CN114928093A - Topological structure of direct current power flow controller and control method - Google Patents

Topological structure of direct current power flow controller and control method Download PDF

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Publication number
CN114928093A
CN114928093A CN202210838620.7A CN202210838620A CN114928093A CN 114928093 A CN114928093 A CN 114928093A CN 202210838620 A CN202210838620 A CN 202210838620A CN 114928093 A CN114928093 A CN 114928093A
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China
Prior art keywords
current
direct current
power flow
flow controller
switching device
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CN202210838620.7A
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Chinese (zh)
Inventor
武文
邹祖冰
李伟
刘瑞阔
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China Three Gorges Corp
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China Three Gorges Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J1/102—Parallel operation of dc sources being switching converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention relates to the technical field of direct current transmission and discloses a topological structure of a direct current power flow controller and a control method. Wherein, this topological structure includes: the voltage stabilizing unit comprises an alternating current transformer and an inverter, wherein the alternating current transformer comprises an input end and an output end, the input end of the alternating current transformer is connected to an alternating current bus of a power transmission system, and the output end of the alternating current transformer is connected to the inverter; the regulating unit comprises a plurality of regulating valves connected in parallel, and the output end of each regulating valve is connected to each direct current transmission line of the power transmission system; and the direct current capacitor is arranged between the voltage stabilizing unit and the adjusting unit and is used for providing a stable direct current voltage source for the adjusting unit. By implementing the method and the device, the overvoltage problem of the direct current capacitor is avoided, the reliability of the power flow controller is improved, the independent control of the direct current power flows in the plurality of direct current transmission lines is realized, the current coupling problem among the direct current transmission lines is avoided, and the working stability of a power transmission system is further ensured.

Description

Topological structure of direct current power flow controller and control method
Technical Field
The invention relates to the technical field of direct current transmission, in particular to a topological structure of a direct current power flow controller and a control method.
Background
The number of converter stations and transmission lines in the multi-terminal direct current transmission system is relatively large, direct current power flow management on the system is difficult only by means of power coordination control between the converter stations, unnecessary line loss, line overload and the like can be caused, and the safe and stable operation of the whole direct current transmission system is endangered. In order to realize flexible and accurate control of power flow in a direct current transmission line and ensure safe and stable operation of a multi-terminal direct current transmission system, an additional power electronic control device, namely a direct current power flow controller, is arranged in the direct current transmission line system, and the method becomes the most effective and most promising solution at present.
The existing direct current power flow controller usually adopts a topology structure of a shared capacitor structure, an independent capacitor structure or a coupling inductor, but the topology structure can only realize the direct current power flow control of a single power transmission line, and the capacitor voltage is possibly influenced by other components and parts and is not controlled, so that the problem of capacitor overvoltage occurs, and the direct current power flow control of a plurality of power transmission circuits is difficult to realize.
Disclosure of Invention
In view of this, embodiments of the present invention provide a topology structure and a control method of a dc power flow controller, so as to solve a problem that it is difficult for an existing dc power flow controller to implement dc power flow control of multiple power transmission circuits.
According to a first aspect, an embodiment of the present invention provides a topology of a dc power flow controller, including: the voltage stabilizing unit comprises an alternating current transformer and an inverter, wherein the alternating current transformer comprises an input end and an output end, the input end of the alternating current transformer is connected to an alternating current bus of a power transmission system, and the output end of the alternating current transformer is connected to the inverter; the regulating unit comprises a plurality of regulating valves connected in parallel, and the output end of each regulating valve is connected to each direct current transmission line of the power transmission system; and the direct current capacitor is arranged between the voltage stabilizing unit and the adjusting unit and is used for providing a stable direct current voltage source for the adjusting unit.
According to the topological structure of the direct current power flow controller, the alternating current transformer and the inverter are used as the voltage stabilizing unit, so that auxiliary control over the voltage of the intermediate capacitor can be achieved by using fewer components, the overvoltage problem of the direct current capacitor is avoided, and the reliability of the power flow controller is improved. Meanwhile, the regulating unit comprises a plurality of regulating valves connected in parallel, and the output end of each regulating valve is connected to each direct current transmission line of the power transmission system, so that the direct current flow of the corresponding direct current transmission line connected to the regulating valve can be controlled through each regulating valve, the independent control of the direct current flow in the plurality of direct current transmission lines is realized, the problem of current coupling among the direct current transmission lines is avoided, and the working stability of the power transmission system is further ensured.
With reference to the first aspect, in a first embodiment of the first aspect, the inverter is a two-level, three-phase inverter.
According to the topological structure of the direct current power flow controller provided by the embodiment of the invention, the two-level three-phase inverter is connected with the alternating current transformer, so that the voltage input by the alternating current bus is convenient to control, the voltage stabilization control of the voltage of the direct current capacitor is realized, and the voltage introduced into the direct current capacitor is prevented from exceeding the allowed voltage range.
With reference to the first aspect, in a second embodiment of the first aspect, the plurality of regulating valves are identical in structure.
According to the topological structure of the direct current power flow controller provided by the embodiment of the invention, the control of the direct current power flow is facilitated and the subsequent port expansion is facilitated by arranging the plurality of regulating valves with the same structure.
With reference to the second embodiment of the first aspect, in a third embodiment of the first aspect, the regulating valve includes a first switching device and a second switching device, and the first switching device and the second switching device are connected in a half-bridge configuration.
According to the topological structure of the direct current power flow controller provided by the embodiment of the invention, the first switching device and the second switching device in the regulating valve are connected in a half-bridge structure mode, the structure is relatively simple, and the port expansion cost is saved.
With reference to the first aspect, in a fourth implementation form of the first aspect, the input terminal of the alternating current transformer comprises a first terminal, a second terminal, and a third terminal; the first terminal, the second terminal and the third terminal are respectively connected with an A-phase alternating current bus, a B-phase alternating current bus and a C-phase alternating current bus of an alternating current power grid.
According to the topological structure of the direct current power flow controller provided by the embodiment of the invention, the first terminal, the second terminal and the third terminal are led out from the input end of the alternating current transformer and are respectively connected to the A-phase alternating current bus, the B-phase alternating current bus and the C-phase alternating current bus of the alternating current power grid, so that electricity can be conveniently taken from the alternating current bus.
With reference to the fourth embodiment of the first aspect, in a fifth embodiment of the first aspect, an output end of one of the regulating valves in the regulating unit is connected to a convergence point of different dc transmission lines, and output ends of the remaining regulating valves are respectively connected to different dc transmission lines.
According to the topological structure of the direct current power flow controller provided by the embodiment of the invention, the output ends of different regulating valves are respectively connected with different direct current transmission lines, so that each direct current transmission line corresponds to each regulating valve, and the freedom degree of power flow control is improved.
According to a second aspect, an embodiment of the present invention provides a control method for a dc power flow controller, which is applied to the topology of the dc power flow controller described in the first aspect or any implementation manner of the first aspect, where the control method for the dc power flow controller includes: under the condition that the voltage of a direct current capacitor is controlled to be stable through a voltage stabilizing unit of the direct current power flow controller, the direction of current flowing into the direct current power flow controller is obtained; determining a current regulation strategy according to the current direction; and issuing the current regulation strategy to a regulation unit of the direct current power flow controller, wherein the current regulation strategy is used for controlling the connection or disconnection of each regulating valve in the regulation unit so as to regulate the direct current flowing through the power transmission line.
According to the control method of the direct current power flow controller provided by the embodiment of the invention, the current direction flowing into the direct current power flow controller is detected, the current regulation strategy is determined according to the current direction, and then the current regulation strategy is issued to the regulation unit of the direct current power flow controller, so that each regulation valve regulates the current according to the current regulation strategy, the independent control of the direct current power flow of each power transmission direct current transmission line is realized, and the degree of freedom of power flow control is improved.
With reference to the second aspect, in a first embodiment of the second aspect, the determining a current regulation strategy according to the current direction includes: acquiring target lines where convergent points of different direct current transmission lines are located; determining the duty ratio of the first switching device and the second switching device in each regulating valve for conducting or breaking by taking the current direction in the target line as a reference; and generating the current regulation strategy according to the duty ratio.
With reference to the first embodiment of the second aspect, in a second embodiment of the second aspect, the generating the current regulation strategy according to the duty cycle includes: when the current direction is the direction of the current flowing out of the convergent point, determining a first current regulation strategy, wherein the first current regulation strategy comprises a first control instruction and a second control instruction; the first control instruction is used for controlling a first switching device of the regulating valve connected to the convergent point to keep a conducting state, and a second switching device of the regulating valve to keep a closing state; and the second control instruction is used for controlling second switching devices of other regulating valves to be complementarily switched on or switched off according to the first duty ratio.
With reference to the first embodiment of the second aspect, in a third embodiment of the second aspect, the generating the current regulation strategy according to the duty cycle includes: when the current direction is that the current flows into the convergence point, determining a second current regulation strategy, wherein the second current regulation strategy comprises a third control instruction and a fourth control instruction; the third control instruction is used for controlling a first switching device of the regulating valve connected to the convergent point to keep in an off state, and a second switching device of the regulating valve to keep in an on state; and the fourth control instruction is used for controlling the second switching devices of other regulating valves to be complementarily switched on or switched off according to a second duty ratio.
According to the control method of the direct current power flow controller provided by the embodiment of the invention, the target line where the convergence points of different direct current transmission lines are located is obtained, and the current direction in the target line is used as a reference, the on-off duty ratio of the first switching device and the second switching device in each regulating valve is determined, so that the current flowing through the regulating valves is regulated, the freedom degree of power flow control is improved, and the reverse control of the direct current power flow of the direct current transmission lines is realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of a topology of a dc power flow controller according to an embodiment of the invention;
fig. 2 is another schematic diagram of the topology of the dc power flow controller according to an embodiment of the invention;
fig. 3 is a flowchart of a control method of the dc power flow controller according to the embodiment of the invention;
fig. 4 is another flowchart of a control method of the dc power flow controller according to the embodiment of the invention;
fig. 5 is a schematic diagram of a five terminal dc power transmission system of an embodiment of the invention;
fig. 6 is a schematic diagram of a dc power flow controller according to an embodiment of the present invention connected to a five-terminal dc power transmission system;
fig. 7 is a schematic diagram illustrating duty cycle control of each regulating valve in the dc power flow controller according to the embodiment of the present invention;
fig. 8 is a block diagram of a control device of a dc power flow controller according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The existing direct current power flow controller usually adopts a common capacitor structure, an independent capacitor structure or a coupling inductor topological structure, but the topological structure can only realize the direct current power flow control of a single power transmission line, and the capacitor voltage is possibly influenced by other components and parts and is not controlled, so that the problem of capacitor overvoltage occurs, and the direct current power flow control of a plurality of power transmission circuits is difficult to realize.
Based on the technical scheme, the auxiliary control on the voltage of the intermediate capacitor is realized by using fewer components, the overvoltage problem of the direct current capacitor is avoided, and the reliability of the power flow controller is improved. Meanwhile, each regulating valve controls the direct current power flow of the corresponding direct current transmission line to which the regulating valve is connected, so that the independent control of the direct current power flow in a plurality of direct current transmission lines is realized, and the current coupling problem among the direct current transmission lines is avoided.
According to an embodiment of the present invention, there is provided an embodiment of a topology structure of a dc power flow controller, where the topology structure of the dc power flow controller includes: voltage stabilizing unit 10, regulating unit 20 and dc capacitor 30. Specifically, the voltage stabilizing unit 10 obtains power from the ac bus, and establishes a stable capacitor voltage for the dc capacitor 30, so that the dc capacitor 30 can provide a stable dc voltage source for the adjusting unit 20, and then the adjusting unit 20 can adjust the dc power flow of each dc power transmission line according to the current adjusting strategy.
The voltage stabilizing unit 10 is mainly configured to stabilize the voltage of the dc capacitor 30, and mainly includes an ac transformer 101 and an inverter 102, where the ac transformer 101 includes an input end and an output end, the input end of the ac transformer 101 is connected to an ac bus of a power transmission system, and the output end of the ac transformer 101 is connected to the inverter 102.
The adjusting unit 20 is mainly used for adjusting the current flowing through each dc transmission line, and mainly includes a plurality of adjusting valves 201 connected in parallel, and an output end of each adjusting valve 201 is connected to a dc transmission line of a power transmission system.
The dc capacitor 30 is mainly used to provide a stable dc voltage source for the regulating unit, and the dc capacitor 30 is disposed between the voltage stabilizing unit 10 and the regulating unit 20. The capacitance value and the number of the dc capacitors 30 are not limited herein, and can be determined by those skilled in the art according to actual needs.
According to the topology structure of the direct current power flow controller, the alternating current transformer and the inverter are used as the voltage stabilizing unit, so that auxiliary control over the voltage of the intermediate capacitor can be achieved by using fewer components, the overvoltage problem of the direct current capacitor is avoided, and the reliability of the power flow controller is improved. Meanwhile, the regulating unit comprises a plurality of regulating valves connected in parallel, and the output end of each regulating valve is connected to each direct current transmission line of the power transmission system, so that the direct current flow of the corresponding direct current transmission line connected to the regulating valve can be controlled through each regulating valve, the independent control of the direct current flow in the plurality of direct current transmission lines is realized, the problem of current coupling among the direct current transmission lines is avoided, and the working stability of the power transmission system is further ensured.
Alternatively, as shown in fig. 2, the inverter 102 is a two-level three-phase inverter. Each phase of the two-level three-phase inverter is connected with the input end of the alternating current transformer 101, so that the voltage input by the alternating current bus can be controlled conveniently, the voltage stabilization control of the voltage of the direct current capacitor is realized, and the voltage introduced into the direct current capacitor is prevented from exceeding the allowed voltage range.
Alternatively, as shown in FIG. 2, the plurality of regulator valves are identical in construction. Through setting up a plurality of governing valves that the structure is the same, made things convenient for the control of direct current trend, the subsequent port extension of being convenient for simultaneously.
Specifically, the regulator valve HB n The switching device comprises a first switching device and a second switching device, wherein the first switching device and the second switching device are connected in a half-bridge structure.
The first and second switching devices may be fully-controlled power electronic devices, such as one or more of IGBT, IGCT, IEGT, GTO or MOSFET turn-off devices. The first switching device and the second switching device are connected in a half-bridge configuration (fig. 2 shows a half-bridge connection configuration in which the first switching device and the second switching device are both IGBTs, and fig. 2 shows different control valves HB with Da, Sa, Db, Sb, D1a, T1a, D1b, T1b, and the like n The first switch device and the second switch device in (1) to facilitate distinguishing), which facilitates subsequent port expansion, and the structure is relatively simple, thus saving the port expansion cost.
Optionally, as shown in fig. 2, the input terminal of the ac transformer 101 includes a first terminalS 1 A second terminalS 2 And a third terminalS 3 The first terminalS 1 A second terminalS 2 And a third terminalS 3 The alternating current bus is connected with an A alternating current bus, a B alternating current bus and a C alternating current bus of an alternating current power grid respectively. This facilitates the ac transformer 101 to take power from the ac bus.
Optionally, as shown in fig. 2, an output end of one regulating valve in the regulating unit is connected to a convergence point of different dc transmission lines, and output ends of the other regulating valves are respectively connected to different dc transmission lines.
The convergence point is the current convergence position of each direct current transmission line. Specifically, the regulating unit includes n regulating valves, and an output end of one regulating valve is connected to a convergence point of different dc transmission lines (shown in fig. 2 as a first regulating valve HB 0 Terminal T of the output of (a) is connected to the convergence point), and the output of the remaining n-1 regulating valves are connected to different dc transmission lines (shown in fig. 2 as the second regulating valve HB) 1 Terminal P of output end of regulating valve to n-1 1 ~P n Respectively connected with different direct current transmissionElectrical lines) where n is a positive integer. Therefore, the power flow control of all the direct current transmission lines can be realized, the current coupling among different direct current transmission lines can be avoided, and the freedom degree of the power flow control is improved.
According to an embodiment of the present invention, there is provided an embodiment of a control method of a dc power flow controller, where it is to be noted that the steps shown in the flowchart of the drawings may be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that here.
In this embodiment, a control method of a dc power flow controller is provided, which can be used in a topology of the dc power flow controller or a system including the dc power flow controller, and fig. 3 is a flowchart of a control method of a dc power flow controller according to an embodiment of the present invention, and as shown in fig. 3, the flowchart includes the following steps:
and S11, acquiring the current direction flowing into the DC power flow controller under the condition that the voltage of the DC capacitor is controlled to be stable by the voltage stabilizing unit of the DC power flow controller.
After the direct current power flow controller is connected to a direct current power transmission system to operate normally, a two-level three-phase inverter in a voltage stabilizing unit of the direct current power flow controller adopts a fixed direct current voltage operation control strategy so as to enable the voltage Uc of a direct current capacitor to be in a stable state.
The current direction is used for representing the current flowing direction of the direct current power flow controller, and the current direction comprises a positive current direction and a negative current direction. Taking the five-terminal dc transmission system shown in fig. 5 as an example, wherein AC1, AC2, AC3, AC4 and AC5 are all AC grids, line.12, line.14, line.23, line.24, line.34 and line.45 are transmission lines between the AC grids, and the equivalent resistance values of the transmission lines are fixed. Fig. 6 shows a schematic connection diagram of the dc power flow controller connected to the five-terminal dc power transmission system, where a terminal T is an output end of a certain regulating valve and is used as a convergence point of different dc power transmission lines, and a terminal P is used 1 、P 2 And P 3 And are output ends of other regulating valves. If the direction of the current flowing into the terminal T is set to be a positive current direction, the direction of the current flowing out of the terminal T is set to be a negative current direction. Similarly, flows into the terminal P 1 、P 2 And P 3 Is in the positive direction of current, then flows out of terminal P 1 、P 2 And P 3 Is the current negative direction. The dc power flow controller can maintain the dc capacitor voltage at a stable level, and can supply the dc capacitor voltage to the terminal T, P 1 、P 2 And P 3 Is monitored in real time to determine whether current is flowing into terminal T, P 1 、P 2 And P 3 Or out terminal T, P 1 、P 2 And P 3 。
And S12, determining a current regulation strategy according to the current direction.
The current regulation strategy is a control strategy for on-off of the regulating valve. The direct current power flow controller can control the on-off of the regulating valve according to the current direction by a certain duty ratio. The current regulation strategy may be determined according to the current regulation requirement of the dc power flow, such as increasing the current of the dc transmission line or decreasing the current of the dc transmission line.
And S13, sending a current regulation strategy to a regulation unit of the direct current power flow controller.
The current regulation strategy is used for controlling the connection or disconnection of each regulating valve in the regulating unit so as to regulate the direct current flowing through the power transmission line.
And issuing the determined current regulation strategy to a regulation unit, wherein the regulation unit can generate a control instruction according to the current regulation strategy, and the control instruction is used for conducting and shutting down each regulation valve to realize the direct current regulation of each direct current transmission line.
In the control method of the dc power flow controller provided in this embodiment, a current regulation policy is determined according to a current direction by detecting the current direction flowing into the dc power flow controller, and then the current regulation policy is issued to a regulation unit of the dc power flow controller, so that each regulation valve regulates current according to the current regulation policy, thereby implementing independent control of dc power flow of each transmission dc power transmission line, and improving the degree of freedom of power flow control.
In this embodiment, a control method of a dc power flow controller is provided, which can be used in the topology of the dc power flow controller or a system including the dc power flow controller, and fig. 4 is a flowchart of a control method of a dc power flow controller according to an embodiment of the present invention, as shown in fig. 4, where the flowchart includes the following steps:
and S21, acquiring the current direction flowing into the DC power flow controller under the condition that the voltage of the DC capacitor is controlled to be stable by the voltage stabilizing unit of the DC power flow controller. For a detailed description, refer to the corresponding related description of the above embodiments, which is not repeated herein.
And S22, determining a current regulation strategy according to the current direction.
Specifically, the step S22 may include:
and S221, acquiring a target line where the convergent points of different direct current transmission lines are located.
The target line is a reference line of other direct current transmission lines, and the direct current power flow controller can select a convergence point of different direct current transmission lines from the multiple direct current transmission lines and take a line where the convergence point is located as the target line.
And S222, determining the duty ratio of the first switching device and the second switching device in each regulating valve for conducting or breaking by taking the current direction in the target line as a reference.
And the first switching device and the second switching device of the regulating valve connected with the target line are switched on or off at a fixed complementary duty ratio, and then the on or off of the first switching device and the second switching device in the regulating valve is used for determining the on or off duty ratio of the first switching device and the second switching device in each of the rest regulating valves.
And S223, generating a current regulation strategy according to the duty ratio.
And the direct current power flow controller controls the connection or disconnection of the first switch device and the second switch device in each regulating valve according to the duty ratio to complete the current regulation of each direct current transmission line. Specifically, the voltage of the output port of each regulating valve of the direct current power flow controller can be calculated according to the duty ratio, and then the current flowing through the direct current power transmission line can be calculated by combining the resistance of each direct current power transmission line.
Setting the regulating valve connected with the target line as HB 0 The other regulating valves are HB 1 ~HB 3 The first switching device of each regulating valve is HB 0 ~HB 3 The second switching device of each regulating valve is HB 0 ~HB 3 A tube of which the current flowing through the point of convergence isI T . Specifically, the step S223 may include:
(1) when the current direction is the outflow convergence point, a first current regulation strategy is determined.
The first current regulation strategy comprises a first control instruction and a second control instruction; the first control instruction is used for controlling a first switching element of the regulating valve connected to the convergent point to keep a conducting state, and a second switching element of the regulating valve to keep a switching-off state; and the second control instruction is used for controlling the second switching devices of other regulating valves to be complementarily switched on or switched off according to the first duty ratio.
The first duty cycle is used for characterizing the HB i And turning on and off the second switching device. When in useI T When the direction is a negative direction, namely the current direction is an outflow convergent point, the direct current power flow controller controls the HB through the first control command 0 The upper tube of (1) is kept in a conducting state, and the lower tube is kept in a disconnecting state. The direct current power flow controller adjusts the current flowing through each direct current transmission line according to the first current adjustment strategyI iP * And the sampled currentI iP To generate a first duty cycle for each regulator valve, as shown in fig. 7. Then, the dc power flow controller may control the regulating valve HB through a second control instruction i The second switching devices are complementarily turned on or off according to the first duty ratio.
(2) And when the current direction is the inflow convergence point, determining a second current regulation strategy.
The second current regulation strategy comprises a third control instruction and a fourth control instruction; the third control instruction is used for controlling a first switching element of the regulating valve connected to the convergent point to keep an off state, and a second switching element of the regulating valve to keep an on state; and the fourth control instruction is used for controlling the second switching devices of other regulating valves to be complementarily switched on or switched off according to the second duty ratio.
The second duty cycle is used for characterizing HB i And turning on and off the second switching device. When in useI T When the direction is positive direction, namely the current direction is inflow convergence point, at this time, the DC power flow controller controls HB through the third control instruction 0 The upper tube of (1) is kept in an off state, and the lower tube is kept in an on state. The direct current power flow controller adjusts the current flowing through each direct current transmission line according to the second current adjusting strategyI iP * And the sampled currentI iP To generate a second duty cycle for each regulator valve, as shown in fig. 7. Then, the dc power flow controller may control the regulating valve HB through a fourth control instruction i Is complementarily turned on or off according to the second duty ratio.
The determination of the current flow direction and the determination of the current regulation strategy are described in detail herein by taking the example of the dc power flow controller shown in fig. 6 being connected to the dc power transmission system.
(1) If current flows into terminal T, P 1 、P 2 And P 3 When HB is on 0 Upper tube of (1) and opening HB 1 ~HB 3 When the tube is down, the output voltage of each port of the DC power flow controller is V TP1 =Uc，V TP2 =Uc，V TP3 = Uc; when maintaining HB 0 Upper tube of (1) is on, but off HB 1 ~HB 3 When the tube is down, the output voltage state of each port of the DC power flow controller is changed to V TP1 =0，V TP2 =0，V TP3 And = 0. Thus, when flowing into the terminal T, P 1 、P 2 And P 3 When the current direction of the capacitor is the same as the positive direction, if the upper tube and the lower tube of the HB 1-HB 3 are kept in complementary conduction, under the working condition, the HB is maintained 0 By controlling HB 1 ~HB 3 The on and off of the lower tube can respectively obtain V at each output port of the DC power flow controller TP1 =D 1 Uc，V TP2 =D 2 Uc，V TP3 =D 3 Adjustable DC voltage of Uc, by pair D 1 ~D 3 The current control of the direct current transmission line can be realized by the adjustment. Wherein D is 1 ~D 3 Are respectively HB 1 ~HB 3 Duty cycle of the lower tube.
(2) If a current flows into the terminal T, a current flows out of the terminal P 1 、P 2 And P 3 When HB is on 0 And opening HB 1 ~HB 3 When the power is supplied to the direct current power flow controller, the output voltage of each port of the direct current power flow controller is respectively:V TP1 = -U c ，V TP2 = -U c ，V TP3 = -U c (ii) a When maintaining HB 0 Lower tube of (1) turns on and off HB 1 ~HB 3 When the direct current power flow controller is used for switching on the tube, the output voltage state of each port of the direct current power flow controller is changed to beV TP1 =0，V TP2 =0，V TP3 And = 0. Thus, if HB is maintained 1 ~HB 3 The upper and lower tubes are complementarily conducted, and under the working condition, the HB is maintained 0 By controlling HB 1 ~HB 3 The on and off of the lower pipe can be respectively obtained at each port of the DC power flow controllerV TP1 = -(1-D 1 )U c ，V TP2 = -(1-D 2 )U c ，V TP3 = -(1-D 3 )U c Can be regulated by the adjustable DC voltage of the pairD 1 ~D 3 The adjustment of the power flow control device can realize the power flow control of each direct current transmission line.
(3) If current flows into terminals T and P 1 Out of current terminal P 2 And P 3 Maintenance of HB 0 Upper tube on by controlling HB 1 ~HB 3 The on and off of the lower tube can be obtained at each output port of the DC power flow controllerV TP1 =D 1 U c ，V TP2 =D 2 U c ，V TP3 =D 3 U c The adjustable dc voltage of (1). When the direction of the current flowing into the terminal T is positive or the current of other controlled lines is reversed, the working principle of the dc power flow controller is basically similar to that described above, and will not be described herein again.
Therefore, after the direct current power flow controller is connected into the direct current power transmission system, the internal voltage is controlled based on the internal voltageV TP On the basis of stable control, the independent regulating valves are respectively introduced to different controlled direct current transmission lines through control equivalence to realize voltage adjustability, and the voltage-adjustable DC power transmission line has the following characteristics:
(1) when the total current isI T When the direction is negative, no matter the current direction of each controlled direct current transmission line is positive or negative, only HB is ensured 0 Upper tube on by controlling HB 1 ~HB 3 The on and off of the lower tube can ensure that the lower tube is respectively connected in series on the corresponding controlled direct current transmission lineV TP1 =D 1 U c ，V TP2 =D 2 U c ，V TP3 =D 3 U c The adjustable dc voltage of (a);
(2) when the total current isI T The direction is positive, no matter the current direction of each controlled direct current transmission line is positive or negative, only HB is ensured 0 Is conducted through the same HB 1 ~HB 3 The on-off ratio of the lower tube can ensure that the lower tube is respectively connected in series on the corresponding controlled direct current transmission lineV TP1 = -(1-D 1 )U c ，V TP2 = -(1-D 2 )U c ，V TP3 = -(1-D 3 )U c The adjustable dc voltage of (a).
Based on the method, the direct current transmission line is equivalent to a resistor (the resistor is invariable) connected in series to the direct current transmission line, and the duty ratio of the first switching device or the second switching device in each regulating valve is controlled by the direct current power flow controllerD i Is prepared byThe control of the relative direct current voltages at the two ends of each controlled direct current transmission line can be realized, and then the power flow flowing through each direct current transmission line can be determined according to the relation among the voltage, the resistance and the current, so that the power flow regulation of the direct current transmission line is realized.
And S23, sending a current regulation strategy to a regulation unit of the direct current power flow controller.
The current regulation strategy is used for controlling the on/off of each regulating valve in the regulation unit so as to regulate the direct current flowing through the power transmission line.
For detailed description, reference is made to the corresponding related description of the above embodiments, and details are not repeated herein.
In the control method of the dc power flow controller provided in this embodiment, the target line where the convergence points of different dc power transmission lines are located is obtained, and the current direction in the target line is used as a reference, and the duty ratios of the on/off states of the first switching device and the second switching device in each regulating valve are determined, so as to regulate the current flowing through the regulating valves, thereby improving the degree of freedom of power flow control and realizing the reverse control of the dc power flow of the dc power transmission lines.
In this embodiment, a control device of a dc power flow controller is further provided, where the control device is used to implement the foregoing embodiments and preferred embodiments, and details are not repeated after the description is given. As used below, the term "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated.
The present embodiment provides a control device of a dc power flow controller, as shown in fig. 8, including:
and an obtaining module 31, configured to obtain a current direction flowing into the dc power flow controller when the voltage of the dc capacitor is controlled to be stable by the voltage stabilizing unit of the dc power flow controller. For a detailed description, reference is made to the corresponding related description of the above method embodiments, which is not repeated herein.
A determination module 32 for determining a current regulation strategy depending on the current direction. For a detailed description, reference is made to the corresponding related description of the above method embodiments, which is not repeated herein.
And the issuing module 33 is configured to issue a current regulation strategy to the regulation unit of the dc power flow controller, where the current regulation strategy is used to control on/off of each regulation valve in the regulation unit to regulate the dc current flowing through the power transmission line. For detailed description, reference is made to the corresponding related description of the above method embodiments, and details are not repeated herein.
The control device of the dc power flow controller provided in this embodiment determines a current regulation strategy according to a current direction by detecting the current direction flowing into the dc power flow controller, and then issues the current regulation strategy to the regulation unit of the dc power flow controller, so that each regulation valve regulates current according to the current regulation strategy, thereby implementing independent control of dc power flow of each transmission dc transmission line, and improving the degree of freedom of power flow control.
The control device of the dc power flow controller in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC circuit, a processor and a memory executing one or more software or fixed programs, and/or other devices that can provide the above functions.
Further functional descriptions of the modules are the same as those of the corresponding embodiments, and are not repeated herein.
The embodiment of the invention also provides a non-transitory computer storage medium, where the computer storage medium stores computer-executable instructions, and the computer-executable instructions can execute the processing method of the control method of the direct current power flow controller in any method embodiment. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a Flash Memory (Flash Memory), a Hard Disk (Hard Disk Drive, abbreviated as HDD), a Solid State Drive (SSD), or the like; the storage medium may also comprise a combination of memories of the kind described above.
Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (10)

1. A topology structure of a direct current power flow controller is characterized by comprising:
the voltage stabilizing unit comprises an alternating current transformer and an inverter, wherein the alternating current transformer comprises an input end and an output end, the input end of the alternating current transformer is connected to an alternating current bus of a power transmission system, and the output end of the alternating current transformer is connected to the inverter;
the adjusting unit comprises a plurality of adjusting valves connected in parallel, and the output end of each adjusting valve is connected to each direct-current transmission line of the power transmission system;
and the direct current capacitor is arranged between the voltage stabilizing unit and the adjusting unit and is used for providing a stable direct current voltage source for the adjusting unit.
2. The topology of claim 1, wherein the inverter is a two-level, three-phase inverter.
3. The topology of claim 1, wherein a plurality of the regulator valves are identical in structure.
4. The topology of claim 3, wherein the regulation valve comprises a first switching device and a second switching device, the first switching device and the second switching device being connected in a half-bridge configuration.
5. The topology of claim 1, wherein the input of the alternating current transformer comprises a first terminal, a second terminal, and a third terminal;
the first terminal, the second terminal, and the third terminal are connected to an a-phase ac bus, a B-phase ac bus, and a C-phase ac bus of an ac power grid, respectively.
6. The topology structure of claim 5, wherein an output end of one of the regulating valves in the regulating unit is connected to a convergence point of different DC transmission lines, and output ends of the other regulating valves are respectively connected to different DC transmission lines.
7. A control method of a dc power flow controller, which is applied to the topology of the dc power flow controller according to any one of claims 1 to 6, the control method of the dc power flow controller comprising:
under the condition that the voltage of a direct current capacitor is controlled to be stable through a voltage stabilizing unit of the direct current power flow controller, the direction of current flowing into the direct current power flow controller is obtained;
determining a current regulation strategy according to the current direction;
and issuing the current regulation strategy to a regulation unit of the direct current power flow controller, wherein the current regulation strategy is used for controlling the connection or disconnection of each regulating valve in the regulation unit so as to regulate the direct current flowing through the power transmission line.
8. The method of claim 7, wherein determining a current regulation strategy based on the current direction comprises:
acquiring target lines where convergent points of different direct current transmission lines are located;
determining the duty ratio of the first switching device and the second switching device in each regulating valve for conducting or breaking by taking the current direction in the target line as a reference;
and generating the current regulation strategy according to the duty ratio.
9. The method of claim 8, wherein the generating the current regulation strategy according to the duty cycle comprises:
when the current direction is that the current flows out of the convergent point, determining a first current regulation strategy, wherein the first current regulation strategy comprises a first control instruction and a second control instruction;
the first control instruction is used for controlling a first switching device of the regulating valve connected to the convergent point to keep a conducting state, and a second switching device of the regulating valve to keep a closing state;
and the second control instruction is used for controlling second switching devices of other regulating valves to be complementarily switched on or switched off according to the first duty ratio.
10. The method of claim 8, wherein the generating the current regulation strategy according to the duty cycle comprises:
when the current direction is that the current flows into the convergence point, determining a second current regulation strategy, wherein the second current regulation strategy comprises a third control instruction and a fourth control instruction;
the third control instruction is used for controlling a first switching device of the regulating valve connected to the convergence point to keep an off state, and a second switching device of the regulating valve to keep an on state;
and the fourth control instruction is used for controlling the second switching devices of other regulating valves to be complementarily switched on or switched off according to a second duty ratio.
CN202210838620.7A 2022-07-18 2022-07-18 Topological structure of direct current power flow controller and control method Pending CN114928093A (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105162105A (en) * 2015-09-22 2015-12-16 中国科学院电工研究所 DC power supply power flow controller topology
US20170098936A1 (en) * 2014-05-19 2017-04-06 Nr Electric Co., Ltd. Unified power flow controller for double-circuit line
CN111525540A (en) * 2020-05-21 2020-08-11 哈尔滨工业大学 Hybrid modular direct current power flow controller and control method thereof
CN111682518A (en) * 2020-05-08 2020-09-18 江苏科能电力工程咨询有限公司 Power controller based on fuzziness
CN111756042A (en) * 2020-07-23 2020-10-09 上海交通大学 Capacitance type full-bridge three-line direct current power flow controller and bidirectional operation method thereof
US20210203247A1 (en) * 2019-07-26 2021-07-01 Shanghai Jiao Tong University Modular multilevel converter with multi-port dc power flow control and control method thereof
CN114421482A (en) * 2022-01-25 2022-04-29 上海交通大学 Mesh direct current system, multi-port direct current power flow control system and control method

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170098936A1 (en) * 2014-05-19 2017-04-06 Nr Electric Co., Ltd. Unified power flow controller for double-circuit line
CN105162105A (en) * 2015-09-22 2015-12-16 中国科学院电工研究所 DC power supply power flow controller topology
US20210203247A1 (en) * 2019-07-26 2021-07-01 Shanghai Jiao Tong University Modular multilevel converter with multi-port dc power flow control and control method thereof
CN111682518A (en) * 2020-05-08 2020-09-18 江苏科能电力工程咨询有限公司 Power controller based on fuzziness
CN111525540A (en) * 2020-05-21 2020-08-11 哈尔滨工业大学 Hybrid modular direct current power flow controller and control method thereof
CN111756042A (en) * 2020-07-23 2020-10-09 上海交通大学 Capacitance type full-bridge three-line direct current power flow controller and bidirectional operation method thereof
CN114421482A (en) * 2022-01-25 2022-04-29 上海交通大学 Mesh direct current system, multi-port direct current power flow control system and control method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
武文: "多端口直流潮流控制器的研究", 《中国优秀博硕士学位论文全文数据库（博士）工程科技II辑》 *

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Application publication date: 20220819