CN111064178A - Self-discipline floating micro-grid system and control method thereof - Google Patents
Self-discipline floating micro-grid system and control method thereof Download PDFInfo
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- CN111064178A CN111064178A CN201811203152.6A CN201811203152A CN111064178A CN 111064178 A CN111064178 A CN 111064178A CN 201811203152 A CN201811203152 A CN 201811203152A CN 111064178 A CN111064178 A CN 111064178A
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/12—Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
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Abstract
The invention relates to an autonomous floating micro-grid system and a control method thereof, wherein the system comprises: a bus bar; a main bus; an alternating current bus; the power generation device is connected to the bus bar; the energy storage device is connected to the main bus; a first control unit that connects the bus bar and the main bus bar; a second control unit that connects the bus bar and the ac bus bar; the converter device is connected with the alternating current bus and the main bus; the load is connected into the main bus; and the connecting device is used for connecting the alternating-current bus into an external alternating-current power grid. Compared with the prior art, the invention does not need a micro-grid centralized control system, reduces control objects and complexity to the maximum extent, utilizes a natural rectification outlet of an external alternating current power grid as a micro-grid voltage support base, reduces investment of interface power electronic equipment and reduces systematic risks.
Description
Technical Field
The invention relates to the technical field of direct-current micro-grids, in particular to an autonomous floating micro-grid system and a control method thereof.
Background
With the gradual maturity and wide application of distributed energy technology, the application of new energy-based microgrid technology is also rapidly developed, wherein a direct-current microgrid has natural advantages as a hotspot for research and application. In a direct-current micro-grid, a direct-current power supply is a power supply mode of a main network, and a large number of distributed direct-current power supplies and energy storage systems directly supply power for direct-current loads through a direct-current main network frame.
In the direct-current micro-grid, bus voltage is the only index for measuring power balance. The voltage stabilization in the network depends on the power balance of the power supply side and the load side, and comprises steady-state stability and dynamic stability, wherein the steady-state stability means that the power balance of the power supply and the load is realized under the condition of the steady state of the system, so that the voltage of a direct current bus is kept floating within an acceptable range; the dynamic stability refers to the dynamic stability of the system when the power generation or load mutation occurs, so that the system cannot have the effect of expandability.
At present, control strategies of a direct-current microgrid are divided into a master-slave control mode and an equivalent control mode. The master-slave mode control structure is complex, a central controller needs to be configured, and the investment cost is high; peer-to-peer control is prone to errors, and control parameter configuration is complex.
Regardless of the control strategy, the stability of the bus voltage is the control target. In the direct-current microgrid, the number of distributed power supplies is large, and the number of control objects determines the complexity of design and implementation of a control strategy. The core of the current mainstream control algorithm is a voltage-power droop control method. The control parameter configuration is complex, and meanwhile, controllable power converter devices with the number equal to that of the distributed power supplies are needed, so that the investment cost is high.
With the development of power electronic technology and energy storage technology, the voltage static stability floating margin of the direct-current micro-grid is gradually enlarged, and the dynamic stability is effectively improved.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an autonomous floating microgrid system and a control method thereof.
The purpose of the invention can be realized by the following technical scheme:
an autonomous floating microgrid system comprising:
a bus bar;
a main bus;
an alternating current bus;
the power generation device is connected to the bus bar;
the energy storage device is connected to the main bus;
a first control unit that connects the bus bar and the main bus bar;
a second control unit that connects the bus bar and the ac bus bar;
the converter device is connected with the alternating current bus and the main bus;
the load is connected into the main bus;
and the connecting device is used for connecting the alternating-current bus into an external alternating-current power grid.
Preferably, the control unit includes:
the detection module is used for detecting the bus voltage of the bus and the main bus;
and the execution module is used for executing on-off and current transformation.
Preferably, the power generation device is a distributed energy source, and specifically includes:
the photovoltaic power generation device is connected to the bus bar through the DC/DC converter, and/or the wind power generation device is connected to the bus bar through the AC/DC converter, and/or the fuel cell pack is connected to the bus bar through the DC/DC converter.
A control method of the autonomous floating micro-grid system comprises the following steps:
when the bus voltage of the bus bar is higher than the bus voltage of the main bus and lower than the main bus upper limit voltage Umax, the bus bar is merged into the main bus to supply power to the load or the energy storage device, and when the bus voltage of the bus bar is lower than the main bus voltage or higher than the main bus upper limit voltage Umax, the bus bar is merged into the alternating current bus to invert the power into the alternating current bus.
Preferably, the control unit is used for controlling the on-off and current transformation of the bus bar, the main bus and the alternating current bus.
Preferably, the detection module detects a bus voltage difference between the bus bar and the main bus bar; the execution module executes on-off or inversion operation according to the voltage difference between the bus bar and the main bus detected by the detection module.
Preferably, the upper limit voltage Umax of the main bus is X% of the energy storage full charge voltage, and the lower limit voltage of the main bus is the rectified outlet voltage value of the converter.
Preferably, the X% is a point where the energy storage device changes from constant-current charging to constant-voltage charging or any other percentage which is beneficial to energy storage and improves the use efficiency and reliability.
Preferably, said energy storage means is connected to said main bus by a DC/DC means.
Preferably, the load is a direct current load and an alternating current load of each voltage class, and the access mode is direct connection or connection through a DC/DC or DC/AC device.
Compared with the prior art, the direct-current micro-grid system coordination control method provided by the invention has the advantages that the voltage difference between the direct-current bus and the main bus is detected in real time through the detection module, and the execution module controls the energy flow between the bus and the direct-current bus or the alternating-current bus in real time according to the result detected by the detection module.
Compared with the existing mainstream microgrid control technology, the method has the advantages that a microgrid centralized control system is not needed, control objects and complexity are reduced to the greatest extent, and the natural rectification outlet of an external alternating current power grid is used as a microgrid voltage support base, so that investment of interface power electronic equipment is reduced, and systematic risks are reduced.
Drawings
FIG. 1 is a schematic structural diagram of an autonomous floating type DC micro-grid system according to the present invention;
fig. 2 is a flow chart of the control method of the autonomous floating type direct current micro-grid system of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
Referring to fig. 1, fig. 1 is a schematic diagram of an autonomous floating type dc microgrid according to an embodiment of the present invention.
The direct current microgrid comprises:
the detection module 100: the bus voltage detection device is used for detecting the bus voltage of the bus and the main bus;
a direct current main Bus (DC Bus1) 301; a direct current Bus bar (DC Bus2) 302;
a first execution module (Breaker1)201 connecting the DC main bus 301 and the DC bus bar 302;
an Energy Storage System (ESS)304 connected to the main DC bus 301 via a DC/DC converter 303;
a Load (Load)306 connected to the DC main bus 301 through a DC/DC converter or DC/AC converter 305;
the power generation device connected to the dc bus bar 302 may be a distributed energy source, and specifically may include but is not limited to: distributed energy sources such as a photovoltaic power generation device (PV)308 connected to the direct current bus bar 302 through a DC/DC converter 307, and/or a Wind power generation device (Wind)310 connected to the direct current bus bar 302 through an AC/DC converter 309, and/or a fuel cell stack (FC)312 connected to the direct current bus bar through a DC/DC converter 311;
an alternating current grid-connected device (PCC)403 connected to the direct current main bus 301 through an AC/DC converter 401;
meanwhile, the PCC is connected to the DC bus bar 302 through the DC/AC converter 402 and the second actuator module (Breaker2) 202.
The implementation method of the invention also provides an autonomous voltage floating microgrid control method, which is shown in figure 2. The direct-current micro-grid comprises a direct-current bus bar, a direct-current main bus bar, an alternating-current bus bar, a power generation device connected into the bus bar, an energy storage device connected into the main bus bar, a first control unit connected between the bus bar and the main bus bar, a second control unit connected between the bus bar and the alternating-current bus bar, a current transformation device connected between the alternating-current bus bar and the main bus bar, and a load connected into the main bus bar, wherein the alternating-current bus bar is connected into a connecting device of an external alternating-current power grid. The control unit is used for controlling the on-off of the bus bar, a main bus and an alternating current bus, when the bus voltage of the bus bar is higher than the bus voltage of the main bus and lower than the main bus upper limit voltage Umax, the bus bar is merged into the main bus to supply power to the load or the energy storage, and when the bus voltage of the bus bar is lower than the main bus voltage or higher than the main bus upper limit voltage Umax, the bus bar is merged into the alternating current bus to invert the power to enter the alternating current bus, the method comprises the following steps:
s1, the bus voltage difference between the bus and the main bus is detected by the detection module;
s2, the execution module executes on-off or inversion operation according to the voltage difference between the bus bar and the main bus detected by the detection module;
the upper limit voltage Umax of the main bus is X% of the energy storage full charge voltage, and the lower limit of the main bus voltage is the rectifying outlet voltage value of the converter.
And the X% is the percentage of the point where the energy storage constant current charging is converted into the constant voltage charging or any other point which is beneficial to energy storage and improvement of the use efficiency and the reliability.
The stored energy is connected to the main bus by a DC/DC device.
The power generation device includes but is not limited to: photovoltaic power generation devices, wind power generation devices, fuel cells, and the like.
The load is a direct current load and an alternating current load of each voltage grade, and the access modes are direct connection, connection through a DC/DC device and a DC/AC device and the like.
While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An autonomous floating microgrid system, comprising:
a bus bar;
a main bus;
an alternating current bus;
the power generation device is connected to the bus bar;
the energy storage device is connected to the main bus;
a first control unit that connects the bus bar and the main bus bar;
a second control unit that connects the bus bar and the ac bus bar;
the converter device is connected with the alternating current bus and the main bus; the load is connected into the main bus;
and the connecting device is used for connecting the alternating-current bus into an external alternating-current power grid.
2. The autonomous floating microgrid system of claim 1, wherein the control unit comprises:
the detection module is used for detecting the bus voltage of the bus and the main bus;
and the execution module is used for executing on-off and current transformation.
3. The autonomous floating microgrid system of claim 1, wherein the power generation device is a distributed energy source, and specifically comprises:
the photovoltaic power generation device is connected to the bus bar through the DC/DC converter, and/or the wind power generation device is connected to the bus bar through the AC/DC converter, and/or the fuel cell pack is connected to the bus bar through the DC/DC converter.
4. A control method using the autonomous floating microgrid system according to claim 2, characterized by comprising the steps of:
when the bus voltage of the bus bar is higher than the bus voltage of the main bus and lower than the main bus upper limit voltage Umax, the bus bar is merged into the main bus to supply power to the load or the energy storage device, and when the bus voltage of the bus bar is lower than the main bus voltage or higher than the main bus upper limit voltage Umax, the bus bar is merged into the alternating current bus to invert the power into the alternating current bus.
5. The method as claimed in claim 4, wherein the control unit is used for controlling the on-off and the variable current of the bus bar, the main bus bar and the alternating current bus bar.
6. The method of claim 5, wherein the detection module detects a bus bar voltage difference between the bus bar and a main bus bar; the execution module executes on-off or inversion operation according to the voltage difference between the bus bar and the main bus detected by the detection module.
7. The method as claimed in claim 4, wherein the main bus upper limit voltage Umax is X% of the energy storage full charge voltage, and the main bus lower limit voltage is the rectified outlet voltage value of the converter.
8. The method of claim 7, wherein X% is a constant current charging to constant voltage charging point of the energy storage device or any other percentage that is beneficial for improving the efficiency and reliability of energy storage.
9. A method according to claim 4, wherein the energy storage device is connected to the main bus by a DC/DC device.
10. The method according to claim 4, wherein the loads are DC loads and AC loads of various voltage classes, and the connection mode is direct connection or connection through DC/DC or DC/AC devices.
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