CN112713645A - Energy storage system grid-connected and off-grid switching system and switching method - Google Patents
Energy storage system grid-connected and off-grid switching system and switching method Download PDFInfo
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- CN112713645A CN112713645A CN202011513733.7A CN202011513733A CN112713645A CN 112713645 A CN112713645 A CN 112713645A CN 202011513733 A CN202011513733 A CN 202011513733A CN 112713645 A CN112713645 A CN 112713645A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
- H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
- H02J9/062—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for AC powered loads
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
Abstract
A grid-connected and off-grid switching system and a switching method of an energy storage system comprise a grid-connected and off-grid switching device STS and a bidirectional energy storage converter PCS; the grid-connected and off-grid switching device STS comprises a controller, a thyristor SCR, a primary relay and a secondary relay; a primary relay and a secondary relay in a main circuit of the off-grid switching device STS are sequentially connected, and a thyristor SCR is connected to the secondary relay in parallel; and a controller of a control circuit of the off-grid switching device STS is connected with the two-stage relay and the thyristor SCR. The SCR is connected in parallel at two ends of the relay, when the relay is disconnected from a network, the SCR and the relay can send signals at the same time, because the semiconductor switch is high in speed, the SCR can be switched on first, and when the relay acts, no voltage difference exists between two sides of the relay, so that the relay cannot be pulled to be arc when the relay is disconnected, and the relay is adhered.
Description
Technical Field
The invention belongs to the technical field of energy conversion of energy storage systems, and particularly relates to a grid-connected and off-grid switching system and a switching method for an energy storage system.
Background
In recent years, with the development of power electronic technology, energy storage technology has received more and more attention, and has become one of indispensable conditions in the application aspects of micro-grid, distributed power generation and the like, and fast grid-connected and off-grid switching is a key node for bringing the energy storage technology into play. The energy storage technology and the advanced electric energy conversion and control technology are combined, so that the effects of peak clipping, valley filling, electric energy quality improvement, power grid characteristic improvement and the like can be realized, the requirements of a power grid side are met, and the requirements of a user side are also met.
The PCS has two working modes, namely a grid-connected working mode and an off-grid working mode. When the power grid is normal, the PCS and the power grid supply power to the load together, or the PCS charges the battery and the power grid supplies power to the load. When the power grid is abnormal, the PCS is separated from the power grid to operate independently and supplies power to the load independently. And the PCS adopts PQ control during grid-connected work, and is equivalent to a current source to output power under the conditions of following the voltage and frequency of a power grid. When the off-grid operation is carried out, the PCS is controlled by V/f, and is equivalent to a voltage source, so that the load power is ensured under the condition of providing voltage and frequency support for the load.
The PCS can not switch the working mode at will when working, if the mains supply is abnormal when the PCS is in grid-connected work, the PCS cannot detect the fault in time, the PCS is not switched into the off-grid working mode, the fault is reported, and the load is shut down possibly at the moment. If the PCS supplies power to the load independently during off-grid operation, the load is required to be disconnected from the power grid, otherwise, the output voltage of the PCS and the mains voltage are connected together under the condition that the phase amplitudes are different, and equipment can be damaged. After the STS is added, the STS is used for detecting the commercial power, controlling the PCS to switch the working mode and controlling the connection of the load and the power grid. When grid connection works, when the voltage or frequency of a power grid is abnormal, the STS disconnects a load and the power grid, controls the PCS to be converted into an off-grid working mode, and supplies power to the load by the PCS alone. When the off-grid operation is carried out, the STS detects that the mains supply is normal, and when the PCS voltage is consistent with the mains supply voltage, the relay is closed to control the PCS to be converted into a grid-connected operation mode. By adopting the cooperation of the STS and the PCS, the rapid conversion of the PCS from grid connection to grid disconnection and from grid disconnection to grid connection can be completed, and particularly under the condition of unplanned power failure, uninterrupted power supply of a load can be reliably ensured.
Disclosure of Invention
The invention aims to provide a grid-connected and off-grid switching system and a switching method for an energy storage system, so as to solve the problems.
In order to achieve the purpose, the invention adopts the following technical scheme:
a grid-connected and off-grid switching system of an energy storage system comprises a grid-connected and off-grid switching device STS and a bidirectional energy storage converter PCS; the grid-connected and off-grid switching device STS comprises a controller, a thyristor SCR, a primary relay and a secondary relay; a primary relay and a secondary relay in a main circuit of the off-grid switching device STS are sequentially connected, and a thyristor SCR is connected to the secondary relay in parallel; and a controller of a control circuit of the off-grid switching device STS is connected with the two-stage relay and the thyristor SCR.
Furthermore, one end of the bidirectional energy storage converter PCS is connected with the storage battery, the other end of the bidirectional energy storage converter PCS is connected with the load and a secondary relay end of the grid-connected and off-grid switching device STS, and a primary relay end of the grid-connected and off-grid switching device STS is connected with the mains supply.
The grid connection and disconnection specifically comprises the following steps:
under the condition that the commercial power is normally supplied, the PCS and the two-stage relay are closed, and the PCS is in grid-connected operation;
when the grid-connected and off-grid switching device STS detects that the amplitude or frequency of the input voltage Uin exceeds the range of normal voltage or normal frequency, the SCR connected with the secondary relay in parallel is firstly switched on, the secondary relay is switched off, then the SCR is switched off, a switching off-grid command is sent to the PCS in a delayed mode, and finally the primary relay is switched off after the SCR is reliably switched off;
if the commercial power is detected to be in a power-off condition, a switching command is sent to the PCS while the secondary relay is switched off, and after the PCS receives the command of switching off the network, control mode conversion is immediately carried out, energy is output externally, and power is supplied to a load;
the off-grid switching and grid connection method specifically comprises the following steps:
when the mains supply is abnormal, the STS, the two-stage relay and the SCR are disconnected, and the PCS is operated off-grid;
when STS detects that the amplitude or frequency of input voltage Uin is restored to the range of normal voltage or normal frequency, firstly informing PCS that the commercial power is normal, closing a primary relay after receiving a prepared sign of PCS, then switching on an SCR (silicon controlled rectifier) connected with the secondary relay in parallel at a voltage zero crossing point, closing the secondary relay, simultaneously sending a grid connection and disconnection command to the PCS, and switching off the SCR after the secondary relay is reliably closed;
after receiving the normal mark of the commercial power, the PCS carries out phase-locking and amplitude-locking preparation work, replies a signal after the preparation, and carries out control mode conversion after receiving a grid-connection switching command and delaying.
Furthermore, if the waveform of the mains supply is poor, after the STS informs the PCS that the mains supply is normal, the preparation time of the STS exceeds the confirmation time of the preparation of the PCS, the STS firstly sends a wave-sealing command to the PCS, the STS performs switching action after the PCS finishes the wave-sealing action, the STS finishes the switching action and then sends a wave-transmitting command to the PCS, the PCS stops outputting after receiving the wave-sealing command and switches the working mode, and the PCS starts working according to the grid-connected working mode after receiving the wave-transmitting command.
Further, the grid-connected mode working process:
step 1: STS real-time detecting the mains voltage;
step 2: judging whether the voltage frequency of the mains supply is abnormal or the mains supply is powered off;
and step 3: determining whether to switch and which switching sequence to switch according to the commercial power state judged in the step 2;
and 4, step 4: controlling the two-stage relay and the silicon controlled rectifier SCR to act according to the switching time sequence determined in the step 3;
and 5: and 4, sending a switching command to the PCS to control the PCS to switch the working mode while operating in the step 4.
Further, the off-grid mode working process:
step 1: STS real-time detecting the mains voltage;
step 2: judging whether the commercial power is recovered to be normal;
and step 3: sending a signal of normal commercial power to the PCS according to the judgment result of the step 2;
and 4, step 4: and determining the action time sequence of the two-stage relay and the SCR according to the signal returned by the PCS.
And 5: and (4) controlling the action of the two-stage relay and the SCR according to the time sequence determined in the step (4).
Compared with the prior art, the invention has the following technical effects:
the SCR is connected in parallel at two ends of the relay, when the relay is disconnected from a network, the SCR and the relay can send signals at the same time, because the semiconductor switch is high in speed, the SCR can be switched on first, and when the relay acts, no voltage difference exists between two sides of the relay, so that the relay cannot be pulled to be arc when the relay is disconnected, and the relay is adhered.
According to different conditions of mains supply faults, different times are selected to send switching commands to the PCS. When the mains supply is powered off, a command of switching off the network is sent to the PCS at the same time when the switching action starts, and the purpose is to supply power to the load at the fastest speed and reduce the power-off time of the load. When the frequency and the voltage are abnormal, a time delay is carried out for a period of time after the SCR is turned off, and a network disconnection command is sent to the PCS, so that the relay can be ensured to be reliably turned off when the PCS is switched in a control mode, and the condition that the commercial power and the PCS are shared to cause PCS damage is prevented. Therefore, the relay can be ensured to be switched off in a zero current state, and the power-off time of the load can be reduced.
When the relay is switched on and switched off, the relay is closed at the voltage zero crossing point, so that current impact generated after the relay is closed at high voltage is prevented, the relay is protected, and the service life of the relay is prolonged.
Drawings
FIG. 1 is a system diagram of the present invention;
FIG. 2 is a flow chart of the present invention for cutting off a web;
fig. 3 is a cut-and-tie flow chart of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
the PCS is a bidirectional energy storage converter, can be connected with a power grid to work, and can also work independently without the power grid. The STS is internally provided with a set of complete closed-loop control system which comprises a controller, a sampling interface, an output interface and external communication.
After being electrified, the STS can determine the working state of the STS according to the current commercial power and the working state of the PCS.
If the system works in a grid-connected mode
Step 1: STS detects the mains voltage in real time.
Step 2: judging whether the frequency of the mains supply voltage is abnormal or the mains supply is powered down
And step 3: and (4) determining whether to switch and which switching time sequence according to the commercial power state judged in the step (2).
And 4, step 4: and (4) controlling the two-stage relay and the silicon controlled rectifier SCR to act according to the switching time sequence determined in the step (3).
And 5: and 4, sending a switching command to the PCS to control the PCS to switch the working mode while operating in the step 4.
If operating in off-grid mode
Step 1: STS detects the mains voltage in real time.
Step 2: and judging whether the commercial power is recovered to be normal or not.
And step 3: and (4) sending a normal commercial power signal to the PCS according to the judgment result in the step (2).
And 4, step 4: and determining the action time sequence of the two-stage relay and the SCR according to the signal returned by the PCS.
And 5: and (4) controlling the action of the two-stage relay and the SCR according to the time sequence determined in the step (4).
The two-stage relay and SCR timing, and cooperation with the PCS,
1. grid-connected and off-grid
And under the normal condition of the mains supply, the PCS two-stage relays are closed, and the PCS is in grid-connected operation. When the STS power supply alternative automatic switching system detects that the amplitude or the frequency of the input voltage Uin exceeds the range of normal voltage or normal frequency, the SCR connected with the secondary relay in parallel is firstly switched on, the secondary relay is switched off, then the SCR is switched off, a switching off-network command is sent to the PCS in a delayed mode, and finally the primary relay is switched off after the SCR is reliably switched off. If the commercial power is detected to be in a power-down condition, a switching command is sent to the PCS while the secondary relay is switched off. After receiving the command of switching off the network, the PCS immediately carries out control mode conversion, outputs energy to the outside and supplies power to the load.
2. Off-grid switching and grid connection
When the mains supply is abnormal, both the STS two-stage relay and the SCR are disconnected, and the PCS is operated off the network. When STS detects that the amplitude or frequency of input voltage Uin is restored to the range of normal voltage or normal frequency, firstly informing PCS that the commercial power is normal, after receiving a prepared sign of PCS, confirming for a period of time, closing a first-stage relay, then switching on an SCR (silicon controlled rectifier) connected with a second-stage relay in parallel at a voltage zero crossing point, closing the second-stage relay, simultaneously sending a grid connection switching command to the PCS, and switching off the SCR after the second-stage relay is reliably closed. After receiving the normal mark of the commercial power, the PCS carries out preparation work such as phase locking, amplitude locking and the like, and replies a signal after the preparation is carried out. After receiving the grid switching and connecting command, the control mode is switched after delaying for a period of time.
If the waveform of the mains supply is poor, after the STS informs the PCS that the mains supply is normal, the STS can not be prepared all the time and exceeds the confirmation time of the preparation of the PCS, the STS firstly sends a wave-sealing command to the PCS, after the PCS finishes the wave-sealing action, the STS carries out switching action, and the STS finishes the switching and then sends a wave-sending command to the PCS. And after receiving the wave-blocking command, the PCS stops outputting, converts the working mode and starts working according to the grid-connected working mode after receiving the wave-sending command.
English abbreviation, PCS: a bidirectional energy storage converter. STS: and an off-grid switching device. SCR: a thyristor.
Claims (6)
1. A grid-connected and off-grid switching system of an energy storage system is characterized by comprising a grid-connected and off-grid switching device STS and a bidirectional energy storage converter PCS; the grid-connected and off-grid switching device STS comprises a controller, a thyristor SCR, a primary relay and a secondary relay; a primary relay and a secondary relay in a main circuit of the off-grid switching device STS are sequentially connected, and a thyristor SCR is connected to the secondary relay in parallel; and a controller of a control circuit of the off-grid switching device STS is connected with the two-stage relay and the thyristor SCR.
2. The energy storage system grid-connected and grid-disconnected switching system according to claim 1, wherein one end of the bidirectional energy storage converter PCS is connected with the storage battery, the other end of the bidirectional energy storage converter PCS is connected with a secondary relay end of the load and grid-connected and grid-disconnected switching device STS, and a primary relay end of the grid-connected and grid-disconnected switching device STS is connected with commercial power.
3. A switching method of an energy storage system grid-connected and off-grid switching system, wherein the energy storage system grid-connected and off-grid switching system is based on any one of claims 1 to 2, and comprises: grid connection and disconnection and grid connection;
the grid connection and disconnection specifically comprises the following steps:
under the condition that the commercial power is normally supplied, the PCS and the two-stage relay are closed, and the PCS is in grid-connected operation;
when the grid-connected and off-grid switching device STS detects that the amplitude or frequency of the input voltage Uin exceeds the range of normal voltage or normal frequency, the SCR connected with the secondary relay in parallel is firstly switched on, the secondary relay is switched off, then the SCR is switched off, a switching off-grid command is sent to the PCS in a delayed mode, and finally the primary relay is switched off after the SCR is reliably switched off;
if the commercial power is detected to be in a power-off condition, a switching command is sent to the PCS while the secondary relay is switched off, and after the PCS receives the command of switching off the network, control mode conversion is immediately carried out, energy is output externally, and power is supplied to a load;
the off-grid switching and grid connection method specifically comprises the following steps:
when the mains supply is abnormal, the STS, the two-stage relay and the SCR are disconnected, and the PCS is operated off-grid;
when STS detects that the amplitude or frequency of input voltage Uin is restored to the range of normal voltage or normal frequency, firstly informing PCS that the commercial power is normal, closing a primary relay after receiving a prepared sign of PCS, then switching on an SCR (silicon controlled rectifier) connected with the secondary relay in parallel at a voltage zero crossing point, closing the secondary relay, simultaneously sending a grid connection and disconnection command to the PCS, and switching off the SCR after the secondary relay is reliably closed;
after receiving the normal mark of the commercial power, the PCS carries out phase-locking and amplitude-locking preparation work, replies a signal after the preparation, and carries out control mode conversion after receiving a grid-connection switching command and delaying.
4. The switching method of the energy storage system grid-connected and off-grid switching system as claimed in claim 3, wherein if the waveform of the utility power is poor, after the STS notifies the PCS that the utility power is normal, the preparation time of the STS exceeds the confirmation time of the preparation of the PCS, the STS first sends a wave-sealing command to the PCS, waits for the PCS to complete the wave-sealing action, the STS performs the switching action, the STS completes the switching action and then sends a wave-transmitting command to the PCS, the PCS stops outputting and switches the operation mode after receiving the wave-sealing command, and the PCS starts to operate according to the grid-connected operation mode after receiving the wave-transmitting command.
5. The switching method of the grid-connected and off-grid switching system of the energy storage system according to claim 3, characterized in that the working process of the grid-connected mode is as follows:
step 1: STS real-time detecting the mains voltage;
step 2: judging whether the voltage frequency of the mains supply is abnormal or the mains supply is powered off;
and step 3: determining whether to switch and which switching sequence to switch according to the commercial power state judged in the step 2;
and 4, step 4: controlling the two-stage relay and the silicon controlled rectifier SCR to act according to the switching time sequence determined in the step 3;
and 5: and 4, sending a switching command to the PCS to control the PCS to switch the working mode while operating in the step 4.
6. The switching method of the energy storage system grid-connected and off-grid switching system according to claim 3, characterized in that the off-grid mode working process comprises:
step 1: STS real-time detecting the mains voltage;
step 2: judging whether the commercial power is recovered to be normal;
and step 3: sending a signal of normal commercial power to the PCS according to the judgment result of the step 2;
and 4, step 4: determining the action time sequence of the two-stage relay and the SCR according to the signal replied by the PCS;
and 5: and (4) controlling the action of the two-stage relay and the SCR according to the time sequence determined in the step (4).
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113765147A (en) * | 2021-11-09 | 2021-12-07 | 万帮数字能源股份有限公司 | Switching device, system and method |
| CN114069696A (en) * | 2021-11-12 | 2022-02-18 | 中国葛洲坝集团装备工业有限公司 | Method and equipment for enhancing reliability of silicon controlled rectifier grid-connected and off-grid switching device of microgrid |
| CN116667518A (en) * | 2023-07-24 | 2023-08-29 | 山东华天电气有限公司 | Direct-current voltage sag management circuit and control method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113765147A (en) * | 2021-11-09 | 2021-12-07 | 万帮数字能源股份有限公司 | Switching device, system and method |
| CN114069696A (en) * | 2021-11-12 | 2022-02-18 | 中国葛洲坝集团装备工业有限公司 | Method and equipment for enhancing reliability of silicon controlled rectifier grid-connected and off-grid switching device of microgrid |
| CN114069696B (en) * | 2021-11-12 | 2024-04-02 | 中国葛洲坝集团装备工业有限公司 | Method and equipment for enhancing reliability of micro-grid silicon controlled rectifier off-grid switching device |
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| CN116667518B (en) * | 2023-07-24 | 2023-10-27 | 山东华天电气有限公司 | Direct-current voltage sag management circuit and control method thereof |
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