Insulation impedance detection method of photovoltaic inverter and photovoltaic inverter
Patent Information
- Application Number
- CN202611156687.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-31
- Publication Date
- 2026-10-09
AI Technical Summary
[0003]有鉴于此，本发明提供了一种光伏逆变器的绝缘阻抗检测方法及光伏逆变器，以解决现有技术中绝缘检测无法区分具体故障MPPT支路的问题
[0003]有鉴于此，本发明提供了一种光伏逆变器的绝缘阻抗检测方法及光伏逆变器，以解决现有技术中绝缘检测无法区分具体故障MPPT支路的问题。
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Figure CN122882816A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic grid-connected inverter technology, specifically to an insulation impedance detection method for photovoltaic inverters and a photovoltaic inverter. Background Technology
[0002] With the increasing demand for cost reduction and efficiency improvement in photovoltaic systems, modern inverters generally adopt multi-MPPT (Maximum Power Point Tracking) designs to improve power generation efficiency and reduce mismatch losses. The number of MPPT channels is typically two or more. However, the traditional unbalanced bridge method can only calculate the total insulation impedance after all MPPT branches are connected in parallel. When an abnormally low total impedance is detected, this method cannot further distinguish which specific MPPT branch the fault originates from. In actual operation and maintenance scenarios, on-site personnel can only check each photovoltaic string one by one, resulting in low location efficiency, time-consuming and labor-intensive operations, significantly increasing operation and maintenance costs and difficulty. Even more disadvantageous is that during fault diagnosis, to avoid equipment damage, the inverter is usually in a state of complete shutdown protection, forcing other MPPT branches that could be generating power normally to stop working, causing unnecessary power generation losses and reducing the overall economic benefits of the system. Summary of the Invention
[0003] In view of this, the present invention provides an insulation impedance detection method for a photovoltaic inverter and a photovoltaic inverter, so as to solve the problem that the insulation detection in the prior art cannot distinguish the specific fault MPPT branch.
[0004] In a first aspect, the present invention provides an insulation impedance detection method for a photovoltaic inverter, applicable to a photovoltaic inverter containing multiple MPPT branches. Each MPPT branch is equipped with a controllable switch, and a switching switch and a disturbance resistor are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground. A voltage divider sampling resistor is connected between the negative terminal bus of the PV side and ground. The method includes: opening the switching switch to obtain a first voltage of the negative terminal bus of the PV side to ground; closing the switching switch to obtain a second voltage of the negative terminal bus of the PV side to ground; calculating the total insulation impedance of all MPPT branches to ground based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor; opening the switching switch and controlling the switching transistor of the target MPPT branch to conduct, and obtaining a third voltage of the negative terminal bus of the PV side to ground; calculating the insulation impedance value of the positive terminal bus of the target MPPT branch to ground based on the total insulation impedance, the third voltage, and the positive terminal bus voltage of the target MPPT branch.
[0005] The method provided by this invention can calculate the insulation resistance value of the positive terminal to ground of any MPPT branch by performing three voltage detections and one short-circuit control of the switching transistor. Compared with the traditional unbalanced bridge method, which can only detect the overall insulation resistance of the PV side, this method can accurately locate the MPPT branch with abnormal insulation resistance. On-site maintenance personnel can quickly locate the fault without checking all strings one by one, greatly reducing the difficulty and time cost of maintenance. At the same time, since the faulty branch can be accurately identified, only the branch needs to be disconnected, and the other normal MPPT branches of the inverter can continue to generate electricity by grid connection, avoiding the power generation loss caused by the shutdown of the entire unit and improving the power generation efficiency and reliability of the system.
[0006] In one optional implementation, the process of calculating the total insulation impedance of all MPPT branches to ground based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor includes: obtaining the positive bus voltage of each MPPT branch and selecting the maximum value among them; calculating the total admittance of all MPPT branches to ground based on the first voltage, the second voltage, the resistance value of the disturbance resistor, the resistance value of the voltage divider sampling resistor, and the maximum value; and calculating the total insulation impedance of all MPPT branches to ground based on the total admittance.
[0007] In one alternative implementation, the total admittance to ground for all MPPT branches is calculated using the following formula:
[0008] Where Y is the total admittance to ground of all MPPT branches; v 01 The first voltage; v 02 This is the second voltage; v1~v n Rs is the positive bus voltage from the first MPPT branch to the nth MPPT branch; Rs is the resistance value of the disturbance resistor; Rq is the resistance value of the voltage divider sampling resistor.
[0009] In one optional implementation, the process of calculating the insulation resistance value of the positive bus of the target MPPT branch to ground based on the total insulation resistance, the third voltage, and the positive bus voltage of the target MPPT branch includes: obtaining the positive bus voltage of the target MPPT branch; and calculating the insulation resistance value of the positive bus of the target MPPT branch to ground based on the total insulation resistance, the difference between the first voltage and the third voltage, the positive bus voltage of the target MPPT branch, and the resistance value of the voltage divider sampling resistor.
[0010] In one optional implementation, the insulation resistance value of the target MPPT branch positive busbar to ground is calculated using the following formula:
[0011] Where i = 1, 2, ..., n, n is the total number of MPPT branches; Ri v is the insulation resistance value of the positive busbar of the i-th MPPT branch to ground; i v is the positive bus voltage of the i-th MPPT branch; 01 The first voltage; v 03 Y is the third voltage; Y is the total admittance to ground of all MPPT branches; R q This is the resistance value of the voltage divider sampling resistor.
[0012] In one alternative implementation, when the switch of the target MPPT branch is turned on, the positive bus of the target MPPT branch is short-circuited to a reference potential, which is ground potential or zero potential.
[0013] In one alternative implementation, the duration of the switching action of the switching switch, the sampling duration of the first voltage, the second voltage, and the third voltage are all less than the switching cycle of the photovoltaic inverter.
[0014] In a second aspect, the present invention provides a photovoltaic inverter, comprising: multiple MPPT branches, a switching switch, a disturbance resistor, a voltage divider sampling resistor, a voltage sampling unit, and a control unit, wherein each MPPT branch is provided with a controllable switching transistor; the switching switch and the disturbance resistor are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground; the voltage divider sampling resistor is connected between the negative terminal bus of the PV side and ground; the voltage sampling unit is used to acquire the voltage of the negative terminal bus of the PV side to ground and the voltage of the positive terminal bus of each MPPT branch; the control unit is connected to the switching switch, each controllable switching transistor, and the voltage sampling unit, and the control unit is used to execute the method as described in the first aspect or any corresponding embodiment thereof.
[0015] Thirdly, the present invention provides an electronic device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the method described in the first aspect or any corresponding embodiment thereof.
[0016] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the method described in the first aspect or any corresponding embodiment thereof. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of the insulation impedance detection principle of a photovoltaic system according to an embodiment of the present invention; Figure 2 This is a schematic flowchart of an insulation impedance detection method for a photovoltaic inverter according to an embodiment of the present invention; Figure 3 This is a specific circuit diagram of a photovoltaic inverter according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.
[0021] This embodiment provides a method for detecting the insulation impedance of a photovoltaic inverter, applicable to photovoltaic inverters containing multiple MPPT branches, such as... Figure 1 As shown, each MPPT branch is equipped with a controllable switch (Q1~Qn), and a switching switch S and a disturbance resistor R are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground. s A voltage-dividing sampling resistor R is connected between the negative busbar on the PV side and ground. q The positive input of the first MPPT branch is denoted as PV1+, the voltage of this branch is denoted as V1, the insulation resistance between its positive terminal and ground is denoted as R1, and the insulation resistance between its negative terminal and ground is denoted as R2; the positive input of the nth MPPT branch is denoted as PVn+, and the voltage of this branch is denoted as V... n Its positive electrode insulation resistance to ground is denoted as R. 2n-1 The insulation resistance of the negative terminal to ground is denoted as R. 2n The insulation detection circuit consists of the original disturbance resistor R in the photovoltaic inverter. s and voltage divider sampling resistor R q Composition, R s It is connected in series with switch S and then connected between the positive terminal Vout of the busbar and ground PE.
[0022] like Figure 2 As shown, the method includes: Step S1: Disconnect the switching switch and obtain the first voltage of the negative busbar on the PV side to ground.
[0023] Specifically, when the switching switch S is disconnected, the disturbance resistor R... s Insulation detection circuit not connected. In this state, the voltage between the PV side negative busbar and ground PE is detected to obtain the first voltage v. 01 This voltage reflects the initial electrical state of the circuit when no known impedance disturbance is applied.
[0024] Step S2: Close the switching switch to obtain the second voltage between the negative busbar on the PV side and ground.
[0025] Specifically, closing the switching switch S will change the disturbance resistor R. s Connect the insulation detection circuit between the PV-side positive busbar and ground PE. At this time, due to R s When the circuit is connected, the electrical parameters of the insulation detection circuit change, and the voltage between the negative busbar on the PV side and the PE ground changes accordingly. This voltage is detected under these conditions to obtain the second voltage v. 02 .
[0026] Step S3: Calculate the total insulation impedance of all MPPT branches to ground based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor.
[0027] The process of calculating the total insulation impedance to ground of all MPPT branches based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor includes: Step S31: Obtain the positive bus voltage of each MPPT branch and select the maximum value.
[0028] Specifically, in step S1, the switching switch S is opened, and the disturbance resistor R... s Without the insulation detection circuit connected, the voltage between the negative busbar on the PV side and ground PE is V. 01 The current flowing from the positive terminal of each MPPT branch to the negative busbar on the PV side through its respective positive insulation resistance is equal to the current flowing from the negative busbar on the PV side through the insulation resistance of each branch's negative terminal and the voltage divider sampling resistor R. q The current flowing to ground (PE). Based on this, the following node current equations are established: (1) Expanding equation (1) by the voltage term, we get V 01 Moving the term to the right side of the equation and rearranging, we obtain the following equation: (2) When the switching switch S is closed, the disturbance resistor R sWhen connected between the positive busbar on the PV side and ground PE, the voltage between the negative busbar on the PV side and ground PE becomes v. 02 Because of R s With the addition of the connection, an additional line was added to the insulation detection circuit via the positive busbar on the PV side and R. s The current branch flowing to ground PE has a current max(v1,…,v). n )-v 02 ) / R s Where max(v1,…,v n ) is the maximum value among all MPPT branch positive bus voltages, representing the highest potential of the PV side positive bus.
[0029] Step S32: Calculate the total admittance of all MPPT branches to ground based on the first voltage, the second voltage, the resistance value of the disturbance resistor, the resistance value of the voltage divider sampling resistor, and the maximum value of the positive bus voltage of the MPPT branch.
[0030] Therefore, the following node current equations are established: (3) Expanding equation (3) by the voltage term and rearranging, we get the following equation: (4) Subtracting equation (2) from equation (4), the first to nth terms on the left side of the equation (i.e., the positive electrode insulation resistance terms of each branch) cancel each other out, leaving R. s Branch current term; the right side of the equation is V 02 With V 01 The difference multiplied by the sum of the reciprocals of all insulation resistances and 1 / R q After eliminating duplicate terms, we obtain the sum of the reciprocals of the parallel values of the insulation resistances of all positive and negative terminals in all MPPT branches. The formula for calculating the total admittance to ground for all MPPT branches is as follows: (5) Where Y is the total admittance to ground of all MPPT branches; v 01 The first voltage; v 02 This is the second voltage; v1~v n Rs is the positive bus voltage from the first MPPT branch to the nth MPPT branch; Rs is the resistance of the disturbance resistor; Rn is the positive bus voltage from the first MPPT branch to the nth MPPT branch. q This is the resistance value of the voltage divider sampling resistor.
[0031] Step S33: Calculate the total insulation impedance to ground of all MPPT branches based on the total admittance.
[0032] Specifically, due to the total insulation resistance R total It is the reciprocal of the total ampere Y.
[0033] Step S4: Disconnect the switching switch, control the switching transistor of the target MPPT branch to turn on, and obtain the third voltage of the negative busbar on the PV side to ground.
[0034] When the switch of the target MPPT branch is turned on, the positive bus of the target MPPT branch is short-circuited to the reference potential, which is ground potential or zero potential. The duration of the switching action of the switching switch, and the sampling duration of the first voltage, second voltage, and third voltage are all integer multiples of the switching cycle of the photovoltaic inverter.
[0035] Specifically, after calculating the total insulation impedance to ground of all MPPT branches, it is necessary to test each individual branch in order to further pinpoint which specific MPPT branch has an insulation abnormality.
[0036] First, disconnect the switching switch S to make the disturbance resistor R s No insulation detection circuit is connected. Then, the i-th (1≤i≤n) MPPT branch is used as the target branch, and the Boost switch Qi of this branch is controlled to turn on. After Qi turns on, the PV+ positive bus of this branch is short-circuited to the reference potential (ground potential or zero potential) through the turned-on switch. Since the photovoltaic string has current source characteristics and the Qi conduction time is extremely short (such as several inverter switching cycles), the switch can fully withstand the losses caused by the current source and will not damage the device.
[0037] In this state, since the positive bus voltage of the i-th MPPT branch is forced to become the reference potential (approximately 0V), while the positive bus voltages of other MPPT branches can be considered constant within a very short detection time, the current distribution in the insulation detection circuit undergoes a change relevant only to this target branch. At this time, the voltage between the negative bus on the PV side and ground PE is acquired to obtain the third voltage v. 03 .
[0038] It should be noted that the selection of the "target MPPT branch" in this step is flexible. Operators can arbitrarily specify a branch for testing based on actual needs (such as historical fault information, system alarm signals, or operation and maintenance experience), or they can test all branches one by one in sequence until all MPPT branches are tested.
[0039] Step S5: Calculate the insulation resistance value of the positive bus of the target MPPT branch to ground based on the total insulation resistance, the third voltage, and the positive bus voltage of the target MPPT branch.
[0040] Specifically, using the third voltage v of the negative busbar on the PV side to ground obtained in step S4 when the target branch is short-circuited. 03 Combined with the first voltage v 01Total admittance Y and the positive bus voltage v of the target branch itself. i The insulation resistance value R of the positive terminal of the target branch to ground was calculated. i .
[0041] The process of calculating the insulation resistance value of the positive busbar of the target MPPT branch to ground based on the total insulation resistance, the third voltage, and the positive busbar voltage of the target MPPT branch includes: Step S51: Obtain the positive bus voltage of the target MPPT branch.
[0042] Step S52: Calculate the insulation impedance value of the positive bus of the target MPPT branch to ground based on the total insulation impedance, the difference between the first voltage and the third voltage, the positive bus voltage of the target MPPT branch, and the resistance value of the voltage divider sampling resistor.
[0043] Taking the i-th MPPT branch as the target branch as an example, its positive bus voltage is v. i The insulation resistance of the positive terminal to ground is R. i When Qi is on, v i It is short-circuited to the reference potential of 0V. According to Kirchhoff's current law, the following node current equation can be established: (6) Assuming the first path is the target MPPT branch, the positive bus voltage v1 of the first MPPT branch is short-circuited to the reference potential of 0V. Substituting v1=0, we can obtain the following equation after simplification: (7) After sorting, we can obtain: (8) By rearranging equation (8), we can obtain the calculation formula for the insulation impedance value R1 of the positive busbar to ground of the first MPPT branch, namely equation (9): (9) Therefore, for any i-th target MPPT branch, it is only necessary to control Qi to conduct according to formula (9) so that the positive bus voltage v of the i-th MPPT branch is... i =0V, and thus the calculation formula for the insulation impedance value of the positive busbar of the i-th target MPPT branch to ground is derived as follows: (10) Where i = 1, 2, ..., n, n is the total number of MPPT branches; R i v is the insulation resistance value of the positive busbar of the i-th MPPT branch to ground; i Let R be the positive bus voltage of the i-th MPPT branch (calculate R). iSubstituting this into step S1, after the switching switch S is opened, the detected branch voltage is recorded as V. i ); v 01 The first voltage; v 03 Y is the third voltage; Y is the total admittance to ground of all MPPT branches; R q This is the resistance value of the voltage divider sampling resistor.
[0044] It should be noted that all parameters in the above formula are known quantities or have been obtained through the aforementioned steps, except for R. i Since it is an unknown quantity, it can be solved directly. When the calculated R... i When the resistance is below a preset safety threshold, the target MPPT branch is determined to have an insulation impedance abnormality; when R i If the insulation level is above or equal to the safety threshold, the branch is considered to have normal insulation. Depending on actual maintenance needs, selective testing can be performed on any one or all MPPT branches.
[0045] The method provided in this embodiment can calculate the insulation resistance value of the positive terminal to ground of any MPPT branch by performing three voltage detections and one short-circuit control of the switching transistor. Compared with the traditional unbalanced bridge method, which can only detect the overall insulation resistance of the PV side, this method can accurately locate the MPPT branch with abnormal insulation resistance. On-site maintenance personnel can quickly locate the fault without checking all strings one by one, greatly reducing the difficulty and time cost of maintenance. At the same time, since the faulty branch can be accurately identified, only the branch needs to be disconnected, and the other normal MPPT branches of the inverter can continue to generate electricity by grid connection, avoiding the power generation loss caused by the shutdown of the entire unit and improving the power generation efficiency and reliability of the system.
[0046] This embodiment provides a photovoltaic inverter, such as... Figure 3 As shown, it includes: multiple MPPT branches, a switching switch S, a disturbance resistor Rs, a voltage divider sampling resistor Rq, a voltage sampling unit, and a control unit (not shown in the figure). Each MPPT branch is equipped with a controllable switch (Q1~Qn). The switching switch S and the disturbance resistor Rs are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground. The voltage divider sampling resistor Rq is connected between the negative bus on the PV side and ground. The voltage sampling unit is used to obtain the voltage of the negative bus on the PV side to ground PE and the positive bus voltages v1~v of each MPPT branch. n The control unit is connected to the switching switch S, each controllable switch (Q1~Qn) and the voltage sampling unit. The control unit is used to execute the method as described in the above embodiments.
[0047] Specifically, Figure 3In this circuit, the controllable switching transistor is a power semiconductor switching device, which can be a MOSFET or an IGBT. Its gate is controlled by the PWM signal output by the control unit and is used to realize the boost conversion and short-circuit control in the insulation impedance detection of this invention. The switching switch S is controlled by the control unit to turn on or off. When S is closed, the perturbation resistor Rs is connected to the loop between the positive bus of the PV side and the ground PE, providing a perturbation impedance with a known resistance value for insulation detection; when S is open, the perturbation resistor Rs is disconnected from the loop. One end of Rq is connected to the negative bus of the PV side, and the other end is grounded to PE, providing a fixed impedance path to ground for the negative bus of the PV side. It is also a voltage divider element for the voltage sampling unit to obtain the voltage of the negative bus of the PV side to ground.
[0048] Specifically, the control unit controls the opening and closing of the switching switch S by outputting a control signal, controls the conduction and turn-off of each controllable switch by outputting a PWM drive signal, and obtains each voltage value by reading the sampling data of the voltage sampling unit. Then, it calculates the total insulation impedance and the insulation impedance value of the positive terminal of each MPPT branch to ground according to the above calculation method.
[0049] It should be noted that the photovoltaic inverter can be a single-phase inverter or a three-phase inverter, and its DC input side includes at least one MPPT branch. The Boost circuit can be a traditional two-level Boost circuit or a three-level Boost circuit; both topologies are suitable for the insulation impedance detection method of this invention. The positive buses of each MPPT branch are connected inside the inverter to form the positive DC bus of the inverter, and the negative buses of each MPPT branch are connected inside the inverter to form the negative bus on the PV side (which can also be called the negative DC bus of the inverter). By controlling the switching of the switching switch S and the disturbance resistor Rs, and in conjunction with the Boost switching transistors Q1~Qn of each MPPT branch, independent detection of the insulation impedance of the positive terminal to ground of each MPPT branch is achieved. No additional power devices are required, effectively reducing hardware costs, while improving the accuracy of fault location and maintenance efficiency.
[0050] The photovoltaic inverter provided in this embodiment of the invention can execute the method provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the various modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.
[0051] Figure 4 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention.
[0052] The following is a detailed reference. Figure 4The diagram illustrates a structural schematic suitable for implementing an electronic device according to embodiments of the present invention. The electronic device may include a processor (e.g., a central processing unit, graphics processor, etc.) 001, which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 002 or a program loaded from memory 008 into random access memory (RAM) 003. The RAM 003 also stores various programs and data required for the operation of the electronic device. The processor 001, ROM 002, and RAM 003 are interconnected via bus 004. An input / output (I / O) interface 005 is also connected to bus 004.
[0053] Typically, the following devices can be connected to I / O interface 005: input devices 006 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 007 including, for example, liquid crystal displays (RCDs), speakers, vibrators, etc.; memory devices 008 including, for example, magnetic tapes, hard disks, etc.; and communication devices 009. Communication device 009 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 4 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown, and more or fewer devices may be implemented or have instead.
[0054] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication device 009, or installed from memory 008, or installed from ROM 002. When the computer program is executed by processor 001, it performs the functions defined in the methods of the embodiments of the present invention.
[0055] Figure 4 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.
[0056] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.
[0057] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.
[0058] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. A method for detecting the insulation impedance of a photovoltaic inverter, characterized in that, The method is applied to a photovoltaic inverter containing multiple MPPT branches, each MPPT branch is equipped with a controllable switch, a switching switch and a disturbance resistor are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground, and a voltage divider sampling resistor is connected between the negative terminal bus of the PV side and ground. Disconnect the switching switch and obtain the first voltage of the PV side negative bus to ground; By closing the switching switch, the second voltage between the negative busbar on the PV side and ground is obtained; Calculate the total insulation impedance to ground of all MPPT branches based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor. After disconnecting the switching switch and controlling the switching transistor of the target MPPT branch to turn on, the third voltage of the negative busbar on the PV side to ground is obtained. Based on the total insulation impedance, the third voltage, and the positive bus voltage of the target MPPT branch, calculate the insulation impedance value of the positive bus of the target MPPT branch to ground.
2. The method according to claim 1, characterized in that, The process of calculating the total insulation impedance to ground of all MPPT branches based on the first voltage, the second voltage, the resistance value of the disturbance resistor, and the resistance value of the voltage divider sampling resistor includes: Obtain the positive bus voltage of each MPPT branch and select the maximum value among them; Calculate the total admittance to ground of all MPPT branches based on the first voltage, the second voltage, the resistance value of the disturbance resistor, the resistance value of the voltage divider sampling resistor, and the maximum value. Calculate the total insulation impedance to ground of all MPPT branches based on the total admittance.
3. The method according to claim 2, characterized in that, The formula for calculating the total admittance to ground of all MPPT branches is as follows: Where Y is the total admittance to ground of all MPPT branches; v 01 The first voltage; v 02 This is the second voltage; v1~v n Rs is the positive bus voltage from the first MPPT branch to the nth MPPT branch; Rs is the resistance value of the disturbance resistor; Rq is the resistance value of the voltage divider sampling resistor.
4. The method according to claim 1, characterized in that, The process of calculating the insulation resistance value of the positive busbar of the target MPPT branch to ground based on the total insulation resistance, the third voltage, and the positive busbar voltage of the target MPPT branch includes: Obtain the positive bus voltage of the target MPPT branch; Based on the total insulation impedance, the difference between the first voltage and the third voltage, the positive bus voltage of the target MPPT branch, and the resistance value of the voltage divider sampling resistor, the insulation impedance value of the positive bus of the target MPPT branch to ground is calculated.
5. The method according to claim 4, characterized in that, The formula for calculating the insulation resistance value of the target MPPT branch positive busbar to ground is as follows: Where i = 1, 2, ..., n, n is the total number of MPPT branches; R i v is the insulation resistance value of the positive busbar of the i-th MPPT branch to ground; i v is the positive bus voltage of the i-th MPPT branch; 01 The first voltage; v 03 Y is the third voltage; Y is the total admittance to ground of all MPPT branches; R q This is the resistance value of the voltage divider sampling resistor.
6. The method according to claim 1, characterized in that, When the switch of the target MPPT branch is turned on, the positive bus of the target MPPT branch is short-circuited to the reference potential, which is ground potential or zero potential.
7. The method according to claim 1, characterized in that, The duration of the switching action of the switching switch, the sampling duration of the first voltage, the second voltage, and the third voltage are all integer multiples of the switching cycle of the photovoltaic inverter.
8. A photovoltaic inverter, characterized in that, include: Multi-channel MPPT branch, switching switch, disturbance resistor, voltage divider sampling resistor, voltage sampling unit and control unit, among which, Each MPPT branch is equipped with a controllable switch. The switching switch and the disturbance resistor are connected in series between the positive terminal of the DC bus output of each MPPT branch and ground; The voltage divider sampling resistor is connected between the negative busbar on the PV side and ground; The voltage sampling unit is used to obtain the voltage of the negative busbar on the PV side to ground and the voltage of the positive busbar of each MPPT branch. The control unit is connected to the switching switch, each of the controllable switching transistors and the voltage sampling unit, and the control unit is used to perform the method as described in any one of claims 1 to 7.
9. An electronic device, characterized in that, include: A memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, the processor executing the computer instructions to perform the method of any one of claims 1 to 7.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the method of any one of claims 1 to 7.