CN108512212B - Distributed control method for multi-voltage-level direct-current distribution network accessed to distributed power supply - Google Patents
Distributed control method for multi-voltage-level direct-current distribution network accessed to distributed power supply Download PDFInfo
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- CN108512212B CN108512212B CN201810345844.8A CN201810345844A CN108512212B CN 108512212 B CN108512212 B CN 108512212B CN 201810345844 A CN201810345844 A CN 201810345844A CN 108512212 B CN108512212 B CN 108512212B
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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
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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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- 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
- H02J1/08—Three-wire systems; Systems having more than three wires
- H02J1/082—Plural DC voltage, e.g. DC supply voltage with at least two different DC voltage levels
Abstract
The invention relates to a new energy power generation direct current distribution technology, and aims to provide a distributed control method of a multi-voltage-level direct current distribution network connected with a distributed power supply. The invention realizes the interconnection between high and low voltage direct current buses by using the direct current transformer and realizes the voltage grade conversion and isolation between high and low voltage direct currents. Through droop control of a plurality of distributed power supplies and constant transformation ratio control of a direct current transformer between high voltage and low voltage direct current, seamless energy flow in the whole direct current distribution network area is realized without switching a control mode. When the high-voltage direct-current distribution network works in a master-slave control mode, voltage constancy of the whole distribution network region can be realized only by one voltage support source on one side, and the control mode of a direct-current transformer does not need to be changed for power flow and control mode conversion in the whole high-low voltage direct-current distribution network region, so that integrated control of a multi-voltage-level or multi-region direct-current distribution network is realized, and the control difficulty of the direct-current distribution network is greatly reduced.
Description
Technical Field
The invention relates to an operation and control method of a multi-voltage-level direct-current distribution network system, and belongs to the technical field of new energy power generation direct-current distribution.
Background
Direct current distributed power generation systems are gaining more and more attention due to their high efficiency and easy control characteristics. In the future, direct current power distribution and alternating current-direct current hybrid power distribution are the development trend. Dc distribution networks typically have different power supply areas and different dc voltage levels to fulfill the requirements of different types of loads.
Interconnection and voltage conversion are generally realized among different voltage classes in the field of direct-current distribution networks through a DC/DC power electronic transformer, the existing DC/DC conversion technology has an isolation type and a non-isolation type, and the isolation type DC/DC can realize electric appliance isolation and fault isolation among different direct-current voltage classes, so that the method has important application significance. The current control technology of the DC/DC conversion module in the field of direct current distribution or power supply mainly comprises current mode control and voltage mode control, wherein the voltage mode control is more widely applied. The DC/DC converter voltage type control method takes direct-current voltage at one end as a control target, and can realize bidirectional flow of energy at high-voltage and low-voltage direct-current sides. The control mode must be switched when the reverse voltage support is realized, so for a direct-current distribution network with a complex structure and a high-density distributed power supply, the operation scene and the control mode are changeable, and each DC/DC converter cannot be directly controlled in an active centralized control mode. Therefore, at present, a direct-current distribution network is researched more in the field of direct-current microgrids, and when the direct-current distribution network is expanded to a direct-current distribution network with a large-scale distributed power supply, many problems are encountered, and research results are few. Aiming at the problem, the invention provides a novel DC/DC direct current transformer control method in a direct current distribution network and an operation control mode of the whole direct current distribution network.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the existing direct current distribution control technology, provides a distributed control method of a multi-voltage-level direct current distribution network connected with a distributed power supply, different direct current voltage-level buses are interconnected through direct current transformers, and provides a novel control mode of the direct current transformers, so that the distributed control of the whole multi-voltage-level direct current distribution network is realized.
In order to solve the technical problem, the solution of the invention is as follows:
the invention provides a distributed control method of a multi-voltage-level direct-current distribution network accessed to a distributed power supply, wherein the multi-voltage-level direct-current distribution network comprises two or more direct-current buses with different voltage levels, and the distributed power supply, the load and the energy storage equipment matched with respective operating voltages are respectively accessed; in two direct current buses of adjacent voltage levels, a direct current bus with higher voltage is called a high-voltage direct current bus, and a direct current bus with lower voltage level is called a low-voltage direct current bus; the high-low voltage direct current buses are interconnected through a direct current transformer, so that voltage grade conversion and isolation between high-low voltage direct currents are realized;
the distributed control method of the multi-voltage-level direct-current distribution network comprises two modes of distributed control and master-slave control;
(1) under the distributed control mode, the operation control strategy of each device in the direct current distribution network is as follows:
(1.1) the control mode of the direct current transformer is constant voltage transformation ratio control, so that constant voltage ratio control between high voltage direct current and low voltage direct current is realized, and the constant voltage transformation ratio of the direct current transformer is the ratio of rated values of interconnected high-low voltage direct current buses;
(1.2) the distributed power supplies, the loads and the energy storage equipment on the two sides of the direct current transformer work in a droop control mode, so that the load fluctuation stabilization and the power balance of a high-voltage direct current bus and a low-voltage direct current bus are realized; the distributed power supplies on the two sides realize integral interaction through constant voltage gain control of the direct current transformer;
(1.3) when the voltage of one side of the direct current transformer is converted due to constant voltage gain control of the direct current transformer, the voltage of the other side is correspondingly changed; at the moment, the distributed power supplies or the energy storage devices on the two sides realize the balance control of power through droop control, and the change of the load on the side or the other side or the output conversion of the distributed power supplies is restrained;
(2) when constant control of direct-current voltage needs to be achieved, the whole direct-current distribution network is switched to a master-slave control mode, and the operation control strategy of each device in the direct-current distribution network in the master-slave control mode is as follows:
(2.1) the control mode of the direct current transformer in the direct current distribution network still keeps constant voltage transformation ratio control;
(2.2) taking a certain distributed power supply or energy storage equipment on one side of the high-voltage direct-current bus or the low-voltage direct-current bus as a main power supply, enabling the distributed power supply or energy storage equipment to work in a voltage control mode, and being used for realizing rated voltage control and stabilizing direct-current voltage on the side; the direct current voltage at the other side is also a rated constant value due to the constant voltage transformation ratio control function of the direct current transformer;
(2.3) simultaneously, operating other distributed power supplies in a maximum power tracking mode, a PQ mode or a droop control mode;
(2.4) the energy storage device not acting as a main power source operates in the PQ mode or the droop mode.
In the invention, in the multi-voltage-level direct-current distribution network, the voltage level of each direct-current bus is 10 kV-48V.
Compared with the prior art, the invention has the beneficial effects that:
when the distributed power supply or load conversion and the distributed power supply are used in a plug-and-play mode, energy in the whole direct current distribution network area can flow seamlessly without switching a control mode through droop control of more distributed power supplies and constant transformation ratio control of a direct current transformer between high voltage and low voltage. In addition, when the high-voltage direct-current distribution network works in a master-slave control mode, the voltage of the whole distribution network area can be constant only by one voltage support source on one side, the control mode of a direct-current transformer does not need to be changed when the power in the whole high-voltage direct-current distribution network area flows and the control mode is changed, and the integrated control of a multi-voltage-level or multi-region direct-current distribution network is realized. Therefore, under various working conditions and control modes of the direct-current distribution network, the control mode of the direct-current transformer does not need to be changed, and the control difficulty of the direct-current distribution network is greatly reduced.
Drawings
Fig. 1 is a schematic diagram of a main flow distribution network;
FIG. 2 is an internal structure diagram of an isolated constant voltage gain DC/DC transformer;
fig. 3 is a control block diagram of a control method of a constant voltage gain dc transformer.
The reference numerals in fig. 1 are: 1, a distributed power supply; 2, loading; 3, an energy storage device; 4, a distributed power supply; 5, loading; 6, energy storage equipment; 7 a direct current transformer; 8 high voltage dc bus; 9 low voltage dc bus.
Detailed Description
The following description will take a dc distribution network with two voltage levels as an example. Other similar structures and methods are within the scope of the present invention in accordance with the principles of the present invention.
As shown in fig. 1, the multi-voltage-class dc distribution network includes two (or more) dc buses with different voltage classes, and the voltage class of each dc bus is between 10kV and 48V. In two direct current buses of adjacent voltage levels, a direct current bus with higher voltage is called a high-voltage direct current bus 8, a direct current bus with lower voltage level is called a low-voltage direct current bus 9, and the two direct current buses are interconnected through a direct current transformer 7 to realize voltage level conversion and isolation between high-voltage direct current and low-voltage direct current. A large number of distributed power supplies 1 matched with the operating voltage, energy storage equipment 3 and various high-voltage loads 2 can be connected to the high-voltage direct-current bus 8. A large number of low-voltage distributed power supplies 4 matched with the operating voltage, energy storage equipment 6, low-voltage loads 5 and the like can also be connected to the low-voltage direct-current bus 9. The direct current distribution network is not limited to two voltage levels, a plurality of voltage levels can be arranged according to needs, and adjacent voltage levels are interconnected through the direct current transformer 7.
Fig. 2 is a schematic diagram of an internal structure of a typical isolated power electronic dc transformer 7, in which the high-voltage side is isolated by a middle high-frequency transformer. The method for controlling the constant voltage of the dc transformer 7 is shown in fig. 3, and realizes the function simulation of the ac transformer by controlling the ratio of the high-voltage side voltage to the low-voltage side voltage to be constant. Therefore, under various working conditions and control modes of the direct-current distribution network, the control mode of the direct-current transformer 7 does not need to be changed, and the control difficulty of the direct-current distribution network is greatly reduced.
The operation control method of the direct current distribution network based on the interconnection of the direct current transformers 7 comprises a distributed control mode and a master-slave control mode.
1. In the distributed control mode, the operation control strategy of each main device in the whole direct current distribution network is as follows:
(1.1) the control mode of the direct current transformer 7 in the direct current distribution network is constant voltage ratio control (or called constant voltage gain control mode), constant voltage control between high-voltage direct current and low-voltage direct current is realized, and the control mode of the direct current transformer based on power electronics does not need to be changed under any condition. The seamless connection of the high-voltage direct-current bus and the low-voltage direct-current bus is realized through the constant-voltage gain controlled direct-current transformer, and the bidirectional flow of the energy at the high-voltage side and the low-voltage side can be realized. Mutual support between high pressure and low pressure can be realized.
(1.2) the constant voltage transformation ratio or constant voltage gain of the dc transformer is the ratio of the ratings of the interconnected high and low voltage dc buses, e.g. if the high voltage dc bus is 800V and the low voltage dc bus is 400V in this example, the constant voltage transformation ratio or voltage gain is 800: 400-2.
(1.3) the distributed power supplies 1 and 4 on the high-voltage direct-current bus 8 and the low-voltage direct-current bus 9 work in a droop control mode, so that the load fluctuation stabilization and the power balance of the high-voltage direct-current bus and the low-voltage direct-current bus can be realized. The distributed power supplies 1, 4 on the high and low voltage dc buses achieve overall interaction through constant voltage gain control of the dc transformer 7.
(1.4) the energy storage devices 3 and 6 on the high-voltage low-voltage direct-current bus also work in a droop control mode, and the whole interaction is realized through the constant-voltage gain control of the direct-current transformer 7.
(1.5) due to the constant voltage proportion control of the direct current transformer 7, when the voltage of one side is converted, the voltage of the other side is correspondingly changed, so that the distributed power supplies 1 and 4 or the energy storage equipment 3 and 6 on the two sides can realize the balance control of power through droop control, and the change of the loads 2 and 5 on the side or the other side or the conversion of the output of the distributed power supplies 1 and 4 is inhibited.
2. When constant control of direct-current voltage needs to be achieved, the whole distribution network can be switched to a master-slave control mode. In the master-slave control mode, the control strategy of each main device under the direct current distribution network is as follows:
(2.1) the control mode of the direct current transformer 7 in the direct current distribution network is still constant voltage ratio control (or is called as a constant voltage gain control mode), constant voltage control between high-voltage direct current and low-voltage direct current is realized, and the control mode of the direct current transformer 7 does not need to be changed under any condition. The seamless connection of the high-low voltage direct current bus is realized through the constant voltage gain controlled direct current transformer 7, and the bidirectional flow of the energy at the high-low voltage side can be realized.
(2.2) any one of the distributed power supplies 1 and 4 or the energy storage devices 3 and 6 on one side can be used as a main power supply, so that the distributed power supplies work in a voltage control mode, rated voltage control is realized, the direct-current voltage on the side is stabilized, and the direct-current voltage on the other side is also rated and constant due to constant voltage transformation ratio control of the direct-current transformer. If the energy storage device 3 is selected as a main power supply and operated in the voltage control mode as in the present example, the high-voltage side direct current is constant, so that the high-voltage side direct current bus is stabilized at 800V, and since the direct current transformer 7 is operated in the constant voltage ratio control mode, the low-voltage side direct current voltage is also a constant rated value and is stabilized at 400V.
(2.3) the distributed power supplies 1, 4 may now operate in either maximum power tracking mode or PQ mode, or droop control mode. In the embodiment, the distributed power supplies 1 and 4 work in a maximum power tracking mode, and renewable energy sources are utilized to the maximum.
(2.4) the energy storage device 6, which is not the main power source, can operate in either the PQ mode or the droop mode, in this case the energy storage device 6 is selected to operate in the droop mode.
Claims (1)
1. A multi-voltage-level direct-current distribution network control method accessed to a distributed power supply is characterized in that the multi-voltage-level direct-current distribution network comprises more than two direct-current buses with different voltage levels, and the distributed power supply, the load and the energy storage equipment which are matched with respective operating voltages are respectively accessed; in two direct current buses of adjacent voltage levels, a direct current bus with higher voltage is called a high-voltage direct current bus, and a direct current bus with lower voltage level is called a low-voltage direct current bus; the high-low voltage direct current buses are interconnected through a direct current transformer, so that voltage grade conversion and isolation between high-low voltage direct currents are realized;
the control method of the multi-voltage-level direct-current distribution network comprises two modes of distributed control and master-slave control;
(1) under the distributed control mode, the operation control strategy of each device in the direct current distribution network is as follows:
(1.1) the control mode of the direct current transformer is constant voltage transformation ratio control, so that constant voltage ratio control between high voltage direct current and low voltage direct current is realized, and the constant voltage transformation ratio of the direct current transformer is the ratio of rated values of interconnected high-low voltage direct current buses;
(1.2) the distributed power supplies, the loads and the energy storage equipment on the two sides of the direct current transformer work in a droop control mode, so that the load fluctuation stabilization and the power balance of a high-voltage direct current bus and a low-voltage direct current bus are realized; the distributed power supplies on the two sides realize integral interaction through constant voltage gain control of the direct current transformer;
(1.3) when the voltage of one side of the direct current transformer is converted due to constant voltage gain control of the direct current transformer, the voltage of the other side is correspondingly changed; at the moment, the distributed power supplies or the energy storage devices on the two sides realize the balance control of power through droop control, and the change of the load on the side or the other side or the output conversion of the distributed power supplies is restrained;
(2) when constant control of direct-current voltage needs to be achieved, the whole direct-current distribution network is switched to a master-slave control mode, and the operation control strategy of each device in the direct-current distribution network in the master-slave control mode is as follows:
(2.1) the control mode of the direct current transformer in the direct current distribution network still keeps constant voltage transformation ratio control;
(2.2) taking a certain distributed power supply or energy storage equipment on one side of the high-voltage direct-current bus or the low-voltage direct-current bus as a main power supply, enabling the distributed power supply or energy storage equipment to work in a voltage control mode, and being used for realizing rated voltage control and stabilizing direct-current voltage on the side; the direct current voltage at the other side is also a rated constant value due to the constant voltage transformation ratio control function of the direct current transformer;
(2.3) simultaneously, operating other distributed power supplies in a maximum power tracking mode, a PQ mode or a droop control mode;
(2.4) the energy storage device not serving as a main power source operates in a PQ mode or a droop mode;
in the multi-voltage-level direct-current distribution network, the voltage level of each direct-current bus is 10 kV-48V.
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| US7116014B1 (en) * | 2002-01-19 | 2006-10-03 | Edward Herbert | Method and apparatus for stabilizing “DC-DC Transformers” in a distributed power system using remote sense |
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| US7116014B1 (en) * | 2002-01-19 | 2006-10-03 | Edward Herbert | Method and apparatus for stabilizing “DC-DC Transformers” in a distributed power system using remote sense |
| CN101931238A (en) * | 2010-04-29 | 2010-12-29 | 浙江省电力试验研究院 | Master-slave strategy-based microgrid system coordination control method |
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