Power supply circuit compatible with low voltage ride through and grid-connected and off-grid device

Abstract

The utility model relates to a power supply circuit compatible with low voltage ride through and a grid-connected and off-grid device, the power supply circuit is provided with a rectification voltage reduction module capable of providing main power supply voltage and an auxiliary power supply module capable of providing auxiliary power supply voltage, and when a power grid is normal, the rectification voltage reduction module and the auxiliary power supply module can provide power supply voltage for a power supply output end at the same time; and when the power grid is abnormal, such as a low-voltage fault, the auxiliary power supply module can also provide power supply voltage for the power supply output end based on the direct current source, so that the applied equipment can realize low-voltage ride through when the power grid has the low-voltage fault, and the off-grid is avoided.

Description

Technical Field

[0001] The present application belongs to the field of circuit technology, and in particular relates to a power supply circuit and a grid-connected and off-grid device compatible with low voltage ride-through. Background Art

[0002] With rising industry standards, grid-connected equipment such as photovoltaic inverters must operate with high reliability and low-voltage ride-through capabilities. In the event of a low-voltage grid fault, the photovoltaic inverter must remain connected for a certain period of time and must also provide reactive power support. Typically, photovoltaic inverters are paired with a distribution box (also known as a backup box / device) for energy scheduling and power distribution. However, if the grid fails, the contactors within the distribution box will disconnect, making it unable to support low-voltage ride-through. Utility Model Content

[0003] The purpose of this application is to provide a power supply circuit and grid-connected / off-grid device compatible with low voltage ride-through, aiming to solve the problem that the distribution box cannot support low voltage ride-through when the power grid fails.

[0004] In a first aspect, an embodiment of the present application provides a power supply circuit compatible with low voltage ride-through, wherein the power supply circuit is used to power a contactor coil, and the contactor is used to control the grid connection or disconnection of a grid-connected device, and the power supply circuit includes a rectifier and step-down module, an auxiliary power supply module, and a power supply output terminal;

[0005] The power supply output end is connected to the contactor coil, and is used to supply power to the contactor coil to close the contactor;

[0006] The input end of the rectifier and buck module is connected to the power grid, and the output end of the rectifier and buck module is connected to the power supply output end and is used to output the main power supply voltage;

[0007] The output end of the auxiliary power supply module is connected to the power supply output end and is used to provide an auxiliary power supply voltage.

[0008] In an optional embodiment, the rectification and voltage reduction module includes a rectification unit and a voltage reduction unit;

[0009] The input end of the rectifier unit constitutes the input end of the rectifier-step-down module, the output end of the rectifier unit is connected to the input end of the step-down unit, and the output end of the step-down unit constitutes the output end of the rectifier-step-down module; or

[0010] The input end of the step-down unit constitutes the input end of the rectifier-step-down module, the output end of the step-down unit is connected to the input end of the rectifier unit, and the output end of the rectifier unit constitutes the output end of the rectifier-step-down module.

[0011] In an optional embodiment, the voltage reduction unit includes a first resistor, a second resistor and a first capacitor;

[0012] The first end of the first resistor is connected to the input end of the step-down unit, the second end of the first resistor is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the output end of the step-down unit, and the second resistor is connected in parallel with the first capacitor.

[0013] In an optional embodiment, a starting module is further included. The starting module is connected in parallel with the first capacitor, and the starting module is configured to be turned on when power is supplied from the power grid and to be turned off after a period of time.

[0014] In an optional embodiment, the startup module includes a third resistor and a first switch connected in series, and the resistance of the third resistor is smaller than the resistance of the second resistor.

[0015] In an optional embodiment, the step-down unit further includes a second switch, and the second switch is connected in series to the input end of the step-down unit.

[0016] In an optional embodiment, a first unidirectional conduction module is further included, wherein the input end of the first unidirectional conduction module is connected to the positive electrode of the output end of the auxiliary power supply module, and the output end of the first unidirectional conduction module is connected to the positive electrode of the power supply output end.

[0017] In an optional embodiment, a second unidirectional conduction module is further included, wherein the input end of the second unidirectional conduction module is connected to the negative pole of the power supply output end, and the output end of the second unidirectional conduction module is connected to the positive pole of the power supply output end.

[0018] In an optional embodiment, a third switch is further included, and the third switch is connected in series with the first unidirectional conduction module.

[0019] In the second aspect, an embodiment of the present application provides a grid-connected and off-grid device, comprising a power supply circuit and a contactor compatible with low voltage ride-through as described above, the contactor comprising a contactor coil and a contact switch controlled by the contactor coil to be turned on and off, the power supply output end of the power supply circuit being connected to the contactor coil, the first end of the grid-connected and off-grid device being used to be connected to the power grid, the second end of the grid-connected and off-grid device being used to be connected to a grid-connected device, and the contact switch being connected between the first end and the second end.

[0020] Compared with the related art, the embodiments of the present application have the following advantages: a power supply circuit configuration compatible with low voltage ride-through can provide a rectifier and step-down module for the main power supply voltage and an auxiliary power supply module for the secondary power supply voltage. When the power grid is normal, the rectifier and step-down module and the auxiliary power supply module can simultaneously provide power supply voltage to the power supply output end. When the power grid is abnormal, such as a low voltage fault, the auxiliary power supply module can also provide power supply voltage to the power supply output end based on a DC source, thereby meeting the requirements of the applied equipment to achieve low voltage ride-through when a low voltage fault occurs in the power grid, thereby avoiding disconnection from the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the solar storage system structure;

[0022] Figure 2 A schematic diagram of the structure of a low voltage ride-through compatible power supply circuit provided in one embodiment of the present application;

[0023] Figure 3 for Figure 2 A structural schematic diagram of an embodiment of a rectifier and voltage-reducing module in a power supply circuit is shown;

[0024] Figure 4 for Figure 2 A structural schematic diagram of an embodiment of a rectifier and voltage-reducing module in a power supply circuit is shown;

[0025] Figure 5 A circuit diagram of a low voltage ride-through compatible power supply circuit provided in one embodiment of the present application;

[0026] Figure 6 A circuit diagram of a low voltage ride-through compatible power supply circuit provided in one embodiment of the present application;

[0027] Figure 7 A schematic structural diagram of an on-grid and off-grid device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0029] It should be noted that when an element is referred to as being “connected to” another element, it can be directly connected to the another element or indirectly connected to the another element.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0031] like Figure 1 As shown, Figure 1 It is a schematic diagram of the application scenario of the photovoltaic storage system provided in the present application. The photovoltaic storage system provided in the present application may include a DC power supply, a power converter 11 and a distribution box 12. Among them, the DC power supply may be a photovoltaic array 13, and the photovoltaic array 13 is composed of a plurality of photovoltaic modules connected in series or in parallel, and the output end of the photovoltaic module can be connected to a DC input end of the power converter 11. The DC power supply can also be an energy storage battery 14. Here, the above-mentioned power converter 11 may include a DC conversion circuit and an inverter circuit, the input end of the DC conversion circuit can be connected to the above-mentioned photovoltaic array 13, the output end of the DC conversion circuit and the energy storage battery 14 can be connected to the input end of the inverter circuit, and the output end of the inverter circuit is used to connect to the first AC interface of the distribution box 12, and the second AC interface of the above-mentioned distribution box 12 is used to connect to the power grid 16. In addition to the first AC interface connected to the power converter 11 and the second AC interface connected to the power grid, the distribution box 12 can also be provided with multiple load interfaces for connecting to loads, such as Figure 1 The backup load 15 and the non-backup load 17 are shown in FIG.

[0032] When the voltage output by the power grid 16 is not lower than the voltage threshold, the above-mentioned distribution box 12 can conduct the connection between the power converter 11 and the power grid 16 according to actual needs or specific operations, that is, the power converter 11 operates in the grid-connected mode. When the power converter 11 is in the grid-connected mode, the power converter 11 can transform the DC power provided by the photovoltaic array 13 through the DC conversion circuit, and invert the transformed DC power through the inverter circuit. The AC power obtained by the power converter 11 after the inversion conversion and the AC power from the power grid 16 are used to supply power to the backup load 15 and the non-backup load 17. In addition, the DC power provided by the DC conversion circuit can also charge the energy storage battery 14. When the energy storage battery 14 is fully charged, the excess energy can be fed to the power grid 16 to realize power benefits.

[0033] When the voltage output by the power grid 16 is lower than the voltage threshold, the distribution box 12 disconnects the input of the power grid 16, so that the power converter 11 operates in off-grid mode. When the backup load 15 and the non-backup load 17 are AC devices and the power converter 11 is in off-grid mode, the power converter 11 can transform the DC power provided by the photovoltaic array 13 through the DC conversion circuit, and invert the transformed DC power or the DC power provided by the energy storage battery 14 through the inverter circuit, so as to output the AC power obtained after the inversion conversion to the backup load 15 for power supply. In the home power supply scenario, the backup load 15 can be an important load in the user's home, such as household appliances, alarm equipment, etc., which will not be powered off even when the power grid 16 is out of power. The non-backup load 17 can be a non-important load in the user's home, such as a charging pile, etc., which will not be powered when the power grid 16 is out of power, so as to ensure that the backup load 15 can be powered for a longer time. In addition, when the distribution box 12 cannot automatically connect the power converter 11 to the power grid 16 , the bypass circuit breaker can be manually closed to restore power supply to the backup load 15 and the non-backup load 17 .

[0034] In some embodiments, Figure 1 After the DC power provided by the photovoltaic array 13 is transformed by the DC conversion circuit in the power converter 11, the energy storage battery 14 can be charged based on the DC power output by the power converter 11. Figure 1 In the application scenario shown, the above-mentioned distribution box 12 draws power from the power grid 16. When the voltage of the power grid 16 is normal, the contactor in the distribution box 12 is energized based on the power supply of the power grid 16 to achieve conduction between the power converter 11 and the power grid 16. Alternatively, when it is detected that the voltage of the power grid 16 is too low, the contactor in the distribution box 12 is disconnected to achieve disconnection between the power converter 11 and the power grid 16. In some countries, the voltage of the power grid 16 has a low voltage ride-through situation, that is, the voltage of the power grid 16 drops to a low voltage and then recovers after a certain period of time. During this process, the power converter 11 is required to maintain a grid-connected operating state. However, the driving voltage of the contactor in the main circuit switch of the distribution box 12 is provided by the voltage of the power grid 16. In the low voltage ride-through scenario of the power grid 16, the contactor cannot be maintained in a closed state, the power converter 11 cannot operate in the grid-connected mode, and the working reliability of the power converter 11 under low voltage ride-through is low.

[0035] See also Figure 2 Some embodiments of the present application provide a power supply circuit 200 compatible with low voltage ride-through, the power supply circuit 200 is used to power a contactor coil 100, and the contactor is used to control the connection or disconnection of a grid-connected device.

[0036] The power supply circuit 200 includes a rectifier and step-down module 210, an auxiliary power supply module 220, and a power supply output terminal Vout. The power supply output terminal Vout is connected to the contactor coil 100 and is used to supply power to the contactor coil 100 to close the contactor. The input terminal of the rectifier and step-down module 210 is connected to the power grid 16, and the output terminal of the rectifier and step-down module 210 is connected to the power supply output terminal Vout and is used to output the main power supply voltage. The output terminal of the auxiliary power supply module 220 is connected to the power supply output terminal Vout and is used to provide an auxiliary power supply voltage.

[0037] Generally, the grid-connected device is, for example, the power converter 11. The auxiliary power module 220 includes, for example, a flyback switching power supply, which converts AC power from the grid 16 or the power converter 11 into DC power to power the system.

[0038] The auxiliary power supply module 220 is used to convert AC power from the power grid 16 or the power converter 11 into DC power, providing a supply voltage for the power output terminal Vout. When the power grid 16 is normal, the rectifier and step-down module 210 and the auxiliary power supply module 220 can simultaneously provide a supply voltage to the power output terminal Vout to power the contactor coil 100. However, when the power grid 16 is abnormal, such as when a low voltage fault occurs, the auxiliary power supply module 220 can still convert the AC power from the power converter 11 into DC power to power the contactor coil 100, meeting the grid connection requirements of the grid-connected equipment when a low voltage ride-through occurs on the power grid 16, and preventing disconnection.

[0039] See also Figure 3 and Figure 4 In some embodiments, the rectifier and buck module 210 includes a rectifier unit 211 and a buck unit 212. The rectifier unit 211 and the buck unit 212 are connected in series between the input and output ends of the rectifier and buck module 210.

[0040] See also Figure 3 In some embodiments, the input end of the rectifier unit 211 constitutes the input end of the rectifier-step-down module 210, the output end of the rectifier unit 211 is connected to the input end of the step-down unit 212, and the output end of the step-down unit 212 constitutes the output end of the rectifier-step-down module 210. The rectifier unit 211 rectifies the alternating current (AC) Vac from the power grid 16, and the step-down unit 212 steps down the rectified DC power and outputs it to the contactor coil 100.

[0041] See also Figure 4In some embodiments, the input end of the step-down unit 212 constitutes the input end of the rectifier-step-down module 210, the output end of the step-down unit 212 is connected to the input end of the rectifier unit 211, and the output end of the rectifier unit 211 constitutes the output end of the rectifier-step-down module 210. The step-down unit 212 steps down the AC power Vac from the power grid 16 and outputs it. The rectifier unit 211 rectifies the stepped-down AC power into DC power and outputs it to the contactor coil 100.

[0042] See also Figure 5 and Figure 6 In some embodiments, the rectifier unit 211 is a full-bridge rectifier circuit including diodes D3, D4, D5, and D6. In other embodiments, the rectifier unit 211 can also be configured as a half-wave rectifier circuit or other rectifier circuits. In some embodiments, the step-down unit 212 includes a first resistor R1, a second resistor R2, and a first capacitor C1. The first end of the first resistor R1 is connected to (or constitutes) the input end of the step-down unit 212, the second end of the first resistor R1 is connected to the first end of the first capacitor C1, the second end of the first capacitor C1 is connected to (or constitutes) the output end of the step-down unit 212, and the second resistor R2 is connected in parallel with the first capacitor C1.

[0043] Among them, the first resistor R1 plays a current limiting role. Based on the DC-isolating and AC-passing characteristics of the first capacitor C1, the voltage after the current limiting by the first resistor R1 is significantly reduced after passing through the first capacitor C1. The second resistor R2 plays a discharge / consumption role. When the first capacitor C1 is full, it is discharged through the second resistor R2. When the discharge reaches a certain value, the voltage charges the first capacitor C1 to achieve a cycle, and the main power supply voltage is output to maintain power supply to the contactor coil 100. The first resistor R1 is generally a winding resistor or a cement resistor, and the value generally ranges from 0-50 ohms. It is used to prevent the contactor coil 100 from generating a large current when it is attracted, thereby damaging the other components of the circuit. The value of the second resistor R2 is in the kilo-ohm level, and is specifically used in conjunction with the first capacitor C1 to achieve a resistance-capacitance voltage reduction effect.

[0044] See also Figure 5 and Figure 6 In some embodiments, the power supply circuit 200 further includes a starting module 240 connected in parallel with the first capacitor C1. The starting module 240 is configured to be turned on when power is supplied by the power grid 16 and to be turned off after a period of time. The period of time refers to the time from when power is supplied by the power grid 16 (i.e., when the second switch K2 is closed) to when the contactor coil 100 is stably engaged. The starting module 240 can be controlled by a controller in the power distribution box 12.

[0045] In some embodiments, the startup module 240 includes a third resistor R3 and a first switch K1 connected in series. The resistance of the third resistor R3 is less than the resistance of the second resistor R2. The third resistor R3 is generally a wire wound resistor or a cement resistor, and its value generally ranges from 30 to 500 ohms.

[0046] See also Figure 5 and Figure 6 In some embodiments, the step-down unit 212 further includes a second switch K2 connected in series to the input terminal of the step-down unit 212. The second switch K2 is used to control whether the main power supply voltage provided by the power grid 16 is used to power the contactor coil 100.

[0047] See also Figure 5 and Figure 6 In some embodiments, the power supply circuit 200 further includes a first unidirectional conduction module D1, the input end of the first unidirectional conduction module D1 is connected to the positive output end of the auxiliary power supply module 220, and the output end of the first unidirectional conduction module D1 is connected to the positive output end of the power supply Vout.

[0048] In one embodiment, the first unidirectional conduction module D1 includes a diode, the anode and cathode of which respectively constitute the input and output terminals of the first unidirectional conduction module D1. The first unidirectional conduction module D1 can prevent the grid voltage from flowing back through the auxiliary power module 220 and thereby damaging the auxiliary power module 220.

[0049] See also Figure 5 and Figure 6 In some embodiments, the power supply circuit 200 further includes a second unidirectional conduction module D2, the input end of the second unidirectional conduction module D2 is connected to the negative pole of the power supply output terminal Vout, and the output end of the second unidirectional conduction module D2 is connected to the positive pole of the power supply output terminal Vout.

[0050] In one embodiment, the second unidirectional conducting module D2 includes a diode, whose anode and cathode respectively constitute the input and output terminals of the second unidirectional conducting module D2. The second unidirectional conducting module D2 can clamp the voltage of the contactor coil 100. When the contactor is closed, the contactor coil 100 generates a back electromotive force, which is prevented from generating a negative voltage spike by the second unidirectional conducting module D2.

[0051] See also Figure 5 and Figure 6 In some embodiments, the power supply circuit 200 further includes a third switch K3 , which is connected in series with the first unidirectional conduction module D1 .

[0052] In one embodiment, the first, second and third switches K1 , K2 and K3 may be devices such as relays and MOS tubes that can realize switching functions, and the switching functions may be controlled by a controller of the distribution box 12 .

[0053] See also Figure 5 In some embodiments, the operating principle is that when the power grid is normally powered, the auxiliary power module 220 is powered, the first, second, and third switches K1, K2, and K3 are closed, and the grid-side voltage Vac is rectified into a steamed wave after passing through the rectifier unit 211. At this time, after the current is limited by the first resistor R1, due to the low resistance of the third resistor R3, most of the current flows through the third resistor R3 and the first switch K1 branch to excite the contactor coil 100, thereby attracting the coil. After stabilization, the first switch K1 is turned off, and the output voltage of the rectifier unit 211 is a steamed wave. Due to the DC-blocking and AC-passing characteristics of the first capacitor C1, the voltage after passing through the first capacitor C1 is significantly reduced, maintaining the power supply (main power supply voltage) for the contactor coil 100. When the first capacitor C1 is full, it is discharged through the second resistor R2. When the discharge reaches a certain value, the rectified voltage charges the first capacitor C1 again, thus completing the cycle.

[0054] The auxiliary power supply voltage output by auxiliary power module 220 powers contactor coil 100 through the branch containing third switch K3, providing dual power supply protection. When an abnormality occurs in grid 16, the input voltage of grid 16 decreases, and the rectified ripple voltage cannot meet the operating requirements of contactor coil 100. At this time, auxiliary power module 220 powers contactor coil 100, keeping the contactor connected to the grid through the backup power box, and continuing to supply backup load 15 and / or provide reactive power compensation for grid 16.

[0055] See also Figure 7 An embodiment of the present application further provides a grid-connected or off-grid device 10, comprising the above-mentioned low voltage ride-through compatible power supply circuit 200 and a contactor, wherein the contactor comprises a contactor coil 100 and a contact switch 300 whose on / off is controlled by the contactor coil 100, a power supply output terminal Vout of the power supply circuit 200 is connected to the contactor coil 100, a first terminal of the grid-connected or off-grid device 10 is used to be connected to the power grid 16, a second terminal of the grid-connected or off-grid device 10 is used to be connected to a grid-connected device, and the contact switch 300 is connected between the first terminal and the second terminal.

[0056] In some embodiments, the grid-connected and off-grid device 10 is used in, for example, a distribution box 12 , and the grid-connected equipment includes the above-mentioned power converter 11 and the like.

[0057] In another embodiment, the grid-connected / off-grid device 10 may also be applied to a grid-connected device, where the grid-connected device includes the power converter 11 and the grid-connected / off-grid device as described above.

[0058] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A power supply circuit compatible with low voltage ride-through, characterized in that: The power supply circuit is used to supply power to the contactor coil, and the contactor is used to control the grid connection or disconnection of the grid-connected equipment. The power supply circuit includes a rectifier and step-down module, an auxiliary power supply module and a power supply output terminal; The power supply output end is connected to the contactor coil, and is used to supply power to the contactor coil to close the contactor; The input end of the rectifier and buck module is connected to the power grid, and the output end of the rectifier and buck module is connected to the power supply output end and is used to output the main power supply voltage; The output end of the auxiliary power supply module is connected to the power supply output end and is used to provide an auxiliary power supply voltage.

2. The power supply circuit according to claim 1, wherein: The rectifier and voltage reduction module includes a rectifier unit and a voltage reduction unit; The input end of the rectifier unit constitutes the input end of the rectifier-step-down module, the output end of the rectifier unit is connected to the input end of the step-down unit, and the output end of the step-down unit constitutes the output end of the rectifier-step-down module; or The input end of the step-down unit constitutes the input end of the rectifier-step-down module, the output end of the step-down unit is connected to the input end of the rectifier unit, and the output end of the rectifier unit constitutes the output end of the rectifier-step-down module.

3. The power supply circuit according to claim 2, wherein: The step-down unit includes a first resistor, a second resistor and a first capacitor; The first end of the first resistor is connected to the input end of the step-down unit, the second end of the first resistor is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the output end of the step-down unit, and the second resistor is connected in parallel with the first capacitor.

4. The power supply circuit according to claim 3, wherein: It also includes a starting module, which is connected in parallel with the first capacitor. The starting module is configured to be turned on when the power grid supplies power and to be turned off after a period of time.

5. The power supply circuit according to claim 4, wherein: The startup module includes a third resistor and a first switch connected in series, and a resistance value of the third resistor is smaller than a resistance value of the second resistor.

6. The power supply circuit according to any one of claims 2 to 5, characterized in that: The step-down unit further includes a second switch connected in series to the input end of the step-down unit.

7. The power supply circuit according to claim 1, wherein: It also includes a first one-way conducting module, wherein the input end of the first one-way conducting module is connected to the positive electrode of the output end of the auxiliary power supply module, and the output end of the first one-way conducting module is connected to the positive electrode of the power supply output end.

8. The power supply circuit according to claim 1, wherein: It also includes a second one-way conducting module, wherein the input end of the second one-way conducting module is connected to the negative pole of the power supply output end, and the output end of the second one-way conducting module is connected to the positive pole of the power supply output end.

9. The power supply circuit according to claim 7, wherein: The invention further comprises a third switch, wherein the third switch is connected in series with the first unidirectional conduction module.

10. A grid-connected and off-grid device, characterized in that: It comprises a low voltage ride-through compatible power supply circuit and contactor as described in any one of claims 1 to 9, the contactor comprising a contactor coil and a contact switch whose on and off is controlled by the contactor coil, the power supply output end of the power supply circuit is connected to the contactor coil, the first end of the grid-connected and off-grid device is used to be connected to the grid, the second end of the grid-connected and off-grid device is used to be connected to the grid-connected equipment, and the contact switch is connected between the first end and the second end.

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