WO2019153793A1

WO2019153793A1 - Electric automobile charging control method and storage medium

Info

Publication number: WO2019153793A1
Application number: PCT/CN2018/111515
Authority: WO
Inventors: 陈良亮; 倪峰; 徐石明; 周静; 唐雾婺; 李骆; 宋杰; 汤延祺; 杨凤坤; 朱庆; 陈嘉栋
Original assignee: 国电南瑞科技股份有限公司; 国网上海市电力公司; 国网浙江省电力有限公司; 国电南瑞南京控制系统有限公司; 国家电网有限公司
Priority date: 2018-02-08
Filing date: 2018-10-23
Publication date: 2019-08-15
Also published as: CN108407636A; CN108407636B

Abstract

Provided is an electric vehicle charging control method, comprising: measuring the frequency of the local electrical grid (101); adjusting a power output value according to said local electrical grid frequency (102).

Description

Electric vehicle charging control method and storage medium

Cross-reference to related applications

The present application is filed on the basis of the Chinese Patent Application No. 20110012 793, the entire disclosure of which is hereby incorporated by reference.

Technical field

The invention relates to an electric vehicle charging control technology, in particular to an electric vehicle charging control method.

Background technique

With the depletion of traditional energy sources such as oil and coal and the increasing environmental problems, the development of new energy technologies has become the common choice for solving energy problems around the world. As an important means to solve transportation, energy and the environment, the development of electric vehicles has become an important way to improve the competitiveness of China's automobile industry, ensure energy security and develop a low-carbon economy. Vigorously developing electric vehicles and accelerating the industrialization of energy-saving and new-energy vehicles are not only an inevitable choice for effectively coping with energy and environmental challenges, but also realizing the sustainable development of China's auto industry. They are also grasping strategic opportunities, shortening the gap with advanced countries, and realizing the automobile industry. Important initiatives and major strategic needs for leapfrog development.

A large number of electric vehicle charging will bring about a rapid increase in the power load, which will bring new power supply pressure to the power system. The random charging of a large number of electric vehicles will bring problems such as frequency reduction and branch capacity mismatch to the power grid. The development and application of electric vehicle interconnection and charging strategy can not only meet the user's charging needs but also serve as a system backup. Participating in system frequency adjustment is of great significance for improving grid power quality. The use of this charging strategy will enable electric vehicle users, charging facilities construction and operation companies, automobile companies and power grid companies to achieve a win-win situation.

How to extend the life of the battery and reduce the impact on the power grid, there is no effective solution.

Summary of the invention

Embodiments of the present application are expected to provide an electric vehicle charging control method capable of avoiding an impact of charging on a power grid.

The electric vehicle charging control method provided by the embodiment of the present application includes: detecting a local grid frequency; and adjusting a power output value according to the local grid frequency.

In an embodiment, the detecting the local grid frequency comprises: detecting a local grid frequency according to a detection period; and the detecting period is determined according to a first type of load fluctuation period in the power system.

In an embodiment, the adjusting the power output value according to the local grid frequency comprises:

The power output value is adjusted when the offset of the local grid frequency exceeds a preset threshold.

In an embodiment, the method further comprises: determining an initial response time;

The adjusting the power output value according to the local grid frequency comprises: adjusting a power output value according to the local grid frequency and the initial response time.

In an embodiment, the initial response time is determined based on the detection period and the number of charging devices.

In an embodiment, the adjusted maximum value of the power output value is determined according to a maximum charging power that the electric vehicle can provide and a preset charging demand.

In an embodiment, the adjusted maximum value of the power output value does not exceed the minimum charging power.

The minimum charging power

Minimum charging requirement to reach the preset charging demand before charging is terminated

among them,

Determined by the following formula:

among them,

The maximum value of electric vehicles that can be increased in Δt time

then

Satisfy:

among them,

Calculated as follows:

Where: Q _i is the battery capacity; η is the charging and discharging efficiency of the electric vehicle; T _i is the leaving time of the i-th electric vehicle;

The difference between the minimum allowable power and the current power at time t+Δt;

The current amount of electricity;

The maximum charging power that can be supplied by the charging device.

In an embodiment, the adjustment of the power output value is responsive according to a local grid frequency deviation condition, and the adjustment range of the power output value satisfies the following expression:

Where L represents the response level; α _l (l = 1, 2, ..., L) is the power adjustment coefficient, 0 < α ₁ ≤ α ₂ ≤ ... ≤ α _L <100%; δ _i (i = 1,2,...,L) is the response threshold of response level i; P _i is the available power of electric vehicle i, when Δf _t is positive, P _i is the maximum charging power that electric vehicle i can increase; when Δf _{When t} is negative, P _i is the maximum charging power that can be reduced by electric vehicle i; sign is a symbol function, and its representation is as follows:

among them,

Adjust the power for the total G2V of the electric car participating in the FM.

The technical solution of the embodiment of the present application is based on the monitoring of the grid frequency of the electric vehicle and the adjustment of the power output value, so as to reduce the power to replace the battery to supply power to the grid, on the one hand, avoiding the impact of charging on the grid; on the other hand, avoiding the electric power The frequent charging and discharging of the car's power battery extends the life of the battery.

DRAWINGS

1 is a block diagram of a distributed electric vehicle participating in a power grid frequency modulation according to an embodiment of the present application;

2 is a control structural diagram of an electric vehicle participating in a primary frequency adjustment of an electric grid according to an embodiment of the present application;

3 is a schematic flow chart of a charging control method for an electric vehicle according to an embodiment of the present application;

4 is a schematic diagram of charging control participating in frequency modulation according to an embodiment of the present application;

5 is a diagram showing an initial response time distribution of an electric vehicle according to an embodiment of the present application;

FIG. 6 is a diagram of a power response representation of an embodiment of the present application.

Detailed ways

The specific embodiments of the present invention will be further described in conjunction with the accompanying drawings, in order to help those skilled in the art to the present invention. Complete, accurate and in-depth understanding.

1 is a block diagram of a distributed electric vehicle participating in a power grid frequency modulation according to an embodiment of the present application, and an electric vehicle (as a charging device) responds according to a frequency deviation signal of a local power grid during charging, and reduces an electric vehicle when a frequency of the local power grid decreases. The charging power; when the frequency of the local power grid rises, the charging power of the electric vehicle is increased. The frequency measuring unit in the electric vehicle charging control device detects the local grid frequency once every period of time (ie, the detection period), and compares the obtained frequency with the rated frequency of the local power grid, if the offset degree exceeds the allowed limit range, Then the frequency response controller operates, according to the frequency offset response control strategy, the electric vehicle charging power (considering SOC) is adjusted accordingly, so that the grid frequency is gradually restored to stability; otherwise, the electric vehicle is normally charged according to the preset charging power. (ie, in a non-responsive state), no power adjustment is made.

Figure 2 shows the control structure diagram of the electric vehicle participating in the secondary frequency adjustment of the power grid. It can be seen that the participation of electric vehicles in the primary frequency adjustment of the power grid can be understood as the integration of the user's planned charging control and frequency droop control. The details can be summarized as follows: 1) Calculate the planned charging power and complete the charging demand of the electric vehicle user; 2) Design the charging droop, and realize the frequency droop control according to the frequency deviation.

Based on this, as shown in FIG. 3, the electric vehicle charging control method of the embodiment of the present application includes: step 101: detecting a local grid frequency; and step 102: adjusting a power output value according to the local grid frequency.

In an optional embodiment of the present application, the detecting the local grid frequency comprises: detecting a local grid frequency according to a detection period; and the detection period is determined according to a first type of load fluctuation period in the power system.

In this embodiment, the charging device detection period is determined according to a first type of load fluctuation period in the actual power system. The load in the actual power system changes all the time, and the in-depth analysis of this irregular load change law can be seen. It is actually a combination of several load variation laws. Conversely, this irregular load variation law can be decomposed into three types of regularly following load changes: the first type of load fluctuation period has a small variation range, the change period is short, generally within 10s; the second type of load The fluctuation period has a large fluctuation range, and the period is long, generally 10s-3min; the third type of load fluctuation period has the largest variation and the longest period. Accordingly, the active power and frequency adjustment of the power system can be roughly divided into three types: one frequency modulation, two frequency modulation, and three frequency frequency modulation. The frequency offset caused by the first type of load fluctuation cycle change load can be automatically adjusted by all genset governors; the second type of load fluctuation cycle change the frequency offset caused by the load can not be shifted by the action of the governor alone. The limitation is within the allowable range. At this time, the generator frequency modulation device of the FM power plant is also required to participate in the frequency adjustment; the third type of load fluctuation cycle frequency modulation mainly instructs each power plant to generate electricity according to a predetermined power generation load curve.

The principle of electric vehicles participating in frequency modulation is mainly to increase the load to reduce the load to achieve the target. According to the principle, the main participation is the primary frequency modulation of the power system. Therefore, according to the first type of load variation period, the detection period can be limited to 10s, for example, 7s.

The essence of power system frequency measurement is the dynamic parameter identification problem of signal observation model, which is to use the real system physical signal input, through a certain signal processing and numerical analysis process, to achieve a better estimation of the predetermined model parameters. The actual measuring devices vary in form, time and requirements. There are early analog, digital circuit modules and built-in program signal processing for single-chip microcomputers and industrial computers that are widely used today. Here mainly use the built-in program signal processing of the industrial computer, its main advantages: the chassis is made of steel structure, has high anti-magnetic, dustproof, anti-shock ability, special power supply inside the chassis, the power supply has strong anti-interference ability, continuous Long-term working ability, generally adopts a standard chassis that is easy to install.

The frequency variation of the power system has an impact on the user, the power plant and the power system itself, so it must be kept at or above the rated value of 50 Hz, and the offset does not exceed a certain range. China stipulates that for systems with a capacity above 3000MW, the frequency tolerance is 50±0.2Hz, the deviation of the electric clock indication from the standard time is not more than 30 seconds; for the system with the capacity below 3000MW, the frequency tolerance is 50±0.5Hz, the electric clock indicates Deviation from the standard time is no more than 1 minute.

The current charging power of the electric vehicle is P, and the charging device detects the local power grid. When the grid frequency is within the allowable range, the charging device continues to charge the electric vehicle with P. With the charging power of the charging device at the rated frequency, there is a “less charging” equivalent to “feeding to the grid”, and “multiple charging” is equivalent to “storage power generation in the storage grid”, with one-way charging. The way to achieve the same two-way V2G FM effect. When the system is in a low frequency state, the electric vehicle participates in low frequency regulation, reduces the charging power of the charging load, or disconnects it from the power grid; when the system is in a high frequency state, the electric vehicle exhibits a charging mode, increasing its Charging power to restore the frequency to normal. During the entire charging process, the charging power cannot exceed the power limit provided by the BMS and the maximum output power that the charging device can provide.

Figure 4 shows the schematic diagram of the electric car participating in the frequency modulation. The corresponding electric vehicle charging power calculation formula is:

During a certain period of time, if the grid frequency is stable, each electric vehicle is charged according to the power P, that is, the charging power of each electric vehicle is constant during this period. If the grid frequency fluctuates during this period and the fluctuation reaches the level that needs to be adjusted, then each charging device of the electric vehicle under the condition of frequency fluctuation starts to participate in the system frequency modulation. If the frequency rises, the charging power of the electric vehicle is increased accordingly to become P+ΔP; if the frequency is decreased, the charging power of the electric vehicle is correspondingly reduced to become P-ΔP. In this process, the electric vehicle charging power value P _{EV is} always positive. This means that while the response frequency changes, the electric vehicle is always in a state of charge. The electric vehicle battery does not need to be converted into a frequency modulation mode between the charging and discharging states, like the traditional vehicle to the grid (V2G, Vehicle-to-Grid). It meets the frequency modulation requirements, meets the user's charging requirements, and is beneficial to extend the service life of electric vehicle batteries.

In an optional embodiment of the present application, the method further includes: determining an initial response time; and adjusting the power output value according to the local grid frequency, including: according to the local grid frequency and the initial response time Adjust the power output value.

Figure 5 shows the initial response time distribution of the electric vehicle. In each detection cycle T, each device (ie, electric vehicle) monitors the local grid frequency. Different devices start to detect the frequency of the grid at different time points and execute control strategies. Because the initial time of the electric vehicle monitoring grid frequency is not set, but the detection period of each equipment is unified (that is, each electric vehicle sets the same detection period to monitor the local grid frequency), so the time point of the frequency deviation is found, that is, the initial The response time t _i is asynchronous. t _i is a random variable between [0, T], since the t _i of each device is independent of each other, and the chance of distribution at any one time point between [0, T] is equal, that is, appears in [ Any time between 0, T] is equally possible. According to the theory of probability theory and statistics, when the total number of electric vehicles participating in frequency modulation J is large enough, the t _i (i = 1, 2, ..., n) of these devices can be regarded as obeying the equilibrium distribution, and its probability mass function. Is 1/n. That is to say, at each cycle, when a frequency deviation event occurs, the initial response time t _{j of} each electric vehicle can be considered to be evenly distributed. In addition, since the time generated by the frequency deviation is also a random independent variable, the initial moment generated by it can also be considered to be evenly distributed within [0, T]. Therefore, the chances of each electric car participating in the response are equal in each cycle. Then there is the following formula:

In an optional embodiment of the present application, the adjustment of the power output value is responsive according to a local grid frequency deviation condition, and FIG. 6 shows a power response performance form diagram, where the adjustment range of the power output value satisfies the following expression:

Where L represents the number of response thresholds, ie the response level; α _l (l=1, 2, ..., L) is the power adjustment factor of the electric vehicle, indicating the power adjusted by the electric vehicle as a percentage of its available power, 0<α ₁ ≤α ₂ ≤...≤α _L <100%; δ _i (i=1,2,...,L) is the response threshold of response level i; P _i is the available power of electric vehicle i (including increased charging power or maximum power that can be reduced): 1) When Δf _t is positive, P _i is the maximum charging power that can be increased by electric vehicle i; 2) when Δf _t is negative, P _i is electric The maximum charging power that car i can reduce; sign is a symbolic function, and its representation is as follows:

among them,

Adjust the power for the total G2V of the electric car participating in the FM.

The embodiment of the present application adopts a step response manner, which has the advantages of simplicity, easy control, and implementation, and the user can flexibly set different response values according to different requirements of the user. In addition, the step response method used in this study, because the response amplitude is the same in a certain frequency deviation segment, it can appropriately relax the measurement accuracy of the frequency.

In an optional embodiment of the present application, the adjusted maximum value of the power output value is determined according to a maximum charging power that the electric vehicle can provide and a preset charging demand.

In this embodiment, the maximum adjustment value of the power output value (ie, the maximum charging power) is limited by the state of charge (SOC) of the electric vehicle and the maximum output capability of the electric vehicle, and the minimum charging power.

It is affected by the user's preset charging requirements, as shown below.

It can be determined by the following formula:

among them,

The maximum value of electric vehicles that can be increased in Δt time

then

Satisfy:

among them,

Calculated as follows:

The amount of electricity at the current moment.

The embodiment of the present application further provides a computer readable storage medium, where the computer program is stored, and when the computer program is executed by the processor, the steps of the method in the embodiment of the present application are implemented.

The foregoing is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application. It should be covered by the scope of protection of this application. Therefore, the scope of protection of the present application should be determined by the scope of the claims.

Claims

An electric vehicle charging control method, the method comprising:

Detecting the local grid frequency;

The power output value is adjusted according to the local grid frequency.
The method of claim 1 wherein said detecting a local grid frequency comprises:

The local grid frequency is detected according to a detection period; the detection period is determined according to a first type of load fluctuation period in the power system.
The method of claim 1 wherein said adjusting power output values based on said local grid frequency comprises:

The power output value is adjusted when the offset of the local grid frequency exceeds a preset threshold.
The method of claim 1 wherein the method further comprises:

Determine the initial response time;

The adjusting the power output value according to the local grid frequency includes:

The power output value is adjusted based on the local grid frequency and the initial response time.
The method of claim 4 wherein said initial response time is determined based on a detection period and a number of charging devices.
The method according to any one of claims 1 to 5, wherein the adjusted maximum value of the power output value is determined according to a maximum charging power and a preset charging demand that the electric vehicle can provide.
The method according to claim 6, wherein the adjusted maximum value of the power output value does not exceed the minimum charging power P i max ; the minimum charging power P i min reaches a minimum of the preset charging demand before charging is terminated. Charging demand

Where P i max =min(P i char,max , P i soc,max );

P i soc,max is determined by the following formula:

among them,

The maximum value of electric vehicles that can be increased in Δt time

Then P i min satisfies:

among them,
Calculated as follows:

Where: Q i is the battery capacity; η is the charging and discharging efficiency of the electric vehicle; T i is the leaving time of the i-th electric vehicle;
The difference between the minimum allowable power and the current power at time t+Δt;
It is the current amount of electricity; P i max is the maximum charging power that can be supplied.
The method according to claim 1, wherein the adjustment of the power output value is responsive according to a local grid frequency deviation condition, and the adjustment range of the power output value satisfies the following expression:

Where L represents the response level; α l (l = 1, 2, ..., L) is the power adjustment coefficient, 0 < α 1 ≤ α 2 ≤ ... ≤ α L <100%; δ i (i = 1,2,...,L) is the response threshold of response level i; P i is the available power of electric vehicle i, when Δf t is positive, P i is the maximum charging power that electric vehicle i can increase; when Δf When t is negative, P i is the maximum charging power that can be reduced by electric vehicle i; sign is a symbol function, and its representation is as follows:

Where ΔP i ev is the total G2V adjustment power of the electric vehicle participating in the frequency modulation.
A computer readable storage medium having stored thereon a computer program, the computer program being executed by a processor to perform the steps of the method of any one of claims 1 to 8.