User side energy storage charging and discharging control method considering service life cost of energy storage battery

Abstract

Compared with a traditional simple control strategy of charging in a valley-time electricity price stage and charging in a peak-time electricity price stage, the core of the user-side energy storage charge and discharge control method considering the service life cost of the energy storage battery is to fully utilize the discharge depth space of the energy storage battery, and discharge arbitrage is carried out on excess electric quantity in an average-price electricity price order; compared with a traditional charging and discharging control strategy, the method has the advantages that the application range is wider, and the superiority and advancement of the control strategy can be better reflected when the monthly average load of the user side changes greatly and the capacity of the energy storage system is redundant.

Description

Technical Field

[0001] The present invention relates to a charging and discharging control strategy, and in particular to a user-side energy storage charging and discharging control method that takes into account the life cost of an energy storage battery. Background Art

[0002] At present, the domestic user-side energy storage charging and discharging control strategy is to continuously charge during the valley price period and continuously discharge during the peak electricity price stage, without considering the relationship with the user-side peak electricity price stage and the parity stage electricity consumption. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in view of the fact that the existing technology does not consider the relationship between the peak electricity price stage and the parity stage of the user side electricity consumption, a user side energy storage charging and discharging control method that takes into account the life cost of the energy storage battery is provided.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A user-side energy storage charging and discharging control method considering the life cost of energy storage batteries, wherein the cycle life of the battery is determined by the following power function:

[0006] N life =N 0 (DoD cyc ) -k

[0007] Where: N life N is the number of cycles when the battery reaches the end of its life; 0 is the number of cycles when the battery reaches the end of its life after charging and discharging at 100% discharge depth; DoDcyc is the actual cycle discharge depth of the battery; kp is the curve fitting parameter; N 0 and k are inherent constants of the battery when it leaves the factory;

[0008] Assuming the installed capacity of the energy storage system is S and the total investment cost of the energy storage system during its entire life cycle is C, the loss cost caused by a single charge and discharge is C / N life ; Discharge quantity S during peak electricity price period 1 , peak electricity price P 1 ; Discharge quantity S during the parity electricity price period 2 , the electricity price at parity P 2 ; Off-peak electricity price P 3 , then:

[0009] (1) When discharge occurs only during the peak phase:

[0010] S×DoD cyc1 =S 1

[0011] Nlife1 =N 0 (DoD cyc1 ) -k

[0012] Considering the loss of energy storage battery during each charge and discharge, the single charge and discharge profit W including the loss cost is 1 for:

[0013]

[0014] (2) Power consumption during peak hours S 1 <S×DoD cyc2 , the excess power in the energy storage battery W 2 Arbitrage can be performed during the parity period:

[0015] S×DoD cyc2 =S 1 +S 2

[0016]

[0017] To compare the benefits of the two discharge control strategies, set the objective function:

[0018]

[0019] Where N 0 , S, C, P 2 , P 3 , k are both constants;

[0020] make

[0021]

[0022] n=P 2 -P 3 ;

[0023] The formula can be resolved into:

[0024] W 1 -W 2 =m((S 1 +S 2 ) k -(S 1 ) k )-n×S 2

[0025] Set the objective function:

[0026] F(S 2 )=m((S 1 +S 2 ) k -(S1 ) k )-n×S 2

[0027] Then we have:

[0028] F'(S 2 )=mk(S 1 +S 2 ) k-1 -n

[0029] The extreme point of the objective function is:

[0030] F'(S 2 )=mk(S 1 +S 2 ) k-1 -n=0

[0031] mk(S 1 +S 2 ) k-1 =n

[0032]

[0033] when When F'(S 2 )<0; when When F'(S 2 )>0; F(S 2 )exist To obtain the minimum value, there are the following situations:

[0034] (1) When When , it means that W1-W2 is always ≥ 0, then the control strategy of discharging during the peak electricity price stage and not discharging during the parity period is adopted;

[0035] (2) When When Discharging during the parity period will achieve greater benefits, and the electricity load during the parity period is adjusted to It is more effective to adopt a control strategy of discharging during the parity period.

[0036] The present invention adopting the above technical solution aims to maximize the single charge and discharge benefits, establishes a relationship between the discharge depth of the energy storage battery and the life cost, and derives a formula to form a quantitative analysis of the results. The control strategy proposed by the present invention can effectively solve the problem of capacity waste caused by insufficient discharge depth of the energy storage battery in the traditional energy storage charge and discharge control strategy, and achieve the maximum single charge and discharge benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0038] like Figure 1 As shown, a user-side energy storage charging and discharging control method considering the life cost of energy storage batteries is as follows:

[0039] Energy storage operation has life loss, which is reflected in the number of charge and discharge cycles and is determined by the depth of discharge. The depth of discharge varies, and the number of cycles that can be performed on energy storage varies. Controlling the number of daily cycles can adjust the cycle life of energy storage. The rated cost of energy storage is amortized to the cycle life, which is the energy storage loss cost. Minimizing the daily loss cost can ensure the optimal cycle life of energy storage. Taking batteries as an example, their cycle life is determined by the following power function:

[0040] N life =N 0 (DoD cyc ) -k

[0041] Where: N life N is the number of cycles when the battery reaches the end of its life; 0 is the number of cycles when the battery reaches the end of its life after charging and discharging at 100% discharge depth; DoDcyc is the actual cycle discharge depth of the battery; kp is the curve fitting parameter; N 0 and k are inherent constants of the battery when it leaves the factory.

[0042] Assuming the installed capacity of the energy storage system is S and the total investment cost of the energy storage system during its entire life cycle is C, the loss cost caused by a single charge and discharge is C / N life ; Discharge quantity S during peak electricity price period 1 , peak electricity price P 1 ; Discharge quantity S during the parity electricity price period 2 , the electricity price at parity P 2 ; Off-peak electricity price P 3 , then:

[0043] (1) When the discharge is performed only during the peak period (ignoring the loss):

[0044] S×DoD cyc1 =S 1

[0045] N life1 =N 0 (DoD cyc1 ) -k

[0046] Considering the loss of energy storage battery during each charge and discharge, the single charge and discharge profit W including the loss cost is 1 for:

[0047]

[0048] (2) Power consumption during peak hours S 1 <S×DoD cyc2 , the excess power in the energy storage battery W 2 Arbitrage can be performed during the parity period:

[0049] S×DoD cyc2 =S 1 +S 2

[0050]

[0051] To compare the benefits of the two discharge control strategies, set the objective function:

[0052]

[0053] Where N 0 , S, C, P 2 , P 3 , k are both constants;

[0054] make

[0055]

[0056] n=P 2 -P 3 ;

[0057] The formula can be resolved into:

[0058] W 1 -W 2 =m((S 1 +S 2 ) k -(S 1 ) k )-n×S 2

[0059] Set the objective function:

[0060] F(S 2 )=m((S 1 +S 2 ) k -(S 1 ) k )-n×S 2

[0061] Then we have:

[0062] F'(S 2 )=mk(S 1 +S 2 ) k-1 -n

[0063] The extreme point of the objective function is:

[0064] F'(S 2 )=mk(S 1 +S 2 ) k-1 -n=0

[0065] mk(S 1 +S 2 ) k-1 =n

[0066]

[0067] when When F'(S 2 )<0; when When F'(S 2 )>0; F(S 2 )exist To obtain the minimum value, there are the following situations:

[0068] (1) When When , it means that W1-W2 is always ≥ 0. At this time, the energy storage control strategy adopts the control strategy of discharging during the peak electricity price stage and not discharging during the parity period.

[0069] (2) When When Discharging during the parity period will achieve greater benefits, and the electricity load during the parity period is adjusted to At this time, it is more effective to adopt a control strategy of discharging during the parity period.

[0070] Compared with traditional charging and discharging control strategies, this new charging and discharging control strategy has a wider range of applications. It can better demonstrate the superiority and advancement of this control strategy when there are large changes in the monthly average load on the user side and when the energy storage system has capacity redundancy, and has good prospects for promotion and application.

[0071] The proposed control strategy aims to maximize the single charge and discharge profit, takes into account the relationship between the discharge depth of the energy storage battery and the life of the energy storage battery, and has good social and economic benefits. At the same time, the proposed control strategy is simple in principle and easy to implement.

Claims

1. A user-side energy storage charging and discharging control method considering the life cost of energy storage batteries, characterized in that: The cycle life of a battery is determined by the following power function: N life =N0(DoD cyc ) -k Where: N life is the number of cycles when the battery reaches the end of its life; N0 is the number of cycles when the battery reaches the end of its life by charging and discharging at 100% discharge depth; DoDcyc is the actual cycle discharge depth of the battery; kp is the curve fitting parameter; N0 and k are both inherent constants of the battery when it leaves the factory; Assuming the installed capacity of the energy storage system is S and the total investment cost of the energy storage system during its entire life cycle is C, the loss cost caused by a single charge and discharge is C / N life ; The discharge quantity during the peak electricity price period is S1, and the peak electricity price is P1; the discharge quantity during the parity electricity price period is S2, and the parity electricity price is P2; the valley electricity price is P3, then: (1) When discharge occurs only during the peak phase: S×DoD cycl =S1 N lifel =N0(DoD cycl ) -k Considering the loss of energy storage battery each time of charging and discharging, the single charge and discharge profit W1 taking into account the loss cost is: (2) Power consumption during peak hours S1 <S×DoD cyc2 , the excess power W2 in the energy storage battery can be arbitraged during the parity period: <h2 style=";text-align:left;direction:ltr">S×DoD<h2 style=";text-align:left;direction:ltr"> cyc2 <h2 style=";text-align:left;direction:ltr"> (S1+S2) To compare the benefits of the two discharge control strategies, set the objective function: Where N0, S, C, P2, P3, and k are all constants; make n = P2-P3; The formula can be resolved into: W1-W2=m((S1+S2) k -(S1) k )-n×S2 Set the objective function: F(S2)=m((S1+S2) k -(S1) k )-n×S2 Then we have: <h2 style=";text-align:left;direction:ltr">F′(S2) = mk(S1+S2)<h2 style=";text-align:left;direction:ltr"> k-1 <h2 style=";text-align:left;direction:ltr"> -n The extreme point of the objective function is: <h2 style=";text-align:left;direction:ltr">F′(S2) = mk(S1+S2)<h2 style=";text-align:left;direction:ltr"> k-1 <h2 style=";text-align:left;direction:ltr"> -n=0 <h2 style=";text-align:left;direction:ltr">mk(S1+S2)<h2 style=";text-align:left;direction:ltr"> k-1 <h2 style=";text-align:left;direction:ltr"> =n when When F′(S2)<0; when When F′(S2)>0; F(S2) To obtain the minimum value, there are the following situations: (1) When When , it means that W1-W2 is always ≥ 0, then the control strategy of discharging during the peak electricity price stage and not discharging during the parity period is adopted; (2) When When Discharging during the parity period will achieve greater benefits, and the electricity load during the parity period is adjusted to It is more effective to adopt a control strategy of discharging during the parity period.

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