Equivalent modeling method and system suitable for large-scale electrochemical energy storage power station

Abstract

The invention discloses an equivalent modeling method and system suitable for a large-scale electrochemical energy storage power station, and relates to the technical field of energy storage power station modeling, and the method comprises the steps: obtaining the data of an electrochemical energy storage power station, and constructing a basic circuit topological structure; building a mathematical model according to the control strategy; basic parameters of the equivalent model are calculated through the generalized Hamilton action quantity. According to the method, coherent equivalence and generalized Hamilton action quantity are combined with an electrochemical energy storage power station mathematical model, and an equivalent model which is the same as a detailed model topology is established. The equivalent model and the detailed model have the same circuit topology structure, so that the grid-connected characteristic and the dynamic response of the equivalent model can be ensured to be consistent with the detailed model after the circuit parameters are converted according to the coherent equivalent mode. And after the parameters are subjected to equivalent calculation, the order of the electrochemical energy storage power station is reduced, the modeling workload is reduced, the simulation analysis time is shortened, and the stability analysis efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage power station modeling, and particularly to an equivalent modeling method and system suitable for large-scale electrochemical energy storage power stations. Background Art

[0002] The instability of renewable energy output poses a huge challenge to the safe and reliable operation of power systems, severely restricting the consumption and utilization of large-scale new energy. The development of energy storage technology provides an effective solution for the large-scale grid connection of renewable energy, ensuring the safe and stable operation of power systems. Among them, electrochemical energy storage has received extensive attention due to its high energy density, fast response speed, good flexibility, strong scalability, etc., and can play an important role in scenarios such as suppressing the fluctuations of renewable energy, peak shaving and valley filling, frequency modulation and voltage regulation, and improving power quality. However, when studying the control strategy and grid connection stability between electrochemical energy storage power stations and new energy power stations, establishing a detailed simulation model requires a huge amount of calculation, and the time and effort consumed by the simulation are unbearable. Currently, there is a lack of an equivalent model for electrochemical energy storage power stations with high accuracy and less simulation time. Under this background, the present invention creates an equivalent modeling method suitable for large-scale electrochemical energy storage power stations. Through this method, a simulation model of an electrochemical energy storage power station suitable for electromagnetic transient simulation can be established.

[0003] The patent "An Electromagnetic Transient Simulation Modeling Method for Electrochemical Energy Storage Power Stations" discloses an electromagnetic transient simulation modeling method and system for electrochemical energy storage power stations. By obtaining the basic data of the electrochemical energy storage power station and the near area of the connected power grid, a typical electromagnetic transient simulation data model of the electrochemical energy storage power station and the near area of the connected power grid is established. However, when it comes to an unbuilt or unoperated energy storage power station, it is difficult to obtain its basic operation data and the situation of the near area of the connected power grid is unknown, resulting in low modeling accuracy. The patent "Converter Electromechanical Simulation Modeling Method, System and Medium for Electrochemical Energy Storage Power Stations" discloses a converter electromechanical simulation modeling method, system and medium for electrochemical energy storage power stations. According to the converter electromechanical simulation model, the parameters to be optimized are determined, and then the overshoot, response time and regulation time under different parameters are used as fitness functions. The particle swarm optimization algorithm is used for iterative optimization and the particle with the minimum fitness is taken as the optimal output. However, the influence of the battery pack model and the bidirectional DC-DC converter in the electrochemical energy storage power station on the overall grid connection characteristics is ignored. The patent "A Modeling Method and System for Electrochemical Energy Storage Power Stations Suitable for Large Power Grid Dynamic Simulation" discloses a modeling method and system for electrochemical energy storage power stations suitable for large power grid dynamic simulation. By collecting the grid frequency, the active power output by the electrochemical energy storage power station, the grid tie line power value and the grid-side machine terminal voltage equivalent value, a frequency support model, a secondary frequency modulation model, a power control model, a battery pack model, a battery limit model and a grid connection interface model of the electrochemical energy storage power station are established respectively. The simulation accuracy of this model is relatively high, but the model order is relatively high and the simulation time is long, which is not suitable for the grid connection stability analysis of electrochemical energy storage power stations and new energy power stations. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed.

[0005] Therefore, the technical problem to be solved by the present invention is: how to maintain a relatively high accuracy and less simulation time during the modeling process of electrochemical energy storage power stations.

[0006] To solve the above technical problem, the present invention provides the following technical solution: An equivalent modeling method suitable for large-scale electrochemical energy storage power stations, including: obtaining the data of the electrochemical energy storage power station and constructing a basic circuit topology; building a mathematical model according to the control strategy; using the generalized Hamilton action to calculate the basic parameters of the equivalent model.

[0007] As a preferred embodiment of the equivalent modeling method suitable for large-scale electrochemical energy storage power stations of the present invention, wherein: the mathematical model includes a storage battery pack model, a BDC model, a PCS model, and the current limiting strategy, fault ride-through control strategy, and battery overcharge and over-discharge protection control strategy of the control model.

[0008] As a preferred solution of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations according to the present invention, wherein: the no-load voltage E of the energy storage battery pack model bat and the port voltage U bat are respectively:

[0009]

[0010] U bat = E bat - R bat I bat

[0011] wherein, E 0 is the battery constant voltage; K is the polarization voltage; C is the battery capacity; ∫idt is the electric quantity absorbed or emitted by the battery; B is a parameter determining the charge and discharge characteristics of the battery; SOC is the ratio of the remaining electric quantity of the storage battery to the rated electric quantity, and the estimation expression of the SOC value S is:

[0012]

[0013] Combined with the above formula, the expression of the no-load voltage E bat is rewritten as a non-linear equation expressed by the actual SOC of the battery:

[0014]

[0015] As a preferred solution of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations according to the present invention, wherein: the BDC model adopts a double closed-loop control strategy, the inner loop is the battery-side current control, and the outer loop is the constant power control. The duty ratio of the thyristor switch is generated according to the difference between the battery output power and its set command value: the outer loop controller outputs the input current reference value of the inner loop controller, so as to respond to the change of the battery-side output current;

[0016] The outer loop control transfer function of the PCS model is expressed as:

[0017]

[0018] wherein, k pdc and k idc are respectively the outer loop proportional and integral coefficients in the constant DC voltage control mode; k pQ and k iQ are respectively the outer loop proportional and integral coefficients in the constant reactive power control mode;

[0019] The current inner loop outputs the dq-axis voltage reference signal of the converter based on the feedforward decoupling method of the PI link, and then generates the pulse signal for controlling the switch of the power electronic device through pulse width modulation:

[0020]

[0021] Among them, are the positive-sequence voltage reference values of the d-axis and q-axis in the inner-loop controller; k pd , k id are the proportional regulation coefficient and integral regulation coefficient of the d-axis current inner loop respectively; k pg , k iq are the proportional regulation coefficient and integral regulation coefficient of the q-axis current inner loop respectively; u sd , u sq are disturbance variables; ω 1 is the synchronous angular velocity; L is the equivalent filter inductor on the AC side.

[0022] As a preferred scheme of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations described in the present invention, wherein: the current limiting strategy is to generate active and reactive current command values for the power outer-loop control, and give priority to ensuring output, and then determine the maximum value of the q-axis component of the positive-sequence current:

[0023]

[0024] Among them, is the maximum allowable output value of the d-axis component of the positive-sequence current, is the maximum allowable output value of the q-axis component of the positive-sequence current, I max is the maximum allowable output current of the PCS;

[0025] The fault ride-through control strategy is that when the fault occurs and causes the voltage change at the grid connection point, the current inner-loop reference value is directly given in segments according to the depth of voltage dip:

[0026]

[0027] Among them, k is a constant coefficient greater than 1.5, U+pcc is the per-unit value of the positive-sequence voltage at the grid connection point, and U+pccn is the per-unit value of the positive-sequence voltage at the grid connection point under the rated operating state;

[0028] The battery overcharge and over-discharge protection control strategy is to limit the operating range of the battery SOC during the charge and discharge process of the energy storage power station. When it exceeds the operating range, the battery management system locks the battery and no longer conducts charge and discharge.

[0029] As a preferred scheme of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations described in the present invention, wherein: the generalized Hamilton action includes that within any time period, the change amount of the generalized Hamilton action of two systems is always a constant, then the two systems are strictly homologous:

[0030]

[0031] Among them, is the generalized Hamiltonian action. The subscripts 1 and 2 are used to distinguish any two homology systems, k is a constant, and ε is the homology tolerance margin;

[0032] Using the generalized Hamiltonian action, a simplified criterion for the grid-connected converter system to satisfy the homology characteristics is derived: when under external small disturbance conditions, the maximum change rate of the inverter line current is less than the given homology tolerance margin ε, which can be expressed by the following formula:

[0033]

[0034] Among them, i line represents the line current at the grid connection point.

[0035] As a preferred solution of the equivalent modeling method for large-scale electrochemical energy storage power stations described in the present invention, among them: for non-conservative systems, its generalized Hamiltonian action is used to measure the internal energy exchange of the system and the energy exchange between the system and the outside, and is expressed as:

[0036]

[0037] Among them, T is the magnetic field energy in the electrochemical energy storage power station, V is the electric field energy, T is mainly composed of the energy stored in the inductance in the system, and V is mainly the energy stored in the capacitor in the electrochemical energy storage power station. The expression is:

[0038]

[0039] Among them, L is the BDC inductor, L f and L t are the LCL filter inductors, C bat is the battery pack capacitor, C dc is the BDC AC side capacitor, C f is the LCL filter capacitor, U is the generalized potential energy, which is mainly composed of the DC injection energy of the electrochemical energy storage power station, the AC output energy and the energy dissipated by the resistance in the system, and is expressed as:

[0040] U = ∫(i bat v bat +R c (i f -i t ) 2 +V pcc i t )dt

[0041] Among them, R c is the passive damping resistor connected in parallel with the filter capacitor.

[0042] In a second aspect, another object of the present invention is to provide an equivalent modeling system applicable to large-scale electrochemical energy storage power stations, including: a data acquisition module, a mathematical model construction module, a control strategy generation module, and a generalized Hamilton action calculation module; the data acquisition module is used to obtain electrochemical energy storage power station data and construct a basic circuit topology; the mathematical model construction is used to construct a storage battery pack model, a BDC model, and a PCS model; the control strategy generation module is used to generate a current limiting strategy, a fault ride-through control strategy, and a battery overcharge and over-discharge protection control strategy; the generalized Hamilton action calculation module is used to calculate the basic parameters of the equivalent model.

[0043] In a third aspect, a computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations as described above are implemented.

[0044] In a fourth aspect, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the equivalent modeling method applicable to large-scale electrochemical energy storage power stations as described above are implemented.

[0045] Advantages of the present invention: The equivalent modeling method and system applicable to large-scale electrochemical energy storage power stations of the present invention combine co-simulation equivalence and generalized Hamilton action with the mathematical model of electrochemical energy storage power stations to establish an equivalent model with the same topology as the detailed model. Since the equivalent model and the detailed model have the same circuit topology, after the circuit parameters are converted according to the co-simulation equivalence method, it can be ensured that the grid connection characteristics and dynamic responses of the equivalent model are consistent with those of the detailed model. And after the parameter equivalence calculation, the order of the electrochemical energy storage power station is reduced, the modeling workload is reduced, the simulation analysis time is reduced, and the efficiency of stability analysis is improved. Description of the Drawings

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0047] Figure 1 It is the overall flowchart of an equivalent modeling method applicable to large-scale electrochemical energy storage power stations provided by an embodiment of the present invention;

[0048] Figure 2 It is the structure diagram of an electrochemical energy storage power station of an equivalent modeling method applicable to large-scale electrochemical energy storage power stations provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0051] Example 1

[0052] Reference Figure 1 - Figure 2 , which is an embodiment of the present invention, provides an equivalent modeling method applicable to a large-scale electrochemical energy storage power station, comprising:

[0053] S1: Obtain electrochemical energy storage power station data and build basic circuit topology;

[0054] Furthermore, the typical grid-connected system structure of an electrochemical energy storage power station is as follows: Figure 2 As shown. The grid-connected system consists of a battery pack, a bidirectional DC-DC converter (BDC), a power converter system (PCS) and an LCL filter, and is connected to the grid through an isolation transformer. The battery pack consists of a large number of single cells connected in series and parallel, connected to the DC bus through the BDC, and then connected to the AC grid through the PCS and AC filter circuit.

[0055] S2: Build a mathematical model based on the control strategy;

[0056] Furthermore, the energy storage battery pack model: Generally, the battery pack can be simplified into an equivalent model of a single cell. The commonly used equivalent circuit model of a single cell is the Shepherd model, which is easy to build and analyze, and can accurately simulate the external characteristics of a variety of electrochemical batteries and reflect the SOC of the battery. The no-load voltage E of the energy storage battery pack model of the Shepherd model bat , port voltage U bat They are:

[0057]

[0058] Ubat = E bat - R bat I bat

[0059] Where: E 0 is the constant voltage of the battery; K is the polarization voltage; C is the battery capacity; ∫idt is the amount of electricity absorbed / emitted by the battery; A and B are parameters that determine the charge and discharge characteristics of the battery. SOC is a key parameter of the energy storage power station, which can quantify the remaining energy inside the current battery. Numerically, it is defined as the ratio of the remaining battery charge to the rated charge. The estimation expression of the SOC value S is:

[0060]

[0061] Therefore, the expression of the no-load voltage Ebat can be rewritten as a non-linear equation expressed by the actual SOC of the battery:

[0062]

[0063] BDC model: BDC maintains the power balance and voltage stability at both ends by controlling the charge / discharge mode of the battery pack, and adopts a double closed-loop control strategy. Among them, the inner loop is the battery-side current control, and the outer loop is the constant power control. Specifically, as Figure 1 shown. BDC determines the charge / discharge state of the energy storage power station according to the active power command value (positive value for discharge and negative value for charge), and uses a cascaded proportional-integral (PI) controller to generate the duty cycle of the thyristor switch according to the difference between the battery output power and its set command value: the outer loop controller outputs the input current reference value of the inner loop controller, so as to respond to the change of the battery-side output current, further optimize the system, and improve the dynamic power response ability of BDC. At the same time, to avoid the influence of high current on BDC and the battery pack, the duty cycle of the converter is limited according to the maximum allowable current Ib,max.

[0064] It should be noted that when it is detected that the SOC is lower than Smin or higher than Smax, where Smin and Smax are the lower and upper limit values of the SOC respectively, BDC keeps S1 and S2 always in the off state, that is, the battery pack is locked. At the same time, the power command value is set to 0, and the battery stops discharging or charging to prevent damage to the battery caused by overcharge / overdischarge.

[0065] Furthermore, for the PCS model: The control strategy during the normal operation of the energy storage power station is divided into two parts: outer-loop power control and inner-loop current control. The outer-loop control can independently adjust the active and reactive powers of the energy storage power station, mainly divided into active power control and reactive power control. Compared with the fixed active power control, the fixed DC voltage control can track the change of active power more quickly, enabling the control system to instantaneously change the output of the d-axis component of the current. Therefore, the active power control method takes the fixed DC voltage control as an example. At the same time, to ensure that the reactive power of the converter in AC with the power grid is controllable, thus providing sufficient margin for active power control, the reactive power control method in this paper takes the fixed reactive power as an example. The transfer function of the outer-loop control is as shown in the formula:

[0066]

[0067] In the formula: k pdc 、k idc are the outer-loop proportional and integral coefficients respectively under the fixed DC voltage control method; k pQ 、k iQ are the outer-loop proportional and integral coefficients respectively under the fixed reactive power control method.

[0068] It should be noted that the current inner loop is based on the feedforward decoupling method of the PI link, which can quickly respond to the outer-loop control parameters, realize the independent control of the dq-axis current, and output the reference signals of the dq-axis voltages of the converter. Then, through pulse width modulation (PWM), the pulse signals for controlling the on / off of power electronic devices are generated.

[0069]

[0070] In the formula: are the reference values of the positive-sequence voltages of the d and q axes in the inner-loop controller respectively; k pd 、k id are the proportional regulation coefficient and integral regulation coefficient of the d-axis current inner loop respectively; k pg 、k iq are the proportional regulation coefficient and integral regulation coefficient of the q-axis current inner loop respectively; u sd 、u sq are disturbance variables; ω1 is the synchronous angular velocity; L is the equivalent filtering inductance on the AC side.

[0071] Furthermore, the current limiting strategy: To avoid overloading the PCS input / output and prevent damage to power electronic devices due to overcurrent, it is necessary to limit the active and reactive current command values generated by the power outer loop control. When the generated current command value does not reach the limit value, the energy storage power station responds to the actual current command; when the command value exceeds the limit value, the actual current magnitude will respond according to the limit value. In actual engineering, the energy storage power station mostly transmits active power during normal grid-connected operation. Therefore, the PCS generally adopts a control measure with active power control as the main and reactive power control as the auxiliary, and the current limiting strategy also adopts an active power priority current limiting strategy, that is, to ensure the output of first, and then determine the maximum value of the q-axis component of the positive-sequence current:

[0072]

[0073] In the formula: is the maximum allowable output value of the d-axis component of the positive-sequence current; is the maximum allowable output value of the q-axis component of the positive-sequence current; I max is the maximum allowable output current of the PCS.

[0074] Furthermore, the fault ride-through control strategy: When a grid fault occurs, the grid-connected operation control strategy under normal conditions is no longer applicable, and the control strategy during the fault ride-through period plays a dominant role. The electrochemical energy storage system should have a certain high and low voltage ride-through ability after being grid-connected.

[0075] It should be noted that during the fault ride-through period, the energy storage power station can still independently control the active and reactive power. During the fault, the system voltage drops, and usually, the reactive power is controlled first to provide support for the system voltage. The PCS controls the magnitude of the reactive power by controlling the q-axis component of the current. Therefore, during the fault, by adjusting the reference value of the q-axis component of the positive-sequence current according to the voltage drop or rise degree at the grid connection point of the energy storage power station, the reactive power transmitted by the PCS can be controlled. When the grid connection point voltage changes due to a fault, the reference value i+qrefDT of the current inner loop is directly given in segments according to the voltage drop depth:

[0076]

[0077] In the formula: k is a constant coefficient greater than 1.5; is the per-unit value of the positive-sequence voltage at the grid connection point; is the per-unit value of the positive-sequence voltage at the grid connection point under the rated operating state.

[0078] It should be noted that according to the fault ride-through strategy, the energy storage power station preferentially transmits reactive power to support the system voltage during the fault. At this time, the PCS changes to adopt a current limiting strategy with reactive power as the main and active power as the auxiliary, and the active current will be limited by the PCS capacity.

[0079]

[0080] Furthermore, the battery overcharge / overdischarge protection control strategy: During the charge / discharge process of the energy storage power station, the state of charge (SOC) of the battery also changes accordingly. When the battery is fully discharged or charged, if continued discharge or charge is carried out, it may cause the voltage to be too low or too high, thereby affecting the battery life and even leading to serious consequences such as thermal runaway and battery explosion. Therefore, in actual engineering, the operating range of the battery SOC is generally limited, such as S ∈ [10%, 90%]. When exceeding this range, the battery management system locks the battery. For example, it shuts down the power conversion system (PCS), disconnects from the power grid, or sets the power command value in the battery disconnect controller (BDC) to 0 and no longer conducts charge and discharge. In the present invention, the situation where the SOC exceeds this range is defined as the energy storage power station being in an overcharge / overdischarge state.

[0081] S3: Calculate the basic parameters of the equivalent model using the generalized Hamilton action;

[0082] Furthermore, the aggregation equivalent method based on the homology criterion obtains the quantitative relationship satisfied between the state variables of the two homologous systems by establishing the mathematical relationship between the two homologous systems, and then the detailed equivalent parameters of the aggregation model can be further deduced.

[0083] It should be noted that only when different subunits in a large-scale system satisfy the homology criterion can the dynamic consistency be guaranteed after aggregation. Therefore, the aggregation method proposed in the present invention aims to provide a method for calculating the aggregation equivalent parameters for multiple parallel energy storage units in a large-scale electrochemical energy storage power station with homology and satisfying the homology criterion. Using the generalized Hamilton action, the basic condition for whether two systems satisfy homology can be obtained: within any time period [t0, t + 0], if the change amount of the generalized Hamilton action of the two systems is always a constant, then the two systems are strictly homologous:

[0084]

[0085] In the formula is the generalized Hamilton action, the subscripts 1 and 2 are used to distinguish any two homologous systems, k is a constant, and ε is the homology tolerance margin, generally less than 1.

[0086] Similarly, using the generalized Hamilton action, a simplified criterion for the grid-connected converter system to satisfy the homology characteristic is deduced: when under external small disturbance conditions (symmetrical or asymmetrical grid faults), the maximum change rate of the inverter line current is less than the given homology tolerance margin ε, which can be expressed by the following formula:

[0087]

[0088] In the formula, i line represents the line current at the grid connection point.

[0089] The generalized Hamiltonian action actually reflects the energy exchange relationship of the system. For a photovoltaic grid-connected power generation system, there are energy input and output as well as energy dissipation. There is energy exchange between the electrochemical energy storage power station and the power grid, so the electrochemical energy storage power station is a non-conservative system. For a non-conservative system, its generalized Hamiltonian action is used to measure the internal energy exchange of the system and the energy exchange between the system and the outside, and can be defined as follows:

[0090]

[0091] In the formula, T is the magnetic field energy in the electrochemical energy storage power station, and V is the electric field energy. T is mainly composed of the energy stored in the inductor in the system, and V is mainly the energy stored in the capacitor in the electrochemical energy storage power station. Therefore, its expression is:

[0092]

[0093] In the formula, L is the BDC inductor, L f and L t are the LCL filter inductors, C bat is the battery pack capacitor, C dc is the BDC AC side capacitor, C f is the LCL filter capacitor. And U is the generalized potential energy, which is mainly composed of the DC injection energy of the electrochemical energy storage power station, the AC output energy and the energy dissipated by the resistance in the system. It can be expressed as:

[0094] U = ∫(i bat v bat +R c (i f -i t ) 2 +v pcc i t )dt

[0095] In the formula, R c is the passive damping resistor in parallel with the filter capacitor.

[0096] When two systems satisfy the homology criterion, their corresponding generalized Hamiltonian actions will also satisfy a certain proportional relationship. In view of the fact that the Hamiltonian action actually reflects the relationship between the energies of the two systems, their energy relationship will also be proportional. It can be known that the following relationship formula is satisfied for two homologous systems:

[0097]

[0098] E is the total energy of the electrochemical energy storage power station. According to the law of conservation of energy, it can be split into:

[0099]

[0100] When the above energy relationship is satisfied, the state variables between two homologous electrochemical energy storage power stations satisfy the following relationship:

[0101]

[0102] In the formula, k L is another constant.

[0103] Therefore, since each energy storage unit in the electrochemical energy storage power station satisfies the homology condition and the homology remains unchanged after the system is aggregated and equivalent, it can be deduced that the above proportional relationship is also satisfied between the state variables of the detailed model and the aggregated model.

[0104] Embodiment 2

[0105] Referring to Figure 2 , an embodiment of the present invention provides an equivalent modeling system applicable to a large-scale electrochemical energy storage power station, including: a data acquisition module, a mathematical model construction module, a control strategy generation module, and a generalized Hamilton action calculation module; the data acquisition module is used to obtain electrochemical energy storage power station data and construct a basic circuit topology; the mathematical model construction is used to construct an energy storage battery pack model, a BDC model, and a PCS model; the control strategy generation module is used to generate a current limiting strategy, a fault ride-through control strategy, and a battery overcharge and over-discharge protection control strategy; the generalized Hamilton action calculation module is used to calculate the basic parameters of the equivalent model.

[0106] Embodiment 3

[0107] An embodiment of the present invention, which is different from the previous two embodiments, is that:

[0108] If the above functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. And the aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0110] More specific examples (non-exhaustive list) of computer-readable media include the following: electrical connection parts (electronic devices) having one or more wirings, portable computer disk cartridges (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber devices, and portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other suitable processing as necessary, and then stored in a computer memory.

[0111] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having suitable combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0112] Embodiment 4

[0113] An embodiment of the present invention provides an equivalent modeling method applicable to large-scale electrochemical energy storage power stations. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0114] Use MATLAB / Simulink or other power system simulation tools to build an equivalent model. The relevant parameters collected in the experiment are shown in Table 1:

[0115] Table 1: Model Parameter Setting Table

[0116]

[0117] Table 2: Comparison Table of Experimental Conditions and Results

[0118]

[0119] Through the data table, the dynamic performance differences between the equivalent model and the detailed model can be clearly compared, and the balance between the improvement of modeling efficiency and the maintenance of accuracy of the proposed method can be verified.

[0120] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An equivalent modeling method suitable for large-scale electrochemical energy storage power stations, characterized in that: include: Obtain electrochemical energy storage power station data and build basic circuit topology; Build mathematical models based on control strategies; The basic parameters of the equivalent model are calculated using the generalized Hamiltonian action.

2. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 1, characterized in that: The mathematical model includes an energy storage battery pack model, a BDC model, a PCS model, and a current limiting strategy, a fault ride-through control strategy, and a battery overcharge and over-discharge protection control strategy of the control model.

3. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 1, characterized in that: The no-load voltage E of the energy storage battery model bat , port voltage U bat They are: U bat =E bat -R bat I bat Among them, E0 is the constant voltage of the battery; K is the polarization voltage; C is the battery capacity; ∫idt is the amount of electricity absorbed or emitted by the battery; B is the parameter that determines the charging and discharging characteristics of the battery; SOC is the ratio of the remaining power of the battery to the rated power. The estimation formula of SOC value S is: Combined with the above formula, the no-load voltage E bat The expression is rewritten into a nonlinear equation represented by the actual SOC of the battery:

4. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 3, characterized in that: The BDC model adopts a dual closed-loop control strategy, with the inner loop being battery-side current control and the outer loop being constant power control, generating the duty cycle of the thyristor switch according to the difference between the battery output power and its set command value: the outer loop controller outputs the input current reference value of the inner loop controller, thereby responding to changes in the battery-side output current; The outer loop control transfer function of the PCS model is expressed as: Among them, k pdc , k idc They are the outer loop proportional and integral coefficients under the constant DC voltage control mode; k pQ , k iQ They are the outer loop proportional and integral coefficients under the constant reactive power control mode; The current inner loop outputs the converter dq axis voltage reference signal based on the feedforward decoupling method of the PI link, and then generates a pulse signal for controlling the switch of the power electronic device through pulse width modulation: in, are the positive sequence voltage reference values ​​of d and q axes in the inner loop controller respectively; k pd , k id are the proportional regulation coefficient and integral regulation coefficient of the inner loop of the d-axis current respectively; k pg , k iq are the inner loop proportional adjustment coefficient of q-axis current and the only adjustment coefficient; u sd 、u sq is the disturbance variable; ω1 is the synchronous angular velocity; L is the equivalent filter inductance on the AC side.

5. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 4, characterized in that: The current limiting strategy is to generate active and reactive current command values ​​for the power outer loop control, giving priority to ensuring The output of , and then determine the maximum value of the positive sequence current q-axis component: in, is the maximum value allowed for the output of the d-axis component of the positive sequence current, is the maximum value allowed for the output of the q-axis component of the positive sequence current, I max The maximum allowed output current of PCS; The fault ride-through control strategy is that when a fault occurs and the grid voltage changes, the current inner loop reference value According to the voltage drop depth, it is directly given in sections: Where k is a constant coefficient greater than 1.5, is the per unit value of the positive sequence voltage at the grid connection point, It is the per unit value of the positive sequence voltage at the grid connection point under rated operating conditions; The battery overcharge and over-discharge protection control strategy is to limit the operating range of the battery SOC during the charging and discharging process of the energy storage power station. When the operating range is exceeded, the battery management system locks the battery and no longer charges or discharges.

6. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 5, characterized in that: The generalized Hamiltonian action includes that the change of the generalized Hamiltonian action of the two systems is always constant in any time period, and the two systems are strictly homologous: in, is the generalized Hamiltonian action, subscripts 1 and 2 are used to distinguish any two homology systems, k is a constant, and ε is the homology tolerance margin; By using the generalized Hamiltonian action, a simplified criterion for the grid-connected converter system to meet the synchronization characteristics is derived: when under the condition of small external disturbance, the maximum change rate of the inverter line current is less than the given synchronization tolerance margin ε, which can be expressed by the following formula: Among them, i line Represents the grid-connected line current.

7. The equivalent modeling method applicable to a large-scale electrochemical energy storage power station according to claim 6, characterized in that: For a non-conservative system, its generalized Hamiltonian action is used to measure the internal energy exchange of the system and the energy exchange between the system and the outside world, expressed as: Among them, T is the magnetic field energy in the electrochemical energy storage power station, V is the electric field energy, T is mainly composed of the inductor storage energy in the system, and V is mainly the energy stored in the capacitor in the electrochemical energy storage power station. The expression is: Where, L is the BDC inductance, L f and L t is the LCL filter inductor, C bat is the battery pack capacitance, C dc is the BDC AC side capacitance, C f is the LCL filter capacitor, U is the generalized potential energy, which is mainly composed of the DC injection energy of the electrochemical energy storage power station, the AC output energy and the energy dissipated by the resistance in the system, expressed as: U=∫(i bat v bat +R c (i f -i t ) 2 +v pcc and t )dt Among them, R c It is a passive damping resistor in parallel with the filter capacitor.

8. A system using the equivalent modeling method for large-scale electrochemical energy storage power stations as claimed in any one of claims 1 to 7, characterized in that: include: Data acquisition module, mathematical model building module, control strategy generation module and generalized Hamiltonian action calculation module; The data acquisition module is used to obtain electrochemical energy storage power station data and construct a basic circuit topology structure; The mathematical model is used to construct an energy storage battery pack model, a BDC model, and a PCS model; The control strategy generation module is used to generate a current limiting strategy, a fault ride-through control strategy, and a battery overcharge and over-discharge protection control strategy; The generalized Hamiltonian action calculation module is used to calculate the basic parameters of the equivalent model.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the equivalent modeling method applicable to a large-scale electrochemical energy storage power station described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the equivalent modeling method applicable to a large-scale electrochemical energy storage power station described in any one of claims 1 to 7 are implemented.

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