Control method, device and equipment of DC conversion module of DC charging pile and medium

Abstract

The invention discloses a control method, device and equipment for a direct current conversion module of a direct current charging pile and a medium, and relates to the technical field of charging pile control. When the charging process of a direct current converter adopting three-level topology in the direct current conversion module of the direct current charging pile is controlled, based on the type of a battery and the actual electric quantity of the battery at the current moment, the direct current conversion module of the direct current charging pile is controlled; determining the expected output voltage of the DC converter at the current moment by using the charging characteristic curve of the battery; based on the actual output voltage, the actual output current and the expected output voltage of the DC converter at the current moment, generating a dynamic surface control law at the current moment by using a control method based on a dynamic surface; and controlling the direct-current converter by using the dynamic surface control law at the current moment so as to adjust the output voltage and the output current of the direct-current converter. According to the invention, the direct-current converter adopting the three-level topology can be effectively controlled, and the problem of thermal runaway of the battery in the charging process is reduced.

Description

Technical Field

[0001] The present application relates to the field of charging pile control technology, and in particular to a control method, device, equipment and medium for a DC conversion module of a DC charging pile. Background Art

[0002] In recent years, electric vehicles have gradually become one of the mainstream means of transportation. Therefore, DC charging piles are also one of the research hotspots. With the gradual development of "photovoltaic storage direct flexible" technology, it is an inevitable trend for the "photovoltaic storage charging" integrated charging station to usher in large-scale implementation. As a DC high-power load, the charging pile is directly connected to the high-voltage DC bus, which is powered by photovoltaics. Photovoltaic power generation depends on solar energy resources and is greatly affected by climate and geographical conditions. There is power uncertainty, which will impact the DC converter of the DC conversion module in the charging pile. At the same time, the DC converter will inevitably be subject to some known or unknown disturbances. In order to ensure the stable operation of the DC converter, a DC converter with a three-level topology came into being.

[0003] The DC charging pile is mainly fast-charged, and the charging process is DC charging pile-fast charging port-car battery. The DC charging pile includes a DC conversion module, which includes a controller and a DC converter. The controller controls the working process of the DC converter to complete the charging process of the battery. The charging process of the traditional DC charging pile is divided into three stages: when the battery voltage is low, it enters the constant current charging stage, at which time constant current charging is performed with a constant current (high power); when the battery voltage reaches the set threshold, it enters the constant voltage charging stage, at which time constant voltage charging is performed with a constant voltage, the current gradually decreases, and the power decreases accordingly; when the battery charging is close to completion (usually the battery power is 80%-90%), it enters the trickle charging stage, at which time it is charged with a small power (usually 10%-20% of the maximum power) to prevent the battery from overheating and overcharging. The entire charging process is monitored and adjusted in real time by the battery management system and the controller. The battery management system is responsible for real-time monitoring of the battery's voltage, current, temperature and other parameters, and transmits the monitoring parameters to the controller. The controller controls the DC converter based on the monitoring parameters.

[0004] However, the bidirectional power transmission DC converter using a three-level topology is a high-order system. The traditional control method used by the controller cannot effectively control the DC converter using a three-level topology. In addition, the traditional control method used by the controller uses the same voltage when charging all types of batteries. In order to meet the charging requirements of all types of batteries, a larger voltage level is used, which causes the battery to heat up quickly during the charging process, which can easily cause thermal runaway of the battery. Summary of the invention

[0005] The purpose of the present application is to provide a control method, device, equipment and medium for a DC conversion module of a DC charging pile, which can effectively control a DC converter using a three-level topology and reduce the problem of thermal runaway of the battery during charging.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a control method for a DC conversion module of a DC charging pile, which is used to control a DC converter of a DC conversion module in a DC charging pile, wherein the DC converter adopts a three-level topology and the DC converter is used to charge a battery. The control method for the DC conversion module of the DC charging pile includes:

[0008] Obtain the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment;

[0009] Based on the type of battery and the actual power of the battery at the current moment, the expected output voltage of the DC converter at the current moment is determined using the charging characteristic curve of the battery;

[0010] Based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated by using a dynamic surface-based control method;

[0011] The DC converter is controlled using the dynamic surface control law at the current moment to adjust the output voltage and output current of the DC converter.

[0012] Optionally, based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated by using a dynamic surface-based control method, specifically including:

[0013] Establishing a first sliding surface; the first sliding surface is the difference between the actual output voltage and the expected output voltage of the DC converter;

[0014] Derivative the first sliding surface to obtain a first derived sliding surface;

[0015] Combining the first derivative sliding surface with the voltage expression in the state space model of the DC converter to obtain a first transformed formula;

[0016] Establishing a first-order filter based on the first transformed formula, and using the first-order filter to calculate the expected output current of the DC converter at the current moment;

[0017] Establishing a second sliding surface; the second sliding surface is the difference between the actual output current and the expected output current of the DC converter;

[0018] Derivative the second sliding surface to obtain a second derived sliding surface;

[0019] Combining the second derivative sliding surface with the current expression in the state space model of the DC converter to obtain a second transformed formula;

[0020] The first transformed formula, the second transformed formula and the substitution law are combined to obtain the dynamic surface control law at the current moment.

[0021] Optionally, the state space model of the DC converter is:

[0022]

[0023] in, is the voltage expression; is the derivative of the voltage across the resonant capacitor CR1 in the DC converter; u c is the voltage across the resonant capacitor CR1 in the DC converter; C is the capacitance of the resonant capacitor CR1; i1 is the current flowing through the resonant inductor Lr in the DC converter; I o is the load current; is the current expression; is the derivative of the current flowing through the resonant inductor Lr in the DC converter; L is the inductance of the resonant inductor Lr; U is the input voltage of the DC converter; n is the coil turns ratio of the transformer in the DC converter; u is the output voltage of the DC converter.

[0024] Optionally, the first-order filter is:

[0025]

[0026] Among them, τ is the filtering time function; is the derivative of the desired output current of the DC converter; x 2d is the expected output current of the DC converter; x2 is the actual output current of the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter.

[0027] Optionally, the substitution law is:

[0028] θ=-S1x1 / C;

[0029] Wherein, θ is the load impedance; S1 is the first sliding surface; x1 is the actual output voltage of the DC converter; and C is the capacitance value of the resonant capacitor CR1 in the DC converter.

[0030] Optionally, the dynamic surface control law at the current moment is:

[0031]

[0032] Among them, μ is the dynamic surface control law; n is the coil turns ratio of the transformer in the DC converter; L is the inductance value of the resonant inductor Lr in the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter; U is the input voltage of the DC converter; x1 is the actual output voltage of the DC converter; is the derivative of the desired output current of the DC converter; k2 is the second surface gain; S2 is the second sliding surface.

[0033] Optionally, after adjusting the output voltage and output current of the DC converter, the control method of the DC charging pile DC conversion module further includes:

[0034] obtaining a regulated output voltage and a regulated output current of the DC converter;

[0035] Determining whether the adjusted output voltage is equal to the expected output voltage of the DC converter at the current moment, and whether the adjusted output current is equal to the expected output current of the DC converter at the current moment;

[0036] If not, an alarm is issued.

[0037] In a second aspect, the present application provides a control device for a DC conversion module of a DC charging pile, which is used to control a DC converter of a DC conversion module in a DC charging pile, wherein the DC converter adopts a three-level topology, and the DC converter is used to charge a battery. The control device for the DC conversion module of the DC charging pile includes:

[0038] A data acquisition module is used to obtain the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment;

[0039] A voltage determination module, used to determine the expected output voltage of the DC converter at the current moment based on the type of the battery and the actual power of the battery at the current moment, using the charging characteristic curve of the battery;

[0040] A control law generation module, used to generate a dynamic surface control law at the current moment based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment by using a dynamic surface-based control method;

[0041] The control module is used to control the DC converter using the dynamic surface control law at the current moment to adjust the output voltage and output current of the DC converter.

[0042] In a third aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control method of the DC conversion module of a DC charging pile as described above.

[0043] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the control method for a DC conversion module of a DC charging pile as described above.

[0044] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0045] The present application provides a control method, device, equipment and medium for a DC conversion module of a DC charging pile. When controlling the charging process of a DC converter using a three-level topology in a DC conversion module of a DC charging pile, based on the type of battery and the actual power of the battery at the current moment, the expected output voltage of the DC converter at the current moment is determined using the charging characteristic curve of the battery; based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated using a control method based on a dynamic surface; the DC converter is controlled using the dynamic surface control law at the current moment to adjust the output voltage and output current of the DC converter. The present application can generate a dynamic surface control law by combining the charging characteristic curve of the battery and the control method based on the dynamic surface, and use the dynamic surface control law to control the charging process of the DC converter, so that the output of the DC converter can change with the charging characteristic curve of the battery, and the DC converter using the three-level topology can be effectively controlled, and the problem of thermal runaway of the battery during charging can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 A flow chart of a control method for a DC conversion module of a DC charging pile provided in Example 1 of the present application.

[0048] Figure 2 A detailed flowchart of a control method for a DC conversion module of a DC charging pile provided in Example 1 of the present application.

[0049] Figure 3 A schematic diagram of the circuit structure of a DC converter using a three-level topology provided in Example 1 of the present application.

[0050] Figure 4 A schematic diagram of the functional modules of a control device for a DC conversion module of a DC charging pile provided in Example 2 of the present application.

[0051] Figure 5 A schematic diagram of the structure of a computer device provided in Example 3 of the present application. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0053] Example 1

[0054] like Figure 1 and Figure 2 As shown, this embodiment provides a control method for a DC conversion module of a DC charging pile, which is used to control a DC converter of a DC conversion module in a DC charging pile, wherein the DC converter adopts a three-level topology and the DC converter is used to charge a battery. The control method for the DC conversion module of the DC charging pile includes:

[0055] S1: Obtain the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment.

[0056] S2: Based on the type of battery and the actual power of the battery at the current moment, the expected output voltage of the DC converter at the current moment is determined using the battery charging characteristic curve.

[0057] S3: Based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated using a dynamic surface-based control method.

[0058] S4: Using the dynamic surface control law at the current moment to control the DC converter to adjust the output voltage and output current of the DC converter.

[0059] The above steps S1-S4 are implemented. In view of the problem that high-voltage charging in the constant-voltage charging stage may cause battery overheating, this embodiment designs a dynamic surface control law in combination with the control method based on the dynamic surface and the charging characteristic curve of the battery, merges the constant-voltage charging stage and the trickle charging stage, and adapts to the charging characteristic curve so that the output power of the constant-current charging stage is consistent with the charging characteristic curve of the battery, so that the charging temperature rises slowly, and the battery thermal runaway problem caused by instantaneous high voltage and high power is reduced, so as to achieve the purpose of protecting the battery, and the output power of the combined stage of the constant-voltage charging stage and the trickle charging stage is consistent with the charging characteristic curve of the battery, and the output power is gradually reduced, so that the charging temperature rises slowly on the basis of ensuring the charging time, and the battery thermal runaway problem caused by instantaneous high voltage and high power is reduced, so as to achieve the purpose of protecting the battery. At the same time, since the battery temperature rises slowly, the purpose of improving the charging efficiency can be achieved at the same time.

[0060] The equipment selection problem needs to be solved urgently under the current trend of the charging industry. In the face of the impact of frequent intermittent loads on equipment, the matching of power equipment capacity and charging power, etc., it is urgent to develop the hardware and control system of fast charging and super charging equipment. This embodiment selects a DC converter with a three-level topology, and further designs a control method for a DC converter with a three-level topology. Figure 3 As shown, it is a schematic diagram of the circuit structure of the DC converter using the three-level topology used in this embodiment. The DC converter using the three-level topology can reduce the damage to the equipment caused by frequent intermittent impact loads, while reducing harmonics, which is beneficial to vehicle-grid interaction and more intelligent.

[0061] The working process of a DC converter using a three-level topology includes:

[0062] (1) Working mode 1 [t0~t1]: The switch tube Q1 and the switch tube Q2 are turned on at zero voltage at time t0, and the current i flowing through the inductor Lr is Lr and the current i flowing through the inductor Lm Lm Positive increase, where i Lr Rising in a sinusoidal trend, i Lm The rising slope of i Lm The increase rate is greater than i Lr The rise is small. On the low voltage side of the transformer (i.e. the right side of the transformer), because i Lr and i Lm Not equal, that is, the current i when the power supply DC outputs a high level Hv and the current i when the power supply DC output is low Lv is not equal to 0, diode D5 and diode D8 are at i Lv The transformer is turned on under the action of the high voltage side to transmit power to the low voltage side of the transformer. LrAfter exceeding the peak value, it will gradually decrease until i Lr =i Lm , working mode 1 stage is terminated.

[0063] (2) Working mode 2 [t1~t2]: From time t1, i Lr with i Lm equal, because the inductance Lm and the inductance Lr, i Lr The changes are very slow and short-lived, so it can be considered that Lr On the low voltage side of the transformer, i Lv =0, diode D5 and diode D8 are turned off with zero current, capacitor CR2 stops forward charging, and the voltage across capacitor CR2 is u CR2 reaches its maximum value, and before capacitor CR2 joins the resonance again, u CR2 In the working mode 2 stage, there is no energy exchange between the high-voltage side of the transformer and the low-voltage side of the transformer, and the output power can only be provided by the capacitor Cf until the switch tube Q1 and the switch tube Q2 are turned off, and the working mode 2 stage is terminated.

[0064] (3) Working mode 3 [t2-t3]: At t2, switch tubes Q1 and Q2 are turned off, i Lr Charge capacitors CQ1 and CQ2, and discharge capacitors CQ3 and CQ4 until the voltage across capacitor CQ1 reaches U ds1 and the voltage U across capacitor CQ2 ds2 The voltage across capacitor CQ3 rises to half of the input voltage. ds3 and the voltage U across capacitor CQ4 ds4 drops to 0. On the low voltage side of the transformer, i Lv is 0, u CR2 No change, working mode 3 stage is terminated.

[0065] (4) Working mode 4 [t3~t4]: At t3, the voltage across capacitor CQ3 is U ds3 and the voltage U across capacitor CQ4 ds4 Decreases to 0, and then i Lr Let diode D3 and diode D4 conduct, and provide ZVS condition for the switch tube Q3 and switch tube Q4 to turn on. Lr and i Lm Still equal, on the low voltage side of the transformer, i Lv Still 0, u CR2 No change, working mode 4 stage is terminated.

[0066] (5) Operation mode 5 [t4-t5]: From time t4, diodes D3 and D4 are still conducting, but i Lr with i Lm are no longer equal, that is, iLv is no longer equal to 0, where i Lr It decreases in a sinusoidal trend, Lm It falls quickly, so Lv Reverse. On the low voltage side of the transformer, diode D6 and diode D7 are in reverse i Lv The high voltage side of the transformer resumes transmitting power to the low voltage side of the transformer, and the capacitor CR2 begins to charge in reverse. CR2 Decreases, and working mode 5 stage is terminated.

[0067] (6) Working mode 6 [t5-t6]: At t5, the switch tubes Q3 and Q4 are turned on at zero voltage under the action of the driving signal, and the working mode 6 phase is terminated. At this time, the working process of the first half of the switching cycle of the DC converter is completed.

[0068] For the working process of the second half of the switching cycle of the DC converter, comparing working mode 6 with working mode 1, their switching states are complementary and the current directions are opposite, so the 6 working modes of the working process of the second half of the switching cycle are omitted.

[0069] This embodiment further establishes a state space model of the DC converter according to the electrical parameters of the DC converter. The initial state space model is:

[0070]

[0071] In formula (1), is the voltage across the resonant capacitor CR1 in the DC converter c The derivative with respect to time t; is the derivative of the current i1 flowing through the resonant inductor Lr in the DC converter with respect to time t; C is the capacitance of the resonant capacitor CR1; R is the load resistance, that is, the battery resistance; L is the inductance of the resonant inductor Lr; u c is the voltage across the resonant capacitor CR1; i1 is the current flowing through the resonant inductor Lr; U is the input voltage of the DC converter; n is the turns ratio of the transformer in the DC converter; u is the output voltage of the DC converter.

[0072] Simplifying the above formula (1) we can get:

[0073]

[0074] In formula (2), is the voltage expression; is the derivative of the voltage across the resonant capacitor CR1 in the DC converter; u c is the voltage across the resonant capacitor CR1 in the DC converter; C is the capacitance of the resonant capacitor CR1; i1 is the current flowing through the resonant inductor Lr in the DC converter; I ois the load current, i.e. the battery input current; is the current expression; is the derivative of the current flowing through the resonant inductor Lr in the DC converter; L is the inductance of the resonant inductor Lr; U is the input voltage of the DC converter; n is the coil turns ratio of the transformer in the DC converter; u is the output voltage of the DC converter.

[0075] The above formula (2) is the state space model of the DC converter of this embodiment. The state space model includes a voltage expression and a current expression. Subsequently, a dynamic surface control law is established based on the state space model of the DC converter.

[0076] The charging characteristic curve generally refers to the relationship curve between the battery voltage and the charging time when the battery is charged at different current values ​​at different temperatures. In this embodiment, the charging characteristic curves of different types of batteries are generated in advance. The types of batteries are distinguished based on the types of chemical raw materials used in the batteries. A query table of different types of batteries is further generated. The query table includes the corresponding relationship between the battery type, the battery power and the battery voltage. After obtaining the actual power of the battery, the query table is queried based on the battery type and the actual power of the battery at the current moment to obtain the battery voltage. The battery voltage is the expected output voltage of the DC converter at the current moment.

[0077] This embodiment also obtains the actual output voltage and actual output current of the DC converter at the current moment, and further generates the dynamic surface control law at the current moment based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment using a dynamic surface-based control method.

[0078] S3 specifically includes:

[0079] (1) A first sliding surface is established, where the first sliding surface is a difference between an actual output voltage of the DC converter and a desired output voltage.

[0080] Taking the expected output voltage as the reference voltage, a first sliding surface is established. The first sliding surface is:

[0081] S1=x1-x 1d (3)

[0082] In formula (3), S1 is the first sliding surface; x1 is the actual output voltage of the DC converter, and the voltage u across the resonant capacitor CR1 in the DC converter is detected. c Get; x 1d is the desired output voltage of the DC converter.

[0083] (2) Deriving the first sliding surface, obtaining the first derived sliding surface.

[0084] After the first derivation, the sliding surface is:

[0085]

[0086] In formula (4), is the derivative of the first sliding surface; is the derivative of the actual output voltage of the DC converter; is the derivative of the desired output voltage of the DC converter.

[0087] (3) Combining the voltage expressions of the sliding surface after the first derivation and the state space model of the DC converter, the first transformed formula is obtained.

[0088] Combining the sliding surface after the first derivation shown in equation (4) and the voltage expression in the state space model of the DC converter shown in equation (2), the intermediate transformation formula is:

[0089]

[0090] In formula (5), is the derivative of the actual output voltage of the DC converter; θ is the load impedance, that is, the battery impedance; C is the capacitance value of the resonant capacitor CR1 in the DC converter; x1 is the actual output voltage of the DC converter; x2 is the actual output current of the DC converter, which is obtained by detecting the current i1 flowing through the resonant inductor Lr.

[0091] Combining equations (3), (4) and (5), we can further obtain the first transformed formula:

[0092]

[0093] In formula (6), C is the capacitance value of the resonant capacitor CR1 in the DC converter; x2 is the actual output current of the DC converter; θ is the load impedance, that is, the battery impedance; x1 is the actual output voltage of the DC converter; is the derivative of the desired output voltage of the DC converter; k1 is the first surface gain; S1 is the first sliding surface.

[0094] (4) A first-order filter is established based on the first transformed formula, and the expected output current of the DC converter at the current moment is calculated using the first-order filter.

[0095] Based on formula (6), this embodiment selects x2 / C to make S1 stable, that is, track Stable, the first sliding surface S1 is connected to a first-order filter x2 / C, and the first-order filter is obtained as:

[0096]

[0097] In formula (7), τ is the filtering time function; is the derivative of the desired output current of the DC converter; x 2d is the expected output current of the DC converter; x2 is the actual output current of the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter.

[0098] In formula (7), only the expected output current is an unknown value. Therefore, using formula (7), the expected output current x of the DC converter at the current moment can be calculated. 2d .

[0099] (5) Establishing a second sliding surface, where the second sliding surface is the difference between the actual output current and the expected output current of the DC converter.

[0100] Based on the calculated x 2d Define the second sliding surface, which is:

[0101]

[0102] In formula (8), S2 is the second sliding surface; C is the capacitance value of the resonant capacitor CR1 in the DC converter; x2 is the actual output current of the DC converter; x 2d is the desired output current of the DC converter.

[0103] (6) Deriving the second sliding surface, obtaining the second derived sliding surface.

[0104] After the second derivation, the sliding surface is:

[0105]

[0106] In formula (9), is the derivative of the second sliding surface; C is the capacitance value of the resonant capacitor CR1 in the DC converter; is the derivative of the actual output current of the DC converter; is the derivative of the desired output current of the DC converter.

[0107] (7) Combining the sliding surface after the second derivation with the current expression in the state space model of the DC converter, the second transformed formula is obtained.

[0108] Combining the second derivative sliding surface shown in equation (9) and the current expression in the state space model of the DC converter shown in equation (2), the second transformed formula is obtained:

[0109]

[0110] In formula (10), is the derivative of the second sliding surface; L is the inductance of the resonant inductor Lr in the DC converter; C is the capacitance of the resonant capacitor CR1 in the DC converter; x1 is the actual output voltage of the DC converter; U is the input voltage of the DC converter; n is the coil turns ratio of the transformer in the DC converter; μ is the dynamic surface control law; is the derivative of the desired output current of the DC converter.

[0111] (8) Combining the first transformed formula, the second transformed formula and the substitution law, the dynamic surface control law at the current moment is obtained.

[0112] In order for x2 to track x 2d Asymptotically stable, design a suitable dynamic surface control law μ. Specifically, first calculate the substitution law through the adaptive function algorithm. The substitution law is:

[0113] θ=-S1x1 / C(11)

[0114] In formula (11), θ is the load impedance; S1 is the first sliding surface; x1 is the actual output voltage of the DC converter; and C is the capacitance value of the resonant capacitor CR1 in the DC converter.

[0115] Combining the first transformed formula shown in formula (6), the second transformed formula shown in formula (10) and the substitution law shown in formula (11), the dynamic surface control law is obtained as follows:

[0116]

[0117] In formula (12), μ is the dynamic surface control law; n is the coil turns ratio of the transformer in the DC converter; L is the inductance value of the resonant inductor Lr in the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter; U is the input voltage of the DC converter; x1 is the actual output voltage of the DC converter; is the derivative of the desired output current of the DC converter; k2 is the second surface gain; S2 is the second sliding surface.

[0118] μ also serves as the duty cycle in PWM control. The controller controls the DC converter by changing the duty cycle to achieve the purpose of voltage regulation, so that the actual output voltage is equal to the expected output voltage, and the actual output current is equal to the expected output current, so that the DC converter can work according to the charging characteristic curve of the battery, reduce battery heating, reduce the problem of thermal runaway of the battery, and improve battery life and safety.

[0119] This embodiment proposes a control method based on dynamic surface and designs a dynamic surface control law. For the DC conversion module of the DC charging pile, the desired output voltage is used as input, and the dynamic surface control law is obtained through the control method based on dynamic surface. By controlling the opening and closing of the switch tube in the DC converter, the duty cycle at a fixed frequency is adjusted to achieve the purpose of making the DC converter output the desired output voltage and the desired output current.

[0120] As an optional implementation, after adjusting the output voltage and output current of the DC converter, the control method of the DC charging pile DC conversion module of this embodiment further includes:

[0121] (1) Obtain the regulated output voltage and regulated output current of the DC converter.

[0122] (2) Determine whether the adjusted output voltage is equal to the expected output voltage of the DC converter at the current moment, and whether the adjusted output current is equal to the expected output current of the DC converter at the current moment.

[0123] (3) If not, no output is given, the battery is powered off, and an alarm is sounded.

[0124] (4) If yes, then the output is normal, the battery is charged, and the actual output voltage and actual output current at the next moment are obtained until the battery charging is completed.

[0125] Since there is little research on DC converters using three-level topology at this stage, there are also few research results on the controller design of DC converters using three-level topology. This embodiment summarizes the general control method applicable to DC converters using three-level topology and compares it with the dynamic surface-based control method used in this embodiment.

[0126] (1) Frequency conversion control technology

[0127] The required switching control is obtained by changing the switching frequency above the resonant frequency. The controller consists of a wideband error amplifier, a voltage-controlled oscillator, and a temperature-stable one-shot timer. The output voltage is compared with the reference voltage to obtain an error voltage, which is amplified and used to drive the voltage-controlled oscillator. The voltage-controlled oscillator output triggers a single pulse, and its pulse duration is fixed according to the requirements of the converter. This control technique is based on the voltage control mode, so the input transient response is poor.

[0128] Frequency conversion control technology has obvious advantages in speed regulation range and efficiency, and is particularly suitable for applications such as fans and pumps that require flexible speed regulation. However, frequency conversion control technology performs poorly in dealing with complex nonlinear systems and fast dynamic response. The control method based on the dynamic surface gradually approaches the target trajectory by designing the dynamic surface, providing faster response and higher robustness. Compared with frequency conversion control technology, the control method based on the dynamic surface performs well in dealing with nonlinear systems and coping with large disturbances, and is suitable for occasions that require high dynamic performance and precise control.

[0129] (2) Linear Quadratic Regulator

[0130] Methods based on optimal control have the advantage of being more systematic than classical control methods. During the design process, the designer only needs to guess the values ​​of a few parameters, which have physical meaning and boundaries, and the rest of the calculations can be implemented on a computer. Usually, the energy function of the resonant tank is minimized, so the transient response is optimized. The significant advantage of optimal control is that a robust controller with a fairly good accuracy margin is guaranteed when the state variables are accessible. The design process starts with calculating the linear state space model of the circuit at one operating point, then, a linear quadratic regulator is calculated at this point until the controller has good marginal robustness, which guarantees a good response in the operating range. The disadvantage of this controller is that it requires measuring all the states of the system, which can be an obstacle. Therefore, the linear quadratic regulator is usually used together with the Kalman filter as an estimator for those inaccessible system states to reduce the measurement effort. On the other hand, this optimal controller with estimators has two disadvantages: first, the controller topology is relatively complex, and second, it has a high sensitivity to any possibility of uncertain models. This is a variable frequency controller for a resonant converter, and the complexity of the controller is justified by the use of a more powerful and systematic approach.

[0131] Linear quadratic regulators are very effective in dealing with linear systems and small-scale nonlinear systems, and have good steady-state and dynamic performance. However, linear quadratic regulators rely on accurate system models and linearization assumptions, and their performance may be limited for systems with strong nonlinearity and large-scale uncertainty. Dynamic surface-based control methods can better handle nonlinear and uncertain systems by designing dynamic surfaces to gradually approach the target trajectory. Dynamic surface-based control methods provide higher robustness and adaptability, especially in practical applications, and are more resistant to model uncertainty and external disturbances.

[0132] (3) PI control

[0133] The PI controller combines proportional control and integral control by adjusting the proportional gain k p and integral gain k iTo adjust the output of the system. The input of the controller is the error e(t) = v ref -v out , v ref is the reference voltage, v out is the output voltage, and the output is the control signal u(t) to reduce the steady-state error and improve the stability of the system.

[0134] The control method based on dynamic surface is superior to PI control because it has better dynamic response and robustness when dealing with nonlinear systems and large disturbances. PI control may have large overshoot and oscillation under nonlinearity and load disturbances, while the control method based on dynamic surface gradually approaches the target trajectory through the dynamic surface, providing faster response and stronger robustness.

[0135] (4) Sliding mode control

[0136] The application of sliding mode control in DC / DC converters is mainly to achieve efficient power conversion and stable output regulation. The basic principle is to design a sliding surface so that the system state can converge quickly on the surface, thereby achieving stable control of the system. However, due to factors such as switching frequency limitation and electromagnetic interference, when the state or output variable of the control system is close to the sliding surface, the system may experience frequent oscillation or vibration. This oscillation may cause system performance to deteriorate and affect the stability and control effect of the system.

[0137] Chattering usually occurs after the sliding mode control system enters the sliding surface, that is, when the system state reaches or approaches the sliding surface and starts to slide. Since the sliding mode control keeps the system on the sliding surface by high-frequency switching on the sliding surface, in actual engineering, this high-frequency switching causes oscillation due to the limited response time and delay of the actuator. When there is measurement noise and parameter uncertainty in the system, the controller's response to these uncertainties and noise will also cause chattering. The measurement noise is amplified under the action of the sign function, resulting in frequent switching of the control input to form chattering. The actual actuator has its dynamic characteristics and limitations and cannot respond to the switching of the control input infinitely fast. This will cause lag and oscillation of the actual control input, further exacerbating the chattering phenomenon. Therefore, the sliding mode control method requires filters or high-order sliding mode control in high-order systems to reduce the chattering phenomenon and optimize the control effect. The control method based on the dynamic surface effectively reduces the chattering phenomenon in the sliding mode control by introducing the dynamic surface, while maintaining the robustness and fast response of the sliding mode control. In addition, the control method based on the dynamic surface provides a smoother control effect and is suitable for systems with high requirements for stable performance.

[0138] (5) Dynamic control with backstepping control technology

[0139] Backstepping control is to achieve precise regulation of the output voltage or current of the DC / DC converter by recursively designing a virtual controller. By designing a backstepping controller, the output quantity can be accurately tracked and adjusted. The backstepping control method has good robustness to system parameter changes and external interference, and can ensure the stability and performance of the system within a certain range. The backstepping control method can usually achieve a faster dynamic response, can quickly respond to input changes and load changes, and maintain a stable output voltage or current. The design of the backstepping controller is relatively complex, and it is necessary to consider issues such as the design of the virtual controller and parameter adjustment, which may require a long debugging and optimization process.

[0140] Since the design of the backstepping control law requires continuous differentiation for certain nonlinear functions, which causes computational explosion and is not conducive to engineering implementation. The control method based on dynamic surface has good robustness, can achieve precise control, and compared with backstepping control, it will not have the problem of "differential explosion".

[0141] Combined with the above description, compared with the prior art, the control method of this embodiment can better protect the battery life while ensuring the charging efficiency. After combining with the charging characteristic curve of the battery, the output power of the charging pile is similar to the power required by the battery, and the battery thermal runaway problem will not occur.

[0142] Example 2

[0143] Based on the same inventive concept, the embodiment of the present application also provides a control device for a DC charging pile DC conversion module for implementing the control method of the DC charging pile DC conversion module involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiment of the control device for the DC charging pile DC conversion module provided below can refer to the limitations of the control method for the DC charging pile DC conversion module above, and will not be repeated here.

[0144] like Figure 4 As shown, a control device for a DC conversion module of a DC charging pile is provided, which is used to control a DC converter of the DC conversion module in the DC charging pile, wherein the DC converter adopts a three-level topology and is used to charge a battery. The control device for the DC conversion module of the DC charging pile includes:

[0145] The data acquisition module M1 is used to acquire the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment.

[0146] The voltage determination module M2 is used to determine the expected output voltage of the DC converter at the current moment based on the type of the battery and the actual power of the battery at the current moment, using the charging characteristic curve of the battery.

[0147] The control law generating module M3 is used to generate the dynamic surface control law at the current moment based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment by using a dynamic surface based control method.

[0148] The control module M4 is used to control the DC converter by using the dynamic surface control law at the current moment, so as to adjust the output voltage and output current of the DC converter.

[0149] Example 3

[0150] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 5 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the computer device is used to store data. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a control method for a DC charging pile DC conversion module is implemented.

[0151] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0152] In an exemplary embodiment, a computer device is also provided, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control method of the DC charging pile DC conversion module described in Example 1.

[0153] Example 4

[0154] An embodiment of the present application provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the control method of the DC conversion module of the DC charging pile described in Example 1 is implemented.

[0155] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A control method for a DC conversion module of a DC charging pile, used to control a DC converter of a DC conversion module in a DC charging pile, wherein the DC converter adopts a three-level topology and is used to charge a battery, characterized in that: The control method of the DC charging pile DC conversion module includes: Obtain the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment; Based on the type of battery and the actual power of the battery at the current moment, the expected output voltage of the DC converter at the current moment is determined using the charging characteristic curve of the battery; Based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated by using a dynamic surface-based control method; The DC converter is controlled using the dynamic surface control law at the current moment to adjust the output voltage and output current of the DC converter.

2. The control method of the DC conversion module of the DC charging pile according to claim 1 is characterized in that: Based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment, a dynamic surface control law at the current moment is generated by using a control method based on a dynamic surface, which specifically includes: Establishing a first sliding surface; the first sliding surface is the difference between the actual output voltage and the expected output voltage of the DC converter; Derivative the first sliding surface to obtain a first derived sliding surface; Combining the first derivative sliding surface with the voltage expression in the state space model of the DC converter to obtain a first transformed formula; Establishing a first-order filter based on the first transformed formula, and using the first-order filter to calculate the expected output current of the DC converter at the current moment; Establishing a second sliding surface; the second sliding surface is the difference between the actual output current and the expected output current of the DC converter; Derivative the second sliding surface to obtain a second derived sliding surface; Combining the second derivative sliding surface with the current expression in the state space model of the DC converter to obtain a second transformed formula; The first transformed formula, the second transformed formula and the substitution law are combined to obtain the dynamic surface control law at the current moment.

3. The control method of the DC charging pile DC conversion module according to claim 2 is characterized in that: The state space model of the DC converter is: in, is the voltage expression; is the derivative of the voltage across the resonant capacitor CR1 in the DC converter; u c is the voltage across the resonant capacitor CR1 in the DC converter; C is the capacitance of the resonant capacitor CR1; i1 is the current flowing through the resonant inductor Lr in the DC converter; I o is the load current; is the current expression; is the derivative of the current flowing through the resonant inductor Lr in the DC converter; L is the inductance of the resonant inductor Lr; U is the input voltage of the DC converter; n is the coil turns ratio of the transformer in the DC converter; u is the output voltage of the DC converter.

4. The control method of the DC charging pile DC conversion module according to claim 2 is characterized in that: The first-order filter is: Among them, τ is the filtering time function; is the derivative of the desired output current of the DC converter; x 2d is the expected output current of the DC converter; x2 is the actual output current of the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter.

5. The control method of the DC conversion module of the DC charging pile according to claim 2 is characterized in that: The substitution law is: θ=-S1x1 / C; Wherein, θ is the load impedance; S1 is the first sliding surface; x1 is the actual output voltage of the DC converter; and C is the capacitance value of the resonant capacitor CR1 in the DC converter.

6. The control method of the DC conversion module of the DC charging pile according to claim 2 is characterized in that: The dynamic surface control law at the current moment is: Among them, μ is the dynamic surface control law; n is the coil turns ratio of the transformer in the DC converter; L is the inductance value of the resonant inductor Lr in the DC converter; C is the capacitance value of the resonant capacitor CR1 in the DC converter; U is the input voltage of the DC converter; x1 is the actual output voltage of the DC converter; is the derivative of the desired output current of the DC converter; k2 is the second surface gain; S2 is the second sliding surface.

7. The control method of the DC conversion module of the DC charging pile according to claim 1 is characterized in that: After adjusting the output voltage and output current of the DC converter, the control method of the DC charging pile DC conversion module further includes: obtaining a regulated output voltage and a regulated output current of the DC converter; Determining whether the adjusted output voltage is equal to the expected output voltage of the DC converter at the current moment, and whether the adjusted output current is equal to the expected output current of the DC converter at the current moment; If not, an alarm is issued.

8. A control device for a DC conversion module of a DC charging pile, used to control a DC converter of the DC conversion module in the DC charging pile, wherein the DC converter adopts a three-level topology and is used to charge a battery, characterized in that: The control device of the DC conversion module of the DC charging pile includes: A data acquisition module is used to obtain the actual output voltage and actual output current of the DC converter and the actual power of the battery at the current moment; A voltage determination module, used to determine the expected output voltage of the DC converter at the current moment based on the type of the battery and the actual power of the battery at the current moment, using the charging characteristic curve of the battery; A control law generation module, used to generate a dynamic surface control law at the current moment based on the actual output voltage, actual output current and expected output voltage of the DC converter at the current moment by using a dynamic surface-based control method; The control module is used to control the DC converter using the dynamic surface control law at the current moment to adjust the output voltage and output current of the DC converter.

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control method of the DC conversion module of a DC charging pile according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the control method of the DC conversion module of the DC charging pile described in any one of claims 1 to 7 is implemented.

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