Direct-current mutual-aid power distribution and utilization device and control method

Abstract

The invention provides a direct-current mutual-aid power distribution and utilization device and a control method, and belongs to the technical field of direct-current power transmission. The device comprises at least two direct-current high-voltage buses which are sequentially connected in series through an opening and closing mechanism, at least one direct-current high-voltage bus is connected with a direct-current power generation mechanism through a DC / DC converter, at least one direct-current high-voltage bus is connected with an energy storage and power supply mechanism through a DC / DC converter, at least one direct-current high-voltage bus is connected with an alternating-current power generation mechanism through an AC / DC converter, and at least one alternating-current power generation mechanism is connected with a any direct-current high-voltage bus is connected with a direct-current electric load; and the at least two alternating current buses are independently arranged, each alternating current bus is connected to a corresponding direct current high-voltage bus through a corresponding AC / DC converter, and each alternating current bus is connected to an alternating current power grid through a corresponding transformer. The system is simple in structure, can meet the power supply requirements in different states, and provides a structural basis for automatic adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current power transmission, and in particular to a direct current mutual aid power distribution device and a control method for the direct current mutual aid power distribution device. Background Art

[0002] With the development of new energy sources such as photovoltaic and wind power, their proportion in power distribution network is gradually increasing. However, these new energy technologies are generally intermittent and volatile, which requires the power grid to have better response and regulation capabilities. DC power systems have higher response and regulation capabilities than AC power systems, and have gradually developed into a key way to achieve large-scale distributed access to new energy sources in the future.

[0003] At present, there are still the following major problems in building a DC power distribution system: (1) The DC system needs to be connected to a variety of photovoltaic power generation systems such as roof photovoltaics, photovoltaic floor tiles, photovoltaic curtain walls, distributed wind turbines, different energy storage systems such as lithium iron phosphate and all-vanadium liquid flow, and different types of DC loads such as DC air conditioners, DC charging piles, and DC lighting. The system structure is complex; (2) In a power supply system with multiple distribution transformers, due to the existence of electromagnetic ring network problems, the AC low-voltage side bus cannot be operated together during normal operation, that is, the low-voltage side cannot be connected together, which has limitations in use. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a DC mutual aid power distribution device and a control method to solve the problems of complex system structure and usage limitations existing in the above-mentioned DC system.

[0005] In order to achieve the above object, an embodiment of the present invention provides a DC mutual aid power distribution device, the device comprising: At least two DC high-voltage busbars are connected in series in sequence through a switch mechanism, at least one DC high-voltage busbar is connected to a DC power generation mechanism through a DC / DC converter, at least one DC high-voltage busbar is connected to an energy storage power supply mechanism through a DC / DC converter, at least one DC high-voltage busbar is connected to an AC power generation mechanism through an AC / DC converter, and any DC high-voltage busbar is connected to a DC power load; At least two independently arranged AC busbars, each AC busbar is connected to a corresponding DC high-voltage busbar through a corresponding AC / DC converter, and each AC busbar is connected to an AC grid through a corresponding transformer.

[0006] Optionally, the DC power generation mechanism includes a photovoltaic power generation mechanism.

[0007] Optionally, the AC power generation mechanism includes a wind power generation mechanism.

[0008] Optionally, each AC bus is connected to an AC power load respectively.

[0009] Optionally, the energy storage and power supply mechanism is a battery pack.

[0010] Optionally, the opening and closing mechanism includes at least one of a relay, a mechanical switch, a power electronic switch or a knife switch.

[0011] Optionally, the device further comprises: The control mechanism is connected to the AC / DC converter and the transformer, and is used to control the operation of the AC / DC converter based on the received external control instructions.

[0012] On the other hand, an embodiment of the present invention further provides a control method for a DC mutual aid power distribution device, which is applied to the above-mentioned DC mutual aid power distribution device, wherein one AC / DC converter is in a voltage stabilization mode and the other AC / DC converters are in a power mode; the method comprises: Confirm that the transformer power balance mode control command has been received: Acquire a first active power of a transformer connected to an AC / DC converter in a voltage stabilization mode, a second active power currently output by any AC / DC converter in a power mode, and a third active power of a transformer connected to the AC / DC converter; Determining a first theoretical output power based on the first active power, the second active power and the third active power; Based on the first theoretical output power, adjusting the output power of the AC / DC converter in the power mode; Confirm that the AC / DC converter power balance mode control command has been received: Acquire a fourth active power currently output by the AC / DC converter in the voltage stabilization mode and a fifth active power currently output by any AC / DC converter in the power mode; Determining a second theoretical output power based on the fourth active power and the fifth active power; Based on the second theoretical output power, the output power of the AC / DC converter in the power mode is adjusted.

[0013] Optionally, determining a first theoretical output power based on the first active power, the second active power, and the third active power includes: The first theoretical output power is calculated using the following formula: ; in, is the first theoretical output power; is the first active power; is the second active power; is the third active power.

[0014] Optionally, determining a second theoretical output power based on the fourth active power and the fifth active power includes: The second theoretical output power is calculated using the following formula: ; in, is the second theoretical output power; is the fourth active power; The fifth active power The system structure of this technical solution is simple and easy to use. It can cope with power supply needs under different conditions and provide a structural basis for the automatic operation and regulation of the distribution network.

[0015] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings: Figure 1 It is a structural schematic diagram of the DC mutual aid power distribution device provided by the present invention; Figure 2 It is a structural schematic diagram of a DC mutual aid power distribution device provided by the present invention and provided with two DC high voltage busbars; Figure 3 It is a structural schematic diagram of a DC mutual aid power distribution device provided by the present invention and provided with three DC high voltage busbars; Figure 4 It is a flow chart of the control method of the DC mutual aid power distribution device provided by the present invention.

[0017] Description of Reference Numerals 1-DC high voltage busbar; 2-opening and closing mechanism; 3-DC power generation mechanism; 4-energy storage and power supply mechanism; 5-AC power generation mechanism; 6-DC power load; 7-AC bus; 8-AC power grid; 9-control mechanism; 11-DC / DC converter; 12-AC / DC converter; 13-AC / DC converter; 14- Transformer; 71- AC power load. DETAILED DESCRIPTION

[0018] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0019] In the embodiments of the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to the directions or positional relationships shown in the accompanying drawings, or the directions or positional relationships in which the inventive product is usually placed when in use.

[0020] The terms “first”, “second”, “third”, etc. are only used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0021] The terms "parallel", "vertical", etc. do not mean that the components must be absolutely parallel or vertical, but can be slightly tilted. For example, "parallel" only means that its direction is more parallel than "vertical", and does not mean that the structure must be completely parallel, but can be slightly tilted.

[0022] The terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal, vertical or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In addition, the terms "roughly" and "basically" are intended to explain that the relevant content does not require absolute precision, but can have certain deviations. For example, "roughly equal" does not only mean absolute equality. Since it is difficult to achieve absolute "equality" in actual production and operation, there are generally certain deviations. Therefore, in addition to absolute equality, "roughly equal" also includes the above-mentioned situation with certain deviations. Taking this as an example, in other cases, unless otherwise specified, the terms "roughly" and "basically" have similar meanings to the above.

[0024] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] Figure 1 It is a structural schematic diagram of the DC mutual aid power distribution device provided by the present invention; Figure 2 It is a structural schematic diagram of a DC mutual aid power distribution device provided by the present invention and provided with two DC high voltage busbars; Figure 3It is a structural schematic diagram of a DC mutual aid power distribution device provided by the present invention and provided with three DC high voltage busbars; Figure 4 It is a flow chart of the control method of the DC mutual aid power distribution device provided by the present invention.

[0026] like Figure 1-3 As shown, this embodiment provides a DC mutual aid power distribution device, the device comprising: At least two DC high-voltage busbars 1 are connected in series in sequence through a switch mechanism 2, at least one DC high-voltage busbar 1 is connected to a DC power generation mechanism 3 through a DC / DC converter 11, at least one DC high-voltage busbar 1 is connected to an energy storage power supply mechanism 4 through a DC / DC converter 11, at least one DC high-voltage busbar 1 is connected to an AC power generation mechanism 5 through an AC / DC converter 12, and any DC high-voltage busbar 1 is connected to a DC power load 6; At least two independently arranged AC busbars 7, each AC busbar 7 is connected to a corresponding DC high-voltage busbar 1 through a corresponding AC / DC converter 13, and each AC busbar 7 is connected to the AC grid 8 through a corresponding transformer 14.

[0027] Specifically, in this embodiment, the DC / DC converter 11 is used to adjust the DC voltage to adjust the DC voltage value at the input end that is higher or lower than the set value to a preset value, and the AC / DC converter 13 is used to adjust the AC voltage value that is higher or lower than the set value to a preset value; the opening and closing mechanism 2 can be used as a DC mutual aid switch to achieve the connection and disconnection of two adjacent DC high-voltage busbars 1. Through the above connection structure, it is possible to supply power to the DC power load through AC and DC. More specifically, since the maximum transformation ratio of the DC / DC converter 11 is about 4, for equipment with a large voltage difference, a multi-stage DC / DC converter 11 can be set, and a multi-stage transformation method can be adopted to make the voltage value meet the use requirements.

[0028] Furthermore, the DC power generation mechanism 3 includes a photovoltaic power generation mechanism.

[0029] Specifically, photovoltaic power generation mechanisms may include roof photovoltaics, curtain wall photovoltaics, photovoltaic floor tiles, etc. The component parameters are different, the string configurations are different, and the export voltage requirements are also different. Therefore, the DC / DC converter 11 can be set to multi-stage and configured and connected according to the actual needs of the photovoltaic power generation string to adjust the voltage value to meet the DC power load.

[0030] Furthermore, the AC power generation mechanism 5 includes a wind power generation mechanism.

[0031] Specifically, the wind power generation mechanism may adopt a distributed wind power generation mechanism.

[0032] Furthermore, each AC busbar 7 is connected to an AC power load 71 .

[0033] Specifically, in this embodiment, in addition to supplying power to the DC high-voltage bus 1 through the AC bus 7 and the transformer 14, and then converting the AC power into DC power through the AC / DC converter 13 to supply power to the DC power load, the AC power grid 8 can also directly supply power to the AC power load 71 through the AC bus 7; since the AC busbars 7 are independently arranged, each AC bus 7 is connected to an AC power load 71 for AC power supply.

[0034] Furthermore, the energy storage and power supply mechanism 4 is a battery pack.

[0035] Specifically, the battery pack may use lithium iron phosphate, all-vanadium liquid flow and other batteries.

[0036] Furthermore, the opening and closing mechanism 2 includes: at least one of a relay, a mechanical switch, a power electronic switch or a knife switch.

[0037] Specifically, in this embodiment, the opening and closing mechanism 2 realizes the disconnection and conduction between two adjacent DC high-voltage busbars 1 by adjusting its own opening and closing state, thereby realizing the DC mutual assistance function. The opening and closing mechanism 2 can be set as a relay to realize remote opening and closing control. In addition, the opening and closing mechanism 2 can also be set as at least one of a mechanical switch, a power electronic switch or a knife switch, and the on-off control is realized by manual opening and closing.

[0038] Furthermore, the device also includes: The control mechanism 9 is connected to the AC / DC converter 13 and the transformer 14, and is used to control the operation of the AC / DC converter 13 based on the received external control instructions.

[0039] Specifically, the control mechanism 9 can implement corresponding automatic control based on the device structure when receiving external control instructions to adjust the DC and AC power supply capabilities.

[0040] In a specific embodiment, Figure 2As shown, two DC high-voltage busbars 1 (a first DC high-voltage busbar and a second DC high-voltage busbar) are provided, which are connected in series in sequence through a switch mechanism 2. The first DC high-voltage busbar is connected to the roof photovoltaic through a DC / DC converter 11. The first DC high-voltage busbar is also connected to other types of photovoltaic components except the roof photovoltaic through a DC / DC converter 11. The second DC high-voltage busbar is connected to an energy storage power supply mechanism 4 and other types of DC power generation equipment through a DC / DC converter 11. Since the power generation parameters of the energy storage power supply mechanism 4 and other types of DC power generation equipment are different, the energy storage power supply mechanism 4 and other types of DC power generation equipment are first connected to the DC low-voltage busbar through a first-level DC / DC converter, and then the DC low-voltage busbar is connected to the second DC high-voltage busbar through a second-level DC / DC converter. The first DC high-voltage busbar is connected to a DC power load 6; Two independently arranged AC busbars 7 (a first AC busbar and a second AC busbar), the first AC busbar is connected to the first DC high-voltage busbar via an AC / DC converter 13, the second AC busbar is connected to the second DC high-voltage busbar via an AC / DC converter 13, the first AC busbar and the second AC busbar are connected to the AC grid 8 via a transformer 14 respectively; the first AC busbar and the second AC busbar are respectively connected to an AC power load.

[0041] In a specific embodiment, Figure 3 As shown, three DC high-voltage busbars 1 (a first DC high-voltage busbar, a second DC high-voltage busbar and a third DC high-voltage busbar) are provided, the first DC high-voltage busbar and the second DC high-voltage busbar, the second DC high-voltage busbar and the third DC high-voltage busbar are sequentially connected in series through a switch mechanism 2, the first DC high-voltage busbar is connected to a DC power generation mechanism 3 through a DC / DC converter 11, the second DC high-voltage busbar is connected to an energy storage power supply mechanism 4 through a DC / DC converter 11, the second DC high-voltage busbar is connected to an AC power generation mechanism 5 through a DC / DC converter 11, and the first DC high-voltage busbar is connected to a DC power load 6; Three independently arranged AC busbars 7 (a first AC busbar, a second AC busbar and a third AC busbar), the first AC busbar is connected to the first DC high-voltage busbar via an AC / DC converter 13, the second AC busbar is connected to the second DC high-voltage busbar via an AC / DC converter 13, the third AC busbar is connected to the third DC high-voltage busbar via an AC / DC converter 13, the first AC busbar, the second AC busbar and the third AC busbar are connected to the AC grid 8 via a transformer 14 respectively; the first AC busbar, the second AC busbar and the third AC busbar are respectively connected to AC power loads.

[0042] like Figure 4As shown, the embodiment of the present invention also provides a control method for a DC mutual aid power distribution device, which is applied to the above-mentioned DC mutual aid power distribution device, where one and only one AC / DC converter is in a voltage stabilization mode, and the other AC / DC converters are in a power mode, wherein the voltage stabilization mode means that the function of the AC / DC conversion link is to stabilize the voltage of the DC bus connected thereto at a certain constant voltage value. The power mode means that the function of the AC / DC conversion link is to stabilize the power of the DC bus connected thereto at a certain constant power value; the method comprises: In the first control mode: First, confirm that the transformer power balance mode control instruction is received: Secondly, obtaining a first active power of a transformer connected to the AC / DC converter in the voltage stabilization mode, a second active power currently output by any AC / DC converter in the power mode, and a third active power of a transformer connected to the AC / DC converter; Then, determining a first theoretical output power based on the first active power, the second active power and the third active power; Finally, based on the first theoretical output power, the output power of the AC / DC converter in the power mode is adjusted; By adopting the above control method, load balancing between transformers can be achieved, so that the power supply capacity of the AC power supply system is maximized.

[0043] In the second control mode: First, confirm that the AC / DC converter power balance mode control command is received: Secondly, obtaining a fourth active power currently output by the AC / DC converter in the voltage stabilization mode and a fifth active power currently output by any AC / DC converter in the power mode; Then, determining a second theoretical output power based on the fourth active power and the fifth active power; Finally, based on the second theoretical output power, the output power of the AC / DC converter in the power mode is adjusted.

[0044] By adopting the above control method, load balancing between AC / DC converters can be achieved, so that the power supply capacity of the DC power supply is maximized.

[0045] Further, in this implementation, determining a first theoretical output power based on the first active power, the second active power, and the third active power includes: The first theoretical output power is calculated using the following formula: ; in, is the first theoretical output power; is the first active power; is the second active power; is the third active power.

[0046] Specifically, the above calculation formula is used to calculate the first theoretical output power, and then the calculated first theoretical output power is used to adjust the output power of the AC / DC converter in the power mode. The calculation method is simple and the calculation result is accurate.

[0047] Further, in this implementation manner, determining the second theoretical output power based on the fourth active power and the fifth active power includes: The second theoretical output power is calculated using the following formula: ; in, is the second theoretical output power; is the fourth active power; is the fifth active power.

[0048] Specifically, the second theoretical output power is calculated using the above calculation formula, and then the calculated second theoretical output power is used to adjust the output power of the AC / DC converter in the power mode. The calculation method is simple and the calculation result is accurate.

[0049] More specifically, when the control is performed based on the above device, the random power flow algorithm can be used to process the data to realize automatic control to cope with the power supply demand under different states. The random power flow algorithm specifically includes: the index set is T = {1, 2, 3, ...}; the state space is S = {1, 2, 3, 4, 5, 6}; if the sequence {3, 2, 3, 4, 6, 5, 1, 3, ...} is called It indicates that the 1st, 3rd, and 8th throws are "3", the 2nd throw is "2", the 4th throw is "4", the 5th throw is "6", .... And at this time The mean is E =3.5, the variance is D( )=17.5,n=1,2,…,covariance is Cov( , )=0,i≠j.

[0050] Definition 1 Let (Ω, F, P) be a probability space, a family of random variables is called a random process, where T is called the index set, for each t in T, X(t) is a random variable X(t, ω), and for each fixed ω, is a real-valued function defined on T with the same value range as X(t), which is called a (sample) trajectory of the random process X.

[0051] For all fixed t, all possible values ​​of X(t) are called the state space of X. For the random process of discrete random variables, the state space can be considered as a set of positive integers, because any countable set has a one-to-one correspondence with a set of positive integers. All we need to do is number all the states and use their numbers to represent the states.

[0052] We often interpret t as time. Generally speaking, T is an infinite set. If it is a countable set, such as T = {0, 1, 2, ...}, then X is called a random process with discrete parameters, or a random sequence. When T = [0, +∞) or (-∞, +∞), then X is called a random process with continuous parameters.

[0053] The above describes in detail the optional implementation modes of the embodiments of the present invention in combination with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical scheme of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0054] Those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor (processor) perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0055] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner when there is no contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations. In addition, various implementation modes of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed by the embodiments of the present invention.

Claims

1. A DC mutual aid power distribution device, characterized in that: The device comprises: At least two DC high-voltage busbars (1) are connected in series in sequence via a switch mechanism (2); at least one DC high-voltage busbar (1) is connected to a DC power generation mechanism (3) via a DC / DC converter (11); at least one DC high-voltage busbar (1) is connected to an energy storage power supply mechanism (4) via a DC / DC converter (11); at least one DC high-voltage busbar (1) is connected to an AC power generation mechanism (5) via an AC / DC converter (12); and any one DC high-voltage busbar (1) is connected to a DC power load (6); At least two independently arranged AC busbars (7), each AC busbar (7) is connected to a corresponding DC high-voltage busbar (1) via a corresponding AC / DC converter (13), and each AC busbar (7) is connected to an AC power grid (8) via a corresponding transformer (14).

2. The DC mutual aid power distribution device according to claim 1, characterized in that: The DC power generation mechanism (3) comprises a photovoltaic power generation mechanism.

3. The DC mutual aid power distribution device according to claim 1, characterized in that: The AC power generation mechanism (5) comprises a wind power generation mechanism.

4. The DC mutual aid power distribution device according to claim 1, characterized in that: Each AC busbar (7) is respectively connected to an AC power load (71).

5. The DC mutual aid power distribution device according to claim 1, characterized in that: The energy storage and power supply mechanism (4) is a battery pack.

6. The DC mutual aid power distribution device according to claim 1, characterized in that: The opening and closing mechanism (2) comprises: at least one of a relay, a mechanical switch, a power electronic switch or a knife switch.

7. The DC mutual aid power distribution device according to claim 1, characterized in that: The device also includes: A control mechanism (9) is connected to the AC / DC converter (13) and the transformer (14) and is used to control the operation of the AC / DC converter (13) based on a received external control instruction.

8. A control method for a DC mutual aid power distribution device, applied to the DC mutual aid power distribution device according to any one of claims 1 to 7, characterized in that: One of the AC / DC converters is in a voltage regulation mode, and the other AC / DC converters are in a power mode; the method comprises: Confirm that the transformer power balance mode control command has been received: Acquire a first active power of a transformer connected to an AC / DC converter in a voltage stabilization mode, a second active power currently output by any AC / DC converter in a power mode, and a third active power of a transformer connected to the AC / DC converter; Determining a first theoretical output power based on the first active power, the second active power and the third active power; Based on the first theoretical output power, adjusting the output power of the AC / DC converter in the power mode; Confirm that the AC / DC converter power balance mode control command has been received: Acquire a fourth active power currently output by the AC / DC converter in the voltage stabilization mode and a fifth active power currently output by any AC / DC converter in the power mode; Determining a second theoretical output power based on the fourth active power and the fifth active power; Based on the second theoretical output power, the output power of the AC / DC converter in the power mode is adjusted.

9. The control method of the DC mutual aid power distribution device according to claim 8, characterized in that: Determining a first theoretical output power based on the first active power, the second active power, and the third active power includes: The first theoretical output power is calculated using the following formula: ； in, is the first theoretical output power; is the first active power; is the second active power; is the third active power.

10. The control method of the DC mutual aid power distribution device according to claim 8, characterized in that: Determining a second theoretical output power based on the fourth active power and the fifth active power includes: The second theoretical output power is calculated using the following formula: ； in, is the second theoretical output power; is the fourth active power; is the fifth active power.

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