Photovoltaic energy storage overvoltage protection control method

Abstract

The application relates to a photovoltaic energy storage overvoltage protection control method, which is based on a photovoltaic energy storage overvoltage protection circuit. The photovoltaic energy storage overvoltage protection circuit comprises one or more MPPT circuits in a cascade structure. The MPPT circuit comprises a first controllable switching device for controlling the conduction or turn-off of an MPPT access path according to a first control signal, a second controllable switching device for controlling the conduction or turn-off of the MPPT circuit according to a second control signal, a third controllable switching device for controlling the conduction or turn-off according to a third control signal, and an inductive element connected in series in the MPPT circuit. The first controllable switching device is controlled to be turned on, the second controllable switching device and the third controllable switching device are kept turned off, and if a current is detected on the inductive element, a fault is determined. After the fault is determined, the third controllable switching device is controlled to be turned on and the first controllable switching device is controlled to be turned off, so as to eliminate the fault current, effectively cope with the excessively high MPPT voltage, protect the overall circuit system, and identify the fault circuit for corresponding processing.

Description

Technical Field

[0001] This application relates to the field of photovoltaic energy storage system technology, and in particular to a photovoltaic energy storage overvoltage protection control method. Background Technology

[0002] Photovoltaic energy storage is a power generation system that combines a solar photovoltaic power generation system with energy storage devices. It mainly consists of photovoltaic equipment and energy storage devices. The photovoltaic equipment converts sunlight into electrical energy through the photovoltaic effect of semiconductor materials, while the energy storage device is used to store electrical energy so that it can be released when sunlight is insufficient or when needed.

[0003] In current photovoltaic (PV) energy storage systems, PV devices use MPPT (Maximum Power Point Tracking) for multiple outputs, directly connected to the energy storage devices, i.e., the storage batteries, forming the DC-side bus. Because the storage batteries are directly connected to the bus, the bus voltage is limited by the battery voltage and cannot fluctuate, causing the MPPT voltage to be higher or lower than the bus voltage. Therefore, the MPPT circuit must use cascaded buck-boost circuits. When the MPPT voltage is high, such as 1300V, but the maximum bus voltage is limited to 1100V, excessively high voltage can cause the bus voltage to rise rapidly under certain conditions, damaging components. For example, if the storage battery disconnects or the switching devices short-circuit, the PV output can rapidly charge the bus electrolytic capacitors, causing them to explode due to overvoltage. Summary of the Invention

[0004] Therefore, in order to address the problem that excessive MPPT voltage in existing MPPT circuits leads to a rapid rise in bus voltage and damages devices, this invention provides a photovoltaic energy storage overvoltage protection circuit and its control method.

[0005] This invention provides a photovoltaic energy storage overvoltage protection circuit, including one or more cascaded MPPT circuits;

[0006] The MPPT circuit includes:

[0007] The first controllable switching device is used to control the MPPT access path to be turned on or off according to the first control signal;

[0008] The second controllable switching device is used to control the MPPT circuit to be turned on or off according to the second control signal;

[0009] The third controllable switching device is used to turn on or off according to the third control signal;

[0010] An inductive element is connected in series in the MPPT circuit.

[0011] The photovoltaic energy storage overvoltage protection circuit of this invention includes one or more cascaded MPPT circuits. Each MPPT circuit includes: a first controllable switching device for controlling the MPPT access path to be turned on or off according to a first control signal; a second controllable switching device for controlling the MPPT circuit to be turned on or off according to a second control signal; a third controllable switching device for being turned on or off according to a third control signal; and an inductive element connected in series in the MPPT circuit. The on / off switching of each device provides a control basis for dealing with overvoltage, and the MPPT circuit with an overvoltage fault can be identified through the switching devices and current detection, facilitating protection processing.

[0012] As one optional embodiment, the first controllable switching device is a relay.

[0013] As one optional embodiment, the second controllable switching device and the third controllable switching device are semiconductor switching devices.

[0014] As one optional embodiment, the second controllable switching device and the third controllable switching device are switching transistors.

[0015] As one alternative embodiment, the inductive element is an inductor.

[0016] As one optional embodiment, the MPPT circuit further includes:

[0017] A first capacitor connected in parallel with the MPPT access path;

[0018] The first capacitor, the MPPT access path, and the first controllable switching device can form a single circuit.

[0019] As one optional embodiment, the MPPT circuit further includes:

[0020] A second capacitor connected in parallel with the energy storage battery;

[0021] The second capacitor and the energy storage battery can form a single circuit.

[0022] As one optional embodiment, the MPPT circuit further includes:

[0023] The first diode connected in parallel with the energy storage battery;

[0024] The first diode, the inductive element, and the third controllable switching device can form a single circuit.

[0025] As one optional embodiment, the MPPT circuit further includes:

[0026] The second diode connected in series in the MPPT circuit;

[0027] The positive terminal of the second diode is connected to the inductive element, and the negative terminal is connected to the energy storage battery.

[0028] This invention also provides a photovoltaic energy storage overvoltage protection control method, applied to the photovoltaic energy storage overvoltage protection circuit of the above-disclosed embodiments, including the following steps:

[0029] The first controllable switching device is turned on, while the second and third controllable switching devices are kept off. If current is detected on the inductive element, a fault is determined.

[0030] After a fault is detected, the third controllable switch is turned on and the first controllable switch is turned off to eliminate the fault current.

[0031] The photovoltaic energy storage overvoltage protection control method of this invention is based on a photovoltaic energy storage overvoltage protection circuit. It controls the first controllable switching device to be turned on while keeping the second and third controllable switching devices off. If current is detected on the inductive element, a fault is determined. After the fault is determined, the third controllable switching device is turned on and the first controllable switching device is turned off to eliminate the fault current, effectively cope with the MPPT voltage being too high, protect the overall circuit system, and identify the faulty circuit for corresponding processing. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a photovoltaic energy storage overvoltage protection circuit module according to a disclosed embodiment;

[0033] Figure 2 This is a schematic diagram of a photovoltaic energy storage overvoltage protection circuit according to a preferred embodiment;

[0034] Figure 3 This is a flowchart of a photovoltaic energy storage overvoltage protection control method according to a disclosed embodiment. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0036] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0037] To keep the following description of the embodiments of this disclosure clear and concise, detailed descriptions of some known functions and components have been omitted.

[0038] This disclosure provides an overvoltage protection circuit for photovoltaic energy storage.

[0039] Figure 1 This is a schematic diagram of a photovoltaic energy storage overvoltage protection circuit module according to a disclosed embodiment, as shown below. Figure 1 As shown, a photovoltaic energy storage overvoltage protection circuit of one disclosed embodiment includes one or more cascaded MPPT circuits;

[0040] The MPPT circuit includes:

[0041] The first controllable switching device 100 is used to control the MPPT access path to be turned on or off according to the first control signal.

[0042] The second controllable switching device 101 is used to control the MPPT circuit to be turned on or off according to the second control signal.

[0043] The third controllable switching device 102 is used to turn on or off according to the third control signal;

[0044] The inductive element 103 is connected in series in the MPPT circuit.

[0045] like Figure 1 As shown, the overall design concept of the MPPT circuit is to connect it in parallel with the energy storage battery Vbus, forming a DC bus at the connection point. Multiple MPPT circuits are cascaded, and each MPPT circuit is independent.

[0046] like Figure 1As shown, in each MPPT circuit, the first controllable switching device 100 controls the MPPT access path to be turned on or off. When it is turned on, MPPT (MPPT+ / MPPT-) is connected, and when it is turned off, MPPT (MPPT+ / MPPT-) is isolated.

[0047] like Figure 1 As shown, assuming the first controllable switch 100 is turned on, MPPT (MPPT+ / MPPT-) is connected, the MPPT circuit forms a path, and an electrical connection is established with the energy storage battery. The second controllable switch 101 is connected in series in the path of the MPPT circuit. When the second controllable switch 101 is turned on, the path conditions for forming the MPPT circuit are met. When turned off, the MPPT circuit is turned off.

[0048] As one optional embodiment, the same MPPT circuit may include one or two first controllable switching devices 100. When two first controllable switching devices 100 are included, each first controllable switching device 100 controls one MPPT (MPPT+ / MPPT+-) connection.

[0049] like Figure 1 As shown, assuming the first controllable switch device 100 is turned on and the second controllable switch device 101 is turned on, the MPPT circuit forms a path. If the third controllable switch device 102 is turned on, since it is connected in parallel with the energy storage battery, it forms an independent sub-circuit with the energy storage battery and interacts with the MPPT circuit.

[0050] like Figure 1 As shown, the inductive element 103 is connected in series in the MPPT circuit. When the MPPT circuit is turned on to form a loop, the inductive element 103 generates a current based on the voltage. This current has the conditions for visualization or detection, such as being detectable by an external testing tool.

[0051] As a preferred embodiment, such as Figure 1 As shown, the inductive element 103 is connected in series between the second controllable switching device 101 and the third controllable switching device 102.

[0052] The selection of the first controllable switching device 100, the second controllable switching device 101, and the third controllable switching device 102 is determined according to the application requirements of the MPPT circuit. Electronic switching devices, semiconductor switches, relays, etc., can be selected.

[0053] As a preferred embodiment, Figure 2 This is a schematic diagram of a photovoltaic energy storage overvoltage protection circuit according to a preferred embodiment, such as... Figure 2 As shown, the first controllable switching device 100 is a relay (K1…Kn). The second controllable switching device 101 and the third controllable switching device 102 are semiconductor switching devices.

[0054] Preferably, the second controllable switching device 101 and the third controllable switching device 102 are switching transistors. An external switching transistor drive signal serves as the second and third control signals to control their on / off states. Wherein, for example... Figure 2 As shown, the second controllable switching device 101 is T11…Tn1, and the third controllable switching device 102 is T12…Tn2.

[0055] The inductive element 103 is either an inductive element or a resistive element. Preferably, as shown below... Figure 2 As shown, the inductive element 103 is an inductor (L1…Ln).

[0056] As one of the preferred embodiments, such as Figure 2 As shown, the MPPT circuit further includes:

[0057] The first capacitor C1 is connected in parallel with the MPPT access path;

[0058] The first capacitor C1, the MPPT access path, and the first controllable switching device 100 can form a single circuit.

[0059] As one of the preferred embodiments, such as Figure 2 As shown, the MPPT circuit further includes:

[0060] The second capacitor C2 is connected in parallel with the energy storage battery;

[0061] The second capacitor C2 and the energy storage battery can form a single circuit.

[0062] As one of the preferred embodiments, such as Figure 2 As shown, the MPPT circuit further includes:

[0063] The first diode D1 is connected in parallel with the energy storage battery;

[0064] The first diode D1, the inductive element 103, and the third controllable switching device 102 can form a single circuit.

[0065] The positive terminal of the first diode D1 is used to connect to the ground terminal or the negative voltage terminal.

[0066] As one of the preferred embodiments, such as Figure 2 As shown, the MPPT circuit further includes:

[0067] The second diode D2 is connected in series in the MPPT circuit;

[0068] The positive terminal of the second diode D2 is connected to the inductive element 103, and the negative terminal is connected to the energy storage battery.

[0069] The photovoltaic energy storage overvoltage protection circuit of any embodiment of this disclosure includes one or more cascaded MPPT circuits. The MPPT circuit includes: a first controllable switching device 100, used to control the MPPT access path to be turned on or off according to a first control signal; a second controllable switching device 101, used to control the MPPT circuit to be turned on or off according to a second control signal; a third controllable switching device 102, used to be turned on or off according to a third control signal; and an inductive element 103 connected in series in the MPPT circuit. By turning on or off each switching device, a control basis for overvoltage response is provided, and the MPPT circuit with overvoltage faults can be identified through the switching devices and current detection, facilitating protection processing.

[0070] Based on the photovoltaic energy storage overvoltage protection circuit, this disclosure also provides a control method for the photovoltaic energy storage overvoltage protection circuit.

[0071] Figure 3 Here is a flowchart of a photovoltaic energy storage overvoltage protection control method according to a disclosed embodiment, as follows: Figure 3 As shown, a photovoltaic energy storage overvoltage protection control method according to a disclosed embodiment includes steps S10 and S11:

[0072] S10, control the first controllable switching device to be turned on, keep the second controllable switching device and the third controllable switching device turned off, and if current is detected on the inductive element, a fault is determined;

[0073] S11, after determining the fault, control the third controllable switch to turn on and control the first controllable switch to turn off, so as to eliminate the fault current.

[0074] by Figure 2 Based on the preferred embodiment, when an excessive bus voltage (e.g., >1000V) is detected, the driver of switch Tn1 is turned off, the driver of switch Tn2 is turned on, and switch Tn2 is kept constantly on. The current of each inductor Ln is detected, and the i-th MPPT circuit whose current exceeds the set current value is identified. The first controllable switching device Ki of the i-th MPPT circuit is disconnected. When the current of the i-th circuit is close to 0 and the current of other MPPT circuits is also 0, a fault in the i-th MPPT circuit is identified and reported, and all switches are blocked. The entire circuit is then restarted after the fault in the i-th MPPT circuit is resolved.

[0075] The photovoltaic energy storage overvoltage protection control method of this invention is based on a photovoltaic energy storage overvoltage protection circuit. It controls the first controllable switching device to be turned on while keeping the second and third controllable switching devices off. If current is detected on the inductive element, a fault is determined. After the fault is determined, the third controllable switching device is turned on and the first controllable switching device is turned off to eliminate the fault current, effectively cope with the MPPT voltage being too high, protect the overall circuit system, and identify the faulty circuit for corresponding processing.

[0076] The following points should be noted regarding this disclosure:

[0077] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure, and other structures can be referred to the general design.

[0078] (2) For clarity, the thickness and dimensions of layers or structures are enlarged in the accompanying drawings used to describe embodiments of the invention. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “above” or “below” another element, the element may be “directly” located “above” or “below” the other element, or there may be intermediate elements present.

[0079] (3) Where there is no conflict, the embodiments and features described herein can be combined to obtain new embodiments. The above are merely specific implementations of this disclosure, but the scope of protection of this disclosure is not limited thereto; the scope of protection of this disclosure should be determined by the scope of the claims.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0081] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A photovoltaic energy storage overvoltage protection control method, characterized in that, The application is applied to a photovoltaic energy storage overvoltage protection circuit, and the photovoltaic energy storage overvoltage protection circuit comprises one or more MPPT circuits in a cascade structure. The MPPT circuit comprises: a first controllable switching device for controlling the conduction or turn-off of the MPPT access path according to a first control signal; a second controllable switching device for controlling the conduction or turn-off of the MPTT circuit according to a second control signal; a third controllable switching device for controlling the conduction or turn-off according to a third control signal; an inductive element connected in series in the MPPT circuit; comprising the steps of: controlling the first controllable switching device to be turned on, keeping the second controllable switching device and the third controllable switching device to be turned off, and determining a fault if a current is detected on the inductive element; after determining the fault, controlling the third controllable switching device to be turned on and the first controllable switching device to be turned off to eliminate the fault current; the MPPT circuit further comprises: a second capacitor connected in parallel with the energy storage battery; the second capacitor and the energy storage battery can form a single loop a first diode connected in parallel with the energy storage battery; the first diode, the inductive element and the third controllable switching device can form a single loop a second diode connected in series in the MPPT circuit; the positive electrode of the second diode is connected to the inductive element, and the negative electrode is connected to the energy storage battery.

2. The photovoltaic energy storage overvoltage protection control method of claim 1, wherein, The first controllable switching device is a relay, a load switch or a circuit breaker.

3. The photovoltaic energy storage overvoltage protection control method of claim 1, wherein, The second controllable switching device and the third controllable switching device are semiconductor switching devices.

4. The photovoltaic energy storage overvoltage protection control method of claim 1, wherein, The second controllable switching device and the third controllable switching device are switching tubes.

5. The photovoltaic energy storage overvoltage protection control method of claim 1, wherein, The inductive element is an inductor.

6. The photovoltaic energy storage overvoltage protection control method of claim 1, wherein, The MPPT circuit further comprises: a first capacitor connected in parallel with the MPPT access path; the first capacitor, the MPPT access path and the first controllable switching device can form a single loop.

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