CN109638829B - No-sewing ring power conversion device for 10kV power distribution network - Google Patents
No-sewing ring power conversion device for 10kV power distribution network Download PDFInfo
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Abstract
The application relates to a seamless ring power conversion device of a 10kV power distribution network, wherein the direct current side of a series voltage compensator is connected with the direct current side of a parallel voltage converter; each phase in the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter; the parallel voltage converter comprises a parallel transformer and a three-phase voltage source type converter; each group of series voltage compensators is used for connecting one group of feeder lines in series and compensating the system voltages of the two groups of feeder lines in opposite directions. Therefore, two feeder lines of different power supplies are connected in series, the accuracy of a loop closing equivalent model is not relied on, loop closing risks caused by equipment overload, protection misoperation and the like due to overlarge loop closing power flow are avoided, the power grid safety risks caused by judging the inappropriately and inappropriately closed loop of the power distribution network by dispatching operators are reduced, the uncertainty of loop closing operation is reduced, the success rate of loop closing and power conversion is improved, and the reliability of regional power grid power supply is further enhanced.
Description
Technical Field
The application relates to the field of closed loop power conversion of 10kV power distribution networks, in particular to a seamless loop power conversion device for a 10kV power distribution network, which eliminates closed loop current.
Background
With the continuous forward development of the times, the electric power requirement for people to pursue good life is gradually changed into the starting point and the foothold of the work of the power supply enterprises. In links such as transmission and transformation power distribution, the construction of a power distribution network is relatively lagged, but with the enhancement of service consciousness of power supply enterprises and the prominence of electric power commodity attributes, the investment of the power distribution network is enlarged year by year, and the reliability and even the satisfaction of power consumption of users are more and more valued. The distribution network is used as the last link of the power system, directly influences the power supply quality of users, has obvious influence on daily life, and power supply enterprises need to strictly control the power failure time and the power failure times.
Considering short-circuit current and other factors, the domestic power distribution network follows the principles of closed-loop design and open-loop operation, loads are usually supplied by a single power supply, and areas supplied by different power supplies are isolated by adopting a tie switch. In the actual production and operation process of the distribution network, maintenance equipment or feeder line load peak time is fully loaded, and loop closing power conversion is often considered. The power failure gap that stops before turns is not existed in the loop closing power transferring, but if the loop closing power transferring mode is adopted, the power flow distribution of the power grid during loop closing is related to the real-time running condition of the system, the system analysis of the loop closing power transferring risk is difficult, the judgment deviation is easy to be caused, and the actual operation result has randomness. If the closed-loop power flow is too large, overload of equipment, misoperation of relay protection, exceeding of short-circuit current, expansion of accidents caused by electromagnetic looped network and the like are caused.
At present, a method for establishing a closed-loop equivalent model is mostly adopted, and the trend is calculated so as to evaluate the closed-loop risk. Whether the economic evaluation or the technical evaluation is carried out, the method is a judgment on whether the circulation value is in an acceptable range before closing the ring, and the circulation cannot be eliminated.
Disclosure of Invention
Based on the above, it is necessary to provide a seamless ring power conversion device for a10 kV power distribution network.
The seamless ring power conversion device of the 10kV power distribution network comprises a series voltage compensator and a parallel voltage converter, wherein the direct current side of the series voltage compensator is connected with the direct current side of the parallel voltage converter; the series voltage compensator is used for realizing split-phase compensation, and each phase in the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter; the parallel voltage converter comprises a parallel transformer and a three-phase voltage source type converter; and the 10kV distribution network seamless ring power conversion device comprises two groups of series voltage compensators, wherein each group of series voltage compensators is used for connecting a group of feeder lines in series and compensating the system voltages of the two groups of feeder lines in opposite directions.
According to the seamless ring power conversion device for the 10kV power distribution network, two feeder lines of different power supplies are connected in series, the accuracy of a ring closing equivalent model is not depended, a parallel voltage converter is matched with the design of two groups of series voltage compensators, circulation generated in the ring closing process is eliminated, ring closing risks caused by equipment overload, protection misoperation and the like due to overlarge ring closing tide are avoided, the power grid safety risks caused by judging the inappropriately and inaudible ring closing experience of a dispatching operator on the power distribution network are reduced, the uncertainty of ring closing operation is reduced, the success rate of ring closing power conversion is improved, and the power supply reliability of a regional power grid is further enhanced.
In one embodiment, the single-phase voltage source converter is provided with a plurality of first parallel coupling structures connected in parallel with each other and is used for inhibiting circulation among the converters of each stage.
In one embodiment, the single-phase voltage source converter is configured to coordinate two of the series voltage compensators to maintain three-phase symmetry of the compensated system voltage.
In one embodiment, the single-phase voltage source type converter is further configured to comprehensively regulate and control the command reference compensation voltage signals of the single-phase voltage source type converters according to a real-time system operation mode.
In one embodiment, the three-phase voltage source converter is provided with a plurality of second parallel structures connected in parallel with each other and is used for reducing the harmonic content of the input current.
In one embodiment, the parallel voltage converters are respectively connected to two circuit breakers, and the parallel voltage converters are connected to the series voltage compensator by each of the circuit breakers and are used for connecting the set of feeder lines.
In one embodiment, the shunt transformer employs a Y/. DELTA.connection.
In one embodiment, the shunt transformer is arranged according to the design capacity.
In one embodiment, the power distribution network is a 10kV power distribution network.
In one embodiment, the line voltage compensation degree of the 10kV distribution network seamless ring power conversion device, the transformation ratio of the parallel voltage converters, the transformation ratio of the series voltage compensators and the direct current voltage are set according to design requirements.
In one embodiment, the line voltage compensation degree is 5%, the transformation ratio of the parallel voltage converter is selected to be 10kV/250V, the transformation ratio of the series voltage compensator is selected to be 250V/250V, and the direct current voltage is regulated to be 500V.
Drawings
Fig. 1 is a schematic diagram of an application framework according to an embodiment of the application.
Fig. 2 is a schematic diagram of a parallel voltage converter according to the embodiment shown in fig. 1.
Fig. 3 is a schematic diagram of a single-phase voltage source type converter according to the embodiment shown in fig. 1.
Detailed Description
In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.
It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The application mainly aims to provide a seamless loop power transfer device which eliminates the loop current in the loop power transfer process of a 10kV power distribution network. In one embodiment, a 10kV distribution network seamless ring power conversion device comprises a series voltage compensator and a parallel voltage converter, wherein the direct current side of the series voltage compensator is connected with the direct current side of the parallel voltage converter; the series voltage compensator is used for realizing split-phase compensation, and each phase in the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter; the parallel voltage converter comprises a parallel transformer and a three-phase voltage source type converter; and the 10kV distribution network seamless ring power conversion device comprises two groups of series voltage compensators, wherein each group of series voltage compensators is used for connecting a group of feeder lines in series and compensating the system voltages of the two groups of feeder lines in opposite directions. According to the seamless ring power conversion device for the 10kV power distribution network, two feeder lines of different power supplies are connected in series, the accuracy of a ring closing equivalent model is not depended, a parallel voltage converter is matched with the design of two groups of series voltage compensators, circulation generated in the ring closing process is eliminated, ring closing risks caused by equipment overload, protection misoperation and the like due to overlarge ring closing tide are avoided, the power grid safety risks caused by judging the inappropriately and inaudible ring closing experience of a dispatching operator on the power distribution network are reduced, the uncertainty of ring closing operation is reduced, the success rate of ring closing power conversion is improved, and the power supply reliability of a regional power grid is further enhanced.
In one embodiment, a 10kV distribution network seamless ring power conversion device comprises a part of or all of the structures of the following embodiments; namely, the seamless ring power conversion device of the 10kV power distribution network comprises part of or all of the following technical characteristics.
In one embodiment, a seamless ring power conversion device for a 10kV power distribution network comprises a series voltage compensator and a parallel voltage converter. The series voltage compensator adopts the principle of split-phase compensation, each phase consists of a series coupling transformer and a single-phase voltage source type converter, the single-phase voltage source type converter adopts a multistage parallel structure to improve the current capacity, and the control strategy can inhibit the circulation among the converters at all levels and reduce the harmonic content of the output voltage. The parallel voltage converter consists of a parallel transformer and a three-phase voltage source converter, the direct current side of the series voltage compensator is connected with the direct current side of the parallel voltage converter, the three-phase voltage source converter adopts a multi-stage parallel structure to improve the current capacity, and the control strategy can reduce the harmonic content of input current. The series voltage compensator generates expected compensation voltage and is coupled with system voltage to realize phase shift control of line voltage. Active power circulates through the parallel voltage converter and the series voltage compensator, can be absorbed by the parallel voltage converter from the system, flows to the series voltage compensator via a direct current capacitor and finally is injected into the system, and vice versa. Meanwhile, the parallel voltage converter and the series voltage compensator can exchange reactive power with a system independently at an alternating current output end of the parallel voltage converter and the series voltage compensator. In one embodiment, the 10kV distribution network seamless ring power conversion device comprises two groups of series voltage compensators, and the control strategy of the single-phase voltage source type converter is to enable the system voltages of two feeder lines to be compensated in opposite directions, so that the difference of the through-flow sizes between the two feeder lines and the series voltage compensators is reduced. The control strategy of the single-phase voltage source type converter is to coordinate and regulate the two series voltage compensators at the same time, ensure that the compensated system voltage is always three-phase symmetrical, and comprehensively regulate and control the command reference compensation voltage signals of the single-phase voltage source type converters according to the real-time system operation mode. In one embodiment, the line voltage compensation degree of the 10kV distribution network seamless ring power conversion device, the transformation ratio of the parallel voltage converters, the transformation ratio of the series voltage compensators and the direct current voltage are set according to design requirements. In one embodiment, the line voltage compensation degree is 5%, the transformation ratio of the parallel voltage converter is selected to be 10kV/250V, the transformation ratio of the series voltage compensator is selected to be 250V/250V, and the direct current voltage is regulated to be 500V. Therefore, the distribution network can be ensured to be powered on and off without generating circulation in the loop closing process; moreover, after the seamless ring power conversion device for the 10kV power distribution network is adopted, the ring closing power conversion operation steps of the power distribution network are unchanged, and the operation is convenient.
In one embodiment, a 10kV distribution network seamless ring power conversion device comprises a parallel voltage converter and two groups of series voltage compensators, wherein the direct current side of each series voltage compensator is connected with the direct current side of each parallel voltage converter; each group of series voltage compensators are used for connecting one group of feeder lines in series and compensating the system voltages of the two groups of feeder lines in opposite directions; in one embodiment, the 10kV distribution network seamless ring power conversion device is provided with three input ends and three output ends for each group of feeder lines. Thus, each set of feeders is connected in from three inputs and out from three outputs, respectively. In one embodiment, the 10kV power distribution network seamless ring power conversion device comprises a series voltage compensator and a parallel voltage converter, wherein the direct current side of the series voltage compensator is connected with the direct current side of the parallel voltage converter; each phase of the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter; the parallel voltage converter comprises a parallel transformer and a three-phase voltage source type converter; the 10kV distribution network seamless ring power conversion device comprises two groups of series voltage compensators, wherein each group of series voltage compensators is used for being connected into one group of feeder lines in series; the single-phase voltage source type converter is provided with n first parallel structures which are mutually connected in parallel; the three-phase voltage source type converter is provided with m second parallel structures which are mutually connected in parallel.
In one embodiment, the series voltage compensator generates a desired compensation voltage coupled to the system voltage to effect phase shift control of the line voltage. In one embodiment, the series voltage compensator is used for realizing split-phase compensation, and each phase of the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter; in one embodiment, the series voltage compensator adopts the principle of split-phase compensation, and each phase consists of a series coupling transformer and a single-phase voltage source type converter. In one embodiment, the single-phase voltage source converter is provided with a plurality of first parallel structures connected in parallel with each other. Further, in one embodiment, the series voltage compensator is configured to perform the main function of eliminating the circulating current of the seamless ring power conversion device, and a synchronous series voltage with adjustable amplitude and phase is injected into the power distribution network system through the series coupling transformer, where the amplitude of the voltage is related to the system voltage level, and the phase of the voltage can be changed in four quadrants. The injection voltage can be regarded as a synchronous alternating current voltage source, and the amplitude and the phase of the voltages of the two feeder lines are compensated phase by phase, so that the amplitude and the phase of the voltages of each phase on the two feeder lines are identical under the condition that the three-phase voltage is kept symmetrical. When the feeder current flows through the series voltage compensator, the two interact to produce an exchange of active and reactive power.
In one embodiment, the single-phase voltage source converter is provided with a plurality of first parallel coupling structures connected in parallel with each other and is used for inhibiting circulation among the converters of each stage. Wherein the plurality includes 2 or more. In one embodiment, the plurality of first parallel structures connected in parallel with each other is n first parallel structures connected in parallel with each other. In one embodiment, the single-phase voltage source converter is configured to coordinate two of the series voltage compensators to maintain three-phase symmetry of the compensated system voltage. In one embodiment, the single-phase voltage source type converter is further configured to comprehensively regulate and control the command reference compensation voltage signals of the single-phase voltage source type converters according to a real-time system operation mode. In one embodiment, the control strategy of the single-phase voltage source converter is used for comprehensively regulating and controlling the command reference compensation voltage signals of the single-phase voltage source converters according to the real-time system operation mode. In one embodiment, n is 2 to 100; i.e. the number of parallel stages of the first parallel structure is 2 to 100, and so on for the rest of the embodiments. In one embodiment, n is 2, i.e. the single-phase voltage source converter has 2 first parallel structures connected in parallel with each other. In one embodiment, n is 5, i.e. the single-phase voltage source converter has 5 first parallel structures connected in parallel with each other, the remaining embodiments and so on.
In one embodiment, the first parallel structure comprises a first capacitor, a second capacitor, four insulated gate bipolar transistors (Insulated Gate Bipolar Transistor, IGBTs), a first inductor, and a second inductor; the four IGBTs form a double bridge arm, are connected in parallel with a first capacitor and are used for being connected in parallel with other first parallel structures, the four insulated gate bipolar transistors comprise first insulated gate bipolar transistors to fourth insulated gate bipolar transistors, a first end of a first inductor is connected between the first insulated gate bipolar transistor and a third insulated gate bipolar transistor, a first end of a second inductor is connected between the second insulated gate bipolar transistor and the fourth insulated gate bipolar transistor, a second end of the first inductor is connected with a second end of the second inductor through the second capacitor, the second end of the first inductor is also used for being connected with a second end of the first inductor of other first parallel structures, and the second end of the second inductor is also used for being connected with a second end of the second inductor of other first parallel structures. By adopting the design, the through-current capacity can be improved, the circulation among converters at all levels can be controlled and inhibited, and the harmonic content of the output voltage can be reduced. In one embodiment, as shown in fig. 3, the single-phase voltage source converter is provided with a plurality of first parallel structures connected in parallel, and each first parallel structure comprises a first capacitor, a second capacitor, a first inductor, a second inductor and four IGBTs; the four IGBTs form a double bridge arm, are connected with the first capacitor in parallel, and are connected with other first parallel connection structures in parallel; the first end of the first inductor is connected between two IGBTs of a bridge arm, the second end of the first inductor is connected with the second ends of the first inductors of other first parallel structures, and the second ends of the first inductors are also connected with the second ends of the second inductors through second capacitors; the first end of the second inductor is connected between two IGBTs of the other bridge arm, and the second end of the second inductor is also connected with the second ends of the second inductors of other first parallel structures.
Further, in one embodiment, the parallel voltage converter is configured to inject or absorb reactive power into the power distribution network system through the parallel transformer, and maintain the ac voltage of the parallel point system; active power is injected or absorbed into the power distribution network system through the parallel transformer, and the requirement that the series voltage compensator exchanges active power with the system at the coupling point is met. In one embodiment, the parallel voltage converter includes a parallel transformer and a three-phase voltage source converter; in one embodiment, the parallel voltage converter is comprised of a parallel transformer and a three-phase voltage source converter. In one embodiment, the parallel voltage converters are respectively connected to two circuit breakers, and the parallel voltage converters are connected to the series voltage compensator by each of the circuit breakers and are used for connecting the set of feeder lines. In one embodiment, the parallel voltage converters are respectively connected into two feeder lines through the circuit breakers, and when in operation, one side of the circuit breakers is closed, the other side of the circuit breakers is opened, and electricity is taken from the transfer feeder lines. In one embodiment, the shunt transformer employs a Y/. DELTA.connection. In one embodiment, the shunt transformer is arranged according to the design capacity.
In one embodiment, the three-phase voltage source converter is provided with a plurality of second parallel structures connected in parallel with each other. In one embodiment, the three-phase voltage source converter is provided with a plurality of second parallel structures connected in parallel with each other and is used for reducing the harmonic content of the input current. Wherein the plurality includes 2 or more. In one embodiment, the plurality of second parallel structures connected in parallel with each other is m second parallel structures connected in parallel with each other. In one embodiment, m is 2 to 100; i.e. the number of parallel stages of the second parallel structure is 2 to 100, and so on for the rest of the embodiments. In one embodiment, m is 3, i.e. the single-phase voltage source converter has 3 second parallel structures connected in parallel with each other. In one embodiment, m is 6, i.e. the single-phase voltage source converter has 6 second parallel structures connected in parallel with each other.
In one embodiment, the second parallel structure has a three-phase three-leg structure. In one embodiment, the second parallel structure includes three inductors, a third capacitor and six insulated gate bipolar transistors, where the six insulated gate bipolar transistors form three legs and are connected in parallel with the third capacitor and are used to connect in parallel with other second parallel structures, two insulated gate bipolar transistors are connected to each leg and a phase ac circuit is connected between them, and each leg is connected to the phase out-of-phase ac circuit, i.e., the different phase ac circuits, respectively, through an inductor, i.e., each leg is connected to a phase ac circuit through an inductor. By adopting the design, the through-current capacity can be improved, and the harmonic content of the input current can be reduced by matching with control. In one embodiment, as shown in fig. 2, the parallel voltage converter includes a parallel transformer and a three-phase voltage source converter, where the three-phase voltage source converter is provided with a plurality of second parallel structures connected in parallel to each other, each second parallel structure has a three-phase three-bridge arm structure, and the second parallel structure includes a third capacitor and six insulated gate bipolar transistors, where the six insulated gate bipolar transistors form three bridge arms and are connected in parallel with the third capacitor and are used in parallel with other second parallel structures, two insulated gate bipolar transistors are provided on each bridge arm and are connected with a phase ac circuit therebetween, and each bridge arm is respectively connected with a phase out-of-phase ac circuit.
In one embodiment, the first parallel structure is arranged in parallel with the second parallel structure. That is, in one embodiment, the first parallel structure and the second parallel structure of each embodiment are arranged in parallel, and the rest of embodiments are the same, and will not be described again. Further, in one of the embodiments, the parallel voltage converter and the series voltage compensator are each configured to exchange reactive power independently from the power distribution network system at an ac output. By the design, the circulation generated in the loop closing and power transferring process of the power distribution network, particularly the 10kV power distribution network, is avoided, equipment overload, protection misoperation and the like caused by overlarge loop closing flow are avoided, the power network safety risk caused by judging the experience of the non-observable and non-measurable loop closing of the power distribution network by dispatching operators is reduced, the success rate of loop closing and power transferring is improved, and the reliability of power supply of regional power networks is further enhanced.
In one embodiment, the 10kV power distribution network seamless ring power conversion device is arranged in a power distribution room, wherein the power distribution room comprises 2 or more different feeder lines, and two feeder lines with a connecting switch are selected to be connected into the 10kV power distribution network seamless ring power conversion device.
The 10kV distribution network seamless ring power conversion device is characterized in that 12 access points are connected with the outside, and a feeder line 1 is led in by A F1、BF1、CF1 and led out by A' F1、B'F1、C'F1; for feeder 2, it is introduced by a F2、BF2、CF2, and exits through a' F2、B'F2、C'F2. The seamless ring power conversion device of the 10kV power distribution network comprises 1 group of parallel voltage converters and 2 groups of series voltage compensators, wherein the parallel voltage compensators are connected with a feeder 1 through BK1, the parallel voltage compensators are connected with a feeder 2 through BK2, and the series voltage compensators are connected with the direct current side of the parallel voltage converters.
The parallel voltage converter comprises a parallel transformer T sh and a three-phase voltage source converter, and the parallel transformer T sh adopts a Y/[ delta ] connection method. The system voltage of the feeder line 1 or the feeder line 2, specifically the access feeder line is determined by the loop closing transfer to the feeder line, is reduced by T sh to obtain U sh, and is used as the input voltage of the three-phase voltage source type converter. And regulating and controlling the three-phase voltage source converter to ensure that the amplitude of the direct-current side voltage U dc is stable and the direct-current side voltage U dc is fast in response to the active power required by the series voltage compensator. The parallel voltage converter is an essential component of the embodiments of the application, and is an essential ring for forming active power circulation flow.
The capacity requirement of the 10kV distribution network seamless ring power conversion device can be met under different conditions, the parallel transformer T sh in the parallel voltage converter can be correspondingly selected according to the design capacity, and the three-phase voltage source converter can adopt a multi-stage parallel structure to improve the current capacity, as shown in figure 2. When the parallel series number of the three-phase voltage source type converters is 2 or more, the regulation strategy of the three-phase voltage source type converters has the function of inhibiting the circulation among the converters at all levels, and meanwhile, harmonic components of input current are further reduced.
The series voltage compensator comprises a series coupling transformer T se and a single-phase voltage source type converter, wherein the single-phase voltage source type converter adopts a common direct current bus design, and the direct current sides of all the single-phase voltage source type converters on the two feed lines are connected with each other and connected with the direct current sides of the parallel voltage converters. The direct current voltage U dc is converted by each single-phase voltage source type converter to obtain compensation voltage, and U se is coupled into the system voltage of each phase of the feeder line through T se. And regulating and controlling the corresponding single-phase voltage source converters of the two feeder lines, so that the amplitude and the phase of the compensated feeder line system voltage U r are the same. The control strategy of the single-phase voltage source type converter is to make the system voltages of the two feeder lines compensate in opposite directions, and reduce the difference of the through-flow between the series voltage compensators of the two feeder lines. The control strategy of the single-phase voltage source type converter is to coordinate and regulate the two series voltage compensators at the same time, ensure that the compensated system voltage is always three-phase symmetrical, and comprehensively regulate and control the command reference compensation voltage signals of the single-phase voltage source type converters according to the real-time system operation mode.
The structure of the single-phase voltage source type converter in the series voltage compensator is shown in fig. 3, and the through-current capacity is improved by adopting a multistage parallel structure. When the parallel series number of the single-phase voltage source type converters is 2 or more, the regulation strategy of the single-phase voltage source type converters has the function of inhibiting the circulation among the converters at all levels, and meanwhile, harmonic components of output voltage are further reduced. The line voltage compensation degree of the embodiment is 5%, the T sh transformation ratio of the parallel voltage converter is selected to be 10kV/250V, the T se transformation ratio of the series voltage compensator is selected to be 250V/250V, and the direct current voltage U dc is regulated to be 500V.
When the feeder 1 needs to be withdrawn, the circuit breaker BK2 is closed, the circuit breaker BK1 is opened, the direct current side is charged, the series voltage compensator injects coupling voltages U se1 and U se2 into the system, the feeder 1 outputs U r1 at A 'F1、B'F1、C'F1 under the regulation of a control strategy, and the feeder 2 outputs U r2,Ur1 and U r2 with consistent amplitude and phase at A' F2、B'F2、C'F2. After the amplitude and the phase of U r1 and U r2 are detected to be consistent, a 10kV ring main unit S0 switch is closed, and no circulation current exists in the ring closing process. The S1 switch is opened, and the feeder line 1 is out of operation. When the operation mode is restored, the process is similar. Therefore, the circulation generated in the loop closing and power transferring process of the 10kV power distribution network can be eliminated, the power distribution network can be ensured not to be powered off and transferred, the circulation is not generated in the loop closing process, equipment overload, protection misoperation and the like caused by overlarge loop closing power flow are avoided, the power network safety risk caused by judging the inappropriately and inappropriately tested loop closing experience of the power distribution network by dispatching operators is reduced, the loop closing and power transferring operation steps of the power distribution network are unchanged, the success rate of loop closing and power transferring is improved, and the power supply reliability of regional power networks is further enhanced.
It should be noted that other embodiments of the present application further include a10 kV distribution network seamless ring power conversion device formed by combining technical features of the foregoing embodiments.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be determined from the following claims.
Claims (10)
1. The seamless ring power conversion device of the 10kV power distribution network is characterized by comprising a series voltage compensator and a parallel voltage converter, wherein the direct current side of the series voltage compensator is connected with the direct current side of the parallel voltage converter;
The series voltage compensator is used for realizing split-phase compensation, and each phase in the series voltage compensator comprises a series coupling transformer and a single-phase voltage source type converter;
the parallel voltage converter comprises a parallel transformer and a three-phase voltage source type converter;
The 10kV distribution network seamless ring power conversion device comprises two groups of series voltage compensators, wherein each group of series voltage compensators is used for connecting one group of feeder lines in series and compensating the system voltages of the two groups of feeder lines in opposite directions;
The series voltage compensator injects a synchronous series voltage with adjustable amplitude and phase to the power distribution network system through a series coupling transformer, the amplitude of the synchronous series voltage is related to the system voltage level, the phase of the voltage can be changed in four quadrants, the synchronous series voltage is used as a synchronous alternating voltage source, the amplitude and the phase of the voltages of two feeder lines are compensated phase by phase, and the amplitude and the phase of each phase voltage on the two feeder lines are the same under the condition of keeping the three-phase voltage symmetrical, and when the feeder line current flows through the series voltage compensator, the two voltages are interacted to generate active power and reactive power exchange;
The parallel voltage converter is used for injecting or absorbing reactive power into the power distribution network system through the parallel transformer and maintaining the alternating voltage of the parallel point system; active power is injected or absorbed into the power distribution network system through the parallel transformer, and the requirement that the series voltage compensator exchanges active power with the system at the coupling point is met.
2. The 10kV distribution network seamless ring power conversion apparatus according to claim 1, wherein the single-phase voltage source converter is provided with a plurality of first parallel connection structures connected in parallel with each other and is used for suppressing a circulation current between the converters of each stage;
The first parallel connection structure comprises a first capacitor, a second capacitor, four insulated gate bipolar transistors, a first inductor and a second inductor; the four insulated gate bipolar transistors form a double bridge arm, are connected in parallel with the first capacitor and are used for being connected in parallel with other first parallel connection structures, the four insulated gate bipolar transistors comprise first insulated gate bipolar transistors to fourth insulated gate bipolar transistors, a first end of a first inductor is connected between the first insulated gate bipolar transistor and the third insulated gate bipolar transistor, a first end of a second inductor is connected between the second insulated gate bipolar transistor and the fourth insulated gate bipolar transistor, a second end of the first inductor is connected with a second end of the second inductor through the second capacitor, the second end of the first inductor is also used for being connected with a second end of the first inductor of other first parallel connection structures, and the second end of the second inductor is also used for being connected with a second end of the second inductor of other first parallel connection structures.
3. The 10kV distribution network seamless ring switching device according to claim 2, wherein the single-phase voltage source converter is configured to coordinate two of the series voltage compensators so that the compensated system voltage remains three-phase symmetric.
4. The 10kV distribution network seamless ring power conversion device according to claim 3, wherein the single-phase voltage source type converters are further used for comprehensively regulating and controlling and then issuing command reference compensation voltage signals of the single-phase voltage source type converters according to a real-time system operation mode.
5. The 10kV distribution network seamless ring power conversion device according to claim 1, wherein the three-phase voltage source converter is provided with a plurality of second parallel structures connected in parallel with each other and is used for reducing harmonic content of input current;
The second parallel structure is provided with a three-phase three-bridge-arm structure and comprises three inductors, a third capacitor and six insulated gate bipolar transistors, wherein the six insulated gate bipolar transistors form three bridge arms and are connected with the third capacitor in parallel and are used for being connected with other second parallel structures in parallel, each bridge arm is provided with two insulated gate bipolar transistors and is connected with a phase alternating current circuit therebetween, and each bridge arm is connected with the phase alternating current circuit through an inductor.
6. The 10kV distribution network seamless ring power transfer device according to claim 1, wherein the parallel voltage converters are respectively connected to two circuit breakers, and the parallel voltage converters are connected to the series voltage compensator through each circuit breaker and are used to connect the set of feeder lines.
7. The 10kV distribution network seamless ring transfer device of claim 1, wherein the shunt transformer employs a Y/delta connection method.
8. The 10kV distribution network seamless ring power transfer device according to claim 1, wherein the shunt transformer is configured according to a design capacity.
9. The 10kV distribution network seamless ring transfer device of any one of claims 1 to 8, wherein the distribution network is a 10kV distribution network.
10. The 10kV distribution network seamless ring power conversion device according to claim 9, wherein the line voltage compensation degree of the 10kV distribution network seamless ring power conversion device is set according to design requirements, the transformation ratio of the parallel voltage converters, the transformation ratio of the series voltage compensator and the direct current voltage.
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| CN113078635B (en) * | 2021-04-07 | 2022-10-28 | 广东电网有限责任公司广州供电局 | Multi-port back-to-back type seamless ring power conversion device and method |
| CN113054662B (en) * | 2021-04-30 | 2022-11-01 | 江苏省电力试验研究院有限公司 | AC medium-voltage distribution network ring closing and opening device and control method |
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