String type inverter circuit and photovoltaic power generation equipment

Abstract

The utility model relates to the technical field of photovoltaic power generation, and discloses a string type inverter circuit and photovoltaic power generation equipment, and the string type inverter circuit comprises a first switch sub-circuit, a second switch sub-circuit, a photovoltaic assembly, an inverter and a time control switch. The first switch sub-circuit is connected in series into the main loop, the second switch sub-circuit is connected in series into the bypass, and the time control switch is connected with the second switch sub-circuit; when the photovoltaic module is merged into the inverter for normal operation, the first switch sub-circuit is closed, the second switch sub-circuit is disconnected, and the current generated by the photovoltaic module enters the inverter for inversion; when a peak clipping alarm signal exists, the first switch sub-circuit is disconnected, the second switch sub-circuit is closed, and the time control switch is closed to charge the load. According to the utility model, the main loop and the bypass can be rapidly switched, the inverter does not need to be started and stopped, the abandoned electric energy is utilized to the greatest extent, the effect of increasing power generation is achieved, and the problem that the abandoned electric energy is not utilized in time and is wasted is solved.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic power generation technology, specifically to a string inverter circuit and photovoltaic power generation equipment. Background Technology

[0002] Peak shaving is a crucial function in photovoltaic (PV) power generation systems. When PV modules generate high output power under favorable sunlight conditions, if transmission and distribution equipment such as inverters, transformer substations, and power lines cannot withstand such peak power, it can lead to insulation damage and reduced lifespan. Therefore, PV inverters possess peak shaving capabilities, enabling them to monitor system output power in real time and automatically reduce output power when necessary to meet grid capacity and maintain system stability, while also mitigating technical curtailment of solar power.

[0003] If this discarded electricity is not utilized in time, it will be wasted. How to store the discarded electricity to improve the power generation effect of photovoltaic power generation equipment is an urgent problem to be solved. Utility Model Content

[0004] In view of this, the present invention provides a string inverter circuit and photovoltaic power generation equipment to solve the problem of wasted electrical energy due to untimely utilization.

[0005] In a first aspect, this utility model provides a string inverter circuit, which includes: a first switching sub-circuit, a second switching sub-circuit, a photovoltaic module, an inverter, and a time control switch;

[0006] The first switch sub-circuit is connected in series to the main circuit, the second switch sub-circuit is connected in series to the bypass, and the time control switch is connected to the second switch sub-circuit.

[0007] When the photovoltaic module is connected to the inverter and is operating normally, the first switch sub-circuit is closed and the second switch sub-circuit is open, and the current generated by the photovoltaic module enters the inverter for inversion; when there is a peak clipping alarm signal, the first switch sub-circuit is open, the second switch sub-circuit is closed, and the time control switch is closed to charge the load.

[0008] This utility model provides a string inverter circuit. When photovoltaic modules are connected in parallel with the inverter and the inverter is operating normally, the first switch sub-circuit is closed and the second switch sub-circuit is open, allowing the current generated by the photovoltaic modules to enter the inverter for inversion. When a peak clipping alarm signal is detected, the first switch sub-circuit is opened, the second switch sub-circuit is closed, and the time control switch is closed, enabling rapid switching between the main circuit and the bypass circuit. The inverter does not need to be started or stopped, maximizing the utilization of wasted solar energy. During periods of strong sunlight, the energy wasted during the peak clipping period of the string inverter is stored. During periods of poor sunlight, the stored energy is used to light supplementary lamps to illuminate the back, thereby increasing power generation and solving the problem of wasted energy due to untimely utilization.

[0009] In one optional implementation, the first switch sub-circuit is a time-delayed opening and time-delayed closing circuit breaker, which is a normally closed circuit breaker; the second switch sub-circuit is a time-delayed closing and time-delayed opening circuit breaker, which is a normally open circuit breaker; the normally closed circuit breaker is connected in series to the main circuit, and the normally open circuit breaker is connected in series to the bypass.

[0010] In one optional implementation, one end of the normally closed circuit breaker is connected to the positive terminal of the photovoltaic module and the positive terminal of the inverter, respectively, and the other end of the normally closed circuit breaker is connected to the negative terminal of the photovoltaic module and the negative terminal of the inverter, respectively.

[0011] One end of the normally open circuit breaker is connected to the positive terminal of the photovoltaic module, one end of the load, and one end of the time control switch, respectively. The other end of the normally open circuit breaker is connected to the negative terminal of the photovoltaic module, the other end of the load, and the other end of the time control switch, respectively. This utility model provides a string inverter circuit where the normally open and normally closed circuit breakers enable rapid switching between the main circuit and the bypass circuit, eliminating the need for inverter start-up and shutdown, and maximizing the utilization of wasted solar energy.

[0012] In one optional implementation, both the first and second switch sub-circuits are electrical bypasses. When the photovoltaic module is connected to the inverter, the positive terminal of the electrical bypass is connected in series to the main circuit, and the negative terminal of the electrical bypass is connected in series to the bypass.

[0013] In one optional implementation, the positive terminal of the electrical bypass is connected to the positive terminal of the photovoltaic module, the positive terminal of the inverter, one end of the load, and one end of the time control switch, respectively, and the negative terminal of the electrical bypass is connected to the negative terminal of the photovoltaic module, the negative terminal of the inverter, the other end of the load, and the other end of the time control switch, respectively.

[0014] This utility model provides a string inverter circuit that uses electrical bypass, requiring fewer additional devices in the circuit, resulting in stable operation and lower investment.

[0015] In one optional implementation, the first switch sub-circuit is a first disconnect switch, and the second switch sub-circuit is a second disconnect switch;

[0016] When photovoltaic modules are connected to the inverter, the first disconnecting switch is connected in series to the main circuit, and the second disconnecting switch is connected in series to the bypass.

[0017] In one optional implementation, the first terminal of the first disconnecting switch is connected to the positive terminal of the photovoltaic module, the second terminal of the first disconnecting switch is connected to the positive terminal of the inverter, and the third terminal of the first disconnecting switch is connected to one end of the load and one end of the time control switch.

[0018] The first terminal of the second disconnect switch is connected to the negative terminal of the photovoltaic module, the second terminal of the second disconnect switch is connected to the negative terminal of the inverter, and the third terminal of the second disconnect switch is connected to the other terminal of the load and the other terminal of the time control switch.

[0019] In one alternative implementation, both the first disconnecting switch and the second disconnecting switch are single-pole double-throw switches.

[0020] This utility model provides a string inverter circuit with a simple isolating switch structure, relatively stable operation, no damage to inverters and other equipment, and low cost.

[0021] In one alternative implementation, the circuit further includes a voltage divider resistor, a charging resistor, and a supplementary lamp light source, with the load being a battery.

[0022] One end of the fill light source is connected to the other end of the time control switch, and the other end of the fill light source is connected to the other end of the charging resistor.

[0023] One end of the voltage divider resistor is connected to the negative terminal of the second switch sub-circuit, and the other end of the voltage divider resistor is connected to one end of the charging resistor;

[0024] One end of the battery is connected to the positive terminal of the second switch sub-circuit and one end of the time control switch, while the other end of the battery is connected to the other end of the charging resistor and the other end of the supplementary lamp light source.

[0025] Fourthly, this utility model provides a photovoltaic power generation device, including the string inverter circuit of the first aspect or any corresponding embodiment described above. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a string inverter circuit according to an embodiment of the present utility model;

[0028] Figure 2 This is a schematic diagram of another set of string inverter circuits according to an embodiment of the present utility model;

[0029] Figure 3 This is a schematic diagram of the structure of another set of string inverter circuits according to an embodiment of the present utility model;

[0030] Figure 4 This is a schematic diagram of another set of string inverter circuits according to an embodiment of the present utility model. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0032] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0034] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0035] Photovoltaic inverters have peak shaving capabilities, enabling them to monitor system output power in real time and automatically reduce output power when necessary to meet grid capacity and maintain system stability, while also preventing technical curtailment of solar power.

[0036] During months with higher temperatures and abundant sunlight, string inverters are prone to peak-shaving operation between 11:00 AM and 1:00 PM. This invention provides a string inverter circuit that utilizes the characteristic of monocrystalline silicon bifacial double-glass modules that can generate electricity from both sides. During periods of strong sunlight, the energy discarded by the string inverter during peak-shaving is stored. During periods of weak sunlight, the stored energy is used to power the back side of the inverter, thereby increasing power generation.

[0037] This embodiment provides a string inverter circuit. Figure 1 This is a structural diagram of a string inverter circuit according to an embodiment of the present invention, as shown below. Figure 1 As shown, the circuit includes: a first switching sub-circuit 11, a second switching sub-circuit 12, a photovoltaic module 13, an inverter 14, and a time control switch 15. The first switching sub-circuit 11 is connected in series to the main circuit, the second switching sub-circuit 12 is connected in series to the bypass, and the time control switch 15 is connected to the second switching sub-circuit 12. When the photovoltaic module 13 is connected in parallel with the inverter and is operating normally, the first switching sub-circuit 11 is closed, the second switching sub-circuit 12 is open, and the current generated by the photovoltaic module 13 enters the inverter 14 for inversion. When there is a peak clipping alarm signal, the first switching sub-circuit 11 is open, the second switching sub-circuit 12 is closed, and the time control switch 15 is closed to charge the load 18. Multiple photovoltaic modules are connected in series to form a photovoltaic string. The inverter uses a prototype inverter, and the photovoltaic modules are made of monocrystalline silicon bifacial double-glass modules. The time control switch is a KG316T time control switch.

[0038] In one alternative implementation, such as Figure 2 As shown, the string inverter circuit also includes a voltage divider resistor 16, a charging resistor 17, and a supplementary lamp light source 19. The load 18 is a battery. One end of the supplementary lamp light source 19 is connected to the other end of the time control switch 15, and the other end of the supplementary lamp light source 19 is connected to the other end of the charging resistor 17. One end of the voltage divider resistor 16 is connected to the negative terminal of the second switch sub-circuit 12, and the other end of the voltage divider resistor 16 is connected to one end of the charging resistor 17. One end of the battery is connected to the positive terminal of the second switch sub-circuit 12 and one end of the time control switch 15, and the other end of the battery is connected to the other end of the charging resistor 17 and the other end of the supplementary lamp light source 19.

[0039] The first switching sub-circuit is a time-delayed opening and time-delayed closing circuit breaker A, which is a normally closed circuit breaker 111; the second switching sub-circuit is a time-delayed closing and time-delayed opening circuit breaker B, which is a normally open circuit breaker 112. One end of the normally closed circuit breaker is connected to the positive terminal of the photovoltaic module and the positive terminal of the inverter, respectively, and the other end of the normally closed circuit breaker is connected to the negative terminal of the photovoltaic module and the negative terminal of the inverter, respectively. One end of the normally open circuit breaker is connected to the positive terminal of the photovoltaic module, one end of the load, and one end of the time control switch, respectively, and the other end of the normally open circuit breaker is connected to the negative terminal of the photovoltaic module, the other end of the load, and the other end of the time control switch, respectively.

[0040] For example, such as Figure 2 As shown, a pair of interlocking circuit breakers A and B are installed before the last photovoltaic string is connected to the inverter. Circuit breaker A is connected in series to the main circuit including the photovoltaic modules and the inverter, and circuit breaker B is connected to the bypass outside the main circuit. When the prototype inverter is running normally, circuit breaker A is closed and circuit breaker B is open; during peak shaving alarm periods (e.g., from 11:00 to 13:00), circuit breaker B is closed and circuit breaker A is open. Figure 2 Circuit breaker A installed in the main circuit is a time-delayed tripping and time-delayed closing circuit breaker, normally closed, meaning it is closed during normal operation. The timer starts when the sample inverter triggers a peak-shaving alarm and disconnects after ten minutes of continuous alarm. Circuit breaker B installed in the bypass circuit is a time-delayed closing and time-delayed tripping circuit breaker, normally open, meaning it is open during normal operation. The timer starts when the sample inverter triggers a peak-shaving alarm and closes after ten minutes of continuous alarm. Because the main circuit uses circuit breakers with arc-extinguishing capabilities, there is no need to start or stop the inverter. The bypass circuit has a time-controlled switch that opens between 6:00 and 7:00 AM and between 5:00 and 6:00 PM daily, activating the bypass and turning on the supplementary lighting. This uses stored electrical energy to illuminate the back of the lamps, thereby increasing power generation.

[0041] This embodiment provides a string inverter circuit. When the photovoltaic module is connected in parallel with the inverter and the inverter is operating normally, the first switch sub-circuit is closed and the second switch sub-circuit is open, and the current generated by the photovoltaic module enters the inverter for inversion. When there is a peak clipping alarm signal, the first switch sub-circuit is open and the second switch sub-circuit is closed, and the time control switch is closed. The main circuit and bypass can be switched quickly without starting and stopping the inverter. This maximizes the utilization of wasted solar energy and solves the problem of wasted energy due to untimely utilization. It enables the storage of energy wasted during peak clipping periods of the string inverter during periods of strong sunlight, and the use of the stored energy to light up the back of the lamp during periods of poor sunlight, thereby increasing the power generation effect.

[0042] This embodiment also provides a string inverter circuit, such as Figure 3 As shown, Figure 3This is a structural diagram of a string inverter circuit according to an embodiment of the present invention. In this circuit, both the first and second switching sub-circuits are electrical bypasses 113. When the photovoltaic modules are connected in parallel to the inverter, the positive terminal of the electrical bypass is connected in series to the main circuit, and the negative terminal of the electrical bypass is connected in series to the bypass. The remaining structure is the same as... Figure 2 The structures shown are the same, so they will not be described again here.

[0043] In one optional implementation, the positive terminal of the electrical bypass is connected to the positive terminal of the photovoltaic module, the positive terminal of the inverter, one end of the load, and one end of the time control switch, respectively; the negative terminal of the electrical bypass is connected to the negative terminal of the photovoltaic module, the negative terminal of the inverter, the other end of the load, and the other end of the time control switch, respectively. The electrical bypass is a permanent electrical bypass.

[0044] A permanent electrical bypass is installed at the connection point of the last string connected to the inverter, which naturally diverts current during peak shaving periods. During normal operation, the current generated by the photovoltaic modules mainly flows through the main circuit and directly enters the inverter for inversion. When a peak shaving alarm occurs, if the main circuit is blocked or obstructed, the current generated by the photovoltaic modules flows through the bypass, turning on the supplementary lamps. The stored electrical energy is used to illuminate the back of the supplementary lamps and charge the batteries.

[0045] This embodiment also provides a string inverter circuit, such as Figure 4 As shown, Figure 4 This is a structural diagram of a string inverter circuit according to an embodiment of the present invention. The first switching sub-circuit is a first isolating switch 114, and the second switching sub-circuit is a second isolating switch 115. When the photovoltaic modules are connected in parallel to the inverter, the first isolating switch is connected in series in the main circuit, and the second isolating switch is connected in series in the bypass circuit. The remaining structure is the same as... Figure 2 and Figure 3 The structures shown are the same, so they will not be described again here.

[0046] In one alternative implementation, such as Figure 4 As shown, the first terminal of the first disconnecting switch is connected to the positive terminal of the photovoltaic module, and the second terminal of the first disconnecting switch is connected to the positive terminal of the inverter; the third terminal of the first disconnecting switch is connected to one end of the load and one end of the time control switch respectively; the first terminal of the second disconnecting switch is connected to the negative terminal of the photovoltaic module, the second terminal of the second disconnecting switch is connected to the negative terminal of the inverter, and the third terminal of the second disconnecting switch is connected to the other end of the load and the other end of the time control switch respectively.

[0047] For example, based on a photovoltaic power station prototype (20 branches), a bypass for curtailed solar power is constructed. The maximum DC receiving power is 225.7 kW, and the maximum operating power of the inverter is 200 kW. Therefore, only one photovoltaic string (11.5 kW) needs to be introduced into the bypass to achieve the reuse of curtailed solar power without significantly affecting the normal power generation operation of the inverter. Using the existing functions of the inverter monitoring system, with minor adjustments to the program logic, when the prototype inverter monitoring system alarms for peak shaving and the alarm continues for a 10-minute delay, a shutdown command is issued to other inverter systems. After shutdown, an isolating switch is used to switch the last-stage string from the main circuit (normal power generation) to the bypass energy storage. After the bypass switching is completed, the startup procedure is executed. When the prototype inverter alarms and the peak shaving resets, and there is no change after a 10-minute delay, a command to shut down the entire inverter is issued. After shutdown, the last photovoltaic string is switched from the bypass energy storage to the main circuit (normal power generation). After the bypass switching is completed, the startup procedure is executed. The above functions are executed only once a day.

[0048] In months with higher temperatures and abundant sunlight, peak-shaving operation of the photovoltaic string inverter is likely to occur between 11:00 AM and 1:00 PM. When peak-shaving occurs on the prototype unit and the monitoring system detects a continuous signal for ten minutes, an automatic switching command can be issued to switch to the energy storage circuit. A time-controlled switch is connected to the battery, which is turned on daily between 6:00 AM and 7:00 AM and between 5:00 PM and 6:00 PM to activate the bypass and supplemental lighting. During these times, leveraging the ability of both sides of the monocrystalline silicon bifacial double-glass module to generate electricity, supplemental lighting is applied to the back of the photovoltaic panels to enhance illumination and increase power generation. In photovoltaic power generation systems, peak-shaving results in energy waste. When there is sufficient sunlight and high output power is generated, the string inverter circuit provided in this embodiment utilizes this wasted energy, indirectly increasing power generation.

[0049] As one or more specific application embodiments of this utility model, the implementation method of the string inverter circuit provided by this utility model will be further described in detail with reference to a certain project, as follows:

[0050] Table 1 below shows the statistics of inverter start-up and shutdown energy losses during peak shaving periods for a certain project:

[0051] Table 1. Statistics of power loss during inverter start-up and shutdown during peak shaving periods.

[0052]

[0053] Based on the calculations in Table 1 above, each inverter loses 6 kWh of electrical energy during start-up and shutdown.

[0054] The main technical parameters of the inverter equipment and the specific peak shaving process are as follows:

[0055] Photovoltaic module model: Monocrystalline silicon bifacial double-glass module; Rated power: 445W; Photovoltaic string composition: Composed of 26 photovoltaic modules connected in series; Inverter manufacturer: Huawei Technologies Co., Ltd.; Model: SUN2000-196KTL-H0.

[0056] A typical setup has 20 photovoltaic strings (including Y-connections) connected to the DC side, each with a rated power of 445W × 26 = 11.6kW, for a total DC power of 11.6 × 20 = 232kW. Based on an AC / DC capacity ratio of 1.15, when the AC irradiance is very good and the total available DC power exceeds 196kW, the inverter will activate its peak-shaving function. The actual operating power will be between 196-200kW, the operating temperature will not exceed 55℃, and the peak-shaving period will last 1 to 1.5 hours. Three inverters with the same DC-side access capacity but different installation locations were selected as references. Equipment operation data from the start to the end of peak-shaving alarms during midday in July and August were statistically analyzed. The theoretical DC-side power was calculated based on the rated power of the modules and considering attenuation factors. According to the module procurement technical agreement for a certain project, the power attenuation of monocrystalline silicon modules in the first year is ≤2%, and the annual attenuation after the first year is <0.45%. The project was first connected to the grid in May 2021, and the statistical data was collected in July 2023. Therefore, based on the module power, the formula is 445 × (1 - 2.45%) = 434 W; 434 × 26 × 20 = 225.7 kW. The statistics of curtailed solar power during peak-shaving periods are shown in Table 2 below.

[0057] Table 2 Statistics on Curtailed Solar Energy During Peak Shaving Periods

[0058]

[0059] According to Table 2 above, the energy consumed during inverter start-up and shutdown is less than the energy that can be stored during peak shaving.

[0060] In addition, the remaining equipment parameters in the string inverter circuit are shown in Table 3 below:

[0061] Table 3 Other Equipment Parameters

[0062]

[0063] The string inverter circuit provided in this embodiment generates an average of 29 kWh of wasted solar power per inverter on a sunny summer day. Therefore, a 30 kWh battery is selected. Taking advantage of the characteristic that the monocrystalline silicon bifacial double-glass module can generate electricity from both sides, the power wasted during the peak shaving period of the string inverter is stored during the period of strong sunlight (11:00-13:00). During the period of poor sunlight (6:00-7:00, 17:00-18:00), the stored power is used to light up the back side of the light source, thereby achieving the effect of increasing power generation.

[0064] This utility model embodiment also provides a photovoltaic power generation device, including the above-described... Figures 1 to 4 The string inverter circuit shown is shown.

[0065] The further functional descriptions of each component in the above string inverter circuit are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0066] Although embodiments of the present 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 present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A string inverter circuit, comprising: The group string inverter circuit comprises a first switch sub-circuit, a second switch sub-circuit, a photovoltaic module, an inverter and a time control switch; The first switch sub-circuit is connected in series in a main loop, and the second switch sub-circuit is connected in series in a bypass circuit, and the time control switch is connected with the second switch sub-circuit; When the photovoltaic module is connected to the inverter, the first switch sub-circuit is closed, the second switch sub-circuit is opened, and the current generated by the photovoltaic module enters the inverter for inversion; when there is a peak clipping alarm signal, the first switch sub-circuit is opened, the second switch sub-circuit is closed, and the time control switch is closed for charging the load.

2. The string inverter circuit of claim 1, wherein, The first switch sub-circuit is a time-delay opening and closing circuit breaker, which is a normally closed circuit breaker; the second switch sub-circuit is a time-delay closing and opening circuit breaker, which is a normally open circuit breaker; The normally closed circuit breaker is connected in series in the main loop, and the normally open circuit breaker is connected in series in the bypass circuit.

3. The string inverter circuit of claim 2, wherein, One end of the normally closed circuit breaker is connected with the positive pole of the photovoltaic module and the positive pole of the inverter respectively, and the other end of the normally closed circuit breaker is connected with the negative pole of the photovoltaic module and the negative pole of the inverter respectively; One end of the normally open circuit breaker is connected with the positive pole of the photovoltaic module, one end of the load and one end of the time control switch respectively, and the other end of the normally open circuit breaker is connected with the negative pole of the photovoltaic module, the other end of the load and the other end of the time control switch respectively.

4. The string inverter circuit of claim 1, wherein, The first switch sub-circuit and the second switch sub-circuit are both electrical bypasses, and when the photovoltaic module is connected to the inverter, the positive pole of the electrical bypass is connected in series in the main loop, and the negative pole of the electrical bypass is connected in series in the bypass circuit.

5. The string inverter circuit of claim 4, wherein, The positive pole of the electrical bypass is connected with the positive pole of the photovoltaic module, the positive pole of the inverter, one end of the load and one end of the time control switch respectively, and the negative pole of the electrical bypass is connected with the negative pole of the photovoltaic module, the negative pole of the inverter, the other end of the load and the other end of the time control switch respectively.

6. The string inverter circuit of claim 1, wherein, The first switch sub-circuit is a first disconnecting switch, and the second switch sub-circuit is a second disconnecting switch; When the photovoltaic module is connected to the inverter, the first disconnecting switch is connected in series in the main loop, and the second disconnecting switch is connected in series in the bypass circuit.

7. The string inverter circuit of claim 6, wherein, The first end of the first disconnecting switch is connected with the positive pole of the photovoltaic module, the second end of the first disconnecting switch is connected with the positive pole of the inverter, the third end of the first disconnecting switch is connected with one end of the load and one end of the time control switch respectively; The first end of the second disconnecting switch is connected with the negative pole of the photovoltaic module, the second end of the second disconnecting switch is connected with the negative pole of the inverter, and the third end of the second disconnecting switch is connected with the other end of the load and the other end of the time control switch respectively.

8. The string inverter circuit of claim 7, wherein, The first disconnecting switch and the second disconnecting switch are both single-pole double-throw switches.

9. The string inverter circuit of claim 1, wherein, The circuit further comprises a voltage dividing resistor, a charging resistor and a supplementary light source, and the load is a storage battery; One end of the supplementary light source is connected with the other end of the time control switch, and the other end of the supplementary light source is connected with the other end of the charging resistor; One end of the voltage dividing resistor is connected with the negative pole of the second switch sub-circuit, and the other end of the voltage dividing resistor is connected with one end of the charging resistor. One end of the battery is connected to one end of the second switch sub-circuit positive electrode and the time control switch, and the other end of the battery is connected to the other end of the charging resistor and the other end of the light source of the supplementary lamp, respectively.

10. A photovoltaic power plant, characterized by An inverter circuit comprising a string as claimed in any one of claims 1 to 9.

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