Limited power control method of photovoltaic microgrid inverter system and optical storage inverter

Abstract

The invention relates to a limited power control method of a photovoltaic micro-grid inverter system and an optical storage inverter. The method comprises the following steps: acquiring the current charging power of a battery, and judging whether the current charging power is greater than the maximum charging power of the battery or not; if yes, calculating a power difference value between the maximum charging power and the current charging power, and when the power difference value is smaller than zero, reducing second power generation energy generated by the optical storage inverter and first power generation energy generated by the photovoltaic grid-connected module according to the power difference value, therefore, the power difference value between the maximum charging power of the battery and the current charging power is controlled to be smaller than a set range, so that accurate and rapid limited power adjustment of the optical storage inverter and the photovoltaic grid-connected module can be realized without communication between the optical storage inverter and the photovoltaic inverter, and stable charging of the battery is realized.

Description

Technical Field

[0001] The present application relates to the field of inverter technology, and in particular to a power limiting control method for a photovoltaic microgrid inverter system and a photovoltaic storage inverter. Background Art

[0002] With the development of inverters, photovoltaic inverters with energy storage and photovoltaic inverters can work in the form of microgrids. When the power grid is working normally, that is, when there is city power, photovoltaic inverters and photovoltaic inverters with energy storage are both connected to the grid and can independently control their output power generation energy to power the connected batteries or loads. However, when there is no city power, photovoltaic inverters and photovoltaic inverters with energy storage need to communicate through communication equipment to ensure that the microgrid can work normally. The way of controlling the communication between the two through communication equipment takes a long time to react. If the output power of the photovoltaic inverter and photovoltaic inverter is too large, it is easy to cause damage to the battery or load in a short time. Summary of the invention

[0003] Based on this, it is necessary to provide a power limiting control method for a photovoltaic microgrid inverter system and a photovoltaic storage inverter to achieve accurate and efficient power limiting adjustment of the photovoltaic microgrid inverter system and stable and efficient charging of the battery.

[0004] In a first aspect, a power limiting control method for a photovoltaic microgrid inverter system is provided, wherein the photovoltaic microgrid inverter system includes a photovoltaic storage inverter, a photovoltaic grid-connected module composed of multiple photovoltaic inverters, and a battery, wherein the first power generation energy generated by the photovoltaic grid-connected module flows to the photovoltaic storage inverter through an AC bus, and the photovoltaic storage inverter charges the battery based on the second power generation energy generated by itself and the first power generation energy, and is applied to the photovoltaic storage inverter, and the method includes:

[0005] Obtaining a current charging power of the battery, and determining whether the current charging power is greater than a maximum charging power of the battery;

[0006] If so, the power difference between the maximum charging power and the current charging power is calculated. When the power difference is less than zero, the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module are reduced according to the power difference, so as to control the power difference between the maximum charging power and the current charging power of the battery to be less than the set range.

[0007] In one embodiment, the photovoltaic storage inverter is connected to a first photovoltaic panel, the first photovoltaic panel is used to convert light energy into electrical energy of the photovoltaic storage inverter, the photovoltaic storage inverter includes a BOOST circuit, and the BOOST circuit is used to boost the output voltage of the first photovoltaic panel to an input voltage that can be used by the photovoltaic storage inverter; the reducing the second power generation energy generated by the photovoltaic storage inverter itself according to the power difference includes:

[0008] Determine whether the BOOST circuit is in an enabled state;

[0009] If yes, the power difference is input into the PI regulator to adaptively generate the maximum reference current of the battery;

[0010] Obtaining the maximum charging current currently allowed by the battery;

[0011] The current difference between the maximum reference current and the maximum charging current is calculated, and the current difference is used as the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation, thereby adjusting the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

[0012] In one embodiment, the photovoltaic storage inverter further includes a BUCK-BOOST circuit, and the BUCK-BOOST circuit is used to convert the second power generation energy of the photovoltaic storage inverter into a charging voltage that can be connected to the battery; and reducing the second power generation energy generated by the photovoltaic storage inverter itself according to the power difference also includes:

[0013] Determine whether the BOOST circuit is in an enabled state;

[0014] If not, the power difference is input into a PI regulator to adaptively generate a maximum reference current for the battery;

[0015] The maximum reference current is used as the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation, thereby adjusting the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

[0016] In one embodiment, reducing the first power generation energy generated by the photovoltaic grid-connected module includes:

[0017] When the power difference is less than zero, calculating an overfrequency load reduction value of the photovoltaic grid-connected module;

[0018] Obtaining the current AC frequency of the AC bus;

[0019] The overfrequency load reduction value is cyclically summed with the current AC frequency, and a first AC frequency is obtained according to each summation, and the first power generation energy generated by the photovoltaic grid-connected module is controlled to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

[0020] In one embodiment, the method further comprises:

[0021] When the power difference is greater than or equal to zero, calculating an overfrequency load reduction value of the photovoltaic grid-connected module;

[0022] Obtaining the current AC frequency of the AC bus;

[0023] The overfrequency load reduction value is cyclically subtracted from the current AC frequency, and a second AC frequency is obtained based on each subtraction. The first power generation energy generated by the photovoltaic grid-connected module is controlled to gradually increase until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

[0024] In one embodiment, the calculating the overfrequency load reduction value of the photovoltaic grid-connected module includes:

[0025]

[0026] Among them, F1 is the frequency of the start load reduction point in the overfrequency load reduction curve, F2 is the frequency of the overfrequency load reduction curve at which the power is reduced to the minimum power, and Tr is the load reduction response time.

[0027] In one embodiment, the method further comprises:

[0028] Set a constant power limit threshold;

[0029] Determine whether the power difference between the maximum charging power and the current charging power is greater than the power limit constant threshold; if so, set the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation to the maximum rated value of the BOOST circuit, or set the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation to the minimum rated value of the BUCK-BOOST circuit.

[0030] In one embodiment, the photovoltaic grid-connected module and the battery are also connected to a load module, and the method further includes:

[0031] Obtaining the load power when the load module is running;

[0032] If the growth rate of the load power exceeds a set threshold after reducing the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module, the maximum limit value of the reference current when the BOOST circuit performs current inner-loop regulation is set to the maximum rated value of the BOOST circuit, or the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner-loop regulation is set to the minimum rated value of the BUCK-BOOST circuit.

[0033] In a second aspect, a photovoltaic power storage inverter is provided, the photovoltaic power storage inverter comprising a control unit, the control unit being used to implement the steps corresponding to the method described in the first aspect above.

[0034] In a third aspect, a photovoltaic microgrid inverter system is provided, the system comprising a photovoltaic storage inverter, a photovoltaic grid-connected module composed of a plurality of photovoltaic inverters, and a battery, the first power generation energy generated by the photovoltaic grid-connected module flows to the photovoltaic storage inverter through an AC bus, the photovoltaic storage inverter charges the battery based on the second power generation energy generated by itself and the first power generation energy, and the photovoltaic storage inverter is used to:

[0035] Obtaining a current charging power of the battery, and determining whether the current charging power is greater than a maximum charging power of the battery;

[0036] If so, the power difference between the maximum charging power and the current charging power is calculated. When the power difference is less than zero, the second power generation energy generated by the photovoltaic storage inverter itself and the first power generation energy generated by the photovoltaic grid-connected module are reduced according to the power difference; thereby controlling the power difference between the maximum charging power and the current charging power of the battery to be less than the set range.

[0037] The power limiting control method of the photovoltaic microgrid inverter system and the photovoltaic storage inverter above obtain the current charging power of the battery to determine whether the current charging power is greater than the maximum charging power of the battery; if so, the power difference between the maximum charging power and the current charging power is calculated, and when the power difference is less than zero, the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module are reduced according to the power difference, thereby controlling the power difference between the maximum charging power and the current charging power of the battery to be less than a set range, so that accurate and rapid power limiting adjustment of the photovoltaic storage inverter itself and the photovoltaic grid-connected module can be achieved without communication between the photovoltaic storage inverter and the photovoltaic inverter, thereby achieving stable charging of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 A photovoltaic microgrid inverter system according to an embodiment;

[0040] Figure 2 A power limiting control method for a photovoltaic microgrid inverter system according to an embodiment;

[0041] Figure 3 A schematic diagram of a process for reducing the second power generation energy generated by the photovoltaic storage inverter itself according to an embodiment;

[0042] Figure 4 A schematic diagram of a process for reducing the second power generation energy generated by the photovoltaic storage inverter itself according to another embodiment;

[0043] Figure 5 A schematic diagram of a process for reducing the first power generation energy generated by the photovoltaic grid-connected module according to an embodiment;

[0044] Figure 6 A schematic diagram of a process of reducing the first power generation energy generated by the photovoltaic grid-connected module according to another embodiment. DETAILED DESCRIPTION

[0045] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0046] As described in the background technology, when the power grid is operating normally, that is, when there is AC power, the photovoltaic inverter and the photovoltaic storage inverter are both connected to the power grid and can operate independently to control the power generation energy output by each of them to charge the battery or power the load. In the absence of AC power, the photovoltaic storage inverter and the photovoltaic inverter are usually connected to each other through a communication module, and an additional communication system is required to control the energy emitted by the photovoltaic storage inverter and the photovoltaic inverter. The inventors have found that the method of controlling the power change of the photovoltaic storage inverter or the photovoltaic inverter through the communication system in the prior art is not only inefficient, but also has a complex system structure.

[0047] Based on this, Figure 1 As shown, a photovoltaic microgrid inverter system is provided, the system comprising a photovoltaic storage inverter 10, a photovoltaic grid-connected module composed of a plurality of photovoltaic inverters 20, and a battery 30.

[0048] The photovoltaic inverter 10 is connected to a first photovoltaic panel 101, and the first photovoltaic panel 101 is used to convert light energy into electric energy of the photovoltaic inverter 10. The photovoltaic inverter 20 is connected to a second photovoltaic panel 201, and the second photovoltaic panel 201 is used to convert light energy into electric energy of the photovoltaic inverter 20.

[0049] The photovoltaic grid-connected module is connected to the photovoltaic storage inverter 10 through an AC bus. The photovoltaic storage inverter 10 is connected to the battery 30. When there is no mains electricity, the first power generation energy generated by the photovoltaic grid-connected module flows to the photovoltaic storage inverter 10 through the AC bus, and the photovoltaic storage inverter 10 charges the battery 30 based on the second power generation energy generated by itself and the first power generation energy.

[0050] Optionally, a dual-source conversion switch ATS is provided on the AC bus. When the dual-source conversion switch ATS switches to a closed route and is connected to the grid, the photovoltaic grid-connected module and the photovoltaic storage inverter are connected to the grid through the AC bus.

[0051] Optionally, the photovoltaic grid-connected module is also connected to a load module to supply power to the load.

[0052] In one embodiment, Figure 2 As shown, a power limiting control method for a photovoltaic microgrid inverter system is provided, which is applied to the photovoltaic storage inverter 10. In the absence of mains power, the photovoltaic storage inverter 10 limits its own output power and / or limits the power output of the photovoltaic grid-connected module. The method includes the following steps 201 to 202:

[0053] Step 201, obtaining the current charging power of the battery, and determining whether the current charging power is greater than the maximum charging power of the battery.

[0054] Step 202, if yes, calculate the power difference between the maximum charging power and the current charging power, and when the power difference is less than zero, reduce the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module according to the power difference, so as to control the power difference between the maximum charging power and the current charging power of the battery to be less than the set range.

[0055] Specifically, the photovoltaic storage inverter obtains the current charging power of the battery and determines whether the current charging power is greater than the maximum charging power of the battery. If so, the current charging power is subtracted from the maximum charging power to obtain the power difference. When the power difference is less than zero, the power limiting control strategy of the photovoltaic storage inverter is triggered. The power limiting control strategy includes: 1. Reducing the second power generation energy generated by the photovoltaic storage inverter itself. 2. By increasing the AC frequency on the AC bus, the first power generation energy generated by the photovoltaic grid-connected module is reduced, so that the power difference between the maximum charging power of the battery and the current charging power is controlled to be less than the set range.

[0056] In this embodiment, in the event of a power outage in the grid, since the photovoltaic storage inverter controls the AC bus voltage, the photovoltaic storage inverter can not only achieve its own power limiting regulation, but also change the AC frequency of the AC bus to achieve power limiting regulation of the photovoltaic grid-connected module. Therefore, there is no need for communication between the photovoltaic storage inverter and the photovoltaic inverter. Under the condition that the sum of the rated powers of all photovoltaic inverters is less than the rated power of the photovoltaic storage inverter, any photovoltaic inverter that meets the grid-connected certification can be selected to achieve accurate and rapid power limiting.

[0057] In one embodiment, the photovoltaic power storage inverter 10 includes a BOOST circuit, which is used to boost the output voltage of the first photovoltaic panel to an input voltage that can be connected to the photovoltaic power storage inverter 10. Figure 3 As shown, in step 202, according to the power difference, the second power generation energy generated by the photovoltaic storage inverter itself is reduced, which specifically includes the following steps 301 to 304:

[0058] Step 301, determining whether the BOOST circuit is in an enabled state.

[0059] Step 302: If yes, the power difference is input into a PI regulator to adaptively generate a maximum reference current for the battery.

[0060] Step 303: Obtain the maximum charging current currently allowed by the battery.

[0061] The maximum charging current currently allowed by the battery 30 is determined by the remaining power state SOC of the battery 30 .

[0062] Step 304, calculate the current difference between the maximum reference current and the maximum charging current, and use the current difference as the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation, thereby adjusting the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

[0063] In detail, the BOOST circuit is controlled by the control unit of the photovoltaic storage inverter to perform dual-loop PID regulation. The dual-loop PID regulation includes current inner-loop regulation and voltage outer-loop regulation. The photovoltaic storage inverter first determines whether the BOOST circuit is in an enabled state. When the BOOST circuit is in an enabled state, the power difference is input into the PI regulator, the most suitable maximum reference current of the battery is adaptively generated, the current difference between the maximum reference current and the maximum charging current is calculated, and the current difference is used as the maximum limit value of the reference current when the BOOST circuit performs current inner-loop regulation, so that the input current of the first photovoltaic panel 101 input to the photovoltaic storage inverter gradually decreases, thereby reducing the second power generation energy generated by the photovoltaic storage inverter itself, until the current charging power of the battery stabilizes and fluctuates around the maximum charging power, and the fluctuation range is less than or equal to the set range.

[0064] In this embodiment, the photovoltaic storage inverter realizes its own power limitation by limiting the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation, thereby stably maintaining the current charging power of the battery near the maximum charging power, which not only ensures dynamic and efficient charging of the battery, but also ensures the stable operation of the photovoltaic microgrid inverter system.

[0065] In one embodiment, the photovoltaic storage inverter 10 further includes a BUCK-BOOST circuit, and the BUCK-BOOST circuit is used to convert the second power generation energy of the photovoltaic storage inverter 10 into a charging voltage that can be connected to the battery. Figure 4 As shown, in step 202, according to the power difference, the second power generation energy generated by the photovoltaic storage inverter itself is reduced, and the following steps 401 to 403 are also included:

[0066] Step 401, determining whether the BOOST circuit is in an enabled state.

[0067] Step 402: If not, input the power difference into a PI regulator to adaptively generate the maximum reference current of the battery.

[0068] Step 403, using the maximum reference current as the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation, thereby regulating the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

[0069] In detail, the BUCK-BOOST circuit is also controlled by the control unit of the photovoltaic storage inverter to perform dual-loop PID regulation. When the BOOST circuit is not working and is in bypass mode, the photovoltaic storage inverter inputs the power difference into the PI regulator to adaptively generate the maximum reference current of the battery. The maximum reference current is used as the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation, so that the current input to the battery by the photovoltaic storage inverter gradually decreases, thereby reducing the second power generation energy generated by the photovoltaic storage inverter itself, until the current charging power of the battery stabilizes and fluctuates around the maximum charging power, and the fluctuation range is less than or equal to the set range.

[0070] In this embodiment, the photovoltaic storage inverter realizes its own power limitation by limiting the minimum reference current limit value when the BUCK-BOOST circuit performs current inner loop regulation, thereby stably maintaining the current charging power of the battery near the maximum charging power, ensuring dynamic and efficient charging of the battery and stable operation of the system.

[0071] In one embodiment, if Figure 5 As shown, step 202 of reducing the first power generation energy generated by the photovoltaic grid-connected module specifically includes the following steps 501 to 503:

[0072] Step 501, when the power difference is less than zero, calculating the overfrequency load reduction value of the photovoltaic grid-connected module.

[0073] Step 502, obtaining the current AC frequency of the AC bus.

[0074] Step 503, cyclically summing the overfrequency load reduction value and the current AC frequency, obtaining a first AC frequency based on each summation, and controlling the first power generation energy generated by the photovoltaic grid-connected module to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

[0075] In detail, the photovoltaic storage inverter and the photovoltaic grid-connected module comply with the grid-connected certification, and the same batch of photovoltaic inverters that have passed the grid-connected certification have the same overfrequency load reduction curve. Therefore, the photovoltaic storage inverter calculates the overfrequency load reduction value of the photovoltaic grid-connected module through the overfrequency load reduction curve. Next, the current AC frequency of the AC bus is obtained, and the overfrequency load reduction value is cyclically summed with the current AC frequency. The first AC frequency is obtained according to each summation, and the first power generation energy generated by the photovoltaic grid-connected module is controlled to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

[0076] In this embodiment, the photovoltaic storage inverter controls the AC frequency on the AC bus to achieve power limiting of the photovoltaic inverter in the photovoltaic grid-connected module, thereby achieving power limiting of the current charging power of the battery, ensuring dynamic and efficient charging of the battery and stable operation of the system.

[0077] Furthermore, if Figure 6 As shown, step 202 of reducing the first power generation energy generated by the photovoltaic grid-connected module also includes the following steps 601 to 603:

[0078] Step 601, when the power difference is greater than or equal to zero, calculating the overfrequency load reduction value of the photovoltaic grid-connected module.

[0079] Step 602, obtaining the current AC frequency of the AC bus.

[0080] Step 603, cyclically subtracting the overfrequency load reduction value from the current AC frequency, obtaining a second AC frequency based on each subtraction, and controlling the first power generation energy generated by the photovoltaic grid-connected module to gradually increase until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

[0081] In detail, following the previous embodiment, since the first AC frequency is obtained by summing each time, the first power generation energy generated by the photovoltaic grid-connected module is gradually reduced, so that the current charging power of the battery fluctuates at the size of the maximum charging power, and the power difference value recalculated during the fluctuation process may be greater than zero, indicating that the current charging power begins to decrease. In order to maintain a stable fluctuation of the current charging power and avoid a large decrease, the photovoltaic storage inverter will also cyclically differenciate the overfrequency load reduction value with the current AC frequency when the power difference is greater than or equal to zero, and obtain the second AC frequency based on each difference, and control the first power generation energy generated by the photovoltaic grid-connected module to gradually increase, so that the current charging power of the battery is stably maintained near the maximum charging power.

[0082] In one embodiment, calculating the overfrequency load reduction value of the photovoltaic grid-connected module includes:

[0083]

[0084] Among them, F1 is the frequency of the start load reduction point in the overfrequency load reduction curve, F2 is the frequency of the overfrequency load reduction curve at which the power is reduced to the minimum power, and Tr is the load reduction response time.

[0085] It should be noted that the step of limiting the power of the second power generation energy generated by the photovoltaic storage inverter in the above embodiment can be executed separately, or it can be executed together with the step of limiting the power of the first power generation energy of the photovoltaic grid-connected module by the photovoltaic storage inverter. When the two are executed together, the power limit adjustment time of the system is greatly shortened.

[0086] In one embodiment, the method further includes: setting a power limit constant threshold; determining whether the power difference between the maximum charging power and the current charging power is greater than the power limit constant threshold, and if so, setting the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation to the maximum rated value of the BOOST circuit, or setting the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation to the minimum rated value of the BUCK-BOOST circuit.

[0087] Specifically, since the power difference is less than zero, the photovoltaic storage inverter will be automatically triggered to execute the power limit control strategy described in the above embodiments. In order to avoid the photovoltaic storage inverter from being in a frequent switching state of starting or stopping the power limit control strategy, a power limit constant threshold is set. After the photovoltaic storage inverter starts the power limit strategy, if the power difference between the maximum charging power of the battery and the current charging power is less than or equal to the power limit constant threshold, the photovoltaic storage inverter continues to execute the power limit strategy. If at this time, the growth rate of the load power exceeds the set threshold, or the light is weakened, the power generation power of the inverter is weakened, or the current maximum charging current of the battery pack suddenly increases (for example, suddenly increases from 0A to 10A), causing the power difference to be greater than the power limit constant threshold, the photovoltaic storage inverter stops the power limit strategy, and the photovoltaic storage inverter sets the maximum limit value of the reference current when the BOOST circuit performs the current inner loop regulation to the maximum rated value of the BOOST circuit, or sets the minimum limit value of the reference current when the BUCK-BOOST circuit performs the current inner loop regulation to the minimum rated value of the BUCK-BOOST circuit. The AC frequency of the AC bus will also be restored to the rated AC frequency of the AC bus.

[0088] In one embodiment, a photovoltaic power storage inverter is provided, the photovoltaic power storage inverter includes a control unit, and the control unit is used to implement the steps corresponding to the power limiting control method of the photovoltaic microgrid inverter system as described in the above embodiments.

[0089] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0090] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0091] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0092] It can be understood that the “connection” in the above embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0093] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0094] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0095] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A power limiting control method for a photovoltaic microgrid inverter system, wherein the photovoltaic microgrid inverter system comprises a photovoltaic storage inverter, a photovoltaic grid-connected module composed of a plurality of photovoltaic inverters, and a battery, wherein the first power generation energy generated by the photovoltaic grid-connected module flows to the photovoltaic storage inverter through an AC bus, and the photovoltaic storage inverter charges the battery based on the second power generation energy generated by itself and the first power generation energy, characterized in that: Applied to the photovoltaic energy storage inverter, the method comprises: Obtaining a current charging power of the battery, and determining whether the current charging power is greater than a maximum charging power of the battery; If so, the power difference between the maximum charging power and the current charging power is calculated. When the power difference is less than zero, the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module are reduced according to the power difference, so as to control the power difference between the maximum charging power and the current charging power of the battery to be less than the set range.

2. The power limiting control method of the photovoltaic microgrid inverter system according to claim 1, characterized in that: The photovoltaic storage inverter is connected to a first photovoltaic panel, the first photovoltaic panel is used to convert light energy into electrical energy of the photovoltaic storage inverter, the photovoltaic storage inverter includes a BOOST circuit, and the BOOST circuit is used to boost the output voltage of the first photovoltaic panel to an input voltage that can be connected to the photovoltaic storage inverter for use; The reducing the second power generation energy generated by the photovoltaic storage inverter itself according to the power difference includes: Determine whether the BOOST circuit is in an enabled state; If yes, the power difference is input into the PI regulator to adaptively generate the maximum reference current of the battery; Obtaining the maximum charging current currently allowed by the battery; The current difference between the maximum reference current and the maximum charging current is calculated, and the current difference is used as the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation, thereby adjusting the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

3. The power limiting control method of the photovoltaic microgrid inverter system according to claim 2, characterized in that: The photovoltaic storage inverter further includes a BUCK-BOOST circuit, which is used to convert the second power generation energy of the photovoltaic storage inverter into a charging voltage that can be connected to the battery; and reducing the second power generation energy generated by the photovoltaic storage inverter itself according to the power difference also includes: Determine whether the BOOST circuit is in an enabled state; If not, the power difference is input into a PI regulator to adaptively generate a maximum reference current for the battery; The maximum reference current is used as the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation, thereby adjusting the second power generation energy generated by the photovoltaic storage inverter to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than the set range.

4. The power limiting control method of the photovoltaic microgrid inverter system according to claim 1, characterized in that: The reducing the first power generation energy generated by the photovoltaic grid-connected module comprises: When the power difference is less than zero, calculating an overfrequency load reduction value of the photovoltaic grid-connected module; Obtaining the current AC frequency of the AC bus; The overfrequency load reduction value is cyclically summed with the current AC frequency, and a first AC frequency is obtained according to each summation, and the first power generation energy generated by the photovoltaic grid-connected module is controlled to gradually decrease until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

5. The power limiting control method of the photovoltaic microgrid inverter system according to claim 4, characterized in that: The method further comprises: When the power difference is greater than or equal to zero, calculating an overfrequency load reduction value of the photovoltaic grid-connected module; Obtaining the current AC frequency of the AC bus; The overfrequency load reduction value is cyclically subtracted from the current AC frequency, and a second AC frequency is obtained based on each subtraction. The first power generation energy generated by the photovoltaic grid-connected module is controlled to gradually increase until the power difference between the maximum charging power of the battery and the current charging power is less than a set range.

6. The power limiting control method of the photovoltaic microgrid inverter system according to claim 4, characterized in that: Calculating the overfrequency load reduction value of the photovoltaic grid-connected module includes: Among them, F1 is the frequency of the start load reduction point in the overfrequency load reduction curve, F2 is the frequency of the overfrequency load reduction curve at which the power is reduced to the minimum power, and Tr is the load reduction response time.

7. The power limiting control method of the photovoltaic microgrid inverter system according to claim 3, characterized in that: The method further comprises: Set a constant power limit threshold; Determine whether the power difference between the maximum charging power and the current charging power is greater than the power limit constant threshold; if so, set the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation to the maximum rated value of the BOOST circuit, or set the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation to the minimum rated value of the BUCK-BOOST circuit.

8. The power limiting control method of a photovoltaic microgrid inverter system according to any one of claims 2 to 7, characterized in that: The photovoltaic grid-connected module is also connected to a load module, and the method further comprises: Obtaining the load power when the load module is running; If the growth rate of the load power exceeds the set threshold after reducing the second power generation energy generated by the photovoltaic storage inverter and the first power generation energy generated by the photovoltaic grid-connected module, the maximum limit value of the reference current when the BOOST circuit performs current inner loop regulation is set to the maximum rated value of the BOOST circuit, or the minimum limit value of the reference current when the BUCK-BOOST circuit performs current inner loop regulation is set to the minimum rated value of the BUCK-BOOST circuit.

9. A photovoltaic energy storage inverter, characterized in that: The photovoltaic energy storage inverter comprises a control unit, and the control unit is used to implement the steps corresponding to the method described in any one of claims 1 to 8 above.

10. A photovoltaic microgrid inverter system, characterized in that: The system comprises a photovoltaic storage inverter, a photovoltaic grid-connected module composed of a plurality of photovoltaic inverters, and a battery. The first power generation energy generated by the photovoltaic grid-connected module flows to the photovoltaic storage inverter through an AC bus. The photovoltaic storage inverter charges the battery based on the second power generation energy generated by itself and the first power generation energy. The photovoltaic storage inverter is used to: Obtaining a current charging power of the battery, and determining whether the current charging power is greater than a maximum charging power of the battery; If so, the power difference between the maximum charging power and the current charging power is calculated. When the power difference is less than zero, the second power generation energy generated by the photovoltaic storage inverter itself and the first power generation energy generated by the photovoltaic grid-connected module are reduced according to the power difference; thereby controlling the power difference between the maximum charging power and the current charging power of the battery to be less than the set range.

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