Under-voltage protection control device matched with distributed photovoltaic grid-connected switch

Abstract

The utility model discloses an undervoltage protection control device matched with a distributed photovoltaic grid-connected switch for use, which comprises an undervoltage detection module, a delay protection module, a voltage detection module, a driving module, a grid-connected switch and a power supply module, the output end of the undervoltage detection module is connected with the signal input end of the delay protection module, the output end of the delay protection module is connected with the input end of the driving module, the output end of the driving module is connected with the signal input end of the grid-connected switch, and the input end of the voltage detection module is connected to the distributed photovoltaic array. The output end of the voltage detection module is connected with the input end of the driving module, and the power supply module is connected with the power input end of the delay protection module. The device has the remarkable effects that the device not only meets the setting requirements of grid-connected switch under-voltage tripping and voltage-detecting closing, but also is high in use freedom degree, good in precision, and high in operation stability and safety.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic grid-connected control, in particular to an undervoltage protection control device for supporting distributed photovoltaic grid-connected switches. Background Art

[0002] The photovoltaic grid-connected power generation system is a solar photovoltaic power generation system connected to the conventional power grid to jointly undertake the power supply task. In order to protect the safe operation between the power grid and the photovoltaic power station while ensuring the convenience of users, it is necessary to ensure that the entire photovoltaic power station system trips when there is no pressure and automatically closes when there is pressure. This ensures the safety of the equipment and the stability of the power grid.

[0003] However, the operating characteristics of the undervoltage release of the standard grid-connected switch for conventional power distribution do not meet the requirements for photovoltaic grid-connected access. It is necessary to request a customized undervoltage release from the switch manufacturer. However, there are many switch manufacturers and models in actual projects, and the products of each manufacturer are not universal, which makes the customization workload very large and greatly affects the progress of the project. At the same time, the operating parameters of the undervoltage release produced according to customized parameters cannot be re-adjusted, and it is not convenient to use it flexibly in different photovoltaic projects.

[0004] Therefore, an undervoltage protection control device for distributed photovoltaic grid-connected switches is needed to overcome the above-mentioned defects. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the utility model is to provide an undervoltage protection control device for a distributed photovoltaic grid-connected switch, which not only meets the setting requirements of undervoltage tripping and pressure-detecting closing of the grid-connected switch, but also has high freedom of use, good precision, high stability and safety in operation.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0007] An undervoltage protection control device for a distributed photovoltaic grid-connected switch, the key of which is: comprising an undervoltage detection module, a delay protection module, a voltage detection module, a drive module, a grid-connected switch and a power supply module, the input end of the undervoltage detection module is connected to the distributed photovoltaic array, the output end of the undervoltage detection module is connected to the signal input end of the delay protection module, the output end of the delay protection module is connected to the input end of the drive module, the output end of the drive module is connected to the signal input end of the grid-connected switch, the input end of the voltage detection module is connected to the distributed photovoltaic array, the output end of the voltage detection module is connected to the input end of the drive module, and the power supply module is connected to the power input end of the delay protection module.

[0008] Furthermore, the undervoltage detection module includes a second rectifier unit, a voltage sampling unit and a voltage comparison unit, the input end of the second rectifier unit is connected to the distributed photovoltaic array, the output end of the second rectifier unit is linked to the input end of the voltage sampling unit, and the output end of the voltage sampling unit is connected to the input end of the voltage comparison unit.

[0009] Furthermore, the voltage sampling unit includes a first voltage-dividing resistor and a second voltage-dividing resistor, the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series and connected between the positive voltage output terminal and the negative voltage output terminal of the second rectifier unit, and the common node of the first voltage-dividing resistor and the second voltage-dividing resistor serves as the output terminal of the voltage sampling unit.

[0010] Furthermore, the voltage comparison unit includes a voltage comparator, the positive input terminal of the voltage comparator is connected in series with the first resistor and then connected to the output terminal of the voltage sampling unit, the negative input terminal of the voltage comparator inputs a reference voltage, and the output terminal of the voltage comparator is connected to the signal input terminal of the delay protection module.

[0011] Furthermore, the delay time of the delay protection module is adjustable.

[0012] Furthermore, the time delay protection module adopts a time delay relay.

[0013] Furthermore, a voltage input terminal of the power supply module is connected to the distributed photovoltaic array.

[0014] Furthermore, the device also includes a switch module, the input end of the switch module is connected to the distributed photovoltaic array, and the three output ends of the switch module are respectively connected to the undervoltage detection module, the voltage detection module and the power supply module.

[0015] Furthermore, the device also includes a state indicating module, an input end of the state indicating module is connected to an output end of the driving module.

[0016] Furthermore, the device also includes a filtering module and a surge protection module, the input end of the filtering module is connected to the distributed photovoltaic array, the output end of the filtering module is connected to the input end of the surge protection module, and the output end of the surge protection module is respectively connected to the input ends of the undervoltage detection module, the voltage detection module and the power supply module.

[0017] Furthermore, the filtering module is composed of two common-mode inductors wound on a magnetic coil and a metal casing; the surge protection module is composed of a first varistor, a second varistor and a third varistor, the first varistor and the second varistor are connected in series and connected between the two output ends of the common mode filter, the common node of the first varistor and the second varistor is grounded and connected to the casing of the common mode filter, and the third varistor is connected between the two output ends of the common mode filter and in parallel with the series circuit of the first varistor and the second varistor.

[0018] The remarkable effects of the utility model are:

[0019] 1. The device includes an undervoltage detection module, a delay protection module, a voltage detection module, a drive module, a grid-connected switch and a power supply module, and separates the undervoltage detection and the voltage detection. The action threshold of the corresponding grid-connected switch can be adjusted on-site, which greatly improves the freedom of use and the action accuracy. At the same time, it solves the problem of insufficient distance between the action voltage and the recovery voltage of an undervoltage release coil, and can meet the requirements of photovoltaic grid connection for undervoltage tripping setting of 20%Un and voltage detection closing setting of 85%Un.

[0020] 2. Set up an independent delay protection module, whose delay time can be adjusted on site to improve the adaptability of the device.

[0021] 3. Each functional unit in the device is independent of each other, and each functional unit can be replaced and repaired independently, which further improves the applicability of the device and reduces the subsequent operation and maintenance costs; since each functional unit is independent of each other, no special customization is required, reducing procurement and construction costs.

[0022] 4. By setting up the pressure detection module, automatic closing can be achieved, avoiding the problem of on-site closing after each power outage, improving the automation level of the system and improving the intelligence of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a principle block diagram of embodiment 1 of the utility model;

[0024] Figure 2 It is the circuit schematic diagram of the power supply module;

[0025] Figure 3 This is the circuit schematic diagram of the undervoltage detection module;

[0026] Figure 4 This is a principle block diagram of Embodiment 2 of the present utility model;

[0027] Figure 5 This is a principle block diagram of Embodiment 3 of the present utility model;

[0028] Figure 6 It is a circuit schematic diagram of the filter module and the surge protection module in Example 3. DETAILED DESCRIPTION

[0029] The specific implementation manner and working principle of the utility model are further described in detail below with reference to the accompanying drawings. Example

[0030] like Figure 1 As shown, an undervoltage protection control device for a distributed photovoltaic grid-connected switch includes a switch module, an undervoltage detection module, a delay protection module, a voltage detection module, a drive module, a grid-connected switch and a power supply module. The input end of the switch module is connected to the distributed photovoltaic array, and the three output ends of the switch module are respectively connected to the undervoltage detection module, the voltage detection module and the power supply module. The input end of the undervoltage detection module is connected to the distributed photovoltaic array, the output end of the undervoltage detection module is connected to the signal input end of the delay protection module, the output end of the delay protection module is connected to the input end of the drive module, the output end of the drive module is connected to the signal input end of the grid-connected switch, the input end of the voltage detection module is connected to the distributed photovoltaic array, the output end of the voltage detection module is connected to the input end of the drive module, the power supply module is connected to the power input end of the delay protection module, and the voltage input end of the power supply module is connected to the distributed photovoltaic array. Specifically:

[0031] The undervoltage detection module is used to sample the voltage of the distributed photovoltaic input and compare the sampled voltage signal with the reference voltage. If the sampled voltage is less than the reference voltage, an undervoltage protection signal is issued;

[0032] The time-delay protection module is used to send a time-delay protection signal according to the undervoltage protection signal;

[0033] The voltage detection module is used to control the undervoltage coil to close and send a closing control signal when the input voltage reaches 85% Ue after power is supplied;

[0034] The driving module is used to send a delayed opening signal according to the delayed protection signal or send a closing driving signal according to the closing control signal;

[0035] The grid-connected switch is used to complete the opening and power-off protection operation or the closing operation according to the delayed opening signal;

[0036] The power supply module is used to be charged by distributed photovoltaics in the charging state, and to supply power to the delay protection module in the discharging state, so as to ensure the undervoltage delay operation of the delay protection module when the voltage is too low or the power is off.

[0037] See attached Figure 2The power supply module includes a first rectifier unit, a first diode D1, a second diode D2, and a charging capacitor group formed by capacitors C1~C4 in parallel. The input end of the first rectifier unit is connected to the switch module, the positive voltage output end of the first rectifier unit is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the power input end of the delay protection module, the negative voltage output end of the first rectifier unit is connected to the anode of the second diode D2 after passing through the parallel resistor R1 and the charging capacitor group, the cathode of the second diode D2 is connected to the power input end of the delay protection module, and the cathode of the first diode D1 is also connected in series with the resistor R2 and connected to the second diode D2.

[0038] Among them, resistor R2 is the charging resistor of the charging capacitor group, which is used to limit the current when charging the charging capacitor group. If there is no resistor R2, the charging current will be too large and burn the charging capacitor group. Resistor R2 can also be connected in parallel with one or more resistors. The resistance value of resistor R2, as well as the number and resistance value of parallel resistors, are determined according to the actual charging current required. It can be seen that in Figure 2 In the structure shown, when the voltage output of the distributed photovoltaic is normal, the delay protection module is powered directly through the diode D1, and the charging capacitor group is charged through the diode D1 and the resistor R2. When the input power supply is in an undervoltage or power-off state, the charging capacitor group supplies power to the delay protection module through the diode D2. The current flow direction is limited by the diodes D1 and D2. The charging capacitor group can be composed of multiple capacitors in parallel, and at this time, a resistor R1 can also be connected in parallel to the charging capacitor group as a discharge resistor.

[0039] See attached Figure 3 The undervoltage detection module includes a second rectifying unit, a voltage sampling unit and a voltage comparing unit, the input end of the second rectifying unit is connected to the switch module, the output end of the second rectifying unit is linked to the input end of the voltage sampling unit, and the output end of the voltage sampling unit is connected to the input end of the voltage comparing unit, specifically:

[0040] The voltage sampling unit includes a first voltage-dividing resistor R3 and a second voltage-dividing resistor R4, the first voltage-dividing resistor R3 and the second voltage-dividing resistor R4 are connected in series and connected between the positive voltage output terminal and the negative voltage output terminal of the second rectifier unit, and a common node between the first voltage-dividing resistor R3 and the second voltage-dividing resistor R4 serves as the output terminal of the voltage sampling unit;

[0041] The voltage comparison unit includes a voltage comparator U1, a positive input terminal of the voltage comparator U1 is connected in series with a first resistor R5 and then connected to the output terminal of the voltage sampling unit, a negative input terminal of the voltage comparator U1 inputs a reference voltage, an output terminal of the voltage comparator U1 is connected to a signal input terminal of the delay protection module via a second resistor R6, and a third resistor R7 is connected between the output terminal of the voltage comparator U1 and its positive input terminal.

[0042] In this example, the delay time of the delay protection module is adjustable, the delay range is 0-10S, and the delay time adjustment value is 1S, 2S, 3S...10S.

[0043] Preferably, the delay protection module adopts a delay relay. In specific applications, the coil winding part is connected in series with the undervoltage detection module, and its switch part is connected to the power supply circuit of the driving module, so that when the sampled voltage is lower than the reference voltage, it can be powered so that the driving module can drive the grid-connected switch to realize the opening operation.

[0044] This embodiment uses the undervoltage detection module and the delay protection module as undervoltage protection for the main circuit. When the power supply voltage drops to within the range of 70% to 35% of the rated working voltage Ue of the undervoltage release, that is, less than the reference voltage, the undervoltage release should be activated to disconnect the grid-connected switch; when the power supply voltage is greater than or equal to 85% Ue, the grid-connected switch is guaranteed to be reliably closed. Example

[0045] See attached Figure 3 This embodiment is further improved on the basis of Embodiment 1, and the difference from Embodiment 1 is that the device further includes a status indication module, the input end of the status indication module is connected to the output end of the driving module, and the status indication module can display lights or contents of different colors according to different operating states of the distributed photovoltaic array, so that relevant personnel can easily know the grid-connected status, such as displaying a red light when the grid-connected switch is opened, displaying a green light when the grid-connected switch is closed, and displaying a flashing yellow light during delayed protection.

[0046] Therefore, through the provided status indication module, relevant personnel can easily learn the grid-connected status of the distributed photovoltaic array. Example

[0047] See attached Figure 4This embodiment is further improved on the basis of the embodiment 1, and the difference from the embodiment 1 is that the device further includes a status indication module, a filtering module and a surge protection module. The input end of the status indication module is connected to the output end of the driving module. The status indication module can display lights or contents of different colors according to different operating states of the distributed photovoltaic array, so that relevant personnel can easily know the grid-connected status, such as displaying a red light when the grid-connected switch is opened and disconnected, displaying a green light when the grid-connected switch is closed, and displaying a flashing yellow light during delayed protection; the input end of the filtering module is connected to the distributed photovoltaic array, the output end of the filtering module is connected to the input end of the surge protection module, and the output end of the surge protection module is respectively connected to the input ends of the undervoltage detection module, the voltage detection module and the power supply module.

[0048] See attached Figure 5 The filtering module is composed of two common-mode inductors wound on a magnetic coil and a metal shell; the surge protection module is composed of a first varistor, a second varistor and a third varistor. The first varistor and the second varistor are connected in series and connected between the two output ends of the common-mode filter. The common node of the first varistor and the second varistor is grounded and connected to the shell of the common-mode filter. The third varistor is connected between the two output ends of the common-mode filter and in parallel with the series circuit of the first varistor and the second varistor.

[0049] The technical solution provided by the utility model is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation method of the utility model. The description of the above embodiments is only used to help understand the method and core idea of ​​the utility model. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

Claims

1. An undervoltage protection control device for a distributed photovoltaic grid-connected switch, characterized in that: It includes an undervoltage detection module, a delay protection module, a voltage detection module, a drive module, a grid-connected switch and a power supply module. The input end of the undervoltage detection module is connected to the distributed photovoltaic array, the output end of the undervoltage detection module is connected to the signal input end of the delay protection module, the output end of the delay protection module is connected to the input end of the drive module, the output end of the drive module is connected to the signal input end of the grid-connected switch, the input end of the voltage detection module is connected to the distributed photovoltaic array, the output end of the voltage detection module is connected to the input end of the drive module, and the power supply module is connected to the power input end of the delay protection module.

2. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 1 is characterized in that: The undervoltage detection module includes a second rectifier unit, a voltage sampling unit and a voltage comparison unit, the input end of the second rectifier unit is connected to the distributed photovoltaic array, the output end of the second rectifier unit is linked to the input end of the voltage sampling unit, and the output end of the voltage sampling unit is connected to the input end of the voltage comparison unit.

3. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 2 is characterized in that: The voltage sampling unit includes a first voltage-dividing resistor and a second voltage-dividing resistor. The first voltage-dividing resistor and the second voltage-dividing resistor are connected in series and connected between the positive voltage output terminal and the negative voltage output terminal of the second rectifier unit. The common node of the first voltage-dividing resistor and the second voltage-dividing resistor serves as the output terminal of the voltage sampling unit.

4. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 2 is characterized in that: The voltage comparison unit includes a voltage comparator, a positive input terminal of the voltage comparator is connected in series with a first resistor and then connected to the output terminal of the voltage sampling unit, a negative input terminal of the voltage comparator inputs a reference voltage, and an output terminal of the voltage comparator is connected to the signal input terminal of the delay protection module.

5. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 1 is characterized in that: The delay time of the delay protection module is adjustable.

6. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 1, characterized in that: The time delay protection module adopts a time delay relay.

7. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 1 is characterized in that: The voltage input terminal of the power supply module is connected to the distributed photovoltaic array.

8. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 7 is characterized in that: The device also includes a switch module, the input end of which is connected to the distributed photovoltaic array, and the three output ends of the switch module are respectively connected to the undervoltage detection module, the voltage detection module and the power supply module.

9. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to any one of claims 1 to 8, characterized in that: The device further comprises a state indicating module, an input end of which is connected to an output end of the driving module.

10. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to any one of claims 1 to 8, characterized in that: The device also includes a filtering module and a surge protection module, the input end of the filtering module is connected to the distributed photovoltaic array, the output end of the filtering module is connected to the input end of the surge protection module, and the output end of the surge protection module is respectively connected to the input ends of the undervoltage detection module, the voltage detection module and the power supply module.

11. The undervoltage protection control device for distributed photovoltaic grid-connected switches according to claim 10, characterized in that: The filtering module is composed of two common-mode inductors wound on a magnetic coil and a metal shell; the surge protection module is composed of a first varistor, a second varistor and a third varistor, the first varistor and the second varistor are connected in series and connected between the two output ends of the common mode filter, the common node of the first varistor and the second varistor is grounded and connected to the shell of the common mode filter, and the third varistor is connected between the two output ends of the common mode filter and in parallel with the series circuit of the first varistor and the second varistor.

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