Direct current bus charging circuit, air conditioning unit and control method thereof

Abstract

The application discloses a DC bus charging circuit, an air conditioning unit and a control method thereof, wherein the DC bus charging circuit comprises: a rectifier module, an input end of which is connected with a live wire and a zero line of an AC power grid, and an output end of which is connected with a live wire and a zero line of a DC bus; and a charging resistor, which is located on a line between the rectifier module and the live wire of the DC bus or on a line between the rectifier module and the zero line of the DC bus, and is used for charging the DC bus by DC power output by the rectifier module. The application solves the problem that the DC bus charging circuit is easy to burn when the unit is started under load in the prior art, protects the charging circuit from being damaged, and enables the unit to be normally started under the condition that the DC bus is under load.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more specifically, to a DC bus charging circuit, an air conditioning unit, and a control method thereof. Background Technology

[0002] Existing photovoltaic-storage air conditioning systems require charging the capacitors on the DC bus before startup. However, these capacitors cannot be directly charged with high voltage; instead, a charging resistor is used. This charging circuit typically has a small current-carrying capacity. Once the DC bus voltage is established, i.e., charging is complete, the system can be started. If a load is connected to the DC bus, the load will require a large current after startup. Since the charging circuit has a small current-carrying capacity, this can easily lead to the charging circuit burning out, preventing the equipment from starting normally and damaging the charging circuit itself.

[0003] There is currently no effective solution to the problem that the DC bus charging circuit is prone to burnout during unit start-up under load in related technologies. Summary of the Invention

[0004] This invention provides a DC bus charging circuit, an air conditioning unit, and a control method thereof, to at least solve the problem that the DC bus charging circuit is prone to burnout when the unit is started under load in the prior art.

[0005] To address the aforementioned technical problems, according to one aspect of the present invention, a DC bus charging circuit is provided, wherein the AC power grid is connected to the DC bus via a converter; the DC bus charging circuit includes:

[0006] The rectifier module has its input terminals connected to the live and neutral wires of the AC power grid, and its output terminals connected to the live and neutral wires of the DC bus.

[0007] The charging resistor, located on the line between the rectifier module and the live wire of the DC bus, or on the line between the rectifier module and the neutral wire of the DC bus, is used to charge the DC bus with the DC power output from the rectifier module.

[0008] Furthermore, it also includes:

[0009] The first switching assembly is located on the line between the output terminal of the rectifier module and the DC bus;

[0010] The second switching assembly is located on the line between the AC power grid and the converter.

[0011] Furthermore, it also includes:

[0012] The controller, connected to the first switch assembly and the second switch assembly, is used to control the first switch assembly to open and the second switch assembly to close when a load is connected to the DC bus, so as to charge the DC bus through the load; and to control the first switch assembly to close when no load is connected to the DC bus, so as to charge the DC bus through the DC bus charging circuit.

[0013] Furthermore, it also includes:

[0014] A current sensor, located on the line between the rectifier module and the live wire of the DC bus, or on the line between the rectifier module and the neutral wire of the DC bus, is used to detect the charging current of the DC bus charging circuit.

[0015] The controller is also connected to a current sensor to determine whether a load is connected to the DC bus by the current detected by the current sensor after the first switching assembly is closed.

[0016] Furthermore, the first switching assembly is a two-pole switch, and the second switching assembly is a three-pole switch.

[0017] According to another aspect of the present invention, an air conditioning unit is provided, including the DC bus charging circuit as described above.

[0018] According to another aspect of the present invention, an air conditioning unit control method is provided, applied to the DC bus charging circuit as described above, the method comprising:

[0019] Before starting the air conditioning unit, control the DC bus charging circuit to be turned on;

[0020] Determine if a load is connected to the DC bus;

[0021] When a load is connected to the DC bus, the DC bus charging circuit is disconnected.

[0022] When the DC bus is not connected to a load, the DC bus is charged through the DC bus charging circuit.

[0023] Furthermore, after the DC bus charging circuit is disconnected, the method also includes: controlling the air conditioning unit to start under load and charging the DC bus through the load;

[0024] After charging the DC bus through the DC bus charging circuit, the method also includes: controlling the air conditioning unit to start under no-load after the DC bus charging is completed.

[0025] Furthermore, determining whether a load is connected to the DC bus includes:

[0026] Detect the charging current of the DC bus charging circuit;

[0027] Determine if the charging current is greater than the no-load charging current;

[0028] If yes, then the DC bus is connected to a load; otherwise, the DC bus is not connected to a load.

[0029] Furthermore, controlling the DC bus charging circuit to conduct includes: controlling the first switch assembly to close;

[0030] Disconnecting the DC bus charging circuit includes: disconnecting the first switching assembly;

[0031] Controlling the air conditioning unit to start under load, or controlling the air conditioning unit to start under no-load, includes: controlling the closing of the second switch assembly.

[0032] According to another aspect of the present invention, a storage medium containing computer-executable instructions is provided, which, when executed by a computer processor, are used to perform the air conditioning unit control method as described above.

[0033] This invention proposes a DC bus charging circuit, comprising a rectifier module and a charging resistor. One end of the circuit is connected to the AC power grid, and the other end is connected to the DC bus. The circuit samples the AC power, rectifies it, and charges the DC bus through the charging resistor. However, the charging circuit is independent of the DC bus. When the DC bus is connected to a load for startup, it will not affect the current of the charging circuit. Therefore, it allows units such as photovoltaic-storage-air conditioning systems to start normally when the DC bus is under load, improving the ease of use of the system and protecting the charging circuit from damage. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an optional structure of a photovoltaic-storage-air conditioning system according to an embodiment of the present invention;

[0035] Figure 2 This is an optional flowchart of an air conditioning unit control method according to an embodiment of the present invention;

[0036] Figure 3 This is another optional flowchart of the air conditioning unit control method according to an embodiment of the present invention.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Rectifier module; 2. Charging resistor; 3. First switch assembly; 4. Second switch assembly; 5. Current sensor; 6. Bidirectional (rectifier / inverter) module; 7. Inverter module; 8. AC motor; 9. Bus capacitor; 10. Bidirectional DC converter; 11. Photovoltaic module; 12. Energy storage battery; 13. DC load. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0041] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] It should be understood that although the terms first, second, third, etc., may be used to describe controllers in embodiments of the present invention, these controllers should not be limited to these terms. These terms are only used to distinguish controllers connected to different devices. For example, without departing from the scope of embodiments of the present invention, a first controller may also be referred to as a second controller, and similarly, a second controller may also be referred to as a first controller.

[0043] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0044] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0045] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0046] Example 1

[0047] In a preferred embodiment 1 of the present invention, a DC bus charging circuit is provided. This DC bus charging circuit can be applied to units with a DC bus, such as photovoltaic-storage-air conditioning systems. Specifically... Figure 1 This diagram illustrates one possible structural design of the photovoltaic-storage-air conditioning system, such as... Figure 1 As shown, the system includes: a bidirectional (rectifier / inverter) module 6, an inverter module 7, an AC motor 8 driving the air conditioner compressor, a bus capacitor 9, a DC bus charging circuit, a bidirectional photovoltaic DC converter 10 connected to the intermediate DC bus, a photovoltaic DC converter connected to a photovoltaic module 11, and an energy storage battery 12 connected to the DC bus via the bidirectional DC converter 10. A DC load 13 is also connected to the DC bus. The bidirectional module is connected to the AC grid at one end and to the DC bus at the other, while the inverter module is connected to the DC bus at one end and to the AC motor of the air conditioner compressor at the other.

[0048] The general startup method is to first charge the DC bus with the charging resistor, that is, charge the bus capacitor. After the bus capacitor voltage is established, the bidirectional module is turned on to stabilize the DC bus. Then, the bidirectional photovoltaic DC converter is started to connect the photovoltaic power generation to the DC bus, and finally the air conditioner compressor and DC load are connected.

[0049] However, in existing technologies, the charging resistor is connected in series with the DC bus, such as... Figure 1 The DC bus live wire is connected to the right side of the bidirectional (rectifier / inverter) module 6. The charging circuit, consisting of the charging resistor and the bus capacitor, generally has a small current carrying capacity. After the DC bus voltage is established, i.e., after charging is complete, if a load is connected to the DC bus, the load will require a large current after startup. However, the charging circuit has a small current carrying capacity, which will very likely cause the charging circuit to burn out, resulting in the equipment failing to start normally and damaging the charging circuit.

[0050] The novel DC bus charging circuit proposed in this invention includes:

[0051] Rectifier module 1 has its input terminal connected to the live wire and neutral wire of the AC power grid, and its output terminal connected to the live wire and neutral wire of the DC bus. The function of this module is to convert the AC power from the power grid into DC power.

[0052] Charging resistor 2 is located on the line between rectifier module 1 and the live wire of DC bus, or on the line between rectifier module 1 and the neutral wire of DC bus, and is used to charge DC bus with DC power output from rectifier module 1.

[0053] In the above embodiments, a DC bus charging circuit is proposed, including a rectifier module and a charging resistor. One end of the circuit is connected to the AC power grid, and the other end is connected to the DC bus. The circuit samples the AC power, rectifies it, and charges the DC bus through the charging resistor. However, the charging circuit is independent of the DC bus. When the DC bus is connected to a load for startup, it will not affect the current of the charging circuit. Therefore, it can enable units such as photovoltaic-storage air conditioning systems to start normally when the DC bus is under load, improve the usability of the system, and protect the charging circuit from damage.

[0054] like Figure 1 As shown, it also includes: a first switch assembly 3, which is a double-pole switch, such as a DC contactor. When the DC contactor is opened, the charging circuit forms a path for bus charging. After charging is completed, the charging circuit is closed to disconnect the charging circuit.

[0055] The second switching assembly 4 is a three-stage switch located on the line between the output terminal of the rectifier module 1 and the DC bus. The first switching assembly 3 and the second switching assembly 4 are connected to the controller. When a load is connected to the DC bus, the controller controls the first switching assembly 3 to open and the second switching assembly 4 to close, charging the DC bus through the load. When no load is connected to the DC bus, the controller controls the first switching assembly 3 to close, charging the DC bus through the DC bus charging circuit. The above charging circuit allows for normal startup under DC bus load. After startup, the load charges the bus capacitor, establishing the bus voltage.

[0056] Preferably, the charging circuit further includes a current sensor 5, located on the line between the rectifier module 1 and the live wire of the DC bus, or on the line between the rectifier module 1 and the neutral wire of the DC bus, used to detect the charging current of the DC bus charging circuit; generally, soft-start circuits do not have a current sensor 5, which is a unique device of this charging circuit, used to detect the magnitude of the charging current and determine whether it is a load start or an no-load start. The controller is also connected to the current sensor 5, used to determine whether the DC bus is connected to a load by the current detected by the current sensor 5 after the first switch assembly 3 is closed. If the charging current is equal to the no-load charging current, it is determined to be a no-load start; if the charging current is greater than the no-load charging current, it is determined to be a load start. If it is a no-load start, then it is further determined whether the bus voltage has been charged to the rated value; if it has been charged to the rated value, it is determined that charging is complete and normal start is possible. If it is a load start, then the charging circuit is closed, the main circuit contactor is directly opened, and charging is performed directly without the need for charging resistor 2. Therefore, during no-load startup, it starts normally by charging; during load startup, it starts by charging using the characteristics of the load, disconnects the charging circuit, protects the charging circuit, and can also start normally under load.

[0057] Existing technology charges the DC bus with a resistor before startup, then starts the circuit after charging is complete, and then applies a load. This means starting under no-load conditions before applying a load. If there is a DC load on the bus, this method will damage the charging circuit. This application incorporates a current sensor in the charging circuit, allowing the charging current to determine whether the startup is under no-load or with a load on the bus. Different methods are used for different startup modes. Under no-load conditions, normal charging starts; under load conditions, the charging circuit is disconnected, and startup is performed directly (equivalent to charging using the load on the DC bus). Existing charging circuits do not consider whether there is a no-load or load condition; this application's charging circuit can identify whether there is a no-load or load condition and corresponds to different charging methods (soft-start method).

[0058] Example 2

[0059] In a preferred embodiment 2 of the present invention, an air conditioning unit is provided, including the DC bus charging circuit as described above. This air conditioning unit is a photovoltaic-storage air conditioning system, and its structural schematic diagram is shown below. Figure 1 As shown, a DC bus charging circuit is installed inside the air conditioning unit.

[0060] In the above embodiments, a DC bus charging circuit is proposed, including a rectifier module and a charging resistor. One end of the circuit is connected to the AC power grid, and the other end is connected to the DC bus. The circuit samples the AC power, rectifies it, and charges the DC bus through the charging resistor. However, the charging circuit is independent of the DC bus. When the DC bus is connected to a load for startup, it will not affect the current of the charging circuit. Therefore, it can enable units such as photovoltaic-storage air conditioning systems to start normally when the DC bus is under load, improve the usability of the system, and protect the charging circuit from damage.

[0061] Example 3

[0062] In a preferred embodiment 3 of the present invention, an air conditioning unit control method is provided, which is applied to the air conditioning unit in embodiment 2 described above. Specifically, Figure 2 An optional flowchart of the method is shown, such as Figure 2 As shown, the method includes the following steps S202-S208:

[0063] S202: Before the air conditioning unit starts, control the DC bus charging circuit to be turned on;

[0064] S204: Determine if a load is connected to the DC bus;

[0065] S206: When a load is connected to the DC bus, the DC bus charging circuit is disconnected.

[0066] S208: When the DC bus is not connected to a load, the DC bus is charged through the DC bus charging circuit.

[0067] In the above embodiments, a DC bus charging circuit is proposed, including a rectifier module and a charging resistor. One end of the circuit is connected to the AC power grid, and the other end is connected to the DC bus. The circuit samples the AC power, rectifies it, and charges the DC bus through the charging resistor. However, the charging circuit is independent of the DC bus. When the DC bus is connected to a load for startup, it will not affect the current of the charging circuit. Therefore, it can enable units such as photovoltaic-storage air conditioning systems to start normally when the DC bus is under load, improve the usability of the system, and protect the charging circuit from damage.

[0068] After the DC bus charging circuit is disconnected, the method further includes: controlling the air conditioning unit to start under load and charging the DC bus through the load; after charging the DC bus through the DC bus charging circuit, the method further includes: controlling the air conditioning unit to start under no-load after the DC bus charging is completed.

[0069] Furthermore, determining whether the DC bus is connected to a load includes: detecting the charging current of the DC bus charging circuit; determining whether the charging current is greater than the no-load charging current; if so, it is determined that the DC bus is connected to a load; otherwise, it is determined that the DC bus is not connected to a load. This application incorporates a current sensor in the charging circuit, allowing the charging current to determine whether the start-up is no-load or has a load on the bus. Different starting methods employ different approaches. Under no-load conditions, normal charging starts; under load, the charging circuit is disconnected, and the bus starts directly (equivalent to using the load on the DC bus for charging).

[0070] Specifically, controlling the DC bus charging circuit to be on includes: controlling the first switch assembly to close; controlling the DC bus charging circuit to be off includes: controlling the first switch assembly to open; controlling the air conditioning unit to start under load, or controlling the air conditioning unit to start under no-load, includes: controlling the second switch assembly to close. The first and second switch assemblies are initially in the off state by default.

[0071] In a preferred embodiment 2 of the present invention, another method for controlling an air conditioning unit is also provided, specifically... Figure 3 An optional flowchart of the method is shown, such as Figure 3 As shown, the method includes the following steps S301-S310:

[0072] S301: Charging has begun;

[0073] S302: Controls the first switch to engage;

[0074] S303: Is the charging current greater than the normal value? If yes, proceed to step S304; otherwise, proceed to step S306. If the charging current is equal to the no-load charging current, it is determined to be no-load start; if the charging current is greater than the no-load charging current, it is determined to be load start.

[0075] S304: Turn off the first switch;

[0076] S305: Turn on the second switch; if it is a load start, close the charging circuit and directly open the main circuit. There is no need to charge with a charging resistor, and it can start directly.

[0077] S306: Has the DC bus voltage reached the rated value? If yes, proceed to step S308; otherwise, proceed to step S307. If it is an unloaded start, continue to determine whether the bus voltage has been charged to the rated value. If it has been charged to the rated value, it is determined that the charging is complete and the start is normal.

[0078] S307: Delay for 1 second, then return to S306;

[0079] S308: Turn on the second switch;

[0080] S309: Close the first switch;

[0081] S310: Charging complete.

[0082] Different starting methods are used for different starting modes. Under no-load conditions, normal charging is performed for starting. Under load conditions, the charging circuit is disconnected and the system starts directly. This allows units such as photovoltaic-storage-air conditioning systems to start normally under DC bus load, improving system usability and protecting the charging circuit from damage.

[0083] Example 4

[0084] Based on the air conditioning unit control method provided in Embodiment 3 above, in a preferred embodiment 4 of the present invention, a storage medium containing computer-executable instructions is also provided, wherein the computer-executable instructions are used to execute the air conditioning unit control method as described above when executed by a computer processor.

[0085] In the above embodiments, a DC bus charging circuit is proposed, including a rectifier module and a charging resistor. One end of the circuit is connected to the AC power grid, and the other end is connected to the DC bus. The circuit samples the AC power, rectifies it, and charges the DC bus through the charging resistor. However, the charging circuit is independent of the DC bus. When the DC bus is connected to a load for startup, it will not affect the current of the charging circuit. Therefore, it can enable units such as photovoltaic-storage air conditioning systems to start normally when the DC bus is under load, improve the usability of the system, and protect the charging circuit from damage.

[0086] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not invented by the invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0087] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A DC bus charging circuit, characterized in that, The AC power grid is connected to the DC bus via a converter; the DC bus charging circuit includes: The rectifier module (1) has its input end connected to the live wire and neutral wire of the AC power grid, and its output end connected to the live wire and neutral wire of the DC bus. The charging resistor (2) is located on the line between the rectifier module (1) and the live wire of the DC bus, or on the line between the rectifier module (1) and the neutral wire of the DC bus, and is used to charge the DC bus with the DC power output by the rectifier module (1). The first switch assembly (3) is located on the line between the output terminal of the rectifier module (1) and the DC bus; the second switch assembly (4) is located on the line between the AC power grid and the converter; The controller is connected to the first switch assembly (3) and the second switch assembly (4) and is used to control the first switch assembly (3) to open and the second switch assembly (4) to close when the DC bus is connected to a load, so as to charge the DC bus through the load; and to control the first switch assembly (3) to close when the DC bus is not connected to a load, so as to charge the DC bus through the DC bus charging circuit. A current sensor (5) is located on the line between the rectifier module (1) and the live wire of the DC bus, or on the line between the rectifier module (1) and the neutral wire of the DC bus, for detecting the charging current of the DC bus charging circuit. The controller is also connected to the current sensor (5) to determine whether the DC bus is connected to a load by the current detected by the current sensor (5) after the first switch assembly (3) is closed.

2. The DC bus charging circuit according to claim 1, characterized in that, The first switch assembly (3) is a two-stage switch, and the second switch assembly (4) is a three-stage switch.

3. An air conditioning unit, characterized in that, Includes the DC bus charging circuit as described in any one of claims 1 to 2.

4. A method for controlling an air conditioning unit, characterized in that, The method, applied to a DC bus charging circuit as described in any one of claims 1 to 2, comprises: Before the air conditioning unit starts, the DC bus charging circuit is turned on. Determine if a load is connected to the DC bus; When a load is connected to the DC bus, the charging circuit of the DC bus is disconnected. When the DC bus is not connected to a load, the DC bus is charged through the DC bus charging circuit.

5. The method according to claim 4, characterized in that, After the DC bus charging circuit is disconnected, the method further includes: controlling the air conditioning unit to start under load, and charging the DC bus through the load; After charging the DC bus through the DC bus charging circuit, the method further includes: controlling the air conditioning unit to start under no-load after the DC bus charging is completed.

6. The method according to claim 4, characterized in that, The determination of whether the DC bus is connected to a load includes: Detect the charging current of the DC bus charging circuit; Determine whether the charging current is greater than the no-load charging current; If so, it is determined that the DC bus is connected to a load; otherwise, it is determined that the DC bus is not connected to a load.

7. The method according to claim 5, characterized in that, Controlling the DC bus charging circuit to conduct includes: controlling the first switch assembly to close; Controlling the DC bus charging circuit to disconnect includes: controlling the first switching assembly to disconnect; Controlling the air conditioning unit to start under load, or controlling the air conditioning unit to start under no-load, includes: controlling the second switch assembly to close.

8. A storage medium containing computer-executable instructions, characterized in that, The computer-executable instructions, when executed by a computer processor, are used to perform the air conditioning unit control method as described in any one of claims 4 to 7.

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