CN111267649A - Maximum efficiency tracking control method and vehicle-mounted charging system - Google Patents

Maximum efficiency tracking control method and vehicle-mounted charging system Download PDF

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CN111267649A
CN111267649A CN201811480364.9A CN201811480364A CN111267649A CN 111267649 A CN111267649 A CN 111267649A CN 201811480364 A CN201811480364 A CN 201811480364A CN 111267649 A CN111267649 A CN 111267649A
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converter
maximum efficiency
power
current
charging system
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罗雪肖
林壮
蒋亚娟
沈杰
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LG Electronics Shanghai Research and Development Center Co Ltd
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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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/14—Plug-in electric vehicles

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Abstract

The invention discloses a maximum efficiency tracking control method and a vehicle-mounted charging system. The maximum efficiency tracking control method comprises the following steps: the maximum efficiency tracking module is used for tracking and obtaining the output current of each converter when the vehicle-mounted charging system is in the maximum efficiency according to the current operating condition, the maximum efficiency tracking module is used for respectively distributing the obtained output current of each converter to each converter, and the converter group is used for converting the power provided by the alternating current power supply according to the output current corresponding to each converter and then outputting the converted power to a load. The maximum efficiency tracking module of the invention utilizes the maximum efficiency tracking to obtain the output current of each converter, so that the vehicle-mounted charging system is at the maximum efficiency, and the power conversion efficiency of the vehicle-mounted charging system is improved.

Description

Maximum efficiency tracking control method and vehicle-mounted charging system
Technical Field
The invention relates to the technical field of vehicle-mounted charging, in particular to a maximum efficiency tracking control method and a vehicle-mounted charging system.
Background
This section is intended to provide a background or context to the embodiments of the invention that are recited in the claims. The description herein is not admitted to be prior art by inclusion in this section.
With the development of vehicle-mounted charging technology and electric vehicles, the vehicle-mounted charging technology of the electric vehicles is also widely developed and applied. Meanwhile, high-power electric vehicles are increasing day by day, the charging time of the electric vehicles is decreasing day by day, and the vehicle-mounted charging technology also gets extensive attention from the industry. The traditional parallel charging technology is mainly applied to a direct-current power supply system, buses of all power supply modules are connected together in a parallel mode, and outputs are connected together in a parallel mode. The output current balance of each power supply module is realized mainly by adopting a parallel current-sharing control technology, namely the output current of each power supply module is controlled to be equal to realize the current sharing among all the modules so as to output corresponding power.
The conventional parallel current sharing control technology mainly comprises: droop method, master/slave setting method, average current automatic current sharing method, maximum current automatic current sharing method, thermal stress automatic current sharing method and external current sharing controller current sharing method.
The droop method is the simplest current sharing method, and current sharing is achieved by adjusting the output impedance of the converter (namely, adjusting the external characteristic gradient). However, the droop method has poor current distribution characteristics at low current and a reduced voltage regulation rate. In order to achieve current sharing, each module must be adjusted independently, and current sharing is difficult to achieve for parallel modules with different rated powers.
The master/slave setup method is applicable to a parallel switching power supply system employing current mode control. The master module works according to the voltage control rule, the other slave modules work in a current control mode, the current of each slave module is modulated according to the same value and basically consistent with the current of the master module, and therefore current sharing is achieved. By adopting a master/slave setting method, communication between a master module and a slave module is required, so that the system is more complicated. If the main module fails, the whole power supply system cannot work, and the method is not suitable for a redundant parallel system. In addition, the voltage loop of the parallel switching power supply system based on the master/slave setting method is wide and is easily interfered by the outside.
The average current automatic current equalizing method is to compare the voltage signal of each module with the voltage signal of the current equalizing bus to obtain the compensation quantity to control and realize current equalizing. By adopting the average current automatic current equalizing method, when the current equalizing bus is short-circuited or any module connected on the bus cannot work, the voltage of the bus is reduced, the voltage of each module is reduced, even the voltage reaches the lower limit, and as a result, a fault is caused. When the current of a certain module rises to the limit, the module is greatly increased, and the output voltage of the module is automatically adjusted to the lower limit.
The maximum current automatic current-sharing method links the parallel power supply modules through the current-sharing bus, provides a current reference value for each power supply module, and all the parallel power supply modules adjust the output current according to the reference value, so that the total current of the system is accurately shared in each parallel power supply. The main module of the maximum current automatic current equalizing method is not fixed, and the module with the maximum current in the system automatically works as the main module. However, although the current sharing method using the additional current sharing controller can obtain a good current sharing effect and a good voltage regulation rate, the additional current sharing controller is needed, and once the current sharing controller fails, the system cannot work normally; and when the number of the parallel modules is large, the number of the parallel systems is large, and the reliability of the system is reduced to a certain extent.
The thermal stress auto-current sharing method achieves current sharing according to the current and temperature (i.e., thermal stress) of each module. The current sharing method of the additional current sharing controller needs to add one current sharing controller to a control circuit of each module, is used for detecting the unbalanced condition of the current of each module connected in parallel and adjusting a control signal, and therefore current sharing is achieved.
Due to various defects of the parallel current-sharing control technology, the efficiency of the vehicle-mounted charging system cannot be optimized by controlling each power supply module to output equal current, and the efficiency of power conversion of the vehicle-mounted charging system cannot be effectively improved.
Therefore, the conventional vehicle-mounted charging system has the problem of low power conversion efficiency.
Disclosure of Invention
The embodiment of the invention provides a maximum efficiency tracking control method, which is used for improving the power conversion efficiency of a vehicle-mounted charging system and is applied to the vehicle-mounted charging system, wherein the vehicle-mounted charging system comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, the converter group also comprises a maximum efficiency tracking module, and the method comprises the following steps:
the maximum efficiency tracking module is used for tracking and obtaining the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the current operating condition by utilizing the maximum efficiency;
the maximum efficiency tracking module distributes the obtained output current of each converter to each converter respectively;
and the converter group converts the power provided by the alternating current power supply according to the output current corresponding to each converter and then outputs the converted power to the load.
The embodiment of the present invention further provides a vehicle-mounted charging system based on the maximum efficiency tracking control method in the above embodiment, so as to improve the power conversion efficiency of the vehicle-mounted charging system, where the vehicle-mounted charging system includes:
the device comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, wherein the converter group further comprises a maximum efficiency tracking module.
In the embodiment of the invention, the vehicle-mounted charging system comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, and the converter group further comprises a maximum efficiency tracking module. The maximum efficiency tracking module is used for tracking and obtaining the output current of each converter when the vehicle-mounted charging system is in the maximum efficiency according to the current operating condition, the maximum efficiency tracking module is used for respectively distributing the obtained output current of each converter to each converter, and the converter group is used for converting the power provided by the alternating current power supply according to the output current corresponding to each converter and then outputting the converted power to a load. The maximum efficiency tracking module in the embodiment of the invention utilizes the maximum efficiency tracking to obtain the output current of each converter, so that the vehicle-mounted charging system is at the maximum efficiency, and therefore, the embodiment of the invention can improve the power conversion efficiency of the vehicle-mounted charging system.
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. In the drawings:
fig. 1 is a functional block diagram of a vehicle charging system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a vehicle-mounted charging system according to an embodiment of the present invention;
FIG. 3 is a flowchart illustrating an implementation of a maximum efficiency tracking control method according to an embodiment of the present invention;
fig. 4 is a flowchart illustrating the implementation of step 301 in the maximum efficiency tracking control method according to an embodiment of the present invention;
fig. 5 is a flowchart illustrating an implementation of step 401 in the maximum efficiency tracking control method according to an embodiment of the present invention;
fig. 6 is a flowchart of an implementation of determining a loss curve of a single converter in the maximum efficiency tracking control method according to the embodiment of the present invention;
FIG. 7 is a schematic diagram of an efficiency grid surface of an on-board charging system when a converter group includes two converters according to an embodiment of the present invention;
fig. 8 is a schematic diagram illustrating a comparison between an efficiency mesh curved surface of a vehicle-mounted charging system obtained by using a maximum efficiency tracking control method and an efficiency mesh curved surface of a vehicle-mounted charging system obtained by using a current sharing control method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
Fig. 1 is a functional block diagram of an in-vehicle charging system provided in an embodiment of the present invention, and for convenience of description, only the portions related to the embodiment of the present invention are shown, and the detailed description is as follows:
as shown in fig. 1, the vehicle charging system includes an ac power source 101, a load 102, and a converter group 103 respectively connected to the ac power source 101 and the load 102, where the converter group 103 further includes a maximum efficiency tracking module 104.
In a further embodiment, the ac power source 101 includes a single-phase ac power source, and it will be understood by those skilled in the art that the ac power source 101 may also include other ac power sources, for example, the ac power source 101 may also include a three-phase four-wire ac power source, which is not limited in this respect.
In addition, the circuit topology of each converter in the converter group comprises: ACDC level structure plus DCDC level structure. Wherein, the ACDC level structure is not limited, and the DCDC level structure is not limited.
In a further embodiment, the load comprises a battery system of an electric vehicle.
Fig. 2 shows a structural schematic diagram of the vehicle-mounted charging system provided by the embodiment of the invention, and for convenience of description, only the part related to the embodiment of the invention is shown, and the detailed description is as follows:
as shown in fig. 2, the ac power source 101 in the embodiment of the present invention is a single-phase ac power source, and when the ac power source 101 is a single-phase ac power source, one end of each of the input ports of the first inverter, the second inverter, …, and the nth inverter is connected to one end of the single-phase ac power source, and the other end of each of the input ports of the first inverter, the second inverter, …, and the nth inverter is connected to the other end of the single-phase ac power source.
The converter group 103 includes a first converter, a second converter, …, and an nth converter. The first converter, the second converter, … and the nth converter in the converter group 103 are all converters with isolated primary and secondary sides, and the difference of the internal parameters of each converter is within the allowable deviation range.
In a further embodiment, the first converter, the second converter, … and the nth converter in the converter group 103 communicate with each other by means of a bus. In a further embodiment, the bus comprises a Controller Area Network (CAN) bus. It will be understood by those skilled in the art that the first converter, the second converter, … and the nth converter in the converter group 103 CAN communicate with each other through other means besides CAN bus, such as RS232/RS485 and ControlNet bus, which is not limited by the embodiment of the present invention.
In another embodiment, if the ac power source 101 is a three-phase four-wire ac power source, one end of each of the first inverter, the second inverter, …, and the nth inverter input port is connected to a neutral line of the three-phase four-wire ac power source, and the other end of each of the first inverter, the second inverter, …, and the nth inverter input port is connected to any one three-phase port of the three-phase four-wire ac power source.
Fig. 3 illustrates an implementation flow of the maximum efficiency tracking control method provided by the embodiment of the present invention, and for convenience of description, only the relevant parts related to the embodiment of the present invention are illustrated, and the following details are described below:
as shown in fig. 3, the maximum efficiency tracking control method includes:
301, the maximum efficiency tracking module obtains an output current of each converter when the vehicle-mounted charging system is at the maximum efficiency by using the maximum efficiency tracking according to the current operating condition;
step 302, the maximum efficiency tracking module distributes the obtained output current of each converter to each converter respectively;
and 303, converting the power provided by the alternating current power supply by the converter group according to the output current corresponding to each converter, and outputting the converted power to the load.
In the embodiment of the invention, Maximum Efficiency tracking (hereinafter, referred to as Maximum Efficiency PointTracking, abbreviated as MEPT) refers to tracking the Efficiency of the vehicle-mounted charging system under the condition that the current operation condition is met, so that the vehicle-mounted charging system is at the Maximum Efficiency.
In the embodiment of the present invention, the maximum efficiency tracking module may obtain the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the current operating condition by using a maximum efficiency tracking algorithm, that is, the maximum efficiency module obtains the output currents I of the first converter, the second converter, … and the nth converter in the converter group by using a maximum efficiency algorithm1、I2… and In, and then respectively sending the obtained output current of each converter to each converter, and finally converting the power provided by the AC power supply by the converter group according to the output current corresponding to each converter and then outputting the converted power to the load, namely, a first converter, a second converter, a … and an nth converter In the converter group according to the output current I corresponding to each converter1、I2… and In, converting the power provided by the AC power supply and outputting the converted power to the load.
In an embodiment of the present invention, the maximum efficiency tracking module may be a controller in a main converter in the converter group 103. Wherein, when determining the main converter, considering that the state of each converter in the converter group is the same in the initial power-on state, any one converter in the converter group can be randomly set as the main converter. During operation, each converter comes and records its own operating time and output power and remains powered off and not cleared. At each subsequent start-up, considering that the state of each converter in the converter group is different at the time, the output power and the working time can be integrated, the accumulated electric energy emitted by each converter is determined, then the accumulated electric energy emitted by each converter is compared, and the converter with the minimum emitted accumulated electric energy in the converter group is taken as a main converter. In addition, the other converters in the converter group except the main converter are all the slave converters. Wherein, the current power is P under the assumption of the current operation condition0The current working voltage is U0。
In the embodiment of the invention, the maximum efficiency tracking module utilizes the maximum efficiency tracking to obtain the output current of each converter, so that the vehicle-mounted charging system is at the maximum efficiency, and the power conversion efficiency of the vehicle-mounted charging system can be improved.
Fig. 4 illustrates an implementation flow of step 301 in the maximum efficiency tracking control method provided by the embodiment of the present invention, and for convenience of description, only the relevant parts related to the embodiment of the present invention are illustrated, and the following details are described below:
in a further embodiment, as shown in fig. 4, step 301, the maximum efficiency tracking module uses maximum efficiency tracking to obtain an output current of each converter when the vehicle charging system is at maximum efficiency according to the current operating condition, including:
step 401, the maximum efficiency tracking module obtains each power distribution combination meeting a preset condition under the current operating condition;
step 402, the maximum efficiency tracking module obtains the total loss of each power distribution combination meeting the preset condition according to the loss curve of the single converter; when the converter group includes only one converter, the converter is called a single converter;
step 403, the maximum efficiency tracking module performs a cyclic comparison on the total loss of each power distribution combination meeting the preset condition to obtain a power distribution combination meeting the preset condition with the minimum total loss under the current operating condition;
in step 404, the maximum efficiency tracking module obtains an output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the power distribution combination with the minimum total loss and meeting the preset condition.
Similarly, assume that the current operating condition is that the current power is P0The current working voltage is U0. The preset condition is a preset condition, and those skilled in the art can understand that the preset condition may be set according to actual requirements, which is not particularly limited in the embodiment of the present invention.
In a further embodiment, the satisfaction of the preset condition comprises the satisfaction of the following condition:
Po＝Po1+Po2+…+Pon-1+Pon；
wherein, PoFor the output power, P, of the on-board charging system under the current operating conditionso1To PonThe output powers of the first converter to the nth converter are respectively. That is, the sum of the output power of the on-board charging system and the output power of the first to nth converters should be equal to satisfy the current operating condition. And then under the current operation condition, the maximum efficiency tracking module acquires each power distribution combination meeting the preset condition.
Further, the single converter is tested under the current operation condition, and a loss curve of the single converter is obtained. The single converter is a converter that is called a single converter when the converter group includes only one converter. Assuming that the loss curves of the first to nth converters in the converter group as a single converter are Ploss1、Ploss2、Ploss(n-2)、…、Ploss(n-1)And Plossn. The total loss of each power distribution combination meeting the preset condition refers to the sum of loss curves of each converter in the converter group as a single converter, and the total loss consumption P of each power distribution combination meeting the preset condition is assumedlossAnd then, the following conditions are satisfied: ploss＝Ploss1+Ploss2+…+Ploss(n-2)+Ploss(n-1)+Plossn. Namely, the maximum efficiency tracking module obtains the total loss of each power distribution combination meeting the preset condition according to the loss curve of the single converter.
According to the total loss of the power distribution combinations meeting the preset conditions, the maximum efficiency tracking module circularly compares the total loss of each power distribution combination meeting the preset conditions to determine the power distribution combination meeting the preset conditions and having the minimum total loss under the current operation conditions, and the total loss of the power distribution combination having the minimum total loss under the current operation conditions can be PlossminAnd (4) showing. Assuming that the first to nth converters in the converter group are changed when the total loss of the power distribution combination is minimal under the current operating conditionsThe corresponding output power of the converter is respectively Po1min、Po2min、…、P(on-1)minAnd PonminAnd satisfies the following conditions: po＝Po1min+Po2min+…+P(on-1)min+Ponmin。
Considering that the working voltage of the vehicle-mounted charging system under the current operation condition is U0I.e. the working voltages of the first to nth converters in the converter group are all U0According to the power distribution combination P satisfying the preset condition with the minimum total losso1min、Po2min、…、P(on-1)minAnd PonminAnd obtaining the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency. Assuming that the output current of each converter is I when the vehicle-mounted charging system is at maximum efficiency1、I2、…、In-1And InThen, there are:
Figure BDA0001893225920000071
and
Figure BDA0001893225920000072
in the embodiment of the invention, the maximum efficiency tracking module obtains the total loss of each power distribution combination meeting the preset condition according to the loss curve of the single converter, obtains the power distribution combination meeting the preset condition with the minimum total loss, and further obtains the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the power distribution combination meeting the preset condition with the minimum total loss, so that the power conversion efficiency of the vehicle-mounted charging system can be further improved.
In a further embodiment, each converter in the converter group comprises a digital processing chip, and the loss curve of the single converter obtained in the above way is loaded into the digital processing chip of each converter.
Fig. 5 illustrates an implementation flow of step 401 in the maximum efficiency tracking control method provided by the embodiment of the present invention, and for convenience of description, only the relevant parts related to the embodiment of the present invention are illustrated, and the following details are described below:
in a further embodiment, as shown in fig. 5, step 401, the maximum efficiency tracking module obtains each power allocation combination satisfying the preset condition under the current operating condition, including:
step 501, under the current operating condition, the maximum efficiency tracking module sequentially increases the possible values of the output powers of the first converter to the nth converter from zero to P according to the power step lengtho、Po-Po1、…、Po-Po1-Po2…Pn-3-Pn-2、Po-Po1-Po2…Pn-2-Pn-1；
Step 502, maximum efficiency tracking module separately from Po、Po-Po1、…、Po-Po1-Po2…Pn-3-Pn-2、Po-Po1-Po2…Pn-2-Pn-1One value is selected, so that the sum of the selected n values is equal to the output power P of the vehicle charging system under the current operation conditiono。
In the embodiment of the present invention, the power step refers to the minimum unit of value that is increased or decreased when the output power of the converter is adjusted, and generally, the power step may be set to 1 watt, and it will be understood by those skilled in the art that the power step may also be set to other values, for example, the power step may be set to 2 watts, which is not limited by the embodiment of the present invention. We can adopt PstepRepresenting the power step.
At the time of obtaining each power distribution combination satisfying the preset condition, at the current operation condition (i.e. the working power P)oOperating voltage U0) Then, the possible value of the output power of the first converter is gradually increased to P according to the power stepoPossible values of the output power of the first converter then include: 0. pstep、2Pstep、3Pstep、…、PoPossible values of the output power of the second converter include: 0. pstep、2Pstep、3Pstep、…、Po-Po1(ii) a Possible values of the output power of the third converter include: 0. pstep、2Pstep、3Pstep、…、Po-Po1-Po2And so on, possible values of the output power of the n-1 st converter include: 0. pstep、2Pstep、3Pstep、…、Po-Po1-Po2…Pn-3-Pn-2Possible values of the output power of the nth converter include: 0. pstep、2Pstep、3Pstep、…、Po-Po1-Po2…Pn-2-Pn-1。
After obtaining the possible values of the output powers of the first converter to the nth converter, selecting a value from the possible values of the output powers of the first converter to the nth converter, that is, a first value is selected from the possible values of the output power of the first converter, a second value is selected from the possible values of the output power of the second converter, a third value is selected from the possible values of the output power of the third converter, a fourth value is selected from the possible values of the output power of the fourth converter, and so on, until an n-1 th value is selected from the possible values of the output power of the n-1 th converter, an nth value is selected from the possible values of the output power of the nth converter, so that n values are selected from the possible values of the output power of the first converter to the nth converter, and the selected n values satisfy that the sum of the n values is equal to the operating power P.o。
When selecting n values from the possible values of the output power of the first to nth converters, the output power of the first converter may be selected to be PoThe output power of other converters is zero; or the output powers of the first converter to the n-1 converter can be selected to be power step length PstepSelecting the output power of the nth converter as Pon-(n-1)PstepAnd so on. Therefore, a plurality of power distribution combinations may be acquired such that the acquired power distribution combinations each satisfy that the sum of powers is equal to the output power P of the vehicle-mounted charging systemo。
Fig. 6 illustrates an implementation flow of determining a loss curve of a single converter in the maximum efficiency tracking control method provided by the embodiment of the present invention, and for convenience of description, only the portion related to the embodiment of the present invention is illustrated, and the detailed description is as follows:
in a further embodiment, referring to fig. 6, determining a loss curve for a single converter includes:
601, obtaining an efficiency curve of a single converter by a maximum efficiency tracking module according to the current operating condition;
in step 602, the maximum efficiency tracking module obtains a loss curve of the single converter under the current operating condition according to the efficiency curve of the single converter.
The efficiency curve of the converter is a curve showing a trend in the conversion efficiency of the converter power. The loss curve of the converter is a curve showing the trend of the converter power loss. As indicated above, the efficiency curves here are the efficiency curve and the loss curve of a single converter. That is, when the converter group includes only one converter, the efficiency curve and the loss curve of the one converter are obtained. In particular, it is possible to operate at the current operating conditions (i.e. operating power P)oOperating voltage U0) Then, each converter in the converter group is tested as a single converter, and an efficiency curve of each converter in the converter group as a single converter is obtained.
Assuming that the efficiency of the single converter is represented by η and the loss is represented by S, a certain loss on the loss curve of the single converter and a certain efficiency corresponding to the efficiency curve of the single converter satisfy the following relation:
Figure BDA0001893225920000091
wherein, P0The output power of the onboard charging system is the current operating condition.
Therefore, after the efficiency curve of the single converter is obtained, according to the efficiency of each point on the efficiency curve, the loss of the single converter corresponding to each point is determined through the formula, the obtained loss data of each point is drawn into a curve, and the drawn curve is the loss curve of the single converter.
In order to improve the efficiency of determining the loss curve of the single converter, the efficiency of several points can be selected from the efficiency curve of the single converter, the loss corresponding to the several points is obtained through calculation, and the loss corresponding to the several points is used for fitting to obtain the loss curve of the single converter.
In addition, under the current operating conditions (i.e. operating power P)oOperating voltage U0) When the change occurs, according to a new operating condition and according to a selection principle that the converter which generates the minimum accumulated electric energy is the main converter, the new main converter is selected, and the output current of each converter in the converter group is obtained by using the maximum efficiency tracking control method in any embodiment, so that the maximum efficiency of the vehicle-mounted charging system under the new operating condition is realized.
Further, the vehicle-mounted charging system shown in fig. 1 is configured to execute the maximum efficiency tracking control method according to any one of the embodiments. As shown in fig. 1, the vehicle-mounted charging system includes: the device comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, wherein the converter group further comprises a maximum efficiency tracking module.
In a further embodiment, the maximum efficiency tracking module may further include an upper computer. The function of the maximum efficiency tracking module is realized through the upper computer in the converter group. That is, the output current of each inverter when the vehicle-mounted charging system is made to be at the maximum efficiency is determined by the upper computer, and then the upper computer distributes the obtained output current of each inverter to each inverter in the inverter group. The upper computer and each converter in the converter group can communicate in a bus mode.
In a further embodiment, both the master converter and the slave converter comprise a voltage loop and a current loop. The main converter stabilizes the voltage of the load by controlling the voltage loop, and both the main converter and the slave converter control the current loop to track the output current distributed by the main converter to each converter.
Fig. 7 is a schematic diagram of an efficiency grid surface of an on-vehicle charging system when a converter group includes two converters according to an embodiment of the present invention, and for convenience of description, only the parts related to the embodiment of the present invention are shown, and detailed descriptions are as follows:
in the embodiment of the invention, the converter group only comprises two converters, namely the first converter and the second converter, and the efficiency mesh surface schematic diagram of the vehicle-mounted charging system is drawn based on the two converters.
As shown in fig. 7, by the maximum efficiency tracking control method, the boundary between the power plane (i.e., the power plane formed by the combination of all the powers of which the sum of the output power of the first converter and the output power of the second converter is 2 kW) when the total output power of the in-vehicle charging system is 2kW and the efficiency grid curve of the in-vehicle charging system is obtained. The boundary line between the power plane and the efficiency grid curve is a curve formed by the efficiencies of the vehicle-mounted charging systems corresponding to different power combinations when the sum of the output power of the first converter and the output power of the second converter is 2 kW.
As can be seen from fig. 7, when the efficiency of the on-vehicle charging system corresponding to the different power combinations of the first converter and the second converter is maximum under the condition that the total output power of the on-vehicle charging system is 2kW, only one converter is operated, and the output power is 2kW, while the other converter is not operated, that is, under the condition that there is no output power.
That is, when the output power of the first converter is 2kw and the output power of the second converter is zero, or when the output power of the first converter is zero and the output power of the second converter is 2kw, the vehicle-mounted charging system reaches the maximum efficiency.
Fig. 8 shows a comparison between an efficiency mesh surface of an in-vehicle charging system obtained by using a maximum efficiency tracking control method according to an embodiment of the present invention and an efficiency mesh surface of an in-vehicle charging system obtained by using a current sharing control method, where for convenience of description, only the portions related to the embodiment of the present invention are shown, and details are as follows:
as shown in fig. 8, the first efficiency mesh curved surface is an efficiency mesh curved surface of the vehicle-mounted charging system obtained by using the maximum efficiency tracking control method, and the second efficiency mesh curved surface is an efficiency mesh curved surface of the vehicle-mounted charging system obtained by using a conventional current sharing control method. As can be seen from fig. 8, under the condition of light load (i.e. 20% rated load to 50% rated load), the average efficiency of the first-efficiency mesh curved surface is improved by about 2% compared with the average efficiency of the second-efficiency mesh curved surface in the vehicle-mounted charging system. In addition, the efficiency of the first efficiency mesh surface is improved less compared to the efficiency of the second efficiency mesh surface when the load is heavier. The efficiency of the first efficiency mesh surface is substantially the same as the efficiency of the second efficiency mesh surface near or at full load.
As shown in fig. 8, for the same operating conditions, the efficiency of the vehicle-mounted charging system obtained by the maximum efficiency tracking control method is improved compared with the efficiency of the vehicle-mounted charging system obtained by the current sharing control method. Particularly, when the vehicle-mounted charging system is in light load (namely 20% rated load to 50% rated load), the efficiency of the vehicle-mounted charging system obtained by the maximum efficiency tracking control method is obviously improved compared with the efficiency of the vehicle-mounted charging system obtained by the current sharing control method. Experiments show that compared with the traditional current sharing control method, the light-load average efficiency of the vehicle-mounted charging system obtained by the maximum efficiency tracking control method is improved by about 2%. Experiments also show that the larger the number of converters in the converter group, the larger the rate of improvement in the light-load average efficiency of the vehicle-mounted charging system by the maximum efficiency tracking control method.
In a further embodiment, the maximum efficiency tracking control method provided in any embodiment of the present invention may be an offline algorithm, that is, under the conditions of different output powers and output voltages, a power distribution combination table of each converter in the converter group is obtained by using the maximum efficiency tracking control method, and then the power distribution combination table is recorded in a control chip of the converter, and the control chip of the converter searches for the power distribution combination table during the operation process, so that the power distribution combination of the converter when the vehicle-mounted charging system is at the maximum efficiency is performed.
In addition, in another embodiment of the present invention, the maximum efficiency tracking control method may also be an online algorithm. In the running process, according to different output powers and output voltages, the power distribution combination of the converter when the vehicle-mounted charging system is at the maximum efficiency is obtained through real-time calculation and executed, and therefore the maximum efficiency running point of the vehicle-mounted charging system is tracked. Each converter in the converter group is loaded with the maximum efficiency tracking control method.
The embodiment of the present invention further provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor, and the processor implements the maximum efficiency tracking control method when executing the computer program.
An embodiment of the present invention further provides a computer-readable storage medium, where a computer program for executing the maximum efficiency tracking control method is stored in the computer-readable storage medium.
In summary, in the embodiment of the present invention, the vehicle-mounted charging system includes an ac power supply, a load, and a converter group respectively connected to the ac power supply and the load, and the converter group further includes a maximum efficiency tracking module. The maximum efficiency tracking module is used for tracking and obtaining the output current of each converter when the vehicle-mounted charging system is in the maximum efficiency according to the current operating condition, the maximum efficiency tracking module is used for respectively distributing the obtained output current of each converter to each converter, and the converter group is used for converting the power provided by the alternating current power supply according to the output current corresponding to each converter and then outputting the converted power to a load. The maximum efficiency tracking module in the embodiment of the invention utilizes the maximum efficiency tracking to obtain the output current of each converter, so that the vehicle-mounted charging system is at the maximum efficiency, and therefore, the embodiment of the invention can improve the power conversion efficiency of the vehicle-mounted charging system.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The maximum efficiency tracking control method is applied to a vehicle-mounted charging system, the vehicle-mounted charging system comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, the converter group further comprises a maximum efficiency tracking module, and the method comprises the following steps:
the maximum efficiency tracking module is used for tracking and obtaining the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the current operating condition by utilizing the maximum efficiency;
the maximum efficiency tracking module distributes the obtained output current of each converter to each converter respectively;
and the converter group converts the power provided by the alternating current power supply according to the output current corresponding to each converter and then outputs the converted power to the load.
2. The maximum efficiency tracking control method as claimed in claim 1, wherein said maximum efficiency tracking module includes an upper computer.
3. The maximum efficiency tracking control method according to claim 1, wherein the maximum efficiency tracking module includes a controller in a main converter, the main converter is any one of the converter group which is randomly set in an initial power-on state or a converter which is determined to emit the smallest accumulated power each time power is turned on later.
4. The maximum efficiency tracking control method of claim 1, wherein the maximum efficiency tracking module using maximum efficiency tracking to obtain the output current of each converter at which the vehicle charging system is at maximum efficiency based on the current operating conditions comprises:
the maximum efficiency tracking module acquires each power distribution combination meeting a preset condition under the current operation condition;
the maximum efficiency tracking module obtains the total loss of each power distribution combination meeting the preset condition according to the loss curve of the single converter; when the converter group includes only one converter, the converter is called a single converter;
the maximum efficiency tracking module circularly compares the total loss of each power distribution combination meeting the preset condition to obtain the power distribution combination meeting the preset condition and with the minimum total loss under the current operation condition;
and the maximum efficiency tracking module obtains the output current of each converter when the vehicle-mounted charging system is at the maximum efficiency according to the power distribution combination with the minimum total loss and meeting the preset condition.
5. The maximum efficiency tracking control method according to claim 4, wherein the converter group includes first to nth converters, and the satisfying of the predetermined condition includes satisfying of the following conditions:
Po＝Po1+Po2+…+Pon-1+Pon；
wherein, PoFor the output power, P, of the on-board charging system under the current operating conditionso1To PonThe output powers of the first converter to the nth converter are respectively.
6. The maximum efficiency tracking control method as claimed in claim 5, wherein the maximum efficiency tracking module obtaining each power allocation combination satisfying the preset condition under the current operation condition comprises:
the maximum efficiency tracking module enables the possible values of the output power of the first converter to the nth converter to be respectively according to the power step under the current operating conditionSequentially increasing from zero to Po、Po-Po1、…、Po-Po1-Po2…Pn-3-Pn-2、Po-Po1-Po2…Pn-2-Pn-1；
The maximum efficiency tracking module selects a value from possible values of output power of the first converter to the nth converter respectively, so that the sum of the selected n values is equal to the output power P of the on-board charging system under the current operating conditiono。
7. The maximum efficiency tracking control method of claim 4, wherein the loss curve for a single converter is determined by:
the maximum efficiency tracking module obtains an efficiency curve of the single converter according to the current operating condition;
the maximum efficiency tracking module obtains a loss curve of the single converter under the current operating condition according to the efficiency curve of the single converter.
8. An in-vehicle charging system to which the maximum efficiency tracking control method according to any one of claims 1 to 7 is applied, comprising:
the device comprises an alternating current power supply, a load and a converter group respectively connected with the alternating current power supply and the load, wherein the converter group further comprises a maximum efficiency tracking module.
9. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program for executing the method of any one of claims 1 to 7.
CN201811480364.9A 2018-12-05 2018-12-05 Maximum efficiency tracking control method and vehicle-mounted charging system Withdrawn CN111267649A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112644322A (en) * 2020-12-28 2021-04-13 国网广汇(上海)电动汽车服务有限公司 Electric vehicle battery charging and discharging control system and control method
CN112910061A (en) * 2021-04-07 2021-06-04 科世达(上海)机电有限公司 Control method, device and medium for charging system load balancing

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112644322A (en) * 2020-12-28 2021-04-13 国网广汇(上海)电动汽车服务有限公司 Electric vehicle battery charging and discharging control system and control method
CN112910061A (en) * 2021-04-07 2021-06-04 科世达(上海)机电有限公司 Control method, device and medium for charging system load balancing

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