CN116436066A - Three-phase distribution network type power electronic transformer and configuration optimization method - Google Patents
Three-phase distribution network type power electronic transformer and configuration optimization method Download PDFInfo
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
- H02J3/322—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means the battery being on-board an electric or hybrid vehicle, e.g. vehicle to grid arrangements [V2G], power aggregation, use of the battery for network load balancing, coordinated or cooperative battery charging
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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
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- 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
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/10—The dispersed energy generation being of fossil origin, e.g. diesel generators
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/30—The power source being a fuel cell
Abstract
The invention discloses a three-phase distribution network type power electronic transformer and a configuration optimization method, wherein the method comprises the following steps: the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side are filtered through a low-voltage side supporting capacitor and an inductor, and voltage phase shifting is performed through a preset control algorithm; and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1. By applying the three-phase distribution network type power electronic transformer and the configuration optimization method, the high-voltage side and low-voltage side supporting capacitance values are reduced by adopting the mode of the A-phase, B-phase and C-phase low-voltage direct current terminals in a series-parallel mode, so that the power density of the whole device is improved, the volume of the whole device is reduced, and the constraint pressure of an application scene on the volume of the device is reduced. In the prior art, a large capacity of supporting capacitor is needed to obtain the same voltage ripple range, so that the system volume, the cost and the power density are increased.
Description
Technical Field
The invention relates to the technical field of electrical equipment, in particular to a power electronic transformer optimization method and device.
Background
The solid state transformer (Solid state transformer, SST), also known as a power electronic transformer (Power Electronic Transformer, PET), is a stationary electrical device that combines power electronic conversion technology with high frequency power conversion technology based on electromagnetic induction principles to convert power of one power characteristic to power of another. The power electronic transformer has the advantages of electric isolation, active power control and portabilityThe system is used for the AC/DC interfaces with multiple voltage levels, and can realize energy routers, power flow scheduling of the power grid and interface equipment with different power grid modes so as to cope with the trend of the multidirectional flow of electric energy. Compared with the conventional transformer, the SST has a plurality of advantages, and the SST is characterized in that the flexible control of primary current, secondary voltage and power can be realized. When the SST is applied to a power system, the power quality is improved, the system stability is improved, and a flexible transmission mode and real-time control of power flow in a power market are realized. The SST is used in the field of new energy intelligent micro-grid at present, and is mainly used for solving the problem of voltage disturbance of a power distribution network in a traditional power grid. Generally, SST is subjected to multistage conversion, as shown in fig. 1, and the classical conversion topology is currently an AC-DC converter+high-frequency isolation type DC-dc+dc-AC converter, and the system conversion link is subjected to 2-stage DC link (supporting capacitor C dH And C dL ) A large number of support capacitors need to be arranged inside the system, which affects the volume and power density of the system. The support capacitor is too large in configuration, uneconomical and huge in system level, and the slower the response speed is controlled, the greater the hysteresis is; the support capacitor is too small in configuration, so that the direct-current voltage fluctuation is large, and oscillation is caused when the direct-current voltage fluctuation is severe, and the stability of the whole device and the system is affected.
Disclosure of Invention
The invention aims to solve the technical problems that: the support capacitor is too large in configuration, uneconomical and huge in system level, and the slower the response speed is controlled, the greater the hysteresis is; the support capacitor is too small in configuration, so that the direct-current voltage fluctuation is large, and oscillation is caused when the direct-current voltage fluctuation is severe, and the stability of the whole device and the system is affected.
In order to solve the technical problems, the invention provides a configuration optimization method of a three-phase distribution network type power electronic transformer, which comprises the following steps:
the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side are filtered through a low-voltage side supporting capacitor and an inductor, and voltage phase shifting is performed through a preset control algorithm;
and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1.
Optionally, the collecting the phase-shifted voltages after being mixed and connected to the bus includes:
respectively converging a first port in a link of the phase A, the phase B and the phase C of the low-voltage output side to obtain a phase R, a second port to obtain a phase S and a third port to obtain a phase T;
and outputting the R phase, the S phase and the T phase to a bus.
In order to solve the technical problems, the present invention provides a three-phase distribution network type power electronic transformer, comprising: the high-voltage side cascade H-bridge module, the DC-DC bidirectional converter and the low-voltage side H-bridge module are alternately connected in series and then output to the bus through the collecting port;
the sink port includes: and collecting the R phase by a first port, the S phase by a second port and the T phase by a third port in links of the A phase, the B phase and the C phase of the low-voltage output side.
Optionally, the three-phase distribution network type power electronic transformer comprises IGBT, IGCT, IPM or SiC MOSFETs.
Optionally, the topology of the three-phase distribution network type power electronic transformer includes: two-level, three-level, H-bridge cascade, chain, MMC version.
Optionally, the three-phase distribution network type power electronic transformer is provided with a filter.
One or more embodiments of the above-described solution may have the following advantages or benefits compared to the prior art:
by applying the three-phase distribution network type power electronic transformer and the configuration optimization method, the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side are filtered through the low-voltage side supporting capacitor and the inductor, and voltage phase shifting is performed through a preset control algorithm; and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1.
The capacity values of the high-voltage side supporting capacitor and the low-voltage side supporting capacitor are reduced by adopting a mode of series-parallel connection of the A-phase, B-phase and C-phase low-voltage direct current terminals, so that the power density of the whole device is improved, the volume of the whole device is reduced, and the constraint pressure of an application scene on the volume of the device is reduced. In addition, the small ripple voltage can be conveniently connected into other new energy sources and energy storage conversion devices, the problem that direct current voltage fluctuation under the parallel grid is large is not needed to be considered, and in the operation of a power grid system, particularly in the process of feeding back energy paths to the power grid, the electric energy quality of the whole device can be improved, and the friendliness of new energy sources and energy storage access is greatly improved. In addition, the mode of series-parallel connection of the low-voltage direct-current terminals of the phase A, the phase B and the phase C is adopted, a new hardware LC filter or other active frequency doubling control devices are not needed, the implementation is simple, and the operation is easy.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a power electronic transformer according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an SST energy routing-based ac/dc hybrid micro-grid system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a three-phase SST according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a conventional configuration of a three-phase SST output-side DC bus according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a conventional configuration of multiple and unified three-phase SST output side DC bus configuration according to an embodiment of the present invention;
fig. 6 is a flowchart of a configuration optimization method of a three-phase power electronic transformer according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a cross configuration of a DC bus on the output side of a three-phase SST according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a conventional configuration of multiple and unified three-phase SST output side DC bus configuration according to an embodiment of the present invention;
FIG. 9a is a simulated waveform corresponding to the grid side voltage and current of FIG. 4 under full load conditions;
FIG. 9b is a simulated waveform corresponding to the mid-level high side DC voltage of FIG. 4 under full load conditions;
FIG. 9c is a simulated waveform corresponding to the intermediate voltage on the low side of the output stage in the full load condition of FIG. 4;
FIG. 10a is a simulated waveform of grid side voltage and current corresponding to the full load condition of FIG. 7;
FIG. 10b is a simulated waveform corresponding to the mid-level high side DC voltage of FIG. 7 during full load conditions;
FIG. 10c is a simulated waveform corresponding to the intermediate voltage on the low side of the output stage in the full load condition of FIG. 7.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following detailed description of the implementation method of the present invention will be given with reference to the accompanying drawings and examples, by which the technical means are applied to solve the technical problems, and the implementation process for achieving the technical effects can be fully understood and implemented accordingly.
The energy internet is a new generation intelligent network which takes electric power as a core, and deeply fuses and interconnects energy and information. The realization of the energy internet is to start from a power distribution network, and the power electronic transformer is an open energy carrier and has the following characteristics: the transformer function can be realized, and the access of various AC/DC power equipment including a distributed power generation device can be realized; the electric quantity of each port can be controlled in real time, and the power grid requirements such as energy management, tide scheduling and the like are realized; the dynamic performance is good, and the capability of coping with short-circuit faults is provided; the power grid data acquisition can be easily completed, and a data basis is provided for the operation of the energy Internet. An ac/dc hybrid micro-grid with SST as a core is shown in fig. 2, which replaces the common connection point (Point of Common Coupling, PCC) to serve as a transfer station for energy flow among the power distribution network, the ac micro-grid, and the dc micro-grid.
The three-phase cascade type PWM rectifier is taken as an example, and the three-phase SST is shown in fig. 3, which includes the following three parts: the cascade part realizes AC-DC conversion, the converters on the two sides of the high-frequency transformer respectively realize DC-DC conversion of forward and reverse energy flow control, and the later stage realizes DC-AC conversion as required to be connected into a low-voltage power grid or other three-phase loads. The capacitor at the rear end of the front-stage cascade rectifier is referred to as a high-voltage side supporting capacitor, and the supporting capacitor of the DC link at the output side of the rear-stage isolation DC-DC is referred to as a low-voltage side DC capacitor.
In the prior art, the main mode of double frequency inhibition is that an LC filter and an active control device are additionally arranged in a circuit, however, the LC filter is huge in volume and needs to consider the matching of inductance value and capacitance value of LC, once the matching is not good, passive elements of the filter are extremely easy to generate heat, the safety and stability of the whole device are affected seriously, and in addition, the LC filter is easy to resonate with other passive elements or characteristic frequency harmonics such as switching order in a converter; the active control device needs to acquire analog quantities such as direct current and the like to be added into closed-loop control, and the active control device also needs to be provided with a reactor and a capacitor, so that the complexity of the device is increased, the control complexity is improved, and engineering application is difficult to realize in practical operation.
Referring to fig. 4 and fig. 5, fig. 4 is a schematic diagram of a conventional configuration of a three-phase SST output side dc bus provided by an embodiment of the present invention, and fig. 5 is a schematic diagram of a conventional configuration of multiple and unified three-phase SST output side dc bus configuration provided by an embodiment of the present invention. For the three-phase input three-phase output solid-state transformer system shown in fig. 4, three sets of output-side dc terminals P of each phase are typically provided A123 (by P A1 、P A2 And P A3 Assembled) and N A123 (by N A1 、N A2 And N A3 Assembled) is directly assembled to the output side single-phase bridge unit of the present phase, and the single-phase circuits C of three groups of input side branches dHA1 、C dHA2 、C dHA3 The double frequency of the direct-current voltage of (2) is transferred to the output side supporting capacitor C through high-frequency DC-DC dLA1 In this case, if a lower voltage fluctuation is desired, a larger output side capacitance is required. SecondThe larger double frequency pulsation at the output side can cause overlarge current double frequency pulsation of the high-frequency DC-DC converter, and the overcurrent fault of the converter is triggered when serious, so that the reliability of the whole device is affected. And finally, the excessive input and output side supporting capacitors increase the volume of a direct current link, influence the control rapidity of the whole system, cause control hysteresis while increasing the cost, and cause unstable problems such as middle voltage fluctuation or network side current oscillation of the system when serious.
On the one hand, the traditional scheme does not consider the adaptability of the new energy to the high-voltage or low-voltage direct current side. The input and the removal of a large amount of fluctuation load and the energy feed-in of a random new energy (wind power, photovoltaic, energy storage and the like) direct current grid-connected device cause direct current voltage fluctuation in an intermediate link, and the superimposed random component is easy to cause overvoltage and overcurrent faults due to larger fluctuation.
On the other hand, the conventional scheme does not consider the suitability of the intermediate energy-taking secondary power supply. The secondary power supply unit of the high-voltage power electronic transformer device is generally taken from an intermediate loop, larger ripple voltage fluctuation is needed to select a wider range of secondary power supply modules, and the overall cost of the system is increased; the voltage peak with larger fluctuation is easy to cause serious overvoltage of intermediate voltage, which leads to failure breakdown of the secondary power supply module, causes failure shutdown of the whole device and influences the stability of the system.
On the other hand, the conventional scheme does not consider the influence on the system pre-rectifier control and the DC-DC soft switching characteristic performance. The three-phase cascading PWM rectifier needs to perform phase internal voltage equalizing, phase-to-phase voltage equalizing and global voltage equalizing on the three-phase intermediate voltage, the control schemes finally perform comprehensive control by collecting the intermediate voltage of each level of single branch, and control software and algorithms can filter secondary pulsation through a filter and a wave trap, but always contain a certain frequency doubling component, so that the overall network side harmonic performance and voltage equalizing capacity of the system are affected; excessive voltage fluctuation causes tube voltage fluctuation in the DC-DC converter for the high-frequency DC-DC side, influences the charging and discharging process of junction capacitors in the commutation stage, and further easily triggers soft switch failure; the soft switch failure causes the loss increase of the switching device, the system efficiency of the whole device is influenced while the pressure of the heat radiation system is increased, and the failure fault of the switching device can be triggered when the system is serious.
In view of the above, the present invention provides a configuration optimization method for a three-phase distribution network type power electronic transformer, and the configuration optimization method for the three-phase distribution network type power electronic transformer is described below.
As shown in fig. 6, a flowchart of a configuration optimization method for a three-phase power electronic transformer according to an embodiment of the present invention may include the following steps:
step S101: the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side are filtered through a low-voltage side supporting capacitor and an inductor, and voltage phase shifting is performed through a preset control algorithm.
Specifically, the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side of the three-phase distribution network type power electronic transformer are filtered by a capacitor and an inductor to remove interference signals, and the corresponding control is applied through a preset control algorithm, so that grid connection (access to a power grid) and off-grid (three-phase/single-phase load) operation can be realized.
Step S102: and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1.
For example, when N is 2, six times of frequency voltage can be obtained after the phase shift of the low-voltage side supporting capacitor voltage, so that the amplitude of the output voltage can be effectively reduced. Of course, the present invention is not limited to specific values of N, that is, the present invention can shift the phase of the low voltage side into 6 times, 9 times, 12 times, etc., and the present invention is not limited to the values of N.
In one implementation manner, as shown in fig. 7, a first port, a second port and a third port in links of a phase a, a phase B and a phase C of the low-voltage output side may be respectively converged to obtain an R phase, a second port to obtain an S phase and a third port to obtain a T phase; and outputting the R phase, the S phase and the T phase to a bus.
Referring to fig. 8, the three-phase SST output side dc bus configuration multiplexing is provided in an embodiment of the present inventionThe unified traditional configuration schematic diagram firstly defines the low-voltage direct-current terminal of the three-phase triple cascade power electronic transformer system as: phase A (P) A1 ，P A2 ，P A3 ，N A1 ，N A2 ，N A3 ) B phase (P) B1 ，P B2 ，P B3 ，N B1 ，N B2 ，N B3 ) C phase (P) C1 ，P C2 ，P C3 ，N C1 ，N C2 ，N C3 ) The A phase, the B phase and the C phase low-voltage side direct current terminals are respectively and alternately summarized according to ABC phase, and the obtained three phases are expressed as R phase, S phase and T phase, wherein the connection form of the R phase low-voltage side direct current side is as follows: (P) A1 ，P B1 ，P C1 ，N A1 ，N B1 ，N C1 ) The S-phase low-voltage end direct current side connection mode is as follows: (P) A2 ，P B2 ，P C2 ，N A2 ，N B2 ，N C2 ) The direct current side connection form of the T-phase low-voltage end is as follows: (P) A3 ，P B3 ，P C3 ，N A3 ，N B3 ，N C3 )。
From the above, the embodiment of the invention introduces a carrier wave phase dislocation thought, adopts the phase difference of voltage doubling of the power frequency voltages of the phase A, the phase B and the phase C on the direct current side, and carries out voltage phase dislocation through the supporting capacitor on the low-voltage direct current side, thereby realizing lower direct current ripple on the high-voltage side and the low-voltage side. It can be understood that the power frequency input ac voltage of the three-phase power grid is 120 ° of the wrong phase, and the single-phase system forms a double frequency component on the DC side, so that a phase difference exists between the double frequency components of the three phases of the a phase, the B phase and the C phase, after being transformed by the isolated DC-DC converter, the double frequency fluctuation power is transferred to the low voltage DC side, and 3N double frequency, such as six times frequency component, is formed by utilizing the phase shift of the double frequency component of the three-phase power grid system, thereby reducing the DC ripple on the low voltage side, and the fluctuation power reduction on the low voltage side can be transferred to the high voltage side to further reduce the voltage ripple on the high voltage side.
It should be noted that, under the same voltage ripple index, the scheme of the invention can be realized by smaller capacitance values of the high-voltage side supporting capacitor and the low-voltage side supporting capacitor. In addition, by offset of double frequency ripple waves, the ripple voltage can be reduced by more than 65% in theory, the capacitance value of the supporting capacitor is strongly related to the amplitude value and the fluctuation size of the direct current voltage, the ripple voltage requirement is reduced, and the capacitance value of the capacitor can be synchronously reduced.
The low-voltage side series-parallel configuration scheme can reduce the complexity of a control link and improve the efficiency of the whole device; and voltage ripple can affect voltage equalizing and current harmonic level of the front-stage cascade four-quadrant network side, so that the friendliness of the device to the power grid is reduced. The voltage ripple also affects the realization of the later-stage isolated DC-DC soft switch, the DC-DC switching device can not realize soft switch (ZVS, ZCS, etc.), the loss of the system can be increased, the input power of the system part is lost in a heat form, and the energy utilization rate and the efficiency of the whole device are reduced.
By applying the three-phase distribution network type power electronic transformer and the configuration optimization method, the high-voltage side and low-voltage side supporting capacitance values are reduced by adopting the mode of the A-phase, B-phase and C-phase low-voltage direct current terminals in a series-parallel mode, so that the power density of the whole device is improved, the volume of the whole device is reduced, and the constraint pressure of an application scene on the volume of the device is reduced. In the prior art, a large capacity of supporting capacitor is needed to obtain the same voltage ripple range, so that the system volume, the cost and the power density are increased.
In addition, the small ripple voltage can be conveniently connected into other new energy sources and energy storage conversion devices, the problem that direct current voltage fluctuation under the parallel grid is large is not needed to be considered, and in the operation of a power grid system, particularly in the process of feeding back energy paths to the power grid, the electric energy quality of the whole device can be improved, and the friendliness of new energy sources and energy storage access is greatly improved. In addition, the mode of series-parallel connection of the low-voltage direct-current terminals of the phase A, the phase B and the phase C is adopted, a new hardware LC filter or other active frequency doubling control devices are not needed, the implementation is simple, and the operation is easy.
The three-phase power electronic transformer according to the embodiment of the present invention will be described below.
Further, the three-phase distribution network type power electronic transformer provided by the invention comprises: the high-voltage side cascade H-bridge module, the DC-DC bidirectional converter and the low-voltage side H-bridge module are alternately connected in series and then output to the bus through the collecting port;
the sink port includes: and collecting the R phase by a first port, the S phase by a second port and the T phase by a third port in links of the A phase, the B phase and the C phase of the low-voltage output side.
In one case, the three-phase distribution network type power electronic transformer comprises IGBT, IGCT, IPM or SiC MOSFETs.
In one case, the topology of the three-phase distribution network type power electronic transformer comprises: two-level, three-level, H-bridge cascade, chain, MMC version.
In one case, the three-phase distribution network type power electronic transformer is provided with a filter.
By utilizing the three-phase distribution network type power electronic transformer, the power frequency voltage low-voltage side supporting capacitor and the inductance of the phase A, the phase B and the phase C of the low-voltage output side are filtered, and voltage phase shifting is carried out through a preset control algorithm; and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1.
The capacity values of the high-voltage side supporting capacitor and the low-voltage side supporting capacitor are reduced by adopting a mode of series-parallel connection of the A-phase, B-phase and C-phase low-voltage direct current terminals, so that the power density of the whole device is improved, the volume of the whole device is reduced, and the constraint pressure of an application scene on the volume of the device is reduced. In addition, the small ripple voltage can be conveniently connected into other new energy sources and energy storage conversion devices, the problem that direct current voltage fluctuation under the parallel grid is large is not needed to be considered, and in the operation of a power grid system, particularly in the process of feeding back energy paths to the power grid, the electric energy quality of the whole device can be improved, and the friendliness of new energy sources and energy storage access is greatly improved. In addition, the mode of series-parallel connection of the low-voltage direct-current terminals of the phase A, the phase B and the phase C is adopted, a new hardware LC filter or other active frequency doubling control devices are not needed, the implementation is simple, and the operation is easy.
In order to verify the optimizing effect of the configuration optimizing method of the three-phase power electronic transformer, simulation analysis is performed, and the method specifically comprises the following steps:
simulation analysis: for the same system and control parameters, for full load simulation of the system shown in fig. 4 and 7, the high-voltage side and low-voltage side direct current, voltage and network side current waveforms of the three phases of the system under the same working condition are shown in fig. 9a to 9c and fig. 10a to 10c.
Comparison of simulation results: taking the high-voltage side direct-current voltage and the low-voltage side direct-current voltage of the A phase as examples, the high-voltage side direct-current voltage ripple and the low-voltage side direct-current voltage ripple in the ABC phase series-parallel mode provided by the application are respectively reduced by 75% and 78%, which indicates that the voltage ripple suppression effect of the scheme is obvious. The comparison data of the prior art with the present application scheme is shown in the following table:
although the embodiments of the present invention are disclosed above, the embodiments are only used for the convenience of understanding the present invention, and are not intended to limit the present invention. Any person skilled in the art can make any modification and variation in form and detail without departing from the spirit and scope of the present disclosure, but the scope of the present disclosure is still subject to the scope of the present disclosure as defined by the appended claims.
Claims (6)
1. The configuration optimization method of the three-phase distribution network type power electronic transformer is characterized by comprising the following steps of:
the power frequency voltages of the A phase, the B phase and the C phase of the low-voltage output side are filtered through a low-voltage side supporting capacitor and an inductor, and voltage phase shifting is performed through a preset control algorithm;
and (3) carrying out interphase parallel connection on the phase-shifted phase voltages, and then collecting the phase-shifted phase voltages to a bus to shift the frequency doubling components of the three-phase distribution network system into 3N frequency doubling components, wherein N is a natural number larger than 1.
2. The method for optimizing configuration of a three-phase distribution network type power electronic transformer according to claim 1, wherein the step of gathering the phase-shifted phase voltages into a bus after performing phase-to-phase series connection includes:
respectively converging a first port in a link of the phase A, the phase B and the phase C of the low-voltage output side to obtain a phase R, a second port to obtain a phase S and a third port to obtain a phase T;
and outputting the R phase, the S phase and the T phase to a bus.
3. A three-phase distribution network type power electronic transformer, comprising: the high-voltage side cascade H-bridge module, the DC-DC bidirectional converter and the low-voltage side H-bridge module are alternately connected in series and then output to the bus through the collecting port;
the sink port includes: and collecting the R phase by a first port, the S phase by a second port and the T phase by a third port in links of the A phase, the B phase and the C phase of the low-voltage output side.
4. A three-phase grid power electronic transformer according to claim 3, characterized in that the three-phase grid power electronic transformer comprises IGBT, IGCT, IPM or SiC MOSFETs.
5. A three-phase grid-type power electronic transformer according to claim 3, characterized in that the topology of the three-phase grid-type power electronic transformer comprises: two-level, three-level, H-bridge cascade, chain, MMC version.
6. A three-phase mains-distribution power electronic transformer according to claim 3, characterized in that the three-phase mains-distribution power electronic transformer is provided with a filter.
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