Electric vehicle cluster multistage regulation method and system supporting power grid frequency modulation

Abstract

The invention discloses an electric vehicle cluster multi-stage regulation method and system supporting power grid frequency modulation, and relates to the technical field of power distribution networks, and the method comprises the steps that a power grid dispatching center calculates the total power required by frequency modulation; dividing the electric vehicle cluster into a plurality of electric vehicle sub-clusters according to the time when the electric vehicles access the power grid; the maximum frequency modulation capacity which can be provided by an electric vehicle participating in power grid frequency modulation is calculated according to the current SOC state of the electric vehicle, the maximum frequency modulation capacity provided by each sub-cluster is calculated, and the required frequency modulation total power is distributed to each sub-cluster in proportion; and distributing the received required frequency modulation capacity information to each electric vehicle capable of participating in the frequency modulation of the power grid in the sub-cluster according to a proportion. According to the method, the actual problems encountered when large-scale electric vehicles are accessed to the power grid to participate in frequency modulation are solved, a part of calculation and optimization tasks of the centralized dispatching center are distributed to the edge side, and the problem that calculation and communication burdens of the dispatching center are too large is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution network, and in particular to a multi-level regulation method and system for electric vehicle clusters supporting power grid frequency modulation. Background Art

[0002] Under the strategic goal of "dual carbon", my country's power energy structure will shift from traditional fossil energy to renewable energy, such as wind energy and solar energy, in order to solve the problems of environmental pollution and resource depletion. Therefore, the penetration rate of renewable energy in the power system has gradually increased in recent years. However, with the large-scale access of renewable energy to the power grid, its randomness and volatility will have a strong impact on the power system, which will in turn affect the power quality of the power grid and the stable operation of the power system frequency. Therefore, it is necessary to adopt certain frequency modulation measures to enable the power system to better absorb renewable energy.

[0003] In the power system, common frequency regulation resources mainly include traditional conventional units and energy storage systems, but the former has inherent defects such as slow response speed, dead zone limitation, and ramp rate limitation, while the latter has a long construction period and expensive construction funds. They all have certain defects and shortcomings and are not the optimal solution to solve the frequency stability problem caused by the high proportion of renewable energy access to the power system. With the rapid development of electric vehicles and the increasing maturity of V2G technology, coupled with the characteristics of low operating costs, fast response signal speed and sufficient number of electric vehicles, electric vehicles can be used as a flexible load on the one hand, and as an energy storage device to discharge the power system on the other hand.

[0004] However, large-scale access of electric vehicles to the power grid will also bring new problems, such as the random access of electric vehicles, the willingness of electric vehicles to participate in the frequency regulation of the power system, and the ability of electric vehicles to participate in the frequency regulation of the power system. It is necessary to propose a multi-level regulation strategy for electric vehicle clusters that supports grid frequency regulation to solve these problems, thereby achieving a win-win situation for electric vehicle users and the power system. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is: how to solve the problems of random access of electric vehicles to the power grid on a large scale, the willingness of electric vehicles to participate in power system frequency regulation, the ability of electric vehicles to participate in power system frequency regulation, etc.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a multi-level regulation method for electric vehicle clusters supporting grid frequency modulation, comprising: a grid dispatching center calculates the total power required for frequency modulation, and sends the total power information required for frequency modulation to an electric vehicle centralized control center; after receiving the total power required for frequency modulation, the electric vehicle centralized control center determines whether the electric vehicle can participate in grid frequency modulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in frequency modulation, and divides the electric vehicle cluster into multiple electric vehicle sub-clusters, and at regular intervals, dynamically re-dividing the sub-clusters while considering the limit on the number of charge and discharge times; the electric vehicles participating in grid frequency modulation calculate the maximum frequency modulation capacity that can be provided by each electric vehicle according to its current SOC state, calculate the maximum frequency modulation capacity provided by each sub-cluster, and distribute the required total frequency modulation power to each sub-cluster in proportion; the sub-cluster distributes the received required frequency modulation capacity information in proportion to each electric vehicle that can participate in grid frequency modulation, so as to complete large-scale electric vehicles participating in grid auxiliary frequency modulation.

[0008] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency regulation described in the present invention, wherein: the reliability index includes the user's reliability index ω l It is the ratio of the actual frequency regulation time to the expected time since the user first participated in the grid frequency regulation, 0≤ω l ≤1,ω l The specific calculation formula is expressed as:

[0009]

[0010] Among them, ω l is the reliability index of the user, λ l is the number of times that electric vehicle l leaves the grid before the set expected departure time during the frequency regulation period, l is the total number of times that electric vehicle l participates in grid frequency regulation; l When it is less than the reliability index threshold, electric vehicle l cannot participate in grid frequency regulation.

[0011] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency regulation described in the present invention, wherein: the time margin for participating in frequency regulation includes the time margin for participating in frequency regulation θ l The ability of electric vehicles to participate in grid frequency regulation is expressed as:

[0012]

[0013] Among them, t l,min For electric vehicle l with maximum power P max Charging time, SOC l,expis the desired state of charge for the electric vehicle, is the charge state of the electric vehicle when it is initially connected to the grid, E l is the rated capacity of the electric vehicle, t l,exp is the time when the electric vehicle is expected to leave the grid, t l,0 is the time when the electric vehicle is initially connected to the grid, θ l is the time margin for frequency modulation; when θ l >1, that is, t l,exp -t l,0 >t l,min , indicating that the electric vehicle is fully charged within the stay time, which also means that the electric vehicle has the ability to participate in the grid frequency regulation. l With the increase in the number of electric vehicles, the ability of electric vehicles to participate in grid frequency regulation is enhanced.

[0014] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency modulation described in the present invention, wherein: the charge and discharge times limit includes that since electric vehicles are firstly used as transportation tools and secondly as auxiliary grid frequency modulation, it is necessary to first meet the needs of electric vehicle users, that is, to reach the expected battery charge state before the expected departure time, and the electric vehicles in the cluster are divided into a frequency modulation charging group, a frequency modulation discharging group, and a unidirectional charging group. After the electric vehicles are connected to the grid, the sub-clusters re-count the current SOC states of each electric vehicle every ten minutes and determine whether to switch between groups. The determination is based on the following Maximum power allowed within the time allowed If the electric vehicle user's expectations are met, That is, calculate the minimum charge state that should be achieved at present like At the next moment, the electric vehicle enters the frequency modulation group, otherwise it enters the one-way charging group.

[0015] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency regulation described in the present invention, the minimum charge state is expressed as:

[0016]

[0017] Among them, t0 is the time when the electric vehicle is initially connected to the power grid, and Δt is the time interval, that is, the SOC state of the electric vehicle is recalculated at a certain time interval to determine whether to switch groups. is the charge state of the i-th electric vehicle in cluster j after it enters the grid at time t0 and passes through Δt. is the desired state of charge of the i-th electric vehicle in cluster j, is the maximum charging and discharging power value of the i-th electric vehicle in the j-cluster, is the battery capacity of the i-th electric vehicle in cluster j, η c Charging efficiency for electric vehicles, is the expected departure time of the ith electric vehicle in the jth cluster, j is the jth electric vehicle sub-cluster, i is the ith electric vehicle in the jth electric vehicle sub-cluster; SOC min The lower limit of the state of charge of the electric vehicle battery, SOC max The upper limit of the battery charge state of the electric vehicle is defined as is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k, expressed as:

[0018]

[0019] in, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k-1, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k-1; when the number of charge-discharge conversions When the SOC is less than the charge-discharge conversion number threshold, the electric vehicle currently in the frequency modulation discharge group first determines its own SOC state. If it is greater than the SOC min And the frequency modulation power at the next moment is greater than 0, it is still classified into the frequency modulation discharge group at the next moment. If it is not greater than SOC min Or the frequency modulation power is less than 0, then it will be divided into the frequency modulation charging group at the next moment. If the SOC state of the electric vehicle in the frequency modulation charging group is less than SOC max If the frequency modulation power at the next moment is less than 0, it will still be included in the frequency modulation charging group at the next moment. max Or the frequency modulation power is greater than 0, then it will be classified into the frequency modulation discharge group at the next moment; when the charge and discharge conversion times When the charge-discharge conversion times are greater than or equal to the threshold, and the electric vehicle's own SOC state is at SOC min and SOC max If the electric vehicle is divided into two groups at the next moment, the group into which the electric vehicle is divided is consistent with the group at the current moment.

[0020] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency regulation described in the present invention, wherein: the maximum frequency regulation capacity includes, the frequency regulation capacity that a single electric vehicle can provide is expressed as:

[0021]

[0022] in, is the adjustable frequency capacity of the ith electric vehicle in the jth subcluster at time k+1, To increase the capacity, To adjust the capacity downward, is the actual power of the i-th electric vehicle in the j-th sub-cluster at time k, is the maximum charging and discharging power of the i-th electric vehicle in the j-th sub-cluster, α, β are weight coefficients, expressed as:

[0023]

[0024] The maximum frequency regulation capacity that each subcluster can provide is the sum of the adjustable capacities of all electric vehicles that can participate in frequency regulation within the subcluster. The total adjustable upward capacity and adjustable downward capacity must be calculated separately.

[0025] As a preferred solution of the multi-level regulation method of electric vehicle cluster supporting grid frequency regulation described in the present invention, wherein: the required total frequency regulation power is proportionally distributed to each sub-cluster including calculating the required total frequency regulation power expressed as:

[0026] P total,k+1 =-K∫Δf

[0027] Among them, K is the frequency modulation power ratio coefficient, Δf is the frequency that the power grid needs to adjust; when Δf < 0, the power required for frequency modulation P according to the formula total,k+1 > 0, electric vehicles need to output power to the grid, that is, electric vehicles participating in frequency regulation need to discharge to provide adjustable capacity like All electric vehicles discharge at the maximum power within the controllable range, and the remaining frequency modulation power is provided by traditional units. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is expressed as:

[0028]

[0029] Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth sub-cluster; the frequency regulation task assigned by the sub-cluster to each electric vehicle in the cluster is expressed as:

[0030]

[0031] in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η d is the discharge efficiency of the electric vehicle; when Δf>0, the power P required for frequency modulation is obtained according to the formula total,k+1 <0, electric vehicles need to obtain power from the grid, that is, electric vehicles need to be charged to provide adjustable capacity like All electric vehicles are charged at the maximum power within the controllable range, and the remaining frequency modulation power is provided by traditional units. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is expressed as:

[0032]

[0033] Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth sub-cluster; the frequency regulation task assigned by the sub-cluster to each electric vehicle in the cluster is expressed as:

[0034]

[0035] in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η c Charging efficiency for electric vehicles.

[0036] Another object of the present invention is to provide a system for a multi-level regulation method of an electric vehicle cluster supporting grid frequency modulation, which can solve the problem of multi-level regulation of an electric vehicle cluster supporting grid frequency modulation by constructing a multi-level regulation system for an electric vehicle cluster.

[0037] To solve the above technical problems, the present invention provides the following technical solutions: a multi-level regulation system for electric vehicle clusters supporting grid frequency modulation, comprising a data acquisition module, a cluster division module, a power division module and a sub-cluster internal power division module; the data acquisition module is used for the grid dispatching center to calculate the total power required for frequency modulation, and send the total power information required for frequency modulation to the electric vehicle centralized control center; the cluster division module is used for the electric vehicle centralized control center to determine whether the electric vehicle can participate in grid frequency modulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in frequency modulation after receiving the total power required for frequency modulation, and to divide the electric vehicle cluster into multiple electric vehicle sub-clusters, and at a certain interval, dynamically divide the sub-clusters again under the condition of considering the limit of the number of charge and discharge times; the power division module is used for calculating the maximum frequency modulation capacity that can be provided by each electric vehicle participating in grid frequency modulation according to the current SOC state of the electric vehicle, calculating the maximum frequency modulation capacity provided by each sub-cluster, and distributing the required total frequency modulation power to each sub-cluster in proportion; the sub-cluster internal power division module is used for distributing the received required frequency modulation capacity information to each electric vehicle that can participate in grid frequency modulation in proportion within the sub-cluster, so as to complete the large-scale electric vehicle participation in grid auxiliary frequency modulation.

[0038] A computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned multi-level regulation method for electric vehicle clusters supporting grid frequency regulation are implemented.

[0039] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a multi-level regulation method for an electric vehicle cluster supporting grid frequency regulation as described above.

[0040] The beneficial effects of the present invention are as follows: the multi-level regulation method for electric vehicle clusters supporting grid frequency regulation provided by the present invention can well solve the practical problems encountered by large-scale electric vehicles accessing the grid to participate in frequency regulation, and allocate part of the calculation and optimization tasks of the centralized dispatching center to the edge side, thereby alleviating the problem of excessive calculation and communication burden of the dispatching center; comprehensively considering various factors, the designed multi-level regulation strategy is more in line with actual life situations and more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0042] Figure 1 A flowchart of an electric vehicle cluster participating in grid frequency regulation in a multi-level regulation method for an electric vehicle cluster supporting grid frequency regulation provided in a first embodiment of the present invention.

[0043] Figure 2 A multi-level regulation strategy diagram of an electric vehicle cluster of an electric vehicle cluster multi-level regulation method supporting grid frequency regulation is provided in accordance with the first embodiment of the present invention.

[0044] Figure 3 A structural diagram of a multi-level regulation system for an electric vehicle cluster supporting grid frequency regulation provided in a second embodiment of the present invention.

[0045] Figure 4 A comparison diagram of network losses before and after electric vehicles participate in frequency regulation in a multi-level regulation method for electric vehicle clusters supporting grid frequency regulation provided in a third embodiment of the present invention.

[0046] Figure 5 A frequency deviation diagram of a power grid of a multi-stage regulation method for an electric vehicle cluster supporting power grid frequency regulation provided in a third embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0049] Example 1, reference Figure 1 and Figure 2, which is the first embodiment of the present invention, and provides a multi-level regulation method for electric vehicle clusters supporting grid frequency regulation, including: the grid dispatching center calculates the total power required for frequency regulation, and sends the total power information required for frequency regulation to the electric vehicle centralized control center; after receiving the total power required for frequency regulation, the electric vehicle centralized control center determines whether the electric vehicle can participate in grid frequency regulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in frequency regulation, and divides the electric vehicle cluster into multiple electric vehicle sub-clusters, and at regular intervals, dynamically re-dividing the sub-clusters while considering the limit of the number of charge and discharge times; the electric vehicles participating in grid frequency regulation calculate the maximum frequency regulation capacity that can be provided by each electric vehicle according to its current SOC state, calculate the maximum frequency regulation capacity provided by each sub-cluster, and distribute the required total frequency regulation power to each sub-cluster in proportion; the sub-cluster distributes the received required frequency regulation capacity information in proportion to each electric vehicle that can participate in grid frequency regulation, so as to complete large-scale electric vehicles participating in grid auxiliary frequency regulation.

[0050] The grid dispatching center calculates the total power required for frequency regulation, and then sends the information to the electric vehicle centralized control center; after receiving the total power required for frequency regulation, the electric vehicle centralized control center determines whether the electric vehicle can participate in grid frequency regulation based on the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in frequency regulation. At the same time, the electric vehicle cluster is divided into multiple electric vehicle sub-clusters, and the sub-clusters are dynamically re-divided at regular intervals while considering the limit on the number of charge and discharge times. The electric vehicles that can participate in frequency regulation calculate the maximum frequency regulation capacity that each can provide based on their current SOC status, and calculate the maximum frequency regulation capacity that each sub-cluster can provide, and then distribute the required total frequency regulation power to each sub-cluster in proportion. The required frequency regulation capacity information received within the sub-cluster is distributed in proportion to each electric vehicle that can participate in grid frequency regulation, completing large-scale electric vehicle participation in grid-assisted frequency regulation. Such as Figure 1 and Figure 2 shown.

[0051] (1) Reliability indicators.

[0052] User reliability indexω l It is the ratio of the actual frequency regulation time to the expected time since the user first participated in the power grid frequency regulation, 0≤ω l ≤1, and ω l The closer it is to 1, the higher the reliability of the electric vehicle user. l The specific calculation formula is as follows:

[0053]

[0054] Among them, λl represents the number of times that electric vehicle l leaves the grid before the set expected departure time during the frequency regulation period, χ l represents the total number of times electric vehicle l participates in grid frequency regulation, ω l is the reliability index of the user. l When ω<0.5, it means that in the past, the electric car had a 50% chance of leaving before the set expected time, and the user reliability is low. l When <0.4, electric vehicle l cannot participate in grid frequency regulation. l It can be set according to actual conditions, and is generally selected not to exceed 0.5. The reliability index threshold selected in the present invention is 0.4.

[0055] (2) Participation in frequency modulation time margin.

[0056] The time margin θ for frequency modulation l It indicates the ability of electric vehicles to participate in grid frequency regulation. The specific calculation formula is as follows:

[0057]

[0058]

[0059] Among them, t l,min For electric vehicle l with maximum power P max Charging time, SOC l,exp is the desired state of charge for the electric vehicle, is the charge state of the electric vehicle when it is initially connected to the grid, E l is the rated capacity of the electric vehicle, t l,exp is the time when the electric vehicle is expected to leave the grid, t l,0 is the time when the electric vehicle is initially connected to the grid, θ l The time margin for participating in frequency modulation.

[0060] It can be seen that θ l It is related to the dwell time and the shortest charging time of electric vehicles. In theory, it is considered that θ l >1, that is, t l,exp -t l,0 >t l,min , indicating that the electric vehicle can be fully charged within the stay time, which also means that the electric vehicle has the ability to participate in the grid frequency regulation. l With the increase in the number of electric vehicles, the ability of electric vehicles to participate in grid frequency regulation is enhanced.

[0061] (3) Limitation on the number of charge and discharge conversions.

[0062] Since electric vehicles are primarily used as a means of transportation and secondly as an auxiliary grid frequency regulation, the needs of electric vehicle users must be met first, that is, the expected battery charge state must be reached before the expected departure time. Based on this, the electric vehicles in the cluster are divided into a frequency regulation charging group, a frequency regulation discharge group, and a unidirectional charging group. After the electric vehicles are connected to the grid, the sub-clusters re-count the current SOC state of each electric vehicle every ten minutes and determine whether to switch between groups. The judgment is based on: Maximum power allowed within the time allowed If the electric vehicle users can meet their expectations, That is, calculate the minimum charge state that should be achieved at present like At the next moment, the electric vehicle enters the frequency modulation group, otherwise it enters the one-way charging group.

[0063] in, The calculation formula is as follows:

[0064]

[0065] Among them, t0 is the time when the electric vehicle is initially connected to the power grid, and Δt is the time interval, that is, the SOC state of the electric vehicle is recalculated at a certain time interval to determine whether to switch groups. is the charge state of the i-th electric vehicle in cluster j after it enters the grid at time t0 and passes through Δt. is the desired state of charge of the i-th electric vehicle in cluster j, is the maximum charging and discharging power value of the i-th electric vehicle in the j-cluster, is the battery capacity of the i-th electric vehicle in cluster j, η c Charging efficiency for electric vehicles, is the expected departure time of the i-th electric vehicle of the j-th electric vehicle sub-cluster, j is the j-th electric vehicle sub-cluster, and i is the i-th electric vehicle of the j-th electric vehicle sub-cluster.

[0066] In order to avoid the reduction of electric vehicle battery life due to low charge and high discharge, the SOC state of the electric vehicle is limited to charge and discharge within the allowable range. min The lower limit of the state of charge of the electric vehicle battery, SOC max is the upper limit of the battery charge state of the electric vehicle. In addition, during the frequency modulation process, in order to meet the demand, the battery of the electric vehicle will be frequently charged and discharged, which will also affect the battery life. Therefore, it is necessary to limit the number of charge and discharge conversions. The specific operation is to define It represents the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k. The specific calculation formula is as follows:

[0067]

[0068] in, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k-1, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k-1.

[0069] The rules for switching between charging and discharging groups of electric vehicles considering the limit of charging and discharging times are as follows:

[0070] When the charge and discharge conversion times When the electric vehicle currently in the frequency modulation discharge group first determines its own SOC state, if it is greater than SOC min If the frequency modulation power at the next moment is greater than 0, it will still be classified into the frequency modulation discharge group at the next moment; if it is not greater than SOC min Or the frequency modulation power is less than 0, then it will be assigned to the frequency modulation charging group at the next moment. If the SOC state of the electric vehicle in the frequency modulation charging group is less than SOC max If the frequency modulation power at the next moment is less than 0, it will still be classified into the frequency modulation charging group at the next moment; if it is not greater than SOC max Or if the frequency modulation power is greater than 0, it will be classified into the frequency modulation discharge group at the next moment.

[0071] When the charge and discharge conversion times When the electric vehicle's own SOC state is at SOC min and SOC max The group that the electric vehicle is divided into at the next moment is consistent with the group at the current moment. The specific setting requirement for the number of charge-discharge conversions is a number greater than 1, generally 4-7. If it is set too high, it loses the meaning of protecting the electric vehicle battery by limiting the number of charge-discharge conversions. If it is set too low, it is easy for the electric vehicle to reach the conversion limit too quickly, which is not conducive to participating in the grid frequency modulation. The threshold value of the charge-discharge conversion number of the present invention is 5.

[0072] The maximum frequency regulation capacity that each electric vehicle can provide is calculated based on its current SOC state. The maximum frequency regulation capacity provided by each sub-cluster is calculated. The frequency regulation capacity that a single electric vehicle can provide is calculated as follows:

[0073]

[0074] in, represents the adjustable frequency capacity of the ith electric vehicle in the jth subcluster at time k+1, Indicates that the capacity can be adjusted upward. Indicates that the capacity can be reduced. represents the actual power of the i-th electric vehicle in the j-th sub-cluster at time k, represents the maximum charging and discharging power of the i-th electric vehicle in the j-th sub-cluster, α and β represent weight coefficients, and are calculated as follows:

[0075]

[0076] The maximum frequency regulation capacity that each subcluster can provide is the sum of the adjustable capacities of each electric vehicle that can participate in frequency regulation within the subcluster. The total adjustable upward capacity and adjustable downward capacity must be calculated separately.

[0077] The total power required for frequency regulation is then allocated to each sub-cluster in proportion. The former calculation is mainly used for proportional allocation, while the latter calculation is mainly used to determine whether traditional units need to be added to work together to achieve frequency regulation;

[0078] The sub-cluster will distribute the required frequency regulation capacity information received in proportion to each electric vehicle that can participate in grid frequency regulation, thereby completing the large-scale participation of electric vehicles in grid auxiliary frequency regulation.

[0079] The strategy for allocating the frequency regulation tasks of electric vehicles is to allocate them in proportion. The specific allocation process is as follows:

[0080] First calculate the power P required for frequency modulation total,k+1 :

[0081] P total,k+1 = -K∫Δf (9)

[0082] Among them, K is the frequency modulation power proportional coefficient, and Δf is the frequency that the power grid needs to adjust.

[0083] When Δf<0, according to the calculation formula (6), the power P required for frequency modulation total,k+1 > 0, electric vehicles need to output power to the grid, that is, electric vehicles participating in frequency regulation need to discharge to provide adjustable capacity like If , all electric vehicles discharge at the maximum power within the controllable range, where the controllable range refers to the allowable charging and discharging power range that ensures that the real-time SOC state of the electric vehicle is between the set upper and lower limits of the battery charge state, and the remaining required frequency modulation power is provided by the traditional unit. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is as follows:

[0084]

[0085] Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, It is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster.

[0086] Then, considering that the controllable capacity of electric vehicles directly determines the frequency regulation capability of electric vehicles, the larger the controllable frequency regulation capacity, the higher the frequency regulation priority, and the larger the frequency regulation task received. Based on this idea, the frequency regulation task assigned by the sub-cluster to each electric vehicle in the cluster is calculated as follows:

[0087]

[0088] in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η d is the discharge efficiency of electric vehicles.

[0089] Similarly, when Δf>0, the power P required for frequency modulation can be obtained according to formula (6): total,k+1 <0, at this time, the electric vehicle needs to obtain power from the grid, that is, the electric vehicle needs to be charged, providing adjustable capacity like If all electric vehicles are charged at the maximum power within the controllable range, the remaining frequency modulation power is provided by the traditional unit. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is as follows:

[0090]

[0091] Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, It is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster.

[0092] The frequency modulation task assigned by the sub-cluster to each electric vehicle within the cluster is calculated as follows:

[0093]

[0094] in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η c Charging efficiency for electric vehicles.

[0095] Example 2, reference Figure 3 , which is the second embodiment of the present invention, is different from the previous embodiment in that it provides an electric vehicle cluster multi-level regulation system supporting grid frequency modulation, including: a data acquisition module, a cluster division module, a power division module and a sub-cluster internal power division module.

[0096] The data acquisition module is used by the power grid dispatching center to calculate the total power required for frequency regulation and send the total power information required for frequency regulation to the electric vehicle centralized control center.

[0097] The cluster division module is used for the electric vehicle centralized control center to determine whether the electric vehicle can participate in the grid frequency regulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in the frequency regulation after receiving the total power required for the frequency regulation. At the same time, the electric vehicle cluster is divided into multiple electric vehicle sub-clusters. At the same time, the sub-clusters are dynamically re-divided at regular intervals while considering the limit on the number of charge and discharge times.

[0098] The power division module is used to calculate the maximum frequency regulation capacity that each electric vehicle can provide according to its current SOC state, calculate the maximum frequency regulation capacity provided by each sub-cluster, and allocate the required total frequency regulation power to each sub-cluster in proportion.

[0099] The sub-cluster internal power division module is used to distribute the required frequency regulation capacity information received within the sub-cluster in proportion to each electric vehicle that can participate in the grid frequency regulation, so as to complete the large-scale participation of electric vehicles in the grid auxiliary frequency regulation.

[0100] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0101] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0102] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0103] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0104] Example 3, reference Figure 4 and Figure 5 , which is the third embodiment of the present invention, and which is different from the first two embodiments in that it is used to verify and illustrate the technical effects adopted in the present invention, so as to verify the real effects of this method.

[0105] The comparison of total network loss before and after electric vehicles participate in frequency regulation is shown in the figure below: Figure 4 As shown, it can be seen that the present invention can effectively reduce network loss.

[0106] In addition, according to the following Figure 5 It can be seen that when electric vehicles participate in the grid frequency regulation, the maximum and minimum values ​​of the grid frequency deviation are smaller than the case where no electric vehicles participate in the grid frequency regulation. And through data analysis, it can be known that when electric vehicles participate in the grid frequency regulation, the root mean square value of the grid frequency change is smaller. It can be seen that when electric vehicles participate in the grid frequency regulation, the system frequency fluctuation is more stable and has a better frequency regulation effect.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation, characterized in that: include, The power grid dispatching center calculates the total power required for frequency regulation and sends the total power information required for frequency regulation to the electric vehicle centralized control center; After receiving the total power required for frequency modulation, the electric vehicle centralized control center determines whether the electric vehicle can participate in the grid frequency modulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in the frequency modulation. At the same time, the electric vehicle cluster is divided into multiple electric vehicle sub-clusters. At a certain interval, the sub-clusters are dynamically divided again under the consideration of the limit of the number of charge and discharge times. The electric vehicles participating in the grid frequency regulation calculate the maximum frequency regulation capacity that each can provide according to their current SOC status, calculate the maximum frequency regulation capacity provided by each sub-cluster, and distribute the required total frequency regulation power to each sub-cluster in proportion; The sub-cluster will distribute the required frequency regulation capacity information received in proportion to each electric vehicle that can participate in grid frequency regulation, thereby completing the large-scale participation of electric vehicles in grid auxiliary frequency regulation.

2. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 1, characterized in that: The reliability index includes the user's reliability index ω l It is the ratio of the actual frequency regulation time to the expected time since the user first participated in the grid frequency regulation, 0≤ω l ≤1,ω l The specific calculation formula is expressed as: Among them, ω l is the reliability index of the user, λ l is the number of times that electric vehicle l leaves the grid before the set expected departure time during the frequency regulation period, l The total number of times that electric vehicle l participates in grid frequency regulation; ω l When it is less than the reliability index threshold, electric vehicle l cannot participate in grid frequency regulation.

3. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 2, characterized in that: The time margin for participating in frequency modulation includes the time margin θ for participating in frequency modulation. l The ability of electric vehicles to participate in grid frequency regulation is expressed as, Among them, t l,min For electric vehicle l with maximum power P max Charging time, SOC l,exp is the desired state of charge for the electric vehicle, is the charge state of the electric vehicle when it is initially connected to the grid, E l is the rated capacity of the electric vehicle, t l,exp is the time when the electric vehicle is expected to leave the grid, t l,0 is the time when the electric vehicle is initially connected to the grid, θ l The time margin for participating in frequency modulation; When θ l >1, that is, t l,exp -t l,0 >t l,min , indicating that the electric vehicle is fully charged within the stay time, which also means that the electric vehicle has the ability to participate in the grid frequency regulation. l With the increase in the number of electric vehicles, the ability of electric vehicles to participate in grid frequency regulation is enhanced.

4. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 3, characterized in that: The charge and discharge times limit includes that since electric vehicles are first used as transportation and secondly as auxiliary grid frequency regulation, it is necessary to first meet the needs of electric vehicle users, that is, to reach the expected battery charge state before the expected departure time, and the electric vehicles in the cluster are divided into a frequency regulation charging group, a frequency regulation discharge group, and a unidirectional charging group. After the electric vehicles are connected to the grid, the sub-clusters re-count the current SOC status of each electric vehicle every ten minutes and determine whether to switch between groups. The judgment is based on the following Maximum power allowed within the time allowed If the electric vehicle user's expectations are met, That is, calculate the minimum charge state that should be achieved at present like At the next moment, the electric vehicle enters the frequency modulation group, otherwise it enters the one-way charging group.

5. The multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 4, characterized in that: The minimum charge state is expressed as, Among them, t0 is the time when the electric vehicle is initially connected to the power grid, and Δt is the time interval, that is, the SOC state of the electric vehicle is recalculated at a certain time interval to determine whether to switch groups. is the charge state of the i-th electric vehicle in cluster j after it enters the grid at time t0 and passes through Δt. is the desired state of charge of the i-th electric vehicle in cluster j, is the maximum charging and discharging power value of the i-th electric vehicle in the j-cluster, is the battery capacity of the i-th electric vehicle in cluster j, η c Charging efficiency for electric vehicles, is the expected departure time of the ith electric vehicle of the jth cluster, j is the jth electric vehicle sub-cluster, and i is the ith electric vehicle of the jth electric vehicle sub-cluster; SOC min The lower limit of the state of charge of the electric vehicle battery, SOC max The upper limit of the battery charge state of the electric vehicle is defined as is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k, expressed as, in, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k, is the charging and discharging power value of the i-th electric vehicle in the j-th cluster at time k-1, is the number of charge-discharge conversions of the i-th electric vehicle in the j-th cluster at time k-1; When the charge and discharge conversion times When the SOC is less than the charge-discharge conversion number threshold, the electric vehicle currently in the frequency modulation discharge group first determines its own SOC state. If it is greater than the SOC min And the frequency modulation power at the next moment is greater than 0, it is still classified into the frequency modulation discharge group at the next moment. If it is not greater than SOC min Or the frequency modulation power is less than 0, then it will be divided into the frequency modulation charging group at the next moment. If the SOC state of the electric vehicle in the frequency modulation charging group is less than SOC max If the frequency modulation power at the next moment is less than 0, it will still be included in the frequency modulation charging group at the next moment. max Or if the frequency modulation power is greater than 0, it will be classified into the frequency modulation discharge group at the next moment; When the charge and discharge conversion times When the charge-discharge conversion times are greater than or equal to the threshold, and the electric vehicle's own SOC state is at SOC min and SOC max If the electric vehicle is divided into two groups at the next moment, the group into which the electric vehicle is divided is consistent with the group at the current moment.

6. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 5, characterized in that: The maximum frequency regulation capacity includes the frequency regulation capacity that a single electric vehicle can provide and is calculated as follows: in, is the adjustable frequency capacity of the ith electric vehicle in the jth subcluster at time k+1, To increase the capacity, To adjust the capacity downward, is the actual power of the i-th electric vehicle in the j-th sub-cluster at time k, is the maximum charging and discharging power of the i-th electric vehicle in the j-th sub-cluster, α, β are weight coefficients, expressed as, The maximum frequency regulation capacity that each subcluster can provide is the sum of the adjustable capacities of all electric vehicles that can participate in frequency regulation within the subcluster. The total adjustable upward capacity and adjustable downward capacity must be calculated separately.

7. A multi-level regulation method for electric vehicle clusters supporting grid frequency modulation as claimed in claim 6, characterized in that: The method of allocating the required total frequency modulation power to each sub-cluster in proportion includes calculating the required total frequency modulation power expressed as: P total,k+1 =-K∫Δf Among them, K is the frequency modulation power ratio coefficient, Δf is the frequency that the power grid needs to adjust; When Δf<0, the power P required for frequency modulation is total,k+1 > 0, electric vehicles need to output power to the grid, that is, electric vehicles participating in frequency modulation need to discharge to provide adjustable capacity like All electric vehicles discharge at the maximum power within the controllable range, and the remaining frequency modulation power is provided by traditional units. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is expressed as: Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, The adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster; The frequency modulation task assigned by the sub-cluster to each electric vehicle within the cluster is expressed as: in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η d is the discharge efficiency of electric vehicles; When Δf>0, the power P required for frequency modulation is obtained according to the formula total,k+1 <0, electric vehicles need to obtain power from the grid, that is, electric vehicles need to be charged to provide adjustable capacity like All electric vehicles are charged at the maximum power within the controllable range, and the remaining frequency modulation power is provided by traditional units. The power required for frequency modulation at the next moment is allocated to each cluster in proportion, and the allocation method is expressed as: Among them, P total,k+1 is the total FM power required at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, The total adjustable capacity that can be provided by all electric vehicles that can participate in frequency regulation, The adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster; The frequency modulation task assigned by the sub-cluster to each electric vehicle within the cluster is expressed as: in, is the frequency modulation task of the i-th electric vehicle in the j-th subcluster at time k+1, is the frequency modulation power required to be provided by the j-th sub-cluster at time k+1, is the adjustable capacity that can be provided by the electric vehicles participating in frequency regulation in the jth subcluster, is the upward frequency regulation capacity that the i-th electric vehicle in the j-th sub-cluster can provide at time k+1, η c Charging efficiency for electric vehicles.

8. A system using a multi-level regulation method for electric vehicle clusters supporting grid frequency regulation as claimed in any one of claims 1 to 7, characterized in that: Including, data acquisition module, cluster division module, power division module and sub-cluster internal power division module; The data acquisition module is used by the power grid dispatching center to calculate the total power required for frequency modulation and send the total power information required for frequency modulation to the electric vehicle centralized control center; The cluster division module is used for the electric vehicle centralized control center to determine whether the electric vehicle can participate in the grid frequency modulation according to the time when the electric vehicle is connected to the grid, the reliability index of the electric vehicle user, and the time margin for the electric vehicle to participate in the frequency modulation after receiving the total power required for the frequency modulation, and to divide the electric vehicle cluster into multiple electric vehicle sub-clusters, and to dynamically re-divide the sub-clusters at regular intervals while considering the limit of the number of charge and discharge times; The power division module is used to calculate the maximum frequency modulation capacity that each electric vehicle participating in the grid frequency modulation can provide according to its current SOC state, calculate the maximum frequency modulation capacity provided by each sub-cluster, and distribute the required total frequency modulation power to each sub-cluster in proportion; The sub-cluster internal power division module is used to distribute the received required frequency regulation capacity information to each electric vehicle that can participate in the grid frequency regulation in proportion within the sub-cluster, so as to complete the participation of large-scale electric vehicles in grid auxiliary frequency regulation.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a multi-level regulation method for an electric vehicle cluster supporting grid frequency regulation as described in any one of claims 1 to 7 are implemented.

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 steps of a multi-level regulation method for an electric vehicle cluster supporting grid frequency regulation as described in any one of claims 1 to 7 are implemented.

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