Determining method and apparatus for shutdown device abnormality in string, and inverter

Abstract

A determining method and apparatus for a shutdown device abnormality in a string, and an inverter. The method comprises: acquiring a blocking voltage of an inverter; acquiring an actual voltage array and a current array of a target solar panel string in the process of decreasing the voltage at an MPPT direct current input end corresponding to the target solar panel string from the blocking voltage to a preset voltage; determining at least one current value, and determining a first open-circuit voltage of the target solar panel string by means of a voltage value corresponding to the at least one current value; and on the basis of the first open-circuit voltage, determining whether the target solar panel string has a shutdown device abnormality. In this way, by means of minimal calculation, the first open-circuit voltage can be acquired, to efficiently analyze whether the solar panel string has the shutdown device abnormality.

Description

A method and device for determining whether a string has a circuit breaker abnormality, an inverter

[0001] This application claims priority to Chinese patent application number CN2023111607229 filed with the State Intellectual Property Office of the People's Republic of China on September 8, 2023, entitled "A method and device for determining the presence of a switch-off abnormality in a string, and an inverter", the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of photovoltaic technology, and in particular to a method and device for determining whether a string circuit breaker is abnormal, and an inverter. Background Art

[0003] When the inverter in a photovoltaic system is operating, the operating voltage may be affected by factors such as cloud obstruction and dirty solar panel strings. Therefore, it is difficult to determine whether the photovoltaic system string-level shutdown device (hereinafter referred to as the shutdown device) is damaged by changes in the string operating voltage.

[0004] Currently, the open-circuit voltage of a string can effectively avoid misjudging low operating voltages due to differences in illumination or contamination of the solar panel strings. However, string or centralized inverters typically have a maximum power point tracking (MPPT) circuit connected to two or more strings. Due to the potential for circulating currents and the proportional relationship between the open-circuit voltage and the MPPT voltage of a single standard string, the maximum power operating point of the string may be multi-peaked due to inconsistent string attenuation characteristics and uneven illumination, making it difficult to deduce the string open-circuit voltage based on the string maximum power point voltage. Inverters typically cannot directly sample the string open-circuit voltage, making it impossible to effectively locate the failure location of an abnormal circuit breaker on a specific string of the inverter.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present application provide a method and apparatus for determining whether a string has a circuit breaker anomaly, and an inverter, aiming to locate the failure location on a specific string of the inverter to facilitate operation and maintenance.

[0007] In a first aspect, an embodiment of the present application provides a method for determining whether a string has a circuit breaker abnormality, the method comprising: obtaining a blocking voltage of an inverter, the blocking voltage being the voltage at the DC input terminal of the inverter when a first circuit in the inverter is closed, the first circuit comprising an inverter circuit; in a step-down process of decreasing the voltage at the MPPT DC input terminal corresponding to a target solar panel string from the blocking voltage to a preset voltage, obtaining an actual voltage array and a current array of the target solar panel string, elements at the same position in the actual voltage array and the current array being obtained corresponding to the same decrement, and the target solar panel string being one of the solar panel strings to be tested; determining at least one current value based on the actual voltage array and the current array, and determining a first open-circuit voltage of the target solar panel string through a voltage value corresponding to the at least one current value; and determining whether the target solar panel string has a circuit breaker abnormality based on the first open-circuit voltage.

[0008] Optionally, in the voltage reduction process of reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, obtaining the actual voltage array and current array of the target solar panel string includes: reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string by a first parameter value; obtaining the actual voltage value of the target solar panel string, and storing the actual voltage value in the actual voltage array of the target solar panel string; obtaining the current value of the target solar panel string, and storing the current value in the current array of the target solar panel string; if the voltage of the MPPT DC input terminal does not decrease to the preset voltage, continuing to execute the step of reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string by the first parameter value and subsequent steps; if the voltage of the MPPT DC input terminal decreases to the preset voltage, determining the current array and actual voltage array of the target solar panel string.

[0009] Optionally, determining at least one current value based on the actual voltage array and the current array, and determining the first open-circuit voltage of the target solar panel string by the voltage value corresponding to the at least one current value, includes: determining a first first current value greater than or equal to zero and a first actual voltage value corresponding to the first current value based on the actual voltage array and the current array; determining a first second current value that meets a preset condition and a second actual voltage value corresponding to the second current value; the preset condition is that a second product of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and an actual voltage value corresponding to the third current value, and the second product is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the position of the second current value in the current array is after the first current value; using a ratio of a first parameter to a second parameter as the first open-circuit voltage, the first parameter being a difference between a product of the first current value and the second actual voltage value and a product of the second current value and the first actual voltage value, and the second parameter being a difference between the first current value and the second current value.

[0010] Optionally, the method determines at least one current value based on the actual voltage array and the current array, and determines the first open-circuit voltage of the target solar panel string by the voltage value corresponding to the at least one current value, including: in the current array, if it is determined that the n-1th current value is less than zero and the nth current value is greater than zero or equal to zero, then the nth actual voltage value in the actual voltage array is used as the open-circuit voltage; if all current values ​​in the current array are greater than zero, then the first first current value in the current array is determined, and if the first current value is less than or equal to the current threshold, then the first actual voltage value in the actual voltage array corresponding to the first current value is used as the first open-circuit voltage; if the first current value is greater than the current threshold, then the first second current value that meets the preset conditions and the a second actual voltage value corresponding to the second current value, the preset condition being that a second product value of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and the actual voltage value corresponding to the third current value, and the second product value is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the position of the second current value in the current array is after the first current value; a ratio of the first parameter to the second parameter is used as a first open-circuit voltage, the first parameter being a difference between a product of the first current value and the second actual voltage value and a product of the second current value and the first actual voltage value corresponding to the first current value, and the second parameter being a difference between the first current value and the second current value.

[0011] Optionally, the determining whether there is a circuit breaker abnormality in the target solar panel string based on the first open-circuit voltage includes: if the first open-circuit voltage meets a preset abnormal condition, increasing the abnormal number of the target solar panel string by one, and obtaining the currently accumulated abnormal number of the target solar panel string; if the abnormal number exceeds a preset value, there is a circuit breaker abnormality in the target solar panel string, and the preset value is the number required to determine whether there is a circuit breaker abnormality in the target solar panel string; if the abnormal number does not exceed the preset value, continuing to execute the obtaining of the inverter's closing wave voltage and subsequent steps; if the first open-circuit voltage meets the preset abnormal condition, it also includes: if the first open-circuit voltage does not meet the preset abnormal condition, continuing to execute the obtaining of the inverter's closing wave voltage and subsequent steps.

[0012] Optionally, the method further includes: repeating the step of obtaining the inverter's blocking voltage and subsequent steps within each cycle until it is confirmed that the target solar panel string has a circuit breaker abnormality, or the repetition reaches a preset number of repetitions or a preset repetition duration; the preset value is the number of times required to determine that the target solar panel string has a circuit breaker abnormality within the cycle.

[0013] Optionally, the preset abnormal condition is set according to the first open-circuit voltage of the target solar panel string and a historical record value, and the historical record value is a value set based on the historical first open-circuit voltage of the target solar panel string.

[0014] Optionally, the first open-circuit voltage meets a preset abnormal condition, including: if the first open-circuit voltage is less than the historical record value, and a first comparison value between the historical record value and the first open-circuit voltage is greater than a first threshold; the first threshold is set according to the target solar panel string nominal open-circuit voltage.

[0015] Optionally, the historical record value is the maximum first open-circuit voltage value in the historical record, or the historical record value is the average value of multiple first open-circuit voltage values ​​in the historical record within a preset time length, or the historical record value is the average value of multiple first open-circuit voltages ranked from large to small within the preset time length.

[0016] Optionally, the first open circuit voltage does not meet a preset abnormal condition, including: the first open circuit voltage is greater than the historical record value, and the historical record value is updated; or the first open circuit voltage is equal to the historical record value.

[0017] Optionally, there are multiple solar panel strings to be tested that power the MPPT; if the first open-circuit voltage meets a preset abnormal condition, it includes: if the absolute value of the second comparison value of the first open-circuit voltage and the second open-circuit voltage is greater than the historical record value, and the absolute value of the second comparison value and the third comparison value of the historical record value are greater than a second threshold; the second open-circuit voltage is the open-circuit voltage of the solar panel string to be compared, and the solar panel string to be compared is one of the solar panel strings to be tested except the target solar panel string, and the historical record value is set according to the absolute value of the second comparison value of the historical record, and the first open-circuit voltage and the second open-circuit voltage of each second comparison value are determined by data obtained in the same process of reducing the voltage of the MPPT DC input terminal from the closed-wave voltage to the preset voltage, and the second threshold is set according to the nominal open-circuit voltage of the solar panel string.

[0018] Optionally, the historical record value is the maximum value of the absolute values ​​of the second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of multiple second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of a preset number of second comparison values ​​in a preset segment that are sorted from large to small.

[0019] Optionally, the first open-circuit voltage does not meet a preset abnormal condition, including: the absolute value of the second comparison value is less than the historical record value, and the historical record value is updated to the absolute value of the second comparison value; or the absolute value of the second comparison value is equal to the historical record value.

[0020] Optionally, the first circuit further includes a DC boost circuit.

[0021] Optionally, the preset voltage is a starting voltage of the inverter or a preset multiple of the blocking voltage, and the preset multiple is less than 1.

[0022] In a second aspect, the present application also provides a device for determining whether a string has a circuit breaker abnormality, the device comprising: a wave-blocking module, configured to obtain the wave-blocking voltage of the inverter, the wave-blocking voltage being the voltage of the DC input terminal of the inverter when the first circuit in the inverter is closed, the first circuit comprising an inverter circuit; a processing module, configured to obtain the actual voltage array and current array of the target solar panel string during the step-down process of decreasing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from the wave-blocking voltage to the preset voltage, the elements at the same position in the actual voltage array and the current array being obtained corresponding to the same decrement, and the target solar panel string is one of the solar panel strings to be tested; a calculation module, configured to determine at least one current value based on the actual voltage array and the current array, and determine the first open-circuit voltage of the target solar panel string through the voltage value corresponding to the at least one current value; a confirmation module, configured to determine whether the target solar panel string has a circuit breaker abnormality based on the first open-circuit voltage.

[0023] In a third aspect, the present application further provides an inverter that uses the above-mentioned method for determining whether a string has a circuit breaker abnormality to determine whether a target solar panel string has a circuit breaker abnormality.

[0024] In a fourth aspect, the present application also provides a photovoltaic system comprising a solar string and an inverter; the solar panel string is connected to the input end of the inverter, and the output end of the inverter is connected to a power grid or a load; the solar panel string is configured to output direct current to the inverter; the inverter is configured to receive the direct current and output alternating current to the power grid or the load, and uses the above-mentioned method for determining whether a string has a circuit breaker abnormality to determine whether a target solar panel string connected to the inverter has a circuit breaker abnormality.

[0025] Embodiments of the present application provide a method and apparatus for determining whether a solar panel string has a circuit breaker anomaly, and an inverter. By obtaining a closed-circuit voltage, and then, during the step-down process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from the closed-circuit voltage to a preset voltage, obtaining an actual voltage array and a current array of the target solar panel string. Furthermore, based on the actual voltage array and the current array, at least one current value is determined, and the first open-circuit voltage of the target solar panel string is determined using the voltage value corresponding to the at least one current value. Based on the first open-circuit voltage, it is determined whether the target solar panel string has a circuit breaker anomaly. Thus, the present application allows the first open-circuit voltage of the target solar panel string to be determined by simply determining at least one current value from the actual voltage array and the current array and combining it with the corresponding voltage value. This avoids the computational complexity associated with determining the open-circuit voltage using curve fitting, thereby improving computational efficiency. Furthermore, the present application can determine the first open-circuit voltage using a small number of current values, which can be implemented within the inverter's computing unit, eliminating the need for an additional processor for curve fitting and reducing costs. The present application determines whether there is a circuit breaker abnormality in the target solar panel string through the first open-circuit voltage, thereby avoiding the problem that the operating voltage of the solar panel string is affected by factors such as dark clouds and string dirt, and it is difficult to judge whether there is a circuit breaker damage by the change of the operating voltage of the target solar panel string. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the following briefly introduces the drawings required for use in the embodiment or the prior art description. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] FIG1 is a schematic circuit diagram of a photovoltaic system string shutdown device according to an embodiment of the present application;

[0028] FIG2 is a flow chart of a method for determining whether a string circuit breaker is abnormal, provided by an embodiment of the present application;

[0029] FIG3 is a schematic diagram of a process for obtaining open circuit voltage according to an embodiment of the present application;

[0030] FIG4 is a schematic diagram of another process for obtaining open circuit voltage according to an embodiment of the present application;

[0031] FIG5 is a schematic diagram of a flow chart of determining whether a first open-circuit voltage satisfies a preset abnormal condition according to an embodiment of the present application;

[0032] FIG6 is a schematic diagram of another flow chart for determining whether a first open-circuit voltage satisfies a preset abnormal condition according to an embodiment of the present application;

[0033] FIG7 is an application flow chart of a method for determining whether a string circuit breaker is abnormal, provided by an embodiment of the present application;

[0034] FIG8 is a schematic structural diagram of a device for determining whether a string circuit breaker is abnormal, provided by an embodiment of the present application;

[0035] FIG9 is a schematic diagram of a connection structure between an inverter and a solar panel provided in an embodiment of the present application;

[0036] FIG10 is a schematic diagram of another connection structure between an inverter and a solar panel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] Figure 1 shows a schematic circuit diagram of a photovoltaic system string-level shutdown device. The photovoltaic system string-level shutdown device (hereinafter collectively referred to as the shutdown device) includes Q1 / D1 and Q2 / D2, which can be MOSFETs / IGBTs or diodes, and PV1 and PV2, which are solar panels. After long-term operation, the shutdown device may become damaged. Specifically, if Q1 / D1 is short-circuited, it will not be effectively shut down during shutdown, and the string voltage will significantly exceed the safe voltage. The faulty string or MPPT can be directly located based on the string voltage after shutdown. If Q2 / D2 is open-circuited, maintenance is not necessary because the Q2 / D2 circuit is not required during normal operation. If Q1 / D1 is open-circuited or Q2 / D2 is short-circuited, the corresponding string will be bypassed from the entire string, resulting in a low string voltage. During inverter operation, the operating voltage is affected by factors such as cloud obstruction and string contamination, making it difficult to determine whether the circuit breaker is damaged by changes in the string operating voltage. Therefore, if the Q1 / D1 part is open or the Q2 / D2 part is short-circuited, it is difficult to locate the solar panel string with abnormal circuit breakers in the inverter.

[0038] The open-circuit voltage can effectively avoid misjudging low operating voltage caused by differences in sunlight or string contamination. However, string or centralized inverters typically have a maximum power point tracking (MPPT) solar controller circuit connected to two or more strings. Due to the possibility of circulating current, the inverter cannot usually reliably obtain the string open-circuit voltage through direct sampling.

[0039] Conventional methods for obtaining open-circuit voltage usually require an IV scan, fitting the voltage and current data according to the IV curve equation, and then calculating the open-circuit voltage. However, fitting the IV curve by obtaining multiple current values ​​and corresponding multiple voltage values ​​requires a large amount of calculation and is difficult to implement at the inverter end. A processor capable of curve fitting is required, which increases costs.

[0040] Based on the above-mentioned problems, the present application adopts a method and apparatus for determining whether a solar panel string has a circuit breaker anomaly, and an inverter. The method obtains the actual voltage array and current array of the target solar panel string by obtaining the blocking voltage and then performing a voltage reduction process from the blocking voltage to a preset voltage at the MPPT DC input terminal corresponding to the target solar panel string. Furthermore, based on the actual voltage array and current array, at least one current value is determined, and the first open-circuit voltage of the target solar panel string is determined based on the voltage value corresponding to the at least one current value. Based on the first open-circuit voltage, it is determined whether the target solar panel string has a circuit breaker anomaly.

[0041] In this way, the present application can determine the first open-circuit voltage of the target solar panel string from the actual voltage array and current array by simply determining at least one current value and the corresponding voltage value. This greatly reduces the amount of calculation, avoids the use of the actual voltage array and current array, and avoids the multi-point fitting of the IV curve. There is no need to configure a processor for implementing curve fitting, thereby reducing the amount of calculation for determining the first open-circuit voltage and lowering the cost of calculation.

[0042] The first open-circuit voltage of the target solar panel string is used to determine whether the target solar panel has a circuit breaker abnormality, thereby avoiding the problem that the operating voltage of the solar panel string is affected by factors such as dark clouds and string dirt, and it is difficult to judge whether the circuit breaker is damaged by the change of the operating voltage of the target solar panel string.

[0043] Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] FIG2 is a flow chart of a method for determining whether a string circuit breaker is abnormal, according to an embodiment of the present application. Referring to FIG2 , a method for determining whether a string circuit breaker is abnormal includes:

[0045] S201: Obtain a blocking voltage of an inverter. The blocking voltage is a voltage at a DC input terminal of the inverter when a first circuit in the inverter is closed. The first circuit includes an inverter circuit.

[0046] Obtaining the blocking voltage of the inverter means obtaining the voltage at the DC input terminal of the inverter as the blocking voltage after turning off all switching elements (such as MOS tubes / IGBTs) in the first circuit.

[0047] In a possible implementation, the inverter is a string inverter or a centralized inverter, which generally has at least one Maximum Power Point Tracking (MPPT) function corresponding to at least one solar panel string.

[0048] S202. During a voltage reduction process of reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from a closed-wave voltage to a preset voltage, an actual voltage array and a current array of the target solar panel string are obtained, where elements at the same position in the actual voltage array and the current array are obtained corresponding to the same reduction operation. The target solar panel string is one of the solar panel strings to be tested.

[0049] The voltage at the MPPT DC input terminal corresponding to the target solar panel string is decreased from the closing wave voltage in order to obtain the current array and the actual voltage array at the power point to the right of the maximum power point of the MPPT power curve, thereby facilitating the determination of a current value close to or equal to zero for the subsequent determination of the open-circuit voltage.

[0050] In one possible implementation, the voltage at the MPPT DC input terminal can be gradually reduced from the wave-sealing voltage to the preset voltage at a preset voltage value (the interval time of each reduction can be fixed or non-fixed), or the voltage at the MPPT DC input terminal can be linearly or non-linearly reduced from the wave-sealing voltage to the preset voltage over time.

[0051] The number of solar panel strings that power the MPPT can be one or more.

[0052] The elements at the same position in the actual voltage array and the current array are obtained in the same decrement. In another possible implementation, the actual voltage value of the target solar panel string is obtained at each decrement, and the actual voltage array of the target solar panel string is formed in chronological order. The current value of the target solar panel string is obtained at each decrement, and the current array of the target solar panel string is formed in chronological order. During the step-down process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, the number of decrements is equal to the number of current value elements in the current array, and is also equal to the number of actual voltage value elements in the actual voltage array.

[0053] S203 : Determine at least one current value according to the actual voltage array and the current array, and determine a first open-circuit voltage of the target solar panel string according to a voltage value corresponding to the at least one current value.

[0054] Because the operating voltage is affected by factors such as cloud cover and string contamination, it is difficult to determine whether there is a problem with the circuit breaker being damaged by changes in the operating voltage of the solar panel string. Therefore, at least one current value is determined from the current array. The current value can be used to determine the voltage value corresponding to the current approaching zero or equal to zero. This voltage value is the approximate open-circuit voltage, which is not affected by factors such as cloud cover and string contamination, and can be used to determine whether there is an abnormal circuit breaker in the solar panel string.

[0055] Furthermore, by determining a small number of current values ​​from a current array having multiple current values ​​for calculation, the solution of determining the open circuit voltage by curve fitting is avoided, the amount of calculation is greatly reduced, and there is no need to configure a processor for curve fitting, thus saving costs.

[0056] S204: Determine, based on the first open-circuit voltage, that a circuit breaker abnormality exists in the target solar panel string.

[0057] As can be seen from steps S201-S204 above, the present application only needs to determine at least one current value and the corresponding voltage value from the actual voltage array and current array to determine the first open-circuit voltage. This significantly reduces the amount of computation required, avoids the use of the actual voltage array and current array to fit the IV curve at multiple points, and eliminates the need for a processor for performing IV curve fitting. This reduces the amount of computation required to determine the first open-circuit voltage, lowering computational costs. Determining the first open-circuit voltage with less computation avoids the problem of solar panel strings being affected by factors such as cloud cover and string contamination, making it difficult to determine whether the circuit breaker is damaged based on changes in the string operating voltage.

[0058] In a possible implementation, the first circuit of the inverter in step S201 further includes a DC boost circuit.

[0059] In another possible implementation, in the above step S202, the preset voltage can be the starting voltage of the inverter, or it can be a preset multiple of the blocking voltage, where the preset multiple is less than 1. Of course, it can also be a voltage lower than the blocking voltage, for example, set manually.

[0060] In the embodiment of the present application, in step S202 of FIG. 2 , during the step-down process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, the actual voltage array and current array of the target solar panel string are obtained. Possible implementations are described below. It should be noted that the implementations described below are merely exemplary and do not represent all implementations of the embodiment of the present application.

[0061] Step A1: Decrease the voltage at the DC input terminal of the MPPT corresponding to the target solar panel string by a first parameter value.

[0062] The first parameter value is smaller than the difference between the sealing wave voltage and the preset voltage.

[0063] In one possible implementation, the difference between the closed-wave voltage and the preset voltage is K times the first parameter value. Therefore, during the process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, the voltage is decreased K times, each time by the first parameter value. Consequently, the number of elements in the actual voltage array and the number of elements in the current array of the solar panel string are both K.

[0064] Step A2: Acquire the actual voltage value of the target solar panel string, and store the actual voltage value into an actual voltage array of the target solar panel string.

[0065] After each decrease of the first parameter value, the actual voltage value of the target solar panel string is obtained and recorded in an actual voltage array.

[0066] Step A3: Obtain the current value of the target solar panel string, and store the current value in the current array of the target solar panel string.

[0067] After each decrease of the first parameter value, the current value of the target solar panel string is obtained and recorded in the current array.

[0068] The execution order of the above steps A2 and A3 is not limited.

[0069] Step A4: If the voltage at the MPPT's DC input terminal has not decreased to the preset voltage, continue decreasing the voltage at the MPPT's DC input terminal corresponding to the target solar panel string by the first parameter value and subsequent steps; if the voltage at the MPPT's DC input terminal decreases to the preset voltage, determine the current array and actual voltage array of the target solar panel string.

[0070] Exemplarily, starting from the closing wave voltage, steps A1-A4 are executed K times in a loop until the Kth decrease reaches the preset voltage, the actual voltage value and current value corresponding to the Kth decrease are obtained and the corresponding array of values ​​is recorded, and the loop ends.

[0071] Exemplarily, the voltage at the DC input end of the MPPT is controlled starting from the closed-wave voltage, and steps A1-A4 are executed once each time the voltage is decreased, and steps A1-A4 are executed K times in a cycle to obtain the current array (including K current values) and actual voltage array (including K actual voltage values) of the solar panel string.

[0072] In one possible implementation, there are three solar panel strings to be tested that are set to be powered by MPPT. During the voltage reduction process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, while obtaining the actual voltage array and current array of the target solar panel string using steps A1-A4, the actual voltage array and current array corresponding to the other solar panel strings among the three solar panel strings to be tested, excluding the target solar panel string, can also be obtained simultaneously. Specifically, this includes:

[0073] Step A01: Decrease the voltage at the DC input terminal of the MPPT corresponding to the target solar panel string by a first parameter value.

[0074] The difference between the closed-wave voltage and the preset voltage is set to be K times the first parameter value. The number of elements in the actual voltage array and the number of elements in the current array of each solar panel string are both K.

[0075] Step A02: Acquire the actual voltage value of each solar panel string in the solar array to be tested, and store the actual voltage value in an actual voltage array of the corresponding solar panel string.

[0076] Specifically, if there are three solar panel strings to be tested that power the MPPT, three actual voltage arrays (Ua, Ub, and Uc) are set corresponding to the three solar panel strings. After executing step A01 to decrement the first parameter, execute step A02 to obtain the actual voltage value of solar panel string a and record it in the corresponding actual voltage array Ua, obtain the actual voltage value of solar panel string b and record it in the corresponding actual voltage array Ub, and obtain the actual voltage value of solar panel string c and record it in the corresponding actual voltage array Uc.

[0077] Step A03: Obtain the current value of each solar panel string in the solar array to be tested, and store the current value in the current array of the corresponding solar panel string.

[0078] The execution order of steps A02 and A03 is not limited.

[0079] Specifically, if there are three solar panel strings to be tested, three current arrays (Ia, Ib, and Ic) are set corresponding to the three solar panel strings. After executing step A01 to decrement the first parameter, executing step A03 to obtain the actual voltage value of solar panel string a and record it in the corresponding actual voltage array Ia, obtain the actual voltage value of solar panel string b and record it in the corresponding actual voltage array Ib, and obtain the actual voltage value of solar panel string c and record it in the corresponding actual voltage array Ic.

[0080] Step A04: If the voltage at the MPPT's DC input terminal has not decreased to the preset voltage, then continue to execute the steps of decreasing the voltage at the MPPT's DC input terminal corresponding to the target solar panel string by the first parameter value and subsequent steps. If the voltage at the MPPT's DC input terminal decreases to the preset voltage, then determine the current array and actual voltage array of each solar panel string in the solar panel array to be tested.

[0081] Specifically, there are three solar panel strings powering the MPPT. After the voltage at the DC input end of the MPPT is not reduced to a preset voltage, the actual voltage array and current array corresponding to solar panel string a are finally obtained, as are the actual voltage array Ua and current array Ia corresponding to solar panel string a, the actual voltage array Ub and current array Ib corresponding to solar panel string b, and the actual voltage array Uc and current array Ic corresponding to solar panel string c, and Ua, Ub, Uc, Ia, Ib, and Ic all include K elements.

[0082] Based on the actual voltage array and current array of each solar panel string to be tested, at least one current value can be determined. This current value is used to determine the current closest to or equal to 0, and the voltage value corresponding to this current is approximately the open-circuit voltage of the solar panel string.

[0083] In the embodiment of the present application, there are multiple possible implementations of step S203, which are described below. It should be noted that the implementations described below are only for illustrative purposes and do not represent all implementations of the embodiment of the present application.

[0084] In a first possible implementation, referring to a schematic flow chart of obtaining an open-circuit voltage as shown in FIG3 , two current values ​​are determined based on an actual voltage array and a current array, and a first open-circuit voltage of a target solar panel string is determined using voltage values ​​corresponding to the two current values, including:

[0085] Step B1: Determine a first current value I1 greater than or equal to zero and a first actual voltage value U1 corresponding to the first current value I1 according to the actual voltage array and the current array.

[0086] For example, referring to FIG3 , we can start from the first current value (i=0) in the current array. If I[i] is greater than or equal to zero, then I1=I[i], and determine U[i] from the actual current array according to the sorting number i, U1=U[i]; if I[i] is not greater than or equal to zero, then the sorting number i is increased by 1 (i=i+1), and continue to judge whether the current value in the current array is greater than or equal to zero, until the first current value I1 greater than or equal to zero in the current array is determined.

[0087] Step B2: Determine a first second current value I2 and a second actual voltage value U2 corresponding to the second current value that meet a preset condition; the preset condition is that a second product of the second current value and the second actual voltage value is greater than the product of a third current value preceding the second current value in the current array (the current value preceding the second current value in the current array of the solar panel string) and the actual voltage value corresponding to the third current value, and the second product is greater than the product of a fourth current value following the second current value (the current value following the second current value in the current array of the solar panel string) and the fourth actual voltage value corresponding to the fourth current value, and the position of the above-mentioned second current value in the current array is located after the above-mentioned first current value.

[0088] For example, referring to FIG3 , after determining the first first current value I1 that is greater than or equal to zero, the first second current value I2=I[i] that meets the preset conditions is then searched from the current values ​​following the first current value in the current array, and the second voltage value U2=U[i] corresponding to the second current value is determined.

[0089] Among them, the preset conditions are I[i]U[i]≥I[i-1]U[i-1] and I[i]U[i]≥I[i+1]U[i+1].

[0090] Specifically, the sorting position of the first current value in the current array is the same as the sorting position of the first actual voltage value in the actual voltage array. The sorting position of the second current value in the current array is the same as the sorting position of the second actual voltage value in the actual voltage array. The sorting position of the third current value in the current array is the same as the sorting position of the third actual voltage value in the actual voltage array. The sorting position of the fourth current value in the current array is the same as the sorting position of the fourth actual voltage value in the actual voltage array.

[0091] Step B3, the first open-circuit voltage Uopen is the ratio of the first parameter to the second parameter, the first parameter is the difference between the product of the first current value and the second actual voltage value and the product of the second current value and the first actual voltage value, and the second parameter is the difference between the first current value and the second current value.

[0092] Specifically, the formula of the first open-circuit voltage Uopen is: Uopen=(I1U2-I2U1) / (I1-I2).

[0093] This possible implementation is to approximate the right side of the local peak point closest to the first open-circuit voltage with a straight line to fit the approximate first open-circuit voltage.

[0094] As can be seen from steps B1-B3 above, the present application filters out two current values, I1 and I2, from the current array and determines the corresponding voltage values, U1 and U2, to calculate the open-circuit voltage. This significantly reduces the computational effort required to determine the open-circuit voltage and improves its efficiency. Furthermore, this calculation method is simple and can be implemented within the inverter's processor, eliminating the need for a separate processor for curve fitting to determine the open-circuit voltage, thus saving costs.

[0095] In a second possible implementation, at least one current value is determined based on the actual voltage array and the current array, and the open-circuit voltage of the target solar panel string is determined using a voltage value corresponding to the at least one current value, including:

[0096] Step C1: In the current array, if it is determined that the n-1th current value is less than zero and the nth current value is greater than or equal to zero, the nth actual voltage value in the actual voltage array is used as the open circuit voltage.

[0097] If the n-1th current value in the current array is less than zero and the nth current value is greater than zero or equal to zero, then only one current value I[n] needs to be screened out in the current array, and the nth actual voltage value in the actual voltage array can be approximated as the open-circuit voltage U[n].

[0098] For example, please refer to another flow chart of obtaining the open circuit voltage shown in Figure 4. The specific screening method includes:

[0099] The loop can be started from the n=1th current array. If I[n-1]<0 and I[n]>0 are not satisfied, then n=n+1 is continued to loop. If I[n-1]<0 and I[n]>0 are satisfied, then the nth actual voltage value is found in the actual voltage array as the open-circuit voltage Uopen, that is, Uopen=U[n], where I[n] is the Nth current value in the current array, and the same applies to I[n-1].

[0100] Step C2: If all current values ​​in the current array are greater than zero, determine the first current value in the current array; if the first current value is less than or equal to the current threshold, use the first actual voltage value in the actual voltage array corresponding to the first current value as the first open-circuit voltage.

[0101] Specifically, if all current values ​​in the current array are greater than zero, the first current value in the current array is determined to be the first current value for analysis. If the first current value does not exceed the current threshold, the actual voltage value corresponding to the first current value (the first actual voltage value in the actual voltage array) can be approximated as the open-circuit voltage. The current threshold is the current value at which the corresponding voltage value can be approximated as the open-circuit voltage. Exemplarily, the current threshold is close to zero, such as 1 ampere, to ensure that the first current value is not too large and the actual voltage value corresponding to the first current value can be approximated as the open-circuit voltage.

[0102] Step C3: If the first current value is greater than the current threshold, execute the method of steps B1 to B3 to determine the open circuit voltage.

[0103] As can be seen from steps C1-C3 above, the present application determines that if the n-1th current value in the current array is less than zero and the nth current value is greater than zero or equal to zero, or if all current values ​​are greater than zero and the first current value does not exceed the current threshold, the first current value can be directly determined and the actual voltage corresponding to the first current value can be approximated as the open-circuit voltage. If conditions C1 or C2 are not met, steps B1-B3 are then used. That is, if the n-1th current value in the current array is less than zero and the nth current value is greater than zero or equal to zero, or if the first current value does not exceed the current threshold, the open-circuit voltage can be directly approximated without calculation, further reducing the amount of computation required.

[0104] Based on the above embodiment, in a possible implementation, when the amount of calculation can be reduced compared to curve fitting, in particular, when there are multiple solar panel strings to be tested, each solar panel string in the solar panel strings to be tested can be used as a target solar panel string, and steps B1-B3 or steps C1-C3 can be used to determine the first open-circuit voltage of the target solar panel string.

[0105] Based on the first open-circuit voltage of the target solar panel string, in step S204 of FIG. 2 , a circuit breaker abnormality is determined for the target solar panel string based on the first open-circuit voltage. If the abnormality is determined, a warning can be issued to the user. The user only needs to repair the circuit breaker of the abnormal solar panel string that has been warned, thus narrowing the scope of the repair.

[0106] In the embodiment of the present application, step S204 in FIG. 2 determines, based on the first open-circuit voltage, that a circuit breaker abnormality exists in the target solar panel string, and there are multiple possible implementations.

[0107] In one possible implementation, when the first open circuit voltage meets the abnormal condition, it is determined that the target solar panel string has a circuit breaker abnormality; when the first open circuit voltage does not meet the abnormal condition, it is determined that the target solar panel string does not have a circuit breaker abnormality.

[0108] In this possible implementation, the first open-circuit voltage is compared with the abnormal condition to determine whether the solar panel string has an abnormality. Of course, in another possible implementation, multiple first open-circuit voltages of the target solar panel string can be obtained, and the cumulative number of abnormalities of the multiple first open-circuit voltages exceeds a preset value for determination. The specific method is as follows:

[0109] Step D1: If the first open-circuit voltage meets the preset abnormal condition, the abnormal number of the target solar panel string is increased by one, and the current accumulated abnormal number of the target solar panel string is obtained; if the abnormal number exceeds the preset value, then the target solar panel string has a circuit breaker abnormality, and the preset value is the number of times required to determine that the target solar panel string has a circuit breaker abnormality; if the abnormal number does not exceed the preset value, continue to execute the inverter blocking voltage and subsequent steps [steps S201-S204].

[0110] Step D2: If the first open-circuit voltage does not meet the preset abnormal condition, continue to obtain the blocking voltage of the inverter and subsequent steps.

[0111] Repeating steps S201-S204 (D1 or D2) to obtain the open-circuit voltage of the solar panel string multiple times, the number of abnormalities of the solar panel string is cumulatively determined to reduce misjudgment and reliably determine the abnormal solar panel string.

[0112] For example, the preset value can be set according to user needs. For example, the user can reset the accumulated number of abnormalities to zero, start repeating steps S201-S204 (D1 or D2), accumulate the number of abnormalities, and compare it with the preset value. When an abnormal solar panel string is detected, an early warning is issued to the user, and subsequent manual control is suspended.

[0113] Furthermore, for each MPPT, the steps of obtaining the inverter's closing wave voltage and subsequent steps [S201-S204, where step S204 executes (D1 or D2)] can be repeatedly executed in each cycle until it is confirmed that the target solar panel string has a circuit breaker abnormality, or, if the target solar panel string has not been confirmed to have a circuit breaker abnormality after a preset number of repetitions or a preset repetition time, then the target solar panel string does not have a circuit breaker abnormality; the preset value is the number of times required to determine that the target solar panel string has a circuit breaker abnormality within the cycle.

[0114] The period can be monthly, weekly, or daily, and other periods are also possible. For example, the preset number of repetitions can be 20 times per week, and the corresponding preset value can be 15 times. Of course, other types of preset repetitions and preset values ​​can also be used for each period. The same applies to the preset duration.

[0115] The accumulated number of exceptions is cleared at the beginning of each cycle, and the accumulated number of exceptions starts from zero in each cycle.

[0116] In the embodiment of the present application, in step S204 of FIG. 2 , if the first open-circuit voltage satisfies the preset abnormal condition, there are multiple possible implementations, which are described below. It should be noted that the implementations described below are only exemplary and do not represent all implementations of the embodiment of the present application.

[0117] The preset abnormal condition may be comparing the open circuit voltage with a manually preset voltage threshold or interval to determine whether the first open circuit voltage meets the preset abnormal condition.

[0118] The preset abnormal condition is set based on the first open-circuit voltage of the target solar panel string and a historical value, wherein the historical value is set based on the historical first open-circuit voltage of the target solar panel string. Of course, other methods can also be used to preset the abnormal condition.

[0119] When the preset abnormal condition is set based on the first open-circuit voltage of the target solar panel string and the historical record value, there are multiple possible implementation methods, which are described below. It should be noted that the implementation methods given in the following description are only for illustrative purposes and do not represent all implementation methods of the embodiments of this application.

[0120] In one possible implementation.

[0121] The specific method for determining whether the first open circuit voltage meets the preset abnormal condition includes:

[0122] Step E1: Determine whether the first open-circuit voltage of the target solar panel string is less than a historical record value.

[0123] Step E2: If the first open-circuit voltage is less than the historical value, and a first comparison value between the historical value and the first open-circuit voltage is greater than a first threshold, the first open-circuit voltage is determined to meet a preset abnormal condition. The first threshold is set based on the target solar panel string nominal open-circuit voltage.

[0124] Step E3: If the first open circuit voltage is greater than or equal to the historical record value, the first open circuit voltage does not meet the preset abnormal condition.

[0125] Step E4: If the first open circuit voltage is greater than the historical record value, update the historical record value.

[0126] Among them, the historical record value can be the maximum first open-circuit voltage value in the historical record, or the historical record value can also be the average value of multiple first open-circuit voltage values ​​recorded in the historical record within a preset time length, or the historical record value can also be the average value of multiple first open-circuit voltages sorted from large to small within the preset time length.

[0127] The comparison value may be a difference, a ratio, or other values ​​that can achieve comparison.

[0128] The first threshold and the target solar panel string nominal open circuit voltage satisfy a preset proportional relationship.

[0129] For example, the first comparison value may be a difference value, and the historical record value may be the maximum first open circuit voltage value in the historical record. See FIG5 for a schematic flow chart of determining whether the first open circuit voltage satisfies a preset abnormal condition. The specific steps for determining whether the first open circuit voltage satisfies the preset abnormal condition may be:

[0130] Step E01: Determine whether the first open-circuit voltage Uopen is less than a historical record value.

[0131] Step E02: If the first open circuit voltage Uopen is less than the historical record value Uopenmax, and the difference between the historical record value and the first open circuit voltage (Uopenmax-Uopen) is greater than the first preset difference Uset, the first open circuit voltage meets the preset abnormal condition.

[0132] Step E03: If the first open circuit voltage Uopen is greater than or equal to the historical record value Uopenmax, the first open circuit voltage does not meet the preset abnormal condition.

[0133] Step E04 : If the first open-circuit voltage Uopen is greater than the historical record value Uopenmax, then the historical record value is updated to the first open-circuit voltage (Uopenmax=Uopen).

[0134] The method in which the first contrast value is a ratio is similar to the method in which the first contrast value is a difference.

[0135] For example, if the inverter does not initially store a historical record of the target solar panel string, a first open-circuit voltage of the target solar panel string is first obtained according to the above method and recorded as the historical record value, and then the above-mentioned method for determining whether a string circuit breaker abnormality exists is performed. Of course, the initial historical record value can be a preset value or a value determined by other means.

[0136] In this embodiment, there may be one or more solar panel strings to be tested that supply power to the MPPT.

[0137] In another possible implementation.

[0138] There are multiple solar panel strings to be tested that power the MPPT. The open-circuit voltage of the target solar panel string is a first open-circuit voltage.

[0139] One of the multiple solar panel strings to be tested, excluding the target solar panel string, is used as the solar panel string to be compared. (For example, in steps A01-A04, among the three solar panel strings a, b, and c supplying power to the MPPT, if the target solar panel string is a, then the solar panel string to be compared is b or c. Below, the solar panel string to be compared is used as an example.) The open-circuit voltage of the solar panel string to be compared is the second open-circuit voltage. The second open-circuit voltage is determined in the same manner as the first open-circuit voltage.

[0140] Determining whether the first open circuit voltage meets a preset abnormal condition, specifically comprising:

[0141] Step F1 , calculating an absolute value of a second comparison value between a first open-circuit voltage of the target solar panel string a and a second open-circuit voltage of the solar panel string b to be compared.

[0142] Step F2: Determine whether the absolute value of the second comparison value is greater than the historical record value.

[0143] Step F3: If the absolute value of the second comparison value is greater than the historical record value, and a third comparison value between the absolute value of the second comparison value and the historical record value is greater than a second threshold, the open circuit voltage meets the preset abnormal condition.

[0144] Step F4: If the absolute value of the second comparison value is less than or equal to the historical record value, the first open circuit voltage does not meet the preset abnormal condition.

[0145] Step F5: If the absolute value of the second comparison value is smaller than the historical record value, then update the historical record value to the absolute value of the second comparison value.

[0146] The historical record value is set based on the absolute value of the second comparison value in the historical record. The first open-circuit voltage and the second open-circuit voltage corresponding to each second comparison value are determined by data obtained during the same step-down process of decreasing the voltage at the MPPT DC input terminal from the closed-wave voltage to the preset voltage. The comparison value is the open-circuit voltage of the target solar panel string a and the open-circuit voltage of the solar panel string b to be compared. The historical record value is the maximum absolute value of the second comparison value in the historical record, or the average absolute value of multiple second comparison values ​​in the historical record, or the average absolute value of a preset number of second comparison values ​​ranked first in descending order within a preset interval. Of course, the historical record value can also be determined based on the second comparison value.

[0147] The second threshold is set according to the target solar panel string nominal open circuit voltage. For example, the second threshold and the target solar panel string nominal open circuit voltage satisfy a preset proportional relationship.

[0148] The comparison value may be a difference or a ratio, or may be a value determined by other algorithms that can compare the two.

[0149] For example, referring to another flow chart of determining whether the first open circuit voltage satisfies a preset abnormal condition as shown in FIG6 , the comparison value is set as a difference value, and the historical record value is the maximum absolute value of the second comparison value in the historical record. The specific method for determining whether the first open circuit voltage satisfies the preset abnormal condition includes:

[0150] The target solar panel string a has a first open-circuit voltage Uopen1 , and the target solar panel string b has a second open-circuit voltage Uopen2 .

[0151] Step F01 : Calculate a second absolute value of a difference between a first open-circuit voltage of a target solar panel string and a second open-circuit voltage of a solar panel string to be compared, ΔU=|Uopen1−Uopen2|.

[0152] Step F02 : Determine whether ΔU is greater than the historical record value ΔUmax.

[0153] In step F03 , if ΔU is greater than the historical value ΔUmax, and a third difference (ΔU−ΔUmax) between the absolute value of the second difference and the historical value is greater than a second preset difference ΔUset, then the first open-circuit voltage Uopen1 of the target solar panel string a meets the preset abnormal condition.

[0154] Step F04 : If ΔU is less than or equal to the historical record value ΔUmax, the open-circuit voltage Uopen1 of the target solar panel string a does not meet the preset abnormal condition.

[0155] Step F05 : If ΔU is less than the historical record value ΔUmax, then the historical record value is updated to the second absolute value of the difference (ΔUmax=ΔU).

[0156] The historical record value is a maximum absolute value ΔUmax of a first difference between a first open-circuit voltage of the target solar panel string a and a second open-circuit voltage of the solar panel string b to be compared.

[0157] The second preset difference and the target solar panel string nominal open-circuit voltage satisfy a preset proportional relationship.

[0158] Illustratively, the solar panel string to be compared may be any one of the solar panel strings to be tested except the target solar panel string, or may be one of the solar panel strings to be tested except the target solar panel string that supplies power to the MPPT and is selected based on human needs.

[0159] For example, if the inverter does not store historical records for the solar panel string, a first absolute value of the difference can be obtained and recorded as the historical record value, and then the aforementioned method for determining a string circuit breaker anomaly is performed. Of course, the initial value of the historical record value can also be a manually preset value.

[0160] A method for determining whether a string circuit breaker is abnormal is described above, provided in an embodiment of the present application. The method for determining whether a string circuit breaker is abnormal is exemplified below with reference to a specific application scenario.

[0161] There are three solar panel strings to be tested that are set to MPPT power supply (taking solar panel strings a, b, and c as an example). Referring to FIG7 , an application flow chart of a method for determining whether a string has a circuit breaker abnormality is shown. A method for determining whether a string has a circuit breaker abnormality may specifically include:

[0162] Step G1: Obtaining a blocking voltage of the inverter. The blocking voltage is a voltage at a DC input terminal of the inverter when a first circuit in the inverter is closed. The first circuit includes an inverter circuit.

[0163] Step G2: Control the voltage at the DC input terminal of the MPPT corresponding to the target solar panel string to be the closed-wave voltage.

[0164] Step G3: Decrease the voltage of the current DC input terminal of the MPPT by a first parameter value.

[0165] Step G4: Obtain the actual voltage value of the target solar panel string, and store the actual voltage value into an actual voltage array of the target solar panel string.

[0166] The target solar panel string is one of the solar panel strings to be tested.

[0167] Step G5: Obtain the current value of the target solar panel string, and store the current value in the current array of the target solar panel string.

[0168] Step G6: If the voltage of the MPPT DC input terminal does not decrease to the preset voltage, continue to execute steps G3-G6. If the voltage of the MPPT DC input terminal decreases to the preset voltage, determine the current array and actual voltage array of the target solar panel string.

[0169] Elements in the same sorting position in the current array and the actual voltage array are correspondingly obtained in the same execution of steps G3-G6.

[0170] In one possible implementation, while looping steps G3-G6 to obtain the actual voltage array and current array of the target solar panel string, the actual voltage array and current array corresponding to each of the other solar panel strings in the solar panel string to be tested can also be obtained simultaneously. For example, after obtaining the actual voltage array Ua and current array Ia corresponding to target solar panel string a, the actual voltage array Ub and current array Ib corresponding to solar panel string b in the solar panel string to be tested, as well as the actual voltage array Uc and current array Ic corresponding to solar panel string c, can also be obtained.

[0171] Step G7: Based on the current array of the target solar panel string, if it is determined that the n-1th current value is less than zero and the nth current value is greater than or equal to zero, the nth actual voltage value in the actual voltage array of the target solar panel string is used as the first open-circuit voltage. If all current values ​​in the current array are greater than zero, the first current value in the current array is determined. Further, if the first current value is less than or equal to the current threshold, the first actual voltage value in the actual voltage array of the target solar panel string is used as the first open-circuit voltage. If the first current value is greater than the current threshold, steps B1-B3 are executed as shown in FIG. Finally, the first open-circuit voltage of the target solar panel string is determined.

[0172] Specifically, according to the actual voltage array and current array of each solar panel string, step G7 is executed to determine the open-circuit voltage Uopen1 of the target solar panel string a. Similarly, the open-circuit voltage Uopen2 of the solar panel string b and the open-circuit voltage Uopen3 of the solar panel string c can be obtained.

[0173] Step G8: If the first open-circuit voltage does not meet the preset abnormal condition, then continue with step G1 and subsequent steps. If the first open-circuit voltage of the target solar panel string meets the preset abnormal condition, the abnormality count of the target solar panel string is incremented by one, and the current cumulative abnormality count of the target solar panel string is obtained. If the abnormality count does not exceed the preset value, then continue with step G1 and subsequent steps. If the abnormality count exceeds the preset value, then a circuit breaker abnormality exists in the target solar panel string, and an early warning is issued.

[0174] Specifically, if Uopen1 meets the preset abnormal condition, the abnormal number of the target solar panel string a is increased by 1. Similarly, if Uopen2 of solar panel string b executes step G8 and meets the preset abnormal condition, the abnormal number of solar panel string b is increased by 1. If Uopen3 of solar panel string c executes step G8 and meets the preset abnormal condition, the abnormal number of solar panel string c is increased by 1.

[0175] The cumulative number of abnormalities corresponding to target solar panel string a is the number of abnormalities after the current abnormality number + 1. If the number of abnormalities for target solar panel string a exceeds the preset value, a warning is issued to the user indicating that a circuit breaker abnormality exists in target solar panel string a. The same applies to solar panel strings b and c.

[0176] Whether the first open circuit voltage satisfies the preset abnormal condition may be determined by using steps E1 to E4 or steps F1 to F5.

[0177] According to the above steps G1-G8, abnormal solar panel strings can be located, and solar panel strings without abnormalities do not need to be repaired, thus eliminating the maintenance scope and improving the efficiency of abnormality positioning and maintenance.

[0178] Furthermore, the above steps G1-G8 can be repeated a preset number of times or for a preset duration in each cycle (e.g., monthly, weekly, daily). If the number of abnormalities of one or more solar panel strings exceeds a preset value in each cycle, the circuit breaker of the solar panel string that has been warned can be repaired.

[0179] The above are some specific implementations of a method for determining whether a string circuit breaker is abnormal in an embodiment of the present application. Based on this, the present application also provides a corresponding device. The device provided in the embodiment of the present application will be introduced from the perspective of functional modularization.

[0180] FIG8 is a schematic diagram of a structure of a device for determining whether a string circuit breaker is abnormal. Referring to FIG8 , the device for determining whether a string circuit breaker is abnormal includes:

[0181] The wave-sealing module 801 is configured to obtain a wave-sealing voltage of the inverter. The wave-sealing voltage is the voltage at the DC input terminal of the inverter when the first circuit in the inverter is closed. The first circuit includes the inverter circuit.

[0182] The first circuit may further include a DC boost circuit.

[0183] The processing module 802 is configured to obtain an actual voltage array and a current array of the target solar panel string during a step-down process of decreasing the voltage at the MPPT DC input terminal corresponding to the target solar panel string from a closed-wave voltage to a preset voltage, wherein elements at the same position in the actual voltage array and the current array are obtained in the same step-down process. The target solar panel string is one of the solar panel strings to be tested.

[0184] Exemplarily, the preset voltage may be a starting voltage of the inverter or a preset multiple of the blocking voltage, where the preset multiple is less than 1.

[0185] The calculation module 803 is configured to determine at least one current value according to the actual voltage array and the current array, and determine a first open-circuit voltage of the target solar panel string according to a voltage value corresponding to the at least one current value.

[0186] The confirmation module 804 is configured to determine whether a circuit breaker abnormality exists in the target solar panel string based on the first open circuit voltage.

[0187] According to the aforementioned device for determining a circuit breaker anomaly in a solar string, a calculation module determines at least one current value from a current array and an actual voltage array, and combines this current with the voltage value corresponding to the current to determine the first open-circuit voltage of the target solar panel string. This avoids the computational complexity associated with curve fitting and the cost associated with the need for an additional curve fitting processor. Furthermore, the confirmation module determines the anomaly of the target solar panel string based on the first open-circuit voltage, thus avoiding the difficulty of determining circuit breaker damage based on changes in the string operating voltage, which can be affected by factors such as cloud obstruction and string contamination.

[0188] Furthermore, the processing module 802 is further configured to decrease the voltage of the DC input terminal of the MPPT corresponding to the target solar panel string by a first parameter value; obtain the actual voltage value of the target solar panel string, and store the actual voltage value in the actual voltage array of the target solar panel string; obtain the current value of the target solar panel string, and store the current value in the current array of the target solar panel string; if the voltage of the DC input terminal of the MPPT does not decrease to the preset voltage, continue to execute the steps of decreasing the voltage of the DC input terminal of the MPPT corresponding to the target solar panel string by the first parameter value and subsequent steps; if the voltage of the DC input terminal of the MPPT decreases to the preset voltage, determine the current array and the actual voltage array of the target solar panel string.

[0189] In one possible implementation, the calculation module 803 is configured to determine, based on the actual voltage array and the current array, a first first current value greater than or equal to zero and a first actual voltage value corresponding to the first current value; determine a first second current value that meets a preset condition and a second actual voltage value corresponding to the second current value; the preset condition is that a second product value of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and an actual voltage value corresponding to the third current value, and the second product value is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the position of the second current value in the current array is after the first current value; the ratio of the first parameter to the second parameter is used as the first open-circuit voltage, the first parameter is the difference between the product of the first current value and the second actual voltage value and the product of the second current value and the first actual voltage value, and the second parameter is the difference between the first current value and the second current value.

[0190] In one possible implementation, the calculation module 803 is configured to, in the current array, if it is determined that the n-1th current value is less than zero and the nth current value is greater than zero or equal to zero, then use the nth actual voltage value in the actual voltage array as the open-circuit voltage; if all current values ​​in the current array are greater than zero, then determine the first first current value in the current array, and if the first current value is less than or equal to the current threshold, then use the first actual voltage value in the actual voltage array corresponding to the first current value as the first open-circuit voltage; if the first current value is greater than the current threshold, then determine the first second current value that meets the preset conditions and the second actual voltage value corresponding to the second current value, and the preset conditions The condition is that a second product value of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and an actual voltage value corresponding to the third current value, and the second product value is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the position of the second current value in the current array is after the first current value; a ratio of the first parameter to the second parameter is used as the first open-circuit voltage, the first parameter is a difference between the product of the first current value and the second actual voltage value and the product of the second current value and the first actual voltage value corresponding to the first current value, and the second parameter is a difference between the first current value and the second current value.

[0191] In one possible implementation, the confirmation module 804 is configured to increase the number of abnormalities of the target solar panel string once and obtain the current accumulated number of abnormalities of the target solar panel string if the first open-circuit voltage meets the preset abnormal condition; if the number of abnormalities exceeds the preset value, there is a circuit breaker abnormality in the target solar panel string, and the preset value is the number of times required to determine that there is a circuit breaker abnormality in the target solar panel string; if the number of abnormalities does not exceed the preset value, continue to execute the steps of obtaining the closing wave voltage of the inverter and subsequent steps; if the first open-circuit voltage does not meet the preset abnormal condition, continue to execute the steps of obtaining the closing wave voltage of the inverter and subsequent steps.

[0192] In a possible implementation, the preset abnormal condition is set according to the first open-circuit voltage of the target solar panel string and a historical record value, where the historical record value is a value set based on the historical first open-circuit voltage of the target solar panel string.

[0193] Furthermore, in one possible implementation, the confirmation module is further configured to determine that the open-circuit voltage meets a preset abnormality condition if the first open-circuit voltage is less than a historical record value and a first comparison value between the historical record value and the first open-circuit voltage is greater than a first threshold value; the first threshold value is set based on the nominal open-circuit voltage of the target solar panel string. If the first open-circuit voltage is greater than the historical record value, the historical record value is updated, and the open-circuit voltage does not meet the preset abnormality condition; or if the first open-circuit voltage is equal to the historical record value, the open-circuit voltage does not meet the preset abnormality condition.

[0194] The historical record value is the maximum first open-circuit voltage value in the historical record, or the historical record value is the average value of multiple first open-circuit voltage values ​​in the historical record within a preset time length, or the historical record value is the average value of multiple first open-circuit voltages ranked from large to small within the preset time length.

[0195] In another possible implementation, there are multiple solar panel strings to be tested that power the MPPT. The confirmation module is further configured to confirm that the first open-circuit voltage meets a preset abnormal condition if the absolute value of a second comparison value between the first open-circuit voltage and the second open-circuit voltage is greater than a historical record value, and a third comparison value between the absolute value of the second comparison value and the historical record value is greater than a second threshold. The second open-circuit voltage is the open-circuit voltage of the solar panel string to be compared, and the solar panel string to be compared is one of the solar panel strings to be tested, excluding the target solar panel string. The historical record value is set based on the absolute value of the second comparison value in the historical record. The first open-circuit voltage and the second open-circuit voltage of each second comparison value are determined by data obtained during the same step-down process of decreasing the voltage at the MPPT DC input terminal from the closed-wave voltage to the preset voltage. The second threshold is set based on the nominal open-circuit voltage of the solar panel string. The confirmation module is further configured to update the historical record value to the absolute value of the second comparison value if the absolute value of the second comparison value is less than the historical record value, and confirm that the first open-circuit voltage does not meet the preset abnormal condition. Alternatively, the absolute value of the second comparison value is equal to the historical record value, confirming that the first open circuit voltage does not meet the preset abnormal condition.

[0196] The historical record value is the maximum value of the absolute values ​​of the second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of multiple second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of a preset number of second comparison values ​​that are sorted from large to small within a preset segment.

[0197] The embodiment of the present application also provides an inverter for implementing the solution provided in the embodiment of the present application.

[0198] An inverter adopts the above-mentioned method for determining whether a string has a shutdown abnormality, and is used to determine whether a target solar panel string has a shutdown abnormality.

[0199] The inverter may include at least one MPPT, and each MPPT may be powered by at least one solar panel string.

[0200] In one possible implementation, referring to a schematic diagram of a connection structure between an inverter and a solar panel shown in FIG9 , the inverter includes multiple MPPTs (MPPT1 and MPPT2 are taken as examples in FIG9 ), each MPPT is connected to multiple solar panel strings (for example, MPPT1 in FIG9 can be connected to solar panel string 1 and solar panel string 2, and MPPT2 can be connected to solar panel string 3 and solar panel string 4); the solar panel strings include solar panels PV and circuit breakers, and the solar panels and circuit breakers are connected one-to-one (for example, solar panel PV11 in FIG9 is connected to circuit breaker 11, solar panel PV12 is connected to circuit breaker 12, solar panel PV13 is connected to circuit breaker 13, etc.), and the circuit breakers included in each solar panel string are sequentially connected in series and then connected to an MPPT in the inverter (for example, circuit breakers 11, 12, and 13 in solar panel string 1 in FIG9 are sequentially connected in series, and the head end and the end end are both connected to MPPT1), for powering the MPPT.

[0201] In the inverter corresponding to FIG9 , step S202 and subsequent steps may be performed on MPPT1 or MPPT2 separately, or may be performed on both MPPT1 and MPPT2 simultaneously.

[0202] In another possible implementation, referring to another schematic diagram of the connection structure between the inverter and the solar panel shown in FIG10 , the inverter includes multiple MPPTs (MPPT1 and MPPT2 are taken as examples in FIG10 ), each MPPT is connected to multiple solar panel strings, the solar panel strings include solar panels and circuit breakers, each circuit breaker is connected to multiple solar panels (for example, the circuit breaker 11 in FIG10 can be connected to the solar panel PV11 and the solar panel PV12), and the circuit breakers included in each solar panel string are connected in series in sequence and then connected to an MPPT in the inverter (for example, in FIG10 , the head end and the end of the series connection of circuit breakers 11 and 12 in the solar panel string 1 are both connected to MPPT1) for powering the MPPT.

[0203] In the inverter corresponding to FIG10 , step S202 and subsequent steps may be performed on MPPT1 or MPPT2 separately, or may be performed on both MPPT1 and MPPT2 simultaneously.

[0204] The embodiment of the present application also provides a photovoltaic system, including a solar string and an inverter;

[0205] A solar panel string is connected to an input end of an inverter, and an output end of the inverter is connected to a power grid or a load; the solar panel string is configured to output direct current to the inverter; the inverter is configured to receive direct current and output alternating current to the power grid or the load, and using one of the above-mentioned methods for determining whether a circuit breaker abnormality exists in a string, it is determined whether a target solar panel string connected to the inverter has a circuit breaker abnormality.

[0206] The embodiments of the present application also provide corresponding devices and computer storage media for implementing the solutions provided by the embodiments of the present application.

[0207] The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute instructions or codes, so that the device executes a method for determining whether a string breaker abnormality exists in any embodiment of the present application.

[0208] The computer storage medium stores code. When the code is executed, the device executing the code implements a method for determining whether a string circuit breaker abnormality exists in any embodiment of the present application.

[0209] The "first" and "second" in the names such as "first" and "second" (if any) mentioned in the embodiments of this application are only used as name identifiers and do not represent the first or second in order.

[0210] Through the description of the above embodiments, it can be known that those skilled in the art can clearly understand that all or part of the steps in the above embodiment methods can be implemented by means of software plus a general hardware platform. Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as a read-only memory (ROM) / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network communication device such as a router) to execute the methods described in each embodiment or certain parts of the embodiments of the present application.

[0211] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiment. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment. Those of ordinary skill in the art can understand and implement it without paying any creative work.

[0212] The above description is merely an exemplary embodiment of the present application and is not intended to limit the scope of protection of the present application.

Claims

1. A method for determining whether a string circuit breaker is abnormal, the method comprising: Obtaining a blocking voltage of the inverter, wherein the blocking voltage is a voltage at a DC input terminal of the inverter when a first circuit in the inverter is closed, wherein the first circuit includes an inverter circuit; In the process of reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from the closed-wave voltage to the preset voltage, an actual voltage array and a current array of the target solar panel string are obtained, and the elements at the same position in the actual voltage array and the current array are obtained corresponding to the same reduction, and the target solar panel string is one of the solar panel strings to be tested; Determine at least one current value according to the actual voltage array and the current array, and determine a first open-circuit voltage of the target solar panel string by a voltage value corresponding to the at least one current value; Based on the first open circuit voltage, it is determined whether the target solar panel string has a circuit breaker abnormality.

2. The method according to claim 1, wherein in the process of reducing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from the closed wave voltage to the preset voltage, obtaining the actual voltage array and current array of the target solar panel string comprises: Decreasing the voltage of the DC input terminal of the MPPT corresponding to the target solar panel string by a first parameter value; Acquire an actual voltage value of the target solar panel string, and store the actual voltage value into an actual voltage array of the target solar panel string; Acquire the current value of the target solar panel string, and store the current value in the current array of the target solar panel string; If the voltage at the DC input terminal of the MPPT does not decrease to the preset voltage, continue to execute the step of decreasing the voltage at the DC input terminal of the MPPT corresponding to the target solar panel string by the first parameter value and subsequent steps; if the voltage at the DC input terminal of the MPPT decreases to the preset voltage, determine the current array and actual voltage array of the target solar panel string.

3. The method according to claim 2, wherein determining at least one current value according to the actual voltage array and the current array, and determining the first open circuit voltage of the target solar panel string by the voltage value corresponding to the at least one current value, comprises: Determine, according to the actual voltage array and the current array, a first current value greater than or equal to zero and a first actual voltage value corresponding to the first current value; Determine a first second current value that meets a preset condition and a second actual voltage value corresponding to the second current value; The preset condition is that a second product value of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and an actual voltage value corresponding to the third current value, and the second product value is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the second current value is located after the first current value in the current array; The ratio of the first parameter to the second parameter is used as the first open circuit voltage, the first parameter is the difference between the product of the first current value and the second actual voltage value and the product of the second current value and the first actual voltage value, and the second parameter is the difference between the first current value and the second current value.

4. The method according to claim 2, wherein determining at least one current value according to the actual voltage array and the current array, and determining the first open circuit voltage of the target solar panel string by the voltage value corresponding to the at least one current value, comprises: In the current array, if it is determined that the n-1th current value is less than zero and the nth current value is greater than zero or equal to zero, then the nth actual voltage value in the actual voltage array is used as the open circuit voltage; If all current values ​​in the current array are greater than zero, then a first current value in the current array is determined; if the first current value is less than or equal to a current threshold, then a first actual voltage value in the first actual voltage array corresponding to the first current value is used as a first open circuit voltage; If the first current value is greater than the current threshold, a first second current value that satisfies a preset condition and a second actual voltage value corresponding to the second current value are determined, wherein the preset condition is that a second product value of the second current value and the second actual voltage value is greater than a product of a third current value preceding the second current value in the current array and an actual voltage value corresponding to the third current value, and the second product value is greater than a product of a fourth current value following the second current value and a fourth actual voltage value corresponding to the fourth current value, and the second current value is located after the first current value in the current array; The ratio of the first parameter to the second parameter is used as the first open-circuit voltage, the first parameter is the difference between the product of the first current value and the second actual voltage value and the product of the second current value and the first actual voltage value corresponding to the first current value, and the second parameter is the difference between the first current value and the second current value.

5. The method according to any one of claims 1 to 4, wherein determining that a circuit breaker abnormality exists in the target solar panel string based on the first open circuit voltage comprises: If the first open circuit voltage meets a preset abnormal condition, the abnormal number of the target solar panel string is increased once, and the current accumulated abnormal number of the target solar panel string is obtained; If the number of abnormalities exceeds a preset value, the target solar panel string has a circuit breaker abnormality, and the preset value is the number of times required to determine that the target solar panel string has a circuit breaker abnormality; if the number of abnormalities does not exceed the preset value, continue to perform the steps of obtaining the inverter's closing wave voltage and subsequent steps; If the first open circuit voltage meets a preset abnormal condition, the method further includes: If the first open circuit voltage does not meet the preset abnormal condition, the step of obtaining the blocking voltage of the inverter and subsequent steps are continued.

6. The method according to claim 5, further comprising: In each cycle, the step of obtaining the inverter's blocking voltage and subsequent steps is repeated until it is confirmed that the target solar panel string has a circuit breaker abnormality, or the repetition reaches a preset number of repetitions or a preset repetition duration; the preset value is the number of times required to determine that the target solar panel string has a circuit breaker abnormality in the cycle.

7. According to the method described in any one of claims 5 or 6, the preset abnormal condition is set according to the first open-circuit voltage of the target solar panel string and a historical record value, and the historical record value is a value set based on the historical first open-circuit voltage of the target solar panel string.

8. The method according to claim 7, wherein the first open circuit voltage satisfies a preset abnormal condition, comprising: The first open circuit voltage is less than the historical record value, and a first comparison value between the historical record value and the first open circuit voltage is greater than a first threshold; The first threshold is set according to the target solar panel string nominal open circuit voltage.

9. The method according to claim 8, The historical record value is the maximum first open circuit voltage value of the historical record, or the historical record value is a preset time The average value of multiple first open circuit voltage values ​​recorded in history within the preset time length, or the historical record value is the average value of multiple first open circuit voltages ranked from large to small within the preset time length.

10. The method according to claim 8 or 9, wherein the first open circuit voltage does not meet a preset abnormal condition, comprising: The first open circuit voltage is greater than the historical record value, and the historical record value is updated; Or, the first open circuit voltage is equal to the historical record value.

11. The method according to claim 7, wherein there are multiple solar panel strings to be tested that supply power to the MPPT; If the first open circuit voltage meets a preset abnormal condition, it includes: If the absolute value of the second comparison value between the first open-circuit voltage and the second open-circuit voltage is greater than the historical record value, and the absolute value of the second comparison value and the third comparison value of the historical record value are greater than the second threshold value; the second open-circuit voltage is the open-circuit voltage of the solar panel string to be compared, and the solar panel string to be compared is one of the solar panel strings to be tested except the target solar panel string, and the historical record value is set according to the absolute value of the second comparison value of the historical record, and the first open-circuit voltage and the second open-circuit voltage of each second comparison value are determined by data obtained in the same step-down process of reducing the voltage of the MPPT DC input terminal from the closing wave voltage to the preset voltage, and the second threshold is set according to the nominal open-circuit voltage of the solar panel string.

12. According to the method of claim 11, the historical record value is the maximum value of the absolute values ​​of the second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of multiple second comparison values ​​in the historical records, or the historical record value is the average value of the absolute values ​​of a preset number of second comparison values ​​in a preset segment that are sorted from large to small.

13. The method according to any one of claims 11 to 12, wherein the first open circuit voltage does not meet a preset abnormal condition, comprising: The absolute value of the second comparison value is smaller than the historical record value, and the historical record value is updated to be the absolute value of the second comparison value; Or, the absolute value of the second comparison value is equal to the historical record value.

14. The method according to claim 1, wherein the first circuit further comprises a DC boost circuit.

15. The method according to claim 1, characterized in that The preset voltage is a starting voltage of the inverter or a preset multiple of the sealing voltage, and the preset multiple is less than 1.

16. A device for determining whether a string circuit breaker is abnormal, the device comprising: A wave-blocking module is configured to obtain a wave-blocking voltage of the inverter, wherein the wave-blocking voltage is a voltage at a DC input terminal of the inverter when a first circuit in the inverter is closed, wherein the first circuit includes an inverter circuit; The processing module is configured to obtain an actual voltage array and a current array of the target solar panel string during a voltage reduction process of decreasing the voltage of the MPPT DC input terminal corresponding to the target solar panel string from a closed-wave voltage to a preset voltage, wherein the elements at the same position in the actual voltage array and the current array are obtained corresponding to the same reduction, and the target solar panel string is one of the solar panel strings to be tested; a calculation module configured to determine at least one current value according to the actual voltage array and the current array, and determine a first open circuit voltage of the target solar panel string by a voltage value corresponding to the at least one current value; The confirmation module is configured to determine whether there is a circuit breaker abnormality in the target solar panel string based on the first open circuit voltage.

17. An inverter, using the method for determining whether a string has a shutdown abnormality according to any one of claims 1 to 15, to determine whether a target solar panel string has a shutdown abnormality.

18. A photovoltaic system comprising a solar string and an inverter; The solar panel string is connected to the input end of the inverter, and the output end of the inverter is connected to the power grid or load; The solar panel string is configured to output direct current to the inverter; The inverter is configured to receive the direct current and output alternating current to a power grid or a load, and to determine whether a target solar panel string connected to the inverter has a switch abnormality by using a method for determining whether a string has a switch abnormality as described in any one of claims 1 to 15.

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