of sending the second communication signal before sending the first communication signal to the time of sending the second communication signal again is greater than the first preset time.

5. The method of claim 4, wherein, Within the first preset time from stopping sending the second communication signal, the first communication signal is sent at least once, the time interval from the first time of sending the first communication signal to the time of starting to send the second communication signal again is less than the first preset time, and the time interval from the last time of sending the first communication signal to the last time of sending the second communication signal before sending the first communication signal is less than the first preset time.

6. The method of claim 1 or 2, wherein, The method further comprises: when there is a power converter in the photovoltaic string that does not receive the first communication signal, the first communication signal is sent to the photovoltaic string again; when there is no power converter in the photovoltaic string that does not receive the first communication signal, the second communication signal is started to be sent to the photovoltaic string again.

7. The method of claim 6, wherein, controlling the inverter to determine whether there is a power converter in the photovoltaic string that does not receive the first communication signal according to the input electrical parameters of the inverter.

8. The method of claim 7, wherein, when it is detected that the direct-current input voltage and / or the direct-current input current of the inverter abnormally decreases, it is determined that there is a power converter in the photovoltaic string that does not receive the first communication signal.

9. The method of claim 1, wherein, the first communication signal carries an adjustment coefficient, and the adjustment instructions control the power converter to adjust the output voltage characteristic value according to the adjustment coefficient; or, the adjustment instructions control the power converter to adjust the output voltage characteristic value according to the preset adjustment coefficient of the power converter.

10. The method of claim 2, wherein, controlling the inverter to apply a disturbance to the direct-current input thereof and determining whether there is a power converter in the photovoltaic string connected with the inverter that is in a voltage limiting state.

11. The method of claim 10, wherein, controlling the inverter to apply a disturbance to the direct-current input voltage of the inverter in the direction of increasing and / or decreasing, and determining whether there is a power converter in a voltage limiting state according to the change of the direct-current input power of the inverter before and after the disturbance.

12. An inverter applied to a photovoltaic system, the photovoltaic system further comprising at least one photovoltaic string connected to the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct current power sources connected to the power converters correspondingly, characterized in that, The inverter comprises: a first signal sending module, configured to send a first communication signal; the first communication signal comprises adjustment instructions and operation permission instructions, the adjustment instructions are used for controlling the power converter to adjust the output voltage characteristic value, and the operation permission instructions are used for controlling the working state of the power converter; When the power converter does not receive the operation permission instruction within the first preset time, the output of the power converter is in a limited state.

13. A master control device applied to a photovoltaic system, the photovoltaic system further comprising at least one photovoltaic string and an inverter connected with the photovoltaic string, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct-current power sources connected with the power converters in correspondence, characterized in that, The master device comprises: The second signal sending module is configured to send a first communication signal, wherein the first communication signal comprises an adjustment instruction and an operation permission instruction, the adjustment instruction is used to control the power converter to adjust the output voltage characteristic value, and the operation permission instruction is used to control the working state of the power converter. When the power converter does not receive the operation permission instruction within the first preset time, the output of the power converter is in a limited state.

14. The master device of claim 13, wherein, The second signal sending module sends a second communication signal comprising the operation permission instruction and not comprising the adjustment instruction before sending the first communication signal. The second signal sending module stops sending the second communication signal and starts sending the first communication signal every second preset time or when there is a power converter in the voltage limiting state.

15. The master device of claim 14, wherein, The time interval between the last time when the second signal sending module sends the second communication signal and the time when the second communication signal is sent again is greater than the first preset time before the second signal sending module sends the first communication signal.

16. The master device of claim 15, wherein, The second signal sending module sends the first communication signal at least once within the first preset time since the second signal sending module stops sending the second communication signal, the time interval between the first time when the first communication signal is sent and the time when the second communication signal is started to be sent again is less than the first preset time, and the time interval between the last time when the first communication signal is sent and the time when the second communication signal is sent last time before the first communication signal is sent is less than the first preset time.

17. The master device of claim 13 or 14, wherein, When there is a power converter in the photovoltaic string that does not receive the first communication signal, the second signal sending module sends the first communication signal to the photovoltaic string again. When there is no power converter in the photovoltaic string that does not receive the first communication signal, the second signal sending module starts to send the second communication signal to the photovoltaic string again.

18. The master device of claim 17, wherein, Further comprising: The third signal sending module is configured to send an operation state query instruction, and the operation state query instruction is used to query the judgment result of whether there is a power converter in the photovoltaic string that does not receive the first communication signal.

19. The master device of claim 14, wherein, Further comprising: The fourth signal sending module is configured to send a state judgment instruction, and the state judgment instruction is used to control the inverter to judge whether there is a power converter in the photovoltaic string connected with the inverter that is in the voltage limiting state.

20. A photovoltaic system characterized by, The inverter and at least one photovoltaic string connected with the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct-current power sources connected with the power converters correspondingly, the inverter performing the steps of the method according to any one of claims 1-11.

21. A photovoltaic system characterized by, The inverter, at least one photovoltaic string connected with the inverter, and a master device connected with the inverter, the photovoltaic string comprising a plurality of power converters connected in series and photovoltaic direct-current power sources connected with the power converters correspondingly, the master device performing the steps of the method according to any one of claims 1-11.

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