Self-adaptive power distribution control method and system of energy storage system considering SOC

Abstract

The invention discloses an energy storage system adaptive power distribution control method and system considering SOC, relates to the technical field of energy storage system power distribution control, and solves the problems of unreasonable power distribution and unbalanced charge state control between energy storage units in an existing direct current power supply system. Comprising the following steps: acquiring a charge-discharge state and a charge state of each energy storage unit in the energy storage system; calculating a first droop coefficient of each energy storage unit according to the charge-discharge state and the charge state of each energy storage unit; calculating a system charge mean value according to the charge states of all the energy storage units in the energy storage system, and calculating an equalization factor of each energy storage unit according to the charge-discharge state, the charge state and the system charge mean value of each energy storage unit; according to the first droop coefficient and the equalization factor of each energy storage unit, calculating a second droop coefficient of each energy storage unit, and guiding power distribution of each energy storage unit; through SOC and equalization factor optimization droop coefficient, reasonable power distribution and equalization control are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution control of energy storage systems, and more specifically, to an adaptive power distribution control method and system for energy storage systems taking SOC into consideration. Background Art

[0002] Common DC power supply systems include substation emergency DC power supply systems and DC microgrids. The former is mainly used to ensure power supply after power outages for important loads, while the latter is mainly used for power supply in islands and remote areas. Although the two are different in scale, they have similar structures and both include DC / DC converters, AC / DC converters, DC loads, AC loads, and energy storage systems. Among them, the role of the energy storage system is to maintain the power balance and DC voltage stability of the DC power supply system, as well as to improve the flexibility of system control and the economy of operation. Usually, the energy storage system is composed of multiple energy storage units running in parallel. Each unit is connected to the DC bus through a DC / DC converter. The key and technical difficulty of its control is how to distribute power among multiple energy storage units and achieve balanced control of the state of charge (SOC). Droop control has the advantages of no need for communication, multiple units jointly controlling DC voltage and power, and plug-and-play, and has been widely used in the power distribution of energy storage systems.

[0003] The coefficient of traditional droop control is a fixed coefficient. Usually, the droop coefficient is set only by considering the capacity of the energy storage unit. It cannot be adjusted dynamically according to the SOC, and it cannot achieve balanced control of the SOC. During the power distribution process, some energy storage units may be overcharged / discharged, and some energy storage units may have charge / discharge capacity, which affects the life of the energy storage unit. Some studies have proposed to consider the power distribution control of the energy storage unit SOC, but most of them are considered from the perspective of SOC balanced control, without considering the impact of the initial SOC of the energy storage unit on power distribution, resulting in unreasonable power distribution between energy storage units in the DC power supply system and unbalanced charge state control.

[0004] Therefore, the present application provides an adaptive power distribution control method and system for an energy storage system taking SOC into consideration to solve the above problems. Summary of the invention

[0005] The purpose of this application is to provide an adaptive power distribution control method and system for an energy storage system taking SOC into consideration, so as to solve the problems of unreasonable power distribution and unbalanced state of charge control between energy storage units in the existing DC power supply system; this application solves the above problems by dynamically optimizing the droop coefficient of the energy storage unit by introducing the state of charge SOC and the balancing factor.

[0006] The present application first provides an adaptive power distribution control method for an energy storage system considering SOC, including: obtaining the charge and discharge state and charge state of each energy storage unit in the energy storage system; calculating the first droop coefficient of each energy storage unit according to the charge and discharge state and charge state of each energy storage unit; calculating the system charge mean according to the charge state of all energy storage units in the energy storage system, and calculating the balance factor of each energy storage unit according to the charge and discharge state, charge state and system charge mean of each energy storage unit; calculating the second droop coefficient of each energy storage unit according to the first droop coefficient and the balance factor of each energy storage unit; and guiding the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit.

[0007] By adopting the above technical solution, the state of charge SOC and the balancing factor are introduced to dynamically adjust the droop coefficient of the energy storage unit, thereby optimizing the allocated charging and discharging power, realizing reasonable power allocation of the energy storage unit and rapid balanced control of the SOC; during discharge, the energy storage unit with a higher initial SOC is allocated a smaller droop coefficient to bear more discharge power, and during charging, the energy storage unit with a lower initial SOC is allocated a smaller droop coefficient to bear more charging power.

[0008] In a possible implementation, the first droop coefficient of each energy storage unit is calculated according to the charge and discharge state and the state of charge of each energy storage unit; and is obtained by the following function:

[0009]

[0010] Where: k′ i is the first droop coefficient of energy storage unit i during discharge, k″ i is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant.

[0011] In a possible implementation, the balancing factor of each energy storage unit is calculated according to the charge and discharge state, charge state and system charge mean of each energy storage unit; and is obtained by the following function:

[0012]

[0013] Where: i is the balancing factor of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

[0014] In a possible implementation, the second droop coefficient of each energy storage unit is calculated according to the first droop coefficient and the balancing factor of each energy storage unit; and is obtained by the following function:

[0015]

[0016] Where: k i is the second droop coefficient of energy storage unit i, δ i is the balancing factor of energy storage unit i during discharge, k′ i is the first droop coefficient of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, k″ i is the first droop coefficient of energy storage unit i during charging.

[0017] In a possible implementation, the power distribution of each energy storage unit is guided according to the second droop coefficient of each energy storage unit; the power distribution of each energy storage unit is guided by the following function:

[0018] V dcref,i =V dcN -k i P bess,i

[0019] Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k i is the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

[0020] The present application also provides an adaptive power distribution control system for an energy storage system taking SOC into consideration, comprising: a data acquisition unit, used to acquire the charge and discharge state and charge state of each energy storage unit in the energy storage system; a first droop coefficient calculation unit, used to calculate the first droop coefficient of each energy storage unit according to the charge and discharge state and charge state of each energy storage unit; a balancing factor calculation unit, used to calculate the system charge mean according to the charge state of all energy storage units in the energy storage system, and to calculate the balancing factor of each energy storage unit according to the charge and discharge state, charge state and system charge mean of each energy storage unit; a second droop coefficient calculation unit, used to calculate the second droop coefficient of each energy storage unit according to the first droop coefficient and the balancing factor of each energy storage unit; and a droop coefficient control unit, used to guide the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit.

[0021] In a possible implementation manner, the first droop coefficient calculation unit is specifically configured to calculate the first droop coefficient of each energy storage unit by using the following function:

[0022]

[0023] Where: k′ i is the first droop coefficient of energy storage unit i during discharge, k″ i is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant.

[0024] In a possible implementation manner, the balancing factor calculation unit is specifically configured to obtain the balancing factor of each energy storage unit through the following function:

[0025]

[0026] Where: i is the balancing factor of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

[0027] In a possible implementation manner, the second droop coefficient calculation unit is specifically configured to obtain the second droop coefficient of each energy storage unit through the following function:

[0028]

[0029] Where: k i is the second droop coefficient of energy storage unit i, δ i is the balancing factor of energy storage unit i during discharge, k′ i is the first droop coefficient of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, k″ i is the first droop coefficient of energy storage unit i during charging.

[0030] In a possible implementation manner, the droop coefficient control unit is specifically configured to guide the power distribution of each energy storage unit through the following function:

[0031] V dcref,i =V dcN -k i P bess,i

[0032] Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k iis the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

[0033] Compared with the prior art, the present application has the following beneficial effects: by introducing the SOC of the energy storage unit and the balancing factor to optimize the droop coefficient, adaptive power distribution is achieved; the SOC of the energy storage unit is fully considered, so that the energy storage unit with a larger initial SOC can bear more discharge power during discharge, and the energy storage unit with a smaller initial SOC can bear more charging power during charging, and the droop coefficient of the energy storage unit and the allocated charging and discharging power are dynamically adjusted according to the SOC value during the charging and discharging process, so as to achieve reasonable power distribution of each energy storage unit and rapid SOC balancing control, which can effectively avoid excessive discharge or charging of the energy storage unit due to SOC imbalance, extend the life of the energy storage unit, and the overall control effect is better than the traditional droop control power distribution method. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0035] Figure 1 This is a structural diagram of a typical DC power supply system including an energy storage system;

[0036] Figure 2 A flow chart of an adaptive power allocation control method for an energy storage system considering SOC;

[0037] Figure 3 It is the energy storage unit partition diagram considering SOC;

[0038] Figure 4 is the characteristic curve of the first droop coefficient changing with SOC during discharge;

[0039] Figure 5 is a characteristic curve of the first droop coefficient changing with SOC during charging;

[0040] Figure 6 It is the characteristic diagram of the balance factor during discharge;

[0041] Figure 7 This is the characteristic diagram of the balancing factor during charging;

[0042] Figure 8 is a power distribution characteristic diagram controlled by the second droop coefficient;

[0043] Fig. 9 The block diagram of the adaptive power distribution control system for the energy storage system considering SOC;

[0044] Fig.10 It is the response diagram of the system under discharge condition;

[0045] Fig.11 This is the response diagram of the system under charging conditions. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0047] First, the application scenarios of this application are described. Figure 1 As shown, Figure 1 The structure diagram of a typical DC power supply system with an energy storage system. It includes m energy storage units, n DC loads, p AC loads, DC\DC converters, AC\DC converters, and is usually connected to an external AC power grid. The battery of the energy storage unit is connected to the DC power supply system through a bidirectional DC\DC converter, the main purpose of which is to maintain the stability of the DC voltage and the balance of power; the DC load is connected to the DC power supply system through a Buck step-down converter; the AC load is connected to the DC power supply system through an AC / DC converter. When the AC system is powered off, the AC\DC converter works in the inverter mode to supply energy to the AC load. When the AC system is operating normally, the AC\DC converter works in the rectification mode to supply energy to the DC load and battery charging.

[0048] In the above application scenarios, when the DC system has power imbalance, the energy storage system needs to quickly balance the unbalanced power of the DC system to maintain the stability of the DC voltage. The difficulty lies in how to distribute the unbalanced power among the various energy storage units.

[0049] To this end, the present application provides an energy storage system adaptive power allocation control method and system considering SOC to solve the above problems. The method and system provided by the present application are described in detail below in conjunction with specific embodiments.

[0050] See also Figure 2 As shown, Figure 2 The present invention is a flow chart of an adaptive power distribution control method for an energy storage system considering SOC. The method comprises: S1, obtaining the charge-discharge state and charge state of each energy storage unit in the energy storage system; S2, calculating the first droop coefficient of each energy storage unit according to the charge-discharge state and charge state of each energy storage unit; S3, calculating the system charge mean according to the charge state of all energy storage units in the energy storage system, and calculating the balance factor of each energy storage unit according to the charge-discharge state, charge state and system charge mean of each energy storage unit; S4, calculating the second droop coefficient of each energy storage unit according to the first droop coefficient and balance factor of each energy storage unit; S5, guiding the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit.

[0051] The improvement of this solution is that the state of charge SOC and the balancing factor are introduced to dynamically adjust the droop coefficient of the energy storage unit, thereby optimizing its allocated charging and discharging power, and realizing reasonable power allocation of the energy storage unit and rapid balancing control of SOC. By implementing this solution, during discharge, the energy storage unit with a higher initial SOC is allocated a smaller droop coefficient to bear more discharge power, and during charging, the energy storage unit with a lower initial SOC is allocated a smaller droop coefficient to bear more charging power.

[0052] Step S1 is to obtain the charge / discharge state and charge state of each energy storage unit in the energy storage system. By analyzing the charge / discharge state and charge state of the energy storage unit, corresponding restrictions can be set to avoid overcharging or discharging of the energy storage unit and affecting its life.

[0053] Specifically, assuming that the SOC of the energy storage unit at the initial time t0 is SOC0, when the energy storage unit is charged and discharged, the SOC at any time t can be calculated as:

[0054]

[0055] Where: SOC0 is the SOC value of the energy storage unit at the initial time t0, Q is the maximum capacity of the energy storage unit that can store charge, P bess The power used to charge / discharge the energy storage unit. When charging, P bess <0; when discharging, P bess >0.

[0056] The SOC value of the energy storage unit at any time is calculated according to formula (1). Then, the suitable working area of ​​the energy storage unit is analyzed based on the SOC value. The working area of ​​the energy storage unit includes: prohibited discharge area, restricted discharge area, free charge and discharge area, restricted charge area and prohibited charge area. Please refer to Figure 3As shown. Among them, 1. The prohibited discharge area refers to the SOC between 0% and SOC1. At this time, the energy storage unit is not allowed to discharge to avoid excessive discharge of the energy storage unit and affect its life. 2. The restricted discharge area refers to the SOC between SOC1 and SOC2. In this area, as the SOC value decreases, the discharge of the energy storage unit should be gradually restricted to reduce the output of the energy storage unit to avoid directly stopping the discharge when the SOC reaches SOC1, which will bring greater power disturbances to the system. 3. The normal charging and discharging area refers to the SOC between SOC2 and SOC3. At this time, the charging and discharging of the energy storage unit is not restricted, and the energy storage unit is charged and discharged according to the needs of the energy storage system. 4. The restricted charging area refers to the SOC between SOC3 and SOC4. In this area, as the SOC value increases, the charging of the energy storage unit should be gradually restricted to reduce the charging power of the energy storage unit to avoid directly stopping the charging when the SOC reaches SOC4, which will bring greater power disturbances to the system. 5. The prohibited charging area refers to the SOC between SOC4 and 100%. At this time, the energy storage unit is not allowed to be charged to avoid overcharging of the energy storage unit and affecting its life.

[0057] Step S2 is to calculate the first droop coefficient of each energy storage unit according to the charge and discharge state and charge state of each energy storage unit. Figure 3 The energy storage unit partition is based on the adjusted droop control coefficient of the SOC value of the energy storage unit to obtain the first droop coefficient of the energy storage system. The first droop coefficient takes into account the SOC value of the energy storage unit, which can effectively prevent the energy storage unit from being overcharged and discharged and affecting its life.

[0058] Specifically, see Figure 4-5 As shown. According to the charge and discharge status of each energy storage unit, different piecewise functions are set to adjust the droop control coefficient. When discharging, the energy storage unit with a higher initial SOC is assigned a smaller droop coefficient to bear more discharge power, and when charging, the energy storage unit with a lower initial SOC is assigned a smaller droop coefficient to bear more charging power.

[0059] like Figure 4 As shown, the first droop coefficient of the energy storage unit during discharge is obtained by the following piecewise function:

[0060]

[0061] Where: k′ i is the first droop coefficient of energy storage unit i during discharge, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant. It can be seen that when SOC iWhen SOC is greater than SOC2, the first droop coefficient at this time is equal to the initial value k0, indicating that the discharge power of the energy storage unit is not limited, and the energy storage unit distributes power according to the first droop coefficient k0; when the energy storage unit discharges into the restricted discharge area, that is, SOC i Between SOC1 and SOC2, the droop coefficient increases with SOC i The power allocated to the corresponding energy storage unit gradually decreases until the energy storage unit enters the prohibited discharge area (SOC1), and the droop coefficient is equal to the maximum value k max , at which point the energy storage unit stops discharging.

[0062] like Figure 5 As shown, the first droop coefficient of the energy storage unit during charging is obtained by the following piecewise function:

[0063]

[0064] Where: k″ i is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant. It can be seen that the characteristics during charging and discharging are similar. i When SOC is less than 3, the droop coefficient k i is equal to the initial value k0, indicating that the charging power of the energy storage unit is not limited, and the energy storage unit allocates power according to the first droop coefficient k0; when the energy storage unit enters the restricted charging area, that is, SOC i Between SOC3 and SOC4, the droop coefficient k i With SOC i The charging power allocated to the unit gradually decreases, and the charging speed of the energy storage unit gradually slows down until the energy storage unit enters the prohibited charging area (SOC4), and the droop coefficient is equal to the maximum value k max , at this time the energy storage unit stops charging.

[0065] Step S3 is to calculate the system charge mean value according to the charge state of all energy storage units in the energy storage system, and calculate the balance factor of each energy storage unit according to the charge and discharge state, charge state and system charge mean value of each energy storage unit. The first droop coefficient obtained based on step S2 only considers the SOC of the energy storage unit itself, and does not consider the SOC of the remaining energy storage units. Under certain operating conditions, the SOC balance of each energy storage unit cannot be achieved. Therefore, the balance factor is calculated by the charge and discharge state, charge state and system charge mean value of each energy storage unit, which is used to optimize the first droop coefficient and achieve balanced control of the SOC of each energy storage unit.

[0066] Specifically, see Figure 6-7As shown. According to the charge and discharge state, charge state and system charge mean of each energy storage unit, the balancing factor is calculated to adjust the droop control coefficient. This makes the SOC value of each energy storage unit gradually balanced after charging and discharging.

[0067] like Figure 6 As shown, the balancing factor of the energy storage unit during discharge is obtained by the following function:

[0068]

[0069] Where: i is the balancing factor of energy storage unit i during discharge, ΔSOC i is the state of charge SOC of energy storage unit i i And the system charge mean SOC avr The difference is, a is the difference adjustment coefficient of the balancing factor, b is the power exponential adjustment coefficient of the balancing factor, and m is the total number of energy storage units.

[0070] like Figure 7 As shown, the balancing factor of the energy storage unit during charging is obtained by the following function:

[0071]

[0072] Where: γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

[0073] Step S4 is to calculate the second droop coefficient of each energy storage unit according to the first droop coefficient and the balancing factor of each energy storage unit. The first droop coefficient of step S2 is optimized based on the balancing factor of step S3 to obtain the second droop coefficient. The second droop coefficient takes into account both the impact of the SOC value on the life of the energy storage unit and the balance of the SOC values ​​of each energy storage unit in the system, so as to achieve safe and balanced charging and discharging of the energy storage units in the system.

[0074] Specifically, the second droop coefficient of each energy storage unit during discharge is obtained by the following function:

[0075] k i =δ i k′ i (7)

[0076] Where: k i is the second droop coefficient of energy storage unit i, δ i is the balancing factor of energy storage unit i during discharge, k′ i is the first droop coefficient of energy storage unit i during discharge. Figure 6The discharge balance factor characteristic diagram, when ΔSOC i When it is less than 0, it means that the SOC of the i-th energy storage unit i Less than the system charge mean SOC avr , at this time the equilibrium factor δ i Greater than 1, k i >k′ i , equalization factor δ i The first droop coefficient k′ of the energy storage unit is increased i , its allocated power decreases, that is, when the SOC of the energy storage unit i Less than the system charge mean SOC avr When the SOC of the energy storage unit is i Greater than the average SOC of each unit avr When the equalization factor δ i Less than 1, k i <k′ i , equalization factor δ i The first droop coefficient k′ of the energy storage unit is reduced i , the allocated discharge power increases, and the SOC decreases faster. Therefore, in the balancing factor δ i Under the action of, the SOC of each energy storage unit will tend to be balanced.

[0077] The second droop coefficient of each energy storage unit during charging is obtained by the following function:

[0078] k i =γ i ·k″ i (8)

[0079] Where: k i is the second droop coefficient of energy storage unit i, γ i is the balancing factor of energy storage unit i during charging, k″ i is the first droop coefficient of energy storage unit i during charging. Figure 7 The charging balance factor characteristic diagram, when the SOC of the energy storage unit i When it is smaller (less than the system charge mean SOC avr ), γ i <1, k i <k″ i , the equalization factor γ i The first droop coefficient k" of the energy storage unit is reduced i , the allocated charging power increases, and the SOC rises faster; when the SOC of the energy storage unit i When it is larger (greater than the system charge mean SOC avr ), γ i >1, ki >k″ i , the equalization factor γ i Increase the first droop coefficient k" of the energy storage unit i , the allocated charging power is reduced and the SOC rise speed is slowed down. Therefore, in the balancing factor γ i Under the action of, the SOC of each energy storage unit will tend to be balanced.

[0080] Step S5 is to guide the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit. The droop control is introduced in the power control link of each energy storage unit. Its essence is that a single energy storage unit adjusts its active output or input according to the measured DC voltage, and multiple energy storage units jointly control the DC voltage and maintain the power balance of the DC power supply system. The DC voltage of the bidirectional DC\DC converter of the energy storage unit i is guided by the second droop control coefficient of step S4.

[0081] Specifically, see Figure 8 The second droop coefficient guides the power distribution of each energy storage unit through the following function:

[0082] V dcref,i =V dcN -k i P bess,i (9)

[0083] Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k i is the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

[0084] Combination Figure 8 The power distribution characteristic diagram of the second droop coefficient control. In steady-state operation, for energy storage unit i, the DC voltage V dcN Able to track its reference value V dcref,i . Figure 8 The left half (negative semi-axis) indicates that the energy storage unit is operating in a charging state, and the corresponding power is a negative value. The negative sign of the power indicates that the power flows into the energy storage unit. The smaller the power value corresponding to the negative semi-axis, the greater the charging power corresponding to the energy storage unit during charging. Figure 8 The right half (positive semi-axis) indicates that the energy storage unit is operating in the discharge state, and the corresponding power is a positive value. The positive sign of the power indicates that the power flows out of the energy storage unit. The larger the power value corresponding to the positive semi-axis, the greater the discharge power corresponding to the energy storage unit during discharge.

[0085] by Figure 8 As an example, the three curves of VdcN ), the slopes of the three curves are k1<k2<k3. Ignoring the voltage drop of the DC line, the DC voltage corresponding to each energy storage unit is equal. When the energy storage unit is discharged, the DC voltage is V dc1 (less than V dcN ), Figure 8 The relationship between the discharge powers corresponding to different second droop coefficients is P1>P2>P3>0, that is, the smaller the second droop coefficient, the greater the power allocated when the energy storage unit is discharged. When the energy storage unit is charged, the DC voltage is V dc2 (greater than V dcN ), Figure 8 The magnitude relationship of the charging power corresponding to different second droop coefficients is P1<P2<P3<0, that is, the smaller the second droop coefficient, the greater the power allocated to the energy storage unit when charging. It can be seen that when distributing power, the smaller the second droop coefficient, the more power allocated to the energy storage unit.

[0086] It is understandable that, in response to the problems of unreasonable power distribution and unbalanced SOC control between energy storage units in a DC power supply system, the present application proposes an adaptive power distribution control method for an energy storage system that takes SOC into consideration, specifically, the SOC and balancing factor of the energy storage unit are introduced to optimize the droop coefficient to achieve adaptive power distribution. The adaptive power distribution control method provided by the present application fully considers the SOC of the energy storage unit, and can allow energy storage units with a larger initial SOC to bear more discharge power during discharge, and energy storage units with a smaller initial SOC to bear more charging power during charging, and dynamically adjust the droop coefficient of the energy storage unit and the allocated charge and discharge power according to the SOC value during the charging and discharging process, so as to achieve reasonable power distribution of each energy storage unit and rapid balanced control of SOC, which can effectively avoid excessive discharge or charging of energy storage units caused by unbalanced SOC, extend the life of energy storage units, and the overall control effect is better than the traditional droop control power distribution method.

[0087] See also Fig. 9 As shown, Fig. 9The structure diagram of the adaptive power distribution control system for energy storage system considering SOC. The system includes: a data acquisition unit, used to acquire the charge and discharge state and charge state of each energy storage unit in the energy storage system; a first droop coefficient calculation unit, used to calculate the first droop coefficient of each energy storage unit according to the charge and discharge state and charge state of each energy storage unit; a balancing factor calculation unit, used to calculate the system charge mean according to the charge state of all energy storage units in the energy storage system, and calculate the balancing factor of each energy storage unit according to the charge and discharge state, charge state and system charge mean of each energy storage unit; a second droop coefficient calculation unit, used to calculate the second droop coefficient of each energy storage unit according to the first droop coefficient and balancing factor of each energy storage unit; a droop coefficient control unit, used to guide the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit.

[0088] In a possible implementation manner, the first droop coefficient calculation unit is specifically configured to calculate the first droop coefficient of each energy storage unit by using the following function:

[0089]

[0090] Where: k′ i is the first droop coefficient of energy storage unit i during discharge, k″ i is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant.

[0091] In a possible implementation manner, the balancing factor calculation unit is specifically configured to obtain the balancing factor of each energy storage unit through the following function:

[0092]

[0093] Where: i is the balancing factor of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

[0094] In a possible implementation manner, the second droop coefficient calculation unit is specifically configured to obtain the second droop coefficient of each energy storage unit through the following function:

[0095]

[0096] Where: k i is the second droop coefficient of energy storage unit i, δi is the balancing factor of energy storage unit i during discharge, k′ i is the first droop coefficient of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, k″ i is the first droop coefficient of energy storage unit i during charging.

[0097] In a possible implementation manner, the droop coefficient control unit is specifically configured to guide the power distribution of each energy storage unit through the following function:

[0098] V dcref,i =V dcN -k i P bess,i

[0099] Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k i is the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

[0100] It should be noted that the adaptive power distribution control system of the energy storage system considering SOC is used to implement the above-mentioned adaptive power distribution control method of the energy storage system considering SOC, corresponds one-to-one with the above-mentioned method, and has corresponding effects, so it will not be elaborated on.

[0101] See also Figure 10-11 The present application also provides a specific verification example to illustrate the effect of the energy storage system adaptive power distribution control method and system considering SOC provided by the present application.

[0102] In order to verify the accuracy of the proposed control strategy, a Figure 1 The simulation system shown in the figure includes 3 energy storage units, 2 DC loads, 2 AC loads and 1 AC\DC converter. The SOC of the three energy storage units are 60%, 50% and 40% respectively. The parameters of the adaptive droop control proposed in the present invention are: SOC1=10%, SOC2=45%, SOC3=55%, SOC4=90%, k0=0.02, k max =0.2, a=2, b=5.

[0103] Fig.10It is a system response diagram under the discharge condition of the energy storage system. The curves corresponding to Bess1, Bess2, and Bess3 are the response curves of energy storage unit 1, energy storage unit 2, and energy storage unit 3 under the adaptive power allocation control provided in this application. The curves corresponding to Bess1', Bess2', and Bess3' are the response curves of energy storage unit 1, energy storage unit 2, and energy storage unit 3 under the traditional fixed droop coefficient control.

[0104] Depend on Fig.10 It can be seen that under the control of a fixed droop coefficient, the SOC of the energy storage unit is not taken into consideration, the discharge power allocated to each energy storage unit is the same, and the rate of decrease of the SOC is the same, and the balanced distribution of the SOC between the energy storage units cannot be achieved. At 110s, the SOC of Bess1 is about 10%, while the SOC of Bess3 is greater than 30%, which may cause the energy storage unit with a smaller initial SOC to over-discharge and affect the life of the energy storage unit. However, under the adaptive power distribution control provided in the present application, at the initial moment, the energy storage unit with a larger SOC has a small droop coefficient, and its allocated discharge power is large, and its allocated discharge power is small. During the discharge process, the droop coefficient and the allocated discharge power are dynamically adjusted, and the SOC of each energy storage unit gradually tends to be balanced. At 110s, the SOCs of the three energy storage units are all around 20%. As the SOC of each energy storage unit tends to be balanced, the droop coefficients of each energy storage unit gradually approach each other, and the allocated discharge powers gradually become consistent, indicating that the adaptive power allocation control provided in the present application can achieve reasonable power allocation of each energy storage unit and balanced control of SOC.

[0105] Fig.11 It is a system response diagram under the charging condition of the energy storage unit. The curves corresponding to Bess1, Bess2, and Bess3 are the response curves of energy storage unit 1, energy storage unit 2, and energy storage unit 3 under the adaptive power distribution control provided in this application. The curves corresponding to Bess1', Bess2', and Bess3' are the response curves of energy storage unit 1, energy storage unit 2, and energy storage unit 3 under the traditional fixed droop coefficient control.

[0106] Depend on Fig.11It can be seen that, similar to the discharge condition, under the control of the fixed droop coefficient, the discharge power allocated to each energy storage unit is the same, the SOC decrease rate is the same, and the balanced control of SOC cannot be achieved, which may cause the energy storage unit with a higher initial SOC to be overcharged, affecting the life of the energy storage unit. Under the adaptive power allocation control provided by the present application, at the initial moment, the droop coefficient of the energy storage unit with a larger SOC is large, and the charging power allocated to it is small, and the droop coefficient of the energy storage unit with a smaller SOC is small, and the charging power allocated to it is large. In the charging process, the droop coefficient and the allocated charging power are dynamically adjusted, and the SOC of each energy storage unit gradually tends to be balanced, the droop coefficient of each energy storage unit gradually approaches, and the allocated charging power gradually becomes consistent, so that the SOC balanced control of each energy storage unit can be achieved.

[0107] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An adaptive power distribution control method for an energy storage system considering SOC, characterized in that: include: Obtain the charge and discharge status and charge state of each energy storage unit in the energy storage system; Calculating a first droop coefficient of each energy storage unit according to the charge and discharge state and the state of charge of each energy storage unit; The system charge mean is calculated according to the charge state of all energy storage units in the energy storage system, and the balancing factor of each energy storage unit is calculated according to the charge and discharge state, charge state and system charge mean of each energy storage unit; Calculating a second droop coefficient of each energy storage unit according to the first droop coefficient and the balancing factor of each energy storage unit; According to the second droop coefficient of each energy storage unit, the power distribution of each energy storage unit is guided.

2. The adaptive power distribution control method of energy storage system considering SOC according to claim 1 is characterized in that: According to the charge and discharge state and charge state of each energy storage unit, the first droop coefficient of each energy storage unit is calculated; it is obtained by the following function: Where: k i ' is the first droop coefficient of energy storage unit i during discharge, k i ″ is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant.

3. The adaptive power distribution control method of energy storage system considering SOC according to claim 1, characterized in that: According to the charge and discharge state, charge state and system charge mean of each energy storage unit, the balance factor of each energy storage unit is calculated; it is obtained through the following function: Where: i is the balancing factor of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

4. The adaptive power distribution control method of energy storage system considering SOC according to claim 1 is characterized in that: According to the first droop coefficient and the balancing factor of each energy storage unit, the second droop coefficient of each energy storage unit is calculated; it is obtained by the following function: Where: k i is the second droop coefficient of energy storage unit i, δ i is the balancing factor of energy storage unit i during discharge, k i ′ is the first droop coefficient of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, k i ″ is the first droop coefficient of energy storage unit i during charging.

5. The adaptive power distribution control method of energy storage system considering SOC according to claim 1, characterized in that: According to the second droop coefficient of each energy storage unit, the power distribution of each energy storage unit is guided; the power distribution of each energy storage unit is guided by the following function: V dcref,i =V dcN -k i P bess,i Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k i is the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

6. An adaptive power distribution control system for an energy storage system considering SOC, characterized in that: include: A data acquisition unit, used to acquire the charge and discharge status and charge state of each energy storage unit in the energy storage system; A first droop coefficient calculation unit, used to calculate a first droop coefficient of each energy storage unit according to a charge / discharge state and a charge state of each energy storage unit; A balancing factor calculation unit, used to calculate the system charge mean according to the charge states of all energy storage units in the energy storage system, and to calculate the balancing factor of each energy storage unit according to the charge and discharge state, charge state and system charge mean of each energy storage unit; A second droop coefficient calculation unit, used for calculating a second droop coefficient of each energy storage unit according to the first droop coefficient and the balancing factor of each energy storage unit; The droop coefficient control unit is used to guide the power distribution of each energy storage unit according to the second droop coefficient of each energy storage unit.

7. The energy storage system adaptive power distribution control system considering SOC according to claim 6, characterized in that: The first droop coefficient calculation unit is specifically used to calculate the first droop coefficient of each energy storage unit through the following function: Where: k i ' is the first droop coefficient of energy storage unit i during discharge, k i ″ is the first droop coefficient of energy storage unit i during charging, SOC i is the state of charge of energy storage unit i, SOC1, SOC2, SOC3, SOC4 are partition values, k max , k0 is a constant.

8. The energy storage system adaptive power distribution control system considering SOC according to claim 6, characterized in that: The balancing factor calculation unit is specifically used to obtain the balancing factor of each energy storage unit through the following function: Where: i is the balancing factor of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, ΔSOC i is the difference between the state of charge of energy storage unit i and the system charge mean, a is the difference adjustment coefficient of the balancing factor, and b is the power exponential adjustment coefficient of the balancing factor.

9. The energy storage system adaptive power distribution control system considering SOC according to claim 6, characterized in that: The second droop coefficient calculation unit is specifically used to obtain the second droop coefficient of each energy storage unit through the following function: Where: k i is the second droop coefficient of energy storage unit i, δ i is the balancing factor of energy storage unit i during discharge, k i ′ is the first droop coefficient of energy storage unit i during discharge, γ i is the balancing factor of energy storage unit i during charging, k i ″ is the first droop coefficient of energy storage unit i during charging.

10. The energy storage system adaptive power distribution control system considering SOC according to claim 6, characterized in that: The droop coefficient control unit is specifically used to guide the power distribution of each energy storage unit through the following function: V dcref,i =V dcN -k i P bess,i Where: V dcref,i is the DC voltage reference value of energy storage unit i, V dcN is the rated DC voltage of the energy storage system, k i is the second droop coefficient of energy storage unit i, P bess,i is the power of energy storage unit i.

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