CN112018751A - Hybrid energy storage system composite control method based on variable filtering time constant - Google Patents

Abstract

The invention discloses a composite control method for a hybrid energy storage system based on a variable filter time constant, comprising the following steps: (1) a monitoring and control system monitors the state of charge of each battery pack of an energy storage system through a data acquisition module, so as to obtain the overall (2) According to the state of charge of the energy storage system, a variable filter time constant control method is adopted, and a variable factor γ is introduced to adjust the filter time constant calculation period T _d of the battery energy storage system to obtain The filter time constant is corrected twice to control the output of the energy storage system. The invention can prevent the battery energy storage system from being overcharged and overdischarged, ensure its safe operation, and improve the battery life.

Description

Composite control method of hybrid energy storage system based on variable filter time constant

technical field

The invention relates to a control method for a hybrid energy storage system, in particular to a composite control method for a hybrid energy storage system based on a variable filtering time constant.

Background technique

In recent years, with the continuous deterioration of the energy crisis and environmental pollution, governments around the world have issued relevant policies to optimize the energy structure, which has promoted the research and utilization of new energy sources such as wind energy and solar energy. However, distributed power generation technologies such as photovoltaic power generation and wind power generation have fluctuations, which are greatly affected by the environment and seasonality. The power generation process is intermittent and uncontrollable. Incorporation into the power grid will affect the normal operation of the power grid. Due to its advantages, it is necessary to configure a reasonable energy storage to build a new energy power supply system, which promotes the local consumption of renewable energy, and has good development prospects and application value.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above problems, the present invention proposes a composite control method for a hybrid energy storage system based on a variable filter time constant, which can prevent the battery energy storage system from being overcharged and overdischarged, ensure its safe operation, and improve battery life.

Technical solution: The technical solution adopted in the present invention is a composite control method for a hybrid energy storage system based on a variable filter time constant, which is applied to a hybrid energy storage system including power-type energy storage and energy-type energy storage, including the following steps :

(1) The monitoring and control system monitors the state of charge of each battery in the energy-based energy storage system through the data acquisition module, so as to obtain the state of charge of the entire energy-based energy storage system;

(2) According to the state of charge of the energy-based energy storage system, the variable filter time constant control method is adopted, and a variable factor γ is introduced to adjust the filter time constant of the energy storage system, so as to perform a secondary correction on the filter time constant and control the energy storage system. The output of the energy system.

Wherein, the variable filter time constant control method includes the following processes:

(21) According to the state of charge of the energy storage system, select the following control conditions:

时，能量型储能系统仅放电；when

When the energy storage system only discharges;

时，能量型储能系统仅充电；when

When the energy-based energy storage system only charges;

时，对能量型储能系统以初始滤波时间常数进行定时间常数控制；when

When , the energy-based energy storage system is controlled by a fixed time constant with the initial filter time constant;

则判断能量型储能系统的输出功率P_bat是否大于0，若大于0，则T＝T+γΔT；若小于0，则T＝T-γΔT；当

则判断能量型储能系统的输出功率P_bat是否大于0，若大于0，则T＝T-γΔT；若小于0，则T＝T+γΔT；when

Then judge whether the output power P _bat of the energy-based energy storage system is greater than 0. If it is greater than 0, then T=T+γΔT; if it is less than 0, then T=T-γΔT; when

Then judge whether the output power P _bat of the energy storage system is greater than 0, if it is greater than 0, then T=T-γΔT; if it is less than 0, then T=T+γΔT;

和

分别为能量型储能系统正常工作时的荷电状态上下限值；

和

分别为能量型储能系统的最大限制充电与最小限制放电，T为滤波时间常数，γ为可变因子，ΔT为滤波时间常数修正量，ΔT＝CT_d，C为时间常数变化率，T_d为滤波时间常数计算周期。Among them, SOC _bat is the state of charge of the energy storage system,

and

are the upper and lower limits of the state of charge when the energy-based energy storage system is working normally;

and

are the maximum limit charge and minimum limit discharge of the energy-based energy storage system, T is the filter time constant, γ is the variable factor, ΔT is the filter time constant correction, ΔT=CT _d , C is the time constant change rate, T _d Calculate the period for the filter time constant.

The value of the variable factor γ is as follows:

时，调整系数γ＝1；when

When , the adjustment coefficient γ=1;

可变因子取值

when

Variable factor value

可变因子取值

when

Variable factor value

(22) Calculate the filtered reference value P _{fw_ref} (t) of the generated power of the power-type energy storage system at the current moment.

The calculation formula of the filtered reference value P _{fw_ref} (t) of the generated power of the power-type energy storage system at the current moment is:

Among them, t represents the time, and P _fw is the output power of the power-type energy storage system.

(23) Calculate the reference value P _{bat_ref} (t+1) of the generated power of the energy-based energy storage system at the next moment, and issue the control command to the energy-based energy storage system.

The calculation formula of the reference value P _{bat_ref} (t+1) of the generated power of the energy-based energy storage system at the next moment is:

P _{bat_ref} (t+1)=P _{fw_ref} (t)-P _fw (t)

Among them, t represents the time, and P _fw is the output power of the power-type energy storage system.

Beneficial effect: Compared with the existing technology, the hybrid energy storage combines power-type energy storage (flywheel) and energy-type energy storage (lithium battery) as a buffer link to stabilize the fluctuation of new energy, and combines the complementary characteristics of the two to ensure the power grid. power and energy requirements. The flywheel provides high-power instantaneous and frequent charging and discharging capabilities, but due to its low energy density, it is not suitable for storing a large amount of energy, so lithium batteries are required to meet the energy storage requirements. The mixed use of the two kinds of energy storage can not only smooth the fluctuation of the power supply of the new energy, but also improve the power quality of the new energy. Aiming at the power distribution problem of the hybrid energy storage system, the present invention combines the variable factor γ with the filter time constant calculation period T _d , and simultaneously considers the battery state of charge, and adjusts the output of the hybrid energy storage system in real time to prevent the battery energy storage system Overcharge and overdischarge to ensure safe operation and improve battery life. At the same time, the use of hybrid energy storage has improved the recycling rate of new energy.

Description of drawings

Figure 1 is a structural diagram of a hybrid energy storage system;

Figure 2 is a schematic diagram of the state of charge limit classification;

Fig. 3 is the variable filter time constant control block diagram of the present invention;

Fig. 4 is the filter time constant adjustment module structure diagram of the present invention;

FIG. 5 is a value rule diagram of the adjustment coefficient γ according to the present invention.

Detailed ways

The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

The composite control method of the hybrid energy storage system based on the variable filter time constant of the present invention is applied to the hybrid energy storage system as shown in FIG. 1 . The hybrid energy storage system includes power-type energy storage (flywheel) and energy-type energy storage (lithium battery) respectively connected to the traction grid, and the monitoring system is connected to the grid access side of the two. The present invention firstly monitors the load fluctuation of the traction network (that is, the change of the load fluctuation power ΔP) according to the monitoring system, and at the same time considers the advantages of the flywheel energy storage without considering the advantages of overcharge and overdischarge. The time constant T is combined to allocate power to the hybrid energy storage system, thereby compensating for the load fluctuation power ΔP. On this basis, a variable factor γ is introduced into the state of charge of the battery, and the filter time constant T is corrected twice to determine the output of the flywheel energy storage system and the battery energy storage system to prevent the battery energy storage system from being overcharged and overcharged. to ensure its safe operation. The invention introduces the variable factor γ into the filter time constant, and adjusts the output of the hybrid energy storage system in combination with the state of charge of the battery, so as to provide an effective reference for the energy management of the hybrid energy storage.

The composite control method of the hybrid energy storage system based on the variable filter time constant of the present invention comprises the following steps:

(1) The monitoring and control system monitors the state of charge (State Of Charge, SOC) of each lithium battery of the battery energy storage system through the data acquisition module, thereby obtaining the state of charge of the entire energy storage system.

(2) Considering the battery state of charge, the variable filter time constant is combined with the power distribution of the hybrid energy storage system, a variable factor γ is introduced, and the filter time constant T is corrected twice to ensure the battery life.

The structure of the hybrid energy storage system is shown in Figure 1. Among them, P _bat is the output power of the lithium battery; P _fw is the output power of the flywheel energy storage; P _{bat_ref} is the reference value of the output power of the lithium battery; ΔP is the output power of the busbar to the traction network. If it is negative, it means that the traction network supplies power to the energy storage element.

According to the energy conservation relationship:

P _bat +P _fw =ΔP (1)

The fluctuating P _fw is passed through a low-pass filter to obtain the power reference value P _{fw_ref} , P _{fw_ref} −P _fw =P _{bat_ref} . When P _{bat_ref} > 0, the battery is discharged; when P _{bat_ref} < 0, the battery is charged.

Among them, the low-pass filter function is:

和

分别为锂电池正常工作时的荷电状态上下限值；

和

分别为锂电池的最大限制充电与最小限制放电，当

时，锂电池只能充电，当

时，锂电池只能放电。The state of charge of the lithium battery is shown in Figure 2. in,

and

are the upper and lower limits of the state of charge when the lithium battery is working normally;

and

Respectively, the maximum limit charge and minimum limit discharge of the lithium battery, when

, the lithium battery can only be charged when

, the lithium battery can only discharge.

The control block diagram of the variable filter time constant is shown in Figure 3.

It can be obtained from the figure:

The s in the above formula is represented by d/dt, and the difference can be obtained:

P _{bat_ref} (t)=P _{fw_ref} (t)-P _fw (t) (6)

Among them, T _d is the calculation period.

The filter time constant adjustment method is shown in Figure 4. Among them, T(t) and T(t+1) are the filter time constants at time t and time t+1, respectively; _Tmax and _Tmin are the upper and lower limits of the filter time constant; C is the time constant change rate; ΔT is Correction of filter time constant, ΔT=CT _d .

The output control of this scheme is as follows:

时，锂电池只能放电。①When

, the lithium battery can only discharge.

时，锂电池只能充电。②When

, the lithium battery can only be charged.

时，电池以初始滤波时间常数进行定时间常数控制。③When

When , the battery performs constant time constant control with the initial filter time constant.

则判断P_bat是否大于0，若大于0，则T＝T+γΔT；若小于0，则T＝T-γΔT。当

则判断P_bat是否大于0，若大于0，则T＝T-γΔT；若小于0，则T＝T+γΔT。④When

Then judge whether P _bat is greater than 0. If it is greater than 0, then T=T+γΔT; if it is less than 0, then T=T-γΔT. when

Then judge whether P _bat is greater than 0. If it is greater than 0, then T=T-γΔT; if it is less than 0, then T=T+γΔT.

Among them, γ is the adjustment coefficient of the filter time constant calculation period T _d .

⑤ Calculate the filtered reference value P _{fw_ref} (t) of the power generated by the flywheel at the current moment by formula (5).

⑥ Calculate the reference value P _{bat_ref} (t+1) of the battery power generation power at the next moment by formula (6), and send the control command to the lithium battery energy storage system, and return to step ①.

Among them, in step 4, a variable factor γ is introduced to adjust the state of charge of the battery energy storage system, so as to perform a secondary correction on the filtering time constant, and then determine the output relationship between the flywheel energy storage and the battery system, and adjust the output of the hybrid energy storage system. Provide an effective reference for hybrid energy storage energy management.

The value of the variable factor γ is shown in Figure 5.

时，调整系数γ＝1，即此时误差较小，不需要进行引入调整系数。when

When , the adjustment coefficient γ=1, that is, the error is small at this time, and there is no need to introduce the adjustment coefficient.

此时该时间段内锂电池的调整系数只能取

When the SOC state is high

At this time, the adjustment factor of the lithium battery in this time period can only be taken as

此时该时间段内蓄电池的调整系数只能取

When the SOC state is low

At this time, the adjustment coefficient of the battery in this time period can only be taken as

Claims (5)

1. A hybrid energy storage system composite control method based on a variable filtering time constant is applied to a hybrid energy storage system comprising a power type energy storage system and an energy type energy storage system, and is characterized by comprising the following steps:

(1) the monitoring control system monitors the charge state of each battery in the energy type energy storage system through the data acquisition module so as to obtain the charge state of the whole energy type energy storage system;

(2) and according to the state of charge of the energy storage system, a variable filtering time constant control method is adopted, and a variable factor gamma is introduced to adjust the filtering time constant of the energy storage system so as to perform secondary correction on the filtering time constant and control the output of the energy storage system.

2. The hybrid energy storage system compound control method based on the variable filter time constant as claimed in claim 1, wherein the variable filter time constant control method comprises the following processes:

(21) selecting the following control conditions according to the state of charge of the energy storage system:

when in use

While, the energy-type energy storage system is only discharging;

when in use

When the energy storage system is charged, the energy storage system is only charged;

when in use

Then, performing timing constant control on the energy type energy storage system by using an initial filtering time constant;

when in use

Judging the output power P of the energy storage system_batIf the value is greater than 0, T + γ Δ T; if less than 0, T- γ Δ T; when in use

Judging the output power P of the energy storage system_batIf the value is greater than 0, then T-gamma delta T; if less than 0, T + γ Δ T;

therein, SOC_batIs the state of charge of the energy storage system,

and

respectively representing the upper limit value and the lower limit value of the state of charge of the energy type energy storage system during normal work;

and

the maximum limit charging and the minimum limit discharging of the energy storage system are respectively carried out, T is a filter time constant, gamma is a variable factor, delta T is a filter time constant correction quantity, and delta T is CT_dC is the rate of change of time constant, T_dThe period is calculated for the filter time constant.

(22) Calculating a reference value P of the filtered generated power of the power type energy storage system at the current moment_{fw_ref}(t)。

(23) Calculating a reference value P of the generated power of the energy storage system at the next moment_{bat_ref}(t +1) and sending the control command to the energy type energy storage system.

3. The hybrid energy storage system compound control method based on variable filtering time constant of claim 2, characterized in that the current time power type energy storage systemReference value Pf of filtered generated power_{w_ref}The formula for (t) is:

wherein t represents the time, P_fwIs the output power of the power type energy storage system.

4. The hybrid energy storage system compound control method based on the variable filtering time constant as claimed in claim 2, wherein the reference value P of the generated power of the energy storage system at the next moment_{bat_ref}The calculation formula of (t +1) is:

P_{bat_ref}(t+1)＝P_{fw_ref}(t)-P_fw(t)

wherein t represents the time, P_fwIs the output power of the power type energy storage system.

5. The hybrid energy storage system compound control method based on the variable filtering time constant of claim 2, wherein the variable factor γ takes the following values:

when in use

When the adjustment coefficient gamma is 1;

when in use

Value of variable factor

When in use

Value of variable factor

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