CN111130198A - Charging system and method for electric automobile - Google Patents
Charging system and method for electric automobile Download PDFInfo
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- CN111130198A CN111130198A CN202010001692.7A CN202010001692A CN111130198A CN 111130198 A CN111130198 A CN 111130198A CN 202010001692 A CN202010001692 A CN 202010001692A CN 111130198 A CN111130198 A CN 111130198A
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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
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
- H02J7/04—Regulation of charging current or voltage
- H02J7/06—Regulation of charging current or voltage using discharge tubes or semiconductor devices
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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
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/2173—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a biphase or polyphase circuit arrangement
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
Abstract
The application discloses charging system and method of electric automobile, including: the input end of the isolated AC-DC converter is connected with a power grid, and the output end of the isolated AC-DC converter is connected with a direct current bus; the isolated AC-DC converter rectifies alternating current into direct current before the electric automobile is charged, and does not work when the electric automobile is charged; when the isolated AC-DC converter works, the insulation monitoring circuit monitors the insulation resistance to the ground of the direct current bus; the input end of the non-isolated AC-DC charging module is connected with a power grid, and the output end of the non-isolated AC-DC charging module is connected with the input end of the direct current bus; the non-isolated AC-DC charging module works when the electric automobile is charged to rectify alternating current provided by a power grid into direct current; and when the electric automobile is not charged, the connection with the power grid is disconnected. Can carry out insulation monitoring before charging, improve charge efficiency, reduce cost.
Description
Technical Field
The application relates to the technical field of power electronics, in particular to a charging system and method of an electric automobile.
Background
High-power direct current charging is the first choice for fast charging of electric vehicles. Currently, a high-power dc charging pile usually includes a plurality of charging modules connected in parallel. For example, a 120kW dc charging post may include 6 parallel 20kW charging modules.
In the prior art, a charging module is generally divided into a high-frequency isolation type and a power-frequency isolation type, and the charging module is most widely applied to the high-frequency isolation type. The following describes the high-frequency isolation type and power-frequency isolation type charging modules, respectively.
High-frequency isolation type charging module: the front stage adopts an APFC (active Power Factor correction) topology, and the rear stage adopts a high-frequency isolation DC-DC converter.
Power frequency isolated form charging module: the power frequency transformer is connected with the APFC topology at the front stage, and the non-isolated DC-DC converter is arranged at the rear stage.
The two isolation modes meet the 7.5.5 electrical isolation requirement in NB/T33001-2018 and the online insulation monitoring requirement in GB/T18487.1-2015 energy transmission process, and fully consider the safety problem when the direct current charging pile charges the electric automobile.
The above standards require insulation monitoring both before and during charging. Isolation is required for insulation monitoring. However, whether high-frequency isolation or power-frequency isolation is adopted, the isolated charging module has the defects of low charging efficiency and high cost.
Disclosure of Invention
The application provides a charging system and a charging method for an electric automobile, which can perform insulation monitoring before charging, improve charging efficiency and reduce the cost of the whole charging system.
The embodiment of the invention provides a charging system of an electric automobile, which comprises: the device comprises a non-isolated AC-DC charging module, an isolated AC-DC converter and an insulation monitoring circuit;
the input end of the isolated AC-DC converter is connected with a power grid, and the output end of the isolated AC-DC converter is connected with a direct current bus;
the isolated AC-DC converter is used for rectifying alternating current provided by the power grid into direct current before the electric automobile is charged and does not work when the electric automobile is charged;
the insulation monitoring circuit is used for monitoring the insulation resistance to the ground of the direct current bus when the isolated AC-DC converter works;
the input end of the non-isolated AC-DC charging module is connected with the power grid, and the output end of the non-isolated AC-DC charging module is connected with the input end of the direct current bus;
the non-isolated AC-DC charging module is used for rectifying alternating current provided by the power grid into direct current when the electric automobile is charged; and when the electric automobile is not charged, the connection with the power grid is disconnected.
Preferably, the method further comprises the following steps: a controller and a controllable switch;
the input end of the non-isolated AC-DC charging module is connected with the power grid through the controllable switch;
the controller is used for controlling the controllable switch to be switched off when the electric automobile is not charged; and when the electric automobile is charged, controlling the controllable switch to be closed.
Preferably, the non-isolated AC-DC charging module comprises any one of:
the system comprises a VIENNA rectifier-based non-isolated AC/DC charging module, a two-level PWM rectifier-based non-isolated AC/DC charging module, a T-type three-level rectifier-based non-isolated AC/DC charging module, an I-type NPC rectifier-based non-isolated AC/DC charging module, an ANPC rectifier-based non-isolated AC/DC charging module and a flying capacitor rectifier-based non-isolated AC/DC charging module.
Preferably, the output terminal of the non-isolated AC-DC charging module further comprises any one of the following DC-DC converters:
buck, boost, and buck-boost.
Preferably, the isolated AC-DC converter comprises any one of:
the converter comprises a front-stage diode uncontrolled rectifying and post-stage flyback converter, a front-stage diode uncontrolled rectifying and post-stage push-pull converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting full-bridge converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage flyback converter, a front-stage APFC plus post-stage push-pull converter, a front-stage APFC plus post-stage forward converter, a front-stage APFC plus post-stage phase-shifting full-bridge converter, a front-stage APFC plus post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage LLC converter and a front-stage diode uncontrolled rectifying and post-stage forward converter.
Preferably, the maximum power of the isolated AC-DC converter is less than the maximum power of the non-isolated AC-DC charging module.
Preferably, the non-isolated AC-DC charging module comprises at least two of: a first non-isolated AC-DC charging module and a second non-isolated AC-DC charging module;
the first and second non-isolated AC-DC charging modules are connected in parallel with each other.
Preferably, the controller is further configured to control the isolated AC-DC converter to charge the DC bus to a preset threshold voltage when the insulation is determined to be normal by the insulation resistance detected by the insulation monitoring circuit, and then control the isolated AC-DC converter to stop working, so as to control the controllable switch to be turned on.
The embodiment of the application also provides a charging control method of the electric automobile, which is applied to the system; the method comprises the following steps:
before charging, the non-isolated AC-DC charging module is controlled to be disconnected with a power grid, the isolated AC-DC converter is controlled to rectify alternating current provided by the power grid into direct current, and the insulation monitoring circuit is controlled to monitor the insulation resistance to the ground of a direct current bus;
and when the insulation monitoring is finished and the insulation is normal, controlling the isolated AC-DC converter to stop working, controlling the input end of the non-isolated AC-DC charging module to be connected with a power grid, and controlling the non-isolated AC-DC charging module to charge the electric automobile.
Preferably, before the controlling the isolated AC-DC converter to stop operating, the method further includes:
and controlling the isolated AC-DC converter to charge the direct-current bus to a preset threshold voltage, controlling a controllable switch to be closed, and connecting the input end of the non-isolated AC-DC charging module with the power grid through the controllable switch.
According to the technical scheme, the method has the following advantages that:
since the european standard only requires insulation monitoring of the charging system before charging, and insulation monitoring is not required during charging, before charging, the embodiment of the present application operates with an isolated AC-DC converter for isolation, and at this time, the non-isolated AC-DC charging module is disconnected from the power grid at both physical and electrical levels. After the insulation monitoring is finished, the isolated AC-DC converter quits working, the non-isolated AC-DC charging module is connected with the power grid, and the non-isolated AC-DC charging module performs electric energy conversion to charge the electric automobile. Because the isolated AC-DC converter is only used for insulation monitoring before charging, the power of the isolated AC-DC converter can be small, and the isolated AC-DC converter is small in size and low in cost. The AC-DC converter is bulky and costly due to the bulky isolation devices. The non-isolated AC-DC charging module is non-isolated, one-stage isolation is omitted, charging efficiency can be improved, the size is small, and cost is low.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be 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 described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of a charging system of an electric vehicle according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of another charging system for an electric vehicle according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a non-isolated AC/DC charging module of a T-type three-level rectifier provided herein;
FIG. 4 is a schematic diagram of a non-isolated AC/DC charging module of an ANPC rectifier according to an embodiment of the present application;
fig. 5 is a schematic diagram of a charging system of another electric vehicle according to an embodiment of the present disclosure;
fig. 6 is a flowchart of a charging control method for an electric vehicle according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions provided by the present application better understood by those skilled in the art, the charging standard of electric vehicles in europe is described below. IEC 68151-23-2014 specifies that insulation monitoring of the positive direct current bus and the negative direct current bus on the charging direct current side to the ground is only required before charging, and insulation monitoring is not required in the charging process of the electric vehicle, namely in the energy transmission process. This standard is thought to confirm before electric automobile charges that to fill electric pile body reliable ground connection and actual insulation level accord with the standard, just can ensure safety, and the safety in the charging process can be guaranteed by the rifle that charges. Therefore, this standard considers that a non-isolated scheme may be adopted at the time of charging as long as the scheme can confirm that there is no problem with the charging system insulation before charging.
Therefore, the technical scheme provided by the embodiment of the application is based on the above standard regulation, insulation monitoring is carried out before charging, and insulation monitoring is not carried out in the charging process. However, during insulation monitoring, the power grid needs to be isolated from the direct current side, so before charging, the embodiment of the application adopts the isolated AC-DC converter to work for isolation, and at this time, the non-isolated AC-DC charging module is disconnected from the power grid at both physical and electrical levels. After the insulation monitoring is finished, the isolated AC-DC converter quits working, the non-isolated AC-DC charging module is connected with the power grid, and the non-isolated AC-DC charging module performs electric energy conversion to charge the electric automobile. Because the isolated AC-DC converter is only used for insulation monitoring before charging, the power of the isolated AC-DC converter can be small, and the isolated AC-DC converter is small in size and low in cost. The AC-DC converter is bulky and costly due to the bulky isolation devices. The non-isolated AC-DC charging module is non-isolated, one-level isolation is omitted, charging efficiency is high, the size is small, and cost is low.
In order to make the technical solutions of the present application better understood, 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.
It should be understood that the terms "first", "second", "third", and "fourth" in the embodiments of the present application are for convenience of description only, and do not limit the present application.
The embodiment of the system is as follows:
referring to fig. 1, the figure is a schematic view of a charging system of an electric vehicle according to an embodiment of the present application.
The charging system of electric automobile that this embodiment provided includes: a non-isolated AC-DC charging module 100, an isolated AC-DC converter 200, and an insulation monitoring circuit 300;
the input end of the isolated AC-DC converter 200 is connected with a power grid, and the output end of the isolated AC-DC converter 200 is connected with a direct current bus;
the isolated AC-DC converter 200 is used for rectifying the alternating current provided by the power grid into direct current before the electric vehicle is charged, and does not work when the electric vehicle is charged;
the isolated AC-DC converter 200 is used to rectify AC power from the grid into DC power and supply the DC power to the DC bus when monitoring the DC side insulation before charging.
The insulation monitoring circuit is used for monitoring the insulation resistance to the ground of the direct current bus when the isolated AC-DC converter 200 works;
since the isolation monitoring requires isolation between the DC side and the AC side, isolation in the isolation monitoring process is achieved by the isolated AC-DC converter 200.
The input end of the non-isolated AC-DC charging module 100 is connected with the power grid, and the output end of the non-isolated AC-DC charging module 100 is connected with the input end of the direct current bus;
the non-isolated AC-DC charging module 100 is configured to rectify an alternating current provided by the power grid into a direct current when the electric vehicle is charged; and when the electric automobile is charged or not charged, the connection with the power grid is disconnected.
During insulation monitoring, the input end of the non-isolated AC-DC charging module 100 cannot be connected to a power grid, otherwise, insulation monitoring cannot be completed, so that during insulation monitoring, the input end of the non-isolated AC-DC charging module 100 needs to be disconnected from the power grid, and after insulation monitoring is completed, the input end of the non-isolated AC-DC charging module 100 is connected to the power grid during charging.
Since the isolated AC-DC converter 200 operates only during insulation monitoring before charging, the isolated AC-DC converter 200 only needs to provide power at which the insulation monitoring can operate normally, and the power may be small, for example, 1 kW. The maximum power of the isolated AC-DC converter 200 is less than the maximum power of the non-isolated AC-DC charging module 100. The non-isolated AC-DC charging module 100 needs to operate during charging of the electric vehicle to provide charging power, so the power of the non-isolated AC-DC charging module 100 is relatively high, generally, the power of the non-isolated AC-DC charging module 100 may be several tens of times that of the isolated AC-DC converter, for example, the maximum power of the non-isolated AC-DC charging module is more than 20 times that of the isolated AC-DC converter. Specifically, when the power of the isolated AC-DC converter 200 is 1kW, the power of the non-isolated AC-DC charging module 100 may be 20kW, 60kW, or 100 kW.
According to the technical scheme provided by the embodiment of the application, the main power conversion module, namely the non-isolated AC-DC charging module 100, used only during charging is non-isolated, and the small power module, used only during insulation monitoring before charging, is isolated, and the two modules are added together and have smaller volume than an isolated rectifying module in the prior art. The framework provided by the application has small volume and low cost, meets the European standard of insulation monitoring before charging, and can ensure normal charging. Because the charging system that this application provided, in the charging process, what utilized is that the non-isolated rectifier module of charging, has lacked the one-level isolation, consequently, can improve the conversion efficiency of electric energy, make charge efficiency higher. In the process of electric energy conversion, the more the stages are, the lower the efficiency is, and each stage can waste certain electric energy.
In order to better complete the insulation monitoring, it is necessary that the non-isolated AC-DC charging module is disconnected from the grid during the insulation monitoring, and therefore, the system may further include: a controllable switch 400 and a controller 500; as shown in fig. 2.
The input of the non-isolated AC-DC charging module 100 is connected to the grid through the controllable switch 400;
the controller 500 is configured to control the controllable switch 400 to be turned off when the electric vehicle is not charging, so as to disconnect the non-isolated AC-DC charging module 100 from the power grid; when the electric vehicle is charged, the controllable switch 400 is controlled to be closed, so as to connect the non-isolated AC-DC charging module 100 with the power grid.
The specific type and implementation manner of the controllable switch 400 are not particularly limited in the embodiment of the present application, and the controllable switch 400 may include one switch or a plurality of switches as long as the opening and closing functions can be implemented. For example, the controllable switch 400 may be a relay, a breaker, a contactor, an IGBT, a MOS, or the like.
In this embodiment, a specific topology adopted by the non-isolated AC-DC charging module is not limited, and may be implemented by using a relatively mature non-isolated rectifier.
For example, the non-isolated AC-DC charging module may include any one of:
the system comprises a VIENNA rectifier-based non-isolated AC/DC charging module, a two-level PWM rectifier-based non-isolated AC/DC charging module, a T-type three-level rectifier-based non-isolated AC/DC charging module, an I-type NPC rectifier-based non-isolated AC/DC charging module, an ANPC rectifier-based non-isolated AC/DC charging module and a flying capacitor rectifier-based non-isolated AC/DC charging module.
Specifically, reference may be made to fig. 3, which is a schematic diagram of a non-isolated AC-DC charging module of a T-type three-level rectifier provided in the present application.
As can be seen from fig. 3, the rectifier is a three-phase rectifier, and includes 12 switching tubes, Ta1-T a 4; tb1-Tb4 and Tc1-Tc 4.
In addition, reference may be made to fig. 4, which is a schematic diagram of a non-isolated AC-DC charging module of an ANPC rectifier provided in the present application.
As can be seen from fig. 4, the rectifier is a three-phase rectifier, each phase includes an upper bridge arm and a lower bridge arm, the upper bridge arm includes three switching tubes, and the lower bridge arm includes three switching tubes.
Since the application of the T-type three-level rectifier and the ANPC rectifier is mature, the detailed working principle thereof is not described herein again.
The non-isolated AC-DC charging module can comprise two stages, wherein the first stage is an AC-DC module, the second stage is a DC-DC converter, and the second stage is connected in series with the output end of the first stage;
for example, the output terminal of the non-isolated AC-DC charging module further includes any one of the following DC-DC converters:
buck, boost, and buck-boost.
The DC-DC converter included in the non-isolated AC-DC charging module is not specifically limited in this embodiment, and one skilled in the art may select one DC-DC converter according to actual needs.
The isolated AC-DC converter is not particularly limited in this embodiment, for example, any one of the following may be adopted for the isolated AC-DC converter:
the converter comprises a front-stage diode uncontrolled rectifying and post-stage flyback converter, a front-stage diode uncontrolled rectifying and post-stage push-pull converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting full-bridge converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage flyback converter, a front-stage APFC plus post-stage push-pull converter, a front-stage APFC plus post-stage forward converter, a front-stage APFC plus post-stage phase-shifting full-bridge converter, a front-stage APFC plus post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage LLC converter and a front-stage diode uncontrolled rectifying and post-stage forward converter.
The preceding stage and the subsequent stage are front and rear two-stage DC-DC converters, and the preceding stage DC-DC converter and the subsequent stage DC-DC converter are connected in series.
After the insulation monitoring is completed, in order to prevent too large current impact from being caused to the non-isolated AC-DC charging module when the non-isolated AC-DC charging module is connected to the power grid, after the insulation monitoring is completed, the isolated AC-DC converter is used for charging the DC bus, when the DC bus voltage at the DC side is recharged to the preset threshold voltage, the isolated AC-DC converter is controlled to stop working, and the controllable switch is controlled to be closed, so that the non-isolated AC-DC charging module is connected to the power grid. At this time, the voltage difference between the input end and the output end of the non-isolated AC-DC charging module is not too large, so that the internal switching tube, the capacitance, the inductance and other electrical elements cannot be damaged, the devices are protected, and the service life of the devices is prolonged.
It should be noted that, after the non-isolated AC-DC charging module is connected to the power grid, the isolated AC-DC converter stops working, but the isolated AC-DC converter may not be disconnected from the power grid.
In this embodiment, the preset threshold voltage is not specifically limited, and the threshold voltage is set, so that the purpose of protecting the electrical elements of the non-isolated AC-DC charging module can be achieved. For example, for a single-phase power grid system, the preset threshold voltage may be a voltage peak value of the phase voltage; for a three-phase grid system, the preset threshold voltage may be a voltage peak of the line voltage.
The number of the non-isolated AC-DC charging modules provided in the above embodiments may be one, or may be multiple, and when the number of the non-isolated AC-DC charging modules is multiple, the multiple non-isolated AC-DC charging modules are connected in parallel, so as to increase the output power and increase the charging power. The following description will take the case where the non-isolated AC-DC charging module includes two modules.
Referring to fig. 5, the figure is a schematic view of a charging system of another electric vehicle according to an embodiment of the present application.
The non-isolated AC-DC charging module includes at least two of: a first non-isolated AC-DC charging module 100a and a second non-isolated AC-DC charging module 100 b;
the first and second non-isolated AC- DC charging modules 100a and 100b are connected in parallel with each other. As shown in the figure, the input terminal of the first non-isolated AC-DC charging module 100a and the input terminal of the second non-isolated AC-DC charging module 100b are connected together and are connected to the power grid through the controllable switch 400, and it can be understood that the first non-isolated AC-DC charging module 100a and the second non-isolated AC-DC charging module 100b may share one controllable switch or may respectively correspond to one controllable switch, and are connected to the power grid through their corresponding controllable switches, but two controllable switches are required to act simultaneously. The output of the first non-isolated AC-DC charging module 100a and the output of the second non-isolated AC-DC charging module 100b are connected together and both connected to the DC side.
Based on the charging system of the electric automobile provided by the embodiment, the embodiment of the application further provides a charging control method of the electric automobile.
Referring to fig. 6, the flowchart is a flowchart of a charging control method for an electric vehicle according to an embodiment of the present application.
The charging control method of the electric vehicle provided by the embodiment is applied to the system described in the above embodiment; the method comprises the following steps:
s501: before charging, the non-isolated AC-DC charging module is controlled to be disconnected with a power grid, the isolated AC-DC converter is controlled to rectify alternating current provided by the power grid into direct current, and the insulation monitoring circuit is controlled to monitor the insulation resistance to the ground of a direct current bus;
s502: and when the insulation monitoring is finished and the insulation is normal, controlling the isolated AC-DC converter to stop working, controlling the input end of the non-isolated AC-DC charging module to be connected with a power grid, and controlling the non-isolated AC-DC charging module to charge the electric automobile.
Insulation monitoring is performed before charging, and insulation monitoring is not performed in the charging process. However, during insulation monitoring, the power grid needs to be isolated from the direct current side, so before charging, the embodiment of the application adopts the isolated AC-DC converter to work for isolation, and at this time, the non-isolated AC-DC charging module is disconnected from the power grid at both physical and electrical levels. After the insulation monitoring is finished, the isolated AC-DC converter quits working, the non-isolated AC-DC charging module is connected with the power grid, and the non-isolated AC-DC charging module performs electric energy conversion to charge the electric automobile. Because the isolated AC-DC converter is only used for insulation monitoring before charging, the power of the isolated AC-DC converter can be small, and the isolated AC-DC converter is small in size and low in cost. The AC-DC converter is bulky and costly due to the bulky isolation devices. And the non-isolated AC-DC charging module is in a non-isolated type, so that the volume is small and the cost is low.
After the insulation monitoring is completed, in order to avoid too large current impact on the non-isolated AC-DC charging module when the non-isolated AC-DC charging module is connected to the power grid, the method may further include, before the controlling the isolated AC-DC converter to stop operating, charging the DC bus with the isolated AC-DC converter after the insulation monitoring is completed:
and controlling the isolated AC-DC converter to charge the direct-current bus to a preset threshold voltage, controlling a controllable switch to be closed, and connecting the input end of the non-isolated AC-DC charging module with the power grid through the controllable switch.
At this time, the voltage difference between the input end and the output end of the non-isolated AC-DC charging module is not too large, so that the internal switching tube, the capacitance, the inductance and other electrical elements cannot be damaged, the devices are protected, and the service life of the devices is prolonged.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A charging system for an electric vehicle, comprising: the device comprises a non-isolated AC-DC charging module, an isolated AC-DC converter and an insulation monitoring circuit;
the input end of the isolated AC-DC converter is connected with a power grid, and the output end of the isolated AC-DC converter is connected with a direct current bus;
the isolated AC-DC converter is used for rectifying alternating current provided by the power grid into direct current before the electric automobile is charged and does not work when the electric automobile is charged;
the insulation monitoring circuit is used for monitoring the insulation resistance to the ground of the direct current bus when the isolated AC-DC converter works;
the input end of the non-isolated AC-DC charging module is connected with the power grid, and the output end of the non-isolated AC-DC charging module is connected with the input end of the direct current bus;
the non-isolated AC-DC charging module is used for rectifying alternating current provided by the power grid into direct current when the electric automobile is charged; and when the electric automobile is not charged, the connection with the power grid is disconnected.
2. The system of claim 1, further comprising: a controller and a controllable switch;
the input end of the non-isolated AC-DC charging module is connected with the power grid through the controllable switch;
the controller is used for controlling the controllable switch to be switched off when the electric automobile is not charged; and when the electric automobile is charged, controlling the controllable switch to be closed.
3. The system of claim 1, wherein the non-isolated AC-DC charging module comprises any one of:
the system comprises a VIENNA rectifier-based non-isolated AC/DC charging module, a two-level PWM rectifier-based non-isolated AC/DC charging module, a T-type three-level rectifier-based non-isolated AC/DC charging module, an I-type NPC rectifier-based non-isolated AC/DC charging module, an ANPC rectifier-based non-isolated AC/DC charging module and a flying capacitor rectifier-based non-isolated AC/DC charging module.
4. The system of claim 3, wherein the output of the non-isolated AC-DC charging module further comprises any one of the following DC-DC converters:
buck, boost, and buck-boost.
5. The system of any of claims 1-4, wherein the isolated AC-DC converter comprises any of:
the converter comprises a front-stage diode uncontrolled rectifying and post-stage flyback converter, a front-stage diode uncontrolled rectifying and post-stage push-pull converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting full-bridge converter, a front-stage diode uncontrolled rectifying and post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage flyback converter, a front-stage APFC plus post-stage push-pull converter, a front-stage APFC plus post-stage forward converter, a front-stage APFC plus post-stage phase-shifting full-bridge converter, a front-stage APFC plus post-stage phase-shifting half-bridge converter, a front-stage APFC plus post-stage LLC converter and a front-stage diode uncontrolled rectifying and post-stage forward converter.
6. The system of any of claims 1-4, wherein a maximum power of the isolated AC-DC converter is less than a maximum power of the non-isolated AC-DC charging module.
7. The system of any of claims 1-4, wherein the non-isolated AC-DC charging module comprises at least two of: a first non-isolated AC-DC charging module and a second non-isolated AC-DC charging module;
the first and second non-isolated AC-DC charging modules are connected in parallel with each other.
8. The system of claim 2, wherein the controller is further configured to control the isolated AC-DC converter to charge the DC bus to a preset threshold voltage when the insulation is determined to be normal through the insulation resistance detected by the insulation monitoring circuit, and then control the isolated AC-DC converter to stop working, so as to control the controllable switch to be closed.
9. A charging control method for an electric vehicle, applied to the system according to any one of claims 1 to 8, comprising:
before charging, the non-isolated AC-DC charging module is controlled to be disconnected with a power grid, the isolated AC-DC converter is controlled to rectify alternating current provided by the power grid into direct current, and the insulation monitoring circuit is controlled to monitor the insulation resistance to the ground of a direct current bus;
and when the insulation monitoring is finished and the insulation is normal, controlling the isolated AC-DC converter to stop working, controlling the input end of the non-isolated AC-DC charging module to be connected with a power grid, and controlling the non-isolated AC-DC charging module to charge the electric automobile.
10. The method of claim 9, further comprising, prior to said controlling said isolated AC-DC converter to cease operation:
and controlling the isolated AC-DC converter to charge the direct-current bus to a preset threshold voltage, controlling a controllable switch to be closed, and connecting the input end of the non-isolated AC-DC charging module with the power grid through the controllable switch.
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