CN104333042A - Energy storage current transformer grid connection and grid disconnection seamless switching device and method - Google Patents

Abstract

The invention relates to an energy storage current transformer grid connection and grid disconnection seamless switching device and an energy storage current transformer grid connection and grid disconnection seamless switching method. The energy storage current transformer grid connection and disconnection seamless switching device is connected with a power grid monitoring system and a grid connection point switch, and comprises an energy storage current transformer, a controller, a battery management system, a battery pack and a first transformer, wherein the controller is connected with the power grid monitoring system, the energy storage current transformer and the battery management system, the battery pack is connected with the energy storage current transformer and the battery management system, the energy storage current transformer is connected with a first power grid bus through the first transformer, the controller is provided with a first interface connected with a voltage transformer, a second interface connected with the grid connection point switch and a third interface connected with a grid connection point switch position node, and the voltage transformer is arranged above the grid connection point switch. Compared with the prior art, the energy storage current transformer grid connection and grid disconnection seamless switching device and the energy storage current transformer grid connection and grid disconnection seamless switching method have the advantages of being capable of achieving high precision synchronism of grid disconnection to grid connection switching, achieving smooth grid connection to grid disconnection switching, being independent of a communication network and the like.

Description

A control device and method for seamless switching of energy storage converters on-grid and off-grid

technical field

The invention relates to the field of micro-grid control, in particular to an energy storage converter and an off-grid seamless switching control device and method.

Background technique

Large-scale energy storage technology is a cutting-edge technology. At present, only a few developed countries such as China, the European Union, and the United States have carried out research on this technology and achieved certain research results. However, many technical bottlenecks have not yet been broken through. Some domestic universities, scientific research institutes and equipment manufacturers have also begun to carry out related research on energy storage converters and off-grid seamless switching, and the technical routes are different, and the technology is immature in engineering application, mainly in the following aspects Outstanding issue:

1) When the energy storage converter is connected to the grid and switched to off-grid operation, it is impossible to realize the load without power loss and there is a large voltage fluctuation at the moment of off-grid startup;

2) When the energy storage converter is switched from off-grid to grid-connected operation (especially when it is switched to weak grid operation, such as diesel generators), it cannot smoothly switch to impact the grid, resulting in failure of the weak grid, and the energy storage converter carried by the energy storage converter The battery generates an instantaneous high current shock;

3) The energy storage converter itself cannot complete the automatic synchronization function, and the off-grid switching is heavily dependent on the synchronous detection and control accuracy of the configured on-grid and off-grid control device;

4) When the grid-connection point switch is not a high-speed electronic switch, due to the inconsistency of each action time of the switch and the long return time of the switch position node, it is impossible to accurately predict the closing time point of the switch, which will cause impact on the grid and The energy storage battery attached to the energy storage converter produces an instantaneous high current impact;

5) The energy storage converter relies heavily on the communication network to transmit information such as the voltage amplitude and phase angle of the grid at the grid-connected point during the synchronization process of the energy storage converter from the grid to the grid.

At present, the on-grid and off-grid switching of energy storage converters still needs to be realized by configuring on-grid and off-grid switching devices. The existing on-grid and off-grid switching devices mainly have the following disadvantages:

1) The synchronous control accuracy of the off-grid switching device is poor, resulting in the inability of the energy storage converter to switch smoothly from off-grid to grid-connected, impacting the power grid, causing a weak grid failure, and causing an instantaneous high current impact on the energy storage battery of the energy storage converter ;

2) After the on-grid and off-grid switching device separates and merges the outlet switch, the time delay in judging the switch position is long, which will also cause impact on the on-grid and off-grid switching, and seamless switching cannot be achieved;

3) When the consistency of the switch action time of the grid-connected point and the return time of the position node is poor, it will also cause impacts in the grid-connected and off-grid switching process, and seamless switching cannot be achieved;

4) The on-grid and off-grid switching device transmits information such as the voltage amplitude and frequency of the on-grid point to the energy storage converter through the communication network. When switching on and off the grid, the real-time communication cannot be guaranteed, which will also cause currents in the on-grid and off-grid switching. Shock, unable to achieve seamless switching;

5) The existing on-grid and off-grid switching is completed by the cooperation of the on-grid and off-grid switching device and the energy storage converter, and the real-time control is poor and the cost is high.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide an energy storage converter seamless switching control device for grid-connection and grid-connection, which can realize high-precision synchronism from off-grid to grid-connection, and realize smooth switching between grid-connection and grid-connection. method.

The purpose of the present invention can be achieved through the following technical solutions:

An energy storage converter connected to and off-grid seamless switching control device, respectively connected to a grid monitoring system and a grid-connected point switch, the control device includes an energy storage converter, a controller, a battery management system, a battery pack and a first transformer, The controller is respectively connected to the grid monitoring system, the energy storage converter, and the battery management system, the battery pack is respectively connected to the energy storage converter and the battery management system, and the energy storage converter is connected to the first The transformer is connected to the first power grid bus, and the controller is provided with a first interface for connecting a voltage transformer, a second interface for connecting a grid-connection point switch, and a third interface for connecting a grid-connection point switch position node , the voltage transformer is arranged on the upper side of the grid-connected point switch.

The controller is connected with the power grid monitoring system through a local area network.

The controller is provided with a three-phase voltage and current sampling loop on the upper side of the grid connection point, and the sampling loop is connected with a voltage transformer.

A control method for seamless on-off grid switching of energy storage converters, including planned on-grid switching control and unplanned on-grid switching control, wherein,

The planned grid-connection and off-grid switching control is specifically: after the controller receives the grid-connection and off-grid instruction issued by the grid monitoring system, the controller completes the opening operation of the grid-connection point switch through the grid-connection and off-grid control logic , and make the energy storage converter enter the off-grid operation mode; after the controller receives the off-grid to grid-connected command issued by the grid monitoring system, the controller completes the closing of the grid-connected point switch through the off-grid to grid-connected control logic operation, and make the energy storage converter enter the grid-connected operation mode;

The unplanned on-grid and off-grid switching control is specifically: after the controller detects the island protection action through the voltage transformer installed on the upper side of the grid-connected point switch, it automatically controls the switch-off of the grid-connected point switch, and makes the energy storage converter Enter the off-grid operation mode; after the controller detects that the upper side of the grid-connected point switch is live through the voltage transformer, it automatically controls the grid-connected point switch to close, and makes the energy storage converter enter the grid-connected operation mode.

In the planned grid-connected and off-grid switching control, the grid-connected to off-grid control logic is specifically: the controller sends the grid-connected point switch opening command, and switches the energy storage converter within 10 ms of quickly detecting the grid-connected point switch opening to the off-grid operation mode; the off-grid to grid-connected control logic is specifically: the controller sends the grid-connected point switch closing command, and switches the energy storage converter to the grid-connected within 10ms after quickly detecting the grid-connected point switch closing run mode.

In the above-mentioned unplanned on-off grid switching control, when the controller detects the island protection action, it issues an opening command of the grid-connecting point switch, and switches the energy storage converter to the off-grid operation mode with a delay of 10 ms; the controller After detecting that the upper side of the grid-connected point switch is charged, a command to close the grid-connected point switch is issued, and the energy storage converter is switched to the grid-connected operation mode within 10ms of the rapid detection of the grid-connected point switch closing.

The criterion for quickly detecting the opening or closing of the grid-connection point switch is judging the position node displacement of the grid-connection point switch or the sudden change of the three-phase instantaneous power of the grid-connection point.

Compared with the prior art, the present invention has the following advantages:

1) Set the three-phase voltage and current sampling circuit on the upper side of the grid-connected point switch, the opening and closing control interface of the grid-connected point switch, and the switch position node interface in the controller. At the same time, the voltage and current of the grid-connected point can be detected to solve the problem of energy storage converters. The problem of realizing high-precision synchronism from off-grid to grid-connected without the need for an off-grid switching device;

2) The controller integrates the on-off grid seamless switching interface and logic control function, and does not rely on the on-grid switching device and the communication network to complete the on-off grid seamless switching;

3) The control method does not depend on the switch type and action time of the grid-connected point, and can realize smooth and seamless switching between grid-connected and off-grid when different types of switches are selected at the grid-connected point, thereby ensuring that when the energy storage converter is switched on and off the grid, Reliable and stable load operation;

4) The control method has no impact on the energy storage converter and the grid when switching between on-grid and off-grid, so it is also suitable for grids with small short-circuit capacity;

5) The control method supports the parallel operation of multiple energy storage converters, so it is easy to expand the system;

6) During the switching process of on-grid and off-grid, the controller itself can automatically complete the synchronous function of on-grid;

7) It solves the problem of seamless switching between energy storage converters and off-grid in engineering applications, which is of great significance to the development of key energy storage technologies.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

As shown in Figure 1, a control device for seamless switching between grid-connected and off-grid energy storage converters is connected to the grid monitoring system 1 and the grid-connected point switch 3 respectively. The control device includes an energy storage converter 6, a controller 4, a battery The management system 5, the battery pack 7 and the first transformer 9, the controller 4 are connected to the power grid monitoring system 1 through a local area network, and are respectively connected to the energy storage converter 6 and the battery management system 5, and the battery pack 7 is respectively connected to the energy storage converter The energy storage converter 6 and the battery management system 5 are connected to the first grid bus 12 through the first transformer 9 . The controller 4 is provided with a first interface for connecting the voltage transformer 10, a second interface for connecting the grid connection point switch 3 and a third interface for connecting the grid connection point switch position node 11, and the voltage transformer 10 is located at On the upper side of the grid-connected point switch 3, the grid-connected point switch 3 is connected to the second grid bus 2 through the second transformer 13, and the controller 4 is provided with a three-phase voltage and current sampling circuit on the upper side of the grid-connected point, and the sampling circuit is connected to the voltage transformer 10 connected, the controller 4 can obtain the upper side three-phase power of the grid-connected point according to the collected voltage and current signals. The three-phase voltage and current sampling loop on the upper side of the grid-connected point is used for synchronous judgment of grid-connected to off-grid and off-grid to grid-connected; the controller directly controls the opening and closing of the grid-connected point switch through logical judgment, and real-time combination with the grid-connected point switch position The third interface connected to point 11 detects the position of the grid-connected point switch. In addition to completing the control of the energy storage converter 6, the controller 4 is also responsible for receiving the transmission of the on-grid switching control command issued by the grid monitoring system 1, so as to realize the seamless switching of the energy storage converter on the grid and off-grid. In this embodiment, the first grid bus 12 is a grid with a voltage level of 10kV, the second grid bus 2 is a grid with a voltage level of 10kV and above, and the first grid bus 12 is connected to an important load 8 .

The above-mentioned control method for the seamless switching control device of the energy storage converter includes planned on-grid and off-grid switching control and unplanned on-grid switching control, wherein,

The planned on-grid and off-grid switching control is specifically: after the controller 4 receives the grid-connected to off-grid command issued by the grid monitoring system 1, the controller 4 completes the opening of the grid-connected point switch 3 through the grid-connected to off-grid control logic operation, and make the energy storage converter 6 enter the off-grid operation mode; after the controller 4 receives the off-grid to grid-connected instruction issued by the grid monitoring system 1, the controller 4 completes the parallelism through the off-grid to grid-connected control logic Closing operation of the outlet switch 3, and making the energy storage converter 6 enter the grid-connected operation mode;

The unplanned grid-connected and off-grid switching control is specifically: after the controller 4 detects the island protection action through the voltage transformer 10 arranged on the upper side of the grid-connected point switch 3, it automatically controls the grid-connected point switch 3 to open, and makes the energy storage converter The controller 6 enters the off-grid operation mode; after the controller 4 detects that the upper side of the grid-connection point switch 3 is charged through the voltage transformer 10, it automatically controls the grid-connection point switch 3 to close, and makes the energy storage converter 6 enter the grid-connection operation mode.

In the planned on-grid switching control, the grid-connected to off-grid control logic is specifically: the controller 4 sends the grid-connected point switch opening command, and switches the energy storage converter 6 to In the off-grid operation mode, the criterion for quickly detecting the opening of the switch at the grid-connected point is to judge the position of the switch at the grid-connected point or the sudden change of the three-phase power at the grid-connected point, that is, the position of the switch at the grid-connected point or the three-phase instantaneous When the power changes suddenly, it is judged that the opening is successful; the off-grid to grid-connected control logic is specifically: the controller 4 sends the closing command of the grid-connecting point switch, and switches the energy storage converter 6 to In the grid-connected operation mode, the criterion for quickly detecting the closing of the grid-connected point switch is to judge the position of the grid-connected point switch or the sudden change of the three-phase power at the grid-connected point, that is, the position of the grid-connected point switch or the three-phase instantaneous power of the grid-connected point When the power changes suddenly, it is judged that the closing is successful.

In the unplanned on-off grid switching control, when the controller 4 detects the island protection action, it sends out the opening command of the grid-connecting point switch, and switches the energy storage converter 6 to the off-grid operation mode with a delay of 10ms; the controller 4 After detecting that the upper side of the grid-connection point switch 3 is electrified, a command to close the grid-connection point switch is issued, and the energy storage converter 6 is switched to the grid-connection operation mode within 10ms of fast detection of the grid-connection point switch closing, and the grid-connection point switch is quickly detected The criterion for closing is to judge the position of the switch at the grid-connected point and the node displacement or the sudden change of the three-phase instantaneous power at the grid-connected point.

Claims (7)

1. An energy storage converter connected to and off-grid seamless switching control device, which is respectively connected to a grid monitoring system (1) and a grid-connected point switch (3), characterized in that the control device includes an energy storage converter (6) , a controller (4), a battery management system (5), a battery pack (7) and a first transformer (9), and the controller (4) is respectively connected to the grid monitoring system (1), the energy storage converter ( 6), and the battery management system (5), the battery pack (7) is respectively connected to the energy storage converter (6) and the battery management system (5), and the energy storage converter (6) passes through the first A transformer (9) is connected to the first grid bus (12), and the controller (4) is provided with a first interface for connecting the voltage transformer (10) and a second interface for connecting the grid connection point switch (3). The second interface and the third interface for connecting the node (11) of the grid-connected point switch position, the voltage transformer (10) is arranged on the upper side of the grid-connected point switch (3). 2. The energy storage converter according to claim 1, characterized in that the controller (4) is connected to the grid monitoring system (1) through a local area network. 3. An energy storage converter according to claim 1, characterized in that the controller (4) is equipped with a three-phase voltage and current sampling circuit on the upper side of the grid connection point. , the sampling loop is connected with the voltage transformer (10). 4. A control method for an energy storage converter as claimed in claim 1, characterized in that it includes planned on-grid and off-grid switching control and unplanned on-grid and off-grid switching control, in, The planned grid-connection and off-grid switching control specifically includes: after the controller (4) receives the grid-connection to off-grid instruction issued by the power grid monitoring system (1), the controller (4) passes the grid-connection to off-grid control logic Complete the opening operation of the grid-connected point switch (3), and enable the energy storage converter (6) to enter the off-grid operation mode; the controller (4) receives the off-grid transfer from the grid monitoring system (1) After the instruction, the controller (4) completes the closing operation of the grid-connection point switch (3) through the off-grid to grid-connection control logic, and enables the energy storage converter (6) to enter the grid-connection operation mode; The unplanned on-grid and off-grid switching control is specifically: the controller (4) automatically controls the grid-connected point switch ( 3) Open the switch, and make the energy storage converter (6) enter the off-grid operation mode; the controller (4) detects that the upper side of the grid-connection point switch (3) is charged through the voltage transformer (10), and automatically controls the grid-connection point The switch (3) is closed, and the energy storage converter (6) enters the grid-connected operation mode. 5. The control method for seamless switching between grid-connected and off-grid converters according to claim 4, characterized in that, in the planned grid-connected and off-grid switching control, the control logic for grid-connected and off-grid transitions is specifically: control The converter (4) sends the opening command of the grid-connection point switch, and switches the energy storage converter (6) to the off-grid operation mode within 10 ms of quickly detecting the grid-connection point switch opening; the off-grid to grid-connection control logic is specific It is: the controller (4) sends a closing command of the grid-connecting point switch, and switches the energy storage converter (6) to the grid-connecting operation mode within 10 ms of quickly detecting the closing of the grid-connecting point switch. 6. The method for seamless switching control of energy storage converters according to claim 4, characterized in that, in the unplanned control of switching between grid and off-grid, the controller (4) detects an island protection action At the same time, it sends the opening command of the grid-connected point switch, and switches the energy storage converter (6) to the off-grid operation mode with a delay of 10ms; after the controller (4) detects that the upper side of the grid-connected point switch (3) is charged, it sends out The closing command of the grid-connecting point switch switches the energy storage converter (6) to the grid-connecting operation mode within 10 ms of fast detection of the closing of the grid-connecting point switch. 7. The control method for grid-connected and off-grid seamless switching of energy storage converters according to claim 5 or 6, wherein the criterion for quickly detecting the opening or closing of the grid-connecting point switch is to judge the grid-connecting point Switch position node displacement or sudden change of three-phase instantaneous power at grid-connected point.