Photovoltaic off-grid control method and electronic equipment

Abstract

The embodiment of the invention discloses a photovoltaic off-grid control method and electronic equipment. The method comprises the following steps: judging whether the input power of a photovoltaic module is smaller than load power or not; if yes, adjusting the photovoltaic input voltage according to the first preset voltage to control the bus voltage to be stable; if not, the photovoltaic input voltage is tracked and adjusted through the maximum power point so as to improve the input power; and adjusting the output voltage of the inverter according to the second preset voltage so as to reduce the load power. According to the embodiment of the invention, the bus voltage is controlled to be stable when the input power of the photovoltaic module is not less than the load power, the maximum energy is provided through the maximum power point tracking when the input power is less than the load power, and the output voltage of the inverter is reduced to match the input power and the load power, so that the power consumption can be reduced on the basis of not increasing the hardware cost. And maximum utilization of photovoltaic energy is realized.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of photovoltaic systems, and in particular to a photovoltaic off-grid control method and electronic equipment. Background Art

[0002] In recent years, new energy power generation systems represented by photovoltaics and energy storage have developed rapidly. Existing photovoltaic and energy storage off-grid systems are mostly concentrated in the application scenarios of photovoltaic grid-connected, photovoltaic and energy storage grid-connected, and photovoltaic and energy storage off-grid, such as using photovoltaic modules and batteries to supply power to the busbar of the inverter circuit to achieve grid-connected and off-grid applications.

[0003] When a photovoltaic storage and off-grid system is used, considering the high cost of batteries, no batteries are installed, or the batteries are abnormally damaged, when the power grid is cut off, it will not be able to supply power to the key loads of the system. Existing off-grid operation schemes mostly rely on batteries as energy storage media to achieve off-grid operation, and do not consider the off-grid operation strategy under the condition of only photovoltaic modules, so they cannot be applied to scenarios where batteries are not installed or batteries are abnormally damaged. Summary of the invention

[0004] The main technical problem solved by the embodiments of the present invention is to provide a photovoltaic off-grid control method and electronic equipment, which can solve the power supply problem of key loads of the photovoltaic system in the scenario where the battery is not installed or the battery is abnormally damaged.

[0005] In order to solve the above technical problems, a technical solution adopted in an embodiment of the present invention is: to provide a photovoltaic off-grid control method, which is applied to a photovoltaic storage inverter connected to a photovoltaic component and a load, including: judging whether the input power of the photovoltaic component is less than the load power; if not, adjusting the photovoltaic input voltage according to a first preset voltage to control the bus voltage stability; if so, adjusting the photovoltaic input voltage through maximum power point tracking to increase the input power; according to a second preset voltage, adjusting the inverter output voltage to reduce the load power.

[0006] In some embodiments, the determining whether the input power of the photovoltaic component is less than the load power specifically includes: detecting the bus voltage; determining the difference between the bus voltage and the difference between the target bus voltage and a preset threshold; if the bus voltage is greater than the difference between the target bus voltage and the preset threshold, determining that the input power is greater than the load power; if the bus voltage is less than the difference between the target bus voltage and the preset threshold, determining that the input power is less than the load power.

[0007] In some embodiments, the step of adjusting the photovoltaic input voltage according to the first preset voltage includes: obtaining a first inductor current command value according to the difference between the first preset voltage and the current photovoltaic input voltage through an input voltage controller; obtaining a second inductor current command value according to the difference between a target bus voltage and the bus voltage through a bus voltage controller; selecting the smaller value of the first inductor current command value and the second inductor current command value as the final inductor current command value; and obtaining a first control signal according to the final inductor current command value through an inductor current controller to adjust the photovoltaic input voltage.

[0008] In some embodiments, the first preset voltage is the product of an open circuit voltage of the photovoltaic component and a preset coefficient.

[0009] In some embodiments, the step of adjusting the photovoltaic input voltage by maximum power point tracking includes: obtaining a target photovoltaic input voltage by maximum power point tracking; obtaining a first inductor current command value by an input voltage controller according to a difference between the target photovoltaic input voltage and a current photovoltaic input voltage; obtaining a second inductor current command value by a bus voltage controller according to a difference between a target bus voltage and a current bus voltage; selecting a smaller value between the first inductor current command value and the second inductor current command value as a final inductor current command value; and obtaining a first control signal by an inductor current controller according to the final inductor current command value to adjust the photovoltaic input voltage.

[0010] In some embodiments, when performing maximum power point tracking, it also includes: obtaining a target photovoltaic input voltage corresponding to a current maximum power point; and updating the first preset voltage according to the target photovoltaic input voltage.

[0011] In some embodiments, the step of adjusting the inverter output voltage according to the second preset voltage includes: obtaining a bus voltage ratio according to the bus voltage and a preset ratio; selecting a smaller value between the bus voltage ratio and the preset voltage value as the target inverter output voltage; obtaining a second inductor current command value according to the difference between the target inverter output voltage and the current inverter output voltage through an inverter voltage controller; and obtaining a second control signal according to the second inductor current command value through an inductor current controller to adjust the inverter output voltage.

[0012] In some embodiments, if it is a three-phase three-wire inverter, the preset ratio is If it is a three-phase four-wire inverter, the preset ratio is

[0013] To solve the above technical problems, another technical solution adopted in the embodiment of the present invention is: to provide an electronic device, comprising: at least one processor; at least one network interface, the network interface is communicatively connected to the corresponding processor; and a memory communicatively connected to the at least one processor; wherein the network interface is used to establish a communication connection between the processor and other external devices; the memory stores instructions executable by the at least one processor, the instructions are executed by the at least one processor, so that the at least one processor can execute the photovoltaic off-grid control method as described above.

[0014] In order to solve the above technical problems, another technical solution adopted in the embodiment of the present invention is: providing a non-volatile computer storage medium, wherein the computer storage medium stores computer executable instructions, and the computer executable instructions are executed by one or more processors, so that the one or more processors can execute the photovoltaic off-grid control method as described above.

[0015] The beneficial effects of the embodiments of the present invention are as follows: Different from the prior art, the embodiments of the present invention control the bus voltage to be stable when the input power of the photovoltaic module is not less than the load power, provide maximum energy through maximum power point tracking when the input power is less than the load power, and reduce the inverter output voltage to match the input power and the load power, thereby maximizing the utilization of photovoltaic energy without increasing the hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of a photovoltaic energy storage system;

[0017] Figure 2 It is a schematic flow chart of a photovoltaic off-grid control method provided by an embodiment of the present invention;

[0018] Figure 3 yes Figure 2 The schematic diagram of the process of step S100 in the photovoltaic off-grid control method is shown;

[0019] Figure 4 yes Figure 2 The schematic diagram of the process of step S200 in the photovoltaic off-grid control method is shown;

[0020] Figure 5 yes Figure 2 The schematic diagram of the process of step S300 in the photovoltaic off-grid control method is shown;

[0021] Figure 6 is a control block diagram of a photovoltaic converter provided by an embodiment of the present invention;

[0022] Figure 7 yes Figure 2The schematic diagram of the process of step S400 in the photovoltaic off-grid control method is shown;

[0023] Figure 8 is a control block diagram of an inverter provided by an embodiment of the present invention;

[0024] Fig. 9 yes Figure 2 The power-voltage waveform diagram of the photovoltaic off-grid control method shown when the actual MPP point voltage is greater than the target photovoltaic input voltage;

[0025] Fig.10 yes Figure 2 The power-voltage waveform diagram of the photovoltaic off-grid control method shown when the actual MPP point voltage is less than the target photovoltaic input voltage;

[0026] Fig.11 It is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on another element or there can be one or more centered elements therebetween. When an element is described as "connected" to another element, it can be directly connected to another element or there can be one or more centered elements therebetween. The orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "bottom" and the like used in this specification is based on the orientation or positional relationship shown in the accompanying drawings, only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0028] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0029] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0030] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0031] See also Figure 1 , Figure 1 It is a structural schematic diagram of a photovoltaic energy storage system, which includes a photovoltaic energy storage inverter 100, a photovoltaic module 200, a battery group 300 and a key load 400.

[0032] The photovoltaic storage inverter 100 includes a photovoltaic converter 110, an inverter 120, an energy storage converter 130, a control switch S1, and a control switch S2. The DC side of the inverter 120 is connected to one end of the photovoltaic converter 110 and one end of the energy storage converter 130, respectively. The other end of the photovoltaic converter 110 is connected to the photovoltaic module 200, and the other end of the energy storage converter 130 is connected to the battery pack 300. The AC side of the inverter 120 is connected to one end of the control switch S2, and the other end of the control switch S2 is connected to one end of the control switch S1 and the key load 400, respectively. The other end of the control switch S1 is connected to the power grid 20.

[0033] The port connecting the photovoltaic converter 110 and the photovoltaic module 200 is called a photovoltaic interface. In practical applications, the photovoltaic interface can be connected to one or more photovoltaic modules to receive solar energy and convert it into electrical energy. The main function of the photovoltaic converter 110 is to adjust the operating voltage of the photovoltaic module 200 to achieve the best energy conversion efficiency.

[0034] The port connecting the energy storage converter 130 and the battery pack 300 is called a battery interface, which is used to connect the battery pack. In normal application scenarios, the battery pack can store excess photovoltaic energy and provide supplementary power when the light is insufficient.

[0035] The port connecting the control switch S1 and the grid 20 is called the grid interface. The control switch S1 is used to control the grid-connected and off-grid states of the photovoltaic energy storage system. When the grid 20 is normal, the photovoltaic energy storage system can achieve grid-connected operation by closing the control switch S1; when the grid 20 is powered off, the control switch S1 is opened to enter the off-grid mode.

[0036] The port connecting the control switch S2 and the critical load 400 is called a load interface. The control switch S2 is used to control the on-off of power supply to the critical load 400. In the application scenario of the present invention, the critical load 400 is usually a critical electrical device in a residence or building.

[0037] In actual applications, there are the following situations: For example, some users choose not to install batteries because of the high cost of battery packs. Of course, in more cases, it may be because the battery pack fails and cannot be connected to the photovoltaic energy storage system. At this time, the photovoltaic energy storage system can keep the control switch S1 closed for grid-connected operation when the grid is normal, and the grid supplies power to the critical load; however, when the grid is out of power, the critical load loses its power source.

[0038] To solve the above problems, an embodiment of the present invention provides a photovoltaic off-grid control method, which is applied to a photovoltaic storage inverter connected to a photovoltaic module and a load. The flow chart is as follows: Figure 2 As shown, the specific steps include:

[0039] Step S100: determining whether the input power of the photovoltaic module is less than the load power.

[0040] Specifically, the relationship between the input power and load power of the photovoltaic module is monitored in real time. By comparing the two power values, the current working state is determined, and the corresponding control strategy is selected. For example, in the morning or evening when the light is weak, the input power of the photovoltaic module may be less than the load power; while in the midday when the light is sufficient, the input power of the photovoltaic module may be greater than the load power.

[0041] Step S200: adjusting the photovoltaic input voltage according to the first preset voltage to control the bus voltage to be stable.

[0042] When the input power of the photovoltaic module is not less than the load power, since the photovoltaic module can provide sufficient power to meet the load demand, the control focus turns to maintaining the stable operation of the photovoltaic system. By adjusting the photovoltaic input voltage to the first preset voltage, the stability of the bus voltage can be ensured. For example, when there is sufficient sunlight, the photovoltaic input voltage can be controlled at a suitable operating point so that the bus voltage is maintained at a predetermined stable value, providing a stable power input for the load.

[0043] Step S300: adjusting the photovoltaic input voltage through maximum power point tracking to increase the input power.

[0044] When the input power of the photovoltaic module is less than the load power, the power provided by the photovoltaic module is insufficient to meet the load demand, so the maximum power point tracking (MPPT) technology is needed to maximize the output power of the photovoltaic module. For example, in the case of weak light, the photovoltaic input voltage is dynamically adjusted to make the photovoltaic module always work at the maximum power point to obtain the maximum possible output power.

[0045] Step S400: adjusting the inverter output voltage according to the second preset voltage to reduce the load power.

[0046] When the power provided by the photovoltaic module is insufficient to meet the load demand, in order to achieve power balance control, it is also necessary to control the actual power consumption of the load by adjusting the output voltage of the inverter. For example, when the photovoltaic input power is insufficient, by appropriately reducing the inverter output voltage, the power consumption of the load can be reduced accordingly, thereby achieving power balance between the input power and the load power.

[0047] Take a home photovoltaic system as an example. Suppose it is 10 am on a sunny day. At this time, the sunlight is sufficient, the output power of the photovoltaic module is 3000W, and the household power load is 2000W. The system detects that the input power is greater than the load power, and maintains the bus voltage stable to ensure normal power supply. At 4 pm, the sunlight weakens, the photovoltaic output drops to 1500W, and the load is still 2000W. The system detects that the input power is less than the load power, and immediately starts the MPPT to maximize the photovoltaic output. At the same time, it appropriately reduces the inverter output voltage and reduces the load power to ensure the continuous operation of the system.

[0048] In general, the photovoltaic off-grid control method provided in this embodiment achieves efficient operation of the system by dynamically judging the power relationship and adopting different control strategies. When the photovoltaic power is sufficient, the stability of the system is prioritized; when the photovoltaic power is insufficient, the input power is increased through MPPT, and the power is balanced by adjusting the output voltage, ultimately achieving maximum utilization of photovoltaic energy. This method is particularly suitable for photovoltaic storage inverter systems that do not install batteries or have damaged batteries, and can ensure the power supply needs of critical loads without increasing hardware costs.

[0049] In some embodiments of the present application, the flowchart of step S100 is as follows: Figure 3 As shown, the specific steps include:

[0050] Step S110: Detect bus voltage.

[0051] The voltage value of the bus is monitored in real time through the voltage sensor. The bus voltage is an important indicator reflecting the power balance state of the system, and its value change directly reflects the relationship between input power and output power. For example, in a photovoltaic system, when the bus voltage begins to drop, it usually indicates that the input power of the system may not be able to meet the current load demand.

[0052] Step S120: determining the difference between the bus voltage and the difference between the target bus voltage and a preset threshold.

[0053] Specifically, a target bus voltage and a preset threshold are set, and it is determined whether the bus voltage is greater than or less than a difference between the target bus voltage and the preset threshold.

[0054] Step S130: Determine whether the input power is greater than the load power.

[0055] When the detected bus voltage is higher than the target bus voltage minus the preset threshold, it means that the input power provided by the PV module is sufficient to maintain a stable bus voltage, and it is determined that the input power at this time is greater than the load power.

[0056] Step S140: Determine whether the input power is less than the load power.

[0057] When the detected bus voltage is lower than the difference between the target bus voltage and the preset threshold, it means that the power provided by the PV module is insufficient to maintain a stable bus voltage, and it is determined that the input power at this time is less than the load power.

[0058] In general, this embodiment establishes a simple and effective power relationship judgment method through the key parameter of bus voltage. This method does not require additional power detection equipment and can be implemented only by monitoring the bus voltage; it has a fast response speed and can reflect the power balance state of the system in a timely manner; the judgment standard is clear and easy to implement and debug; finally, by setting a preset threshold, a certain margin is provided to avoid frequent switching of the system working mode.

[0059] The working process of this embodiment is described below by using specific examples:

[0060] Assuming that the target bus voltage of a photovoltaic storage inverter system is set to 400V and the preset threshold is 10V, the judgment threshold is 390V. At 9 am, the sunlight is good, and the system detects that the bus voltage is 398V, which is higher than the judgment threshold of 390V. The system determines that the current photovoltaic input power is greater than the load power and continues to maintain stable bus voltage control. At 3 pm, due to cloud cover, the bus voltage dropped to 387V, which is lower than the judgment threshold of 390V. The system immediately determines that the photovoltaic input power is less than the load power and immediately starts the MPPT control strategy.

[0061] It should be noted that the setting of the preset threshold: if the difference is set too large, the power shortage judgment may be entered too early, affecting the efficiency of the photovoltaic system; if the difference is set too small, it may lead to untimely judgment, which will affect the stability of the photovoltaic system; as an example and not a limitation, in the embodiment of the present application, the preset threshold is set to about 10V to achieve a better balance between system response speed and stability.

[0062] In some embodiments of the present application, the flowchart of step S200 is as follows: Figure 4 As shown, the specific steps include:

[0063] Step S210: obtaining a first inductor current command value according to a difference between a first preset voltage and a current photovoltaic input voltage through an input voltage controller.

[0064] In an embodiment of the present application, the first preset voltage is the product of the open circuit voltage of the photovoltaic module and the preset coefficient. As an example and not a limitation, considering that the maximum power point voltage of a common photovoltaic module is about 0.8 times the open circuit voltage, the initial value of the preset coefficient is usually set to 0.8. The photovoltaic input voltage currently sampled is compared with the first preset voltage to obtain an error value; the error value is input into the input voltage controller to calculate the corresponding inductor current command value. For example, if the open circuit voltage of the photovoltaic module is 400V, the first preset voltage is 320V. When the sampled voltage is 310V, the input voltage controller generates an inductor current command value for adjusting the photovoltaic input voltage to the first preset voltage.

[0065] Step S220: obtaining a second inductor current command value according to the difference between the target bus voltage and the bus voltage through a bus voltage controller.

[0066] By monitoring the change of bus voltage, the bus voltage currently sampled is compared with the target bus voltage to obtain the error value; the error value is input into the bus voltage controller to calculate the corresponding inductor current command value. Among them, the target bus voltage is determined by the current photovoltaic input voltage and the inverter output voltage. Taking the three-phase four-wire inverter as an example, in order to ensure that the inverter can work normally, the bus voltage needs to be greater than 2 times the peak value of the inverter output voltage. For example, when the inverter output voltage is 230V (effective value), its peak value is about 325V, so the target bus voltage needs to be set above 650V.

[0067] Step S230: selecting a smaller value between the first inductor current command value and the second inductor current command value as a final inductor current command value.

[0068] In the embodiment of the present application, the smaller value of the first inductor current command value and the second inductor current command value is selected as the final inductor current command value to take into account the control requirements of the photovoltaic input terminal and the bus terminal at the same time. The principle of taking the minimum value is: if a larger current command value is selected, the photovoltaic input voltage may be too low, causing the photovoltaic module to operate at an undesirable operating point. For example, when the first inductor current command value is 10A and the second inductor current command value is 8A, the system will select 8A as the final command value.

[0069] Step S240: obtaining a first control signal according to the final inductor current command value through the inductor current controller to adjust the photovoltaic input voltage.

[0070] The inductor current controller generates a corresponding first control signal, i.e., a PWM control signal, according to the final current command value, so as to adjust the working state of the photovoltaic converter and adjust the photovoltaic input voltage. For example, when the photovoltaic input voltage needs to be increased, the controller will reduce the duty cycle of the PWM signal; when the photovoltaic input voltage needs to be reduced, the duty cycle of the PWM signal will be increased.

[0071] It should be noted that when performing MPPT, it also includes: obtaining the target photovoltaic input voltage corresponding to the current maximum power point; updating the first preset voltage according to the target photovoltaic input voltage. That is, when the photovoltaic converter controls the MPPT, it is necessary to synchronously record the maximum power point voltage and update the preset coefficient. Make the first preset voltage closer to the actual maximum power point voltage.

[0072] In some embodiments of the present application, the flowchart of step S300 is as follows: Figure 5 As shown, the specific steps include:

[0073] Step S310: obtaining a target photovoltaic input voltage through maximum power point tracking.

[0074] The MPPT algorithm calculates the optimal operating voltage point of the photovoltaic module in real time. When the light conditions change, the MPPT algorithm can dynamically adjust to always track the maximum output power point of the photovoltaic module. For example, when the light intensity changes from 800W / m 2 Reduce to 500W / m 2 When the target voltage is adjusted, the MPPT algorithm will adjust the target voltage accordingly to ensure that the PV panels maintain maximum power output under the new environmental conditions.

[0075] Step S320: obtaining a first inductor current command value according to a difference between a target photovoltaic input voltage and a current photovoltaic input voltage through an input voltage controller.

[0076] The input voltage controller compares the target PV input voltage output by the MPPT algorithm with the actual sampled PV input voltage to calculate the required inductor current command value. For example, if the target voltage tracked by the MPPT is 320V and the current PV input voltage is 300V, the controller will generate an appropriate current command value to adjust the PV input voltage to the target PV input voltage.

[0077] Step S330: obtaining a second inductor current command value according to a difference between the target bus voltage and the current bus voltage through a bus voltage controller.

[0078] By monitoring the change of bus voltage, the bus voltage currently sampled is compared with the target bus voltage to obtain the error value; the error value is input into the bus voltage controller to calculate the corresponding inductor current command value. Among them, the target bus voltage is determined by the current photovoltaic input voltage and the inverter output voltage. Taking the three-phase four-wire inverter as an example, in order to ensure that the inverter can work normally, the bus voltage needs to be greater than 2 times the peak value of the inverter output voltage. For example, when the inverter output voltage is 230V (effective value), its peak value is about 325V, so the target bus voltage needs to be set above 650V.

[0079] Step S340: selecting a smaller value between the first inductor current command value and the second inductor current command value as a final inductor current command value.

[0080] The smaller value of the first inductor current command value and the second inductor current command value is selected as the final inductor current command value to ensure that the photovoltaic system can track the maximum power point without causing instability due to excessive current. For example, when the first inductor current command value is 12A and the second inductor current command value is 10A, the system selects 10A as the final command value, which can be as close to the maximum power point as possible while ensuring system stability.

[0081] Step S350: obtaining a first control signal according to the final inductor current command value through the inductor current controller to adjust the photovoltaic input voltage.

[0082] The final current command value is converted into the first control signal, namely the PWM control signal, and the photovoltaic input voltage is controlled by adjusting the on-time of the switch tube. For example, when the photovoltaic input voltage needs to be increased, the controller will reduce the duty cycle of the PWM signal accordingly; when the photovoltaic input voltage needs to be reduced, the duty cycle of the PWM signal is increased.

[0083] The above steps S100 to S300 are all performed in the photovoltaic converter of the photovoltaic storage inverter. Figure 6 The control block diagram of the photovoltaic converter is shown. The photovoltaic converter is composed of three controllers, namely an input voltage controller 111, a bus voltage controller 112 and an inductor current controller 113, and also includes a selection module 114 and a minimum value module 115.

[0084] Among them, PV open The open circuit voltage of the photovoltaic module is multiplied by the preset coefficient Gain and then input into the selection module. pv The input power of the photovoltaic module is input into the selection module 114 after the maximum power point voltage is obtained by the MPPT module. REFis the target photovoltaic input voltage, and is the output of the selection module 114. The selection module 114 selects the output maximum power point voltage or Gain*photovoltaic open circuit voltage according to the following rules.

[0085] PV RBK It is the photovoltaic voltage sampling value, which is used for closed-loop feedback control of photovoltaic input voltage; BUS REF is the target bus voltage, which is determined by the current PV input voltage and off-grid voltage; BUS RBK is the bus voltage sampling value, which is used for the closed-loop feedback control of the bus voltage; I REF is the target inductor current, taking the minimum value of the input voltage controller output and the bus voltage controller output; I RBK is the inductor current sampling value, which is used for closed-loop feedback control of the inductor current.

[0086] According to the above steps S100 to S300, the selection module 114 makes a selection by judging the magnitude of the current voltage and the voltage command. RBK >BUS REF -ΔU, indicating that the current PV module provides enough energy and does not need to perform MPPT. At this time, the PV converter needs to provide a stable bus voltage for the inverter. ΔU is a preset threshold. As an example but not a limitation, ΔU is set to 10V. If BUS RBK <BUS REF -ΔU means that the energy provided by the current PV panels is insufficient and can no longer provide a stable bus voltage for the inverter. MPPT needs to be implemented to provide as much energy as possible.

[0087] In some embodiments of the present application, the flowchart of step S400 is as follows: Figure 7 As shown, the specific steps include:

[0088] Step S410: Obtaining a bus voltage ratio according to the bus voltage and a preset ratio.

[0089] Specifically, the corresponding preset ratio is selected according to the type of inverter. As an example but not limitation, if it is a three-phase three-wire inverter, the preset ratio is If it is a three-phase four-wire inverter, the preset ratio is The bus voltage ratio is obtained by multiplying the current bus voltage by the preset ratio. For example, when the bus voltage is 400V, for a three-phase four-wire inverter system, the bus voltage ratio is

[0090] Step S420: Selecting a smaller value between the bus voltage ratio and the preset voltage value as the target inverter output voltage.

[0091] By comparing the obtained bus voltage ratio with the preset voltage value (usually 230V or 220V AC effective value), the smaller value is selected as the actual inverter output voltage instruction to ensure that the inverter output voltage does not exceed its modulation capability, and when the bus voltage decreases, the load power is reduced by reducing the output voltage.

[0092] For example: when the bus voltage is sufficient (400V), the bus voltage ratio is about 141V, the preset voltage value is 230V, and the system will output 230V AC power; when the bus voltage drops to 350V, the bus voltage ratio is about 124V, and the system will output 124V AC power, thereby reducing the load power.

[0093] Step S430: obtaining a second inductor current command value according to a difference between a target inverter output voltage and a current inverter output voltage through an inverter voltage controller.

[0094] The inverter voltage controller compares the target output voltage with the actual sampled output voltage to calculate the required inductor current command value. The inverter voltage controller needs to consider the characteristics of the AC voltage to achieve accurate control of the voltage amplitude and phase. For example, when the target output voltage is 230V and the current output voltage is 220V, the inverter voltage controller will generate an appropriate current command value to increase the inverter output voltage.

[0095] Step S440: obtaining a second control signal according to the second inductor current command value through the inductor current controller to adjust the inverter output voltage.

[0096] The current command output by the voltage controller is converted into a second control signal, namely the actual PWM control signal. The inductor current controller needs to respond quickly to ensure the stability and waveform quality of the output voltage. For example, when the load changes suddenly, the controller can quickly adjust the duty cycle of the PWM signal to maintain a stable output voltage.

[0097] The above step S400 is performed in the inverter of the photovoltaic energy storage inverter. Figure 8 1 shows a control block diagram of the inverter. The photovoltaic converter is composed of two controller parts, namely an inverter voltage controller 121 and an inductor current controller 122 , and also includes a minimum value module 123 .

[0098] INV REF is the target inverter voltage, is the smaller ratio of the preset voltage value to the bus voltage, and as an example but not a limitation, the preset voltage value is 230V. Taking a single-phase inverter and a three-phase four-wire inverter as an example, it is usually taken When the bus is insufficient, the inverter output voltage is actively reduced to reduce the load power. RBKIL is the sampling value of the inverter voltage, which is used for the closed-loop feedback control of the inverter voltage. REF IL is the target inductor current, and the inverter voltage controller output is taken. RBK is the inductor current sampling value, which is used for closed-loop feedback control of the inductor current.

[0099] In general, when the input power of the photovoltaic module is greater than the load power, the BUS RBK >BUS REF -ΔU, the PV inverter controls the bus voltage to be stable, and the inverter outputs a rated voltage of 220V or 230V. Since the PV inverter does not perform MPPT tracking, in order to prevent transient conditions such as load mutations from causing the PV modules to operate to the left of the maximum power point (MPP), it is necessary to set the PV inverter's PV REF =Gain*open circuit voltage. Its main function is to limit the PV input voltage from falling below the open circuit voltage times Gain, and maintain the PV module running on the right side of the MPP point of the PU curve. At this time, it is also necessary to preset the MPPT module output to Gain*open circuit voltage in advance, and switch to "PV module input power <

[0100] When the load power is “high”, the input power of photovoltaic is smoothly transferred.

[0101] When the input power of the photovoltaic module is less than the load power, the BUS RBK <BUS REF -ΔU, the photovoltaic converter controls MPPT tracking to provide maximum energy, and does not control the bus voltage. Therefore, the inverter needs to appropriately reduce the output voltage according to the current bus voltage to reduce the load power to achieve a balance between the input power and load power of the photovoltaic module. When controlling MPPT, the photovoltaic converter needs to synchronously record the voltage at the maximum power point and update the Gain value. Make Gain*PV open Closer to the actual maximum power point voltage of the current string.

[0102] Considering that the MPP voltage of a photovoltaic module is not necessarily 0.8 times the open circuit voltage, Fig. 9 The photovoltaic off-grid control method provided by this application shows that the voltage at the real MPP point is greater than the PV REF Voltage adaptability when .

[0103] Point A: Steady-state operating point at P1 load power

[0104] Point B: Steady-state operating point at P2 load power

[0105] Point C: Unstable operating point at P2 load power

[0106] Point D: PV REF Operating point under limit

[0107] Point M: The maximum power operating point of the photovoltaic module curve

[0108] Depend on Fig. 9 It can be seen that when the load is running at point A, it is "the input power of the PV module> the load power condition". When the load suddenly increases from P1 power to P2 power, the PV converter may transfer from point A to point B for stable operation. If the transient change is faster, the PV converter may pass through the maximum power point M from point A and continue to the left to point C. From a simple stability analysis, it can be seen that point C is an unstable operating point: when the energy extracted by the PV converter increases, the voltage at the PV module port becomes lower, point C moves to the left, and the energy that can be provided decreases. In order to stabilize the bus, the PV converter will extract more energy, forming a positive feedback. Therefore, point C will continue to move left to point D. Due to the PV REF The PV converter will remain operating at point D.

[0109] However, at this time, the input power that the photovoltaic module can provide at point D is less than the load power P2, and the bus voltage will gradually decrease until BUS RBK <BUS REF -ΔU, switched to "PV panel input power < load power condition", the PV panel starts MPPT tracking and climbs from point D to point C again, and in the process PV REF The limit value will also change from the voltage at point D to the voltage at point C, making Gain*PV open Closer to the actual maximum power point voltage of the current string.

[0110] Fig.10 The photovoltaic off-grid control method provided by this application shows that the voltage at the actual MPP point is less than Gain*PV open Voltage adaptability when .

[0111] Point A: Steady-state operating point at P1 load power

[0112] Point B: PV REF Operating point under limit

[0113] Point C: Stable operating point at P2 load power

[0114] Point M: The maximum power operating point of the photovoltaic module curve

[0115] Depend on Fig.10It can be seen that when the load is running at point A, it is the "input power of the PV module> load power condition". When the load suddenly increases from P1 power to P2 power, the PV converter will transfer from point A to point C. If the actual MPP point voltage is less than Gain*PVopen, the inverter will be limited to operate at point B. The input power that the PV module can provide at point B is less than the load power P2, and the bus voltage will gradually decrease and switch to the "input power of the PV module< load power condition". The PV module starts MPPT tracking and climbs from point B to point C, and updates PV REF is the voltage at point C.

[0116] After multiple changes in load characteristics, the inverter can adapt to the PV curves of different PV modules, and when the load is large, the PV converter can operate at the MPP point.

[0117] Different from the prior art, the implementation mode of the present invention controls the bus voltage to be stable when the input power of the photovoltaic module is not less than the load power, provides maximum energy through MPPT when the input power is less than the load power, and reduces the inverter output voltage to match the input power and load power. It can maximize the utilization of photovoltaic energy without increasing hardware costs.

[0118] The embodiment of the present invention also provides an electronic device based on the above photovoltaic off-grid control method, and its structural schematic diagram is as follows: Fig.11 As shown, the electronic device 500 includes:

[0119] One or more processors 501, network interface 502 and memory 503, Fig.11 In the figure, a processor 501, a network interface 502 and a memory 503 are taken as an example.

[0120] The network interface 502 is in communication with the corresponding processor 501, and the processor 501 and the memory 502 can be connected via a bus or other means. Fig.11 The example of connecting through bus is taken in the following.

[0121] The network interface 502 is used to establish a communication connection between the processor 501 and other external devices, including the following types: RJ-45 interface, SC optical fiber interface, AUI interface, FDDI interface, Console interface and other interface types.

[0122] The memory 503 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs, non-volatile computer executable programs and modules. The processor 501 executes various functional applications and data processing of the electronic device by running the non-volatile software programs, instructions and units stored in the memory 503, that is, the photovoltaic off-grid control method of the above method embodiment is implemented.

[0123] The memory 503 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the electronic device, etc. In addition, the memory 503 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 503 may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the electronic device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0124] The one or more units are stored in the memory 503, and when executed by one or more processors, perform the photovoltaic off-grid control method in any of the above method embodiments, for example, perform the above described Figure 2 The method comprises steps S100 to S400.

[0125] The above electronic device can execute the photovoltaic off-grid control method provided by the embodiment of the present invention, and has the corresponding program modules and beneficial effects of the execution method. For technical details not fully described in the electronic device embodiment, please refer to the photovoltaic off-grid control method provided by the embodiment of the present invention.

[0126] The embodiment of the present invention further provides a non-volatile computer-readable storage medium, which may be included in the device described in the above embodiment; or may exist independently without being assembled into the device. The above non-volatile computer-readable storage medium carries one or more programs, and when the above one or more programs are executed, the photovoltaic off-grid control method of the embodiment of the present disclosure is implemented.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present application as above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A photovoltaic off-grid control method, applied to a photovoltaic storage inverter connected to a photovoltaic module and a load, characterized in that: include: Determining whether the input power of the photovoltaic module is less than the load power; If not, adjusting the photovoltaic input voltage according to the first preset voltage to control the bus voltage to be stable; If so, adjusting the photovoltaic input voltage by maximum power point tracking to increase the input power; According to the second preset voltage, the inverter output voltage is adjusted to reduce the load power.

2. The method according to claim 1, characterized in that The determining whether the input power of the photovoltaic module is less than the load power specifically includes: detecting the bus voltage; Determining the difference between the bus voltage and a target bus voltage and a preset threshold value; If the bus voltage is greater than the difference between the target bus voltage and the preset threshold, it is determined that the input power is greater than the load power; If the bus voltage is less than the difference between the target bus voltage and the preset threshold, it is determined that the input power is less than the load power.

3. The method according to claim 1, characterized in that The step of adjusting the photovoltaic input voltage according to the first preset voltage comprises: Obtaining a first inductor current command value according to a difference between the first preset voltage and the current photovoltaic input voltage through an input voltage controller; Obtaining a second inductor current command value according to a difference between a target bus voltage and the bus voltage by a bus voltage controller; selecting a smaller value between the first inductor current command value and the second inductor current command value as a final inductor current command value; A first control signal is obtained through an inductor current controller according to the final inductor current command value to adjust the photovoltaic input voltage.

4. The method according to claim 3, characterized in that The first preset voltage is the product of the open circuit voltage of the photovoltaic module and a preset coefficient.

5. The method according to claim 1, characterized in that The step of adjusting the photovoltaic input voltage by maximum power point tracking comprises: The target photovoltaic input voltage is obtained through maximum power point tracking; Obtaining a first inductor current command value according to a difference between the target photovoltaic input voltage and the current photovoltaic input voltage through an input voltage controller; Obtaining a second inductor current command value according to a difference between a target bus voltage and a current bus voltage through a bus voltage controller; selecting a smaller value between the first inductor current command value and the second inductor current command value as a final inductor current command value; A first control signal is obtained through an inductor current controller according to the final inductor current command value to adjust the photovoltaic input voltage.

6. The method according to claim 5, characterized in that When performing maximum power point tracking, it also includes: Get the target photovoltaic input voltage corresponding to the current maximum power point; The first preset voltage is updated according to the target photovoltaic input voltage.

7. The method according to claim 1, characterized in that The step of adjusting the inverter output voltage according to the second preset voltage comprises: Obtaining a bus voltage ratio according to the bus voltage and a preset ratio; Selecting a smaller value between the bus voltage ratio and a preset voltage value as a target inverter output voltage; Obtaining a second inductor current command value according to a difference between the target inverter output voltage and the current inverter output voltage by means of an inverter voltage controller; A second control signal is obtained through an inductor current controller according to the second inductor current command value to adjust the inverter output voltage.

8. The method according to claim 7, characterized in that If it is a three-phase three-wire inverter, the preset ratio is If it is a three-phase four-wire inverter, the preset ratio is 9. An electronic device, characterized in that: include: at least one processor; at least one network interface, the network interface being communicatively connected to a corresponding processor; as well as, a memory communicatively connected to the at least one processor; wherein, The network interface is used to establish a communication connection between the processor and other external devices; The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the photovoltaic off-grid control method according to any one of claims 1 to 8.

10. A non-volatile computer storage medium, characterized in that: The computer storage medium stores computer executable instructions, which are executed by one or more processors, so that the one or more processors can execute the photovoltaic off-grid control method according to any one of claims 1 to 8.

Images