Self-adaptive voltage control method, system and device for charging pile and medium

Abstract

The invention discloses a voltage adaptive control method, system and device for a charging pile and a medium, and the method comprises the steps: obtaining a reactive voltage droop coefficient of the charging pile, and determining a compensation coefficient according to the reactive voltage droop coefficient; the power grid voltage of a power grid where the charging pile is located is obtained, and a standard feed-forward coefficient is determined according to the power grid voltage, the line impedance of the charging pile, the double-closed-loop impedance and the rated active power; when it is detected that the voltage drop exists in the power grid, the harmonic order of power grid current in the power grid is obtained, the standard feed-forward coefficient is adjusted according to the harmonic order, and a self-adaptive feed-forward coefficient of the charging pile is obtained; and acquiring a voltage drop value of the power grid, and controlling the charging pile to output an output voltage matched with the voltage drop value according to the compensation coefficient, the adaptive feedforward coefficient and the voltage drop value, so as to improve the operation stability of a power grid system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grid-connected technology, and in particular to a voltage adaptive control method, system, device and medium for charging piles. BACKGROUND

[0002] With the popularization of new energy vehicles and the rapid deployment of charging facilities, the penetration rate of high-power grid-forming charging piles in the power grid has significantly increased. However, as a nonlinear and impulsive load, the large-scale access of charging piles will inject a large amount of harmonics into the power grid and cause significant voltage fluctuations and drops and other power quality problems. This not only leads to local power quality deterioration, but also may cause background harmonic amplification, threatening the safe and stable operation of the regional power grid.

[0003] To address the above challenges, domestic and foreign scholars focus on active governance technologies such as virtual impedance and feedforward control. Among them, a harmonic suppression strategy based on current negative feedforward for virtual synchronous generator is proposed, which can reduce the total harmonic distortion of grid-connected current from 16.46% to 3.6% by combining virtual impedance to reshape the output impedance. A coordinated control of complete voltage feedforward and virtual impedance is introduced in the LCL type grid-connected inverter, which can suppress resonance and reduce the total harmonic distortion rate to below 2.1%. In addition, some researches use generalized integrators to extract harmonics and combine feedforward control, or use virtual impedance angle adaptive algorithms to overcome the harmonic amplification problem caused by fixed parameters. These studies confirm that the coordinated application of virtual impedance and feedforward control is an effective solution to improve power quality in complex grid environments.

[0004] However, the present inventors have found in practice that the above prior art still has significant deficiencies: first, most strategies focus on improving the quality of grid-connected current (such as harmonic suppression), and insufficient attention is paid to the stability support capability of the output voltage of grid-forming charging piles when the grid voltage drops, and both are difficult to consider. Second, the parameters such as virtual impedance and feedforward coefficient in the existing solutions are often based on independent design or empirical debugging, and there is a lack of comprehensive mathematical models and control frameworks that can optimize the voltage support capability and current harmonic suppression performance, resulting in limited overall power quality optimization effect of the system under grid voltage disturbance. SUMMARY

[0005] To solve the above technical problems, the present application discloses a voltage adaptive control method, system, device and medium for charging piles, which is used to improve the stability of power grid operation.

[0006] To achieve the above purpose, in a first aspect, the present application discloses a voltage adaptive control method for charging piles, comprising:

[0007] obtaining a reactive voltage droop coefficient of the charging pile, to determine a compensation coefficient according to the reactive voltage droop coefficient;

[0008] Obtain the grid voltage of the power grid where the charging pile is located, and determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance, and the rated active power.

[0009] When a voltage drop is detected in the power grid, the harmonic order of the grid current in the power grid is obtained, and the standard feedforward coefficient is adjusted according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile.

[0010] The voltage drop value of the power grid is obtained, and the output voltage of the charging pile is controlled to match the voltage drop value based on the compensation coefficient, the adaptive feedforward coefficient, and the voltage drop value.

[0011] This invention discloses a voltage adaptive control method for charging piles, solving the technical problem of simultaneously achieving voltage stability and harmonic suppression when the grid voltage drops, thus improving the stability of the power grid system. Specifically, by introducing a compensation coefficient based on reactive power voltage droop and incorporating the voltage drop value for control during grid voltage dips, active support and adaptive adjustment of the charging pile's output voltage are achieved, preventing undervoltage shutdowns due to grid voltage drops. By introducing a standard feedforward coefficient based on system parameters and further dynamically adjusting it according to the actual harmonic order to obtain an adaptive feedforward coefficient, precise and adaptive suppression of specific harmonics is achieved, effectively reducing the harmonic distortion rate of the grid-connected current. Finally, the compensation coefficients for voltage and current are combined with the adaptive feedforward coefficient for the final control of the charging pile's output voltage, achieving synergistic optimization and simultaneous improvement of the two key indicators—voltage stability and current quality—within a single control framework, thereby enhancing the stability of the power grid system.

[0012] As a preferred example, before obtaining the reactive voltage droop coefficient of the charging pile and determining the compensation coefficient based on the reactive voltage droop coefficient, the process includes:

[0013] Construct an equivalent impedance model for the charging pile; wherein, the equivalent impedance model includes the equivalent impedance of the reactive voltage link of the charging pile, the line impedance, the filter impedance, and the virtual impedance;

[0014] Based on the reactive voltage control loop of the charging pile and the equivalent impedance model, the negative feedback mapping relationship between the equivalent impedance of the reactive voltage loop and the output voltage of the charging pile is obtained.

[0015] Based on the calculation formula of the equivalent impedance of the reactive voltage link and the negative feedback mapping relationship, the reactive voltage droop coefficient of the charging pile is obtained, and the compensation coefficient of the output voltage is determined based on the reactive voltage droop coefficient.

[0016] The above scheme provides a solid theoretical basis and clear physical meaning for determining the compensation coefficient by constructing an equivalent impedance model and analyzing the negative feedback mapping relationship. This transforms the determination process of the compensation coefficient from black-box empirical debugging to white-box model derivation, thereby improving the accuracy, reliability and repeatability of the control.

[0017] As a preferred example, the step of obtaining the reactive voltage droop coefficient of the charging pile, and determining the compensation coefficient based on the reactive voltage droop coefficient, includes:

[0018] Obtain the reciprocal of the reactive voltage droop coefficient, and use the reciprocal as the compensation coefficient.

[0019] The above scheme systematically counteracts the negative impact of the droop coefficient on the output voltage by utilizing the reciprocal relationship, achieving the most efficient voltage compensation. At the same time, selecting the reciprocal of the droop system to determine the compensation coefficient is not only easy to implement in a digital controller, but also ensures the optimization of the voltage support effect.

[0020] As a preferred example, the step of obtaining the grid voltage of the power grid where the charging pile is located, and determining the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance, and the rated active power, includes...

[0021] Obtain the square value of the grid voltage, and obtain the sum of multiple square values ​​of the voltage;

[0022] The line impedance of the charging pile and the double-closed-loop impedance when the charging pile adopts voltage and current double-closed-loop control are obtained, so as to obtain the overall impedance of the charging pile by summing the line impedance and the double-closed-loop impedance.

[0023] The product of the overall impedance and the rated active power of the charging pile is obtained, and the ratio of the sum to the product is used as the standard feedforward coefficient of the charging pile.

[0024] The above scheme calculates a standard feedforward coefficient that is a benchmark value that best matches the current operating conditions of the system by comprehensively considering three key system operating state parameters: grid voltage, overall impedance, and power level. By obtaining the benchmark value, a high-performance initial operating point is provided for subsequent harmonic adaptive suppression, ensuring that the control strategy can quickly enter an effective state under various operating conditions and improving the stability of the power grid system.

[0025] As a preferred example, when a voltage drop is detected in the power grid, obtaining the harmonic order of the grid current in the power grid, and adjusting the standard feedforward coefficient according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile, includes:

[0026] When a voltage drop is detected in the power grid, the first harmonic order and the second harmonic order of the power grid current are obtained, and the first reciprocal of the first harmonic order and the second reciprocal of the second harmonic order are obtained;

[0027] Obtain the absolute value of the difference between the reciprocal of the first number and the reciprocal of the second number, and use the product of the absolute value of the difference and the standard feedforward coefficient as the adaptive feedforward coefficient of the charging pile.

[0028] The above scheme identifies the most important harmonic orders and applies targeted weighted amplification to the standard feedforward coefficient, enabling the suppression measures to precisely target the most harmful harmonic components. This achieves online adaptive adjustment of the feedforward coefficient, significantly improving the targeting and effectiveness of harmonic suppression and enhancing the stability of the power grid system.

[0029] As a preferred example, the step of detecting a voltage drop in the power grid includes:

[0030] The first and second voltages of the power grid are collected sequentially according to the preset acquisition step size;

[0031] The voltage difference between the first voltage and the second voltage is obtained. When the voltage difference is greater than or equal to a preset difference threshold, it is determined that there is a voltage drop in the power grid.

[0032] The above scheme can effectively avoid misjudgments caused by normal voltage fluctuations or measurement noise by setting a difference threshold, improve the reliability of system operation, and ensure that the control strategy is activated only when the power grid system experiences a significant voltage drop, thus achieving an effective balance between safety and efficiency.

[0033] As a preferred example, the step of obtaining the voltage drop value of the power grid, and controlling the output voltage of the charging pile to match the voltage drop value based on the compensation coefficient, the adaptive feedforward coefficient, and the voltage drop value, includes:

[0034] The sum of the adaptive feedforward coefficient and the compensation coefficient is obtained, and the sum of the coefficients is used as the adjustment coefficient of the output voltage.

[0035] The sum of the equivalent impedance of the reactive voltage link, the line impedance, and the virtual impedance of the charging pile is obtained, and the sum of the impedances is used as the comprehensive equivalent impedance of the charging pile.

[0036] Obtain the adjustment ratio value of the line impedance divided by the comprehensive equivalent impedance;

[0037] The reference voltage of the charging pile is obtained, and the output voltage of the charging pile is obtained through a preset series voltage divider function based on the reference voltage, the adjustment ratio, and the adjustment coefficient.

[0038] In the above scheme, the adjustment coefficient, as the resultant force of the compensation coefficient and the feedforward coefficient, comprehensively reflects the dual optimization of voltage support and current quality, thereby improving the stability of the power grid system. Meanwhile, the integrated equivalent impedance model accurately describes the system's impedance characteristics, making the voltage calculation based on the series voltage divider principle highly accurate. Finally, through the preset series voltage divider function, precise, stable, and rapid voltage control guided by the mathematical model is achieved, further improving the stability of the power grid system.

[0039] Secondly, the present invention discloses a voltage adaptive control system for a charging pile, including a compensation module, a feedforward module, an adaptive adjustment module and a voltage control module.

[0040] The compensation module is used to obtain the reactive voltage droop coefficient of the charging pile, so as to determine the compensation coefficient based on the reactive voltage droop coefficient.

[0041] The feedforward module is used to obtain the grid voltage of the power grid where the charging pile is located, so as to determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance and the rated active power.

[0042] The adaptive adjustment module is used to obtain the harmonic order of the grid current in the grid when a voltage drop is detected in the grid, and adjust the standard feedforward coefficient according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile.

[0043] The voltage control module is used to obtain the voltage drop value of the power grid, so as to control the output voltage of the charging pile to match the voltage drop value according to the compensation coefficient, the adaptive feedforward coefficient and the voltage drop value.

[0044] This invention discloses a voltage adaptive control system for charging piles, solving the technical problem of existing technologies that struggle to simultaneously achieve voltage stability and harmonic suppression during grid voltage dips, thus improving the stability of the power grid system. Specifically, by introducing a compensation coefficient based on reactive power voltage droop and incorporating the voltage drop value for control during grid voltage dips, active support and adaptive adjustment of the charging pile's output voltage are achieved, preventing undervoltage shutdowns due to grid voltage drops. Furthermore, by introducing a standard feedforward coefficient based on system parameters and dynamically adjusting it according to the actual harmonic order to obtain an adaptive feedforward coefficient, precise and adaptive suppression of specific harmonics is achieved, effectively reducing the harmonic distortion rate of the grid-connected current. Finally, the compensation coefficients for voltage and current are combined with the adaptive feedforward coefficient for the final control of the charging pile's output voltage, achieving synergistic optimization and simultaneous improvement of the two key indicators—voltage stability and current quality—within a single control framework, thereby enhancing the stability of the power grid system.

[0045] Thirdly, the present invention discloses a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a voltage adaptive control method for a charging pile as described in any one of the first aspects.

[0046] Fourthly, the present invention discloses a computer-readable storage medium comprising: a stored computer program, wherein, when the computer program is executed, the device on which the computer-readable storage medium is located is controlled to perform a voltage adaptive control method for a charging pile as described in any one of the first aspects. Attached Figure Description

[0047] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 This is a schematic flowchart of a voltage adaptive control method for a charging pile provided in an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of the structure of a voltage adaptive control system for a charging pile provided in an embodiment of the present invention;

[0050] Figure 3 This is an equivalent impedance model diagram of a grid-type charging pile provided in an embodiment of the present invention;

[0051] Figure 4 A simplified control block diagram of the voltage loop provided in an embodiment of the present invention;

[0052] Figure 5 A block diagram of virtual impedance control provided in an embodiment of the present invention;

[0053] Figure 6 A simplified equivalent block diagram of a grid-type charging pile provided in an embodiment of the present invention:

[0054] Figure 7 This is a control block diagram of a grid-type charging pile provided in an embodiment of the present invention. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] Reference Figure 1 To improve the stability of the power grid system, this embodiment provides a voltage adaptive control method for charging piles. This method controls the output voltage of the charging piles to ensure the stability of the power grid system. Specifically, the voltage adaptive control method includes:

[0057] Step 101: Obtain the reactive voltage droop coefficient of the charging pile, and determine the compensation coefficient based on the reactive voltage droop coefficient.

[0058] Step 102: Obtain the grid voltage of the power grid where the charging pile is located, and determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance, and the rated active power.

[0059] Step 103: When a voltage drop is detected in the power grid, the harmonic order of the power grid current is obtained, and the standard feedforward coefficient is adjusted according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile.

[0060] Step 104: Obtain the voltage drop value of the power grid, and control the output voltage of the charging pile to match the voltage drop value according to the compensation coefficient, the adaptive feedforward coefficient and the voltage drop value.

[0061] In this embodiment, step 101 includes:

[0062] Step 1011: Construct the equivalent impedance model of the charging pile; wherein, the equivalent impedance model includes the equivalent impedance of the reactive voltage link of the charging pile, the line impedance, the filter impedance and the virtual impedance;

[0063] Step 1012: Based on the reactive voltage control loop of the charging pile and the equivalent impedance model, obtain the negative feedback mapping relationship between the equivalent impedance of the reactive voltage loop and the output voltage of the charging pile.

[0064] Step 1013: Based on the calculation formula of the equivalent impedance of the reactive voltage link and the negative feedback mapping relationship, obtain the reactive voltage droop coefficient of the charging pile, and determine the compensation coefficient of the output voltage based on the reactive voltage droop coefficient.

[0065] Step 1014: Obtain the reciprocal of the reactive voltage droop coefficient, and determine the reciprocal as the compensation coefficient.

[0066] Specifically, in this embodiment, in response to the impact of voltage drops in the power grid, an equivalent impedance of the charging pile is constructed and a voltage compensation coefficient is set. By analyzing the support of the voltage compensation coefficient on the output voltage of the charging pile, the value of the voltage compensation coefficient, i.e., the compensation coefficient, is determined.

[0067] Specifically, refer to Figure 3 As can be seen from the equivalent impedance model diagram of the charging pile shown, the... Figure 3 This includes the power supply, the equivalent impedance of the reactive voltage link, the virtual impedance, the filter impedance, and the line impedance including the busbar, all connected in sequence. According to... Figure 3 It can be seen that the equivalent impedance model of the charging pile is obtained based on the equivalent impedance of the reactive power-voltage control link of the charging pile, that is, based on the equivalent impedance of the reactive power-voltage link of the charging pile, the line impedance, the filter impedance, and the virtual impedance of the charging pile; wherein, the calculation expression of the equivalent impedance model is:

[0068] Z eq1 =X d +X g +X v +X f

[0069] Wherein, the Z eq1 The equivalent impedance of the charging pile; the X d The equivalent impedance of the reactive voltage link of the charging pile; the X g The line impedance of the charging pile; the X v The virtual impedance of the charging pile; the X f The filter impedance of the charging pile is denoted as .

[0070] Specifically, acquiring the charging pile refers to acquiring the voltage regulation link of the grid-type charging pile. That is, when the charging pile uses a reactive power-voltage control link to achieve voltage regulation, the equivalent impedance of the reactive power-voltage link can be solved by the control equation corresponding to the reactive power-voltage control link; wherein, the reactive power-voltage equation in the reactive power-voltage control link is:

[0071] U v =U ref +k q (Q ref -Q s )+k v1 (U ref -U s )

[0072] Wherein, the U sThe terminal voltage of the charging pile is the same as the output voltage of the charging pile; the U v The amplitude of the virtual voltage; the U ref The reference voltage value; the Q ref This is a reactive power reference value; the Q value is... s The output reactive power of the charging pile; the k q The reactive voltage droop coefficient; the k v1 The compensation coefficient is also known as the voltage compensation factor.

[0073] The formula for calculating the output reactive power of the charging pile is as follows:

[0074]

[0075] Based on the calculation expression of the above reactive voltage equation, it can be seen that when the compensation coefficient is 0, the reactive voltage equation is a reactive voltage droop equation. Therefore, the calculation expression of the reactive voltage droop equation is:

[0076] U v =U ref +k q (Q ref -Q s )

[0077] Based on the reactive power-voltage droop equation, the calculation expression for output reactive power, and the reactive power-voltage equation in the reactive power-voltage control loop, it can be seen that when the compensation coefficient is set, i.e., the k... v1 When the value is 0, the calculation expression for the output reactive power can also be:

[0078]

[0079] In summary, based on the two calculation expressions for the output reactive power, the calculation expression for the equivalent impedance of the reactive voltage link is as follows:

[0080] X d =k q U s

[0081] In summary, based on the equivalent impedance model Z eq1 The influence of the equivalent impedance model and the compensation coefficient on the output voltage of the charging pile is analyzed using the calculation expression of the compensation coefficient. Specifically, referring to the reactive power-voltage droop equation and the calculation expression of the reactive power output value of the charging pile, the calculation expression of the output reactive power can also be:

[0082]

[0083] Specifically, when the grid voltage fluctuation is within the normal range, the charging station operates normally; when the grid voltage drop reaches a certain threshold, the charging station will shut down or fail to operate normally due to undervoltage. Because of the grid voltage drop, the charging station's output voltage decreases as the equivalent impedance increases, according to the series voltage divider principle:

[0084]

[0085] E=U ref +k v1 (U ref -U s )

[0086] Where E is the internal potential of the charging pile; the ΔU g The voltage drop value of the power grid.

[0087] Based on the calculation expressions for the internal potential and the output voltage, the calculation expression for the output voltage of the charging pile with additional compensation coefficient and equivalent impedance can be obtained as follows:

[0088]

[0089] According to the calculation expression of the output voltage of the charging pile, the output voltage of the charging pile is related to the compensation coefficient, and it increases with the increase of the compensation coefficient and decreases with the increase of the equivalent impedance.

[0090] In summary, based on the above analysis, the reciprocal of the reactive voltage droop coefficient is selected as the compensation coefficient. For example, according to the specified reactive voltage regulation coefficient, when k... q The value ranges from 0.03 to 0.08. The voltage compensation factor, also known as the compensation coefficient k, is... v1 That is, k q The reciprocal of the compensation coefficient; the calculation expression for the compensation coefficient is:

[0091]

[0092] Wherein, the k v1 The value range is 12.5-33.3.

[0093] In this embodiment, the above steps, by constructing an equivalent impedance model and analyzing the negative feedback mapping relationship, provide a solid theoretical basis and clear physical meaning for determining the compensation coefficient. This transforms the determination process of the compensation coefficient from black-box empirical debugging to white-box model derivation, improving the accuracy, reliability, and repeatability of the control. Furthermore, the reciprocal relationship is used to systematically offset the negative impact of the droop coefficient on the output voltage, achieving the most efficient voltage compensation. Simultaneously, selecting the reciprocal of the droop system for determining the compensation coefficient is not only easy to implement in a digital controller but also ensures optimal voltage support.

[0094] In this embodiment, step 102 includes:

[0095] Step 1021: Obtain the square value of the grid voltage, and obtain the sum of multiple square values ​​of the voltage;

[0096] Step 1022: Obtain the line impedance of the charging pile and the double closed-loop impedance when the charging pile adopts voltage and current double closed-loop control, so as to obtain the overall impedance of the charging pile by summing the line impedance and the double closed-loop impedance.

[0097] Step 1023: Obtain the product of the overall impedance and the rated active power of the charging pile, and use the ratio of the sum to the product as the standard feedforward coefficient of the charging pile.

[0098] Specifically, in this embodiment, the grid-connected output current of the charging pile is analyzed based on the overall impedance and feedforward coefficient. Specifically, when the grid-type charging pile or the charging pile adopts voltage-current dual closed-loop control, since the proportional resonant controller has strong anti-interference ability and good signal tracking ability, the voltage loop adopts a PI controller and the current loop adopts a proportional controller; at this time, the calculation expression of the voltage-current dual closed-loop control is:

[0099]

[0100] Wherein, the G i G v ... i k is the proportionality coefficient of the current loop. u For voltage loop proportional coefficient, k ui This represents the voltage loop integral coefficient.

[0101] Next, by introducing the overall impedance and designing feedforward coefficient parameters, the impact of the overall impedance in the system on the grid-connected output current is analyzed. The overall impedance is constructed from the harmonic voltage variation:

[0102] ΔU=k v2 (UiL -U L )

[0103]

[0104] Wherein, ΔU is the harmonic voltage change; and k v2 The feedforward coefficient; the X q The U represents the dual closed-loop impedance of the charging pile; L The actual voltage across the overall impedance can be expressed as the overall impedance Z. eq2 The difference between the voltages at both ends is obtained as follows:

[0105] U L =V a -V b

[0106] Wherein, the U iL The ideal voltage across the overall impedance; the Z eq2 The overall impedance is defined as I, where I is the grid-connected current of the charging pile; Va and Vb are the voltages across the overall impedance, which can be measured using a voltage sensor. The current feedforward coefficient k... v2 When the value of satisfies the following relationship with the grid-connected current I, the harmonic distortion rate of the current is within the ideal range:

[0107]

[0108] Where ω represents the harmonic content of a certain odd harmonic in the grid-connected current of the charging pile, U g This represents the grid voltage. In summary, based on the above analysis, the feedforward coefficient k is... v2 The calculation expression for the standard feedforward coefficient is:

[0109]

[0110] Wherein, P ref The active power setpoint of the charging pile is the rated active power of the charging pile.

[0111] In this embodiment, the above steps comprehensively consider three key system operating state parameters: grid voltage, overall impedance, and power level. The calculated standard feedforward coefficient is a benchmark value that best matches the current operating condition of the system. By obtaining the benchmark value, a high-performance initial operating point is provided for subsequent harmonic adaptive suppression, ensuring that the control strategy can quickly enter an effective state under various operating conditions and improving the stability of the power grid system.

[0112] In this embodiment, step 103 includes:

[0113] Step 1031: Collect the first voltage and the second voltage of the power grid sequentially according to the preset acquisition step size; obtain the voltage difference between the first voltage and the second voltage; when the voltage difference is greater than or equal to the preset difference threshold, determine that there is a voltage drop in the power grid.

[0114] Step 1032: When a voltage drop is detected in the power grid, the first harmonic number and the second harmonic number of the power grid current are obtained, and the first reciprocal of the first harmonic number and the second reciprocal of the second harmonic number are obtained;

[0115] Step 1033: Obtain the absolute value of the difference between the reciprocal of the first number and the reciprocal of the second number, and use the product of the absolute value of the difference and the standard feedforward coefficient as the adaptive feedforward coefficient of the charging pile.

[0116] Specifically, in this embodiment, the expression for calculating the maximum value of the lower limit of the feedforward coefficient for the h1 and h2 harmonics in the grid-connected current is as follows:

[0117]

[0118] Wherein, K v5-7 The maximum value of the feedforward coefficient is represented by h1; h1 is the first harmonic order; h2 is the second harmonic order.

[0119] For example, the maximum value K of the lower limit of the feedforward coefficient is used to address the 5th and 7th harmonics in the grid-connected current. v5-7 for:

[0120]

[0121] Meanwhile, the values ​​of the feedforward coefficients satisfy the following conditions:

[0122]

[0123] In summary, the grid-connected current harmonic distortion rate meets the requirements at this time. Therefore, the larger the values ​​of the feedforward coefficient and the overall impedance, the better the grid-connected current harmonic suppression effect.

[0124] In this embodiment, the above steps and scheme identify the most important harmonic order and perform targeted weighted amplification on the standard feedforward coefficient, so that the suppression measures are precisely focused on the most harmful harmonic components at present. This achieves online adaptive adjustment of the feedforward coefficient, greatly improves the pertinence and effectiveness of harmonic suppression, and enhances the stability of the power grid system.

[0125] In this embodiment, step 104 includes:

[0126] Step 1041: Obtain the sum of the adaptive feedforward coefficient and the compensation coefficient, and use the sum of the coefficients as the adjustment coefficient of the output voltage;

[0127] Step 1042: Obtain the sum of the equivalent impedance of the reactive voltage link, the line impedance, and the virtual impedance of the charging pile, and use the sum of the impedances as the comprehensive equivalent impedance of the charging pile.

[0128] Step 1043: Obtain the adjustment ratio value of the line impedance divided by the comprehensive equivalent impedance;

[0129] Step 1044: Obtain the reference voltage of the charging pile, and obtain the output voltage of the charging pile through a preset series voltage divider function based on the reference voltage, the adjustment ratio and the adjustment coefficient.

[0130] Specifically, in this embodiment, referring to Figure 4 The simplified voltage loop control block diagram of the charging pile shown illustrates that the block first receives the input signal Usref, then processes it according to a preset adder / subtractor, and finally inputs the processed signal to a PI controller to generate a control quantity through proportional and integral operations, ultimately yielding the output voltage. The actual voltage value of the filter capacitor and the setpoint form a negative feedback loop. By designing the voltage loop parameters so that when the capacitor voltage Uc = Us, the filter reactance and the equivalent impedance of the voltage-current dual-loop control can cancel each other out. Therefore, the comprehensive equivalent impedance of the charging pile can be obtained by taking the remaining impedance parameters; the calculation expression for the comprehensive equivalent impedance is:

[0131] Z v =X d +X g +X v

[0132] Wherein, the Z v This is the constructed comprehensive equivalent impedance.

[0133] The virtual impedance can be determined by the internal potential and the current corresponding to the voltage drop in the mains grid; at this time, refer to Figure 5 As shown in the virtual impedance control diagram, firstly, reference active power and reference reactive power are input to the power control module, which outputs the angle and voltage. Simultaneously, the current during grid voltage dips is detected and input to the virtual impedance value calculation module. The calculated virtual impedance value is used in the virtual impedance control and voltage-current dual closed-loop module, which, combined with the output from the power control module, ultimately generates the reference voltage. The entire process, through information interaction and collaborative work between modules, achieves effective control of system power and voltage under conditions such as grid voltage dips. The rules for determining the virtual impedance are as follows:

[0134]

[0135] Among them, I k This is the current corresponding to a voltage drop in the mains power grid.

[0136] The compensation factor and feedforward coefficient in the system are equivalent to a single overall optimization coefficient. In this case, the voltage compensation factor is positively correlated with the charging pile terminal voltage. Therefore, a larger compensation coefficient value results in better voltage support. Furthermore, the feedforward coefficient is also positively correlated with the grid-connected current; a larger feedforward coefficient value results in better grid-connected current harmonic suppression. The compensation factor and feedforward coefficient can be equivalent to a comprehensive optimization coefficient to obtain the final adjustment coefficient; the calculation expression for the adjustment coefficient is as follows:

[0137] k v =k v1 +k v2

[0138] In the formula, k v This is the adjustment coefficient.

[0139] Based on the comprehensive equivalent impedance model and overall optimization coefficients, the charging pile voltage is kept stable while suppressing grid-connected current harmonics. The simplified equivalent control block diagram of the charging pile is shown below. Figure 6 As shown, Figure 6 The AC power source on the left serves as the energy input, with various resistors connected in series. The circuit then connects to a bus, a crucial node for power collection and distribution, which in turn connects to the equivalent power source on the right through line impedance. The entire model, through the series resistors and bus structure, demonstrates the basic path and equivalent electrical relationships of electrical energy from input to distribution. Figure 6 It can be seen that when the grid-connected current contains the h-th harmonic of Ih%, we can obtain

[0140]

[0141] In the formula, I THD Z_h represents the harmonic distortion rate of the grid-connected current. Z_h represents the impedance of the h-th harmonic. I_h% represents the percentage of harmonic content in the grid-connected current.

[0142] At this point, the harmonic distortion rate, controlled by the comprehensive optimization coefficient and the comprehensive equivalent impedance model, can be maintained within the allowable range. When the grid voltage drops to ΔUg, the charging pile voltage can be calculated using the series voltage divider formula.

[0143]

[0144] In the formula: ΔUg is the value of the grid voltage drop.

[0145] In this embodiment, the adjustment coefficient in the above steps, as the resultant force of the compensation coefficient and the feedforward coefficient, comprehensively reflects the dual optimization of voltage support and current quality, thereby improving the stability of the power grid system. Meanwhile, the comprehensive equivalent impedance model accurately describes the impedance characteristics of the system, making the voltage calculation based on the series voltage divider principle highly accurate. Finally, through the preset series voltage divider function, precise, stable, and rapid voltage control guided by the mathematical model is achieved, further improving the stability of the power grid system.

[0146] Specifically, in this embodiment, referring to Figure 7 The diagram shown is a control block diagram for a grid-type charging pile. Figure 7 The left side of the diagram displays the input three-phase voltage and current, which, after dq transformation, participate in subsequent control. Control signals are generated by the SPWM module, combined with voltage-current control loops and power-voltage control loops, and adjusted using integrated equivalent impedance and comprehensive optimization coefficients. These control loops work together to achieve precise control of the grid-type charging pile based on power calculation results and input electrical quantities, ensuring stable operation and meeting the corresponding power requirements. Figure 7 After implementing the control strategy shown, the harmonic distortion rate of the charging pile's grid-connected output current I can be kept below 5%, while maintaining the stability of the charging pile's terminal voltage Us when the grid voltage drops by ΔUg. To verify the effectiveness of this invention, the 5th and 7th harmonics were tested during grid voltage drops, and three control strategies were set up and compared with the control strategy provided in this application. Strategy 1 is a harmonic suppression strategy for the charging pile's grid-connected output current containing only equivalent impedance; Strategy 2 is a voltage support strategy for the charging pile containing only virtual impedance; and Strategy 3 is a harmonic suppression strategy for the charging pile's grid-connected output current combining only the feedforward coefficient and virtual impedance. At this time, if the grid-connected current contains 4% of the 5th harmonic and 3% of the 7th harmonic, the simulation results of the different strategies are shown in the table below:

[0147]

[0148] As can be seen from the table above, the strategy provided in this embodiment can maintain the stability of the charging pile terminal voltage when the grid voltage drops by ΔUg while ensuring that the harmonic distortion rate does not exceed 5%.

[0149] On the other hand, refer to Figure 2 This embodiment also discloses a voltage adaptive control system for a charging pile, including a compensation module 201, a feedforward module 202, an adaptive adjustment module 203, and a voltage control module 204.

[0150] The compensation module 201 is used to obtain the reactive voltage droop coefficient of the charging pile, so as to determine the compensation coefficient based on the reactive voltage droop coefficient.

[0151] The feedforward module 202 is used to obtain the grid voltage of the power grid where the charging pile is located, so as to determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance and the rated active power.

[0152] The adaptive adjustment module 203 is used to obtain the harmonic order of the grid current in the grid when a voltage drop is detected in the grid, and adjust the standard feedforward coefficient according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile.

[0153] The voltage control module 204 is used to obtain the voltage drop value of the power grid, so as to control the output voltage of the charging pile to match the voltage drop value according to the compensation coefficient, the adaptive feedforward coefficient and the voltage drop value.

[0154] Based on the above embodiment of the voltage adaptive control method for a charging pile, this embodiment also provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the voltage adaptive control method for a charging pile according to any embodiment.

[0155] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0156] The terminal device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and memory. The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device through various interfaces and lines.

[0157] Based on the above-described method embodiments, this embodiment also provides a computer-readable storage medium, including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the voltage adaptive control method for a charging pile as described in any of the above-described method embodiments. Wherein, the modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the present invention can implement all or part of the processes in the methods of the above embodiments, or it can be accomplished by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. Wherein, the computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms, etc. The computer-readable medium may include any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0158] This embodiment discloses a voltage adaptive control method, system, device, and medium for charging piles, solving the technical problem of simultaneously achieving voltage stability and harmonic suppression when the grid voltage drops, thus improving the stability of the power grid system. Specifically, by introducing a compensation coefficient based on reactive power voltage droop and incorporating the voltage drop value for control during grid voltage drops, active support and adaptive adjustment of the charging pile's output voltage are achieved, preventing undervoltage shutdown due to grid voltage drops. By introducing a standard feedforward coefficient based on system parameters and further dynamically adjusting it according to the actual harmonic order to obtain an adaptive feedforward coefficient, precise and adaptive suppression of specific harmonics is achieved, effectively reducing the harmonic distortion rate of the grid-connected current. Finally, the compensation coefficients for voltage and current are combined with the adaptive feedforward coefficient for the final control of the charging pile's output voltage, achieving synergistic optimization and simultaneous improvement of the two key indicators of voltage stability and current quality within a single control framework, thereby enhancing the stability of the power grid system.

[0159] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A voltage adaptive control method for a charging pile, characterized in that, include: Obtain the reactive voltage droop coefficient of the charging pile, and determine the compensation coefficient based on the reactive voltage droop coefficient; Obtain the grid voltage of the power grid where the charging pile is located, and determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance, and the rated active power. When a voltage drop is detected in the power grid, the harmonic order of the grid current in the power grid is obtained, and the standard feedforward coefficient is adjusted according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile. The voltage drop value of the power grid is obtained, and the output voltage of the charging pile is controlled to match the voltage drop value based on the compensation coefficient, the adaptive feedforward coefficient, and the voltage drop value.

2. The voltage adaptive control method for a charging pile according to claim 1, characterized in that, Before obtaining the reactive voltage droop coefficient of the charging pile and determining the compensation coefficient based on the reactive voltage droop coefficient, the process includes: Construct an equivalent impedance model for the charging pile; wherein, the equivalent impedance model includes the equivalent impedance of the reactive voltage link of the charging pile, the line impedance, the filter impedance, and the virtual impedance; Based on the reactive voltage control loop of the charging pile and the equivalent impedance model, the negative feedback mapping relationship between the equivalent impedance of the reactive voltage loop and the output voltage of the charging pile is obtained. Based on the calculation formula of the equivalent impedance of the reactive voltage link and the negative feedback mapping relationship, the reactive voltage droop coefficient of the charging pile is obtained, and the compensation coefficient of the output voltage is determined based on the reactive voltage droop coefficient.

3. The voltage adaptive control method for a charging pile according to claim 2, characterized in that, The step of obtaining the reactive voltage droop coefficient of the charging pile and determining the compensation coefficient based on the reactive voltage droop coefficient includes: Obtain the reciprocal of the reactive voltage droop coefficient, and use the reciprocal as the compensation coefficient.

4. The voltage adaptive control method for a charging pile according to claim 1, characterized in that, The process involves obtaining the grid voltage of the power grid where the charging pile is located, and determining a standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance, and the rated active power. Obtain the square value of the grid voltage, and obtain the sum of multiple square values ​​of the voltage; The line impedance of the charging pile and the double-closed-loop impedance when the charging pile adopts voltage and current double-closed-loop control are obtained, so as to obtain the overall impedance of the charging pile by summing the line impedance and the double-closed-loop impedance. The product of the overall impedance and the rated active power of the charging pile is obtained, and the ratio of the sum to the product is used as the standard feedforward coefficient of the charging pile.

5. The voltage adaptive control method for a charging pile according to claim 4, characterized in that, When a voltage drop is detected in the power grid, the harmonic order of the grid current is obtained, and the standard feedforward coefficient is adjusted according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile, including: When a voltage drop is detected in the power grid, the first harmonic order and the second harmonic order of the power grid current are obtained, and the first reciprocal of the first harmonic order and the second reciprocal of the second harmonic order are obtained; Obtain the absolute value of the difference between the reciprocal of the first number and the reciprocal of the second number, and use the product of the absolute value of the difference and the standard feedforward coefficient as the adaptive feedforward coefficient of the charging pile.

6. The voltage adaptive control method for a charging pile according to claim 5, characterized in that, The step of detecting a voltage drop in the power grid includes: The first and second voltages of the power grid are collected sequentially according to the preset acquisition step size; The voltage difference between the first voltage and the second voltage is obtained. When the voltage difference is greater than or equal to a preset difference threshold, it is determined that there is a voltage drop in the power grid.

7. A voltage adaptive control method for a charging pile according to any one of claims 1-6, characterized in that, The step of obtaining the voltage drop value of the power grid, and controlling the output voltage of the charging pile to match the voltage drop value based on the compensation coefficient, the adaptive feedforward coefficient, and the voltage drop value, includes: The sum of the adaptive feedforward coefficient and the compensation coefficient is obtained, and the sum of the coefficients is used as the adjustment coefficient of the output voltage. The sum of the equivalent impedance of the reactive voltage link, the line impedance, and the virtual impedance of the charging pile is obtained, and the sum of the impedances is used as the comprehensive equivalent impedance of the charging pile. Obtain the adjustment ratio value of the line impedance divided by the comprehensive equivalent impedance; The reference voltage of the charging pile is obtained, and the output voltage of the charging pile is obtained through a preset series voltage divider function based on the reference voltage, the adjustment ratio, and the adjustment coefficient.

8. A voltage adaptive control system for a charging pile, characterized in that, It includes a compensation module, a feedforward module, an adaptive adjustment module, and a voltage control module; The compensation module is used to obtain the reactive voltage droop coefficient of the charging pile, so as to determine the compensation coefficient based on the reactive voltage droop coefficient. The feedforward module is used to obtain the grid voltage of the power grid where the charging pile is located, so as to determine the standard feedforward coefficient based on the grid voltage, the line impedance of the charging pile, the double closed-loop impedance and the rated active power. The adaptive adjustment module is used to obtain the harmonic order of the grid current in the grid when a voltage drop is detected in the grid, and adjust the standard feedforward coefficient according to the harmonic order to obtain the adaptive feedforward coefficient of the charging pile. The voltage control module is used to obtain the voltage drop value of the power grid, so as to control the output voltage of the charging pile to match the voltage drop value according to the compensation coefficient, the adaptive feedforward coefficient and the voltage drop value.

9. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a voltage adaptive control method for a charging pile as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform a voltage adaptive control method for a charging pile as described in any one of claims 1-7.

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