Super charging pile grid-connected property analysis and evaluation method based on dynamic-steady state process

Abstract

The invention relates to the technical field of electrical engineering and automation thereof, in particular to a super charging pile grid-connected property analysis and evaluation method based on a dynamic-steady state process. Comprising the following steps: dynamic change index analysis: time sequence data acquisition, process feature recognition and process stage division; multi-dimensional characteristic quantitative analysis: dynamic characteristic index calculation and steady-state characteristic index evaluation; aggregation effect modeling: group characteristic modeling and interaction influence analysis; an evaluation index system is constructed, wherein a single pile evaluation index and a group evaluation index are included; and realizing a dynamic evaluation mechanism: setting an evaluation period and adjusting a dynamic weight. Through the implementation of the method, the problems of voltage fluctuation, harmonic distortion, frequency deviation and the like possibly caused in the grid connection process of the super charging pile can be effectively solved, stable operation of a power grid is ensured, and meanwhile technical support is provided for rapid popularization of new energy automobiles.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering and automation technology, and in particular to a method for analyzing and evaluating the grid-connected properties of a super charging pile based on a dynamic-steady-state process. Background Art

[0002] With the rapid adoption of new energy vehicles, the efficient deployment and grid-friendly integration of 100-kilowatt supercharging stations have become critical to supporting the "dual carbon" goals. Charging stations are a crucial component of electric vehicle adoption. Currently, grid-connected charging stations are the dominant form of charging stations in my country. With the increasing use of new energy transportation devices such as electric vehicles, the number of charging stations has also increased over time. Conventional charging stations connect directly to the AC grid at the input and are equipped with charging plugs for charging electric vehicles at the output. Charging power typically ranges from tens to hundreds of kilowatts, resulting in relatively slow charging speeds. Furthermore, charging issues are becoming increasingly prominent in specialized scenarios such as shore power for ships, electric trucks, and battery swap stations. In these scenarios, sufficient power must be provided to ensure normal operation of equipment or vehicles within a short period of time, making the demand for fast charging extremely urgent.

[0003] While charging pile technology is rapidly developing, the massive demand for electric vehicles, shore power for ships, electric trucks, and battery swap stations is also placing immense pressure and challenges on the power grid. To meet this growing demand for electricity, advanced management and control methods are needed to fully tap the capabilities of existing transmission and distribution equipment and improve its utilization.

[0004] As high-power charging equipment, supercharging piles have become an important support for new energy transportation. During the grid connection process, supercharging piles may cause voltage fluctuations, harmonic distortion, and frequency offsets in the grid, affecting the stable operation of the grid. Currently, domestic and international research on the grid connection characteristics of supercharging piles focuses on the following aspects:

[0005] (1) Assessment of the impact of charging load on the power grid: Existing studies have analyzed the load curve of high-power charging piles, but most of them are based on steady-state characteristics and lack in-depth research on the dynamic grid connection process.

[0006] (2) Grid compatibility analysis: Some studies have explored the impact of supercharging piles on power quality when connected to the distribution network, but most of them use static simulation methods and fail to fully cover the dynamic change process.

[0007] (3) Harmonic and power quality assessment: Studies have shown that the power electronic devices of super charging piles may generate high-order harmonics, affecting the power quality of the distribution network, but there is a lack of systematic quantitative assessment methods.

[0008] Therefore, the existing technologies still have the following deficiencies: (1) There is a lack of a comprehensive dynamic-steady-state analysis framework, which fails to systematically quantify the transient and steady-state impacts of super charging piles on the power grid. (2) The evaluation indicators are not comprehensive enough. The existing methods mainly focus on a single indicator (such as voltage fluctuation rate) and lack a joint analysis of multiple key grid-connected parameters (such as voltage recovery time, harmonic impact amplitude, and power factor change). (3) The grid-connected adaptability optimization is insufficient, and it fails to provide charging pile parameter optimization solutions for different power grid environments. Summary of the Invention

[0009] The present invention provides a method for analyzing and evaluating the grid-connected properties of super charging piles based on dynamic-steady-state combined parameters to solve the problems existing in the prior art.

[0010] The technical solution adopted by the present invention is: a method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process, comprising the following steps:

[0011] Step 1: Dynamic change indicator analysis:

[0012] Time series data acquisition: collects voltage, current, active power, and reactive power during the charging process; process feature identification: performs multi-scale decomposition based on wavelet transform to identify characteristic points in the charging process; process stage division: divides the charging process into three stages: startup dynamic process, steady-state charging process, and end dynamic process;

[0013] Step 2: Multi-dimensional feature quantitative analysis:

[0014] Dynamic characteristic index calculation: Calculate voltage fluctuation rate and transient response time dynamic characteristic indexes; Steady-state characteristic index evaluation: Evaluate voltage deviation, power factor, voltage stability constraint, frequency deviation constraint, power factor constraint, current harmonic constraint, and transformer capacity constraint;

[0015] Step 3: Aggregate effect modeling:

[0016] Group characteristic modeling: establish an aggregation model of N charging piles; interaction impact analysis: calculate the coupling coefficient of the charging pile group;

[0017] Step 4: Construction of evaluation indicator system:

[0018] Single pile evaluation index: build a single pile evaluation index system; Group evaluation index: build a group evaluation index system;

[0019] Step 5: Dynamic evaluation mechanism implementation:

[0020] Evaluation cycle setting: set the evaluation cycle according to charging characteristics; dynamic weight adjustment: dynamically update the evaluation weight based on operating data.

[0021] As a further improvement of the present invention, in step one, process feature identification is performed using the following formula: ψ(t) = |P(t) - P(t-1)| > ε, where P(t) is the power value at time t and ε is the threshold parameter.

[0022] As a further improvement of the present invention, in step 2, the calculation of the dynamic characteristic index includes:

[0023] Voltage fluctuation rate: ΔV = (V_max - V_min) / V_n × 100%;

[0024] Transient response time: T r =t s -t0,

[0025] Among them, t s is the moment when the system reaches steady state, and t0 is the initial moment of disturbance.

[0026] As a further improvement of the present invention, in step 2, the steady-state characteristic index evaluation includes:

[0027] Voltage deviation:

[0028] Power Factor:

[0029] Voltage stability constraint: |U i -U ref |≤ΔU max ;

[0030] Frequency deviation constraint: |ff nominal |≤Δf max ;

[0031] Power factor constraint: PF ≥ 0.9;

[0032] Current harmonic constraint: THD ≤ 5%;

[0033] Transformer capacity constraint: P load +P EV ≤P rated .

[0034] As a further improvement of the present invention, in step 3, the group characteristic modeling is performed using the following formula: total(t) =∑[α i ×P i(t) ], where α i Participation coefficient of charging pile i.

[0035] As a further improvement of the present invention, in step 3, the interaction impact analysis is performed using the following formula:

[0036] As a further improvement of the present invention, in step 4, the single pile evaluation index is calculated by the following formula: S single =w 1 ×ΔV+w 2 ×T r +w 3 ×δV+w 4 ×PF.

[0037] As a further improvement of the present invention, in step 4, the group evaluation index is performed by the following formula: S group =S single ×K c ×f(N), where f(N) is the scale correction function.

[0038] As a further improvement of the present invention, in step 5, the evaluation period is set by the following formula: T = max (T r )+T stable .

[0039] As a further improvement of the present invention, in step 5, the dynamic weight adjustment is performed by the following formula: Among them, E k is the evaluation error of the kth cycle.

[0040] The beneficial effects of the present invention are as follows: (1) Constructing a multi-dimensional grid-connected analysis framework: systematically evaluating the dynamic response characteristics and steady-state operation characteristics of super charging piles connected to the distribution network; (2) Proposing a joint evaluation index system: covering key parameters such as voltage fluctuation, frequency adjustment, power factor, harmonic distortion, etc., to comprehensively measure the grid-connected adaptability of super charging piles; (3) Optimizing the grid-connected control strategy: adjusting the operating parameters of the charging piles based on the evaluation results to improve grid compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an overall flow chart of a method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process of the present invention. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only used to explain this application and are not intended to limit this application.

[0043] The present invention provides a method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process, comprising the following steps:

[0044] Step 1: Dynamic change indicators (transient process at the moment of grid connection and load mutation)

[0045] 1.1 Time Series Data Collection

[0046] Collect key electrical quantities such as voltage, current, active power, reactive power, etc. during the charging process.

[0047] 1.2 Process feature identification

[0048] Multi-scale decomposition is performed based on wavelet transform to identify characteristic points in the charging process: ψ(t) = |P(t) - P(t-1)| > ε, where P(t) is the power value at time t and ε is the threshold parameter.

[0049] 1.3 Process Stage Division

[0050] The charging process is divided into three stages: the starting dynamic process, the steady-state charging process and the ending dynamic process.

[0051] Step 2: Multi-dimensional feature quantitative analysis

[0052] 2.1 Calculation of dynamic characteristic indicators

[0053] (1) Voltage fluctuation rate: ΔV = (V_max - V_min) / V_n × 100%

[0054] (2) Transient response time: T r =t s -t0, where t s is the moment when the system reaches steady state, and t0 is the initial moment of disturbance.

[0055] 2.2 Steady-state characteristic index evaluation

[0056] Voltage deviation:

[0057] Power Factor:

[0058] Voltage stability constraint: |U i -U ref |≤ΔU max

[0059] Frequency deviation constraint: |ff nominal |≤Δf max

[0060] Power factor constraint: PF ≥ 0.9

[0061] Current harmonic constraint: THD≤5%

[0062] Transformer capacity constraint: P load +P EV ≤Prated

[0063] Step 3: Aggregate Effect Modeling

[0064] 3.1 Population Characteristics Modeling

[0065] Establish an aggregation model of N charging piles: P total(t) =∑[α i ×P i(t) ]i=1,N, where α i is the participation coefficient of charging pile i.

[0066] 3.2 Interaction Impact Analysis

[0067] Calculate the coupling coefficient of the charging pile group:

[0068] Step 4: Construction of evaluation indicator system

[0069] 4.1 Single pile evaluation index: S single =w 1 ×ΔV+w 2 ×T r +w 3 ×δV+w 4 ×PF

[0070] 4.2 Group evaluation index: S group =S single ×K c ×f(N), where f(N) is the scale correction function.

[0071] Step 5: Implementation of dynamic evaluation mechanism

[0072] 5.1 Evaluation cycle setting

[0073] The evaluation period T is set according to the charging characteristics: T=max(T r )+T stable

[0074] 5.2 Dynamic Weight Adjustment

[0075] Dynamically update evaluation weights based on operational data: Where E_k is the evaluation error of the kth cycle.

[0076] Example:

[0077] Ten super chargers are deployed at a charging station, each with a rated power of 150kW. The data acquisition system collects key electrical quantities such as voltage, current, active power, and reactive power during the charging process in real time.

[0078] The collected data is decomposed at multiple scales using wavelet transform to identify characteristic points during the charging process. Dynamic change points during the charging process are identified using the formula: ψ(t) = |P(t) - P(t-1)| > ε, where P(t) is the power value at time t and ε is the threshold parameter.

[0079] According to the recognition results of the characteristic points, the charging process is divided into three stages: (1) Startup dynamic process: the initial stage when the charging pile is connected to the power grid, the voltage and current fluctuate greatly; (2) Steady-state charging process: the charging pile enters a stable working state, and the voltage and current fluctuate less; (3) Ending dynamic process: the transition stage at the end of charging, the voltage and current fluctuate again.

[0080] Calculate the voltage fluctuation rate: ΔV = (V_max - V_min) / V_n × 100%, where V_max and V_min are the maximum and minimum voltage values ​​during charging, respectively, and V_n is the rated voltage.

[0081] Calculate transient response time: T r =t s -t0, where t s is the moment when the system reaches steady state, and t0 is the initial moment of disturbance.

[0082] Calculate the voltage deviation: Calculate the power factor: Evaluate constraints such as voltage stability, frequency deviation, power factor, current harmonics, and transformer capacity

[0083] Establish an aggregation model of 10 charging piles: P total(t) =∑[α i ×P i(t) ], where α i i is the participation coefficient of the i-th charging pile.

[0084] Calculate the coupling coefficient of the charging pile group:

[0085] Construct single pile evaluation index: S single =w 1 ×ΔV+w 2 ×T r +w 3 ×δV+w 4 ×PF; construct group evaluation index: S group =S single ×K c ×f(N), where f(N) is the scale correction function.

[0086] Set the evaluation period: T = max(T r )+T stable; Dynamically adjust evaluation weights: Where E_k is the evaluation error of the kth cycle.

[0087] This paper provides a method for analyzing and evaluating the grid-connected properties of supercharging piles based on a dynamic-steady-state process. Through time-series data acquisition, process feature identification, calculation of dynamic and steady-state characteristic indicators, aggregate effect modeling, and the construction of an evaluation index system, this method systematically evaluates the dynamic response characteristics and steady-state operating characteristics of supercharging piles during the grid-connected process. This method not only comprehensively measures the grid-connected adaptability of supercharging piles but also optimizes their operating parameters based on the evaluation results, improving the compatibility and stability of the power grid.

[0088] Through the implementation of the present invention, it is possible to effectively solve the problems such as voltage fluctuation, harmonic distortion, frequency offset, etc. that may be caused by super charging piles during the grid connection process, ensure the stable operation of the power grid, and provide technical support for the rapid popularization of new energy vehicles.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing and evaluating the grid-connected properties of supercharging piles based on a dynamic-steady-state process, characterized by: The following steps are involved: Step 1: Dynamic change indicator analysis: Time series data collection: collect voltage, current, active power and reactive power during the charging process; Process feature identification: Multi-scale decomposition based on wavelet transform to identify characteristic points in the charging process; Process stage division: the charging process is divided into three stages: the startup dynamic process, the steady-state charging process and the end dynamic process; Step 2: Multi-dimensional feature quantitative analysis: Dynamic characteristic index calculation: Calculate voltage fluctuation rate and transient response time dynamic characteristic indexes; Steady-state characteristic index evaluation: Evaluate voltage deviation, power factor, voltage stability constraint, frequency deviation constraint, power factor constraint, current harmonic constraint, and transformer capacity constraint; Step 3: Aggregate effect modeling: Group characteristic modeling: establish an aggregation model of N charging piles; interaction impact analysis: calculate the coupling coefficient of the charging pile group; Step 4: Construction of evaluation indicator system: Single pile evaluation index: build a single pile evaluation index system; Group evaluation index: build a group evaluation index system; Step 5: Dynamic evaluation mechanism implementation: Evaluation cycle setting: set the evaluation cycle according to charging characteristics; dynamic weight adjustment: dynamically update the evaluation weight based on operating data.

2. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In the step 1, process feature identification is performed using the following formula: ψ(t)=|P(t)-P(t-1)|>ε, where P(t) is the power value at time t and ε is a threshold parameter.

3. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In the second step, the calculation of the dynamic characteristic index includes: Voltage fluctuation rate: ΔV = (V_max - V_min) / V_n × 100%; Transient response time: T r =t s -t0, Among them, t s is the moment when the system reaches steady state, and t0 is the initial moment of disturbance.

4. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In the step 2, the steady-state characteristic index evaluation includes: Voltage deviation: Power Factor: Voltage stability constraint: |U i -U ref |≤ΔU max ; Frequency deviation constraint: |ff nominal |≤Δf max ; Power factor constraint: PF ≥ 0.9; Current harmonic constraint: THD ≤ 5%; Transformer capacity constraint: P load +P EV ≤P rated .

5. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 3, the group characteristic modeling is performed using the following formula: total(t) =∑[α i ×P i(t) ], where α i Participation coefficient of charging pile i.

6. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 3, the interaction impact analysis is performed using the following formula:

7. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 4, the single pile evaluation index is calculated using the following formula: single =w 1 ×ΔV+w 2 ×T r +w 3 ×δV+w 4 ×PF.

8. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 4, the group evaluation index is calculated using the following formula: group =S single ×K c ×f(N), where f(N) is the scale correction function.

9. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 5, the evaluation period is set by the following formula: T = max (T r )+T stable .

10. The method for analyzing and evaluating the grid-connected properties of super charging piles based on a dynamic-steady-state process according to claim 1, characterized in that: In step 5, the dynamic weight adjustment is performed using the following formula: Among them, E k is the evaluation error of the kth cycle.

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