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 main contact which is disposed in a grid-connected loop; a contactor coil coupled with the main contact; the input side of the power conversion circuit is electrically connected with a power grid; the first switch is electrically connected to a loop formed by the power conversion circuit and the contactor coil; the input end of the one-way conduction device is electrically connected with the second end of the contactor coil, and the output end of the one-way conduction device is electrically connected with the first end of the contactor coil; and the controller is electrically connected with the driving end of the first switch and is used for increasing the duty ratio of the first switch when the voltage of the output side of the power conversion circuit is reduced. According to the control circuit, when the voltage of the power grid drops, the controller increases the duty ratio of the first switch and provides holding power for the contactor coil, so that the contactor can still be closed within a period of time and realize low voltage ride through, and the circuit is simple in structure and low in cost.

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 continuous development of the power system, the complexity and volatility of the power grid are increasing. Especially in the context of large-scale access to the power grid by renewable energy such as photovoltaic power generation, the problem of temporary sag and fluctuation of the power grid voltage has become particularly prominent. 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, most devices that achieve low voltage ride-through function require complex circuit design, which undoubtedly increases the cost of the equipment. 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 the contactor can remain energized for a period of time when the grid voltage drops, waiting for the grid voltage to recover, thereby mitigating the drastic changes in the power supply system caused by the grid voltage drop, and the circuit structure is simple and the cost is low.

[0004] In a first aspect, the present application provides a grid-connected contactor control circuit, comprising: Main contacts, set in the grid-connected circuit; Contactor coil, coupled with main contacts; A power conversion circuit, the input side of the power conversion circuit is electrically connected to the power grid; A first switch, the first switch is electrically connected to a loop formed by a power conversion circuit and a contactor coil; A unidirectional conductive device, wherein the input end of the unidirectional conductive device is electrically connected to the second end of the contactor coil, and the output end of the unidirectional conductive device is electrically connected to the first end of the contactor coil; The controller is electrically connected to the driving end of the first switch and is configured to increase the duty cycle of the first switch when the voltage at the output side of the power conversion circuit decreases.

[0005] According to the grid-connected contactor control circuit of the present application, when the voltage on the output side of the power conversion circuit drops, it indicates that the grid voltage has dropped. The controller increases the duty cycle of the first switch to provide holding power for the contactor coil and maintain the voltage across the contactor coil, so that when the grid voltage drops, the contactor can still remain attracted for a period of time, waiting for the grid voltage to recover, thereby mitigating the drastic changes in the power supply system caused by the grid voltage drop. The circuit structure is simple and the cost is low.

[0006] According to one embodiment of the present application, a power conversion circuit includes: A switching power supply circuit, wherein the AC side of the switching power supply circuit is electrically connected to the power grid, and the DC side of the switching power supply circuit is electrically connected to the contactor coil via a first switch.

[0007] According to one embodiment of the present application, the grid-connected contactor control circuit further includes: A capacitor, wherein a first end of the capacitor is electrically connected to a first end of the first switch, and a second end of the capacitor is electrically connected to a second end of the contactor coil.

[0008] According to one embodiment of the present application, when the voltage on the DC side of the switching power supply circuit decreases, the duty cycle of the first switch is determined according to the following formula: ; Among them, U km To maintain the voltage of the contactor, U1 is the voltage across the capacitor.

[0009] According to one embodiment of the present application, the rated voltage of the capacitor is greater than the minimum pickup voltage of the contactor coil.

[0010] According to one embodiment of the present application, a power conversion circuit includes: A full-bridge rectifier circuit, wherein the AC side of the full-bridge rectifier circuit is electrically connected to the power grid, and the DC side of the full-bridge rectifier circuit is electrically connected to the contactor coil.

[0011] According to one embodiment of the present application, when the voltage on the DC side of the full-bridge rectifier circuit decreases, the duty cycle of the first switch is determined according to the following formula: ; Among them, U km To maintain the voltage of the contactor, U2 is the voltage on the DC side of the full-bridge rectifier circuit.

[0012] According to one embodiment of the present application, the controller is also configured to drive the first switch with a first duty cycle when the contactor is connected to the grid, and to drive the first switch with a second duty cycle after the contactor is connected to the grid, so that the contactor remains energized, and the first duty cycle is greater than the second duty cycle.

[0013] According to one embodiment of the present application, the grid-connected contactor control circuit further includes: A load circuit is electrically connected to the contactor coil, and the load circuit is configured to consume electrical energy of the contactor coil when in a conducting state; The controller is electrically connected to the load circuit and is configured to control the first switch to be turned off and the load circuit to be turned on when receiving a shutdown signal of the grid-connected contactor.

[0014] According to one embodiment of the present application, the load circuit includes: The second switch is connected in series with the contactor coil; A transient voltage suppressor, the transient voltage suppressor is connected in parallel with the second switch, or the transient voltage suppressor is connected in parallel with the contactor coil; The controller is configured to control both the first switch and the second switch to be turned off when receiving a turn-off signal from the grid-connected contactor.

[0015] According to one embodiment of the present application, the controller is also configured to obtain on-grid and off-grid mode configuration information, and control the first switch and / or load circuit according to the on-grid and off-grid mode configuration information, and the on-grid and off-grid mode configuration information includes a low voltage ride-through mode and / or a fast switching mode.

[0016] In a second aspect, the present application provides a photovoltaic system, which includes: a contactor, an inverter and the aforementioned grid-connected contactor control circuit, wherein the grid-connected contactor control circuit is electrically connected to the contactor.

[0017] According to the photovoltaic system of the present application, when the voltage on the output side of the power conversion circuit in the grid-connected contactor control circuit drops, it indicates that the grid voltage has dropped. The controller increases the duty cycle of the first switch to provide holding power for the contactor coil and maintain the voltage across the contactor coil, so that when the grid voltage drops, the contactor can still remain attracted for a period of time, waiting for the grid voltage to recover, thereby mitigating the drastic changes in the power supply system caused by the grid voltage drop. The circuit structure is simple and the cost is low.

[0018] 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

[0019] 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; Figure 7 This is the sixth circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application; Figure 8 This is the seventh circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application; Fig. 9 This is the eighth circuit diagram of the grid-connected contactor control circuit provided in the embodiment of the present application.

[0020] Reference numerals: Grid-connected contactor control circuit 100, power conversion circuit 110, switching power circuit 111, full-bridge rectifier circuit 112, unidirectional conduction device 120, load circuit 130, power grid 200, contactor coil KM, first to second switches K1~K2, capacitor C, diode D, transient voltage suppressor TVS. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] In the context of large-scale access to the grid by renewable energy sources such as photovoltaic power generation, 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, most devices that achieve low voltage ride-through function require complex circuit design, which increases the equipment cost.

[0026] Reference Figure 1 , Figure 1 The 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 main contact, a contactor coil KM, a power conversion circuit 110, a first switch K1, a unidirectional conduction device 120 and a controller. The main contact is arranged in the grid-connected loop; the contactor coil KM is coupled with the main contact; the input side of the power conversion circuit 110 is electrically connected to the power grid 200; the first switch K1 is electrically connected to the loop formed by the power conversion circuit 110 and the contactor coil KM; the input end of the unidirectional conduction device 120 is electrically connected to the second end of the contactor coil KM, and the output end of the unidirectional conduction device 120 is electrically connected to the first end of the contactor coil KM; the controller is electrically connected to the driving end of the first switch K1, and is configured to increase the duty cycle of the first switch K1 when the voltage at the output side of the power conversion circuit 110 drops.

[0027] The main contact is arranged in the grid-connected circuit, and is mainly used to connect or disconnect the circuit between the grid 200 and the grid-connected equipment, so as to ensure smooth and safe power transmission.

[0028] The contactor coil KM and the main contact work through electromagnetic coupling. When the contactor coil KM is energized, the generated magnetic field will attract the main contact to close, otherwise it will cause the main contact to open, thereby achieving control of the grid-connected circuit.

[0029] The input side of the power conversion circuit 110 is connected to the power grid 200, 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 to meet the needs of different power grid 200 conditions.

[0030] The first switch K1 is electrically connected to the loop formed by the power conversion circuit 110 and the contactor coil KM, and adjusts the power supply to the contactor coil KM by periodically opening and closing, thereby controlling the action of the main contacts, which helps to reduce energy consumption and improve the response speed of the system.

[0031] 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).

[0032] The unidirectional conductive device 120 is electrically connected between the second end of the contactor coil KM and the first end of the contactor coil KM to form a unidirectional conductive path. The unidirectional conductive device 120 can continue current when the voltage on the output side of the power conversion circuit 110 drops, so as to supply power to the contactor coil KM for a certain period of time when the current is small, so as to maintain the main contacts closed.

[0033] The specific type of the unidirectional conductive device 120 can be selected according to the actual application scenario and is not limited here. For example, the unidirectional conductive device 120 can be a diode D, the anode of the diode D is electrically connected to the second end of the contactor coil KM, and the cathode of the diode D is electrically connected to the first end of the contactor coil KM.

[0034] The controller is electrically connected to the driving end of the first switch K1. The controller can obtain the voltage on the output side of the power conversion circuit 110 in real time. When the voltage on the output side of the power conversion circuit 110 drops, it indicates that the voltage of the power grid 200 drops. At this time, the controller increases the duty cycle of the first switch K1, and the voltage across the contactor coil KM is the product of the voltage on the output side of the power conversion circuit 110 and the duty cycle of the first switch K1. When the voltage of the power grid 200 drops, increasing the duty cycle of the first switch K1 can maintain the voltage across the contactor coil KM, so that when the voltage of the power grid 200 drops, the contactor can still remain energized for a period of time, waiting for the voltage of the power grid 200 to recover, and slowing down the drastic changes in the power supply system caused by the voltage drop of the power grid 200.

[0035] According to the grid-connected contactor control circuit 100 of the present application, when the voltage on the output side of the power conversion circuit 110 drops, it indicates that the voltage of the power grid 200 drops. The controller increases the duty cycle of the first switch K1, provides holding power for the contactor coil KM, and maintains the voltage across the contactor coil KM, so that when the voltage of the power grid 200 drops, the contactor can still remain attracted for a period of time, waiting for the voltage of the power grid 200 to recover, thereby mitigating the drastic changes in the power supply system caused by the voltage drop of the power grid 200. The circuit structure is simple and the cost is low.

[0036] In some embodiments, the power conversion circuit 110 includes a switching power circuit 111, the AC side of the switching power circuit 111 is electrically connected to the power grid 200, and the DC side of the switching power circuit 111 is electrically connected to the contactor coil KM through the first switch K1.

[0037] The switching power supply circuit 111 is mainly used to convert the AC power outputted by the power grid 200 into DC power for the contactor coil KM to work. The switching power supply circuit 111 has high energy efficiency and power conversion efficiency, and can maintain the purity of the output voltage and improve the stability of the circuit.

[0038] Reference Figure 2 and Figure 3 , Figure 2 and Figure 3 The grid-connected contactor control circuit 100 provided in an embodiment of the present application is shown. In some embodiments, the grid-connected contactor control circuit 100 further includes a capacitor C, a first end of the capacitor C is electrically connected to a first end of the first switch K1, and a second end of the capacitor C is electrically connected to a second end of the contactor coil KM.

[0039] The first end of the capacitor C is electrically connected to the first end of the first switch K1 and the first output end of the power conversion circuit 110, respectively, and the second end of the capacitor C is electrically connected to the second end of the contactor coil KM and the second output end of the power conversion circuit 110, respectively. When the power grid 200 is normal, the electric energy output by the power grid 200 is partially stored in the capacitor C after being rectified by the power conversion circuit 110. When the voltage of the power grid 200 drops, the duty cycle of the first switch K1 is increased, and the electric energy stored in the capacitor C supplies power to the contactor coil KM, which can maintain the voltage across the contactor coil KM, so that when the voltage of the power grid 200 drops, the contactor can still remain attracted for a period of time to achieve low voltage ride-through.

[0040] The first switch K1 is mainly used to control the on / off of the loop formed by the power conversion circuit 110 and the contactor coil KM. The position of the first switch K1 can be selected according to the actual application scenario and is not limited here.

[0041] Reference Figure 4 and Figure 5As an example, the first end of the capacitor C is electrically connected to the first output end of the power conversion circuit 110 and the first end of the contactor coil KM respectively, the second end of the capacitor C is electrically connected to the first end of the first switch K1, and the second end of the first switch K1 is electrically connected to the second end of the contactor coil KM. When the voltage of the power grid 200 drops, the duty cycle of the first switch K1 is increased, and the electric energy stored in the capacitor C can power the contactor coil KM.

[0042] In some embodiments, when the voltage on the DC side of the switching power supply circuit 111 decreases, the duty cycle of the first switch K1 is determined according to the following formula: ; Among them, U km To maintain the voltage of the contactor, U1 is the voltage across the capacitor C.

[0043] When the voltage of the power grid 200 is normal, taking the voltage across the capacitor C as 230 V as an example, if the first switch K1 maintains the contactor closed at a duty cycle of 7%, that is, the voltage to maintain the contactor closed is 230*7%=16.1 V. When the voltage on the DC side of the switching power supply circuit 111 drops, that is, when the voltage across the capacitor C is 50 V, the duty cycle of the first switch K1 is 7%*230 / 50=32.2%.

[0044] During the discharge process of the capacitor C, the voltage across the capacitor C gradually decreases, and the duty cycle of the first switch K1 gradually increases. It can be understood that the upper limit of the duty cycle of the first switch K1 does not exceed 1.

[0045] In some embodiments, the rated voltage of capacitor C is greater than the minimum pickup voltage of contactor coil KM.

[0046] The rated voltage of capacitor C is greater than the minimum pull-in voltage of contactor coil KM. When the electric energy stored in capacitor C is transmitted to contactor coil KM, contactor coil KM can be kept pulled in to achieve low voltage ride-through.

[0047] Reference Figures 6 to 9 In some embodiments, the power conversion circuit 110 includes a full-bridge rectifier circuit 112, the AC side of the full-bridge rectifier circuit 112 is electrically connected to the power grid 200, and the DC side of the full-bridge rectifier circuit 112 is electrically connected to the contactor coil KM.

[0048] The midpoint of the upper bridge arm of the full-bridge rectifier circuit 112 is electrically connected to the first end of the power grid 200, the midpoint of the lower bridge arm of the full-bridge rectifier circuit 112 is electrically connected to the second end of the power grid 200, and the output end of the full-bridge rectifier circuit 112 is electrically connected to the contactor coil KM.

[0049] The upper bridge arm and the lower bridge arm of the full-bridge rectifier circuit 112 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 full-bridge rectifier circuit 112 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.

[0050] The first switch K1 is mainly used to control the on / off of the loop formed by the full-bridge rectifier circuit 112 and the contactor coil KM. The position of the first switch K1 can be selected according to the actual application scenario, and the specific position can refer to the above embodiment, which will not be repeated here.

[0051] In some embodiments, when the voltage on the DC side of the full-bridge rectifier circuit 112 decreases, the duty cycle of the first switch K1 is determined according to the following formula: ; Among them, U km To maintain the voltage of the contactor at which it is pulled in, U2 is the voltage on the DC side of the full-bridge rectifier circuit 112 .

[0052] When the voltage of the power grid 200 is normal, taking the voltage on the DC side of the full-bridge rectifier circuit 112 as 220 V as an example, if the first switch K1 maintains the contactor energized with a duty cycle of 10%, that is, the voltage to maintain the contactor energized is 220*10%=22 V. When the voltage of the power grid 200 drops so that the voltage on the DC side of the full-bridge rectifier circuit 112 drops to 50 V, the duty cycle of the first switch K1 is 10%*220 / 50=44%.

[0053] In some embodiments, the controller is further configured to drive the first switch K1 with a first duty cycle when the contactor is connected to the grid, and to drive the first switch K1 with a second duty cycle after the contactor is connected to the grid, so that the contactor remains closed, and the first duty cycle is greater than the second duty cycle.

[0054] The first duty cycle is greater than the second duty cycle, that is, when the contactor is connected to the grid, the controller drives the first switch K1 with a larger switch duty cycle, so that the voltage transmitted to the contactor coil KM is larger, and the main contact of the contactor can be quickly attracted. After the contactor is connected to the grid, the controller drives the first switch K1 with a smaller switch duty cycle, and the voltage across the contactor coil KM is maintained at a lower voltage. The current through the contactor coil KM is the basic holding current, which effectively reduces the power consumption of the contactor in the on state, realizes high-voltage contactor attraction, and low-voltage contactor maintenance attraction.

[0055] It should be noted that the specific values ​​of the first duty cycle and the second duty cycle can be selected according to the actual application scenario and are not limited here. For example, the first duty cycle can be 20% and the second duty cycle can be 8%.

[0056] Reference Figures 2 to 9 In some embodiments, the grid-connected contactor control circuit 100 further includes a load circuit 130. The load circuit 130 is electrically connected to the contactor coil KM, and the load circuit 130 is configured to consume the electric energy of the contactor coil KM when in the on state; the controller is electrically connected to the load circuit 130, and is configured to control the first switch K1 to turn off and control the load circuit 130 to turn on when receiving the off signal of the grid-connected contactor.

[0057] The controller receives a shutdown signal from the grid-connected contactor, that is, when the contactor needs to be shut down, the controller can control the first switch K1 to be disconnected, the load circuit 130 to be turned on, and the current of the contactor coil KM is quickly consumed through the load circuit 130, thereby achieving rapid shutdown of the contactor.

[0058] The load circuit 130 is mainly used to quickly consume the current of the contactor coil KM when the contactor needs to be turned off. Its specific structure can be selected according to the actual application scenario. For example, the load circuit 130 can include a resistor with a higher resistance or a transient voltage suppressor TVS.

[0059] In some embodiments, the load circuit 130 includes a second switch K2 and a transient voltage suppressor TVS. The second switch K2 is connected in series with the contactor coil KM; the transient voltage suppressor TVS is connected in parallel with the second switch K2, or the transient voltage suppressor TVS is connected in parallel with the contactor coil KM; the controller is configured to control both the first switch K1 and the second switch K2 to be turned off when receiving a shutdown signal from the grid-connected contactor.

[0060] Reference Figure 3 , Figure 5 , Figure 7 and Figure 8 , the first end of the second switch K2 is electrically connected to the input end of the unidirectional conductive device 120 and the first end of the transient voltage suppressor TVS, respectively, the second end of the second switch K2 is electrically connected to the second end of the contactor coil KM and the second end of the transient voltage suppressor TVS, respectively, and the first end of the contactor coil KM is electrically connected to the output end of the unidirectional conductive device 120. When the controller controls the first switch K1 and the second switch K2 to be disconnected, the current of the contactor coil KM drops, and a reverse voltage is formed at both ends of the transient voltage suppressor TVS. The reverse voltage is greater than the breakdown voltage of the transient voltage suppressor TVS, and the impedance of the transient voltage suppressor TVS drops rapidly. The energy of the contactor coil KM is rapidly consumed through the loop formed by the transient voltage suppressor TVS and the unidirectional conductive device 120, thereby realizing the rapid shutdown of the contactor.

[0061] Reference Figure 2 , Figure 4 , Figure 6 and Fig. 9, the first end of the second switch K2 is electrically connected to the input end of the unidirectional conductive device 120, the second end of the second switch K2 is electrically connected to the second end of the transient voltage suppressor TVS and the second end of the contactor coil KM, and the output end of the unidirectional conductive device 120 is electrically connected to the first end of the transient voltage suppressor TVS and the first end of the contactor coil KM. When the controller controls the first switch K1 and the second switch K2 to be disconnected, the current of the contactor coil KM drops, and a reverse voltage is formed at both ends of the transient voltage suppressor TVS. The reverse voltage is greater than the breakdown voltage of the transient voltage suppressor TVS, and the impedance of the transient voltage suppressor TVS drops rapidly. The energy of the contactor coil KM is quickly consumed by the transient voltage suppressor TVS, thereby realizing the rapid shutdown of the contactor.

[0062] In some embodiments, the controller is further configured to obtain on-grid and off-grid mode configuration information, and control the first switch K1 and / or the load circuit 130 according to the on-grid and off-grid mode configuration information, wherein the on-grid and off-grid mode configuration information includes a low voltage ride-through mode and / or a fast switching mode.

[0063] When the on-grid and off-grid mode configuration information is the low voltage ride-through mode, if the grid voltage drops, the voltage on the output side of the power conversion circuit 110 will drop, and the controller can achieve low voltage ride-through by increasing the duty cycle of the first switch K1.

[0064] When the on-grid and off-grid mode configuration information is a fast switching mode, the controller can control the first switch K1 to be disconnected and the load circuit 130 to be turned on, so as to realize the fast consumption of the energy of the contactor coil KM, thereby realizing the fast shutdown of the contactor.

[0065] The specific principles of the grid-connected contactor control circuit 100 for achieving low voltage ride-through and fast switching can be referred to the aforementioned embodiments, which will not be described in detail here.

[0066] It is understandable that the grid-connected contactor control circuit 100 in the aforementioned embodiment allows to be set to the low voltage ride-through mode and the fast switching mode at the same time. The controller can select the mode according to the actual application scenario. When one mode is selected, the program of the other mode is not called, thereby reducing the waste of software resources.

[0067] An embodiment of the present application provides a photovoltaic system, which includes: a contactor, an inverter, and the aforementioned grid-connected contactor control circuit 100, wherein the grid-connected contactor control circuit 100 is electrically connected to the contactor.

[0068] The contactor is electrically connected to the grid-connected circuit between the inverter and the power grid 200. By controlling the on and off of the contactor, the inverter can be controlled to switch between the grid-connected state and the off-grid state. When the contactor is closed, the inverter is in the grid-connected state, and when the contactor is disconnected, the inverter is in the off-grid state.

[0069] When the inverter is in the grid-connected state, if the voltage of the grid 200 fluctuates and causes a voltage drop, the grid-connected contactor control circuit 100 can keep the contactor closed for a period of time to achieve low voltage ride-through.

[0070] 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.

[0071] According to the photovoltaic system of the present application, when the voltage on the output side of the power conversion circuit 110 in the grid-connected contactor control circuit 100 drops, it indicates that the voltage of the power grid 200 drops. The controller increases the duty cycle of the first switch K1 to provide holding power for the contactor coil KM, and maintains the voltage across the contactor coil KM, so that the contactor can remain attracted for a period of time when the voltage of the power grid 200 drops, waiting for the voltage of the power grid 200 to recover, thereby mitigating the drastic changes in the power supply system caused by the voltage drop of the power grid 200. The circuit structure is simple and the cost is low.

[0072] 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.

[0073] 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: Main contacts, set in the grid-connected circuit; A contactor coil coupled to the main contact; A power conversion circuit, wherein an input side of the power conversion circuit is electrically connected to a power grid; A first switch, the first switch being electrically connected to a loop formed by the power conversion circuit and the contactor coil; A unidirectional conductive device, wherein the input end of the unidirectional conductive device is electrically connected to the second end of the contactor coil, and the output end of the unidirectional conductive device is electrically connected to the first end of the contactor coil; The controller is electrically connected to the driving end of the first switch and is configured to increase the duty cycle of the first switch when the voltage at the output side of the power conversion circuit decreases.

2. The grid-connected contactor control circuit according to claim 1, characterized in that: The power conversion circuit comprises: A switching power supply circuit, wherein the AC side of the switching power supply circuit is electrically connected to the power grid, and the DC side of the switching power supply circuit is electrically connected to the contactor coil through the first switch.

3. The grid-connected contactor control circuit according to claim 2, characterized in that: The grid-connected contactor control circuit also includes: A capacitor, wherein a first end of the capacitor is electrically connected to a first end of the first switch, and a second end of the capacitor is electrically connected to a second end of the contactor coil.

4. The grid-connected contactor control circuit according to claim 3, characterized in that: When the voltage on the DC side of the switching power supply circuit decreases, the duty cycle of the first switch is determined according to the following formula: ； Among them, U km To maintain the voltage at which the contactor is pulled in, U1 is the voltage across the capacitor.

5. The contactor control circuit according to claim 3, characterized in that: The rated voltage of the capacitor is greater than the minimum pickup voltage of the contactor coil.

6. The grid-connected contactor control circuit according to claim 1, characterized in that: The power conversion circuit comprises: A full-bridge rectifier circuit, wherein the AC side of the full-bridge rectifier circuit is electrically connected to the power grid, and the DC side of the full-bridge rectifier circuit is electrically connected to the contactor coil.

7. The grid-connected contactor control circuit according to claim 6, characterized in that: When the voltage on the DC side of the full-bridge rectifier circuit decreases, the duty cycle of the first switch is determined according to the following formula: ； Among them, U km To maintain the voltage at which the contactor is pulled in, U2 is the voltage on the DC side of the full-bridge rectifier circuit.

8. The grid-connected contactor control circuit according to claim 1, characterized in that: The controller is also configured to drive the first switch with a first duty cycle when the contactor is connected to the grid, and to drive the first switch with a second duty cycle after the contactor is connected to the grid to keep the contactor closed, wherein the first duty cycle is greater than the second duty cycle.

9. The grid-connected contactor control circuit according to any one of claims 1 to 8, characterized in that: The grid-connected contactor control circuit also includes: A load circuit, electrically connected to the contactor coil, wherein the load circuit is configured to consume electrical energy of the contactor coil when in a conducting state; The controller is electrically connected to the load circuit, and is configured to control the first switch to be turned off and control the load circuit to be turned on when receiving a shutdown signal from the grid-connected contactor.

10. The grid-connected contactor control circuit according to claim 9, characterized in that: The load circuit comprises: A second switch connected in series with the contactor coil; A transient voltage suppressor, wherein the transient voltage suppressor is connected in parallel with the second switch, or the transient voltage suppressor is connected in parallel with the contactor coil; The controller is configured to control both the first switch and the second switch to be turned off upon receiving a turn-off signal of the grid-connected contactor.

11. The grid-connected contactor control circuit according to claim 9, characterized in that: The controller is also configured to obtain on-grid and off-grid mode configuration information, and control the first switch and / or the load circuit according to the on-grid and off-grid mode configuration information, wherein the on-grid and off-grid mode configuration information includes a low voltage ride-through mode and / or a fast switching mode.

12. A photovoltaic system, characterized in that: The utility model comprises a contactor, an inverter and a grid-connected contactor control circuit according to any one of claims 1 to 11, wherein the grid-connected contactor control circuit is electrically connected to the contactor.

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