CN110783991A - Direct current charging system and control method thereof - Google Patents
Direct current charging system and control method thereof Download PDFInfo
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- CN110783991A CN110783991A CN201911093907.6A CN201911093907A CN110783991A CN 110783991 A CN110783991 A CN 110783991A CN 201911093907 A CN201911093907 A CN 201911093907A CN 110783991 A CN110783991 A CN 110783991A
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
- H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
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- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
Abstract
The invention provides a direct current charging system and a control method thereof, which are applied to the technical field of direct current power supply, the direct current charging system at least comprises a composite rectifier with a reactive compensation function, a plurality of DC/DC converters, at least one charging interface, a direct current bus and a system controller, wherein the input end of each composite rectifier is respectively connected with a power supply, the output end of each composite rectifier is respectively connected with the direct current bus, the input end of each DC/DC converter is connected with the direct current bus, the output end of each DC/DC converter is connected with the corresponding charging interface according to a preset corresponding relation, the system controller is at least used for controlling a target composite rectifier to provide reactive compensation current, the system provides reactive compensation current through the composite rectifier with the reactive compensation function, a reactive compensation device is not required to be independently arranged, compared with the prior art, the overall construction cost of, and the operation and maintenance task can be simplified, and the operation and maintenance cost is reduced.
Description
Technical Field
The invention relates to the technical field of direct current power supply, in particular to a direct current charging system and a control method thereof.
Background
One direct current charging station often is provided with many direct current and fills electric pile, fills electric pile through direct current and carries out quick charge for the object of charging. Each dc charging pile is generally formed by connecting a plurality of charging modules in parallel. At present, most of common charging modules are two-stage AC/DC charging modules, the front stage rectification part adopts an APFC (Active Power factor correction) circuit topology, and the rear stage isolation type DC/DC part adopts circuit topologies such as LLC (logical Link control) and phase-shifted full-bridge. In the operation process of the direct current charging station, reactive compensation needs to be carried out on the direct current charging station, so that efficient operation of related equipment such as a direct current charging pile in the direct current charging station is guaranteed, and meanwhile, the influence of the direct current charging station on the power factor of a public power grid connected with the direct current charging station is reduced.
In order to solve the reactive compensation problem of the dc charging station, a common method is to provide a reactive compensation device in the dc charging station, and output a reactive current through the reactive compensation device, for example, using a Static Var Generator (SVG) to perform reactive compensation on the dc charging station.
However, the use of a separate reactive power compensation device will undoubtedly increase the overall construction cost and operation and maintenance cost of the dc charging station.
Disclosure of Invention
The invention provides a direct current charging system and a control method thereof, which adopt a rectifier with a reactive compensation function to replace a common reactive compensation device, and have lower overall construction cost and operation and maintenance cost compared with a direct current charging station in the prior art.
In order to achieve the purpose, the technical scheme provided by the application is as follows:
in a first aspect, the present invention provides a dc charging system, comprising: at least one composite rectifier with reactive compensation function, a plurality of DC/DC converters, at least one charging interface, a direct current bus and a system controller,
the input end of each composite rectifier is connected with a power supply, and the output end of each composite rectifier is connected with the direct current bus;
the input end of each DC/DC converter is connected with the direct current bus, and the output end of each DC/DC converter is connected with the corresponding charging interface according to a preset corresponding relation;
the system controller is at least used for controlling the target composite rectifier to output reactive compensation current; wherein the target composite rectifier is one or more of the composite rectifiers.
Optionally, the number of composite rectifiers is less than the number of DC/DC converters.
Optionally, the dc charging system provided in the first aspect of the present invention further includes: a detection device, wherein,
the detection device is used for detecting the input current and the input voltage of the direct current charging system and sending the input current and the input voltage to the system controller;
and the system controller is used for controlling the target composite rectifier to output reactive compensation current according to the input current and the input voltage.
Optionally, the composite rectifier further has a harmonic current compensation function;
the system controller is further used for controlling the target composite type rectifier to output harmonic compensation current according to the input current.
Optionally, the dc charging system provided in the first aspect of the present invention further includes: a split transformer and at least one basic rectifier without reactive compensation function and harmonic current compensation function, wherein,
the input end of the split transformer is connected with the power supply, and at least one output end of the split transformer is connected with the power supply input end of each composite rectifier;
the other output ends of the split transformer are connected with the power input end of each basic rectifier;
and the output end of each basic rectifier is respectively connected with the direct current bus.
Optionally, the composite rectifier includes one of a two-level PWM rectifier, an I-type three-level PWM rectifier, a T-type three-level PWM rectifier, an ANPC three-level PWM rectifier, a flying capacitor type PWM rectifier, and a five-level diode clamp PWM rectifier.
Optionally, the basic rectifier includes one of a T-type VIENNA rectifier, an I-type VIENNA rectifier, and a diode rectifier.
Optionally, the system controller is further configured to obtain a reactive output instruction including a reactive compensation current value, and control the target composite rectifier to output a reactive compensation current according to the reactive output instruction.
In a second aspect, the present invention provides a method for controlling a dc charging system, which is applied to a system controller in the dc charging system according to any one of the first aspect of the present invention, and the method includes:
acquiring a reactive compensation current value of the direct current charging system;
determining a target composite rectifier according to a preset screening rule; wherein the target hybrid rectifier is one or more of the hybrid rectifiers of the DC charging system;
and controlling the target composite type rectifier to output reactive compensation current based on the reactive compensation current value.
Optionally, the obtaining of the reactive compensation current value of the dc charging system includes:
acquiring a reactive output instruction;
and analyzing the reactive output instruction to obtain a reactive compensation current value.
Optionally, if the dc charging system includes the detection device, the obtaining of the reactive compensation current value of the dc charging system includes:
obtaining an input current and an input voltage of the DC charging system
And calculating to obtain a reactive compensation current value of the direct current charging system according to the input current and the input voltage.
Optionally, the method for controlling a dc charging system according to any one of the second aspect of the present invention further includes:
calculating to obtain a harmonic compensation current value of the direct current charging system according to the input current;
and controlling the target composite type rectifier to output harmonic compensation current based on the harmonic compensation current value.
Optionally, the controlling the target composite rectifier to output the reactive compensation current based on the reactive compensation current value includes:
distributing the reactive compensation current values according to a first preset distribution rule to obtain reactive compensation current values corresponding to the target composite rectifiers;
and controlling each target composite type rectifier to output reactive compensation current according to the corresponding reactive compensation current value.
Optionally, the controlling the target composite rectifier to output a harmonic compensation current based on the harmonic compensation current value includes:
if the harmonic compensation current value is larger than a preset threshold value, distributing the reactive compensation current value according to a second preset distribution rule to obtain a harmonic compensation current value corresponding to each target composite rectifier;
and controlling each target composite rectifier to output harmonic compensation current according to the corresponding harmonic compensation current value.
Optionally, the method for controlling any dc charging system according to the second aspect of the present invention further includes:
and controlling each composite type rectifier and/or each basic type rectifier to output charging current.
The direct current charging system at least comprises a composite rectifier with a reactive compensation function, a plurality of DC/DC converters, at least one charging interface, a direct current bus and a system controller. The input end of each composite rectifier is connected with a power supply, the output end of each composite rectifier is connected with a direct current bus, the input end of each DC/DC converter is connected with the direct current bus, the output end of each DC/DC converter is connected with a corresponding charging interface according to a preset corresponding relation, and the system controller is used for controlling the target composite rectifier to output reactive compensation current.
According to the direct current charging system, the composite rectifier with the reactive compensation function provides reactive compensation current, a reactive compensation device does not need to be arranged independently, and compared with the prior art, the direct current charging system is low in overall construction cost, and meanwhile, operation and maintenance tasks can be simplified, and operation and maintenance cost can be reduced.
Furthermore, because a reactive power compensation device is not arranged independently, the construction land of the direct current charging system can be saved, and the construction cost is further reduced.
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, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a block diagram of a dc charging system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a T-type three-level rectifier according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an ANPC rectifier according to an embodiment of the present invention;
fig. 4 is a block diagram of another dc charging system according to an embodiment of the present invention;
fig. 5 is a block diagram of a dc charging system according to another embodiment of the present invention;
fig. 6 is a flowchart of a control method of a dc charging system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. 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 application.
Optionally, referring to fig. 1, fig. 1 is a block diagram of a dc charging system according to an embodiment of the present invention. The dc charging system provided in the embodiment of the present invention includes: the system comprises at least one hybrid rectifier 10, a direct current bus 20, a plurality of DC/DC converters 30, at least one charging interface 40, and a system controller 50. It should be noted that, in the embodiment shown in fig. 1, one composite rectifier 10, two DC/DC converters 30, and two charging interfaces 40 (charging interface 1 and charging interface 2) are shown, which only serve to simplify the illustration and facilitate description of the function of the DC charging system provided in the embodiment of the present invention, and are not intended to limit the number of the above components.
Specifically, as shown in fig. 1, the composite rectifier 10 has a power input end connected to a power supply 60 (shown by a solid line in the figure), and an output end connected to the dc bus 20, so as to converge the rectified dc current on the dc bus. It is conceivable that, when the dc charging system is provided with a plurality of composite rectifiers 10, the power input terminals of the composite rectifiers 10 may be connected to the power supply 60, the output terminals of the composite rectifiers 10 may be connected to the dc bus 20, and by providing the dc bus 20, the wiring difficulty of the system may be simplified, so that the wiring process is more convenient and neat, and the difficulty of the subsequent maintenance work may be reduced.
Further, the composite rectifier 10 selected in the embodiment of the present invention has a reactive compensation function, and can output a reactive compensation current according to a control instruction of the system controller 50. Of course, it is conceivable that the hybrid rectifier 10 has a charging current output function in addition to the reactive power compensation function, and can output a charging current when necessary.
Optionally, the composite rectifier 10 may be a T-type three-level rectifier as shown in fig. 2 or an ANPC rectifier as shown in fig. 3, or may be a two-level PWM rectifier, an I-type three-level PWM rectifier, a flying capacitor type PWM rectifier, or a five-level diode clamp PWM rectifier. The various types of rectifiers described above ensure that the hybrid rectifier 10 has a reactive compensation function.
As described above, the DC bus 20 is connected to the output terminal of the hybrid rectifier 10 to collect the DC current output from the hybrid rectifier 10, and the input terminal of the DC/DC converter 30 is connected to the DC bus 20 to receive the DC current output from the hybrid rectifier 10 through the DC bus 20. Meanwhile, the output end of each DC/DC converter 30 is connected to the corresponding charging interface 40 according to a preset correspondence relationship, and the charging interface 40 serves as a final output port of the charging current to charge the charging object when the charging object is connected thereto.
It should be noted that, in the example shown in fig. 1, each DC/DC converter 30 is connected to a corresponding charging interface 40, and in practical applications, a plurality of DC/DC converters 30 may be connected to the same charging interface 40 to meet the charging power requirement of the charging interface 40. Of course, the corresponding connection relationship between the DC/DC converter 30 and the charging interface 40 is determined at the beginning of the design of the DC charging system, and the specific connection condition between the DC/DC converter 30 and the charging interface 40 can be realized by referring to the implementation manner in the prior art, which is not limited in the present invention.
Optionally, the DC/DC converter 30 described in the embodiment of the present invention may select a power unidirectional isolation type DC/DC converter, and may also select a power bidirectional isolation type DC/DC converter.
The system controller 50 is configured to control the target composite rectifier 10 to output reactive compensation current to replace the function of the SVG device in the prior art, so as to implement reactive compensation on the connected power supply network. Further, it is also possible to integrate the charging current output control function into the system controller 50 provided in the embodiment of the present invention, that is, the system controller 50 controls the hybrid rectifier 10 to output the charging current according to the connection condition of the charging object.
In summary, the dc charging system provided in the embodiment of the present invention provides reactive compensation current through the composite rectifier having the reactive compensation function, and a reactive compensation device is not required to be separately provided.
Furthermore, because a reactive power compensation device which is independently arranged in the prior art is omitted, the construction land of the direct current charging system can be saved to a certain extent, and the construction cost is further reduced.
Optionally, the system controller may control the composite rectifier to output the reactive compensation current in two ways. Firstly, the system controller can control the reactive compensation current output by the composite rectifier according to an externally input control command. Specifically, the system controller can perform high-speed real-time communication with each composite rectifier, and after a reactive output instruction including a reactive compensation current value is obtained, the system controller sends the obtained reactive output instruction to the corresponding target composite rectifier through the high-speed real-time communication so as to control the corresponding target composite rectifier to output the reactive compensation current.
Secondly, a detection device is arranged in the direct current charging system, the input current and the input voltage of the direct current charging system are fed back to a system controller through the detection device, the system controller calculates the reactive compensation current value required to be output by the direct current charging system in real time according to the obtained input voltage and input current, and controls the output reactive compensation current of the target composite rectifier according to the reactive compensation current value.
Optionally, referring to fig. 4, fig. 4 is a block diagram of another dc charging station according to an embodiment of the present invention, and on the basis of the embodiment shown in fig. 1, the dc charging station further includes: the detection device 70 is configured to, among other things,
the detection device 70 is configured to detect an input current and an input voltage of the dc charging system, and transmit the detected input current and input voltage to the system controller 50. It is emphasized that the input current and input voltage, especially the input current, of the entire dc charging system, which are detected by the detecting device 70, cannot be the input current of some or part of the hybrid rectifier 10. As shown, the connection of the detection device 70 with the detection point preset by the dc charging system and the information transmission relationship with the system controller 50 are shown by dotted lines.
Alternatively, for the detection of the input current of the dc charging system, when the power supply 60 does not supply power to other load devices except the dc charging system, the output current of the power supply 60 may be directly detected, and the output current of the power supply 60 may be used as the input current of the dc charging system. Accordingly, the output voltage of the power supply 60 can be used as the input voltage of the dc charging system on the premise that the voltage drop generated from the power supply 60 to the dc charging system is within the allowable range. Of course, the detection point of the detection device 70 may be set in the dc charging system, so as to more accurately obtain the input current and the input voltage of the dc charging system. Any setting mode capable of accurately acquiring the input current and the input voltage of the direct current charging system is optional, and the setting mode also belongs to the protection scope of the invention on the premise of not exceeding the core thought scope of the invention.
The system controller 50 controls the target hybrid rectifier to output the reactive compensation current according to the input current and the input voltage of the dc charging system fed back by the detection device 70. That is, the system controller 50 calculates based on the input current and the input voltage fed back by the detection device 70 according to a preset algorithm, generates a control command corresponding to the current working condition of the dc charging system, and controls the target composite rectifier to output the reactive compensation current.
Further, the composite rectifier 10 may further have a harmonic current compensation function on the basis of having a reactive compensation function. In this case, the system controller 50 may also calculate a harmonic compensation current that the dc charging system needs to output, based on the input current of the dc charging system fed back by the detection device 70, and control the target hybrid rectifier 10 to output the harmonic compensation current, if necessary.
As a result, the target hybrid rectifier 10 can output the reactive compensation current, the harmonic compensation current, or both the reactive compensation current and the harmonic compensation current according to the control command of the system controller 50.
Of course, under the condition that the dc charging system does not need to output the reactive compensation current and the harmonic compensation current, the system controller 50 provided in the embodiment of the present invention may also control the target composite rectifier to stop outputting the reactive compensation current or the harmonic compensation current, or stop outputting the reactive compensation current and the harmonic compensation current at the same time.
It is conceivable that, due to the difference between the input current and the input voltage of the dc charging system, the reactive compensation current value and the harmonic compensation current value that the dc charging system needs to output are also different, and thus the number of the composite rectifiers that need to output the reactive compensation current and the harmonic compensation current changes, and therefore, in the case where the dc charging system is provided with a plurality of composite rectifiers, the target composite rectifier referred to in the present invention refers to one or more of all the composite rectifiers included in the dc charging system.
In the prior art, most of charging modules of the charging pile adopt two-stage AC/DC charging modules, namely a front-stage rectifier and a rear-stage DC/DC converter, and the front-stage rectifier and the rear-stage DC/DC converter are usually arranged in a one-to-one correspondence manner. The number of the rectifiers is reduced by arranging the high-power composite rectifier, so that auxiliary power supplies, driving circuits, power devices, structural parts and other related peripheral equipment used by the rectifiers can be greatly reduced, the overall construction cost of the direct-current charging system is further reduced, and meanwhile, the operation and maintenance cost can be reduced due to the reduction of the number of the rectifiers.
Optionally, in a practical application of the dc charging system, the reactive compensation capacity required to be provided by the whole dc charging system is relatively small, and therefore, when the dc charging system fully adopts the composite rectifier, such a design is obviously excessive, and based on this, another dc charging system is further provided in an embodiment of the present invention, referring to fig. 5, where fig. 5 is a structural block diagram of another dc charging system provided in an embodiment of the present invention, and on the basis of the embodiment shown in fig. 4, the dc charging system further includes: at least one basic rectifier 80 (only one is shown by way of example in fig. 2) without reactive compensation and harmonic current compensation functions, wherein,
the input terminals of the basic rectifiers 80 are connected to a power supply, and the output terminals are connected to the dc bus 20, respectively. The basic rectifier 80 functions to output a charging current according to a control command of the system controller 50 to charge the charging object connected to the charging interface.
Optionally, the basic rectifier 80 may be one of a T-type VIENNA rectifier, an I-type VIENNA rectifier, and a diode rectifier.
As shown in fig. 5, a split transformer 90 is also included in the embodiment of the present invention. The secondary side of the split transformer 90 is divided into at least two parts, each part can supply power for the connected load, the sum of the rated output power of each part is the total rated power of the split transformer, but the specific value of the rated power that each part in the secondary side can provide depends on the ampere-turn distribution of the split transformer in the design process. In an embodiment of the present invention, power is supplied to each type of rectifier in the dc charging system through a split transformer 90. Specifically, the input terminal of the split transformer 90 is connected to the power supply 60, at least one output terminal of the split transformer 90 is connected to the power supply input terminal of each composite rectifier 10, and the remaining output terminals of the split transformer 90 are connected to the power supply input terminal of the basic rectifier 80 in the dc charging system.
For example, the dc charging system has only one composite rectifier 10, one basic rectifier 80, and the split transformer 90 may be a double split transformer, where one secondary winding of the transformer is connected to the composite rectifier 10, and the other secondary winding is connected to the basic rectifier 80; for another example, if there are 2 composite rectifiers 10 and 2 basic rectifiers 80 in the dc charging system, one secondary winding of the double split transformer is connected to the 2 composite rectifiers 10, and the other secondary winding is connected to the 2 basic rectifiers 80; of course, in the case of arranging 2 composite rectifiers 10 and 2 basic rectifiers 80 in the dc charging system, a four-split transformer may be used, wherein 2 secondary windings are respectively connected to the composite rectifiers 10, and the other 2 secondary windings are respectively connected to the 2 basic rectifiers 80.
It should be noted that, in order to provide stability of power supply of each rectifier and power supply quality of the power supply, a transformer may also be disposed in the embodiment shown in fig. 1, and since the rectifiers disposed in the embodiment shown in fig. 1 are all composite rectifiers, the transformer in the dc charging system may be implemented by using a common dual-winding transformer.
Correspondingly, the output end of each rectifier is connected in parallel to the DC bus 20, and the input of each DC/DC converter is connected in parallel to the DC bus 20, so as to obtain electric energy through the DC bus. As for the connection relationship between the charging interface and each DC/DC converter, the connection relationship can be implemented with reference to the embodiment shown in fig. 1, and details thereof are omitted here.
With respect to the system controller 50, in an embodiment of the present invention, the system controller 50 may also be used to control the basic rectifier 80. When the charging target is connected to the corresponding charging interface, the basic rectifier 80 is controlled to output the charging current.
In the present embodiment, the basic function of the detection device 70 is not changed, but the input current and the input voltage of the dc charging system are still detected. In a specific connection relationship, the detection point of the detection device 70 may be disposed upstream of the split transformer 90, or may be disposed downstream of the split transformer 90, and any connection method capable of detecting the input current and the input voltage of the dc charging system is also optional.
In summary, the dc charging system provided in the embodiment of the present invention is provided with the composite rectifier and the basic rectifier, so that the requirements of the dc charging system for performing reactive current compensation and harmonic current compensation are met by the composite rectifier, and meanwhile, the requirements of the dc charging system for outputting active power for charging a charging object are met by the composite rectifier and the basic rectifier in a matching manner. Compared with the embodiment, the number of the composite rectifiers is reduced, and the construction cost of the direct current charging system can be further reduced.
In practical applications, the reactive compensation capacity required by a dc charging system is relatively limited and can be estimated by existing algorithms, for example, the reactive compensation capacity is required to provide 10% of the total capacity of the dc charging system. Therefore, the setting quantity of the composite rectifier and the basic rectifier can be matched according to the proportion of the reactive compensation capacity to the active capacity of the direct-current charging system, so that the overall construction cost of the direct-current charging system and the later operation and maintenance cost are further reduced while the basic reactive compensation capacity is met.
It should be noted that, in any of the above embodiments, regardless of the hybrid rectifier or the basic rectifier, it is possible to output a corresponding charging current only when a charging target is connected to the charging interface, and it is not possible to output a charging current when no charging target is connected. However, for the composite rectifier, even if the charging interface is not connected with a charging object, the system controller can control the composite rectifier to output corresponding reactive compensation current and harmonic compensation current or simultaneously output the reactive compensation current and the harmonic compensation current according to needs.
A control method of the dc charging system according to an embodiment of the present invention is described below, and the control method of the dc charging system according to the embodiment of the present invention is applied to a system controller of the dc charging system according to any one of the embodiments described above.
Optionally, referring to fig. 6, fig. 6 is a flowchart of a control method of a dc charging system according to an embodiment of the present invention, where the flowchart may include:
and S100, obtaining a reactive compensation current value of the direct current charging system.
In order to realize control of the composite rectifier, a system controller of the direct current charging system first needs to obtain a reactive compensation current value to be output by the direct current charging system.
Optionally, the system controller may receive an external reactive output instruction, where the reactive output instruction includes a reactive compensation current value of the dc charging station, and after receiving the reactive output instruction, the system controller analyzes the reactive output instruction to obtain the reactive compensation current value included therein.
Optionally, if the dc charging system is provided with the detection device, the system controller is connected to the detection device of the dc charging system, the input current and the input voltage of the dc charging system are obtained through the detection device, and after the input current and the input voltage of the dc charging system are obtained, the reactive compensation current value required to be provided by the dc charging system can be calculated according to the obtained input current and the obtained input voltage. It is conceivable that the reactive compensation current value calculated here is relative to the dc charging system, and the reactive compensation current for a specific output of each composite rectifier needs to be further determined in a subsequent step.
As described above, if the hybrid charging pile in the dc charging station further has a harmonic current compensation function, the system controller further needs to calculate a harmonic compensation current value that needs to be output by the dc charging system according to a preset algorithm. Specifically, in the process of calculating the reactive compensation current value of the direct current charging system, the input current and the input voltage of the direct current charging system need to be combined, and the harmonic compensation current value of the direct current charging system can be calculated only by combining the input current of the direct current charging system. As for the specific calculation process of the reactive compensation current and the harmonic compensation current, the calculation process can be realized by referring to the calculation method in the prior art, the calculation method is not specifically limited in this respect, and any calculation method in the prior art that can calculate the reactive compensation current value and the harmonic compensation current value of the direct current charging system according to the input current and the input voltage of the direct current charging system is also optional.
As for the data transmission mode and the data transmission process between the system controller and the detection device, the implementation mode in the prior art can be referred to, and the present invention is not particularly limited to this.
And S110, determining a target composite rectifier according to a preset screening rule.
The composite rectifier mentioned in the embodiment of the invention is one or more of all composite rectifiers of a direct current charging system.
Alternatively, there may be a variety of ways to select the target composite rectifier. For example, the historical time lengths of the reactive compensation currents output by each composite rectifier or the harmonic compensation currents output by each composite rectifier can be counted, the composite rectifiers are sorted according to the historical time lengths, and then the composite rectifiers are selected as the target composite rectifiers according to the sequence of the historical time lengths from short to long.
Or setting corresponding state marks for each composite rectifier, marking the state of each composite rectifier, and screening the composite rectifiers which do not output reactive compensation current or harmonic compensation current as target composite rectifiers according to the state marks of the composite rectifiers. And after all the composite rectifiers in the direct current charging system output reactive compensation current or harmonic compensation current, updating the state identifications of all the composite rectifiers in the direct current charging system so as to select the composite rectifiers next time.
Optionally, for the condition that the system controller controls the composite charging pile to output the reactive compensation current according to the received reactive output instruction, more control information can be added to the reactive output instruction. For example, a composite rectifier that specifically executes the reactive output instruction may be specified, and after obtaining the reactive output instruction of this type, the system controller may directly control the corresponding composite rectifier to output the reactive compensation current according to the obtained reactive output instruction without determining the target composite rectifier according to the preset screening rule.
It is conceivable that no matter what kind of preset screening rule is adopted to screen the target composite rectifier, a precondition must be satisfied, that is, the selected target composite rectifier can output the reactive compensation current and the harmonic compensation current of the dc charging system calculated in S100, and an overload phenomenon does not occur.
Further, the reactive output instruction may further specify a reactive current value specifically output by each target composite rectifier, and the like.
It should be noted that other ways of obtaining the target composite rectifier through screening are also optional, and the other ways also belong to the protection scope of the present invention without departing from the scope of the core idea of the present invention.
And S120, controlling the target composite rectifier to output reactive compensation current based on the reactive compensation current value.
After determining the reactive compensation current and the target composite rectifier which need to be output by the direct current charging system, firstly, distributing the obtained reactive compensation current value according to a first preset distribution rule to obtain the reactive compensation current value corresponding to each target composite rectifier.
Optionally, as the simplest distribution mode, the reactive compensation current value required to be output by the direct current charging system may be evenly distributed to each target composite rectifier; and the reactive compensation current value required to be output by the direct current charging system can be proportionally distributed to each target composite rectifier according to a preset distribution proportion. Of course, the allocation may be performed in other allocation manners, and the allocation is also within the protection scope of the present invention without departing from the scope of the core idea of the present invention.
After the reactive compensation current value corresponding to each target composite rectifier is determined, each target composite rectifier can be controlled to output reactive compensation current according to the corresponding reactive compensation current value.
In summary, the control method for the dc charging system according to the embodiment of the present invention controls the dc charging system with the composite rectifier, so that the composite rectifier can provide the reactive compensation current without separately providing a reactive compensation device, thereby simplifying the operation and maintenance task and reducing the operation and maintenance cost.
Optionally, for the harmonic compensation current, after the harmonic compensation current value of the dc charging system is obtained through calculation, it is first determined whether the harmonic compensation current value is greater than a preset threshold, for example, 5% of the total current, if the harmonic compensation current value of the dc charging system is greater than the preset threshold, similar to the reactive current compensation mode, the harmonic compensation current value obtained through calculation needs to be distributed according to a second preset distribution rule, so as to obtain a harmonic compensation current value corresponding to each target composite rectifier, and then each target composite rectifier is controlled to output the harmonic compensation current according to the corresponding harmonic compensation current value.
Optionally, for the second preset allocation rule, the same allocation manner as the first preset allocation rule may be selected, and of course, an allocation manner different from the first preset allocation rule may also be selected.
Correspondingly, if the calculated harmonic compensation current value is smaller than or equal to the preset threshold value, the harmonic current compensation can be temporarily not performed, and the system controller directly prohibits each target composite rectifier from outputting the harmonic compensation current.
Of course, for the composite type rectifier that is not selected as the target composite type rectifier, the reactive compensation current and the harmonic compensation current are not output.
According to the above control process, it can be seen that, according to the difference between the calculated reactive compensation current value and the harmonic compensation current value, the working state of the composite rectifier at least includes: the method comprises the steps of outputting reactive compensation current, outputting harmonic compensation current, simultaneously outputting reactive compensation current and harmonic compensation current, forbidding to output reactive compensation current and harmonic compensation current, and the like.
Further, the control method provided in the embodiment of the present invention may specify one or more target composite rectifiers to perform corresponding functions when controlling the dc charging system to perform reactive current compensation and harmonic current compensation, so that when the number of charging interfaces actually connected to a charging object in the dc charging system decreases, reactive compensation current and harmonic compensation current that need to be output by the dc charging system may be decreased. Certainly, because the number of the composite rectifiers in the dc charging system is small, when the output of the reactive compensation current and the harmonic compensation current is specifically stopped, the output requirement is considered, and the specific number of the composite rectifiers is also considered comprehensively, so that the current reactive compensation requirement or the harmonic current compensation requirement of the dc charging system cannot be met after a certain composite rectifier is turned off.
Optionally, if a basic rectifier is disposed in the dc charging system, the control method provided in the embodiment of the present invention may further control the composite rectifier and the basic rectifier according to a specific situation that the dc charging system is connected to a charging object, or simultaneously control the composite rectifier and the basic rectifier to charge the charging object, that is, output the charging current.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (15)
1. A dc charging system, comprising: at least one composite rectifier with reactive compensation function, a plurality of DC/DC converters, at least one charging interface, a direct current bus and a system controller,
the input end of each composite rectifier is connected with a power supply, and the output end of each composite rectifier is connected with the direct current bus;
the input end of each DC/DC converter is connected with the direct current bus, and the output end of each DC/DC converter is connected with the corresponding charging interface according to a preset corresponding relation;
the system controller is at least used for controlling the target composite rectifier to output reactive compensation current; wherein the target composite rectifier is one or more of the composite rectifiers.
2. The direct current charging system according to claim 1, wherein the number of the hybrid rectifiers is less than the number of the DC/DC converters.
3. The dc charging system of claim 1, further comprising: a detection device, wherein,
the detection device is used for detecting the input current and the input voltage of the direct current charging system and sending the input current and the input voltage to the system controller;
and the system controller is used for controlling the target composite rectifier to output reactive compensation current according to the input current and the input voltage.
4. The dc charging system of claim 3, wherein the hybrid rectifier further has a harmonic current compensation function;
the system controller is further used for controlling the target composite type rectifier to output harmonic compensation current according to the input current.
5. The dc charging system of claim 1, further comprising: a split transformer and at least one basic rectifier without reactive compensation function and harmonic current compensation function, wherein,
the input end of the split transformer is connected with the power supply, and at least one output end of the split transformer is connected with the power supply input end of each composite rectifier;
the other output ends of the split transformer are connected with the power input end of each basic rectifier;
and the output end of each basic rectifier is respectively connected with the direct current bus.
6. The dc charging system of claim 1, wherein the hybrid rectifier comprises one of a two-level PWM rectifier, an I-type three-level PWM rectifier, a T-type three-level PWM rectifier, an ANPC three-level PWM rectifier, a flying capacitor type PWM rectifier, and a five-level diode-clamped PWM rectifier.
7. The DC charging system of claim 5, wherein the base rectifier comprises one of a T-VIENNA rectifier, an I-VIENNA rectifier, and a diode rectifier.
8. The dc charging system of any of claims 1-7, wherein the system controller is further configured to obtain a reactive output command including a reactive compensation current value, and to control the target composite rectifier to output a reactive compensation current according to the reactive output command.
9. A method for controlling a dc charging system, the method being applied to a system controller in the dc charging system according to any one of claims 1 to 8, the method comprising:
acquiring a reactive compensation current value of the direct current charging system;
determining a target composite rectifier according to a preset screening rule; wherein the target hybrid rectifier is one or more of the hybrid rectifiers of the DC charging system;
and controlling the target composite type rectifier to output reactive compensation current based on the reactive compensation current value.
10. The method according to claim 9, wherein the obtaining the reactive compensation current value of the dc charging system comprises:
acquiring a reactive output instruction;
and analyzing the reactive output instruction to obtain a reactive compensation current value.
11. The method according to claim 9, wherein if the dc charging system includes a detection device, the obtaining the reactive compensation current value of the dc charging system includes:
obtaining an input current and an input voltage of the DC charging system
And calculating to obtain a reactive compensation current value of the direct current charging system according to the input current and the input voltage.
12. The method of controlling a dc charging system according to claim 11, further comprising:
calculating to obtain a harmonic compensation current value of the direct current charging system according to the input current;
and controlling the target composite type rectifier to output harmonic compensation current based on the harmonic compensation current value.
13. The method of controlling a dc charging system according to claim 9, wherein the controlling the target hybrid rectifier to output a reactive compensation current based on the reactive compensation current value includes:
distributing the reactive compensation current values according to a first preset distribution rule to obtain reactive compensation current values corresponding to the target composite rectifiers;
and controlling each target composite type rectifier to output reactive compensation current according to the corresponding reactive compensation current value.
14. The method of controlling a dc charging system according to claim 12, wherein the controlling the target hybrid rectifier to output a harmonic compensation current based on the harmonic compensation current value comprises:
if the harmonic compensation current value is larger than a preset threshold value, distributing the reactive compensation current value according to a second preset distribution rule to obtain a harmonic compensation current value corresponding to each target composite rectifier;
and controlling each target composite rectifier to output harmonic compensation current according to the corresponding harmonic compensation current value.
15. The method for controlling a dc charging system according to any one of claims 9 to 14, further comprising:
and controlling each composite type rectifier and/or each basic type rectifier to output charging current.
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