Grid-connected contactor control circuit and photovoltaic system

Abstract

The invention discloses a grid-connected contactor control circuit and a photovoltaic system, and belongs to the technical field of new energy power generation grid connection. The invention provides a grid-connected contactor control circuit, and the circuit comprises a normally-open main contact which is disposed in a grid-connected loop; the contactor coil is coupled with the normally open main contact; the input side of the power conversion circuit is electrically connected with a power grid, and the output side of the power conversion circuit is electrically connected with the contactor coil; the output end of the switching circuit is electrically connected with the contactor coil; and the direct-current auxiliary power supply is electrically connected with the input end of the switching circuit. According to the grid-connected contactor control circuit, the direct-current auxiliary power supply provides holding power for the contactor coil and maintains the voltage at the two ends of the contactor coil, so that when the voltage of a power grid drops, the contactor can still maintain suction, low voltage ride through is achieved, the circuit structure is simple, and the cost is low.

Description

Technical Field

[0001] The present application belongs to the technical field of new energy power generation and grid connection, and in particular, relates to a grid-connected contactor control circuit and a photovoltaic system. Background Art

[0002] With the rapid development of renewable energy generation technology, especially the widespread application of distributed energy such as wind power and photovoltaics, the power system has increasingly higher requirements for the stability of power generation equipment in the event of grid failure. The grid voltage may drop due to voltage fluctuations and other reasons, and recover after a period of time. This requires the grid-connected equipment to be able to maintain connection with the grid for a certain period of time after the grid voltage drops, waiting for the grid voltage to recover and achieve low voltage ride-through. At present, the control loop of the equipment used to achieve the low voltage ride-through function is complex and the implementation cost is high. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a grid-connected contactor control circuit and a photovoltaic system, in which when the grid voltage drops, a DC auxiliary power supply provides holding power for the contactor coil, and the contactor can still maintain the pull-in, realizing low voltage ride-through, with a simple circuit structure and low cost.

[0004] In a first aspect, the present application provides a grid-connected contactor control circuit, comprising: Normally open main contacts are set in the grid-connected circuit; The contactor coil is coupled with the normally open main contact; A power conversion circuit, wherein the input side of the power conversion circuit is electrically connected to the power grid, and the output side of the power conversion circuit is electrically connected to the contactor coil; A switch circuit, wherein an output end of the switch circuit is electrically connected to a contactor coil; The DC auxiliary power supply is electrically connected to the input end of the switch circuit.

[0005] According to the grid-connected contactor control circuit of the present application, a DC auxiliary power supply provides holding power for the contactor coil to maintain the voltage across the contactor coil, so that when the grid voltage drops, the contactor can still remain attracted to achieve low voltage ride-through. The circuit structure is simple and the cost is low.

[0006] According to one embodiment of the present application, the switch circuit includes: A first switch is arranged on a loop formed by a power conversion circuit and a contactor coil; The normally open auxiliary contact is set on the loop formed by the DC auxiliary power supply and the contactor coil. The normally open auxiliary contact follows the normally open main contact.

[0007] According to one embodiment of the present application, the switch circuit further includes: The normally closed auxiliary contact is set on the loop formed by the power conversion circuit and the contactor coil. The normally closed auxiliary contact follows the normally open main contact.

[0008] According to one embodiment of the present application, the grid-connected contactor control circuit further includes: A first transient voltage suppressor is provided, wherein a first end of the first transient voltage suppressor is electrically connected to a first end of the contactor coil, and a second end of the first transient voltage suppressor is electrically connected to a second end of the contactor coil.

[0009] According to one embodiment of the present application, the switch circuit includes: A first diode, wherein an anode of the first diode is electrically connected to a positive electrode of the DC auxiliary power supply, and a cathode of the first diode is electrically connected to a contactor coil.

[0010] According to one embodiment of the present application, the grid-connected contactor control circuit further includes: The second switch is arranged on the loop formed by the power grid and the power conversion circuit. The second switch is turned off when the voltage on the output side of the power conversion circuit drops, so that the first diode is forward-conducted.

[0011] According to one embodiment of the present application, the grid-connected contactor control circuit further includes: The third switch is connected in series with the contactor coil; The second transient voltage suppressor is connected in parallel with the third switch, or the second transient voltage suppressor is connected in parallel with the contactor coil and is electrically connected to an end of the third switch close to the contactor coil.

[0012] According to one embodiment of the present application, a power conversion circuit includes: A center-tapped transformer, wherein a primary winding of the center-tapped transformer is electrically connected to the power grid, and a center point of a secondary winding of the center-tapped transformer is electrically connected to a second end of a contactor coil; a second diode, wherein an anode of the second diode is electrically connected to a first end of a secondary winding of the center-tapped transformer, and a cathode of the second diode is electrically connected to a first end of a contactor coil; A third diode, an anode of the third diode is electrically connected to the second end of the secondary winding of the center-tapped transformer, and a cathode of the third diode is electrically connected to the first end of the contactor coil.

[0013] According to one embodiment of the present application, a power conversion circuit includes: The rectifier circuit has an AC side electrically connected to the power grid, and a DC side electrically connected to the contactor coil.

[0014] In a second aspect, the present application provides a photovoltaic system, which includes a contactor and the aforementioned grid-connected contactor control circuit, wherein the grid-connected contactor control circuit is electrically connected to the contactor.

[0015] According to the photovoltaic system of the present application, a DC auxiliary power supply provides holding power for the contactor coil to maintain the voltage across the contactor coil, so that when the grid voltage drops, the contactor can still remain attracted, achieving low voltage ride-through, with a simple circuit structure and low cost.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 is a structural block diagram of a grid-connected contactor control circuit provided in an embodiment of the present application; Figure 2 It is one of the circuit diagrams of the grid-connected contactor control circuit provided in the embodiment of the present application; Figure 3 This is the second circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application; Figure 4 This is the third circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application; Figure 5 This is the fourth circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application; Figure 6 This is the fifth circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application.

[0018] Reference numerals: Grid-connected contactor control circuit 100, power conversion circuit 110, rectifier circuit 111, switch circuit 120, DC auxiliary power supply 130, power grid 200, contactor coil KM, normally open auxiliary contact Ko, normally closed auxiliary contact Kc, first to third switches K1~K3, first to third diodes D1~D3, transient voltage suppressor TVS. DETAILED DESCRIPTION

[0019] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0020] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0021] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0022] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0023] With the large-scale access of renewable energy sources such as photovoltaic power generation and wind power generation to the power grid, the power system has increasingly higher requirements for the stability of power generation equipment in the event of a grid failure. The grid voltage may drop due to voltage fluctuations and other reasons, and recover after a period of time. This requires that the grid-connected equipment can maintain connection with the grid for a certain period of time after the grid voltage drops, waiting for the grid voltage to recover and achieve low voltage ride-through. At present, the control circuits used to achieve low voltage ride-through function equipment are complex and the implementation cost is high.

[0024] Reference Figure 1 , Figure 1The structural block diagram of the grid-connected contactor control circuit 100 provided by an embodiment of the present application is shown. One embodiment of the present application proposes a grid-connected contactor control circuit 100, which includes: a normally open main contact, a contactor coil KM, a power conversion circuit 110, a switch circuit 120 and a DC auxiliary power supply 130. The normally open main contact is arranged in the grid-connected loop; the contactor coil KM is coupled with the normally open main contact; the input side of the power conversion circuit 110 is electrically connected to the power grid 200, and the output side of the power conversion circuit 110 is electrically connected to the contactor coil KM; the output end of the switch circuit 120 is electrically connected to the contactor coil KM; and the DC auxiliary power supply 130 is electrically connected to the input end of the switch circuit 120.

[0025] The normally open main contact is set in the grid-connected circuit, and is mainly used to connect or disconnect the circuit between the grid 200 and the grid-connected equipment to ensure smooth and safe power transmission. The normally open main contact allows the grid-connected equipment to be smoothly connected to the grid 200 when the voltage of the grid 200 is stable, and when the voltage of the grid 200 is abnormal, it can respond quickly through the control circuit and disconnect from the grid 200 to protect the equipment from damage.

[0026] The contactor coil KM and the normally open main contact work through electromagnetic coupling. When the contactor coil KM is energized, the generated magnetic field will attract the normally open main contact to close, otherwise it will cause the normally open main contact to open, thereby achieving control of the grid-connected circuit.

[0027] The power conversion circuit 110 is electrically connected to the power grid 200 and the contactor coil KM, and is mainly used to convert the power provided by the power grid 200 into a voltage and current suitable for the operation of the contactor coil KM to ensure the stable operation of the circuit. The functions of the power conversion circuit 110 may include but are not limited to rectification, filtering and voltage stabilization, etc., to meet the working requirements of the contactor coil KM under different power grid 200 conditions.

[0028] The DC auxiliary power supply 130 may include a rectifier module. The AC side of the rectifier module is electrically connected to the power grid, and the DC side of the rectifier module is electrically connected to the input end of the switch circuit 120. The DC auxiliary power supply 130 is mainly used to provide stable DC power to ensure that power can still be provided to the contactor coil KM through the switch circuit 120 when the power grid 200 voltage fluctuates or is abnormal, so as to achieve low voltage ride-through.

[0029] The switch circuit 120 is electrically connected between the DC auxiliary power supply 130 and the contactor coil KM. When the switch circuit 120 is turned on, the DC auxiliary power supply 130 provides stable DC power to the contactor coil KM. When the switch circuit 120 is turned off, the loop between the DC auxiliary power supply 130 and the contactor coil KM is disconnected, and the DC auxiliary power supply 130 does not provide power to the contactor coil KM.

[0030] It should be noted that the DC voltage provided by the DC auxiliary power supply 130 is lower than the DC voltage at the output side of the power conversion circuit 110 when the voltage of the power grid 200 is normal, and is higher than the voltage of the contactor coil KM to maintain the normally open main contacts closed.

[0031] When the voltage of the power grid 200 is normal, the DC voltage on the output side of the power conversion circuit 110 provides electric energy for the contactor coil KM, which can close the normally open main contact; after the normally open main contact is closed, the switch circuit 120 can be controlled to be turned on, and the DC auxiliary power supply 130 provides electric energy for the contactor coil KM to maintain the normally open main contact closed. When the normally open main contact remains in a closed state, the DC auxiliary power supply 130 provides holding power for the contactor coil KM to maintain the voltage across the contactor coil KM. If the voltage of the power grid 200 drops, the rectifier module can still work, converting the electric energy of the power grid into direct current to maintain the contactor coil KM closed, and the contactor can still maintain the closed state, realizing low voltage ride-through, with a simple circuit structure and low cost. In addition, when the voltage of the power grid 200 is too high, the DC auxiliary power supply 130 can adjust the output voltage to stabilize within the voltage range that maintains the normally open main contact of the contactor closed, thereby avoiding damage to the grid-connected equipment due to the excessive voltage of the power grid 200.

[0032] According to the grid-connected contactor control circuit 100 of the present application, the DC auxiliary power supply 130 provides holding power for the contactor coil KM to maintain the voltage across the contactor coil KM, so that when the voltage of the power grid 200 drops, the contactor can still remain closed to achieve low voltage ride-through, with a simple circuit structure and low cost.

[0033] Reference Figure 2 and Figure 3 In some embodiments, the switch circuit includes a first switch K1 and a normally open auxiliary contact Ko. The first switch K1 is arranged on the loop formed by the power conversion circuit 110 and the contactor coil KM; the normally open auxiliary contact Ko is arranged on the loop formed by the DC auxiliary power supply 130 and the contactor coil KM, and the normally open auxiliary contact Ko follows the normally open main contact.

[0034] The first switch K1 is set on the loop formed by the power conversion circuit 110 and the contactor coil KM. When the first switch K1 is closed, the power conversion circuit 110 provides power to the contactor coil KM, so that the normally open main contact is closed, and the normally open auxiliary contact Ko follows the normally open main contact to switch from the off state to the on state, so that the loop formed by the DC auxiliary power supply 130 and the contactor coil KM is connected, and the DC auxiliary power supply 130 supplies power to the contactor coil KM to maintain the normally open main contact closed. If the voltage of the power grid 200 drops, the DC auxiliary power supply 130 provides holding power to the contactor coil KM to maintain the voltage across the contactor coil KM, and the contactor can still maintain the pull-in state to achieve low voltage ride-through.

[0035] The specific type of the first switch K1 can be selected according to the actual application scenario and is not limited here. For example, the first switch K1 can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulate-Gate Bipolar Transistor).

[0036] The location where the first switch K1 is connected can be determined according to the actual application scenario and is not limited here.

[0037] Reference Figure 2 As an example, the first end of the first switch K1 is electrically connected to the first output end of the power conversion circuit 110, and the second end of the first switch K1 is electrically connected to the first end of the contactor coil KM. When the first switch K1 is closed, the power conversion circuit 110 provides power to the contactor coil KM, and when the first switch K1 is opened, the loop formed by the power conversion circuit 110 and the contactor coil KM is disconnected.

[0038] Reference Figure 3 As an example, the first end of the first switch K1 is electrically connected to the second output end of the power conversion circuit 110, and the second end of the first switch K1 is electrically connected to the second end of the contactor coil KM. When the first switch K1 is closed, the power conversion circuit 110 provides power to the contactor coil KM, and when the first switch K1 is opened, the loop formed by the power conversion circuit 110 and the contactor coil KM is disconnected.

[0039] In some embodiments, the switch circuit 120 further includes a normally closed auxiliary contact Kc. The normally closed auxiliary contact Kc is disposed on a loop formed by the power conversion circuit 110 and the contactor coil KM, and the normally closed auxiliary contact Kc follows the normally open main contact.

[0040] When the first switch K1 is closed, the power conversion circuit 110 provides power to the contactor coil KM, so that the normally open main contact is closed, and the normally closed auxiliary contact Kc follows the normally open main contact to switch from the on state to the off state, so that the loop formed by the power conversion circuit 110 and the contactor coil KM is disconnected, and the power grid 200 does not provide power to the contactor coil KM, but the DC auxiliary power supply 130 supplies power to the contactor coil KM to maintain the normally open main contact closed. The loop formed by the power grid 200 and the contactor coil KM and the loop formed by the DC auxiliary power supply 130 and the contactor coil KM are controlled by auxiliary contacts with opposite actions, which can avoid high-voltage and low-voltage DC power supplies from supplying power to the contactor coil at the same time, and prevent the DC auxiliary power supply 130 from being damaged. At this time, if the voltage of the power grid 200 drops, the contactor can still maintain the pull-in, and the contactor is not affected by the voltage fluctuation of the power grid 200, thereby realizing low voltage ride-through.

[0041] In some embodiments, the grid-connected contactor control circuit 100 further includes a first transient voltage suppressor TVS, a first end of which is electrically connected to a first end of the contactor coil KM, and a second end of which is electrically connected to a second end of the contactor coil KM.

[0042] The first transient voltage suppressor TVS is connected in parallel with the contactor coil KM. When the switch circuit 120 is disconnected, the loop formed by the first transient voltage suppressor TVS and the contactor coil KM is turned on, and the current of the contactor coil KM is quickly consumed through the transient voltage suppressor TVS, so that the contactor can be quickly shut down.

[0043] In some embodiments, the switch circuit 120 includes a first diode D1 , an anode of the first diode D1 is electrically connected to the positive electrode of the DC auxiliary power supply 130 , and a cathode of the first diode D1 is electrically connected to the contactor coil KM.

[0044] The first diode D1 forms a unidirectional conduction loop between the DC auxiliary power supply 130 and the contactor coil KM. When the voltage of the power grid 200 is normal, the voltage on the output side of the power conversion circuit 110 is greater than the voltage of the positive electrode of the DC auxiliary power supply 130, and the first diode D1 is reversely cut off. At this time, the voltage of the power grid 200 can provide electrical energy for the contactor coil KM to close the normally open main contact. When the voltage of the power grid 200 is reduced to a voltage lower than the positive electrode of the DC auxiliary power supply 130, the first diode D1 is forward-conducted, and the DC auxiliary power supply 130 provides electrical energy for the contactor coil KM to keep the normally open main contact in a closed state, thereby achieving low voltage ride-through.

[0045] Reference Figures 4 to 6In some embodiments, the grid-connected contactor control circuit 100 further includes a second switch K2, which is disposed on a loop formed by the power grid 200 and the power conversion circuit 110. The second switch K2 is turned off when the voltage on the output side of the power conversion circuit 110 drops, so that the first diode D1 is forward-conducted.

[0046] The second switch K2 is mainly used to control the on-off of the loop formed by the power grid 200 and the power conversion circuit 110. When the voltage on the output side of the power conversion circuit 110 drops, the second switch K2 is turned off, the loop formed by the power grid 200 and the power conversion circuit 110 is disconnected, the first diode D1 is forward-conducted, and the DC auxiliary power supply 130 provides power to the contactor coil KM. The DC auxiliary power supply 130 can adjust the output voltage to be stable within the voltage range that maintains the normally open main contact of the contactor closed, so that the state of the normally open main contact is not affected by the voltage fluctuation of the power grid 200, thereby achieving low voltage ride-through.

[0047] The specific type of the second switch K2 can be selected according to the actual application scenario and is not limited here. For example, the second switch K2 can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulate-Gate Bipolar Transistor).

[0048] The location where the second switch K2 is connected can be determined according to the actual application scenario and is not limited here.

[0049] Reference Figures 4 to 6 As an example, the first end of the second switch K2 is electrically connected to the power grid 200, and the second end of the second switch K2 is electrically connected to the input side of the power conversion circuit 110. When the second switch K2 is closed, the power energy of the power grid 200 is rectified by the power conversion circuit 110 and then provided to the contactor coil KM.

[0050] In some embodiments, the grid-connected contactor control circuit 100 further includes: a third switch K3 and a second transient voltage suppressor TVS. The third switch K3 is connected in series with the contactor coil KM; the second transient voltage suppressor TVS is connected in parallel with the third switch K3, or the second transient voltage suppressor TVS is connected in parallel with the contactor coil KM and is electrically connected to an end of the third switch K3 close to the contactor coil KM.

[0051] The locations where the third switch K3 and the second transient voltage suppressor TVS are connected can be determined according to the actual application scenario and are not limited here.

[0052] Reference Figure 4As an example, the first end of the third switch K3 is electrically connected to the first output end of the power conversion circuit 110, the second end of the third switch K3 is electrically connected to the first end of the contactor coil KM, the first end of the second transient voltage suppressor TVS is electrically connected to the second end of the third switch K3 and the first end of the contactor coil KM respectively, and the second end of the second transient voltage suppressor TVS is electrically connected to the second end of the contactor coil KM. When the second switch K2 and the third switch K3 are both disconnected, the current of the contactor coil KM is quickly consumed through the loop formed by the second transient voltage suppressor TVS, and the contactor can be quickly turned off.

[0053] Reference Figure 5 As an example, the first end of the third switch K3 is electrically connected to the second output end of the power conversion circuit 110, the second end of the third switch K3 is electrically connected to the second end of the contactor coil KM, the first end of the second transient voltage suppressor TVS is electrically connected to the first output end of the power conversion circuit 110 and the first end of the contactor coil KM, and the second end of the second transient voltage suppressor TVS is electrically connected to the second end of the third switch K3 and the second end of the contactor coil KM. When the second switch K2 and the third switch K3 are both disconnected, the current of the contactor coil KM is quickly consumed through the loop formed by the second transient voltage suppressor TVS, so that the contactor can be quickly turned off.

[0054] Reference Figure 6 As an example, the first end of the third switch K3 is electrically connected to the first output end of the power conversion circuit 110, the second end of the third switch K3 is electrically connected to the first end of the contactor coil KM, the first end of the second transient voltage suppressor TVS is electrically connected to the first end of the third switch K3, and the second end of the second transient voltage suppressor TVS is electrically connected to the second end of the third switch K3. When the second switch K2 and the third switch K3 are both disconnected, the current of the contactor coil KM is quickly consumed through the loop formed by the second transient voltage suppressor TVS and the power conversion circuit 110, so that the contactor can be quickly turned off.

[0055] Continue to refer to Figure 2 and Figure 3 In some embodiments, the power conversion circuit 110 includes: a center-tapped transformer, a second diode D2, and a third diode D3. The primary winding of the center-tapped transformer is electrically connected to the power grid 200, and the center point of the secondary winding of the center-tapped transformer is electrically connected to the second end of the contactor coil KM; the anode of the second diode D2 is electrically connected to the first end of the secondary winding of the center-tapped transformer, and the cathode of the second diode D2 is electrically connected to the first end of the contactor coil KM; the anode of the third diode D3 is electrically connected to the second end of the secondary winding of the center-tapped transformer, and the cathode of the third diode D3 is electrically connected to the first end of the contactor coil KM.

[0056] When the AC power output by the power grid 200 passes through the center-tapped transformer, its positive and negative half-waves are respectively directed to the second diode D2 and the third diode D3. During the positive half-wave, the second diode D2 is forward biased and turned on, allowing current to pass and flow to the load such as the contactor coil KM; during the negative half-wave, the third diode D3 is forward biased and turned on, also allowing current to pass and flow to the load. The two diodes are alternately turned on to achieve full-wave rectification. The rectification circuit formed by the center-tapped transformer and the diode has good stability and high rectification efficiency.

[0057] Continue to refer to Figures 4 to 6 In some embodiments, the power conversion circuit 110 includes a rectifier circuit 111. The AC side of the rectifier circuit 111 is electrically connected to the power grid 200, and the DC side of the rectifier circuit 111 is electrically connected to the contactor coil KM.

[0058] The midpoint of the upper bridge arm of the rectifier circuit 111 is electrically connected to the first end of the power grid 200, the midpoint of the lower bridge arm of the rectifier circuit 111 is electrically connected to the second end of the power grid 200, and the output end of the rectifier circuit 111 is electrically connected to the contactor coil KM.

[0059] The upper bridge arm and the lower bridge arm of the rectifier circuit 111 are alternately turned on in one cycle, and can use all two half cycles of the AC signal for rectification, with high rectification efficiency. In addition, the output voltage waveform of the rectifier circuit 111 is relatively smooth, with small ripples, which is conducive to improving the stability of the circuit, reducing noise interference, and making the output voltage closer to the ideal DC.

[0060] An embodiment of the present application provides a photovoltaic system, which includes a contactor and the aforementioned grid-connected contactor control circuit 100 , wherein the grid-connected contactor control circuit 100 is electrically connected to the contactor.

[0061] The contactor can be electrically connected between the power grid 200 and the grid-connected device. By controlling the on and off of the contactor, the grid-connected device can be controlled to switch between the grid-connected state and the off-grid state. When the contactor is closed, the grid-connected device is in the grid-connected state, and when the contactor is disconnected, the grid-connected device is in the off-grid state.

[0062] When the grid-connected device is in the grid-connected state, the grid-connected contactor control circuit 100 can control the DC auxiliary power supply 130 to provide holding power for the contactor coil KM, maintain the voltage across the contactor coil KM, so that when the voltage of the power grid 200 drops, the contactor can still remain closed to achieve low voltage ride-through.

[0063] The structure and working principle of the grid-connected contactor control circuit 100 may refer to the aforementioned embodiments, and will not be described in detail here.

[0064] According to the photovoltaic system of the present application, the DC auxiliary power supply 130 provides holding power for the contactor coil KM to maintain the voltage across the contactor coil KM, so that when the grid 200 voltage drops, the contactor can still remain attracted to achieve low voltage ride-through, with a simple circuit structure and low cost.

[0065] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A grid-connected contactor control circuit, characterized in that: include: Normally open main contacts are set in the grid-connected circuit; A contactor coil coupled to the normally open main contact; A power conversion circuit, wherein the input side of the power conversion circuit is electrically connected to the power grid, and the output side of the power conversion circuit is electrically connected to the contactor coil; A switch circuit, wherein an output end of the switch circuit is electrically connected to the contactor coil; A direct current auxiliary power supply is electrically connected to the input end of the switch circuit.

2. The grid-connected contactor control circuit according to claim 1, characterized in that: The switch circuit comprises: A first switch is arranged on a loop formed by the power conversion circuit and the contactor coil; A normally open auxiliary contact is arranged on a loop formed by the DC auxiliary power supply and the contactor coil, and the normally open auxiliary contact follows the normally open main contact to move.

3. The grid-connected contactor control circuit according to claim 2, characterized in that: The switch circuit further comprises: A normally closed auxiliary contact is arranged on a loop formed by the power conversion circuit and the contactor coil, and the normally closed auxiliary contact follows the normally open main contact to move.

4. The grid-connected contactor control circuit according to claim 3, characterized in that: The grid-connected contactor control circuit also includes: A first transient voltage suppressor, wherein a first end of the first transient voltage suppressor is electrically connected to a first end of the contactor coil, and a second end of the first transient voltage suppressor is electrically connected to a second end of the contactor coil.

5. The grid-connected contactor control circuit according to claim 1, characterized in that: The switch circuit comprises: A first diode, wherein an anode of the first diode is electrically connected to a positive electrode of the DC auxiliary power supply, and a cathode of the first diode is electrically connected to the contactor coil.

6. The grid-connected contactor control circuit according to claim 5, characterized in that: The grid-connected contactor control circuit also includes: The second switch is arranged on the loop formed by the power grid and the power conversion circuit, and the second switch is turned off when the voltage on the output side of the power conversion circuit drops, so that the first diode is forward-conducted.

7. The grid-connected contactor control circuit according to claim 6, characterized in that: The grid-connected contactor control circuit also includes: A third switch connected in series with the contactor coil; A second transient voltage suppressor, wherein the second transient voltage suppressor is connected in parallel with the third switch, or the second transient voltage suppressor is connected in parallel with the contactor coil and is electrically connected to an end of the third switch close to the contactor coil.

8. The grid-connected contactor control circuit according to any one of claims 1 to 7, characterized in that: The power conversion circuit comprises: A center-tapped transformer, wherein the primary winding of the center-tapped transformer is electrically connected to the power grid, and the center point of the secondary winding of the center-tapped transformer is electrically connected to the second end of the contactor coil; a second diode, wherein an anode of the second diode is electrically connected to a first end of the secondary winding of the center-tapped transformer, and a cathode of the second diode is electrically connected to a first end of the contactor coil; A third diode, wherein an anode of the third diode is electrically connected to the second end of the secondary winding of the center-tapped transformer, and a cathode of the third diode is electrically connected to the first end of the contactor coil.

9. The grid-connected contactor control circuit according to any one of claims 1 to 7, characterized in that: The power conversion circuit comprises: A rectifier circuit, wherein the AC side of the rectifier circuit is electrically connected to the power grid, and the DC side of the rectifier circuit is electrically connected to the contactor coil.

10. A photovoltaic system, characterized in that: The invention comprises a contactor and a grid-connected contactor control circuit according to any one of claims 1 to 9, wherein the grid-connected contactor control circuit is electrically connected to the contactor.

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