A non-isolated DCDC charging and discharging switching control method and system

Abstract

The present invention relates to the field of DCDC control technology, and specifically discloses a non-isolated DCDC charge-discharge switching control system and method, wherein the method comprises the following contents: taking charging as the positive direction, taking the smaller value of the output of the loop controller PI1 of the DC bus voltage outer loop and the loop controller PI2 of the battery voltage outer loop as the charging current instruction; obtaining the controller compensation voltage V through the loop controller PI3 of the current inner loop Comp , and the battery voltage sampling V Bat The sum is the system reference voltage V buckref ; Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck The technical solution of the present invention can realize rapid charging and discharging seamless switching and suppress voltage fluctuation and starting current impact.

Description

Technical Field

[0001] The present invention relates to the technical field of DCDC control, and in particular to a non-isolated DCDC charge-discharge switching control method and system. Background Art

[0002] Battery charging and discharging control of non-isolated bidirectional DC-DC converters plays a vital role in DC microgrids. The core task of this control system is to achieve efficient battery charging and discharging and maintain the stability of the DC bus voltage by regulating the flow of electrical energy.

[0003] In charging mode, the non-isolated bidirectional DC-DC converter transfers the electrical energy on the DC bus to the battery, raising the battery voltage to a preset value, and manages the charging speed and battery status through current control and voltage control to ensure the safety and efficiency of the charging process. In discharge mode, the converter releases the electrical energy in the battery to the DC bus to maintain the system's power supply requirements and prevent the grid from experiencing a voltage drop. Throughout the process, the control system needs to accurately adjust the converter's operating state to avoid overcharging, over-discharging, and other situations that may damage the battery life.

[0004] Due to the characteristics of the non-isolated structure, the converter usually has higher energy conversion efficiency and smaller size. However, this also means that during the charging and discharging process, especially when switching modes, problems such as voltage mutation and starting current shock may occur. If the switching process is not smooth enough, it may cause large fluctuations in the DC bus voltage, affecting the stability of the entire DC microgrid.

[0005] Therefore, the battery charge and discharge control of the non-isolated bidirectional DC-DC converter must have fast response capabilities to ensure seamless switching between charging and discharging modes while effectively suppressing voltage fluctuations and startup current shocks. Summary of the invention

[0006] One of the purposes of the present invention is to provide a non-isolated DCDC charge-discharge switching control system, which can achieve rapid charge-discharge seamless switching and suppress voltage fluctuations and startup current shocks.

[0007] In order to solve the above technical problems, this application provides the following technical solutions:

[0008] A non-isolated DCDC charge-discharge switching control system, comprising a control module, the control module comprising a DC bus voltage outer loop, a battery voltage outer loop, a minimum function and a current inner loop;

[0009] The DC bus voltage outer loop is used to obtain the DC bus voltage command V dcBusRef , and the DC bus voltage sampling V dcBus ; Calculate the DC bus voltage sampling VdcBus and DC bus voltage command V dcBusRef The difference Err1 is used as the DC bus voltage error. According to the DC bus voltage error Err1, the output current command I 1Ref ;

[0010] The battery voltage outer loop is used to obtain the battery constant charge voltage command V BatRef , and the battery voltage sampling V Bat ; Calculate the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference Err2 is used as the battery voltage error; according to the battery voltage error Err2, the output current command is I 2Ref ;

[0011] Take the smaller function to compare the current command I 1Ref With current command I 2Ref The smaller value is used as the charging current command I Ref ;

[0012] The current inner loop is used to calculate the charging current command I Ref With charging current sampling I buck The difference Err3; the controller compensation voltage V obtained according to Err3 Comp , V Comp With the battery voltage sampling V Bat The sum is the system reference voltage V buckref ; Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck .

[0013] Further, the DC bus voltage outer loop includes a loop controller PI1, the battery voltage outer loop includes a loop controller PI2, and the current inner loop includes a loop controller PI3;

[0014] The loop controller PI1 of the DC bus voltage outer loop is used to receive the DC bus voltage error Err1 and output the current command I 1Ref ;

[0015] The loop controller PI2 of the battery voltage outer loop is used to receive the battery voltage error Err2 and output the current command I 2Ref ;

[0016] The current loop controller PI3 of the current inner loop is used to receive the charging current instruction I Ref With charging current sampling I buck The difference Err3, the output controller compensation voltage V Comp .

[0017] Further, it also includes a DCDC conversion circuit;

[0018] The DCDC conversion circuit includes a high-voltage side capacitor C H , low voltage side capacitor C L , filter inductor L f , Switching device S buck and the switching device S boost ;

[0019] High voltage side capacitor C H One end of the switch device S buck One end of the switch device S buck The other end of the filter inductor L f One end of the filter inductor L f The other end is connected to the low voltage side capacitor C L One end of the low voltage side capacitor C L The other end is connected to the high voltage side capacitor C H The other end of the switch device S boost One end of the switch device S buck The other end of the switching device is connected to S boost The other end is connected to the low voltage side capacitor C L The other end is connected;

[0020] High voltage side capacitor C H One end is also connected to the positive electrode of the high-voltage side, and the high-voltage side capacitor C H The other end is also connected to the negative pole of the high voltage side;

[0021] Low voltage side capacitor C L One end is also connected to the positive electrode of the low voltage side and the low voltage side capacitor C L The other end is also connected to the negative pole of the low voltage side.

[0022] Furthermore, the switch device S buck The duty cycle is the low voltage side duty cycle d buck , switching device S boost The duty cycle is d boost ;d boost Equal to 1-d buck .

[0023] The second object of the present invention is to provide a non-isolated DCDC charge and discharge switching control method, including the following contents:

[0024] With charging as the positive direction, the smaller value of the output of the loop controller PI1 of the DC bus voltage outer loop and the loop controller PI2 of the battery voltage outer loop is taken as the charging current command;

[0025] The controller compensation voltage V obtained by the loop controller PI3 of the current inner loopComp , and the battery voltage sampling V Bat The sum is the system reference voltage V buckref ;

[0026] Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck .

[0027] Further, specifically including:

[0028] The DC bus voltage outer loop obtains the DC bus voltage command V dcBusRef , and the DC bus voltage sampling V dcBus ; The battery voltage outer loop obtains the battery constant charge voltage command V batRef , and the battery voltage sampling V bat ;

[0029] DC bus voltage outer loop calculation DC bus voltage sampling V dcBus and DC bus voltage command V dcBusRef The difference between the DC bus voltage error Err1 is obtained; the battery voltage outer loop calculates the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference between the two is the battery voltage error Err2.

[0030] The DC bus voltage error Err1 is input into the voltage loop controller PI1 of the DC bus voltage outer loop to obtain the current command I 1Ref ; Input the battery voltage error Err2 into the voltage loop controller PI2 of the battery voltage outer loop to obtain the current command I 2Ref；

[0031] The current command is I 1Ref and current command I 2Ref Input the smaller function to get the charging current command I Ref ; Among them, the charging current instruction I Ref Equal to current command - I 1Ref 、Current instruction II 2Ref The smaller value of I Ref When it is greater than 0, it will charge to the low voltage side, I Ref When it is less than 0, it discharges to the high voltage side;

[0032] The current inner loop obtains the charging current sampling I buck , calculate the charging current command I Ref With charging current sampling I buck The difference is Err3;

[0033] Input Err3 into the current loop controller PI3 of the current inner loop to obtain the controller compensation voltage V Comp ;

[0034] Calculate the controller compensation voltage V Comp With the battery voltage sampling V Bat The sum of the system reference voltage V buckref ;

[0035] Calculate the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus The quotient of the low voltage side duty cycle d is obtained. buck .

[0036] Furthermore, the low voltage side duty cycle d buck After the saturation module Sat of the input current inner loop is limited, the saturation module Sat outputs the final duty cycle.

[0037] Furthermore, the saturation upper limit and the saturation lower limit of the voltage loop controller PI2 are respectively ChargMax , -I DisChargMax ; Among them, the battery constant charge current I ChargMax is the maximum constant charge current requested by the low voltage side, and the battery discharge current I DisChargMax It is the maximum discharge current allowed on the low voltage side.

[0038] Furthermore, the saturation upper limit and the saturation lower limit of the current loop controller PI3 are CompMax and CompMin respectively.

[0039] Furthermore, the upper and lower limits of the saturation module Sat are D max , D min .

[0040] This solution takes charging as the positive direction (voltage reduction as positive), takes the smaller output value of the DC bus voltage outer loop controller and the battery voltage outer loop controller as the charging current command, and the system reference voltage (the output is the reference voltage on the low-voltage side) is obtained by summing the compensation voltage obtained by the current inner loop controller and the battery voltage sampling. Finally, the system reference voltage is divided by the DC bus voltage sampling to obtain the normalized low-voltage side duty cycle without the need for additional logical judgment.

[0041] Benefits include:

[0042] 1. It can realize seamless switching effect of battery charging and discharging;

[0043] 2. It can realize constant voltage and constant current charging, which effectively improves the traditional battery charging and discharging switching method based on logic judgment. This solution can realize faster charging and discharging switching in UPS or EPS application scenarios;

[0044] 3. In this solution, the DC bus voltage outer loop and the battery voltage outer loop share the current inner loop controller, which reduces the number of controllers and effectively alleviates the interrupt resources of the MCU;

[0045] 4. Taking charging as the positive direction and making the duty cycle of the low-voltage side dominant can avoid the overcurrent problem caused by the large duty cycle during the charging and discharging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a control block diagram of a non-isolated DCDC charge-discharge switching control system;

[0047] Figure 2 This is a schematic diagram of a DCDC conversion circuit in a non-isolated DCDC charge and discharge switching control system. DETAILED DESCRIPTION

[0048] The following is further described in detail through specific implementation methods:

[0049] Embodiment 1

[0050] A non-isolated DCDC charge-discharge switching control system of this embodiment includes a DCDC conversion circuit and a control module, such as Figure 2 As shown, the DCDC conversion circuit includes a high-voltage side capacitor C H , low voltage side capacitor C L , filter inductor L f , Switching device S buck and the switching device S boost .

[0051] High voltage side capacitor C H One end of the switch device S buck One end of the switch device S buck The other end of the filter inductor L f One end of the filter inductor L f The other end is connected to the low voltage side capacitor C L One end of the low voltage side capacitor C L The other end is connected to the high voltage side capacitor C H The other end of the switch device S boost One end of the switch device S buck The other end of the switching device is connected to S boost The other end is connected to the low voltage side capacitor C L The other end of the connection.

[0052] High voltage side capacitor C H One end is also connected to the positive electrode of the high-voltage side, and the high-voltage side capacitor C H The other end is also connected to the negative pole of the high voltage side;

[0053] Low voltage side capacitor CL One end is also connected to the positive electrode of the low voltage side and the low voltage side capacitor C L The other end is also connected to the negative electrode of the low voltage side. In this embodiment, the low voltage side is a battery pack.

[0054] Switching device S boost With S buck Specifically, the switching device S buck The duty cycle is the low voltage side duty cycle d buck , switching device S boost The duty cycle is d boost ;d boost Equal to 1-d buck , and set a certain dead zone. For example, the dead zone is set to 1% of the switching period.

[0055] like Figure 1 As shown, the control module includes a DC bus voltage outer loop 101 , a battery voltage outer loop 102 , a minimization function 104 and a current inner loop 103 .

[0056] The DC bus voltage outer loop includes loop controller PI1, the battery voltage outer loop includes loop controller PI2, and the current inner loop includes loop controller PI3. Any controller may be used here, for example, sliding mode control, fuzzy control, ADRC control, etc.

[0057] The DC bus voltage outer loop is used to obtain the DC bus voltage command V dcBusRef ; Also used to obtain the DC bus voltage sampling V dcBus ; Calculate the DC bus voltage sampling V dcBus and DC bus voltage command V dcBusRef The difference Err1 is used as the DC bus voltage error; the loop controller PI1 of the DC bus voltage outer loop is used to receive the DC bus voltage error Err1 and output a current command I 1Ref ;

[0058] The battery voltage outer loop is used to obtain the battery constant charge voltage command V BatRef ; Also used to obtain battery voltage sampling V Bat ; Calculate the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference Err2 is used as the battery voltage error; the loop controller PI2 of the battery voltage outer loop is used to receive the battery voltage error Err2 and output the current command I 2Ref ;

[0059] Take the smaller function to compare the current command I 1Ref With current command I 2Ref The smaller value is used as the charging current command I Ref ;

[0060] The current inner loop is used to calculate the charging current command I Ref With charging current sampling I buck The difference Err3 is input into the current loop controller PI3 of the current inner loop, and the controller compensation voltage V Comp , V Comp With the battery voltage sampling V Bat The sum is the system reference voltage V buckref ; Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck .

[0061] Based on the above non-isolated DCDC charge-discharge switching control system, this embodiment also provides a non-isolated DCDC charge-discharge switching control method, including the following contents:

[0062] With charging as the positive direction, the smaller value of the output of the loop controller PI1 of the DC bus voltage outer loop and the loop controller PI2 of the battery voltage outer loop is taken as the charging current command;

[0063] The controller compensation voltage V obtained by the loop controller PI3 of the current inner loop Comp , and the battery voltage sampling V Bat The sum is the system reference voltage V buckref ;

[0064] Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck .

[0065] Specific:

[0066] The DC bus voltage outer loop obtains the DC bus voltage command V dcBusRef , and the DC bus voltage sampling V dcBus ; DC bus voltage sampling V dcBus is the high voltage side capacitor C H The battery voltage outer loop obtains the battery constant charge voltage command V batRef , and the battery voltage sampling V bat ;Battery voltage sampling V bat is the low voltage side capacitor C L Voltage;

[0067] DC bus voltage outer loop calculation DC bus voltage sampling V dcBus and DC bus voltage command V dcBusRefThe difference between the DC bus voltage error Err1 is obtained; the battery voltage outer loop calculates the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference between the two is the battery voltage error Err2.

[0068] The DC bus voltage error Err1 is input into the voltage loop controller PI1 of the DC bus voltage outer loop to obtain the current command I 1Ref ; Input the battery voltage error Err2 into the voltage loop controller PI2 of the battery voltage outer loop to obtain the current command I 2Ref；电压环路控制器PI1 The saturation upper limit and lower limit of the voltage loop controller PI2 are I ChargMax , -I DisChargMax ; Among them, the battery constant charge current I ChargMax The maximum constant charge current requested by the non-isolated bidirectional DCDC low-voltage side (such as a battery pack), the battery discharge current I DisChargMax The maximum discharge current allowed on the low-voltage side of a non-isolated bidirectional DCDC (such as a battery pack);

[0069] The current command is I 1Ref and current command I 2Ref Input the smaller function to get the charging current command I Ref ;Charging current command I Ref Equal to current command - I 1Ref 、Current instruction II 2Ref的较小值，IRef When it is greater than 0, it will charge to the low voltage side, I Ref When it is less than 0, it discharges to the high voltage side.

[0070] The current inner loop obtains the charging current sampling I buck , I buck is the current sampling of the low-voltage side of the non-isolated bidirectional DCDC, with the current flowing to the low-voltage side being positive; in this embodiment, the charging current sampling I buck is the filter inductor L f Calculate the charging current command I Ref With charging current sampling I buck The difference is Err3;

[0071] Input Err3 into the current loop controller PI3 of the current inner loop to obtain the controller compensation voltage V Comp ; That is, the controller compensation voltage V Comp is the output of the current loop controller PI3; wherein the saturation upper limit and the saturation lower limit of the current loop controller PI3 are CompMax and CompMin respectively;

[0072] Calculate the controller compensation voltage V Comp With the battery voltage sampling V Bat The sum of the system reference voltage Vbuckref ;

[0073] Calculate the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus The quotient of the low voltage side duty cycle d is obtained. buck ; Low voltage side duty cycle d buck The switching device S buck duty cycle.

[0074] The low voltage side duty cycle d buck After the input saturation module Sat is limited, the saturation module Sat outputs the final duty cycle to control the switching device S buck action; among them, the upper and lower limits of the saturation module Sat are D max , D min .

[0075] This solution is for non-isolated bidirectional DCDC (one side is high voltage side, the other side is low voltage side), based on the duty cycle control of the low voltage side. The loop outputs the compensation voltage V on the low voltage side. Comp , plus the real sampling voltage V on the low voltage side Bat Feedforward, and finally obtain the duty cycle of the low-voltage side by division and normalization, which can realize smooth startup (boost startup or buck) in any direction of the non-isolated bidirectional DCDC topology without overshoot current.

[0076] During the discharge start process, assuming that the high-voltage side is unloaded, the DC bus voltage command V dcBusRef V is the battery constant charge voltage command batRef 1.5 times of the DC bus voltage sampling V dcBus The initial value is approximately equal to the battery voltage sampling V bat , the low-voltage side battery is connected normally, allowing full power charging and discharging, and the battery constant charging voltage command V batRef Greater than the battery voltage sampling V bat .

[0077] The DC bus voltage outer loop gets Err1<0, and the output I 1Ref <0; Err2 obtained by the battery voltage outer loop>0, the output I 2Ref >0 ； Take the I output of the small function Ref =I 1Ref ; V obtained by the current inner loop Comp <0 ，VbuckRef <V bat , d buck Gradually decreases from 1 to a stable state, d boost It gradually increases from 0 to a stable value.

[0078] During the charging start-up process, assuming that the low-voltage side is unloaded, the battery voltage sampling VBat is 0, the high-voltage side DC source is connected normally, and the DC bus voltage sampling V dcBus Greater than the DC bus voltage command sampling V dcBusRef , battery constant charge voltage command V batRef Less than DC bus voltage sampling V dcBus .

[0079] The DC bus voltage outer loop gets Err1>0, and the output I 1Ref >0; the battery voltage outer loop obtains Err2>0, the output I 2Ref >0 ； Take the I output of the small function Ref =min(I 1Ref ,I 2Ref)； VComp>0 obtained by the current inner loop, d buck Gradually increasing from 0, d boost Gradually decrease from 1.

[0080] In summary, whether it is the discharge start process or the charge start process, the dominant duty cycle d boost d buck They all start from 0 and increase slowly, and there will be no overcurrent problem during the startup process.

[0081] During normal charging and discharging, assuming that the high-voltage DC source is connected normally, the DC bus voltage command V dcBusRef V is the battery constant charge voltage command batRef 1.5 times of the low voltage side battery is connected normally, allowing full power charging and discharging, and the battery constant charging voltage command V batRef Greater than the battery voltage sampling V bat .

[0082] If the DC bus voltage sampling V dcBus <DC bus voltage command V dcBusRef , Err1<0, Err2>0, I 1Ref <0,I 2Ref >0 ， I Ref =I 1Ref , the DC bus voltage loop plays a leading role and the battery voltage loop is bypassed at this time.

[0083] If the DC bus voltage sampling V dcBus >DC bus voltage command V dcBusRef , Err1>0, Err2>0, I 1Ref >0,I 2Ref >0 ， I Ref =min(I 1Ref ,I 2Ref)，若 I 1Ref <I2Ref， The DC bus voltage loop plays a leading role, and the battery voltage loop is bypassed. 1Ref >I 2Ref， The DC bus voltage loop is bypassed, and the battery voltage loop plays a leading role. At this time, the battery is charged at a constant voltage.

[0084] In summary, during the normal charging and discharging process, because the current switching is continuously changing, the charging and discharging switching is continuous and non-inductive.

[0085] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or the priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A non-isolated DCDC charge-discharge switching control system, comprising a control module and a DCDC conversion circuit, characterized in that: The control module includes a DC bus voltage outer loop, a battery voltage outer loop, a minimization function and a current inner loop; The DC bus voltage outer loop is used to obtain the DC bus voltage command V dcBusRef , and the DC bus voltage sampling V dcBus ; Calculate the DC bus voltage sampling V dcBus and DC bus voltage command V dcBusRef The difference Err1 is used as the DC bus voltage error. According to the DC bus voltage error Err1, the output current command I 1Ref ; The battery voltage outer loop is used to obtain the battery constant charge voltage command V BatRef , and the battery voltage sampling V Bat ; Calculate the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference Err2 is used as the battery voltage error; according to the battery voltage error Err2, the output current command is I 2Ref ; Take the smaller function to compare the current command I 1Ref With current command I 2Ref The smaller value is used as the charging current command I Ref ; The current inner loop is used to calculate the charging current command I Ref With charging current sampling I buck The difference Err3; the controller compensation voltage V obtained according to Err3 Comp , V Comp With the battery voltage sampling V Bat The sum is the system reference voltage V buckref ; Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck ; The DCDC conversion circuit includes a switching device S buck and the switching device S boost , switching device S buck The duty cycle is the low voltage side duty cycle d buck , switching device S boost The duty cycle is d boost ;d boost Equal to 1-d buck .

2. The non-isolated DCDC charge-discharge switching control system according to claim 1, characterized in that: The DC bus voltage outer loop includes a loop controller PI1, the battery voltage outer loop includes a loop controller PI2, and the current inner loop includes a loop controller PI3; The loop controller PI1 of the DC bus voltage outer loop is used to receive the DC bus voltage error Err1 and output the current command I 1Ref ; The loop controller PI2 of the battery voltage outer loop is used to receive the battery voltage error Err2 and output the current command I 2Ref ; The current loop controller PI3 of the current inner loop is used to receive the charging current instruction I Ref With charging current sampling I buck The difference Err3, the output controller compensation voltage V Comp .

3. The non-isolated DCDC charge-discharge switching control system according to claim 2, characterized in that: The DCDC conversion circuit also includes a high-voltage side capacitor C H , low voltage side capacitor C L 、Filter inductor L f ; High voltage side capacitor C H One end of the switch device S buck One end of the switch device S buck The other end of the filter inductor L f One end of the filter inductor L f The other end is connected to the low voltage side capacitor C L One end of the low voltage side capacitor C L The other end is connected to the high voltage side capacitor C H The other end of the switch device S boost One end of the switch device S buck The other end of the switching device is connected to S boost The other end is connected to the low voltage side capacitor C L The other end is connected; High voltage side capacitor C H One end is also connected to the positive electrode of the high-voltage side, and the high-voltage side capacitor C H The other end is also connected to the negative pole of the high voltage side; Low voltage side capacitor C L One end is also connected to the positive electrode of the low voltage side and the low voltage side capacitor C L The other end is also connected to the negative pole of the low voltage side.

4. A non-isolated DCDC charge and discharge switching control method, characterized in that: It includes the following: Taking charging as the positive direction, the smaller value of the output of the loop controller PI1 of the DC bus voltage outer loop and the loop controller PI2 of the battery voltage outer loop is taken as the charging current command: The DC bus voltage outer loop obtains the DC bus voltage command V dcBusRef , and the DC bus voltage sampling V dcBus ; The battery voltage outer loop obtains the battery constant charge voltage command V batRef , and the battery voltage sampling V bat ; DC bus voltage outer loop calculation DC bus voltage sampling V dcBus and DC bus voltage command V dcBusRef The difference between the DC bus voltage error Err1 is obtained; the battery voltage outer loop calculates the battery constant charge voltage command V BatRef With the battery voltage sampling V Bat The difference is obtained to obtain the battery voltage error Err2; the DC bus voltage error Err1 is input into the voltage loop controller PI1 of the DC bus voltage outer loop to obtain the current command I 1Ref ; Input the battery voltage error Err2 into the voltage loop controller PI2 of the battery voltage outer loop to obtain the current command I 2Ref ; The controller compensation voltage V is obtained by the charging current command through the loop controller PI3 of the current inner loop. Comp , and the battery voltage sampling V Bat The sum is the system reference voltage V buckref ; Set the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus , and obtain the normalized low voltage side duty cycle d buck ; The DCDC conversion circuit also includes a switching device S buck and the switching device S boost , switching device S buck The duty cycle is the low voltage side duty cycle d buck , switching device S boost The duty cycle is d boost ;d boost Equal to 1-d buck .

5. The non-isolated DCDC charge-discharge switching control method according to claim 4, characterized in that: Specifically include: The current command is I 1Ref and current command I 2Ref Input the smaller function to get the charging current command I Ref ; Among them, the charging current instruction I Ref Equal to current command - I 1Ref 、Current instruction II 2Ref The smaller value of I Ref When it is greater than 0, it will charge to the low voltage side, I Ref When it is less than 0, it discharges to the high voltage side; The current inner loop obtains the charging current sampling I buck , calculate the charging current command I Ref With charging current sampling I buck The difference is Err3; Input Err3 into the current loop controller PI3 of the current inner loop to obtain the controller compensation voltage V Comp ; Calculate the controller compensation voltage V Comp With the battery voltage sampling V Bat The sum of the system reference voltage V buckref ; Calculate the system reference voltage V buckref Divide by the DC bus voltage sample V dcBus The quotient of the low voltage side duty cycle d is obtained. buck .

6. The non-isolated DCDC charge-discharge switching control method according to claim 5, characterized in that: It also includes the low voltage side duty cycle d buck After the saturation module Sat of the input current inner loop is limited, the saturation module Sat outputs the final duty cycle.

7. The non-isolated DCDC charge-discharge switching control method according to claim 6, characterized in that: The saturation upper limit and the saturation lower limit of the voltage loop controller PI2 are respectively ChargMax , -I DisChargMax ; Among them, the battery constant charge current I ChargMax is the maximum constant charge current requested by the low voltage side, and the battery discharge current I DisChargMax It is the maximum discharge current allowed on the low voltage side.

8. The non-isolated DCDC charge-discharge switching control method according to claim 7, characterized in that: The saturation upper limit and the saturation lower limit of the current loop controller PI3 are CompMax and CompMin respectively.

9. The non-isolated DCDC charge-discharge switching control method according to claim 8, characterized in that: The upper and lower limits of the saturation module Sat are D max , D min .

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