A method and application for optimizing AC-DC efficiency during charging of a DC charger

Abstract

A method and application for optimizing the AC-to-DC efficiency of a DC charger. The DC charger has multiple charging modules. By controlling the number of activated charging modules, the actual output power of the activated charging modules is controlled to above 50% of the rated power, thereby improving charger efficiency and reducing losses. The method specifically includes the following steps: S1. Implementing an algorithm for determining the number of activated charging modules within the DC charger; S2. Communicating information between the DC charger and the charging vehicle, and uploading the obtained vehicle information to a cloud platform; S3. The DC charger's control unit exchanges data with the cloud platform and determines the number of activated charging modules.

Description

Technical Field

[0001] The present invention relates to the application field of direct current (DC) chargers, and in particular to a method and application for optimizing the AC-to-DC conversion efficiency of a DC charger during charging. Background Art

[0002] With the rapid development of the new energy vehicle industry, the electric vehicle charging pile industry and charging station construction have also grown rapidly. In particular, the demand for DC chargers for electric vehicles with so-called fast charging is growing rapidly. Currently, most DC chargers (referred to as chargers) on the market output power to electric vehicles in the form of AC-DC conversion. This involves AC-DC conversion efficiency, so improving the conversion efficiency of DC chargers is crucial.

[0003] The charging module is a core component of a DC charger. During the charging process, the energy loss of the entire charger can be largely attributed to the charging module. Compared to this loss, other losses, such as power loss in the control board and cable losses, are negligible. Therefore, the higher the output power of the charging module, the higher the AC-to-DC conversion efficiency of the DC charger, and thus the higher the charger efficiency. However, both the output power of the charging module and the efficiency of the charger remain to be improved in existing technologies. Summary of the Invention

[0004] The present invention aims to provide a method and application for optimizing the AC-to-DC efficiency of a DC charger during charging, so as to improve the efficiency of the charger and reduce losses.

[0005] In order to solve the above technical problems, the specific solution adopted by the present invention is: a method for optimizing the AC-to-DC efficiency of a DC charger during charging, wherein the DC charger has multiple charging modules, and by controlling the number of charging modules started, the output power of the started charging modules is controlled to be above 50% of the rated power.

[0006] As a further optimization of the above technical solution, the algorithm for determining the number of charging modules started is as follows:

[0007] 1) When Start all charging modules;

[0008] 2) When

[0009] 2-1) When the output voltage U of the charging module is [U b ,U c ] interval, the output power P' of the charging module and the number of charging module startups n are determined by the following formula (1):

[0010]

[0011] The obtained P' takes the minimum value within its range, and n takes the maximum value within its range;

[0012] 2-2) When the output voltage U of the charging module is [U a ,U b ] interval:

[0013] 2-2-1) When When , the charging module operating current I and the number of charging module startups n are determined by the following formula (2):

[0014]

[0015] In the obtained range, I takes the minimum value and n takes the maximum value;

[0016] 2-2-2) When When the charging module cannot output more than half of the rated power at voltage U, the starting working number n of the charging module is determined by the following formula (3):

[0017]

[0018] In the obtained range, n takes the minimum value.

[0019] Among them, P O is the required power, P n is the rated power of the DC charger, P' is the output power of the charging module, P e is the rated power of the charging module, n is the number of working charging modules, [U a , U c ] is the output voltage range of the charging module; [U b , U c ] is the voltage range that the charging module can output according to the rated power, I is the working current of the charging module, I a The output voltage of the charging module is [U a ,U b ) range.

[0020] An application of a method for optimizing AC-to-DC efficiency during charging of a DC charger, comprising the following steps:

[0021] S1. Place the algorithm for determining the number of charging modules started in the DC charger;

[0022] S2. The DC charger interacts with the charging vehicle information and uploads the read charging vehicle information to the cloud platform;

[0023] S3. The control unit of the DC charger exchanges data with the cloud platform to determine the number of charging modules started.

[0024] As a further optimization of the above technical solution, the control unit has wireless communication function and can exchange data with the cloud platform through the 4G network.

[0025] As a further optimization of the above technical solution, the data information of the current charging vehicle read by the DC charger also includes the required current, the charging vehicle frame number and the charging vehicle SOC information.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the present invention controls the output power of the working charging modules to be above 50% of the rated power by adjusting the starting number of the charging modules, thereby improving the efficiency of the charger. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the overall structural diagram of the present invention;

[0028] Figure 2 It is the voltage and current curve of the charging module;

[0029] Figure 3 It is an iteration diagram of the algorithm for determining the number of charging module startups;

[0030] Reference numerals: 101 , power supply, 102 , charging module, 103 , control unit, 104 , charging vehicle, 105 , cloud platform. DETAILED DESCRIPTION

[0031] Example 1

[0032] This embodiment provides a method for optimizing the AC-to-DC efficiency of a DC charger. The DC charger has multiple charging modules. This embodiment controls the number of activated charging modules to control the output power of the activated charging modules to above 50% of the rated power, thereby improving the efficiency of the charger.

[0033] Charging module output rate = actual output power / rated output power * 100%. According to the document NB / T33001-2018 "Technical Requirements for Non-Onboard Conductive Chargers for Electric Vehicles", when the charging module output rate is 20% ≤ ≤ 50%, the charger efficiency is ≥ 88%. When the charging module output rate is 50% < ≤ 100%, the charger efficiency is ≥ 93%. The present invention adjusts the number of activated charging modules to ensure that the charging module output rate is 50% < ≤ 100%, that is, the actual output power of the operating charging module is controlled to above 50% of the rated output power, thereby achieving a charger efficiency of ≥ 93% for the DC charger.

[0034] like Figure 2 The voltage and current curve of the charging module is shown. The output voltage of the charging module is b to U cWithin the voltage range, the charging module can output according to the rated output power. The output voltage of the charging module is within the range of U a to U b Within this range, the charging module cannot output the rated output power, and the maximum output power is only voltage*current (U*I a )

[0035] The algorithm for determining the number of charging modules started is as follows:

[0036] 1) When Start all charging modules;

[0037] 2) When

[0038] 2-1) When the output voltage U of the charging module is [U b ,U c ] interval, the charging module working power P' and the number of charging module startups n are determined by the following formula (1):

[0039]

[0040] The obtained P' takes the minimum value within its range, and n takes the maximum value within its range;

[0041] 2-2) When the output voltage U of the charging module is [U a ,U b ] interval:

[0042] 2-2-1) When When , the charging module operating current I and the number of charging module startups n are determined by the following formula (2):

[0043]

[0044] In the obtained range, I takes the minimum value and n takes the maximum value;

[0045] 2-2-2) When When the charging module cannot output more than half of the rated power at voltage U, the starting working number n of the charging module is determined by the following formula (3):

[0046]

[0047] In the obtained range, n takes the minimum value;

[0048] Among them, P O is the required power, P nis the rated power of the DC charger, P' is the output power of the charging module, Pe is the rated power of the charging module, n is the number of working units of the charging module, [Ua, Uc] is the output voltage range of the charging module; [Ub, Uc] is the voltage range that the charging module can output according to the rated power, I is the working current of the charging module, I a The output voltage of the charging module is [U a ,U b ) range.

[0049] Example 2

[0050] This embodiment is an application of a method for optimizing AC-to-DC efficiency during charging of a DC charger. The method is applied during the charging process of a DC charger and a charging vehicle.

[0051] like Figure 1 、 2 As shown in FIG. 3 , the DC charger 106 has a plurality of charging modules 102 . When charging the charging vehicle 104 , the power supply 101 input to the DC charger 106 is a three-phase AC power supply. The power supply 101 provides power for the DC charger 106 , the charging modules 102 , the control unit 103 and other components.

[0052] During charging, the DC charger 106 is connected to the charging vehicle 104 via a charging connection device provided with the DC charger 106. The charging vehicle 104 and the DC charger 106 exchange information via CAN communication during the charging process, and the communication protocol complies with national standards.

[0053] Specifically, the DC charger 106 communicates with the charging vehicle 104 through the charging connection device, and can read the current battery voltage, required current, charging vehicle frame number, charging vehicle SOC and other information of the charging vehicle 104, and transmit this information to the cloud platform in real time, and the cloud platform summarizes the information.

[0054] The control unit 103 in the DC charger 106 has wireless communication capabilities and can exchange data with the cloud platform via the 4G network. The control unit 103 communicates with the charging module 102 via CAN to monitor the status of the charging module 102.

[0055] The total power of the DC charger 106 depends on the rated power and number of the charging modules 102. The total power of the DC charger 106 is the sum of the powers of the charging modules 102. In practical applications, the rated power of the charging modules 102 is generally 20kW. Figure 2 The figure shows the voltage and current curve of the charging module. When the output voltage of the charging module 102 is U b to U cIn the interval, the charging module 102 can output at the rated power, i.e., 20 kW. When the output voltage of the charging module 102 is between U a to U b During this period, the charging module 102 cannot output at rated power, and the maximum output power is only voltage*current (U*I a ), that is, the output voltage range of the charging module 102 is [U a ,U c ], the output voltage is [U b ,U c ], the charging module can output according to the rated power, and the output voltage is [U a ,U b ) The maximum output power in the range increases with the voltage. The maximum output power is voltage*current (U*I a ).

[0056] While charging:

[0057] The DC charger 106 exchanges information with the charging vehicle 104, reading information such as the vehicle's current SOC, current battery voltage, required current, and vehicle frame number, and uploads this data to the cloud platform in real time. Simultaneously, the control unit 103 of the DC charger 106 exchanges data with the cloud platform and uses the method of Example 1 to determine the number of activated charging modules.

[0058] After the DC charger 106 is connected to the charging vehicle 104 , as charging proceeds, the current battery voltage of the charging vehicle 104 increases, and the output voltage of the charging module also increases.

[0059] When the output voltage of the charging module 102 is [U b ,U c ], each charging module 102 can output full power, then the required power is determined based on the product of the current battery voltage and the required current. After determining the required power, the number of started charging modules 102 can be determined to achieve the output power of each started charging module 102 controlled to be above 50% of its rated power.

[0060] The output voltage of the charging module 102 is [U a ,U b ), the current required power is obtained by the current battery voltage * required current method, and the charging module 102 can be used according to Figure 2 The charging module power supply current curve diagram finds the maximum current I that the charging module 102 can output corresponding to the current battery voltage. a , current battery voltage*I a, which is the maximum power that the charging module 102 can output at this time. After determining the required power and the corresponding maximum output power of the charging module 102, the number of activated charging modules 102 can be determined so that the output rate of each activated charging module 102 is above 50%.

[0061] Figure 3 It is an iterative diagram of the judgment algorithm for the number of startups of the charging module 102, which is specifically implemented as follows:

[0062] The test bench simulates measured data from various vehicle models in a test bench charger. Using this data (including the simulated vehicle's required voltage and current curves, the charging module's output voltage and current curves, AC input power, DC output power, and so on), a charging module control algorithm is developed. This algorithm is then integrated into the factory-installed DC charger. During customer equipment operation, the factory-installed DC charger functions as the on-site charger, which transmits vehicle data (VIN) and on-site charging data (including the vehicle's required voltage and current curves, the charging module's output voltage and current curves, AC input power, DC output power, and so on) to the charging cloud platform in real time. Considering the possibility that charging trends may change after charging curve updates for certain vehicles, the charging module control strategy is derived based on the latest data and compared with the DC charger using an algorithm based on the number of active charging modules. If any discrepancies occur, the strategy is updated.

[0063] The specific algorithm for the working quantity of the charging module is:

[0064] P O is the required power (the product of the current battery voltage and the required current), P n is the rated power of the whole machine, P' is the output power of the charging module, the rated power of the charging module is 20kW, and n is the number of working charging modules:

[0065] 1) When P O ≥1 / 2P n , start all charging modules;

[0066] 2) When P O <1 / 2P n :

[0067] 2.1) When the output voltage U of the charging module is [U b ,U c ], the output power P' and the number of working hours n of the charging module are determined by the following formula:

[0068]

[0069] The obtained P' takes the minimum value within its range, and n takes the maximum value;

[0070] 2.2) When the output voltage U of the charging module is [Ua ,U b )hour:

[0071] 2.2.1) When U*I a When the power is ≥10kW, the operating current I of the charging module and the number of working charging modules n are determined by the following formula:

[0072]

[0073] Within the obtained range, I takes the minimum value and n takes the maximum value.

[0074] 2.2.2) When U*Ia < 10kW, that is, the charging module cannot output more than half of the rated power at voltage U, the charging module determines the number of charging modules in operation according to the following formula:

[0075]

[0076] In the obtained range, n takes the minimum value.

[0077] The following is a detailed introduction based on a specific practical application process:

[0078] Take a certain type of charging module for example, module P e =20kW, U a =200V, U b =600V, U C =750V, Ia=33.3A, the DC charger is equipped with 6 modules of this model, then the rated power of the DC charger is P n =120kW.

[0079] 1) When the required power P O When the power is ≥60kW, all charging modules are started.

[0080] 2) When the required power P O <60kW, assuming P O =30kW;

[0081] 2.1) When the output voltage of the charging module is U = 600V, the output power P' and the number of working units n of the charging module are determined by the following formula:

[0082]

[0083] It is concluded that P'≥10kW and n≤3 and n is a positive integer.

[0084] Since P' takes the minimum value within its range and n takes the maximum value, we can obtain P'=10kW and n=3.

[0085] 2.2) When the output voltage U of the charging module is [Ua, Ub):

[0086] 2.2.1) When U = 500V, 500V*33.3A = 16.65kW > 10kW. The following formula is used to determine the operating current I of the charging module and the number of charging modules working n:

[0087]

[0088] It is concluded that I≥20A and n≤3 and n is a positive integer,

[0089] In the obtained range, I takes the minimum value and n takes the maximum value, resulting in I=20A and n=3.

[0090] 2.2.2) When U = 250V, 250V*33.3A = 8.33kW < 10kW, that is, the charging module cannot output more than half of the rated power at voltage U. At this time, the output determines the working quantity of the charging module:

[0091]

[0092] It is concluded that n≥3.6 and n is a positive integer,

[0093] Within the obtained range, n takes the minimum value, which is n = 4. At this time, the module operating power is 30kW / 4 = 7.5kW, and the module operating current is 7.5kW / 250V = 30A.

Claims

1. A method for optimizing AC-to-DC efficiency during charging of a DC charger, wherein the DC charger has multiple charging modules, characterized in that: By controlling the number of charging modules started, the output power of the started charging modules is controlled to be above 50% of the rated power; The algorithm for determining the number of charging modules started is: 1) When Start all charging modules; 2) When 2-1) When the output voltage U of the charging module is [U b, U c ] interval, the output power P' of the charging module and the number of charging module startups n are determined by the following formula (1): The obtained P' takes the minimum value within its range, and n takes the maximum value within its range; 2-2) When the output voltage U of the charging module is [U a, U b ] interval: 2-2-1) When When , the charging module operating current I and the number of charging module startups n are determined by the following formula (2): In the obtained range, I takes the minimum value and n takes the maximum value; 2-2-2) When When the charging module cannot output more than half of the rated power at voltage U, the starting working number n of the charging module is determined by the following formula (3): In the obtained range, n takes the minimum value; Among them, P O is the required power, P n is the rated power of the DC charger, P' is the output power of the charging module, P e is the rated power of the charging module, n is the number of working charging modules, [U a , U c ] is the output voltage range of the charging module; [U b , U c ] is the voltage range that the charging module can output according to the rated power, I is the working current of the charging module, I a The output voltage of the charging module is [U a ,U b ) range.

2. An application of the method for optimizing the AC-to-DC efficiency of a DC charger as claimed in claim 1, characterized in that: The following steps are involved: S1. Place the algorithm for determining the number of charging modules started in the DC charger; S2. The DC charger interacts with the charging vehicle information and uploads the read charging vehicle information to the cloud platform; S3. The control unit of the DC charger exchanges data with the cloud platform to determine the number of charging modules started.

3. An application of the method for optimizing the AC-to-DC efficiency of a DC charger as claimed in claim 2, characterized in that: The control unit has wireless communication function and can exchange data with the cloud platform through the 4G network.

4. An application of the method for optimizing the AC-to-DC efficiency of a DC charger as claimed in claim 2, characterized in that: The information of the current charging vehicle read by the DC charger includes the current battery voltage, required current, charging vehicle frame number and charging vehicle SOC information.

Images