A method for adjusting charge and discharge power, a DC converter system

Abstract

The present invention relates to a charge-discharge power regulation method and a DC converter system. In the system, a power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the grid connection point, and an AC load is connected to the grid connection point. Among them, the charge-discharge state of the DC converter is determined, and according to the charge-discharge state of the DC converter, either the sum of the charging power of the DC converter and the operating power of the AC load is compared with the grid connection point input power limit value, or the difference between the discharging power of the DC converter and the operating power of the AC load is compared with the grid connection point output power limit value. According to the comparison result, the output power reference values of the DC converter and the inverter are adjusted and controlled. The present application can not only improve the charge-discharge efficiency of the power battery, but also reduce the impact on the power grid stability during the charge-discharge process of the power battery.

Description

Technical Field

[0001] The present invention relates to the technical field of power regulation control, and particularly relates to a method for regulating charging and discharging power during AC-DC charging and a DC converter system. Background Art

[0002] With the popularization of electric vehicles, their charging problems have attracted more and more attention. DC charging piles can directly provide high-power direct current for electric vehicle batteries, greatly shortening the charging time, which is particularly important for long-distance travel and emergencies that require rapid charging. At present, the charging pile technology is in a period of rapid change. Due to the advantage of fast charging, DC fast charging technology is gradually replacing traditional AC slow charging technology and entering thousands of households. However, DC charging piles configured for homes pose higher requirements for household power distribution systems, resulting in the following technical problems:

[0003] (1) To meet the high-power charging requirements of DC charging piles, it is necessary to increase the current-carrying capacity of the household power distribution system;

[0004] (2) When the power grid capacity is weak, high-power charging may cause the voltage at the grid connection point to drop, triggering undervoltage shutdown and affecting charging continuity;

[0005] (3) The change of AC load will cause the charging power to be unstable, reducing the charging efficiency of electric vehicles.

[0006] These problems jointly limit the efficient use of DC charging piles and affect the charging experience of electric vehicle users, making it an urgent problem to be solved in this field how to achieve efficient, fast, and real-time charging of charging piles. Summary of the Invention

[0007] A main object of the present invention is to overcome at least one of the above defects, and to provide a method for regulating charging and discharging power and a DC converter system, which can not only improve the charging and discharging efficiency of power batteries, but also reduce the impact on the stability of the power grid during the charging and discharging process of power batteries.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] The present invention provides a method for regulating charging and discharging power. A power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected by a DC bus. The connection point between the inverter and the power grid is the grid connection point, and an AC load is connected to the grid connection point. Among them, the charging and discharging state of the DC converter is determined.

[0010] When the DC converter is in the charging state, compare the sum of the charging power of the DC converter and the operating power of the AC load with the grid connection point input power limit value, and adjust and control the output power reference values of the converter and the DC converter according to the comparison result;

[0011] When the DC converter is in the discharging state, compare the difference between the discharging power of the DC converter and the operating power of the AC load with the grid connection point output power limit value, and adjust and control the output power reference values of the DC converter and the converter according to the comparison result.

[0012] According to one embodiment of the present invention, when the DC converter is in the charging state,

[0013] If the sum of the charging power of the DC converter and the operating power of the AC load is greater than the grid connection point input power limit value, control to calculate and determine the output power reference value of the converter with the difference between the grid connection point input power limit value and the real-time power of the grid connection point as the input of the regulator, and control to calculate and determine the output power reference value of the DC converter with the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator.

[0014] According to one embodiment of the present invention, when the DC converter is in the charging state,

[0015] If the sum of the charging power of the DC converter and the operating power of the AC load is less than the grid connection point input power limit value, control to calculate and determine the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and control the DC converter to adjust the operation of the DC converter with the DC converter charging power limit value as the output power reference value of the DC converter.

[0016] According to one embodiment of the present invention, when the DC converter is in the charging state, the converter bus voltage reference value is greater than the DC converter bus voltage reference value.

[0017] According to one embodiment of the present invention, when the DC converter is in the discharging state,

[0018] If the difference between the discharging power of the DC converter and the operating power of the AC load is greater than the grid connection point output power limit value, control to calculate and determine the output power reference value of the converter with the difference between the grid connection point output power limit value and the real-time power of the grid connection point as the input of the regulator, and control to calculate and determine the output power reference value of the DC converter with the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator.

[0019] According to one embodiment of the present invention, when the DC converter is in the discharging state,

[0020] If the difference between the discharging power of the DC converter and the operating power of the AC load is less than the output power limit value of the grid connection point, control is performed to calculate and determine the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and the DC converter adjusts its operation with the DC converter discharging power limit value as the output power of the DC converter.

[0021] According to one embodiment of the present invention, when the DC converter is in the discharging state, the converter bus voltage reference value is less than the DC converter bus voltage reference value.

[0022] In particular, the present invention provides a DC converter system, wherein the system executes the charge and discharge power regulation method as described above to regulate the charge and discharge power between the power battery and the power grid.

[0023] According to one embodiment of the present invention, the DC converter system includes a DC converter, a converter, a controller, and a power acquisition device. The power battery is connected to the power grid through the DC converter and the converter. The DC converter and the converter are connected through a DC bus. The connection point between the converter and the power grid is the grid connection point. The AC load is connected to the grid connection point. The input end of the power acquisition device is connected to the grid connection point, and the output end of the power acquisition device is connected to the input end of the controller. The controller is connected to both the DC converter and the converter. The controller adjusts and controls the output power reference values of the DC converter and the converter according to the charge and discharge state of the DC converter and the input and output power of the grid connection point.

[0024] According to one embodiment of the present invention, the controller includes a converter control unit and a DC converter control unit. The converter control unit is connected to the converter, and the DC converter control unit is connected to the DC converter.

[0025] According to one embodiment of the present invention, the converter control unit includes a converter power upper limit control module, a converter power lower limit control module, and a converter bus voltage control module. The converter power upper limit control module takes the difference between the grid connection point output power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the converter power upper limit control module after passing through the regulator. The converter power lower limit control module takes the difference between the grid connection point input power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the converter power lower limit control module after passing through the regulator. The converter bus voltage control module takes the difference between the converter bus voltage reference value and the DC bus real-time voltage as the input of the regulator, and obtains the output of the converter bus voltage control module after passing through the regulator. The output of the converter bus voltage control module generates an output power reference value for adjusting and controlling the converter after being limited.

[0026] According to one embodiment of the present invention, the DC converter control unit includes a DC converter bus voltage control module. The DC converter bus voltage control module takes the difference between the DC converter bus voltage reference value and the DC bus real-time voltage as the input of the regulator, and obtains the output of the DC converter bus voltage control module after passing through the regulator. The output of the DC converter bus voltage control module generates an output power reference value for adjusting and controlling the DC converter after being limited.

[0027] Compared with the prior art, the advantages and beneficial effects of the charge and discharge power regulation method and the DC converter system of this patent application of the present invention are as follows:

[0028] The charge and discharge power regulation method of this application can overcome the influence of high-power charging on the grid stability, as well as problems such as energy scheduling delay, low charging efficiency, and power control fluctuation caused by the master-slave communication delay, by monitoring the grid connection point power and the DC bus voltage in real time, combining with the charge and discharge state of the DC converter connected to the power battery, and dynamically adjusting the charge and discharge power of the DC converter using a closed-loop control system. While improving the DC charge and discharge efficiency, it can ensure the working stability of the DC converter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Some specific embodiments of the present invention will be described in detail hereinafter with reference to the drawings in an exemplary but not restrictive manner. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0030] Figure 1 is a flowchart of the charge and discharge power regulation method according to an embodiment of the present invention;

[0031] Figure 2It is a schematic structural diagram of a DC converter system according to an embodiment of the present invention;

[0032] Figure 3 It is a schematic module structure diagram of a converter control unit according to an embodiment of the present invention;

[0033] Figure 4 It is a schematic module structure diagram of a DC converter control unit according to an embodiment of the present invention;

[0034] Figure 5 It is a schematic diagram of the energy flow relationship of the charge-discharge power regulation method according to an embodiment of the present invention in the charging scenario;

[0035] Figure 6 It is a schematic diagram of the energy flow relationship of the charge-discharge power regulation method according to an embodiment of the present invention in the discharging scenario. Detailed implementation manners

[0036] Next, the technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Embodiment 1:

[0039] This embodiment describes a charge-discharge power regulation method for a DC converter system. The structure of the DC converter system is as Figure 2 shown. The power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the grid connection point, and an AC load is connected to the grid connection point. The working process of the method is as Figure 1 shown. Among them, the charge-discharge state of the DC converter is determined.

[0040] When the DC converter is in the charging state, the sum of the charging power of the DC converter and the working power of the AC load is compared with the grid connection point input power limit value, and the output power reference values of the inverter and the DC converter are adjusted and controlled according to the comparison result;

[0041] When the DC converter is in the discharging state, the difference between the discharging power of the DC converter and the working power of the AC load is compared with the grid connection point output power limit value, and the output power reference values of the DC converter and the inverter are adjusted and controlled according to the comparison result.

[0042] The method described in this embodiment can overcome the problems such as the impact of high-power charging on the grid stability, the energy scheduling delay caused by the master-slave communication delay, the low charging efficiency, and the power control fluctuation. By dynamically adjusting the charging and discharging power of the DC converter through real-time monitoring of the grid connection point power and the DC bus voltage, and combining with the charging and discharging state of the DC converter connected to the power battery, it can ensure the working stability of the DC converter system while improving the DC charging and discharging efficiency.

[0043] Hereinafter, according to whether the DC converter is in the charging state or the discharging state, combining the working power of the DC converter and the working power of the AC load, compare the sum or difference of the two with the power limit value of the input or output of the grid connection point, and determine the working mode and power of the converter and the DC converter based on the comparison result.

[0044] In one embodiment, when the DC converter is in the charging state, the reference value of the converter bus voltage is greater than the reference value of the DC converter bus voltage, and the control logic is as follows:

[0045] If the sum of the charging power of the DC converter and the working power of the AC load is greater than the input power limit value of the grid connection point, control to calculate the reference value of the output power of the converter by taking the difference between the input power limit value of the grid connection point and the real-time power of the grid connection point as the input of the regulator, and control to calculate the reference value of the output power of the DC converter by taking the difference between the reference value of the DC converter bus voltage and the real-time voltage of the DC bus as the input of the regulator;

[0046] If the sum of the charging power of the DC converter and the working power of the AC load is less than the input power limit value of the grid connection point, control to calculate the reference value of the output power of the converter by taking the difference between the reference value of the converter bus voltage and the real-time voltage of the DC bus as the input of the regulator, and control the DC converter to adjust the working of the DC converter by taking the charging power limit value of the DC converter as the reference value of the output power of the DC converter;

[0047] If the sum of the charging power of the DC converter and the working power of the AC load is equal to the input power limit value of the grid connection point, no regulation is performed.

[0048] In one embodiment, when the DC converter is in the discharging state, the reference value of the converter bus voltage is less than the reference value of the DC converter bus voltage, and the control logic is as follows:

[0049] If the difference between the discharge power of the DC converter and the operating power of the AC load is greater than the grid connection point output power limit value, control is performed to calculate and determine the output power reference value of the converter with the difference between the grid connection point output power limit value and the real-time power of the grid connection point as the input of the regulator, and control is performed to calculate and determine the output power reference value of the DC converter with the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator;

[0050] If the difference between the discharge power of the DC converter and the operating power of the AC load is less than the grid connection point output power limit value, control is performed to calculate and determine the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and the DC converter adjusts its operation with the DC converter discharge power limit value as the output power of the DC converter;

[0051] If the difference between the discharge power of the DC converter and the operating power of the AC load is equal to the grid connection point output power limit value, no regulation is performed.

[0052] The above converter bus voltage reference value and the DC converter bus voltage reference value are related to the DC bus voltage request value and the state of the DC converter. The expression is:

[0053]

[0054]

[0055] Wherein is the DC bus voltage request value, and are the adjustment amounts for making the converter bus voltage reference value and the DC converter bus voltage reference value satisfy the DC bus voltage request value. and are both greater than 0. When the DC converter is in the charging state, > ; when the DC converter is in the discharging state, < . That is, corresponding to the previous text, when the DC converter is in the charging state, the converter bus voltage reference value is greater than the DC converter bus voltage reference value; when the DC converter is in the discharging state, the converter bus voltage reference value is less than the DC converter bus voltage reference value.

[0056] As for the DC bus voltage request value it is composed of the converter DC bus request value and the DC converter bus request value is determined by the larger value. The expression is:

[0057]

[0058] where the converter DC bus request value is determined by the rated voltage on the grid side, and its expression is:

[0059]

[0060] where is the rated voltage on the grid side, is the adjustment amount for the converter to work properly, generally a constant greater than 0.

[0061] The DC converter bus request value is then determined by the voltage of the power battery, and its expression is:

[0062]

[0063] where is the voltage of the power battery, can be positive or negative. Generally, for a buck DC converter, is positive; for a boost DC converter, is negative; for a boost-buck DC converter, when the DC converter works in boost mode, is negative, and when it works in buck mode, is positive.

[0064] In the above two implementation manners, the output power is calculated by using a regulator. The regulator used can be a common PI regulator, PD regulator, adaptive regulator, etc., and the input of the control regulator is adjusted to calculate the corresponding power value.

[0065] The input and output power of the converter has upper and lower limits. Among them: the upper limit of the converter power is the difference between the output power limit value at the grid connection point and the real-time power at the grid connection point, which is used as the input of the regulator, and the upper limit of the converter power is obtained through the regulator. The output power limit value at the grid connection point is the maximum power limit value fed to the grid; the lower limit of the converter power is the difference between the input power limit value at the grid connection point and the real-time power at the grid connection point, which is used as the input of the regulator, and the lower limit of the converter power is obtained through the regulator. The input power limit value at the grid connection point is the maximum power limit value absorbed from the grid. The control is based on the converter bus voltage reference value The difference from the real-time DC bus voltage is used as the input of the regulator to calculate and determine the output power reference value of the converter When doing so, limit processing is performed with the calculated upper limit of the converter power and the lower limit of the converter power to obtain the final output power reference value of the converter .

[0066] Using the DC converter bus voltage reference value and the difference from the real-time DC bus voltage as the input of the regulator, the output power of the DC converter is obtained after passing through the regulator This output power of the DC converter also undergoes limit processing by the upper limit of the DC converter power and the lower limit of the DC converter power to generate the output power value for adjusting and controlling the DC converter . Among them, the upper limit of the DC converter power is the maximum charging power limit value of the DC converter, that is, the maximum power limit value fed to the power battery; the lower limit of the DC converter power is the maximum discharge power limit of the DC converter, that is, the maximum power limit value absorbed from the power battery

[0067] The upper limit of the DC converter power is the minimum value among the rated charging power of the DC converter, the operating derating power of the DC converter (such as temperature derating, etc.) and the charging request power of the power battery. The charging request power of the power battery refers to the maximum power that the battery can accept during charging, and this value is determined through the communication between the electric vehicle and the DC converter; the lower limit of the DC converter power is the minimum value among the rated discharge power of the DC converter, the operating derating power of the DC converter (such as temperature derating, etc.) and the discharge request power of the power battery. The discharge request power of the power battery refers to the maximum power that the power battery can accept during discharge, and this value is determined through the communication between the equipment to which the power battery belongs and the DC converter

[0068] Embodiment 2:

[0069] This embodiment describes a DC converter system, such as Figure 2As shown in the figure, the DC converter system includes a DC converter, an inverter, a controller, and a power acquisition device. The power battery is connected to the power grid through the DC converter and the inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the grid connection point. The AC load is connected to the grid connection point. The input end of the power acquisition device is connected to the grid connection point, and the output end of the power acquisition device is connected to the input end of the controller. The controller is connected to both the DC converter and the inverter. The controller adjusts and controls the output power reference values of the DC converter and the inverter according to the charge and discharge state of the DC converter and the input and output power of the grid connection point.

[0070] Among them, the DC converter system of this embodiment executes the charge and discharge power adjustment method described in Embodiment 1, and is used to adjust the charge and discharge power between the power battery and the power grid.

[0071] In one embodiment, the controller includes an inverter control unit and a DC converter control unit. The inverter control unit is connected to the inverter, and the DC converter control unit is connected to the DC converter.

[0072] Specifically, as Figure 3 shown, the inverter control unit includes an inverter power upper limit control module, an inverter power lower limit control module, and an inverter bus voltage control module. The inverter power upper limit control module uses the difference between the grid connection point output power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the inverter power upper limit control module after passing through the regulator; the inverter power lower limit control module uses the difference between the grid connection point input power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the inverter power lower limit control module after passing through the regulator; the inverter bus voltage control module uses the difference between the inverter bus voltage reference value and the DC bus real-time voltage as the input of the regulator, and obtains the output of the inverter bus voltage control module after passing through the regulator . The output of the inverter bus voltage control module generates an output power reference value for adjusting and controlling the inverter after being subjected to amplitude limiting processing .

[0073] As Figure 4 shown, the DC converter control unit includes a DC converter bus voltage control module. The DC converter bus voltage control module uses the difference between the DC converter bus voltage reference value and the DC bus real-time voltage The difference is used as the input of the regulator, and after passing through the regulator, the output of the DC converter bus voltage control module is obtained , the output of the DC converter bus voltage control module After being limited, it generates an output power reference value for adjusting and controlling the DC converter .

[0074] The charge and discharge power regulation method and the DC converter system of this application dynamically adjust the charge and discharge power of the DC converter by real-time monitoring of the grid connection point power and the DC bus voltage, and utilize a closed-loop control system. The specific implementation steps are as follows:

[0075] (1) Data acquisition: Real-time collect the grid connection point power and DC bus voltage data, and input the collected power and voltage data into the controller;

[0076] (2) Controller adjustment: The controller dynamically adjusts the controller state according to the charge and discharge power of the DC converter, the AC load power, and the grid connection point input and output power limits to determine the output power reference values of the converter and the DC converter;

[0077] (3) Power control: Respectively input the calculated output power reference values of the converter and the DC converter into the power control modules in the converter and the DC converter. Each power control module generates a PWM waveform to precisely control the output power of the converter and the DC converter.

[0078] Working example 1: Charging scenario

[0079] In the charging scenario, energy flows from the DC bus through the DC converter into the power battery, and at this time the power battery is in the charging state. The energy of the DC bus comes from the power grid, and the power grid energy flows into the DC bus through the converter. The energy flow direction at this time is as Figure 5 shown.

[0080] When the sum of the charging power of the DC converter and the AC load power is greater than the grid connection point input power limit, the controller is in state one. It controls to use the difference between the grid connection point input power limit value and the real-time power of the grid connection point as the input of the regulator to calculate and determine the output power reference value of the converter, and controls to use the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator to calculate and determine the output power reference value of the DC converter. That is to say, the power reference value of the converter is controlled by the converter power lower limit control module, and the power reference value of the DC converter is controlled by the DC converter bus voltage control module. At this time, the intermediate DC bus voltage is controlled by the DC converter.

[0081] When the sum of the charging power of the DC converter and the AC load power is less than the grid connection point input power limit, the controller is in State 2, and controls to calculate and determine the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and controls the DC converter to adjust the operation of the DC converter with the DC converter charging power limit value as the output power reference value of the DC converter. That is to say, the converter bus voltage control module controls the power reference value of the converter, and the power upper limit control module of the DC converter controls the power reference value of the DC bus. At this time, the intermediate DC bus voltage is controlled by the converter.

[0082] Working Example 2: Discharge Scenario

[0083] In the discharge scenario, energy flows from the power battery through the DC converter into the DC bus, and at this time the power battery is in the discharge state. The energy on the DC bus can be output to the grid through the converter or supply power to the AC load. The energy flow direction at this time is as Figure 6 shown.

[0084] When the difference between the discharge power of the DC converter and the AC load power is greater than the grid connection point output power limit, the controller is in State 3, and controls to calculate and determine the output power reference value of the converter with the difference between the grid connection point output power limit value and the real-time power of the grid connection point as the input of the regulator, and controls to calculate and determine the output power reference value of the DC converter with the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator. That is to say, the power upper limit control module of the converter controls the power reference value of the converter, and the bus voltage control module of the DC converter controls the power reference value of the DC converter. At this time, the intermediate DC bus voltage is controlled by the DC converter.

[0085] When the difference between the discharge power of the DC converter and the AC load power is less than the grid connection point output power limit, the controller is in State 4, and controls to calculate and determine the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and the DC converter adjusts the operation of the DC converter with the DC converter discharge power limit value as the output power of the DC converter. That is to say, the converter bus voltage control module controls the power reference value of the converter, and the power lower limit control module of the DC converter controls the power reference value of the DC bus. At this time, the intermediate DC bus voltage is controlled by the converter.

[0086] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A charge-discharge power regulation method, where a power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the point of common coupling (PCC), and an AC load is connected to the PCC. It is characterized in that, Determine the charge-discharge state of the DC converter. When the DC converter is in the charging state, compare the sum of the charging power of the DC converter and the operating power of the AC load with the grid connection point input power limit value. If the sum of the charging power of the DC converter and the operating power of the AC load is greater than the grid connection point input power limit value, control to calculate the output power reference value of the converter with the difference between the grid connection point input power limit value and the real-time power of the grid connection point as the input of the regulator, and control to calculate the output power reference value of the DC converter with the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator. The grid connection point input power limit value is the maximum power absorption limit value from the grid. When the DC converter is in the discharging state, compare the difference between the discharging power of the DC converter and the operating power of the AC load with the grid connection point output power limit value, and adjust and control the output power reference values of the DC converter and the converter according to the comparison result.

2. The charge and discharge power adjustment method according to claim 1, wherein When the DC converter is in the charging state, the converter bus voltage reference value is greater than the DC converter bus voltage reference value.

3. A charge and discharge power regulation method, where a power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the point of common coupling (PCC), and an AC load is connected to the PCC. It is characterized in that, Determine the charge-discharge state of the DC converter. When the DC converter is in the charging state, compare the sum of the charging power of the DC converter and the operating power of the AC load with the grid connection point input power limit value. If the sum of the charging power of the DC converter and the operating power of the AC load is less than the grid connection point input power limit value, control to calculate the output power reference value of the converter with the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator, and control the DC converter to adjust its operation with the DC converter charging power limit value as the output power reference value of the DC converter. The grid connection point input power limit value is the maximum power absorption limit value from the grid. When the DC converter is in the discharging state, compare the difference between the discharging power of the DC converter and the operating power of the AC load with the grid connection point output power limit value, and adjust and control the output power reference values of the DC converter and the converter according to the comparison result.

4. The charge and discharge power adjustment method according to claim 3, characterized in that When the DC converter is in the charging state, the converter bus voltage reference value is greater than the DC converter bus voltage reference value.

5. A charge and discharge power regulation method, where a power battery is connected to the power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the point of common coupling (PCC), and an AC load is connected to the PCC. It is characterized in that, Determine the charge-discharge state of the DC converter. When the DC converter is in the charging state, compare the sum of the charging power of the DC converter and the operating power of the AC load with the grid connection point input power limit value, and adjust and control the output power reference values of the DC converter and the converter according to the comparison result. When the DC converter is in the discharging state, compare the difference between the discharging power of the DC converter and the operating power of the AC load with the grid connection point output power limit value. If the difference between the discharging power of the DC converter and the operating power of the AC load is greater than the grid connection point output power limit value, control to use the difference between the grid connection point output power limit value and the real-time power of the grid connection point as the input of the regulator to calculate and determine the output power reference value of the converter, and control to use the difference between the DC converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator to calculate and determine the output power reference value of the DC converter. The grid connection point output power limit value is the maximum power limit value fed to the power grid.

6. The charge and discharge power adjustment method according to claim 5, wherein When the DC converter is in the discharging state, the converter bus voltage reference value is less than the DC converter bus voltage reference value.

7. A charge and discharge power regulation method, wherein a power battery is connected to a power grid through a DC converter and an inverter. The DC converter and the inverter are connected through a DC bus. The connection point between the inverter and the power grid is the grid connection point, and an AC load is connected to the grid connection point. It is characterized in that, Determine the charge-discharge state of the DC converter. When the DC converter is in the charging state, compare the sum of the charging power of the DC converter and the operating power of the AC load with the grid connection point input power limit value, and adjust and control the output power reference values of the DC converter and the converter according to the comparison result. When the DC converter is in the discharging state, compare the difference between the discharging power of the DC converter and the operating power of the AC load with the grid connection point output power limit value. If the difference between the discharging power of the DC converter and the operating power of the AC load is less than the grid connection point output power limit value, control to use the difference between the converter bus voltage reference value and the real-time voltage of the DC bus as the input of the regulator to calculate and determine the output power reference value of the converter, and the DC converter adjusts its operation with the DC converter discharging power limit value as the output power of the DC converter. The grid connection point output power limit value is the maximum power limit value fed to the power grid.

8. The charge and discharge power adjustment method according to claim 7, wherein When the DC converter is in the discharging state, the converter bus voltage reference value is less than the DC converter bus voltage reference value.

9. A DC converter system, characterized in that, The system executes the charge-discharge power regulation method according to any one of claims 1 to 8, and is used to regulate the charge-discharge power between the power battery and the power grid.

10. The DC converter system according to claim 9, characterized in that, The DC converter system includes a DC converter, a converter, a controller, and a power acquisition device. The power battery is connected to the power grid through the DC converter and the converter. The DC converter and the converter are connected by a DC bus. The connection point between the converter and the power grid is the grid connection point. The AC load is connected to the grid connection point. The input end of the power acquisition device is connected to the grid connection point, and the output end of the power acquisition device is connected to the input end of the controller. The controller is connected to both the DC converter and the converter. The controller adjusts and controls the output power reference values of the DC converter and the converter according to the charge-discharge state of the DC converter and the input-output power of the grid connection point.

11. The DC converter system according to claim 10, wherein The controller includes a converter control unit and a DC converter control unit. The converter control unit is connected to the converter, and the DC converter control unit is connected to the DC converter.

12. The DC converter system according to claim 11, wherein The converter control unit includes a converter power upper limit control module, a converter power lower limit control module, and a converter bus voltage control module. The converter power upper limit control module uses the difference between the grid connection point output power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the converter power upper limit control module after passing through the regulator; the converter power lower limit control module uses the difference between the grid connection point input power limit value and the grid connection point real-time power as the input of the regulator, and obtains the output of the converter power lower limit control module after passing through the regulator; the converter bus voltage control module uses the difference between the converter bus voltage reference value and the DC bus real-time voltage as the input of the regulator, and obtains the output of the converter bus voltage control module after passing through the regulator. The output of the converter bus voltage control module is subjected to amplitude limiting processing to generate an output power reference value for adjusting and controlling the converter.

13. The DC converter system according to claim 11, wherein The DC converter control unit includes a DC converter bus voltage control module. The DC converter bus voltage control module uses the difference between the DC converter bus voltage reference value and the DC bus real-time voltage as the input of the regulator, and obtains the output of the DC converter bus voltage control module after passing through the regulator. The output of the DC converter bus voltage control module is subjected to amplitude limiting processing to generate an output power reference value for adjusting and controlling the DC converter.

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