Power supply circuit compatible with low voltage ride through, standby power device and power conversion device

Abstract

The utility model relates to a power supply circuit compatible with low voltage ride through, a standby power device and a power conversion device, and the power supply circuit is provided with a voltage transformation module capable of providing main power supply voltage, a rectification module and an auxiliary power supply module capable of providing auxiliary power supply voltage. The voltage transformation module, the rectification module and the auxiliary power supply module can provide power supply voltage for the power supply output end at the same time, and the auxiliary power supply module can provide the power supply voltage for the power supply output end based on the direct current source when a power grid is abnormal such as a low-voltage fault, so that low-voltage ride-through is realized when the power grid is in the low-voltage fault, and the power supply efficiency is improved. And net separation 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, a backup power device, and a power conversion device compatible with low voltage ride-through. Background Art

[0002] With the increasing number of photovoltaic inverters and the improvement of industry standards, inverters must be highly reliable and have low-voltage ride-through capabilities for normal operation. When a low-voltage fault occurs on the power grid, the photovoltaic inverter must remain connected to the grid for a certain period of time and must also provide reactive power support. Generally, photovoltaic inverters are usually paired with a distribution box (also known as a backup box) for energy scheduling and power distribution. However, if the power grid fails, the contactors inside the distribution box will disengage and cannot support low-voltage ride-through. Utility Model Content

[0003] The purpose of this application is to provide a power supply circuit, backup power device and power conversion 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 transformer module, a rectifier module, and an auxiliary power supply module;

[0005] The input end of the transformer module is connected to the power grid, the output end of the transformer module is connected to the input end of the rectifier module, and the output end of the rectifier module is connected to the power supply output end of the power supply circuit for outputting the main power supply voltage;

[0006] The output end of the auxiliary power supply module is connected to the power supply output end for providing an auxiliary power supply voltage;

[0007] The power supply output end is connected to the contactor coil and is used to supply power to the contactor coil.

[0008] In an optional embodiment, a first switch module is further included, and the first switch module is connected in series to the output end of the rectifier module.

[0009] 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.

[0010] In an optional embodiment, a second switch module is further included, and the second switch module is connected in series with the first unidirectional conduction module.

[0011] In an optional embodiment, the first unidirectional conducting module includes a diode, and the second switching module includes a relay or a semiconductor transistor.

[0012] 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.

[0013] In an optional embodiment, the second unidirectional conducting module includes a diode.

[0014] In an optional embodiment, the rectifier module includes a half-wave rectifier circuit or a full-bridge rectifier circuit.

[0015] In the second aspect, an embodiment of the present application provides a backup power device, including a contactor and a power supply circuit compatible with low voltage ride-through as described above, the contactor including 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 is connected to the contactor coil, the first end of the backup power device is used to be connected to the power grid, the second end of the backup power device is used to be connected to the power conversion device, and the contact switch is connected in series between the first end and the second end.

[0016] In a third aspect, an embodiment of the present application provides a power conversion device, comprising a power converter, a power supply circuit compatible with low voltage ride-through as described above, and a contactor, wherein the contactor comprises a coil and a contact switch whose on and off is controlled by the contactor coil, the AC end of the power converter is connected to the power grid through the contact switch, and the power supply output end of the power supply circuit is connected to the contactor coil.

[0017] Compared with the related art, the embodiments of the present application have the following advantages: the power supply circuit configuration compatible with low voltage ride-through can provide a transformer module, a rectifier module and an auxiliary power supply module for providing a secondary power supply voltage. When the power grid is normal, the transformer module, the rectifier module and the auxiliary power supply module can simultaneously provide the 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 the power supply voltage to the power supply output end based on a DC source, so as to meet 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

[0018] Figure 1 Schematic diagram of the solar storage system structure;

[0019] 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;

[0020] Figure 3A circuit diagram of a low voltage ride-through compatible power supply circuit provided in one embodiment of the present application;

[0021] Figure 4 A schematic structural diagram of an on-grid and off-grid device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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, wherein 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.

[0026] 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.

[0027] 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 .

[0028] 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 1In 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.

[0029] See also Figure 2 An embodiment of the present application provides a power supply circuit 200 compatible with low voltage ride-through. The power supply circuit 200 is used to power a contactor coil 100. The contactor is used to control the grid connection or off-grid connection of grid-connected equipment. The power supply circuit 200 includes a transformer module 210, a rectifier module 220 and an auxiliary power supply module 230.

[0030] The input of the transformer module 210 is connected to the power grid 16, and the output of the transformer module 210 is connected to the input of the rectifier module 220. The output of the rectifier module 220 is connected to the power supply output terminal Vout of the power supply circuit 200 for outputting the main power supply voltage. The output of the auxiliary power supply module 230 is connected to the power supply output terminal Vout for providing an auxiliary power supply voltage. The power supply output terminal Vout is connected to the contactor coil 100 for supplying power to the contactor coil 100.

[0031] Generally, the grid-connected device is, for example, the power converter 11. The auxiliary power module 230 includes, for example, a flyback switching power supply, which converts AC power from the grid 16 or the power converter 11 into DC power as the auxiliary power supply voltage.

[0032] The auxiliary power supply module 230 is used to convert the AC power from the power grid 16 or the power converter 11 into DC power, and provide a power supply voltage for the power output terminal Vout. When the power grid 16 is normal, the transformer module 210, the rectifier module 220 and the auxiliary power supply module 230 can simultaneously provide a power supply voltage to the power output terminal Vout. When the power grid 16 is abnormal, such as when a low voltage fault occurs, since the auxiliary power supply module 230 can draw power from the power converter 11, the auxiliary power supply module 230 can also provide a power supply voltage to the contactor coil 100, so that the contactor remains closed, meeting the requirement that the grid-connected equipment remain connected to the grid when a low voltage ride-through occurs in the grid.

[0033] See also Figure 3 In some embodiments, the voltage transformation module 210 includes a transformer T1. The output voltage of the transformer T1 should meet the following requirements:

[0034] First, determine the overvoltage and undervoltage protection range of the inverter circuit of the power converter 11, and leave a margin of 20V between the upper and lower limits on this basis to prevent grid voltage fluctuations from causing the contactor coil 100 to fail to attract;

[0035] Determine the range of the grid voltage after step-down rectification, where the value is as close as possible to the rated voltage of the contactor coil 100, so as to ensure that the contactor coil 100 is attracted and maintained when the rectifier module 220 outputs steamed wave power supply, and determine the transformer turns ratio.

[0036] The contactor coil 100 pull-in voltage range should be as wide as possible, reaching 0.6-1.2Un (Un is the rated working voltage of the coil). Confirm that the voltage range after transformer T1 transformation is greater than the over-voltage and under-voltage protection range of the inverter circuit, and leave a 20V redundant design to ensure that the contactor can be disengaged in the event of over-voltage or under-voltage of the inverter circuit.

[0037] See also Figure 3 In some embodiments, the power supply circuit 200 further includes a first switch module K1 , which is connected in series to the output end of the rectifier module 220 .

[0038] The first switch module K1 includes a relay or a semiconductor transistor.

[0039] See also Figure 3 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 230, and the output end of the first unidirectional conduction module D1 is connected to the positive output end of the power supply Vout.

[0040] The first unidirectional conducting module D1 can prevent the grid voltage from causing backflow to the auxiliary power module 230 after rectification and voltage reduction, thereby preventing the auxiliary power module 230 from being damaged.

[0041] See also Figure 3 In some embodiments, the power supply circuit 200 further includes a second switch module K2 , which is connected in series with the first unidirectional conduction module D1 .

[0042] In some embodiments, the first unidirectional conducting module D1 includes a diode, and the second switching module K2 includes a relay or a semiconductor transistor.

[0043] When the photovoltaic storage system is off-grid, the first and second switch modules K1 and K2 are turned off simultaneously to disconnect from the grid 16 , and the auxiliary power module 230 can continue to supply power to the contactor coil 100 .

[0044] In some embodiments, the first and second switch modules K1 and K2 can be controlled on and off by a controller of the distribution box 12 based on the power supply of the auxiliary power module 230 .

[0045] See also Figure 3 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.

[0046] In some embodiments, the second unidirectional conduction module D2 includes a diode. The second unidirectional conduction module D2 can clamp the voltage of the contactor coil 100. When the contactor is turned off, the contactor coil 100 generates a back electromotive force, which is prevented from generating a negative voltage spike by the second unidirectional conduction module D2.

[0047] In some embodiments, the rectifier module 220 includes a half-wave rectifier circuit or a full-bridge rectifier circuit. Figure 3 In the illustrated embodiment, the rectifier module 220 is a full-bridge rectifier circuit.

[0048] In some embodiments, the contactor coil 100 is a DC coil. Its operating principle is as follows: when the grid 16 is normal, the auxiliary power module 230 is powered, and the first and second switch modules K1 and K2 are energized. At this point, the grid-side voltage of the grid 16 is stepped down to a certain range by the transformer T1 and supplied to the contactor coil 100 via the rectifier module 220. At this point, the contactor is engaged and maintained. The auxiliary power supply voltage output by the auxiliary power module 230 and the main power supply voltage output by the rectifier module 220 simultaneously power the contactor coil 100. When the grid 16 is abnormal, such as when a low voltage ride-through occurs, the grid voltage decreases, causing the stepped-down and rectified steamed wave from the grid 16 to meet the operating requirements of the contactor coil 100. At this point, the auxiliary power supply voltage output by the auxiliary power module 230 powers the contactor coil 100, keeping the contactor engaged. The power converter 11 maintains grid connection during the low voltage ride-through through the distribution box 12, continuing to supply power to the backup load 15 and / or performing reactive power compensation for the grid 16.

[0049] See also Figure 4 An embodiment of the present application further provides a backup power device 10, comprising a contactor and a low voltage ride-through compatible power supply circuit 200 as described in any embodiment, wherein the contactor comprises a contactor coil 100 and a contact switch 300 whose on and off is controlled by the contactor coil 100, the power supply output terminal Vout of the power supply circuit 200 is connected to the contactor coil 100, the first end of the backup power device 10 is used to be connected to the power grid 16, the second end of the backup power device 10 is used to be connected to the power conversion device, and the contact switch 300 is connected in series between the first end and the second end.

[0050] The power conversion device may include Figure 1 The power converter 11 is shown.

[0051] The backup power device 10 can be used in, for example Figure 1 When applied to a photovoltaic storage system, when the photovoltaic storage system is operating normally, the contactor in the backup power device 10 of the embodiment of the present application adopts dual power supply. When a low voltage ride-through occurs in the power grid 16, the auxiliary power module 230 can continuously supply power to keep the contactor energized, that is, the power conversion device is not disconnected from the grid.

[0052] See also Figure 1 An embodiment of the present application further provides a power conversion device, including a power converter 11, a power supply circuit 200 compatible with low voltage ride-through as described in any of the above embodiments, and a contactor, the contactor including a contactor coil 100 and a contact switch 300 whose on / off is controlled by the contactor coil 100, the AC end of the power converter is connected to the power grid 16 through the contact switch 300, and the power supply output end Vout of the power supply circuit 200 is connected to the contactor coil 100.

[0053] When the power conversion device operates normally, the contactor is powered by dual power supplies. When a low voltage ride-through occurs in the power grid 16, the auxiliary power module 230 can continuously supply power to keep the contactor closed, that is, the power conversion device does not disconnect from the grid.

[0054] This embodiment and Figure 4 The difference of the illustrated embodiment is that the power supply circuit 200, contactor coil 100, and contact switch 300 are all provided within the same device as the power converter 11. This device itself can achieve off-grid and on-grid functionality without requiring a backup power supply, and can also maintain grid connection during low voltage ride-through.

[0055] 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 transformer module, a rectifier module and an auxiliary power supply module; The input end of the transformer module is connected to the power grid, the output end of the transformer module is connected to the input end of the rectifier module, and the output end of the rectifier module is connected to the power supply output end of the power supply circuit for outputting the main power supply voltage; The output end of the auxiliary power supply module is connected to the power supply output end for providing an auxiliary power supply voltage; The power supply output end is connected to the contactor coil and is used to supply power to the contactor coil.

2. The power supply circuit according to claim 1, wherein: The first switching module is further included, and the first switching module is connected in series to the output end of the rectifier module.

3. 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.

4. The power supply circuit according to claim 3, wherein: It also includes a second switch module, which is connected in series with the first unidirectional conduction module.

5. The power supply circuit according to claim 4, wherein: The first unidirectional conducting module includes a diode, and the second switching module includes a relay or a semiconductor transistor.

6. 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.

7. The power supply circuit according to claim 6, wherein: The second unidirectional conducting module includes a diode.

8. The power supply circuit according to claim 1, wherein: The rectifier module includes a half-wave rectifier circuit or a full-bridge rectifier circuit.

9. A backup power device, characterized in that: It includes a contactor and a low voltage ride-through compatible power supply circuit as described in any one of claims 1 to 8, the contactor includes 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 backup power device is used to be connected to the power grid, the second end of the backup power device is used to be connected to the power conversion device, and the contact switch is connected in series between the first end and the second end.

10. A power conversion device, characterized in that: It includes a power converter, a low voltage ride-through compatible power supply circuit as described in any one of claims 1 to 8, and a contactor, the contactor including a coil and a contact switch whose on and off is controlled by the contactor coil, the AC end of the power converter is connected to the power grid through the contact switch, and the power supply output end of the power supply circuit is connected to the contactor coil.

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