Optical storage inverter system and control method thereof

Abstract

The invention relates to an optical storage inverter system and a control method thereof, the optical storage inverter system comprises an energy storage module, a photovoltaic module and an MPPT module based on a BUCK-BOOST unit, the MPPT module is used for being connected with the photovoltaic module, and the optical storage inverter system further comprises an output module connected with the MPPT module and the energy storage module; the output module is further used for being connected with an external load or a power grid. Based on the improved optical storage inverter system, PV voltage and BUS voltage are collected, and the difference value between the PV voltage and the BUS voltage is calculated; adjusting the working mode of the BUCK-BOOST unit according to the difference value; wherein the working modes comprise a BOOST mode, a BUCK mode and a BUCK-BOOST mode. The voltage amplitude of the bus is controlled based on the BUCK-BOOST unit, direct charging and discharging of the bus and the energy storage module are achieved, and the conversion efficiency of the energy storage module is improved. Meanwhile, the cost of adopting the BUCK-BOOST unit is far lower than the additional cost of a bidirectional DCDC device.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage inverters, and in particular to a photovoltaic energy storage inverter system and a control method thereof. Background Art

[0002] Photovoltaic energy storage inverter, also known as photovoltaic energy storage inverter, is a device that converts the direct current generated by photovoltaic panels into alternating current, so that it can be connected to the power grid or directly drive electrical appliances. Therefore, the system that configures the energy storage system based on the photovoltaic energy storage inverter and connects the corresponding photovoltaic equipment to the grid is the photovoltaic energy storage inverter system.

[0003] As a new type of energy conversion system, the photovoltaic storage inverter has the functions of both photovoltaic power generation and battery charging and discharging. The battery cluster accounts for more than 85% of the cost of the entire photovoltaic storage inverter system. How to fully and efficiently apply the battery cluster for charging and discharging and give full play to the cost-effectiveness of the battery is a crucial link. In industrial and commercial application scenarios, users expect that the energy stored in the battery can be converted into the required mains electricity nearly 100%.

[0004] However, in the existing photovoltaic storage inverter system, the external battery cluster is connected to the DC bus in the photovoltaic storage inverter through a high-voltage box, an EMI filter, and a bidirectional DCDC power converter. Usually, the "bidirectional DCDC power converter" plays the role of voltage amplitude adjustment, that is, voltage step-up and step-down. When the battery cluster charges and discharges the inverter bus, it passes through the "bidirectional DCDC" link, and there will be about 1% power loss in this process. In addition to the additional loss, the "bidirectional DCDC" link will also add additional device costs. Summary of the invention

[0005] In order to solve the problems of power loss, extra loss and additional device cost caused by the "bidirectional DCDC" link in the existing photovoltaic storage inverter system, an embodiment of the present invention provides a photovoltaic storage inverter system and a control method thereof.

[0006] The embodiment of the present invention discloses a photovoltaic energy storage inverter system, comprising:

[0007] Energy storage module;

[0008] Photovoltaic modules;

[0009] An MPPT module based on a BUCK-BOOST unit, for connecting the photovoltaic module;

[0010] An output module connected to the MPPT module and the energy storage module respectively;

[0011] Wherein, the output module is also used to connect to an external load or a power grid.

[0012] The embodiment of the present invention provides a photovoltaic storage inverter system, including an energy storage module, a photovoltaic module, and an MPPT module based on a BUCK-BOOST unit. The MPPT module is used to connect the photovoltaic module, and also includes an output module connected to the MPPT module and the energy storage module respectively; wherein the output module is also used to connect an external load or a power grid. Based on the BUCK-BOOST unit, the bus voltage amplitude is controlled to realize direct charging and discharging of the bus and the energy storage module, thereby improving the conversion efficiency of the energy storage module. At the same time, the cost of using the BUCK-BOOST unit is much lower than the additional device cost of the "bidirectional DCDC".

[0013] As one of the optional embodiments, the photovoltaic module includes one or more PV loops;

[0014] The PV circuits are connected to the BUCK-BOOST units in a one-to-one correspondence.

[0015] As one of the optional embodiments, the BUCK-BOOST unit includes:

[0016] A first switch tube, wherein the first switch end is used to connect to the positive input end of the PV circuit;

[0017] A first diode, a cathode of which is connected to the second switch end of the first switch tube, and a cathode of which is used to be connected to the negative input end of the PV loop;

[0018] The cathode of the second diode is used as the BUS+ output terminal;

[0019] A second switch tube, a first switch end of which is connected to the anode of the second diode, and a second switch end of which is used as a BUS- output end;

[0020] The inductor is connected to the cathode of the first diode and the anode of the second diode respectively.

[0021] As one of the optional embodiments, the energy storage module includes an external battery cluster, a high-voltage box and an energy storage filter which are electrically connected in sequence.

[0022] As one of the optional embodiments, the photovoltaic module includes a photovoltaic component, a DC switch and a photovoltaic filter which are electrically connected in sequence.

[0023] As one of the optional embodiments, the output module includes a bus capacitor, an INV unit, an output filter and a relay that are electrically connected in sequence.

[0024] The embodiment of the present invention further discloses a control method of a photovoltaic storage inverter system, which is applied to the photovoltaic storage inverter system of any of the above embodiments, and comprises the following steps:

[0025] Collecting PV voltage and BUS voltage, and calculating the difference between the PV voltage and the BUS voltage;

[0026] The working mode of the BUCK-BOOST unit is adjusted according to the difference; wherein the working modes include BOOST mode, BUCK mode and BUCK-BOOST mode.

[0027] The control method of the photovoltaic storage inverter system of the embodiment of the present disclosure is based on the improved photovoltaic storage inverter system, collects the PV voltage and the BUS voltage, and calculates the difference between the PV voltage and the BUS voltage. The working mode of the BUCK-BOOST unit is adjusted according to the difference; wherein the working modes include BOOST mode, BUCK mode and BUCK-BOOST mode. Based on the BUCK-BOOST unit, the bus voltage amplitude is controlled to realize direct charging and discharging of the bus and the energy storage module, thereby improving the conversion efficiency of the energy storage module. At the same time, the cost of using the BUCK-BOOST unit is much lower than the additional device cost of the "bidirectional DCDC".

[0028] As one of the optional embodiments, the process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of:

[0029] When the difference is a negative value, the BUCK-BOOST unit is controlled to adopt the BOOST mode.

[0030] As one of the optional embodiments, the process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of:

[0031] When the difference is a positive value, the BUCK-BOOST unit is controlled to adopt the BUCK mode.

[0032] As one of the optional embodiments, the process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of:

[0033] When the difference is within the set difference interval, the BUCK-BOOST unit is controlled to adopt the BUCK-BOOST mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A module structure diagram of a photovoltaic storage inverter system according to a disclosed embodiment;

[0035] Figure 2 A module structure diagram of a photovoltaic storage inverter system according to a preferred embodiment;

[0036] Figure 3 A schematic diagram of an inverter charging an energy storage battery in a preferred embodiment;

[0037] Figure 4 A schematic diagram of charging the energy storage battery from the grid side in a preferred embodiment;

[0038] Figure 5 A schematic diagram of the energy storage battery discharging to the inverter in a preferred embodiment;

[0039] Figure 6 A schematic diagram of a BUCK-BOOST unit circuit in a preferred embodiment;

[0040] Figure 7 A flow chart of a control method of a photovoltaic storage inverter system according to a disclosed embodiment;

[0041] Figure 8 A flow chart of a control method of a photovoltaic storage inverter system according to a preferred embodiment;

[0042] Fig. 9 FIG. 4 is a schematic diagram of a BUCK-BOOST unit circuit according to another preferred embodiment. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0044] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0045] In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of some known functions and known components.

[0046] An embodiment of the present disclosure provides a photovoltaic energy storage inverter system.

[0047] Figure 1 FIG. 1 is a module structure diagram of a photovoltaic storage inverter system of a disclosed embodiment. Figure 1 As shown, a photovoltaic storage inverter system of a disclosed embodiment includes:

[0048] Energy storage module 100;

[0049] Photovoltaic module 101;

[0050] An MPPT module 102 based on a BUCK-BOOST unit 200, used to connect the photovoltaic module 101;

[0051] An output module 103 connected to the MPPT module 102 and the energy storage module 100 respectively;

[0052] The output module 103 is also used to connect to an external load or a power grid.

[0053] like Figure 1 As shown, the energy storage module 100 is used to place the battery cluster, charge and store energy according to the output of the photovoltaic module 101 or the power supply of the power grid, and supply power to the outside during discharge. The photovoltaic module 101 performs photovoltaic power generation according to the photovoltaic components, charges the energy storage module 100 or outputs it to the external load or the power grid. The output module 103 serves as an electrical path intermediary for the energy storage module 100, the photovoltaic module 101, the external load, and the power grid, and adjusts the electrical direction of each electrical path.

[0054] Among them, Figure 1 As shown, the photovoltaic module 101 includes one or more PV loops 201;

[0055] The PV (Photovoltaic) loops 201 are connected one-to-one with the BUCK-BOOST units 200. Each BUCK-BOOST unit 200 processes a corresponding PV loop 201.

[0056] As one of the optional embodiments, Figure 2 FIG. 1 is a module structure diagram of a photovoltaic storage inverter system according to a preferred embodiment. Figure 2 As shown, the energy storage module 100 includes an external battery cluster, a high voltage box and an energy storage filter which are electrically connected in sequence. The photovoltaic module 101 includes a photovoltaic assembly, a DC switch and a photovoltaic filter which are electrically connected in sequence. The output module 102 includes a bus capacitor, an INV (inverter) unit, an output filter and a relay which are electrically connected in sequence.

[0057] Figure 3 The schematic diagram of the inverter charging the energy storage battery in the preferred embodiment is as follows: Figure 3As shown in the figure, under normal conditions with sufficient sunshine, the inverter receives PV energy from the photovoltaic panels and directly charges the external battery cluster through the BUS bus terminal. At the same time, it can also be transferred to the INV unit through the BUS bus for grid-connected or off-grid loading. Figure 3 As shown by the arrow, at this time, the BUS charges the battery directly through a wire connection without any intermediate power change link.

[0058] Figure 4 Schematic diagram of charging the energy storage battery from the grid side in a preferred embodiment, as shown in Figure 4 As shown, in some special cases, such as storing electricity during the night when the grid is trough, the grid side provides energy through the INV unit, and then directly charges the external battery cluster by adjusting the BUS voltage, gradually filling it up. Figure 4 As shown by the arrow, at this time, the BUS busbar and the external battery cluster are directly connected through a wire without an intermediate power change link.

[0059] Figure 5 FIG. 1 is a schematic diagram of discharging the energy storage battery to the inverter in a preferred embodiment, as shown in FIG. Figure 5 As shown, when the photovoltaic strings stop working at night, the energy stored in the external battery cluster is released. The external battery cluster is directly connected to the BUS bus as energy support to achieve grid-connected or off-grid load through the INV unit.

[0060] As one of the optional embodiments, Figure 6 FIG. 1 is a schematic diagram of a BUCK-BOOST unit circuit according to a preferred embodiment. Figure 6 As shown, the BUCK-BOOST unit includes:

[0061] The first switch tube Q1, the first switch end is used to connect to the positive input end PV+ of the PV circuit;

[0062] A first diode D1, a cathode of which is connected to the second switch end of the first switch tube Q1, and a cathode of which is used to be connected to the negative input end PV- of the PV loop;

[0063] The cathode of the second diode D2 is used as a BUS+ output terminal;

[0064] A second switch tube Q2, a first switch end of which is connected to the anode of the second diode D2, and a second switch end of which is used as a BUS- output end;

[0065] The inductor L1 is connected to the cathode of the first diode D1 and the anode of the second diode D2 respectively.

[0066] Based on the photovoltaic-storage inverter system of any embodiment of the present disclosure, the embodiment of the present disclosure also provides a control method of the photovoltaic-storage inverter system.

[0067] Figure 7FIG. 1 is a flow chart of a control method of a photovoltaic storage inverter system according to a disclosed embodiment. Figure 7 As shown, it includes step S100 and step S101:

[0068] S100, collecting a PV voltage and a BUS voltage, and calculating a difference between the PV voltage and the BUS voltage;

[0069] S101, adjusting the working mode of the BUCK-BOOST unit according to the difference; wherein the working mode includes a BOOST mode, a BUCK mode and a BUCK-BOOST mode.

[0070] As one of the preferred embodiments, Figure 8 FIG. 1 is a flow chart of a control method of a photovoltaic storage inverter system according to a preferred embodiment. Figure 8 As shown, the process of adjusting the working mode of the BUCK-BOOST unit according to the difference in step S101 includes steps S200 to S202:

[0071] S200 , when the difference is a negative value, controlling the BUCK-BOOST unit to adopt a BOOST mode.

[0072] S201, when the difference is a positive value, controlling the BUCK-BOOST unit to adopt the BUCK mode.

[0073] S202, when the difference is within a set difference interval, controlling the BUCK-BOOST unit to adopt a BUCK-BOOST mode.

[0074] Preferably, after the external battery cluster is directly connected to the BUS bus, the voltage of the external battery cluster is at the same voltage as the BUS bus. The photovoltaic string is the main energy source, and the MPPT circuit is required to regulate its voltage, that is, when the PV voltage is higher than the external battery cluster voltage by a certain value X, the BUCK mode is selected. When the PV voltage is lower than the battery cluster voltage by a certain value X, the BOOST mode is selected. When the difference between the PV voltage and the battery cluster voltage is within the X value range, the BUCK-BOOST mode is selected.

[0075] like Figure 6 As shown in the figure, when the PV voltage is lower than the BUS voltage X, the MPPT adopts the BOOST mode, Q1 is driven to a continuous high level, and Q1 is directly turned on. The duty cycle of the Q2 drive signal is controlled to adjust the gain of the input voltage to the output voltage to achieve the maximum power tracking of the PV.

[0076] Fig. 9 FIG. 1 is a schematic diagram of a BUCK-BOOST unit circuit in another preferred embodiment. Fig. 9As shown in the figure, when the PV voltage is higher than the BUS voltage X, the MPPT adopts the BUCK mode, Q2 is driven to a continuous low level, and Q2 is cut off. The duty cycle of the Q1 drive signal is controlled to adjust the gain of the input voltage to the output voltage to achieve the maximum power tracking of the PV.

[0077] When the PV voltage and BUS voltage X are within the phase difference of X, the BUCK-BOOST mode is entered.

[0078] Assume that the switching period of Q1 and Q2 is T, the on-time of Q1 is TON1, and the on-time of Q2 is TON2. TON1≥TON2, the circuit has three working modes. At 0-TON2, Q1 and Q2 are turned on at the same time, inductor L1 stores energy, and the voltage across the inductor is VIN.

[0079] Based on this, the photovoltaic storage inverter system and control method of the embodiment of the present disclosure, the photovoltaic storage inverter system includes an energy storage module, a photovoltaic module and an MPPT module based on a BUCK-BOOST unit, the MPPT module is used to connect the photovoltaic module, and also includes an output module connected to the MPPT module and the energy storage module respectively; wherein the output module is also used to connect an external load or a power grid. Based on the improved photovoltaic storage inverter system, the PV voltage and the BUS voltage are collected, and the difference between the PV voltage and the BUS voltage is calculated. The working mode of the BUCK-BOOST unit is adjusted according to the difference; wherein the working modes include BOOST mode, BUCK mode and BUCK-BOOST mode. Based on the BUCK-BOOST unit, the bus voltage amplitude is controlled to realize direct charging and discharging of the bus and the energy storage module, thereby improving the conversion efficiency of the energy storage module. At the same time, the cost of using the BUCK-BOOST unit is much lower than the additional device cost of the "bidirectional DCDC".

[0080] There are a few points to note about this disclosure:

[0081] (1) The drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure, and other structures may refer to the general design.

[0082] (2) For the sake of clarity, the thickness and size of layers or structures are exaggerated in the drawings used to describe the embodiments of the present invention. It is understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element, or there may be intervening elements.

[0083] (3) In the absence of conflict, the embodiments of the present disclosure and the features in the embodiments may be combined with each other to obtain new embodiments. The above are only specific implementation methods of the present disclosure, but the protection scope of the present disclosure is not limited thereto. The protection scope of the present disclosure shall be based on the protection scope of the claims.

[0084] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above 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.

[0085] The above 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 patent 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 patent application shall be subject to the attached claims.

Claims

1. A photovoltaic energy storage inverter system, characterized in that: include: Energy storage module; Photovoltaic modules; An MPPT module based on a BUCK-BOOST unit, for connecting the photovoltaic module; An output module connected to the MPPT module and the energy storage module respectively; Wherein, the output module is also used to connect to an external load or a power grid.

2. The photovoltaic storage inverter system according to claim 1, characterized in that: The photovoltaic module includes one or more PV loops; The PV circuits are connected to the BUCK-BOOST units in a one-to-one correspondence.

3. The photovoltaic storage inverter system according to claim 1, characterized in that: The BUCK-BOOST unit includes: A first switch tube, wherein the first switch end is used to connect to the positive input end of the PV circuit; A first diode, a cathode of which is connected to the second switch end of the first switch tube, and a cathode of which is used to be connected to the negative input end of the PV circuit; The cathode of the second diode is used as the BUS+ output terminal; A second switch tube, a first switch end of which is connected to the anode of the second diode, and a second switch end of which is used as a BUS- output end; The inductor is connected to the cathode of the first diode and the anode of the second diode respectively.

4. The photovoltaic storage inverter system according to claim 1, characterized in that: The energy storage module includes an external battery cluster, a high voltage box and an energy storage filter which are electrically connected in sequence.

5. The photovoltaic storage inverter system according to claim 1, characterized in that: The photovoltaic module includes a photovoltaic component, a DC switch and a photovoltaic filter which are electrically connected in sequence.

6. The photovoltaic storage inverter system according to claim 1, characterized in that: The output module includes a bus capacitor, an INV unit, an output filter and a relay which are electrically connected in sequence.

7. A control method for a photovoltaic power storage inverter system, applied to the photovoltaic power storage inverter system according to any one of claims 1 to 6, characterized in that: Includes steps: Collecting PV voltage and BUS voltage, and calculating the difference between the PV voltage and the BUS voltage; The working mode of the BUCK-BOOST unit is adjusted according to the difference; wherein the working modes include BOOST mode, BUCK mode and BUCK-BOOST mode.

8. The control method of the photovoltaic energy storage inverter system according to claim 7, characterized in that: The process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of: When the difference is a negative value, the BUCK-BOOST unit is controlled to adopt the BOOST mode.

9. The control method of the photovoltaic energy storage inverter system according to claim 7, characterized in that: The process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of: When the difference is a positive value, the BUCK-BOOST unit is controlled to adopt the BUCK mode.

10. The control method of the photovoltaic energy storage inverter system according to claim 7, characterized in that: The process of adjusting the working mode of the BUCK-BOOST unit according to the difference comprises the steps of: When the difference is within the set difference interval, the BUCK-BOOST unit is controlled to adopt the BUCK-BOOST mode.

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