Multi-scenario collaborative control method for distributed energy storage system based on fault location and dynamic communication repair

Abstract

The application discloses a distributed energy storage system multi-scene cooperative control method based on fault positioning and dynamic communication repair, mainly including a fault positioning module, a communication repair module, a communication module, an SOC balancing module, a current equalization control module, a voltage recovery module and a voltage and current double closed loop module. The fault positioning module is used for accurately identifying and positioning a fault energy storage unit; the communication repair module is used for realizing adaptive matching of a communication network and a system control topology; the communication module is used for enabling adjacent energy storage units to exchange information, so that the average value of system SOC and control state quantity can be obtained; the SOC balancing module, the current equalization control module and the voltage recovery module are used for realizing SOC balancing of each unit, proportionally distributing output currents according to capacity, and maintaining bus voltage at a rated value, so that the distributed energy storage system can be stably, efficiently and cooperatively operated in multiple scenes such as system starting, steady operation and fault repair.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct-current micro-grid distributed energy storage systems, in particular to a multi-scenario collaborative control method for distributed energy storage systems based on fault positioning and dynamic communication repair. BACKGROUND

[0002] With the rapid development of new energy industry, distributed energy storage systems, as the key support for stabilizing new energy output fluctuation and improving energy utilization efficiency, are widely used in micro-grid, smart building and other scenarios. However, the distributed energy storage system is composed of multiple energy storage units operating collaboratively, and faces many technical challenges in actual operation: on the one hand, the energy storage unit may fail due to battery aging, power device damage and other reasons, and the traditional control method is difficult to quickly and accurately identify and locate the faulty unit, which may lead to the expansion of the fault range and affect the overall operation stability of the system; on the other hand, the system relies on communication network to realize the collaborative control among units, when some units fail to exit, the original communication topology will be broken, if the communication link cannot be reconstructed and adapted to the current running state in time, the data interaction will be interrupted, and the control strategy will fail. Therefore, the present application designs a multi-scenario collaborative control method for distributed energy storage systems based on fault positioning and dynamic communication repair, which realizes accurate identification of abnormal or faulty units by constructing a fault positioning module, and completes dynamic reconstruction and adaptation of the communication topology by combining a communication repair module, on this basis, integrates the functions of state-of-charge (SOC) balancing, current sharing and voltage recovery control, realizes the SOC balancing of each energy storage unit and the proportional distribution of output current according to the capacity of the energy storage unit without relying on output current sampling, and maintains the bus voltage to the rated value, effectively solving the limitations of traditional control methods in fault response, communication adaptation and balancing control, and realizing stable, efficient and collaborative operation of the system in multiple complex scenarios. SUMMARY

[0003] To achieve the above-mentioned purpose, the technical scheme provided by the present application is as follows:

[0004] Step S1: The energy storage unit is connected in parallel to the DC bus through the corresponding DC / DC converter and the line resistance R Linep and interacts with the distributed power supply P DG and the constant power load P CPL At the starting point of each sampling period, the inductor current i Lp , output voltage v cp , output current i cp and state-of-chargeSOC p and DC bus voltage v bus are sampled respectively, where p is the energy storage unit number, p = i, j, k, q, in this invention, only the i-th energy storage unit is taken as an example for illustration, it should be noted that the remaining j-th, k-th and q-th energy storage units are all applicable under the method framework of this invention;

[0005] Step S2: in the fault positioning module, the p-th energy storage unit output current i cp and the derivative of the state of charge of the p-th energy storage unit SOC dp are input, and after being processed by the energy storage unit fault positioning method, the fault positioning instruction L p is output, where the specific content of the energy storage unit fault positioning method is as follows:

[0006] Step S2-1: first, signal preprocessing is performed, that is, the SOC dp is first-order low-pass filtered to obtain the filtered derivative of the state of charge of the energy storage unit SOC dfp , and its expression is:

[0007] (1)

[0008] In formula (1), τ is the filter time constant, which is used to suppress false judgments caused by high-frequency noise, T s is the sampling period, SOC dfsp is the derivative of the state of charge of the energy storage unit after filtering at the previous time, which is used for recursive operation;

[0009] Step S2-2: set the fault current threshold b , and the state of charge derivative threshold β , when condition 1 or condition 2 in the fault judgment expression is met, it is determined that the p-th energy storage unit is faulty, and the fault positioning module outputs the fault positioning instruction L p = 1, otherwise, the fault positioning instruction L p = 0, where the fault judgment expression is:

[0010] (2)

[0011] Step S3: in the communication repair module, the fault positioning instruction L pAs input, after the communication network repair control method processing, output communication link reconstruction instruction set S r , to the consistency algorithm in the communication module, wherein the specific content of the communication network repair control method is as follows:

[0012] Step S3-1: First, real-time acquisition of each energy storage unit fault positioning instruction L p , the number of normal energy storage units in the system , wherein, N is the total number of energy storage units, and the number of normal energy storage units V normal is determined according to the number of normal energy storage units in the system normal =4, the energy storage system is running normally, and the energy storage units communicate in a four-source ring structure, when the number of normal energy storage units V normal =3, the communication link connected with the fault unit is disconnected, and the remaining three normal energy storage units are reconstructed to a three-source ring communication structure, when the number of normal energy storage units V normal =2, the communication link connected with the fault unit is disconnected, and the remaining two normal energy storage units are reconstructed to a two-source straight line communication structure, when the number of normal energy storage units V normal <2, the energy storage system triggers a protection mechanism and stops running because it cannot form an effective communication link;

[0013] Step S3-2: According to the communication link reconstruction logic of step S3-1, output the communication link reconstruction instruction set S r ={ S ij , S jk , S kq , S qi | S ik , S jq} and directly act on the consistency algorithm, wherein, S ij , S jk , S kq , S qi defined as the basic link instruction, respectively corresponding to the basic communication link between energy storage units i and j, j and k, k and q, and q and i, S ik , S jqThe link instruction is defined as a repair link instruction, corresponding to the repair links between energy storage units i and k, and j and q, respectively. The on-off rule of the link instruction is as follows: when S ag =1 indicates that the communication link between the energy storage units a and g is in a closed state, S ag =0 indicates that the communication link between the energy storage units a and g is in an open state, where a and g take values of i, j, k, q, and a is not equal to g;

[0014] Step S4: In the communication module, the state of charge of the energy storage unit SOC i , the virtual control variable ζ i , and the communication link reconstruction instruction set S r are input, and the average values of the state of charge of the energy storage unit SOC ai and the virtual control variable ζ ai are obtained through iteration calculation of a consistency algorithm.

[0015] (3)

[0016] In formula (3), Y ij is the average virtual state deviation amount of the i th energy storage unit and the adjacent j th energy storage unit after passing through a communication delay link, Y Rij is the average virtual state deviation amount of the i th energy storage unit and the j th energy storage unit after link updating, and 1 / ( T t s +1) is a communication delay link, where T t is the communication delay between different energy storage units, s is a pull-type transformation complex variable operator, Y aj is the average virtual state variable of the adjacent j th energy storage unit of the i th energy storage unit in four-source ring communication, Y iq is the average virtual state deviation amount of the i th energy storage unit and the adjacent q th energy storage unit after passing through a communication delay link, Y Riq is the average virtual state deviation amount of the i th energy storage unit and the q th energy storage unit after link updating, Y aq is the average virtual state variable of the adjacent q th energy storage unit of the i th energy storage unit in four-source ring communication, Y ikis the average virtual state deviation of the i-th energy storage unit and the j-th energy storage unit which is not adjacent to the i-th energy storage unit after the communication delay link, Y Rik is the average virtual state deviation of the i-th energy storage unit and the k-th energy storage unit after the link update, Y ak is the average virtual state variable of the i-th energy storage unit and the k-th energy storage unit which is not adjacent to the i-th energy storage unit in the four-source ring communication, Y i =[ SOC i 、 ζ i ]is the virtual state variable of the i-th energy storage unit, Y ai =[ SOC ai 、 ζ ai ]is the average virtual state variable of the i-th energy storage unit, h is the communication step length coefficient;

[0017] When the number of normal energy storage units V normal = 4, the energy storage system is in normal operation, the communication module receives the communication link reconstruction instruction set S r is { S ij = 1, S jk = 1, S kq = 1, S qi = 1| S ik = 0, S jq = 0}, the basic communication link of the energy storage unit is closed, and the energy storage unit forms a four-source ring communication in the connection order of node identification i-j-k-q-i at the same time, the i-th energy storage unit is connected with the adjacent j-th and q-th energy storage units, and the expression of the consistency algorithm of the i-th energy storage unit is:

[0018] (4)

[0019] When the number of normal energy storage units V normal = 3, a single energy storage unit in the energy storage system fails, which can be mainly divided into two cases: case 1 is that the k-th energy storage unit which is not adjacent to the i-th energy storage unit in the four-source ring communication fails, at this time the communication link reconstruction instruction set S r is obtained from the system normal operation { S ij = 1, Sjk =1, S kq =1, S qi =1| S ik =0, S jq =0} update to { S ij =1, S jk =0, S kq =0, S qi =1| S ik =0, S jq =1}, at this time the basic communication link related to the kth energy storage unit is disconnected, the repaired link between the jth and qth is connected, and the remaining normal units are reconstructed in the connection order of node identification i-j-q-i three-source ring communication, at this time the ith energy storage unit is still connected and communicated with the adjacent jth and qth energy storage units, and the consistency algorithm expression of the ith energy storage unit is the same as formula (4);

[0020] Case 2 is that the jth or qth energy storage unit adjacent to the ith energy storage unit in the four-source ring communication fails, at this time the communication link reconstruction instruction set S r from the system normal operation { S ij =1, S jk =1, S kq =1, S qi =1| S ik =0, S jq =0} update to { S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0} (unit j fails) or { S ij =1, S jk =1, S kq =0,S qi =0| S ik =1, S jq =0}(unit q failure), at this time, the basic communication link connected with the jth or qth energy storage unit is disconnected, the repair link between the ith and kth is connected, and the remaining normal units reconstruct the three-source ring communication in the connection order of node identification i-k-q-i (unit j failure) or i-j-k-i (unit q failure), at this time, the consistency algorithm expression of the ith energy storage unit is:

[0021] (5)

[0022] When the number of normal energy storage units V normal =2, the energy storage system has two energy storage unit failures, at this time, the failure type can be divided into: energy storage unit simultaneous failure and energy storage unit time period failure, wherein the energy storage unit simultaneous failure can be divided into two cases: case (1) is that the ith energy storage unit and the adjacent jth and qth energy storage units in the four-source ring communication all simultaneously fail, at this time, the communication link reconstruction instruction set S r is updated from the system normal operation S ij =1, S jk =1, S kq =1, S qi =1| S ik =0, S jq =0} to S ij =0, S jk =0, S kq =0, S qi =0| S ik =1, S jq =0}, at this time, the basic communication link of the energy storage unit is disconnected, the repair link between the ith and kth is connected, and the remaining normal units reconstruct the two-source straight line communication in the connection order of node identification i-k-i, at this time, the consistency algorithm expression of the ith energy storage unit is:

[0023] (6)

[0024] Case (2) is that the kth energy storage unit not adjacent to the ith energy storage unit in four-source ring communication and the jth or qth energy storage unit adjacent to the ith energy storage unit in four-source ring communication fail at the same time, at this time, the receiving communication link reconstruction instruction set S r from the system normal operation of { S ij =1, S jk =1, S kq =1, S qi =1| S ik =0, S jq =0} is updated to { S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0}(unit k and j fail) or { S ij =1, S jk =0, S kq =0, S qi =0| S ik =0, S jq =0}(unit k and q fail), at this time, the basic communication link of the kth and jth or qth energy storage unit fails, and the remaining normal units reconstruct two-source straight-line communication according to the connection order of the node identifier i-q-i (unit k and j fail) or i-j-i (unit k and q fail), at this time, the consistency algorithm expression of the ith energy storage unit is:

[0025] (7)

[0026] The energy storage unit fault by time period refers to that after the first unit fails, the system recovers and runs stably for a period of time, and then the second unit fails, in the process, the communication link reconstruction instruction set S rand consistency algorithm need to be updated twice, and two energy storage units fault in time period can also be divided into three cases: case ① for the i-th energy storage unit in the four-source ring communication, the k-th energy storage unit not adjacent to the i-th energy storage unit fails first, in this stage, the communication link reconstruction instruction set S r The update of the consistency algorithm of the i-th unit is the same as case 1 in the above single unit fault, and the remaining normal units reconstruct the three-source ring communication according to the connection order of the node identifier i-j-q-i, at this time, the system recovers stable operation based on the updated instruction set and algorithm, and runs for a period of time, and then any one of the j-th or q-th energy storage unit adjacent to the i-th energy storage unit in the four-source ring communication fails again, in this stage, the communication link reconstruction instruction set S r by S ij =1, S jk =0, S kq =0, S qi =1| S ik =0, S jq =1} is updated to S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0}(unit j fault) or S ij =1, S jk =0, S kq =0, S qi =0| S ik =0, S jq =0}(unit q fault), at this time, the basic communication link connected with the j-th or q-th energy storage unit is disconnected, and the repair link between the j-th and q-th energy storage units is disconnected, the communication topology of the energy storage unit is reconstructed from the three-source ring communication i-j-q-i to the two-source straight line communication i-q-i (unit j fault) or i-j-i (unit q fault), and the consistency algorithm of the i-th energy storage unit is updated from formula (4) to formula (7);

[0027] The initial stage of case 2 and case 3 is the same: the i-th energy storage unit fails first in the four-source ring communication, and the j-th or q-th energy storage unit adjacent to the i-th energy storage unit fails, and the communication link reconstruction instruction set in this stage is S r The update condition and the consistency algorithm of the i-th unit are consistent with the above-mentioned case 2 in the single unit failure, and the remaining normal units reconstruct the three-source ring communication according to the connection order of the node identifier i-k-q-i (unit j failure) or i-j-k-i (unit q failure), at this time, the system recovers stable operation based on the updated instruction set and algorithm, and after running for a period of time, the failure development of case 2 and case 3 is differentiated, which is specifically shown as follows:

[0028] In case 2, the k-th energy storage unit not adjacent to the i-th energy storage unit in the four-source ring communication fails again in this stage, and the communication link reconstruction instruction set S r is updated to S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0}(unit j failure) or S ij =1, S jk =1, S kq =0, S qi =0| S ik =1, S jq =0}(unit q failure) is updated to S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0}(unit j fails first, and unit k fails later) or S ij =1, S jk =0, S kq =0, Sqi =0| S ik =0, S jq =0}(unit q fails first, unit k fails later), at this time, the basic communication link connected with the kth energy storage unit is disconnected, and the repair link between the ith and kth is disconnected, the communication topology of the energy storage unit is reconfigured from the three-source ring communication of i-k-q-i (unit j fails) or i-j-k-i (unit q fails) to the two-source straight-line communication of i-q-i (unit j fails first, unit k fails later) or i-j-i (unit q fails first, unit k fails later), the consistency algorithm of the ith energy storage unit is first updated from formula (4) to formula (5), and then updated from formula (5) to formula (7) during the whole operation of the system;

[0029] In case ③, the other one (the qth or the jth) adjacent to the ith energy storage unit in the four-source ring communication fails again in this stage, the communication link reconstruction instruction set S r =0, S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0}(unit j fails first) or { S ij =1, S jk =1, S kq =0, S qi =0| S ik =1, S jq =0}(unit q fails first) are uniformly updated to { S ij =0, S jk =0, S kq =0, S qi =0| S ik =1, S jq=0}, at this time the basic communication link connected to the qth or jth energy storage unit is disconnected, and the communication topology of the energy storage unit is uniformly reconstructed from the three-source ring communication of ikqi (unit j fails first) or ijki (unit q fails first) to the two-source straight-line communication of iki. During the entire operation of the system, the consensus algorithm of the ith energy storage unit is first updated from equation (4) to equation (5), and then updated from equation (5) to equation (6).

[0030] When the number of normal energy storage units in the system is V normal When the value is less than 2, the system cannot form an effective communication link, triggering the protection mechanism and stopping operation.

[0031] Step S5: In the SOC balancing module, the average state of charge of the energy storage units is calculated. SOC ai Subtract the state of charge of the energy storage unit SOC i The standard deviation of the state of charge of the energy storage unit, d, is obtained. SOC i Then, the standard deviation of the state of charge of the energy storage unit, d SOC i Based on the inductor current of the energy storage unit i Li The positive and negative signs are dynamically selected for output, and the specific logic is as follows: If the inductor current of the energy storage unit is positive... i Li If the value is greater than zero, it indicates that the energy storage system is in a discharging state. At this time, the switching switch in the SOC equalization module points to port 1, and the standard deviation of the state of charge of the energy storage unit is output as d. SOC i If the inductor current of the energy storage unit i Li If the value is less than zero, it indicates that the energy storage system is in a charging state. At this time, the switching switch in the SOC equalization module points to port 2, and the standard deviation of the state of charge of the energy storage unit is d. SOC i Multiply the product by the coefficient -1, invert the output, take the sine of the result (sin), and then multiply the result by the balance adjustment factor. A The results and process coefficients were obtained. w Multiplying them together yields the equilibrium dominant factor. z process coefficients w The expression is:

[0032] (8)

[0033] In equation (8), θ To balance the acceleration factor, μ To balance the precision factor;

[0034] Among them, the dominant factor of equilibriumz The expression is:

[0035] (9)

[0036] Balance the dominant factor z Take the equilibrium adjustment index η The transition coefficient is obtained by raising the power of . c Then the transition coefficient c Take the exponential function e x To obtain the equilibrium variables y , balance variables y Multiply by the maximum rated capacity of the energy storage unit C max With the rated capacity of the energy storage unit C bat The ratio is taken, and the result is added to the coefficient 1 to obtain the SOC equilibrium factor Δ. m ki, where SOC equilibrium factor Δ m ki The expression is:

[0037] (10)

[0038] Step S6: In the current sharing control module, the inductor current of the energy storage unit is... i Li Divide by the maximum rated inductor current of the energy storage unit i Lmax The result is then divided by the current equalization factor. Q Then multiply the result by the SOC equilibrium factor Δ m ki The flow control coefficient is obtained. x i Then subtract the flow control coefficient from the coefficient 1. x i The current equalization factor can be obtained. n i Current equalization factor n i Multiply by DC bus voltage v bus Virtual control variables can be obtained ζ i Among them, virtual control variables ζ i The expression is:

[0039] (11)

[0040] Step S7: In the voltage recovery module, the average value of the virtual control variable is... ζ aiInput, with current sharing factor n i Divide, to get voltage balancing amount v ai Subtract voltage balancing amount v ref Subtract voltage balancing amount v ai Pass through a voltage recovery link PI controller G N (s), to get voltage recovery adjustment amount v fi ;

[0041] Step S8: In the voltage and current double closed loop module, voltage recovery adjustment amount v fi is taken as input, and is added to DC bus voltage reference value v ref , and then subtracts energy storage unit output voltage v ci , and the obtained result passes through a voltage outer loop PI controller G V (s) to get current inner loop reference current i refi , and the obtained result passes through a voltage outer loop PI controller i refi , and the obtained result passes through a voltage outer loop PI controller m ki , and the obtained result passes through a voltage outer loop PI controller i Li , and the obtained result passes through a voltage outer loop PI controller G I (s), and the obtained result passes through a voltage outer loop PI controller v si , to get driving voltage v si , and the obtained result passes through PWM modulation to output stable and reliable modulation signal d ti .

[0042] Further, in step S2, the value range of filter time constant τ is 0.1< τ <1.5, the value range of sampling period T s is 0.0001< T s <0.01, the value range of fault current threshold b is 0.01< b <0.1, the value range of state of charge derivative small threshold β is 0.0001<β <0.01; In step S4, the communication step size coefficient h The range of values ​​is 0 < h <1, Communication delay between different energy storage units T t The value range is 0.0001 < T t <0.01; In step S5, the balancing adjustment factor A The value range is 0.3 < A <0.9, equilibrium acceleration factor θ The value range is 0.2 < θ <0.7, Balanced Precision Factor μ The value range is 0.0001 < μ <0.01, equilibrium adjustment index η The value range is 0.1 < η <1; In step S6, the current averaging factor Q The value range is 10 < Q <22.

[0043] Compared with existing technologies, the principles and advantages of this solution are as follows:

[0044] This invention discloses a multi-scenario collaborative control method for distributed energy storage systems based on fault location and dynamic communication repair. It mainly includes a fault location module, a communication repair module, a communication module, a SOC balancing module, a current sharing control module, a voltage recovery module, and a voltage and current dual closed-loop module. The fault location module accurately identifies and locates faulty energy storage units; the communication repair module achieves adaptive matching between the communication network and the system control topology; the communication module enables adjacent energy storage units to exchange information to obtain the average value of system SOC and control state variables; and the SOC balancing module, current sharing control module, and voltage recovery module achieve SOC balancing of each unit and proportional distribution of output current according to capacity without sampling output current, while maintaining the bus voltage at its rated value. This method adapts to multiple scenarios such as system startup, steady-state operation, and fault repair, enabling stable, efficient, and collaborative operation of the distributed energy storage system. Attached Figure Description

[0045] Figure 1 This is the main circuit diagram of the distributed energy storage system in an embodiment of the present invention;

[0046] Figure 2 This is a block diagram of a multi-scenario collaborative control method for a distributed energy storage system based on fault location and dynamic communication repair in an embodiment of the present invention;

[0047] Figure 3 This is a flowchart of the fault location and dynamic communication repair method in an example of the present invention;

[0048] Figure 4 Figure for real-time change of communication topology of energy storage unit in embodiment of the present application;

[0049] Figure 5 State of charge in embodiment of the present application SOC p Waveform diagram;

[0050] Figure 6 DC bus voltage in embodiment of the present application v bus Waveform diagram;

[0051] Figure 7 Output current on DC side in embodiment of the present application i cp Waveform diagram;

[0052] Figure 8 Link communication waveform diagram in embodiment of the present application. DETAILED DESCRIPTION

[0053] The present application will be further described below in conjunction with specific embodiments:

[0054] Figure 1 The main circuit diagram of the distributed energy storage system is shown, and the energy storage units DESU p The corresponding DC-DC converter and line resistance R linep are connected in parallel to the DC bus, and the distributed power supply P DG , constant power load P CPL constitute an energy interaction network together, and the parameters of the main circuit are defined as follows: p represents the number of energy storage units, p = i, j, k, q; i Lp , v cp , i cp , C p represent the inductance current, output voltage, output current and support capacitor of the pth energy storage unit respectively, R CPL represents the line resistance on the constant power load side, R DG and C DG are the line resistance and parasitic capacitance of the distributed power supply respectively, wherein the specific numerical values of the parameters are: the line resistance corresponding to the four energy storage units R linei , R linej , Rlinek and R lineq 0.7Ω, 0.8Ω, 0.74Ω, 0.6Ω, and the capacitances are 6F, 6F, 4F, 4F respectively, the inductances L p 0.009H, and the capacitances C p 0.003F; the distributed power supply P DG 16kW, and the corresponding line resistance R DG 0.3Ω, and the parasitic capacitance C DG 0.001F; the constant power load P CPL 8kW, and the corresponding line resistance R CPL 0.4Ω; in addition, v bus is a DC bus voltage, v ref is set to 400V.

[0055] Figure 2 The control block diagram of the multi-scenario collaborative control method of the distributed energy storage system based on fault positioning and dynamic communication repair is shown, and the specific content is as follows:

[0056] Step S1: the energy storage unit is connected in parallel to the DC bus through the corresponding DC / DC converter and the line resistance R Linep and interacts with the distributed power supply P DG and the constant power load P CPL At the starting point of each sampling period, the inductance current i Lp , the output voltage v cp , the output current i cp , the state of charge SOC p and the DC bus voltage v bus of the pth energy storage unit are sampled, wherein p is the energy storage unit number, p=i, j, k, q, and in the present application, only the ith energy storage unit is selected as an example for description, and it should be noted that the remaining jth, kth and qth energy storage units are applicable under the method framework of the present application;

[0057] Step S2: in the fault positioning module, the output current icp and the derivative of the state of charge of the pth energy storage unit SOC dp As input, after being processed by the energy storage unit fault positioning method, the output is the fault positioning instruction L p , wherein the specific content of the energy storage unit fault positioning method is as follows:

[0058] Step S2-1: First, signal preprocessing, that is, the SOC dp First-order low-pass filtering is performed to obtain the filtered derivative of the state of charge of the energy storage unit SOC dfp The expression is:

[0059] (12)

[0060] In formula (12), τ is the filtering time constant, which is used to suppress false judgments caused by high-frequency noise, T s is the sampling period, SOC dfsp is the derivative of the state of charge of the energy storage unit after filtering at the last time, which is used for recursive operation;

[0061] Step S2-2: Set the fault current threshold b , the state of charge derivative threshold β When condition 1 or condition 2 in the fault determination expression is met, it is determined that the pth energy storage unit fails, and the fault positioning module outputs the fault positioning instruction L p = 1, otherwise, output the fault positioning instruction L p = 0, wherein the fault determination expression is:

[0062] (13)

[0063] Step S3: In the communication repair module, the fault positioning instruction L p As input, after being processed by the communication network repair control method, the output is a set of communication link reconstruction instructions S r , which acts on the consistency algorithm in the communication module, wherein the specific content of the communication network repair control method is as follows:

[0064] Step S3-1: First, real-time acquisition of each energy storage unit fault positioning instruction L p , the number of normal energy storage units is counted , wherein Nis the total number of energy storage units, and V is the normal number of energy storage units in the system normal The communication link reconstruction logic is formulated as follows: when V normal = 4, the energy storage system is in normal operation, and the energy storage units communicate in a four-source ring structure; when V normal = 3, the communication link connected to the faulty unit is disconnected, and the remaining three normal energy storage units are reconstructed into a three-source ring communication structure; when V normal = 2, the communication link connected to the faulty unit is disconnected, and the remaining two normal energy storage units are reconstructed into a two-source straight-line communication structure; when V normal < 2, the energy storage system triggers a protection mechanism and stops running due to the inability to form an effective communication link;

[0065] Step S3-2: According to the communication link reconstruction logic of step S3-1, output a set of communication link reconstruction instructions S r ={ S ij , S jk , S kq , S qi | S ik , S jq} and directly act on the consistency algorithm, wherein S ij , S jk , S kq , S qi are defined as basic link instructions corresponding to the basic communication links between energy storage units i and j, j and k, k and q, and q and i, respectively S ik , S jq are defined as repair link instructions corresponding to the repair links between energy storage units i and k, and j and q, respectively. The on-off rule of the link instruction is: when S ag = 1 indicates that the communication link between energy storage units a and g is in a closed state, S ag = 0 indicates that the communication link between energy storage units a and g is in an open state, where a and g take values of i, j, k, and q, and a is not equal to g;

[0066] Step S4: In the communication module, the state of charge of the energy storage unitSOC i virtual control variable ζ i and communication link reconstruction instruction set S r As input, the average state of charge of the energy storage unit is calculated by iteration of the consistency algorithm SOC ai and the average value of the virtual control variable ζ ai where the expression of the consistency algorithm is:

[0067] (14)

[0068] In formula (14), Y ij is the average virtual state deviation of the i-th energy storage unit and the j-th energy storage unit adjacent thereto after passing through the communication delay link, Y Rij is the average virtual state deviation of the i-th energy storage unit and the j-th energy storage unit after link update, 1 / ( T t s +1) is a communication delay link, wherein T t is the communication delay between different energy storage units, s is a pull-type transformation complex variable operator, Y aj is the average virtual state variable of the j-th energy storage unit adjacent to the i-th energy storage unit in four-source ring communication, Y iq is the average virtual state deviation of the i-th energy storage unit and the q-th energy storage unit adjacent thereto after passing through the communication delay link, Y Riq is the average virtual state deviation of the i-th energy storage unit and the q-th energy storage unit after link update, Y aq is the average virtual state variable of the q-th energy storage unit adjacent to the i-th energy storage unit in four-source ring communication, Y ik is the average virtual state deviation of the i-th energy storage unit and the j-th energy storage unit not adjacent thereto after passing through the communication delay link, Y Rik is the average virtual state deviation of the i-th energy storage unit and the k-th energy storage unit after link update, Y ak is the average virtual state variable of the k-th energy storage unit not adjacent to the i-th energy storage unit in four-source ring communication, Y i =[ SOC i 、 ζi ] is a virtual state variable of the i th energy storage unit, Y ai [ SOC ai , ζ ai ] is an average virtual state variable of the i th energy storage unit, h is a communication step length coefficient;

[0069] When the number of normal energy storage units V normal = 4, the energy storage system is in normal operation, and the communication module receives a communication link reconstruction instruction set S r is { S ij = 1, S jk = 1, S kq = 1, S qi = 1| S ik = 0, S jq = 0}, the basic communication link of the energy storage unit is closed, and the energy storage unit forms a four-source ring communication in the connection order of the node identification i-j-k-q-i. At this time, the i th energy storage unit is connected to the adjacent j th and q th energy storage units for communication, and the expression of the consistency algorithm of the i th energy storage unit is:

[0070] (15)

[0071] When the number of normal energy storage units V normal = 3, a single energy storage unit in the energy storage system fails, which can be mainly divided into two cases: case 1 is that the k th energy storage unit not adjacent to the i th energy storage unit fails in the four-source ring communication. At this time, the communication link reconstruction instruction set S r is updated from the { S ij = 1, S jk = 1, S kq = 1, S qi = 1| S ik = 0, S jq = 0} of the system in normal operation to { S ij = 1, S jk = 0, S kq = 0,S qi =1| S ik =0, S jq =1}, at this time the basic communication link related to the kth energy storage unit is disconnected, the repair link between the jth and qth units is connected, and the remaining normal units reconstruct the three-source ring communication according to the connection order of the node identifier ijqi. At this time, the ith energy storage unit is still connected and communicated with the adjacent jth and qth energy storage units. The consistency algorithm expression of the ith energy storage unit is the same as that of equation (15).

[0072] Case 2 is when the i-th energy storage unit experiences a failure in its adjacent j-th or q-th energy storage unit within the four-source ring communication, in which case the communication link reconfiguration instruction set is used. S r From the system during normal operation { S ij =1, S jk =1, S kq =1, S qi =1| S ik =0, S jq =0} is updated to { S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0}(unit j fault) or { S ij =1, S jk =1, S kq =0, S qi =0| S ik =1, S jq =0} (unit q failure), at this time, the basic communication link connected to the j-th or q-th energy storage unit is disconnected, the repair link between the i-th and k-th units is reconnected, and the remaining normal units reconstruct the three-source ring communication according to the connection order of node identifier ikqi (unit j failure) or ijki (unit q failure). At this time, the consensus algorithm expression of the i-th energy storage unit is:

[0073] (16)

[0074] When the number of normal energy storage units V normal = 2, the energy storage system has two energy storage unit failures, and the fault type can be divided into: energy storage unit simultaneous failure and energy storage unit periodical failure, wherein the energy storage unit simultaneous failure can be divided into two cases: case (1) is that the i-th energy storage unit and the j-th and q-th energy storage units adjacent to the i-th energy storage unit in the four-source ring communication all simultaneously fail, at this time, the communication link reconstruction instruction set S r is updated to S ij = 1, S jk = 1, S kq = 1, S qi = 1 S ik = 0, S jq = 0 S ij = 0, S jk = 0, S kq = 0, S qi = 0 S ik = 1, S jq = 0 , at this time, the basic communication link of the energy storage unit is disconnected, the repair link between the i-th and k-th energy storage units is connected, and the remaining normal units reconstruct two-source straight-line communication according to the connection order of node identification i-k-i, at this time, the consistency algorithm expression of the i-th energy storage unit is:

[0075] (17)

[0076] case (2) is that the k-th energy storage unit not adjacent to the i-th energy storage unit in the four-source ring communication simultaneously fails with any one of the j-th or q-th energy storage unit adjacent to the i-th energy storage unit in the four-source ring communication, at this time, the received communication link reconstruction instruction set S r is updated to S ij = 1, S jk = 1, S kq = 1, S qi = 1 Sik =0, S jq =0} update to { S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0} (unit k and j failure) or { S ij =1, S jk =0, S kq =0, S qi =0| S ik =0, S jq =0} (unit k and q failure), at this time, the basic communication link between the kth and the jth or the qth energy storage unit is disconnected, and the remaining normal units reconfigure two-source straight-line communication in the connection order of node identification i-q-i (unit k and j failure) or i-j-i (unit k and q failure), at this time, the consistency algorithm expression of the ith energy storage unit is:

[0077] (18)

[0078] The time-period fault of the energy storage unit refers to that after the first unit fails, the system resumes stable and runs for a period of time, and then the second unit fails, in which process the communication link reconstruction instruction set S r and the consistency algorithm need to be dynamically updated twice, and the two energy storage units time-period fault can also be divided into three cases: case ① is that the kth energy storage unit, which is not adjacent to the ith energy storage unit in the four-source ring communication, fails first, in which stage, the update of the communication link reconstruction instruction set S r and the consistency algorithm of the ith unit are the same as case 1 in the above single unit failure, the remaining normal units reconfigure three-source ring communication in the connection order of node identification i-j-q-i, at this time, the system resumes stable operation based on the updated instruction set and algorithm, and after running for a period of time, the jth or the qth energy storage unit adjacent to the ith energy storage unit in the four-source ring communication fails again, in which stage, the communication link reconstruction instruction set S r is updated by { S ij =1,S jk = 0, S kq = 0, S qi = 1 S ik = 0, S jq = 1 S ij = 0, S jk = 0, S kq = 0, S qi = 1 S ik = 0, S jq = 0} (unit j failure) or { S ij = 1, S jk = 0, S kq = 0, S qi = 0 S ik = 0, S jq = 0} (unit q failure), at this time, the basic communication link connected with the jth or qth energy storage unit is disconnected, and the repair link between the jth and qth energy storage units is disconnected, and the communication topology of the energy storage unit is reconfigured from the three-source ring communication of i-j-q-i to the two-source straight-line communication of i-q-i (unit j failure) or i-j-i (unit q failure), and the consistency algorithm of the ith energy storage unit is updated from formula (15) to formula (18);

[0079] The initial stage of case 2 and case 3 is the same: the jth or qth energy storage unit adjacent to the ith energy storage unit in the four-source ring communication fails first, and the communication link reconstruction instruction set S r is updated, and the consistency algorithm of the ith unit is consistent with the above-mentioned case 2 of single unit failure, and the remaining normal units reconfigure the three-source ring communication according to the connection order of the node identifier i-k-q-i (unit j failure) or i-j-k-i (unit q failure), at this time, the system recovers stable operation based on the updated instruction set and algorithm, and runs for a period of time, and the fault development of case 2 and case 3 is differentiated, which is specifically manifested as:

[0080] In case 2, the kth energy storage unit not adjacent to the ith energy storage unit in the four-source ring communication fails again, and in this stage, the communication link reconstruction instruction set Sr Depend on{ S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0}(unit j fault) or { S ij =1, S jk =1, S kq =0, S qi =0| S ik =1, S jq =0}(cell q fault) updated to { S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0}(Unit j fails first, unit k fails later) or { S ij =1, S jk =0, S kq =0, S qi =0| S ik =0, S jq =0}(unit q fails first, unit k fails later), at this time the basic communication link connected to the kth energy storage unit is disconnected, and the repair link between the ith and kth units is disconnected. The communication topology of the energy storage unit is reconstructed from the three-source ring communication of ikqi (unit j fails) or ijki (unit q fails) to the two-source straight communication of iqi (unit j fails first, unit k fails later) or iji (unit q fails first, unit k fails later). During the entire operation of the system, the consistency algorithm of the ith energy storage unit is first updated from equation (15) to equation (16), and then updated from equation (16) to equation (18).

[0081] In case 3, the i-th energy storage unit fails again in the adjacent one (q-th or j-th) of the four-source ring communication. At this stage, the communication link reconstruction instruction set S r = 0, S ij = 0, S jk = 1, S kq = 1, S qi = 1, S ik = 1, S jq = 0} (unit j fails first) or { S ij = 1, S jk = 1, S kq = 0, S qi = 0, S ik = 1, S jq = 0} (unit q fails first) are updated to { S ij = 0, S jk = 0, S kq = 0, S qi = 0, S ik = 1, S jq = 0}, at which time the basic communication link connected to the q-th or j-th energy storage unit is disconnected, and the communication topology of the energy storage unit is uniformly reconstructed from the three-source ring communication of i-k-q-i (unit j fails first) or i-j-k-i (unit q fails first) to the two-source straight-line communication of i-k-i. The consistency algorithm of the i-th energy storage unit is first updated from equation (15) to equation (16), and then from equation (16) to equation (17) during the entire operation of the system;

[0082] When the number of normal energy storage units V normal <2, the energy storage system triggers the protection mechanism and stops running due to the inability to form an effective communication link.

[0083] Step S5: In the SOC equalization module, the average value of the state of charge of the energy storage unit SOC ai is subtracted from the state of charge of the energy storage unit SOC i to obtain the standard deviation d of the state of charge of the energy storage unitSOC i the standard deviation of the state of charge of the energy storage unit d SOC i according to the positive and negative of the inductance current of the energy storage unit i Li , the specific logic is as follows: if the inductance current of the energy storage unit i Li is greater than zero, it indicates that the energy storage system is in a discharging state, at this time the switching switch in the SOC equalization module points to port 1, and the standard deviation of the state of charge of the energy storage unit d SOC i is output, if the inductance current of the energy storage unit i Li is less than zero, it indicates that the energy storage system is in a charging state, at this time the switching switch in the SOC equalization module points to port 2, and the standard deviation of the state of charge of the energy storage unit d SOC i is multiplied by -1 to get the inverse output, and the result is taken as the sine function sin, and the result is multiplied by the equalization adjustment factor A , the result is multiplied by the process coefficient w to get the equalization dominant factor z , wherein the expression of the process coefficient w is:

[0084] (19)

[0085] In formula (19), θ is the equalization acceleration factor, μ is the equalization accuracy factor;

[0086] wherein the expression of the equalization dominant factor z is:

[0087] (20)

[0088] The equalization dominant factor z is taken to the power of the equalization adjustment index η to get the transition coefficient c , and the transition coefficient c is taken to the exponential function e x to get the equalization variable y , and the equalization variable y is multiplied by the maximum rated capacity of the energy storage unit C max and the rated capacity of the energy storage unit C bat , the result is added to the coefficient 1 to get the SOC equalization factor Δ m ki, wherein the SOC equalization factor Δm ki The expression of is:

[0089] (21)

[0090] Step S6: In the current sharing control module, the energy storage unit inductor current i Li is divided by the maximum rated value of the energy storage unit inductor current i Lmax , and the result is divided by the current sharing coefficient Q , and the obtained result is multiplied by the SOC balancing factor Δ m ki , to obtain the current sharing control coefficient x i , and the coefficient 1 is subtracted from the current sharing control coefficient x i , to obtain the current sharing factor n i , and the current sharing factor n i is multiplied by the DC bus voltage v bus , to obtain the virtual control variable ζ i , wherein the expression of the virtual control variable ζ i is:

[0091] (22)

[0092] Step S7: In the voltage recovery module, the average value of the virtual control variable ζ ai is input, and divided by the current sharing factor n i , to obtain the voltage balancing amount v ai , the DC bus voltage reference value v ref is subtracted from the voltage balancing amount v ai , and then passes through a voltage recovery link PI controller G N (s), to obtain the voltage recovery adjustment amount v fi ;

[0093] Step S8: In the voltage and current double closed loop module, the voltage recovery adjustment amount v fi is input, and added to the DC bus voltage reference value v ref , and then subtracted from the energy storage unit output voltagev ci The result is passed through a voltage outer loop PI controller. G V (s) Obtain the reference current of the inner current loop. i refi The inner loop reference current will be used. i refi With SOC equilibrium factor Δ m ki Multiply the results and subtract the inductor current of the energy storage unit from the result. i Li Then it goes through a current inner loop PI controller G I (s), the result is passed through a limiting circuit to obtain the driving voltage. v si , drive voltage v si After passing through PWM Modulation can output a stable and reliable modulated signal. d ti .

[0094] Furthermore, in step S2, the filtering time constant... τ The value range is 0.1 < τ <1.5, sampling period T s The value range is 0.0001 < T s <0.01, fault current threshold b The value range is 0.01 < b <0.1, small threshold of the derivative of the state of charge β The value range is 0.0001 < β <0.01; In step S4, the communication step size coefficient h The range of values ​​is 0 < h <1, Communication delay between different energy storage units T t The value range is 0.0001 < T t <0.01; In step S5, the balancing adjustment factor A The value range is 0.3 < A <0.9, equilibrium acceleration factor θ The value range is 0.2 < θ <0.7, Balanced Precision Factor μ The value range is 0.0001 < μ <0.01, equilibrium adjustment index η The value range is 0.1 < η <1; In step S6, the current averaging factorQ The value range is 10 < Q <22.

[0095] Figure 3 The diagram shows the flowchart of the fault location and dynamic communication repair method, which mainly includes four steps, as follows:

[0096] Step 1: After the energy storage system starts up, perform a self-test as described in Step 1. Within 0.3 seconds of startup, monitor the output current of the energy storage unit. i cp The original value of the derivative of the state of charge of the energy storage unit SOC dp If either of them approaches 0, the system is deemed to be malfunctioning, the energy storage system is restarted, and step 1 is executed again. If neither of them approaches 0, the next step is performed.

[0097] Step 2: The system performs step 2 to locate the fault. First, the original value of the derivative of the state of charge of the energy storage unit is obtained. SOC dp Signal preprocessing is performed to obtain the derivative of the state of charge of the filtered energy storage unit. SOC dfp Subsequently, the system sets the fault current threshold. b and the small threshold of the derivative of the state of charge β And monitor the output current of the energy storage unit. i cp and filtered SOC dfp ,like i cp In (- b , b) Within the interval, or SOC dfp The absolute value is less than ζ That is, if any condition is met, the energy storage unit is determined to be a faulty unit, and a corresponding fault location command is output. L p =1; If neither of the two conditions is met, it is determined to be a normal unit, and the output is 1. L p =0, which is the value of V calculated in step 3 for the number of normal energy storage units. normal Provide evidence, then proceed to step 3;

[0098] Step 3: The system performs communication repair in step 3, first collecting the fault commands output in step 2 in real time. L p The number of normal energy storage units V in the current system is calculated. normal V was subsequently determined. normal Is it less than 2? If V normal ≥2, then according to V normalPerform corresponding communication link repair operation logic: when V normal =4, maintain four-source ring communication, when V normal =3, disconnect the associated link of the faulty unit and reconstruct as a three-source ring structure, when V normal =2, disconnect the associated link of the faulty unit and switch to a two-source straight line structure, while outputting a set of link reconstruction instructions S r , and acting on the consistency algorithm, which synchronously adjusts each normal unit through information exchange between adjacent units, and outputs the average state of charge of the energy storage unit SOC ap , and determines whether the SOC equalization error SOC p - SOC ap | <5% and bus voltage deviation v bus - v ref | <5% v ref , if it is satisfied, it is determined that the system is cooperatively stable, and enters the normal operation mode, and steps 2 and 3 are cycled to realize real-time monitoring of unit faults and dynamic repair of system communication, if it is not satisfied, the link is reconstructed again according to the current V normal , output a new set of link reconstruction instructions S r , and act on the consistency algorithm to synchronously adjust each normal unit again until the stable condition is met; in addition, if V normal <2, it indicates that the system cannot form an effective communication link, and a trigger signal is output to step 4, and then step 4 is entered;

[0099] Step 4: The system performs step 4 to protect the system. When receiving the trigger signal output by step 3, the system will immediately start the shutdown protection mechanism to stop the charging and discharging operation of all energy storage units, and the energy storage system stops running.

[0100] Figure 4 The real-time change diagram of the communication topology of the energy storage unit is shown. Four energy storage units are connected through six communication links ij, jk, kq, qi and ik, jq, the communication switches of each link, and the communication link reconstruction instruction set DESU i , DESU j , DESU k and DESU q , S r = { S ij , Sjk , S kq , S qi | S ik , S jq} consists of, wherein the four links ij, jk, kq, qi are basic communication links, S ij , S jk , S kq , S qi are basic link instructions for controlling the on-off of the communication switch on the basic communication link, and the two links ik, jq are repair links, S ik , S jq are repair link instructions for controlling the on-off of the communication switch on the repair link, when the system is normally running, the four basic communication links are closed, and the other two repair links are in an open state, forming a four-source ring communication; when the system has a pth (such as DESU i ) single energy storage unit fault, the basic communication and repair links connected with the faulty energy storage unit are all disconnected, the basic communication links of the remaining normal energy storage units are maintained in a closed state, and the corresponding repair links are switched from open to closed, and the communication topology is reconfigured from a four-source ring to a three-source ring communication; when the system has two energy storage unit faults, the fault types can be divided into: simultaneous energy storage unit faults and time period energy storage unit faults, wherein the simultaneous energy storage unit faults include two cases: the first case is a unit same edge fault, that is, the pth and its adjacent energy storage units (such as DESU i and DESU j ) simultaneously fail, the basic communication and repair links connected with the two faults are all disconnected, the basic communication links of the remaining normal energy storage units are maintained in a closed state, and the communication topology is reconfigured from a four-source ring to a two-source straight line communication, and the second case is a unit diagonal fault, that is, the pth and its non-adjacent energy storage units (such as DESU i and DESU kWhen the four basic links are all disconnected at the same time, the repair links between the remaining normal energy storage units are switched from disconnected to closed, and the communication topology is reconfigured from a four-source ring to a two-source straight line communication; when the energy storage units fail in time periods, two energy storage units fail in a sequential order, and there are two cases of unit time period same edge failure and unit time period diagonal failure, and the communication topology changes are consistent: the pth unit fails first, at this time, the communication topology changes are the same as single unit failure, and the communication topology is reconfigured from a four-source ring to a three-source ring communication, then, another unit adjacent or not adjacent to the unit p fails, and the basic communication and repair links connected to the failed unit are all disconnected, the basic communication links or repair links of the remaining normal energy storage units remain closed, and the communication topology is updated from a three-source ring to a two-source straight line communication.

[0101] Figure 5 The state of charge of the energy storage unit is shown SOC p The waveform diagram shows the initial state of charge of the four energy storage units SOC i 、 SOC j 、 SOC k 、 SOC q are 91%, 88%, 86%, and 84%, respectively, after the energy storage system is started, the four energy storage units are working in a discharge state, under the action of the SOC balancing module in the application, the four SOC curves converge at a specific rate, when the system runs to 3.5s, the ith energy storage unit fails and exits the operation in advance, and the SOC curve of the unit forms a horizontal straight line at this point, which is always stable at 82% at the time of failure. This mutation not only changes the original power distribution of the energy storage system, but also affects the adaptation of the communication network to the main circuit and control topology, at this time, the remaining three energy storage units need to undertake all the discharge tasks, under the joint action of the fault positioning module, the communication repair module and the SOC balancing module, SOC i The descending slopes of the three curves are all steep, and the balancing is completed at 4.2s, and then the discharge continues at the same rate, when the system runs to 6s, the system switches from the discharge mode to the charging mode due to the power supply from the external distributed power supply, at the moment of mode switching, under the real-time adjustment of the SOC balancing module, SOC j 、 SOC k and SOC q The descending slopes of the three curves are all steep, and the balancing is completed at 4.2s, and then the discharge continues at the same rate, when the system runs to 6s, the system switches from the discharge mode to the charging mode due to the power supply from the external distributed power supply, at the moment of mode switching, under the real-time adjustment of the SOC balancing module, SOC j 、 SOC k and SOC qThe slope of the three curves changes from negative to positive, i.e. from falling to rising, and continues to maintain the balanced state and continues to charge at the same rate, and when the system runs to 8s, the kth energy storage unit fails and exits the operation in advance, and the SOC k The curve forms a horizontal straight line here, and is always stable at 80.1% at the time of failure. This time, the exit changes the power distribution of the system and the adaptation relationship of the communication network and the main circuit and control topology again, and at this time all the charging power is borne by the remaining jth and qth energy storage units, SOC j and SOC q The rising slope of the two curves becomes steep, and continues to maintain the balanced state until the energy storage system stops running. It can be seen that under the synergistic action of the fault positioning module, the communication repair module and the SOC balancing module, the system still maintains the SOC balance of the remaining energy storage units in the face of complex working conditions such as the time-sharing exit of energy storage units and the switching of system operation modes.

[0102] Figure 6 The DC bus voltage of the distributed energy storage system is shown v bus The waveform diagram, even in the face of complex working conditions such as the time-sharing exit of energy storage units and the switching of system operation modes, the DC bus voltage although there is a certain voltage fluctuation, but can control the voltage fluctuation amplitude within 12V, and after each fluctuation occurs, the DC bus voltage can recover to the voltage reference value 400V within 0.7s, and can also be stable to 400V nearby in the remaining time.

[0103] Figure 7 The DC side output current of the distributed energy storage system is shown i cp The waveform diagram, DESU i , DESU j , DESU k and DESU q The rated capacity ratio of the four energy storage units is 3:3:2:2 respectively. After the start of the energy storage system, the output currents of the four energy storage units gradually converge according to their respective rated capacities under the action of the current equalization control module. When the system runs to 3.5s, the ith energy storage unit fails and exits the operation in advance, and the output current of the ith energy storage unit i ci Instantaneously to 0, at this time the original current distribution balance of the system is broken, and the remaining DESU j , DESUk and DESU q The total output current of the system needs to be shared. Under the action of the fault positioning module and the communication repair module, the communication network of the system, the main circuit and the control topology are adapted, and under the dynamic adjustment of the current sharing module, the output currents of the three energy storage units quickly respond and are distributed as 8.57 A, 5.71 A and 5.71 A at about 4.2s, DESU j , DESU k and DESU q The current sharing is realized, and the output currents are 8.57 A, 5.71 A and 5.71 A respectively, which meets the accurate distribution principle of 3:2:2. When the system runs to 6s, the system switches from the discharging mode to the charging mode as the external distributed power supplies the energy storage system, and the output current of the energy storage unit also changes from positive to negative, that is, the external output changes to the internal current absorption. Under the dynamic adaptation of the current sharing control module and at about 6.6s, DESU j , DESU k and DESU q The current sharing is realized again, and the output currents are -8.57 A, -5.71 A and -5.71 A respectively, which meets the accurate distribution principle of 3:2:2. When the system runs to 8s, the kth energy storage unit fails and exits the operation in advance, and the output current of the kth energy storage unit i ck instantaneously reaches 0, and the original current distribution balance of the system is broken again, and the remaining DESU j and DESU q The total output current of the external distributed power needs to be shared. Under the action of the fault positioning module and the communication repair module, the communication network of the system, the main circuit and the control topology are adapted, and under the dynamic adjustment of the current sharing module and at about 8.4s, DESU j and DESU q The current sharing is realized, and the output currents are -12 A and -8 A respectively, which meets the accurate distribution principle of 3:2. It can be seen that under the synergistic effect of the fault positioning module, the communication repair module and the current sharing control module, the system can still maintain the accurate proportional distribution of the output current of the remaining energy storage unit in the face of the complex working conditions such as the time-sharing exit of the energy storage unit and the switching of the system running mode.

[0104] Figure 8The link communication waveform diagram of the distributed energy storage system is shown. After the system is started, the basic communication links ij, jk, kq and qi exist basic values. The fluctuation at time 0 corresponds to system initialization communication handshake and topology establishment. Each energy storage unit mutually performs node identification and link penetration, and forms a ring-shaped communication according to the connection order of i-j-k-q-i. At around 0.3s, the communication information of the four links synchronously converges to the steady-state value 2 and is stably maintained at the steady-state value 2. At this time, the ring-shaped communication network enters a steady-state operation mode. Each energy storage unit exchanges power distribution instructions, SOC state detection and other data in real time through the link to support system discharge. When the system runs to 3.5s, the i th energy storage unit suddenly fails and exits operation. The original communication topology unit i fails to break, and the communication values of the basic links ij and qi connected with the unit i instantaneously decrease to 0, while the communication value of the repair link jq instantaneously increases from 0 to 2.1. At the same time, the communication of the links jk and kq deviates from the steady-state value, and the three communication links jointly appear short-time oscillation. At this time, the system fault positioning module quickly identifies the fault unit i, and the communication repair module synchronously starts the topology reconstruction algorithm to reconstruct the communication topology into a ring-shaped communication with the connection order of j-k-q-j. Around 4.2s, the communication values of the links jk, kq and jq synchronously converge to the steady-state value 2 and are stably maintained in this state. When the system runs to 6s, the system switches from the discharge mode to the charging mode, and the power flow direction is reversed. This working condition change has a certain influence on the communication link. The communication values of the links jk, kq and jq all appear short-time fluctuation, but under the dynamic adjustment of the communication repair module, they again converge to the steady-state value 2 around 6.6s and are stably maintained, ensuring that the units j, k and q can exchange charging current instructions, energy storage unit charging states and other data in real time during the charging process. When the system runs to 8s, the k th energy storage unit suddenly fails and exits operation. The original ring-shaped communication topology j-k-q-j is broken due to the failure of the unit k, and the communication values of the links jk and kq connected with the unit k instantaneously decrease to 0. Only the communication value of the link jq appears obvious fluctuation. At this time, the system fault positioning module quickly identifies the fault unit k, and the communication repair module starts the secondary topology reconstruction algorithm to reconstruct the communication topology into a straight-line communication with the connection order of j-q-j. Around 8.4s, the communication value of the link jq returns to the steady-state value 2 and is stably maintained in this state until the energy storage system stops running.

[0105] From the above analysis, the application designs a distributed energy storage system multi-scenario collaborative control method based on fault positioning and dynamic communication repair, a fault positioning controller is designed to realize accurate identification and positioning of the running abnormal or fault energy storage unit, a communication repair controller is designed to realize rapid reconstruction of the communication topology and recovery of the link stability after the fault occurs, ensure the continuity and reliability of the data interaction between the remaining energy storage units, and on this basis, an improved SOC equalizer, current equalization and voltage recovery controller are designed, without sampling the output current, the SOC of each energy storage unit can be balanced, the output current can be distributed according to the capacity of the energy storage unit in proportion, and the bus voltage can be maintained to the rated value target, realizing the stable, efficient and collaborative operation of the distributed energy storage system under the complex scenes of multi-energy storage unit fault exit, charge-discharge mode switching and the like.

[0106] The above-mentioned embodiments are only the preferred embodiments of the present application, and are not intended to limit the scope of the application. Any changes made in accordance with the shape and principle of the present application should be covered within the scope of protection of the present application.

Claims

1. A distributed energy storage system multi-scenario collaborative control method based on fault location and dynamic communication repair, characterized in that, Comprise the following steps: Step S1: the energy storage unit samples the inductance current R Linep parallel to the DC bus, and the distributed power P DG and the constant power load P CPL interacts with energy at the beginning of each sampling period, and the inductance current i Lp , output voltage v cp , output current i cp , state of charge SOC p and DC bus voltage v bus of the pth energy storage unit are respectively sampled, where p is the energy storage unit number, p=i, j, k, q; Step S2: In the fault location module, the pth energy storage unit output current i cp and the derivative of the pth energy storage unit state of charge original value SOC dp As input, after being processed by the energy storage unit fault location method, the fault location instruction is output L p ; Step S3: In the communication repair module, the fault location instruction L p As input, after processing by the communication network repair control method, the output communication link reconstruction instruction set S r , acting on the consistency algorithm in the communication module; Step S4: In the communication module, the energy storage unit state of charge SOC i , virtual control variable Zeta i and communication link reconstruction instruction set S r As input, the energy storage unit state of charge average value SOC ai and virtual control variable average value Zeta ai are obtained by iteration calculation through the consistency algorithm Step S5: average the state of charge of the energy storage unit SOC ai and the state of charge of the energy storage unit SOC i As an input quantity, the SOC equalization factor Δ m ki, where the SOC equalization factor Δ m ki is given by the expression: (1) In formula (1), z is the equalization dominant factor, Eta is the equalization regulation index, e () is an exponential function, C max is the maximum rated capacity of the energy storage unit, C bat is the rated capacity of the energy storage unit; wherein the expression of the dominant factor of equalization z is: (2) In formula (2), A is a balancing factor, sin() is a sine function, is a standard deviation of the state of charge of the energy storage unit, w is a process coefficient, i Li is an inductance current of the energy storage unit; wherein the process coefficients w are given by the expression: (3) In formula (3), Theta is an equalization acceleration factor, Mu is an equalization precision factor; Step S6: Convert the inductor current of the energy storage unit i Li DC bus voltage v bus and SOC equilibrium factor Δ m ki As input, after being processed by the current sharing control module, virtual control variables can be obtained. Zeta i Among them, virtual control variables Zeta i The expression is: (4) In formula (4), i Lmax is the maximum rated value of the inductance current of the energy storage unit, Q is the current equalization coefficient; Step S7: In the voltage recovery module, the virtual control variable average value Zeta ai is input, divided by the current sharing factor n i , to obtain the voltage balance amount v ai The DC bus voltage reference value v ref is subtracted by the voltage balance amount v ai , and then passes through a voltage recovery link PI controller G N (s) to obtain the voltage recovery adjustment amount v fi ; Step S8: in the voltage and current double closed loop module, the voltage recovery adjustment amount v fi as input, and add to the DC bus voltage reference value v ref , and subtract the energy storage unit output voltage v ci , the result is through a voltage outer loop PI controller G V (s) to get the current inner loop reference current i refi , the current inner loop reference current i refi is multiplied by the SOC equalization factor Δ m ki , the result is subtracted from the energy storage unit inductance current i Li , and then through a current inner loop PI controller G I (s), the result is through a limiting link, and the driving voltage is obtained v si , the driving voltage v si is further modulated PWM , and the output stable and reliable modulation signal is obtained d ti .

2. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 1, characterized in that, In step S2, the specific content of the energy storage unit fault positioning method is as follows: Step S2-1: Firstly, signal preprocessing is performed, that is, the SOC dp First-order low-pass filtering is performed to obtain the derivative of the filtered energy storage unit state of charge SOC dfp The expression is: (5) In formula (5), Tau is a filter time constant for suppressing misjudgment caused by high-frequency noise, T s is a sampling period, SOC dfsp is a derivative of the state of charge of the energy storage unit after filtering at the previous time, used for recursive operation; Step S2-2: setting a fault current threshold b , a state of charge derivative small threshold β When condition 1 or condition 2 in the fault determination expression is satisfied, it is determined that the pth energy storage unit is faulty, and at this time the fault positioning module outputs a fault positioning instruction L p = 1, otherwise, outputting a fault positioning instruction L p = 0, wherein the fault determination expression is: (6)。 3. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 1, characterized in that, In step S3, the specific content of the communication network repair control method is as follows: Step S3-1: First, real-time acquisition of each energy storage unit fault positioning instruction L p , the number of normal energy storage units in the system is counted , wherein, N is the total number of energy storage units, and the communication link reconstruction logic is formulated according to the number V normal of normal energy storage units in the system. Specifically, when the number V normal of normal energy storage units in the system is 4, the energy storage system operates normally, and the energy storage units communicate in a four-source ring structure; when the number V normal of normal energy storage units in the system is 3, the communication link connected with the faulty unit is disconnected, and the remaining three normal energy storage units are reconstructed into a three-source ring communication structure; when the number V normal of normal energy storage units in the system is 2, the communication link connected with the faulty unit is disconnected, and the remaining two normal energy storage units are reconstructed into a two-source straight-line communication structure; when the number V normal of normal energy storage units in the system is less than 2, the energy storage system triggers a protection mechanism and stops operating due to the inability to form an effective communication link. Step S3-2: According to the communication link reconstruction logic of step S3-1, output the communication link reconstruction instruction set S r ={ S ij , S jk , S kq , S qi | S ik , S jq} and directly act on the consistency algorithm, wherein S ij , S jk , S kq , S qi defined as the basic link instruction, respectively corresponding to the basic communication link between energy storage units i and j, j and k, k and q, q and i, S ik , S jq defined as the repair link instruction, respectively corresponding to the repair link between energy storage units i and k, j and q, and the on-off rule of the link instruction is: when S ag =1 indicates that the communication link between energy storage units a and g is in a closed state, S ag =0 indicates that the communication link between energy storage units a and g is in an open state, wherein a and g take values of i, j, k, q, and a is not equal to g.

4. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 1, characterized in that, In step S4, the expression of the consistency algorithm is: (7) In formula (7), Y ij is the average virtual state deviation of the i th energy storage unit and the j th energy storage unit after passing through the communication delay link, Y Rij is the average virtual state deviation of the i th and j th energy storage unit link updates, 1 / ( T t s +1) is a communication delay link, wherein T t is the communication delay between different energy storage units, s is a pull-type transformation complex variable operator, Y aj is the average virtual state variable of the i th energy storage unit in the four-source ring communication adjacent to the j th energy storage unit, Y iq is the average virtual state deviation of the i th energy storage unit and the q th energy storage unit after passing through the communication delay link, Y Riq is the average virtual state deviation of the i th and q th energy storage unit link updates, Y aq is the average virtual state variable of the i th energy storage unit in the four-source ring communication adjacent to the q th energy storage unit, Y ik is the average virtual state deviation of the i th energy storage unit and the j th energy storage unit after passing through the communication delay link, Y Rik is the average virtual state deviation of the i th and k th energy storage unit link updates, Y ak is the average virtual state variable of the i th energy storage unit in the four-source ring communication adjacent to the k th energy storage unit, Y i [ SOC i , Zeta i ] is the virtual state variable of the i th energy storage unit, Y ai [ SOC ai , Zeta ai ] is the average virtual state variable of the i th energy storage unit, h is a communication step coefficient; a communication link reconstruction instruction set S r The specific content acting on the consistency algorithm for updating is: When the number of normal energy storage units V normal = 4, the energy storage system is in normal operation, and the communication module receives a communication link reconstruction instruction set S r = 1, S ij = 1, S jk = 1, S kq = 1, S qi = 1, S ik = 0, S jq = 0}, the basic communication link of the energy storage unit is closed, and the energy storage unit forms a four-source ring communication according to the connection order of the node identifier i-j-k-q-i. At this time, the i th energy storage unit is connected and communicated with the adjacent j th and q th energy storage units, and the expression of the consistency algorithm of the i th energy storage unit is: (8) When the number of normal energy storage units V normal = 3, a single energy storage unit in the energy storage system fails, which can be mainly divided into two cases: case 1 is that the i-th energy storage unit fails in the k-th energy storage unit which is not adjacent in the four-source ring communication, at this time the communication link reconstruction instruction set S r S ij = 1, S jk = 1, S kq = 1, S qi = 1| S ik = 0, S jq = 0} is updated to { S ij = 1, S jk = 0, S kq = 0, S qi = 1| S ik = 0, S jq = 1} at this time, the basic communication link related to the k-th energy storage unit is disconnected, the repaired link between the j-th and q-th energy storage units is connected, and the remaining normal units reconstruct the three-source ring communication according to the connection order of the node identification i-j-q-i, at this time the i-th energy storage unit is still connected and communicated with the adjacent j-th and q-th energy storage units, and the consistency algorithm expression of the i-th energy storage unit is the same as formula (8).​ Case 2 is that the i-th energy storage unit is adjacent to the j-th or q-th energy storage unit in the four-source ring communication, at this time the communication link reconstruction instruction set S r from the system normal operation of { S ij =1, S jk =1, S kq =1, S qi =1| S ik =0, S jq =0} is updated to { S ij =0, S jk =0, S kq =1, S qi =1| S ik =1, S jq =0}(unit j failure) or { S ij =1, S jk =1, S kq =0, S qi =0| S ik =1, S jq =0}(unit q failure), at this time the basic communication link connected with the j-th or q-th energy storage unit is disconnected, the repair link between the i-th and k-th is connected, and the remaining normal units are reconstructed in the connection order of node identification i-k-q-i (unit j failure) or i-j-k-i (unit q failure) Three-source ring communication, at this time the consistency algorithm expression of the i-th energy storage unit is: (9) When the number of normal energy storage units V normal = 2, two energy storage units of the energy storage system fail, at this time the fault type can be divided into: energy storage unit simultaneous failure and energy storage unit periodical failure, wherein the energy storage unit simultaneous failure can be divided into two cases: case (1) is that the i-th energy storage unit and the j-th and q-th energy storage units adjacent to the i-th energy storage unit in the four-source ring communication all fail at the same time, at this time the communication link reconstruction instruction set S r By the normal operation of the system { S ij = 1, S jk = 1, S kq = 1, S qi = 1| S ik = 0, S jq = 0} is updated to { S ij = 0, S jk = 0, S kq = 0, S qi = 0| S ik = 1, S jq = 0} at this time, the basic communication link of the energy storage unit is disconnected, the repair link between the i-th and k-th energy storage units is connected, and the remaining normal units reconstruct two-source straight-line communication according to the connection order of node identification i-k-i, at this time, the consistency algorithm expression of the i-th energy storage unit is: (10) Case (2) is that the kth energy storage unit not adjacent to the ith energy storage unit in four-source ring communication fails simultaneously with either the jth or qth energy storage unit adjacent to the ith energy storage unit in four-source ring communication, at this time, the receiving communication link reconstruction instruction set S r from the system normal operation of { S ij = 1, S jk = 1, S kq = 1, S qi = 1 S ik = 0, S jq = 0} is updated to { S ij = 0, S jk = 0, S kq = 0, S qi = 1 S ik = 0, S jq = 0} (unit k and j fail) or { S ij = 1, S jk = 0, S kq = 0, S qi = 0 S ik = 0, S jq = 0} (unit k and q fail), at this time, the basic communication link of the kth and jth or qth energy storage unit fails, and the remaining normal units reconstruct two-source straight line communication according to the connection order of node identification i-q-i (unit k and j fail) or i-j-i (unit k and q fail), at this time, the consistency algorithm expression of the ith energy storage unit is: (11) The two energy storage units fault in different time periods refers to that after the first unit fails, the system resumes stable operation for a period of time, and then the second unit fails. In this process, the communication link reconstruction instruction set is updated twice S r and the consistency algorithm needs to be updated dynamically. The two energy storage units fault in different time periods can also be divided into three cases: case ① is that the kth energy storage unit not adjacent to the ith energy storage unit in the four-source ring communication fails first. At this stage, the update of the communication link reconstruction instruction set S r and the consistency algorithm of the ith unit are the same as case 1 in the single unit failure, and the remaining normal units reconstruct the three-source ring communication according to the connection order of node identification i-j-q-i. At this time, the system resumes stable operation based on the updated instruction set and algorithm, and runs for a period of time. Then, the jth or qth energy storage unit adjacent to the ith energy storage unit in the four-source ring communication fails again. At this stage, the communication link reconstruction instruction set S r is updated from { S ij =1, S jk =0, S kq =0, S qi =1| S ik =0, S jq =1} to { S ij =0, S jk =0, S kq =0, S qi =1| S ik =0, S jq =0}(unit j failure) or { S ij =1, S jk =0, S kq =0, S qi =0| S ik =0, S jq =0} (unit q failure), at this time, the base communication link connected with the jth or qth energy storage unit is disconnected, and the repair link between the jth and qth energy storage units is disconnected, the communication topology of the energy storage unit is reconstructed from the three-source ring communication of i-j-q-i to the two-source straight-line communication of i-q-i (unit j failure) or i-j-i (unit q failure), and the consistency algorithm of the ith energy storage unit is updated from formula (8) to formula (11); The initial stage of case 2 and case 3 is the same: the i-th energy storage unit fails first in the four-source ring communication, and the j-th or q-th energy storage unit adjacent to the i-th energy storage unit fails, and the communication link reconstruction instruction set in this stage S r The update case and the consistency algorithm of the i-th unit are consistent with the case 2 in the single unit failure described above, and the remaining normal units reconstruct the three-source ring communication according to the connection order of the node identifiers i-k-q-i (unit j failure) or i-j-k-i (unit q failure), at this time, the system resumes stable operation based on the updated instruction set and algorithm, and after a period of operation, the fault development of case 2 and case 3 appears differentiation, which is specifically manifested as follows: In case 2, the i-th energy storage unit fails again at the k-th energy storage unit which is not adjacent to the i-th energy storage unit in the four-source ring communication, at this stage, the communication link reconstruction instruction set is updated to S r by{ S ij = 0, S jk = 0, S kq = 1, S qi = 1| S ik = 1, S jq = 0}(unit j fails) or{ S ij = 1, S jk = 1, S kq = 0, S qi = 0| S ik = 1, S jq = 0}(unit q fails) to{ S ij = 0, S jk = 0, S kq = 0, S qi = 1| S ik = 0, S jq = 0}(unit j fails first, unit k fails later) or{ S ij = 1, S jk = 0, S kq = 0, S qi = 0| S ik = 0, S jq =0}(unit q fails first, unit k fails later), at this time, the basic communication link connected with the kth energy storage unit is disconnected, and the repair link between the ith and kth is disconnected, the communication topology of the energy storage unit is reconfigured from the three-source ring communication of i-k-q-i(unit j fails) or i-j-k-i(unit q fails) to the two-source straight-line communication of i-q-i(unit j fails first, unit k fails later) or i-j-i(unit q fails first, unit k fails later), and the consistency algorithm of the ith energy storage unit is updated from formula (8) to formula (9) and then from formula (9) to formula (11) during the whole operation of the system. In case 3, the i-th energy storage unit fails again in the adjacent one (q-th or j-th) in the four-source ring communication. At this stage, the communication link reconstruction instruction set S r by { S ij = 0, S jk = 0, S kq = 1, S qi = 1 S ik = 1, S jq = 0} (unit j fails first) or { S ij = 1, S jk = 1, S kq = 0, S qi = 0 S ik = 1, S jq = 0} (unit q fails first) is updated to { S ij = 0, S jk = 0, S kq = 0, S qi = 0 S ik = 1, S jq = 0} uniformly, at this time the basic communication link connected with the q-th or j-th energy storage unit is disconnected, the communication topology of the energy storage unit is uniformly reconstructed from the three-source ring communication of i-k-q-i (unit j fails first) or i-j-k-i (unit q fails first) to the two-source straight line communication of i-k-i, and the consistency algorithm of the i-th energy storage unit is first updated from equation (8) to equation (9), and then from equation (9) to equation (10) in the whole running process of the system. When the system is normal energy storage unit quantity V normal <2, the system cannot form an effective communication link, the energy storage system triggers the protection mechanism, and stops running.

5. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 1, characterized in that, In step S5, the value range of the equalization adjustment factor A is 0.3 A <0.9, the value range of the equalization acceleration factor Theta is 0.2 Theta <0.7, the value range of the equalization precision factor Mu is 0.0001 Mu <0.01, the value range of the equalization adjustment index Eta is 0.1 Eta <1.

6. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 1, characterized in that, In step S6, the current sharing coefficient Q has a value range of 10 Q <22.

7. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 2, characterized in that, In step S2-1, the filter time constant Tau has a value in the range of 0.1 Tau <1.5, the sampling period T s has a value in the range of 0.0001 T s <0.01; in step S2-2, the fault current threshold b has a value in the range of 0.01 b <0.1, the state of charge derivative small threshold β has a value in the range of 0.0001 β <0.

01.

8. The multi-scenario coordinated control method of distributed energy storage system based on fault location and dynamic communication restoration according to claim 4, characterized in that, Communication step size coefficient h The value range of a is 0 h <1, communication delay between different energy storage units T t The value range of a is 0.0001 T t <0.01.

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