CN223391135U - A grid-connected and off-grid backup power system - Google Patents
A grid-connected and off-grid backup power systemInfo
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- CN223391135U CN223391135U CN202422394534.9U CN202422394534U CN223391135U CN 223391135 U CN223391135 U CN 223391135U CN 202422394534 U CN202422394534 U CN 202422394534U CN 223391135 U CN223391135 U CN 223391135U
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- grid
- circuit breaker
- shunt release
- control switch
- power
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Abstract
本实用新型涉及一种并离网备电系统，其中，设计了框架式断路器结构以替代了传统技术中普通断路器+并离网接触器的组合，使得并离网备电系统的并网转离网能力能够达到现有技术水平，乃至在大功率使用场景下也可以实现与电网侧的及时切离，克服了传统技术中并离网接触器在大功率使用场景下受限于机械结构，释放时间逐渐增大、无法继续满足备电系统快速切离网要求的问题，另外通过对于控制开关的闭合控制可实现低电压穿越，支持用户端在不同的离网模式间进行选择和切换。且在并网模式下，不再需要为保持并离网接触器吸合给线圈持续供电，能耗更低。
The present invention relates to a grid-connected and off-grid backup power system, wherein a frame-type circuit breaker structure is designed to replace the combination of an ordinary circuit breaker and a grid-connected and off-grid contactor in traditional technology, so that the grid-connected and off-grid switching capabilities of the grid-connected and off-grid backup power system can reach the existing technical level, and even in high-power usage scenarios, timely disconnection from the grid side can be achieved. This overcomes the problem that the grid-connected and off-grid contactor in traditional technology is limited by the mechanical structure in high-power usage scenarios, the release time gradually increases, and it can no longer meet the requirements of the backup power system for rapid grid disconnection. In addition, low voltage ride-through can be achieved by controlling the closing of the control switch, supporting the user end to select and switch between different off-grid modes. In the grid-connected mode, it is no longer necessary to continuously power the coil to keep the grid-connected and off-grid contactor attracted, resulting in lower energy consumption.
Description
Technical Field
The utility model relates to the field of power control, in particular to a parallel-off-grid standby power system.
Background
The standby power system based on new energy power supply such as light storage (solar photovoltaic energy storage) is used for switching control between traditional power grid power supply and photovoltaic energy storage power supply so as to realize a grid-connected mode accessed by a power grid and a grid-off mode separated from the power grid.
Based on the requirement of a user side for uninterrupted power supply, the power backup system connected with the optical storage must have the capability of being quickly separated from the power grid, namely, the power backup system is quickly separated from the power grid so as to avoid the phenomenon that the power backup system is damaged by an external power grid fault, so that the voltage of a load end is suddenly lowered, and electric equipment is down. However, some grid companies may require the power backup system to have low voltage ride through capability for the power grid based on the requirement of the power grid side for load stability, so the power backup system cannot be disconnected from the power grid quickly after the power grid voltage is temporarily low, that is, the power backup system is expected to have the low voltage ride through capability.
As shown in fig. 1, in order to cope with multiple switching between the grid and the off-grid, a conventional standby power system is provided with an off-grid contactor on the grid side. And after the grid-connected and off-grid contactor is disconnected and released, the standby power system is switched into an off-grid mode. When the parallel-to-off-grid contactor is in low power, the release time is very fast, the parallel-to-off-grid contactor can be basically disconnected within 20ms, and the function of fast switching off the grid can be realized. However, with the continuous increase of power, the standby system needs to be configured with larger size/specification off-grid contactors. The large-size off-grid contactor is limited by a mechanical structure, the release time of the contactor is gradually increased, generally about 70ms is required, and the requirement of quick off-grid of a standby power system cannot be continuously met, so that the contactor is one technical problem to be solved.
In addition, for the requirement of low voltage ride through, as the contactor coil is released immediately upon power failure, a control loop of the contactor coil needs to be designed specifically, such as a control manner of the contactor coil meeting the requirement of low voltage ride through proposed in the patent document (power supply device and power converter) with publication number N117713104 a. However, although this approach can achieve the ability of the contactor coil to remain engaged briefly after de-energizing, its control loop and its complexity, as well as the cost of implementation, are also high. This is another technical problem to which the present application is directed.
Disclosure of utility model
The utility model aims to overcome at least one defect, and provides a parallel-to-off network standby power system, which reduces the operation cost of the power system through the adjustment of a circuit structure and provides support for a user side to select to switch different grid-connected to-off network modes.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
The utility model provides a parallel-off grid standby power system, which comprises an inverter, a power grid and a power grid breaker, wherein the power grid is connected with an alternating current output side of the inverter through the power grid breaker to supply power for a load, the power grid breaker is a frame-type breaker and comprises a breaker body, an energy storage module, a shunt release and a control switch, the shunt release is used for controlling the switch state of the breaker body, the control switch is used for controlling the on-off of the shunt release,
The excitation coil and the control switch in the shunt release are connected in series, the shunt release and the control switch which are connected in series are connected with the output side of the energy storage module, the input side of the energy storage module is connected with the power grid or the inverter, and the energy storage module is powered by the power grid or the inverter and supplies power for the operation of the shunt release;
The control signal input end of the control switch is connected with an external control signal and is used for being conducted after receiving the external control signal, so that the shunt release is electrically tripped, and the breaker body is disconnected.
According to one embodiment of the utility model, the energy storage device comprises a rectifying module, wherein the input side of the rectifying module is connected with the power grid or the inverter, and the output side of the rectifying module is connected with the energy storage module.
According to one embodiment of the utility model, the rectifying module is a single-phase rectifying bridge, and two input ends of the single-phase rectifying bridge are respectively connected to two phase lines of the power grid.
According to one embodiment of the utility model, the energy storage module is an energy storage capacitor, and a loop formed by the shunt release and the control switch which are connected in series is connected with the energy storage capacitor in parallel.
According to one embodiment of the utility model, the inverter is connected with a grid connection point after being connected with an inverter circuit breaker, the grid is also connected with the grid connection point after being connected with the grid circuit breaker, and the load takes electricity from the grid connection point to work.
According to one embodiment of the utility model, the load is connected to the grid-connected point after being connected to the load breaker.
According to one embodiment of the utility model, the control switch is a transistor or a relay.
The invention also provides a parallel-off grid standby system, which comprises an inverter, a power grid and a power grid breaker, wherein the power grid is connected with an alternating current output side of the inverter through the power grid breaker to supply power to a load, the power grid breaker is a frame-type breaker and comprises a breaker body, a shunt release and a control switch, the shunt release is used for controlling the switch state of the breaker body, the control switch is used for controlling the on-off of the shunt release,
The excitation coil and the control switch in the shunt release are connected in series, the shunt release and the control switch which are connected in series are connected with the output side of the inverter, and the output side bus of the inverter is used for taking electricity, and the shunt release is an alternating current driven shunt release;
The control signal input end of the control switch is connected with an external control signal and is used for being conducted after receiving the external control signal, so that the shunt release is electrically tripped, and the breaker body is disconnected.
According to one embodiment of the utility model, the under-voltage tripping device with delay is used for controlling the switching state of the power grid circuit breaker body, is connected with a power grid and takes electricity from the power grid.
According to one embodiment of the utility model, the delay value of the undervoltage release with delay exceeds a low voltage ride through time preset for low voltage ride through.
Compared with the prior art, the parallel-to-off-grid standby power system has the advantages that:
The application designs a frame-type breaker structure to replace the combination of a common breaker and a parallel-to-off-grid contactor in the traditional technology, so that the parallel-to-off grid converting capability of a parallel-to-off grid standby power system can reach the prior art level, even the timely disconnection from the power grid side can be realized under a high-power use scene, the problems that the parallel-to-off grid contactor in the traditional technology is limited by a mechanical structure under the high-power use scene, the release time is gradually increased, the requirement of the standby power system on quick disconnection from the grid cannot be continuously met are overcome, in addition, the low-voltage ride through can be realized through the closing control of a control switch, and the selection and the switching of a user terminal among different off-grid modes are supported. In the grid-connected mode, the coil is not required to be continuously supplied with power for maintaining and being attracted by the off-grid contactor, and the energy consumption is lower.
Further, compared with the prior art with targeted design, the standby power system has the advantages that the number of devices required for off-grid operation of the power grid is small, the whole structure, layout and wiring are compact and simple, the cost is high, the control operation is convenient, and the implementation is easy.
Drawings
Some specific embodiments of the utility model will be described in detail hereinafter by way of example and not by way of limitation with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts or portions. It will be appreciated by those skilled in the art that the drawings are not necessarily drawn to scale. In the accompanying drawings:
FIG. 1 is a schematic circuit diagram of a prior art electrical system;
FIG. 2 is a schematic circuit diagram of an off-grid backup power system according to embodiment 1 of the present invention;
FIG. 3 is a schematic circuit diagram of an off-grid backup power system according to embodiment 2 of the present invention;
Fig. 4 is a schematic circuit diagram of an off-grid standby power system according to embodiment 3 of the present invention;
FIG. 5 is a grid-tied voltage versus time graph of a standard low voltage ride through (Low voltage ride through, LVRT).
Detailed Description
The following description of the embodiments of the present utility model will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the utility model are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
In addition, the technical features of the different embodiments of the present utility model described below may be combined with each other as long as they do not collide with each other.
Example 1:
The conventional standby power system is provided with circuit breakers on a power grid side, an inverter side and a load side, and the embodiment is mainly improved aiming at the power grid side, and a frame type circuit breaker structure is designed so as to conveniently perform parallel-to-grid control and off-grid operation on the power grid side.
As shown in fig. 2, the frame-type circuit breaker structure includes a circuit breaker body installed at the power grid side, and accessories such as a shunt release, a control switch, an energy storage module and the like.
The shunt release is used for controlling the switching state of the power grid circuit breaker body, and in the embodiment, the shunt release driven by direct current is adopted, and the nominal voltage of the shunt release is DC 220V.
The control switch is connected with the shunt release in series, an excitation coil and the control switch in the shunt release are connected with each other in series, the shunt release and the control switch which are connected with each other in series are connected with the output side of the energy storage module, the input side of the energy storage module is connected with the power grid or the inverter, the energy storage module is powered by the power grid or the inverter and supplies power for the operation of the shunt release, the control switch is used for controlling the on-off of the coil current of the shunt release, and the shunt release is used for controlling the on-off state of the breaker body.
The control switch is a system for receiving external control signals to close or release and separating from the network, such as a high-power optical reserve power system in the prior art, and the like, and has a mechanism for detecting and feeding back the inversion output voltage, the power grid voltage, the energy storage voltage and even the load voltage in the system, and the control switch of the standby power system in the embodiment can be used for judging whether the network separation is rapid off-network or low-voltage ride through based on the feedback of the voltage detection signals.
The control signal input end of the control switch is connected with an external control signal and is used for being conducted after receiving the external control signal, so that the shunt release is electrically tripped, and the breaker body is disconnected. In this embodiment, the control switch is controlled remotely by the upper computer, and the control switch can be powered by an independent driving power supply or triggered to be attracted by an input pulse broadband modulation signal. The control switch adopts the existing devices, such as a transistor or a relay, can be switched on and off by receiving an externally input control signal, and the working principle of the control switch is not described herein.
In order to convert the ac power provided by the power grid into the dc power suitable for the shunt release, the power system in this embodiment is provided with a rectifying module, as shown in fig. 2, where the rectifying module adopts a single-phase rectifying bridge composed of four diodes. Two input ends of the single-phase rectifier bridge are respectively connected to two phase lines of the power grid, and two output ends of the single-phase rectifier bridge are respectively connected with the shunt release and the other terminal of the control switch.
In this embodiment, the energy storage module employs an energy storage capacitor, and the capacitance of the energy storage capacitor is selected so that the shunt release can act at least once. The energy storage capacitor is connected in parallel with two ends of the shunt release and the control switch which are connected in series, and electricity is taken from the power grid side through the single-phase rectifier bridge. The energy storage module is used for storing electric energy for the action of the shunt release when the power grid is powered down.
The upper computer is a computer device which receives a user instruction, selects or switches a control mode based on a preloading program and the user instruction and sends out an operation command signal. In the corresponding control mode, the upper computer outputs corresponding signals to the control switch based on the read grid-connected point voltage signals and the control strategy of the current control module so as to control the switching state of the control switch.
The inverter is connected with the grid-connected point after being connected with the inverter circuit breaker, the grid is also connected with the grid-connected point after being connected with the grid circuit breaker, and the load takes electricity from the grid-connected point to work. The process of the standby power system when receiving an external control instruction to work is as follows:
Under the normal state of the power grid, the one-phase voltage of the power grid supplies power to the shunt release after rectification, when the shunt release is required to be disconnected, the upper computer sends a control signal to enable the control switch to be closed, the exciting coil of the shunt release is electrified, and the main contact of the breaker body is driven to be disconnected, because the shunt release only needs short-time electrification (the normally closed switch in the shunt release enables the shunt release to act and then automatically cut off the power supply), although the actual voltage is slightly higher than the nominal value, the current is still within the withstand voltage range of the coil in the shunt release, and the coil is not overheated in a short time, so the shunt release can still be used; when the power grid is powered down, although the power grid cannot supply power to the shunt release, the energy storage capacitor connected in parallel at the rear end of the rectifier bridge stores a part of electric energy, the released electric energy can still enable the shunt release to act once after the control switch is closed, and when low voltage ride-through is required to be realized, the control switch is only required to be closed within the time required by the standard.
The operation process of the high-power off-grid standby power system is described below with reference to a specific control method.
The control method for the high-power off-grid standby power system comprises the following steps of:
s1, acquiring a grid-connected point voltage signal or a voltage signal at the power grid side through a detection device, and transmitting the voltage signal to an upper computer;
S2, inputting a user instruction to the upper computer, and selecting or switching a control module by the upper computer according to the user instruction, wherein the control mode comprises a quick off-grid control mode and a low voltage ride through control mode;
s21, when the upper computer enters a quick off-network control mode, the control strategy executed by the upper computer is as follows:
reading the grid-connected point voltage signal and judging whether the grid-connected point voltage signal is lower than a first threshold value or not:
when the voltage signal of the grid-connected point is lower than a first threshold value, a control signal is sent to a control switch immediately, the control switch is controlled to be closed, a coil of the shunt release is electrified, a breaker body is controlled to be opened, and the standby power system enters an off-grid state;
When the voltage signal of the grid connection point is not lower than a first threshold value, maintaining the control switch in an opened state unchanged (the internal coil of the shunt release is not electrified), and enabling the standby power system to be in a grid connection state;
s22, when the upper computer enters a low voltage ride through mode, the control strategy executed by the upper computer is as follows:
Reading the grid-connected point voltage signal and judging whether the grid-connected point voltage signal is lower than a second threshold value or not:
When the voltage signal of the grid-connected point is not lower than a second threshold value, maintaining the control switch in an opened state;
When the voltage signal of the grid-connected point is lower than a second threshold value, judging whether the duration of the voltage signal of the grid-connected point lower than the second threshold value exceeds the preset low voltage ride-through time;
If the duration does not exceed the preset low voltage ride through time, maintaining the control switch in an on state unchanged, and enabling the standby power system to be in a grid-connected state;
If the duration exceeds the preset low voltage ride through time, the upper computer immediately sends a control signal to the control switch, controls the control switch to be closed, turns on a coil of the shunt release, controls the breaker body to be opened, and enables the standby power system to enter an off-grid state.
In the above step, the preset low voltage ride through time is a set value according to the specification, and according to the actual situation, the first threshold and the second threshold may be the same or different set values according to the specification.
As shown in fig. 5, a voltage-time curve of a grid-connected point of a standard low voltage ride through (Low voltage ride through, LVRT), in which curve 1 is a curve of a low voltage ride through stage, the minimum time of the low voltage ride through is generally about 2s, and it is assumed that the embodiment sets the minimum time of the low voltage ride through to be 1.5s, and after the low voltage ride through is required to be implemented, the control switch is only required to be not closed within 1.5s of the standard requirement. The control circuit breaker can be opened within 20ms according to the off-grid operation and specific conditions, and the selection from the existing shunt release.
Example 2:
The off-grid standby power system of the embodiment also comprises a frame-type circuit breaker structure, wherein the frame-type circuit breaker structure also comprises a circuit breaker body, a shunt release and a control switch. The shunt release is used for controlling the switching state of the power grid circuit device body, and the control signal input end of the control switch is connected with an external control signal (such as the signal output end of an upper computer) at the far end and used for controlling the on-off of the coil current of the shunt release.
In this embodiment, the control of the control switch of the parallel off-grid standby power system by the host computer is also taken as an example. The upper computer receives a user instruction and selects or switches a control mode according to the user instruction, and in the corresponding control mode, based on the read grid-connected point voltage signal and the control strategy of the current control module, the upper computer outputs a corresponding signal to the control switch to control the closing state of the control switch.
Unlike embodiment 1, this embodiment eliminates the rectifier bridge and the storage capacitor from the high power off-grid system.
In this embodiment, as shown in fig. 3, the shunt release is connected in series with the control switch and then connected to the power output terminal of the inverter of the backup power system. The shunt release adopts an AC 220V alternating current drive shunt release, and two ends of the shunt release are respectively connected with an N line and a phase line of the output end of the inverter, namely, electricity is taken from a line of the output end of the inverter.
Because the shunt release is powered by the inverter side in the embodiment, after the power grid is powered down, the shunt release can still obtain enough power to cause the breaker body to be disconnected.
The control method of the high-power off-grid standby power system in the embodiment comprises the following steps:
s1, acquiring a grid-connected point voltage signal or a voltage signal at the power grid side through a detection device, and transmitting the voltage signal to an upper computer;
S2, inputting a user instruction to the upper computer, and selecting or switching a control module by the upper computer according to the user instruction, wherein the control mode comprises a quick off-grid control mode and a low voltage ride through control mode;
s21, when the upper computer enters a quick off-network control mode, the control strategy executed by the upper computer is as follows:
The upper computer reads the grid-connected point voltage signal and judges whether the grid-connected point voltage signal is lower than a third threshold value,
When the voltage signal of the grid-connected point is lower than a third threshold value, a control signal is sent to a control switch immediately to control the control switch to be closed, a power supply loop where the output end of the inverter and the shunt release are positioned is conducted, a coil of the shunt release is electrified, and the breaker body is controlled to be disconnected, so that the standby power system enters an off-grid state;
When the voltage signal of the grid-connected point is not lower than a third threshold value, namely, the open state of the control switch is maintained unchanged, and the standby power system is in a grid-connected state;
S22, when the upper computer enters a low voltage ride through control mode, reading a grid-connected point voltage signal, and judging whether the grid-connected point voltage signal is lower than a fourth threshold value or not;
If the voltage signal of the grid-connected point is not lower than a fourth threshold value, maintaining the control switch in an opened state unchanged, and enabling the standby power system to be in a grid-connected state;
When the voltage signal of the grid-connected point is lower than a fourth threshold value, judging whether the duration of the voltage signal of the grid-connected point lower than the fourth threshold value exceeds the preset low voltage ride through time or not:
If the duration exceeds the preset low voltage ride-through time, the upper computer sends a control signal to the control switch to control the control switch to be closed, and the power supply loop where the output end of the inverter and the shunt release are positioned is conducted, so that the coil of the shunt release is electrified, the breaker body is controlled to be disconnected, and the standby power system enters an off-grid state;
If the duration does not exceed the preset low voltage ride through time, the control switch is kept in an opened state and is unchanged, and the standby power system is in a grid-connected state.
In the same manner as in embodiment 1, in the above step, the preset low voltage ride through time is set to a set value according to the specification, and the third threshold and the fourth threshold may be the same or different set values according to specific situations.
Example 3:
Considering that the standby power system may suffer from overall power loss, for safety, the high-power off-grid standby power system of this embodiment adds an under-voltage release with delay on the basis of embodiment 2, as shown in fig. 4.
The control method of the standby power system in this embodiment is the same as that in embodiment 2, and the under-voltage tripper automatically acts based on the power grid voltage induced by the under-voltage tripper, so that an upper computer is not required to implement control, and the auxiliary means for ensuring the safety of the system are provided.
The under-voltage release with the delay is also used for controlling the switching state of the circuit breaker body of the power grid, so that the delay value of the under-voltage release needs to exceed the preset low-voltage ride-through time so as to ensure that the false switching-off of the circuit breaker body is not caused during the low-voltage ride-through. Similarly, the undervoltage threshold corresponding to the undervoltage release should not be higher than a third threshold or a fourth threshold for judging whether the power grid side is in a low voltage state, so as to avoid the false brake opening of the breaker body.
The above embodiments are only for illustrating the technical concept and features of the present utility model, and are intended to enable those skilled in the art to understand the present utility model and to implement the same, but are not intended to limit the scope of the present utility model, and all equivalent changes or modifications made according to the spirit of the present utility model should be included in the scope of the present utility model.
Claims (10)
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| CN202422394534.9U CN223391135U (en) | 2024-09-30 | 2024-09-30 | A grid-connected and off-grid backup power system |
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| CN202422394534.9U CN223391135U (en) | 2024-09-30 | 2024-09-30 | A grid-connected and off-grid backup power system |
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