Direct current charging system control method based on battery voltage dynamic adjustment

Abstract

The invention relates to the technical field of new energy charging piles, in particular to a direct current charging system control method based on battery voltage dynamic adjustment. When the output voltage V0 of the direct-current charging system adopts the vehicle end required voltage Vd, calculating the number K1 of the required power supply modules at the moment; when the output voltage V0 adopts the sum of the current power battery voltage Vb and the threshold voltage G0, the number K2 of the required power supply modules at the moment is calculated, and the K2 and K1 are the small value. According to the invention, the high-power direct-current charging system obtains information such as vehicle-end required voltage and required current in real time, combines the current power battery voltage, dynamically calculates the number of required power supply modules, and optimizes the output voltage by using an algorithm, thereby improving the use efficiency of the power supply modules, reducing the power loss, and saving the power consumption cost.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy charging piles, and in particular to a direct current charging system control method based on dynamic adjustment of battery voltage. Background Art

[0002] With the rapid development of the new energy electric vehicle industry and electric vehicle fast charging technology, high-power electric vehicle charging equipment that matches it has also emerged. The charging energy transmission of electric vehicles is achieved through the high-power DC charging system through protocol interaction with the BMS (battery management system of electric vehicles). However, the demand voltage sent by the BMS of electric vehicles to the high-power DC charging system is basically much higher than the current power battery voltage of electric vehicles, and most high-power DC charging systems calculate the output current of the current power module based on the demand voltage, resulting in reduced efficiency of the power module in the high-power DC charging system, the output power of the module is not fully utilized, and there is a lot of power loss in the power module in the high-power DC charging system. Summary of the invention

[0003] The problem to be solved by the present invention is to improve the use efficiency of a power module in a high-power DC charging system and reduce power loss.

[0004] In view of the deficiencies of the prior art, the technical solution adopted by the present invention to solve the technical problems is: a DC charging system control method based on dynamic adjustment of battery voltage, the DC charging system includes N power modules with a power of P, a main control system and other modules, and the DC charging system and the electric vehicle exchange information and complete energy transmission through a charging protocol, including the following steps:

[0005] Step 1: Obtain the vehicle-side required voltage V in the information flow parameters according to the protocol interaction d And vehicle-side demand current I d , calculate the required number of power modules K1 and the output voltage V0 of the corresponding DC charging system,

[0006]

[0007] V0=V d ,

[0008] Where P is the power of a single power module;

[0009] Step 2: Determine the corresponding threshold voltage G0 according to the current state of charge;

[0010] Step 3: Calculate the required number of power modules K2 and the output voltage V0 corresponding to K2 based on the threshold voltage G0;

[0011] Step 4: Determine the number of power modules K1 and the number of power modules K2 and compare the two.

[0012] Step 5: Determine the optimal number of power modules required K=MIN(K1, K2) and the corresponding output voltage V0;

[0013] Step 6: Update the charging output voltage V0, adjust the number of power modules to K, and the charging output current I d Remain unchanged.

[0014] Preferably, the number of power modules K2 required in step 3 and the output voltage V0 corresponding to K2 are calculated as follows:

[0015] V0=V b +G0

[0016]

[0017] Among them, V b is the current power battery voltage measured by the high-power DC charging system, G0 is the threshold voltage, I d is the vehicle-side demand current in the information flow, and P is the power of a single power module.

[0018] Preferably, the value of the output voltage V0 corresponding to step 5 is as follows: when K=K1, V0=V d ; When K=K2, V0=V b +G0.

[0019] Preferably, the method for setting the threshold voltage G0 in step 2 is as follows: when the current state of charge is in the range of 0 to 30%, the threshold voltage G0 can be set to a; when the current state of charge is in the range of 30 to 60%, the threshold voltage G0 can be set to b; when the current state of charge is in the range of 60% to 100%, the threshold voltage G0 can be set to c; and a>b>c.

[0020] The beneficial effects of the present invention are as follows: The present invention obtains information such as the required voltage and current of the vehicle end in real time through a high-power DC charging system, dynamically calculates the required number of power modules in combination with the current power battery voltage, and optimizes the output voltage using an algorithm, thereby improving the utilization efficiency of the power module, reducing power loss, and saving electricity costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a control flow diagram of the method of the present invention;

[0022] Figure 2 It is a schematic diagram of the hardware structure involved in the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0024] The high-power DC charging system contains N power modules with a power of P (unit: W). The vehicle-side required voltage V can be obtained based on the charging protocol interaction information. d (Unit: V) and vehicle-side demand current I d (Unit: A), currently most high-power DC charging systems use a required voltage V d To calculate the number of power modules K1 required, in this case the output voltage V0 of the high-power DC charging system is V d (Unit: V), as shown in Formula 1 below:

[0025]

[0026] V0=V d

[0027] Often the current power battery voltage of an electric vehicle is higher than the vehicle-side required voltage V d If the number of power modules K1 is selected, more power loss will be caused, especially after charging for a period of time.

[0028] In view of the problem of large power loss in the above charging method, combined with the existing charging system, the high-power DC charging system measures the current power battery voltage V through the meter during the charging process. b (Unit: V), according to the current power battery voltage V b Optimize the number of power modules required and calculate the number of power modules K0 (unit: pcs) required for current charging. At this time, the output voltage V0 of the high-power DC charging system is V b

[0029] The number of power modules K0 required for current charging is calculated using Formula 2:

[0030]

[0031] In the actual charging process, the vehicle-side voltage V d May be much larger than the current power battery voltage V b At this time, if we continue to use the vehicle-side required voltage V dTo calculate the number of power modules K1 required, it must be greater than the current power battery voltage V b The number of power modules required is calculated as K0. In this scenario, the output voltage V0 required by the vehicle is actually the same as the current power battery voltage V b Equal, at this time use the current power battery voltage V b Calculating the number of power modules required can greatly improve the utilization efficiency of the modules and reduce the ineffective power loss of the modules.

[0032] In order to compensate for the voltage loss in the charging circuit and prevent voltage backflow, the above formula 2 is optimized and a threshold voltage G0 (unit: V) is added on this basis. For example, the threshold voltage can be set to 10V. At this time, the output voltage V0 (unit: V) of the high-power DC charging system satisfies: V0 = V b +G0, the number of power modules K2 required for current charging is calculated as follows:

[0033] Formula 3:

[0034]

[0035] At present, the domestic high-power DC charging system and the BMS of electric vehicles use the GB / T27930 communication protocol for information exchange during the charging process. During the charging process, the vehicle-side demand voltage V is dynamically interacted according to the protocol. d 、Vehicle-side demand current I d , the current power battery voltage V dynamically measured by the DC charging system b , the threshold voltage G0 corresponding to different charge states, the optimal number of power modules K and the optimal output voltage V0 can be calculated. As the communication process of GB / T27930 proceeds, the internal power module of the high-power DC charging system is finally adjusted according to the vehicle-side demand current I d And the optimal output voltage V0 is actually output.

[0036] During the charging process of electric vehicles, the vehicle-side demand current I dIn the real-time update interactive state, different threshold voltages G0 are set according to the current state of charge. The setting method of the threshold voltage G0 is as follows: when the current state of charge is in the range of 0 to 30%, the threshold voltage G0 can be set to a; when the current state of charge is in the range of 30 to 60%, the threshold voltage G0 can be set to b; when the current state of charge is in the range of 60% to 100%, the threshold voltage G0 can be set to c; and a>b>c (for example, when the current state of charge is in the range of 0 to 30%, the threshold voltage G0 can be set to 15V, and when the current state of charge is in the range of 30 to 60%, the threshold voltage G0 can be set to Set to 10V, the current state of charge is in the range of 60% to 100%, and the threshold voltage G0 can be set to 5V). When the corresponding state of charge is reached, the required number of power modules K2 and the corresponding output voltage V0 are calculated according to the threshold voltage G0 corresponding to the current state of charge, and then compared with the required number of power modules K1 calculated using formula 2. The one with the smaller number of required modules is the optimal number of power modules K, that is, K=MIN(K1, K2). The high-power DC charging system outputs according to the optimal number of power modules K and the output voltage V0 corresponding to K.

[0037] like Figure 2 As shown, the DC charging system includes N power modules, a main control system and other modules. The DC charging system and the electric vehicle exchange information and complete energy transmission through the charging protocol. The specific control method includes the following steps:

[0038] Step 1: Obtain the vehicle-side required voltage V in the information flow parameters according to the protocol interaction d And vehicle-side demand current I d , according to formula 1, calculate the required number of power modules K1 and the output voltage V0 of the corresponding DC charging system,

[0039]

[0040] V0=V d

[0041] , where P is the power of a single power module;

[0042] Step 2: In order to compensate for the voltage loss in the charging circuit and prevent voltage backflow, the corresponding threshold voltage G0 is determined according to the current state of charge;

[0043] Step 3: Formula 3 calculates the number of power modules K2 and the output voltage V0 corresponding to K2, and the current power battery voltage V measured by the high-power DC charging system b , threshold voltage G0 and vehicle-side demand current I d According to formula 3, the required number of power modules K2 and the corresponding output voltage V0 are calculated:

[0044] V0=Vb +G0

[0045]

[0046] Step 4: Determine the number of power modules K1 and the number of power modules K2 and compare the two.

[0047] Step 5: Determine the optimal number of power modules K = MIN (K1, K2) and the corresponding output voltage V0. When K = K1, V0 = V d ; When K=K2, V0=V b +G0;

[0048] Step 6: Update the charging output voltage V0, adjust the number of power modules to K, and the charging output current I d Remain unchanged.

[0049] In summary, the charging method of the present invention can be based on the current power battery voltage V b The output voltage V0 is dynamically adjusted, and the number of working power modules is adjusted to the optimal value, so as to solve the problem of reduced utilization efficiency of power modules in the prior art. The output power of the modules can be fully utilized, and the power loss of the power modules in the high-power DC charging system is greatly reduced.

Claims

1. A control method for a DC charging system based on dynamic adjustment of battery voltage, wherein the DC charging system includes N power modules with a power of P, a main control system and other modules, and the DC charging system and the electric vehicle exchange information and complete energy transmission through a charging protocol, characterized in that: The following steps are included: Step 1: Obtain the vehicle-side required voltage V in the information flow parameters according to the protocol interaction d And vehicle-side demand current I d , calculate the required number of power modules K1 and the output voltage V0 of the corresponding DC charging system, V0=V d , Where P is the power of a single power module; Step 2: Determine the corresponding threshold voltage G0 according to the current state of charge; Step 3: Calculate the required number of power modules K2 and the output voltage V0 corresponding to K2 based on the threshold voltage G0; Step 4: Determine the number of power modules K1 and the number of power modules K2 and compare the two. Step 5: Determine the optimal number of power modules required K = MIN (K1, K2) and the corresponding output voltage V0; Step 6: Update the charging output voltage V0, adjust the number of power modules to K, and keep the charging output current I unchanged.

2. The DC charging system control method based on dynamic battery voltage adjustment according to claim 1, characterized in that: The number of power modules K2 required in step 3 and the output voltage V0 corresponding to K2 are calculated as follows: V0=V b +G Among them, V b is the current power battery voltage measured by the high-power DC charging system, G0 is the threshold voltage, I d is the vehicle-side demand current in the information flow, and P is the power of a single power module.

3. The DC charging system control method based on dynamic battery voltage adjustment according to claim 2, characterized in that: The value of the output voltage V0 corresponding to step 5 is as follows: When K = K1, V0 = V d ; When K=K2, V0=V b +G0.

4. The DC charging system control method based on dynamic battery voltage adjustment according to claim 1, characterized in that: The method for setting the threshold voltage G0 in step 2 is as follows: when the current state of charge is in the range of 0 to 30%, the threshold voltage G0 can be set to a; when the current state of charge is in the range of 30 to 60%, the threshold voltage G0 can be set to b; when the current state of charge is in the range of 60% to 100%, the threshold voltage G0 can be set to c; and a>b>c.

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