Photovoltaic inverter system, photovoltaic energy storage device and impedance balancing method

Abstract

The invention discloses a photovoltaic inverter system, a photovoltaic energy storage device and an impedance balancing method, and relates to the technical field of photovoltaic inverters.The photovoltaic inverter system comprises a photovoltaic inverter, MPPT branches connected with the photovoltaic inverter and an impedance balancing resistor connected between the positive end of a bus of the photovoltaic inverter and the control ground. Each MPPT branch is provided with a divider resistor. And determining a target resistance value of the impedance balance resistor according to the input voltage range of each MPPT branch and the resistance value of the divider resistor. According to the invention, the static impedance balance of the photovoltaic inverter can be realized at low cost on the basis of not influencing the working efficiency of the photovoltaic inverter.

Description

Technical Field

[0001] This application relates to the field of photovoltaic inverter technology, and in particular to a photovoltaic inverter system, a photovoltaic energy storage device and an impedance balancing method. Background Technology

[0002] As the power of photovoltaic (PV) inverters increases, the methods, approaches, and types of PV module connection also gradually increase. In practical applications, to enhance the adaptability of PV inverters to the connected PV modules, each channel of the PV inverter connected to a PV module is equipped with MPPT (Maximum Power Point Tracking) functionality. However, multiple channels equipped with MPPT functionality can lead to an imbalance in the static impedance of the positive and negative DC buses (i.e., positive and negative BUS) of the PV inverter, resulting in voltage deviations and affecting the normal operation of the PV inverter.

[0003] Currently, the static impedance of the positive and negative DC buses of a photovoltaic inverter is often balanced by adding more circuit components or two high-cost, high-power resistors. This not only increases costs but also reduces the operating efficiency of the photovoltaic inverter. Summary of the Invention

[0004] The main objective of this application is to provide a photovoltaic inverter system, a photovoltaic energy storage device, and an impedance balancing method, which aims to achieve static impedance balancing of the photovoltaic inverter at low cost without affecting its operating efficiency.

[0005] To achieve the above objectives, this application provides a photovoltaic inverter system, which includes a photovoltaic inverter, MPPT branches connected to the photovoltaic inverter, and an impedance balancing resistor connected between the positive terminal of the busbar of the photovoltaic inverter and the control ground. Each MPPT branch is provided with a voltage divider resistor.

[0006] The target resistance value of the impedance balancing resistor is determined based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor.

[0007] In one embodiment, the step of determining the target resistance value of the impedance balancing resistor based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor includes:

[0008] Obtain the target voltage value determined by each MPPT branch within its respective input voltage range;

[0009] The maximum voltage value among the target voltage values ​​is taken as the first voltage value, and the remaining target voltage values ​​are taken as the second voltage values.

[0010] The sum of the voltage differences between the first voltage value and each of the second voltage values ​​is determined to obtain the voltage deviation value;

[0011] The target resistance value of the impedance balancing resistor is determined based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor.

[0012] In one embodiment, the step of determining the target resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes:

[0013] Based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor, the candidate resistance value of the impedance balance resistor is calculated.

[0014] Based on the candidate resistance values, the target resistance value of the impedance balancing resistor is determined.

[0015] In one embodiment, the step of determining the target resistance value of the impedance balancing resistor based on the candidate resistance values ​​includes:

[0016] When all of the second voltage values ​​are not zero, the candidate resistance value is taken as the target resistance value of the impedance balancing resistor.

[0017] When all the second voltage values ​​are zero, the candidate resistance value is increased to obtain the target resistance value of the impedance balance resistor.

[0018] In one embodiment, the step of increasing the candidate resistance value to obtain the target resistance value of the impedance balance resistor includes:

[0019] The target resistance value of the impedance balance resistor is obtained by multiplying the candidate resistance value by a preset coefficient value.

[0020] In one embodiment, the step of determining the target resistance value of the impedance balancing resistor based on the candidate resistance values ​​includes:

[0021] Verify whether the candidate resistance value is within the preset resistance value range;

[0022] If so, the candidate resistance value is taken as the target resistance value of the impedance balancing resistor;

[0023] If not, adjust the candidate resistance value and use the adjusted candidate resistance value as the new candidate resistance value, then return to the step of verifying whether the candidate resistance value is within the preset resistance value range.

[0024] In one embodiment, the step of calculating the candidate resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes:

[0025] The product of the first voltage value and the resistance value of the voltage divider resistor is calculated, and the ratio of this product to twice the voltage deviation value is used to obtain the candidate resistance value of the impedance balance resistor.

[0026] In one embodiment, the step of determining the target resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes:

[0027] Based on the preset mapping relationship between the voltage value, voltage deviation value, resistance value of the voltage divider resistor and resistance value of the impedance balancing resistor, the resistance value of the impedance balancing resistor corresponding to the first voltage value, the voltage deviation value and the resistance value of the voltage divider resistor is obtained, and used as the target resistance value of the impedance balancing resistor.

[0028] In addition, to achieve the above objectives, this application also provides a photovoltaic energy storage device, which includes the photovoltaic inverter system described above.

[0029] Furthermore, to achieve the above objectives, this application also provides an impedance balancing method applied to the photovoltaic inverter system described above. The method includes:

[0030] Based on the input voltage range of each MPPT branch of the photovoltaic inverter system and the resistance value of the voltage divider resistor, determine the target resistance value of the impedance balance resistor of the photovoltaic inverter system.

[0031] In addition, to achieve the above objectives, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the impedance balancing method described above.

[0032] In addition, to achieve the above objectives, this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the impedance balancing method as described above.

[0033] This application provides a photovoltaic inverter system, which includes a photovoltaic inverter, MPPT branches connected to the photovoltaic inverter, and an impedance balancing resistor connected between the positive terminal of the photovoltaic inverter bus and the control ground. Each MPPT branch is equipped with a voltage divider resistor. The target resistance value of the impedance balancing resistor is determined based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor. Since the target resistance value is the resistance value required to eliminate impedance deviations in the photovoltaic inverter, by using an impedance balancing resistor with the target resistance value, impedance deviations in the photovoltaic inverter can be eliminated, thereby achieving static impedance balance of the photovoltaic inverter.

[0034] Therefore, this application only requires setting an impedance balancing resistor with an appropriate resistance value in the photovoltaic inverter to balance the static impedance of the photovoltaic inverter. Compared with the conventional method of using too many circuit components or two high-cost, high-energy-consuming high-power resistors to balance the static impedance of the photovoltaic inverter, this application not only achieves static impedance balancing of the photovoltaic inverter at a lower cost, but also does not affect the operating efficiency of the photovoltaic inverter. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of a conventional circuit structure for achieving static impedance balance of a photovoltaic inverter, provided for an embodiment of this application;

[0038] Figure 2 A schematic diagram of another conventional circuit structure for achieving static impedance balance of a photovoltaic inverter, provided for an embodiment of this application;

[0039] Figure 3 This is a schematic diagram of the structure of the photovoltaic inverter system provided in the first embodiment of this application;

[0040] Figure 4 This is an example circuit structure diagram of the photovoltaic inverter system provided in the first embodiment of this application;

[0041] Figure 5 This is a schematic flowchart of the impedance balancing method provided in the embodiments of this application.

[0042] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0043] Explanation of icon numbers:

[0044] 10. Photovoltaic inverter; PV1~PVn, MPPT branch; Rx, impedance balancing resistor; Ra, voltage divider resistor; GND, control ground; GNDD, power ground; V1~V3, target voltage value of MPPT branch. Detailed Implementation

[0045] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0046] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0047] As the power of photovoltaic (PV) inverters increases, the methods, approaches, and types of PV module connection also gradually increase. In practical applications, to enhance the adaptability of PV inverters to the connected PV modules, each line of the PV inverter connected to a PV module is equipped with MPPT (Multi-Purpose Test and Power Distribution) functionality. However, multiple lines equipped with MPPT functionality can lead to an imbalance in the static impedance of the positive and negative DC buses (i.e., positive and negative BUS) of the PV inverter, resulting in voltage deviations and affecting the normal operation of the PV inverter.

[0048] Currently, the commonly used methods are as follows: Figure 1 The circuit shown or as Figure 2 The circuit shown is used to balance the static impedance of the positive and negative DC buses of the photovoltaic inverter. However, Figure 1 The circuit shown requires multiple circuit components to balance the static impedance, and its implementation cost is relatively high. Figure 2 The circuit shown requires two high-power resistors to balance the static impedance. High-power resistors are expensive and consume a lot of energy, so they not only increase the cost of implementation but also reduce the efficiency of the photovoltaic inverter.

[0049] Based on this, this application provides a photovoltaic inverter system, which includes a photovoltaic inverter, MPPT branches connected to the photovoltaic inverter, and an impedance balancing resistor connected between the positive terminal of the photovoltaic inverter bus and the control ground. Each MPPT branch is equipped with a voltage divider resistor. The target resistance value of the impedance balancing resistor is determined based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor. Since the target resistance value is the resistance value required to eliminate impedance deviations in the photovoltaic inverter, by using an impedance balancing resistor with the target resistance value, impedance deviations in the photovoltaic inverter can be eliminated, thereby achieving static impedance balance of the photovoltaic inverter.

[0050] Therefore, this application only requires setting an impedance balancing resistor with an appropriate resistance value in the photovoltaic inverter to balance the static impedance of the photovoltaic inverter. Compared with the conventional method of using too many circuit components or two high-cost, high-energy-consuming high-power resistors to balance the static impedance of the photovoltaic inverter, this application not only achieves static impedance balancing of the photovoltaic inverter at a lower cost, but also does not affect the operating efficiency of the photovoltaic inverter.

[0051] This application presents a photovoltaic inverter system according to a first embodiment. Please refer to [link / reference]. Figure 3 The photovoltaic inverter system may include a photovoltaic inverter 10, each MPPT branch PV1 to PVn connected to the photovoltaic inverter 10, and an impedance balancing resistor Rx connected between the positive terminal of the busbar of the photovoltaic inverter 10 and the control ground GND. Each MPPT branch PV1 to PVn is equipped with a voltage divider resistor Ra.

[0052] The target resistance value of the impedance balancing resistor Rx is determined based on the input voltage range of each MPPT branch PV1 to PVn and the resistance value of the voltage divider resistor Ra.

[0053] It should be noted that the MPPT branch refers to the control channel connected to the MPPT function. The target resistance value refers to the resistance value required for the impedance balancing resistor Rx to eliminate the impedance deviation present in the photovoltaic inverter 10. The input voltage range of the MPPT branch includes all input voltage values ​​that the MPPT branch can achieve. Generally speaking, the input voltage range of each MPPT branch PV1 to PVn is the same, for example, it can all be 450 to 820V; the resistance value of the voltage divider resistor Ra on each MPPT branch PV1 to PVn is also the same.

[0054] Additionally, it should be noted that the impedance balancing resistor Rx is a resistor with a fixed resistance value equal to the target resistance value, not a resistor with a variable resistance value.

[0055] This embodiment provides a photovoltaic inverter system, which includes a photovoltaic inverter 10, MPPT branches PV1 to PVn connected to the photovoltaic inverter 10, and an impedance balancing resistor Rx connected between the positive terminal of the busbar of the photovoltaic inverter 10 and the control ground GND. Each MPPT branch PV1 to PVn is equipped with a voltage divider resistor Ra. Based on the input voltage range of each MPPT branch PV1 to PVn and the resistance value of the voltage divider resistor Ra, the target resistance value of the impedance balancing resistor Rx is determined. Since the target resistance value is the resistance value required to eliminate the impedance deviation existing in the photovoltaic inverter 10, by using the impedance balancing resistor Rx with the target resistance value, the impedance deviation existing in the photovoltaic inverter 10 can be eliminated, thereby achieving the static impedance balance of the photovoltaic inverter 10.

[0056] Therefore, in this embodiment, only one impedance balancing resistor Rx with a suitable resistance value needs to be set in the photovoltaic inverter 10 to balance the static impedance of the photovoltaic inverter 10. Compared with the conventional method of using too many circuit components or using two high-cost, high-energy-consuming high-power resistors to balance the static impedance of the photovoltaic inverter 10, this embodiment not only achieves static impedance balancing of the photovoltaic inverter 10 at a low cost, but also does not affect the operating efficiency of the photovoltaic inverter 10.

[0057] For example, taking a photovoltaic inverter system including three MPPT branches as an example, the photovoltaic inverter system can be as follows: Figure 4 The structure is shown in the diagram. In the diagram, GNDD represents power ground, and V1, V2, and V3 represent the target voltage values ​​of the three MPPT branches, respectively.

[0058] In one feasible implementation, the step of determining the target resistance value of the impedance balancing resistor Rx based on the input voltage range of each MPPT branch PV1 to PVn and the resistance value of the voltage divider resistor Ra may include steps S10 to S40:

[0059] Step S10: Obtain the target voltage values ​​of each MPPT branch PV1 to PVn within their respective input voltage ranges;

[0060] It should be noted that the target voltage value is selected from the input voltage range of the MPPT branch and is used as a reference voltage value to determine the target resistance value of the impedance balancing resistor Rx; the target voltage values ​​of each MPPT branch PV1 to PVn are not the same. When determining the target voltage value from their respective input voltage ranges, each MPPT branch PV1 to PVn can arbitrarily select one of the input voltage values ​​included in the input voltage range as the target voltage value.

[0061] Step S20: Take the maximum voltage value among the target voltage values ​​as the first voltage value, and take the remaining target voltage values ​​as the second voltage values.

[0062] Step S30: Determine the sum of the voltage differences between the first voltage value and each of the second voltage values ​​to obtain the voltage deviation value;

[0063] It should be noted that the voltage difference refers to the difference between the first voltage value and the second voltage value. The implementation process of step S30 can be represented by the following formula 1:

[0064] V(Vpv1,...,Vpvn)=(n-1)*Vpv1-Vpv2-...-Vpvn Formula 1

[0065] Where V(Vpv1,...,Vpvn) is the voltage deviation value, Vpv1 is the first voltage value, and each second voltage value includes Vpv2 to Vpvn.

[0066] Step S40: Determine the target resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor Ra.

[0067] It is understandable that the voltage deviation in a photovoltaic inverter is caused by impedance imbalance. Therefore, this embodiment first obtains the target voltage values ​​of each MPPT branch PV1 to PVn within their respective input voltage ranges; then, the maximum voltage value among the target voltage values ​​is taken as the first voltage value, and the remaining target voltage values ​​are taken as the second voltage values; next, the voltage deviation value is obtained by determining the sum of the voltage differences between the first voltage value and each second voltage value; then, by using the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor, the impedance balancing resistor value required to eliminate the impedance deviation in the photovoltaic inverter can be accurately determined.

[0068] Based on the first embodiment described above, a second embodiment of the photovoltaic inverter system of this application is proposed. In the second embodiment, step S40 may include steps S41 to S42:

[0069] Step S41: Calculate the candidate resistance value of the impedance balancing resistor Rx based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor Ra.

[0070] It should be noted that the candidate resistance value of the impedance balancing resistor Rx is a reference resistance value used to determine the target resistance value of the impedance balancing resistor Rx.

[0071] In one feasible implementation, step S41 specifically includes step S411:

[0072] Step S411: Calculate the product of the first voltage value and the resistance value of the voltage divider resistor Ra, and the ratio of this product to twice the voltage deviation value to obtain the candidate resistance value of the impedance balance resistor Rx.

[0073] It should be noted that the implementation process of step S411 can be represented by the following formula 2:

[0074]

[0075] Where X(Vpv1,...,Vpvn) are candidate resistance values, V(Vpv1,...,Vpvn) are voltage deviation values, Vpv1 is the first voltage value, and R is the resistance value of the voltage divider resistor Ra.

[0076] Step S42: Determine the target resistance value of the impedance balancing resistor Rx based on the candidate resistance values.

[0077] In one possible implementation of step S42, step S42 may include steps S01 to S02:

[0078] Step S01: When all the second voltage values ​​are not zero, the candidate resistance value is taken as the target resistance value of the impedance balancing resistor Rx.

[0079] Step S02: When all second voltage values ​​are zero, increase the candidate resistance value to obtain the target resistance value of the impedance balance resistor Rx.

[0080] It is understandable that, as shown in Formula 2 above, if all second voltage values ​​are zero, the resulting candidate resistance values ​​will be very small. In this case, if the candidate resistance value is directly used as the target resistance value of the impedance balancing resistor Rx, that is, if an impedance balancing resistor Rx with the resistance value of the candidate resistance value is set between the positive terminal of the bus of the photovoltaic inverter 10 and the control ground GND, then in the process of balancing the static impedance of the photovoltaic inverter 10, the impedance balancing resistor Rx will have a counteracting effect under other operating conditions because its resistance value is too small, thus failing to effectively balance the static impedance of the photovoltaic inverter 10. Therefore, this embodiment, by setting the values ​​so that when all the second voltage values ​​are not zero, the candidate resistance value can be directly used as the target resistance value of the impedance balancing resistor Rx; while when all the second voltage values ​​are zero, the candidate resistance value needs to be increased so that the increased candidate resistance value can be used as the target resistance value of the impedance balancing resistor Rx. This ensures that the set impedance balancing resistor Rx will not fail to balance the static impedance of the photovoltaic inverter 10 due to its small resistance value, thus guaranteeing the balancing effect of the impedance balancing resistor Rx on the static impedance of the photovoltaic inverter 10.

[0081] In one possible implementation of step S02, step S02 may include step S021:

[0082] Step S021: Increase the candidate resistance value by calculating the product of the candidate resistance value and the preset coefficient value to obtain the target resistance value of the impedance balance resistor Rx.

[0083] It should be noted that the preset coefficient value is a number greater than 1. The preset coefficient value can be a default value, such as 2; or it can be flexibly set by the user according to the actual situation, and this embodiment does not impose specific limitations on it.

[0084] This embodiment does not specifically limit the implementation of step S02. For example, in other feasible implementations, the candidate resistance value can be increased by calculating the sum of the candidate resistance value and the preset resistance increment to obtain the target resistance value of the impedance balance resistor Rx. The preset resistance increment can be a default value or can be flexibly set by the user according to actual conditions; this embodiment does not specifically limit this.

[0085] In another possible implementation of step S42, step S42 may include steps S03 to S05:

[0086] Step S03: Verify whether the candidate resistance value is within the preset resistance value range;

[0087] It should be noted that if the resistance value of the impedance balancing resistor Rx is too small, it will not be able to completely eliminate the impedance deviation in the photovoltaic inverter 10; if the resistance value of the impedance balancing resistor Rx is too large, it may disrupt the previously achieved impedance balance, causing the photovoltaic inverter 10 to face the problem of static impedance imbalance again. Therefore, to ensure that the impedance balancing resistor Rx can effectively eliminate the impedance deviation in the photovoltaic inverter 10, its resistance value should be set within a specific range. This resistance value range can be a default range, or it can be flexibly set by the user according to the actual situation; this embodiment does not impose specific limitations on it.

[0088] Step S04: If yes, then the candidate resistance value is used as the target resistance value of the impedance balancing resistor.

[0089] Step S05: If not, adjust the candidate resistance value and use the adjusted candidate resistance value as the new candidate resistance value, then return to the step of verifying whether the candidate resistance value is within the preset resistance value range.

[0090] It should be noted that during the adjustment of the candidate resistance value, if the candidate resistance value is less than the lower limit of the resistance range, the candidate resistance value needs to be increased; if the candidate resistance value is greater than the upper limit of the resistance range, the candidate resistance value needs to be decreased. Specifically, increasing the candidate resistance value can be achieved by multiplying the candidate resistance value by a preset coefficient value; conversely, decreasing the candidate resistance value can be achieved by calculating the ratio of the candidate resistance value to a preset coefficient value. This embodiment does not specifically limit the method for adjusting the candidate resistance value.

[0091] It is understandable that, based on the foregoing, if the resistance value of the impedance balancing resistor Rx is too small or too large, it will prevent the impedance balancing resistor Rx from effectively balancing the static impedance of the photovoltaic inverter 10. Therefore, this embodiment sets the following: if the candidate resistance value is within a preset resistance value range, it can be directly used as the target resistance value of the impedance balancing resistor Rx; if the candidate resistance value is outside the preset resistance value range, the candidate resistance value needs to be adjusted until it is within the preset resistance value range, and then the adjusted candidate resistance value is used as the target resistance value of the impedance balancing resistor Rx. This ensures that the impedance balancing resistor Rx will not fail to effectively balance the static impedance of the photovoltaic inverter 10 due to its resistance value being too large or too small, thus guaranteeing the balancing effect of the impedance balancing resistor Rx on the static impedance of the photovoltaic inverter 10.

[0092] The above are only two feasible implementations of step S42 provided in this embodiment. This embodiment does not specifically limit the specific implementation of step S42.

[0093] For example, to aid in understanding the implementation process of this embodiment combined with the first embodiment described above, a photovoltaic inverter system is used as an example. Figure 4 Taking the structure shown as an example, assume the target voltage value of the first MPPT branch is V1, the target voltage value of the second MPPT branch is V2, and the target voltage value of the third MPPT branch is V3; where the maximum voltage value among V1, V2, and V3 is V1. Then, the voltage deviation value is calculated using the aforementioned Formula 1; subsequently, the candidate resistance value of the impedance balancing resistor Rx is calculated using the aforementioned Formula 2. When both V2 and V3 are zero, the calculated candidate resistance value is used as the target resistance value of the impedance balancing resistor Rx. When neither V2 nor V3 is zero, the candidate resistance value is increased by multiplying it by a preset coefficient value to obtain the target resistance value of the impedance balancing resistor Rx.

[0094] It should be noted that this example is only for the purpose of assisting in understanding this application and does not constitute a limitation on the photovoltaic inverter system of this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0095] Based on the first embodiment described above, a third embodiment of the photovoltaic inverter system of this application is proposed. In the third embodiment, step S40 may include step S43:

[0096] Step S43: Based on the preset mapping relationship between the voltage value, voltage deviation value, resistance value of the voltage divider resistor and resistance value of the impedance balancing resistor, obtain the resistance value of the impedance balancing resistor Rx that corresponds to the first voltage value, voltage deviation value and resistance value of the voltage divider resistor Ra, and use it as the target resistance value of the impedance balancing resistor Rx.

[0097] In one feasible implementation, a relationship table can be used to record the mapping relationship between voltage value, voltage deviation value, resistance value of voltage divider resistor Ra and resistance value of impedance balancing resistor Rx. Thus, step S43 may include: using the first voltage value, voltage deviation value and resistance value of voltage divider resistor Ra as indexes, finding the resistance value of impedance balancing resistor Rx that corresponds to the first voltage value, voltage deviation value and resistance value of voltage divider resistor Ra in a preset relationship table, and using it as the target resistance value of impedance balancing resistor Rx.

[0098] In another feasible implementation, a relationship curve can be used to record the mapping relationship between the voltage value, voltage deviation value, resistance value of the voltage divider resistor and resistance value of the impedance balance resistor Rx. Thus, step S233 may include: inputting the first voltage value, voltage deviation value and resistance value of the voltage divider resistor Ra into the curve function of the preset relationship curve to obtain the target resistance value of the impedance balance resistor Rx.

[0099] It should be noted that, regarding the two feasible implementation methods of step S43 provided above, while the method using a relational table is more efficient, the amount of data that a relational table can record is limited. Therefore, it is only applicable to determining the target resistance value of the impedance balancing resistor Rx for a subset of voltage values, voltage deviation values, and the resistance values ​​of the voltage divider resistors (i.e., the voltage values, voltage deviation values, and resistance values ​​of the voltage divider resistors recorded in the table). While the method using a relational curve is less efficient than that using a relational table, it can record a larger amount of data, thus having a wider range of applications and ensuring the accuracy of the determined target resistance value of the impedance balancing resistor Rx. Therefore, in practical use, users can flexibly choose the method of recording the mapping relationship between voltage values, voltage deviation values, the resistance values ​​of the voltage divider resistors, and the resistance values ​​of the impedance balancing resistors according to their actual needs.

[0100] The above are only two feasible implementations of step S43 provided in this embodiment. This embodiment does not specifically limit the specific implementation of step S43.

[0101] This embodiment can directly determine the target resistance value of the impedance balancing resistor Rx by utilizing the mapping relationship between the preset voltage value, voltage deviation value, resistance value of the voltage divider resistor and resistance value of the impedance balancing resistor. Compared with the method of determining the target resistance value of the impedance balancing resistor Rx by calculation (i.e., the implementation method provided in the second embodiment above), it is more efficient because it does not involve additional intermediate processes (i.e., directly obtaining the target resistance value, rather than first obtaining candidate resistance values ​​and then determining the target resistance value from the candidate resistance values).

[0102] This application also provides a photovoltaic energy storage device, which includes the photovoltaic inverter system provided in the above embodiments. It is understood that since the photovoltaic inverter system is used in the photovoltaic energy storage device, the embodiments of this photovoltaic energy storage device include all the technical solutions of all embodiments of the photovoltaic inverter system, and the achieved technical effects are exactly the same, and will not be repeated here.

[0103] This application also provides an impedance balancing method, applied to the photovoltaic inverter systems provided in the above embodiments. Please refer to... Figure 5 The impedance balancing method may include step S100:

[0104] Step S100: Determine the target resistance value of the impedance balancing resistor of the photovoltaic inverter system based on the input voltage range of each MPPT branch of the photovoltaic inverter system and the resistance value of the voltage divider resistor.

[0105] The impedance balancing method provided in this application, when applied to the photovoltaic inverter systems in the above embodiments, can achieve static impedance balancing of the photovoltaic inverter at low cost without affecting its operating efficiency. Compared with the prior art, the beneficial effects of the impedance balancing method provided in this application are the same as those of the photovoltaic inverter systems provided in the above embodiments, and other technical features of this impedance balancing method are the same as those disclosed in the above embodiments, and will not be repeated here.

[0106] This application also provides a computer-readable storage medium storing a computer program that can run on a processor, the computer program being used to execute the impedance balancing method in the above embodiments.

[0107] The computer-readable storage medium provided in this application embodiment may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems or devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0108] The aforementioned computer-readable storage medium may be included in the impedance balancing system of the photovoltaic inverter; or it may exist independently and not be assembled into the impedance balancing system of the photovoltaic inverter.

[0109] The aforementioned computer-readable storage medium carries one or more programs that, when executed by the impedance balancing system of the photovoltaic inverter, cause the impedance balancing system of the photovoltaic inverter to determine the target resistance value of the impedance balancing resistor based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor.

[0110] Computer program code for performing the operations of this disclosure can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0111] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0112] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0113] The computer-readable storage medium provided in this application embodiment stores computer-readable program instructions for executing the above-described impedance balancing method, enabling low-cost static impedance balancing of the photovoltaic inverter without affecting its operating efficiency. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application embodiment are the same as those of the impedance balancing method provided in the above embodiments, and will not be repeated here.

[0114] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the impedance balancing method described above.

[0115] The computer program product provided in this application can achieve static impedance balance of a photovoltaic inverter at low cost without affecting its operating efficiency. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the impedance balance method provided in the above embodiments, and will not be repeated here.

[0116] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent scope of this application.

Claims

1. A photovoltaic inverter system, characterized in that, The photovoltaic inverter system includes a photovoltaic inverter, MPPT branches connected to the photovoltaic inverter, and an impedance balancing resistor connected between the positive terminal of the busbar of the photovoltaic inverter and the control ground. Each MPPT branch is equipped with a voltage divider resistor. The target resistance value of the impedance balancing resistor is determined based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor.

2. The photovoltaic inverter system as described in claim 1, characterized in that, The step of determining the target resistance value of the impedance balancing resistor based on the input voltage range of each MPPT branch and the resistance value of the voltage divider resistor includes: Obtain the target voltage value determined by each MPPT branch within its respective input voltage range; The maximum voltage value among the target voltage values ​​is taken as the first voltage value, and the remaining target voltage values ​​are taken as the second voltage values. The sum of the voltage differences between the first voltage value and each of the second voltage values ​​is determined to obtain the voltage deviation value; The target resistance value of the impedance balancing resistor is determined based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor.

3. The photovoltaic inverter system as described in claim 2, characterized in that, The step of determining the target resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes: Based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor, the candidate resistance value of the impedance balance resistor is calculated. Based on the candidate resistance values, the target resistance value of the impedance balancing resistor is determined.

4. The photovoltaic inverter system as described in claim 3, characterized in that, The step of determining the target resistance value of the impedance balance resistor based on the candidate resistance values ​​includes: When all of the second voltage values ​​are not zero, the candidate resistance value is taken as the target resistance value of the impedance balancing resistor. When all the second voltage values ​​are zero, the candidate resistance value is increased to obtain the target resistance value of the impedance balance resistor.

5. The photovoltaic inverter system as described in claim 4, characterized in that, The step of increasing the candidate resistance value to obtain the target resistance value of the impedance balance resistor includes: The target resistance value of the impedance balance resistor is obtained by multiplying the candidate resistance value by a preset coefficient value.

6. The photovoltaic inverter system as described in claim 3, characterized in that, The step of determining the target resistance value of the impedance balance resistor based on the candidate resistance values ​​includes: Verify whether the candidate resistance value is within the preset resistance value range; If so, the candidate resistance value is taken as the target resistance value of the impedance balancing resistor; If not, adjust the candidate resistance value and use the adjusted candidate resistance value as the new candidate resistance value, then return to the step of verifying whether the candidate resistance value is within the preset resistance value range.

7. The photovoltaic inverter system as described in claim 3, characterized in that, The step of calculating the candidate resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes: The product of the first voltage value and the resistance value of the voltage divider resistor is calculated, and the ratio of this product to twice the voltage deviation value is used to obtain the candidate resistance value of the impedance balance resistor.

8. The photovoltaic inverter system as described in claim 2, characterized in that, The step of determining the target resistance value of the impedance balancing resistor based on the first voltage value, the voltage deviation value, and the resistance value of the voltage divider resistor includes: Based on the preset mapping relationship between the voltage value, voltage deviation value, resistance value of the voltage divider resistor and resistance value of the impedance balancing resistor, the resistance value of the impedance balancing resistor corresponding to the first voltage value, the voltage deviation value and the resistance value of the voltage divider resistor is obtained, and used as the target resistance value of the impedance balancing resistor.

9. A photovoltaic energy storage device, characterized in that, The photovoltaic energy storage device includes a photovoltaic inverter system as described in any one of claims 1 to 8.

10. An impedance balancing method, characterized in that, Applied to a photovoltaic inverter system as described in any one of claims 1 to 8, the method comprises: Based on the input voltage range of each MPPT branch of the photovoltaic inverter system and the resistance value of the voltage divider resistor, determine the target resistance value of the impedance balance resistor of the photovoltaic inverter system.

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