A general electromechanical transient modeling method and system for simulating multiple types of energy storage

Abstract

This invention relates to the field of new energy grid connection technology, and provides a general electromechanical transient modeling method and system for simulating multiple types of energy storage. The method includes: structural identification of doubly-fed variable-speed pumped hydro storage and electrochemical energy storage, both decomposed into multiple sub-models according to function; for each sub-model, analyzing the similarities and differences between doubly-fed variable-speed pumped hydro storage and electrochemical energy storage in energy transfer, control strategies, and grid connection characteristics, and establishing a general electromechanical transient model including an energy buffer model, a primary energy side model, a secondary energy side model, and a reference value generation model. This invention proposes a general electromechanical transient model structure capable of simulating the dynamic characteristics of various energy storage systems, which not only facilitates the flexible use of models in large-scale power system simulations but also reduces the burden of program development.

Description

Technical Field

[0001] This invention belongs to the field of electromechanical transient modeling and development of energy storage equipment, and particularly relates to a general electromechanical transient modeling method and system for simulating multiple types of energy storage. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] As the scale of new energy grid connection continues to expand, the demand for energy storage resources in the power system is becoming increasingly urgent. Pumped hydro storage and electrochemical energy storage are currently the two most widely used energy storage technologies. Doubly fed variable speed pumped storage: Compared with traditional fixed speed units, it adjusts the rotor frequency through a converter, realizing flexible adjustment of the speed within a certain range, thereby expanding the operating head range and enabling rapid and accurate power response. Electrochemical energy storage, represented by lithium batteries, has significant advantages such as high energy density, fast response speed and flexible configuration, and plays a key role in smoothing up new energy fluctuations, regulating frequency and voltage, and peak shaving and valley filling.

[0004] However, existing technical solutions have the following problems when performing electromechanical transient simulation modeling of power systems: The models are highly differentiated, resulting in a heavy development burden: Although the two types of energy storage are similar in function, they are different in physical structure (one is a mechanical rotating system and the other is a static electrochemical system). Traditional simulation software usually builds separate model libraries for the two, and developers need to maintain multiple sets of complex mathematical equations and control logic for different devices, which increases the redundancy of program development and the difficulty of maintenance. Inconsistent simulation interfaces and poor flexibility: When conducting large-scale power system simulations, different types of energy storage devices often have different input / output interfaces and parameter systems. This means that when simulation modelers adjust the system scheme (such as replacing pumped storage at a certain node with electrochemical energy storage), they must rebuild the entire simulation module, making it difficult to achieve rapid model switching and flexible calling. Lack of in-depth exploration of the commonalities of energy transfer: Although the physical implementations are different, from the perspective of control and energy conversion, both types of energy storage contain a topology of "energy source - buffer link - grid connection interface". Existing technologies often focus on the detailed modeling of individual devices, ignoring the common characteristics of the two at the electromechanical transient scale, which makes it impossible to describe their dynamic characteristics through a unified mathematical framework.

[0005] Therefore, there is currently a lack of a general electromechanical transient model that can simultaneously take into account the characteristics of doubly-fed variable-speed pumped storage and electrochemical energy storage, has a universal structure, and is easy to implement in programs. This has become a key issue restricting the improvement of power system simulation efficiency and the reduction of development costs. Summary of the Invention

[0006] To address the technical problems mentioned above, this invention provides a general electromechanical transient modeling method and system for simulating multiple types of energy storage. It identifies the structures of two typical energy storage models, decomposes them into multiple sub-models according to their functions, and analyzes the similarities and differences between the two types of energy storage in terms of energy transfer, control strategies, and grid connection characteristics for each sub-model. It establishes energy buffer models, primary energy side models, secondary energy side models, energy state models, and reference value generation models, respectively. This method can simultaneously simulate the energy transfer and grid connection characteristics of doubly-fed variable-speed pumped hydro storage and electrochemical energy storage, which not only facilitates the flexible use of models in large-scale power system simulations but also reduces the burden of program development.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a general electromechanical transient modeling method for simulating various types of energy storage, comprising: Structural identification was performed on both doubly-fed variable-speed pumped storage and electrochemical energy storage, and both were decomposed into multiple sub-models according to their functions. For each type of sub-model, the similarities and differences between doubly-fed variable-speed pumped storage and electrochemical energy storage in terms of energy transfer, control strategies and grid connection characteristics are analyzed, and a general electromechanical transient model including an energy buffer model, a primary energy side model, a secondary energy side model and a reference value generation model is established. The reference value generation model transmits corresponding reference values ​​to the primary energy model and the secondary energy model according to the control mode. The primary energy model generates the primary output power based on the received reference values ​​and inputs it into the energy buffer model. The energy buffer model changes the state variables under the combined action of the primary output power and the electromagnetic power, and transmits them to the secondary energy model. The secondary energy model generates the current injected into the network based on the received reference values, combined with the state variables or the electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

[0008] Furthermore, when the primary energy side model determines the primary output power control and the secondary energy side model determines the state variable control: The reference value generation model transmits the active power reference value to the primary energy side model and the state reference value to the secondary energy side model according to the control mode. The primary energy model generates the primary output power based on the active power reference value and inputs it into the energy buffer model. The energy buffer model changes its state variables under the influence of primary-side output power and electromagnetic power, and transmits these changes to the energy secondary-side model. The energy secondary side model generates the current injected into the network based on the state reference value and state variables, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

[0009] Furthermore, when the primary energy model uses constant state quantity control, the secondary energy model should be set to constant electromagnetic power control: The reference value generation model transmits the state reference value to the primary energy side model and the active power reference value to the secondary energy side model according to the control mode. The primary energy model generates the primary output power based on the state reference value and passes it to the energy buffer model; The energy buffer model changes its state variables under the influence of primary-side output power and electromagnetic power, and transmits these changes to the energy secondary-side model. The energy secondary side model generates the current injected into the network based on the active power reference value and the electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

[0010] Furthermore, for doubly-fed variable-speed pumped storage, the energy buffer model is the doubly-fed motor shaft system model, the primary energy side model includes the governor and turbine model, the secondary energy side model includes the doubly-fed motor grid-connected model, the turbine-side converter and its controller model, the reference value generation model is the speed optimization controller model, and the energy state model is the water storage state model.

[0011] Furthermore, for electrochemical energy storage, the energy buffer model is a capacitor model, the primary energy side model includes battery pack, DC / DC converter and its controller model, the secondary energy side model includes DC / AC converter and its controller model, and the energy state model is a state of charge model.

[0012] Furthermore, the reference value generation model is as follows: Among them, P ref K is the active power reference value. droop and T droop K represents the proportional coefficient and time constant of the droop control, respectively. vi With T vi Let f represent the differential coefficient and time constant of the inertia control, respectively. lower with f upper These represent the upper and lower limits of the dead zone and the integral coefficient of the dead zone control, respectively; P0 represents the initial active power reference value; and K... fint Let represent the integral coefficient, Δf represent the frequency deviation, and s represent the Laplace operator.

[0013] Furthermore, the primary energy model is as follows: Among them, P first_ref S represents the primary side output power reference value. ref S and P represent the state reference value and state variable, respectively. ref and P first K represents the active power reference value and the primary side output power, respectively. p and K i represents the proportional and integral coefficients of the controller, and s represents the Laplace operator.

[0014] Furthermore, the energy buffering model is as follows: Where S represents the state variable, and T j P is used to describe the inertia when the state variable S changes. first P represents the primary side output power. e Indicates electromagnetic power.

[0015] Furthermore, the energy secondary side model is as follows: ; ; ; ; Among them, K pp and K ip K represents the proportional and integral coefficients of active power control, respectively. pq and K iq The proportional and integral coefficients for reactive power control are represented by s, where s represents the Laplace operator, and I... pcmd I p I qcmd and I q U represents the commanded value of active current, the actual value of active current, and the commanded value and actual value of reactive current, respectively. sref with U s S represents the reference value and the actual value of the grid connection point voltage, respectively. ref S and P represent the state reference value and state variable, respectively. ref P represents the active power reference value. e Indicates electromagnetic power.

[0016] A second aspect of the present invention provides a general electromechanical transient modeling system for simulating various types of energy storage, comprising: The structural identification module is configured to perform structural identification on doubly fed variable speed pumped storage and electrochemical energy storage, and decompose them into multiple sub-models according to their functions. The modeling module is configured to: for each type of sub-model, analyze the similarities and differences between doubly fed variable speed pumped storage and electrochemical energy storage in terms of energy transfer, control strategies and grid connection characteristics, and establish a general electromechanical transient model including an energy buffer model, an energy primary side model, an energy secondary side model and a reference value generation model; The reference value generation model transmits corresponding reference values ​​to the primary energy model and the secondary energy model according to the control mode. The primary energy model generates the primary output power based on the received reference values ​​and inputs it into the energy buffer model. The energy buffer model changes the state variables under the combined action of the primary output power and the electromagnetic power, and transmits them to the secondary energy model. The secondary energy model generates the current injected into the network based on the received reference values, combined with the state variables or the electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention performs structural identification on two types of energy storage models, decomposes the energy storage models into multiple sub-models according to their functions, and analyzes the similarities and differences between the two types of energy storage in terms of energy transfer, control strategies, and grid connection characteristics for each sub-model. Energy buffer model, primary energy side model, secondary energy side model, energy state model, and reference value generation model are established respectively. It can simultaneously simulate the energy transfer and grid connection characteristics of doubly-fed variable-speed pumped hydro storage and electrochemical energy storage. This is not only beneficial for the flexible use of models in large-scale power system simulation, but also helps to reduce the burden of program development. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a schematic diagram of the overall structure of the doubly-fed variable-speed pumped storage system according to Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the overall electrochemical energy storage structure of Embodiment 1 of the present invention; Figure 3 This is a structural diagram of the general electromechanical transient model of the energy buffer model in Embodiment 1 of the present invention; Figure 4 This is a structural diagram of the primary side model of pumped storage energy according to Embodiment 1 of the present invention; Figure 5 This is an overall structural diagram of the primary side model of electrochemical energy storage according to Embodiment 1 of the present invention; Figure 6 This is a structural diagram of the general electromechanical transient model of the primary energy side model of the present invention; Figure 7This is a structural diagram of the pumped storage energy secondary side model according to Embodiment 1 of the present invention; Figure 8 This is a structural diagram of the electrochemical energy storage secondary side model of Embodiment 1 of the present invention; Figure 9 This is a structural diagram of the general electromechanical transient model of the energy secondary side model in Embodiment 1 of the present invention; Figure 10 This is a structural diagram of a general electromechanical transient model for generating active power reference values ​​according to Embodiment 1 of the present invention; Figure 11 This is a structural diagram of the pumped storage speed reference value generation model according to Embodiment 1 of the present invention; Figure 12 This is a general electromechanical transient model structure diagram of the generated energy buffer model state reference value in Embodiment 1 of the present invention; Figure 13 This is a structural diagram of the general electromechanical transient model of the energy state model in Embodiment 1 of the present invention; Figure 14 This is an overall structural diagram of the general electromechanical transient model for energy storage according to Embodiment 1 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] Example 1 This embodiment provides a general electromechanical transient modeling method for simulating various types of energy storage.

[0023] To address the challenges of complex models and heavy implementation burdens associated with separately modeling two common energy storage devices—electrochemical energy storage and doubly-fed variable-speed pumped hydro storage—this embodiment provides a general electromechanical transient modeling method for simulating multiple types of energy storage. First, the structure of the two energy storage models is identified, and each model is functionally decomposed into multiple sub-models. Then, for each sub-model, the similarities and differences between the two types of energy storage in terms of energy transfer, control strategies, and grid connection characteristics are analyzed, establishing an energy buffer model, a primary energy side model, a secondary energy side model, an energy state model, and a reference value generation model. Finally, based on the variable transfer relationships between the sub-models, the sub-models are combined to construct a general electromechanical transient model for energy storage.

[0024] This embodiment provides a general electromechanical transient modeling method for simulating multiple types of energy storage, which can simultaneously simulate the energy transfer and grid connection characteristics of doubly-fed variable-speed pumped storage and electrochemical energy storage. This not only facilitates the flexible use of models in large-scale power system simulations, but also helps reduce the burden of program development.

[0025] This embodiment provides a general electromechanical transient modeling method for simulating various types of energy storage, including the following steps: Step 1: Identification and decomposition of the overall model of doubly-fed variable-speed pumped hydro storage and electrochemical energy storage.

[0026] (1) Compared with traditional fixed-speed units, doubly-fed variable-speed pumped storage can not only expand the operating head and power range of the unit because the speed is adjustable, but also achieve rapid power regulation by controlling the frequency and phase of the rotor AC excitation current.

[0027] The structure of a doubly-fed variable-speed pumped storage system is as follows: Figure 1 As shown, where P m P e These represent mechanical power and electromagnetic power, respectively; ω represents rotor speed; P ref ω ref U represents the active power reference value and the speed reference value, respectively. r I r U represents the output voltage and current of the bridge inverter circuit of the machine-side converter, respectively. g I g These represent the output voltage and current of the bridge inverter circuit of the grid-side converter, respectively. dc θ represents the capacitor voltage of the back-to-back converter. pll U represents the phase angle of the phase-locked loop output. s θ s These represent the voltage amplitude and phase at the grid connection point, respectively. PCC represents the grid connection point, and DFIG represents the doubly fed motor.

[0028] Doubly fed variable speed pumped storage is divided into five components according to its function: primary energy side model, secondary energy side model, energy buffer model, and two additional models.

[0029] The primary energy model includes a governor and a turbine model. Its main function is to simulate the process of energy transfer from the energy source (reservoir) to the energy buffer system: the governor adjusts the guide vane opening according to the reference value, thereby controlling the mechanical power output of the turbine.

[0030] The energy secondary side model includes a doubly-fed motor grid-connected model, a machine-side converter model and its controller (the grid-side converter model and its controller are mainly for maintaining the stability of the back-to-back converter capacitor voltage and have little impact on the grid-connected characteristics of the doubly-fed motor, so they are not included in the energy secondary side system). Its main function is to simulate the process of energy transfer from the energy buffer system to the grid: the machine-side converter generates rotor voltage according to the controller's command value to control the magnetic field between the stator and rotor, and then controls the electromagnetic power injected into the grid by the stator.

[0031] The energy buffer model refers to the shaft system model of a doubly fed motor. Its main function is to temporarily compensate for the imbalance between primary and secondary energy. Taking the discharge state as an example, when the electromagnetic power is greater than the mechanical power, the rotor speed decreases to release energy in a short time to make up for the active power deficit. When the electromagnetic power is less than the mechanical power, the rotor speed increases to absorb energy in a short time to absorb the active power surplus.

[0032] The additional models mainly include a speed optimization controller model and a water storage state model. The speed optimizer model is used to generate active power output reference values ​​and rotor speed reference values; the water storage state model is used to describe the changes in the amount of water stored in the reservoir.

[0033] (2) Electrochemical energy storage has received widespread attention due to its high energy density, fast response speed and good flexibility. It can play an important role in scenarios such as smoothing up new energy fluctuations, peak shaving and valley filling, frequency regulation and voltage regulation.

[0034] Structures of electrochemical energy storage, such as Figure 2 As shown, where P bat P e P represents battery power and electromagnetic power, respectively. ref V dcref These represent the active power reference value and the capacitor voltage reference value, respectively, V bat U g P represents the battery pack voltage and the output voltage of the DC / AC converter bridge inverter circuit, respectively. batref This indicates the battery power reference value, V. dc Represents the capacitor voltage, θ pll U represents the phase angle of the phase-locked loop output. s θ s These represent the voltage amplitude and phase at the grid connection point, respectively.

[0035] Electrochemical energy storage is also divided into five major components according to its function: primary energy model, secondary energy model, energy buffer model, and two additional models.

[0036] The primary energy-side model includes a battery pack, a DC / DC converter, and its controller. Its main function is to simulate the process of energy transfer from the energy source (battery) to the energy buffer system: the controller generates a battery power reference value based on a reference value, and then controls the battery pack output current I through the DC / DC converter. bat and its output active power.

[0037] The energy secondary side model includes a DC / AC converter and its controller. Its main function is to simulate the process of energy transfer from the energy buffer system to the power grid: the DC / AC converter adjusts the voltage output of the three-phase bridge inverter circuit according to the controller's command value, thereby controlling the electromagnetic power injected into the power grid.

[0038] The energy buffer model refers to the capacitor located between the DC / DC converter and the DC / AC converter. Its main function is to temporarily compensate for the imbalance between the primary and secondary energy. Taking the discharge state as an example, when the electromagnetic power is greater than the battery power, the capacitor releases energy to compensate for the active power deficit, and the capacitor voltage will decrease during this process. When the electromagnetic power is less than the battery power, the capacitor absorbs energy to absorb the active power surplus, and the capacitor voltage will increase during this process.

[0039] The additional models mainly include a reference value generation model and an energy state model. The reference value generation model is used to generate active power output reference values ​​and capacitor voltage reference values; the energy state model is used to describe the changes in the energy state of the battery pack.

[0040] In summary, whether it is doubly-fed variable-speed pumped hydro storage or electrochemical energy storage, this embodiment decomposes it into five sub-models according to different functions: energy buffer model, primary energy side model, secondary energy side model, reference value generation model, and energy state model. The five sub-models and corresponding physical structures of the two types of energy storage are summarized in Table 1.

[0041] Table 1. Five sub-models and corresponding physical structures for two types of energy storage

[0042] The following section analyzes the differences and similarities between the two energy storage models in terms of energy transfer, control strategy, and grid connection characteristics for each type of sub-model, and establishes a corresponding general electromechanical transient model. Finally, by splicing together the various sub-models according to the transfer relationship of physical quantities, a general electromechanical transient model of the energy storage model can be established.

[0043] Step 2: Energy buffer modeling.

[0044] The shaft system model of the doubly-fed induction generator is classified as an energy buffer model for doubly-fed variable-speed pumped storage. The shaft system model describes the acceleration and deceleration process of the generator rotor under the action of driving torque and braking torque, corresponding to the absorption and release of energy. Its mathematical model can be written as: (1); Where ω represents the rotor angular velocity, J represents the rotor moment of inertia, and P m P represents the mechanical power derived from the water turbine. e This indicates the electromagnetic power output by the doubly-fed motor to the power grid.

[0045] The capacitor model is categorized as an energy buffer model for electrochemical energy storage. It describes the voltage rise and fall of a capacitor under the influence of charging and discharging currents, corresponding to the absorption and release of energy. Its mathematical model can be written as: (2); Among them, V dc P represents the capacitor voltage, C represents the capacitor capacitance, and P represents the capacitor capacitance. bat P represents the active power from the DC / DC converter (and battery pack). e This indicates the electromagnetic power output from the AC / DC converter to the power grid.

[0046] Relate ω and V dc The state of the energy buffer model is defined by S; C and J are defined as inertial time constants, denoted by T. j Indicates; P m With P bat Defined as primary-side output power, denoted by P first Electromagnetic power is still represented by P. e express.

[0047] Based on the above definitions and the fact that formulas (1) and (2) can be written in the form of formula (3), a general electromechanical transient model for an energy buffer model can be established, such as... Figure 3 As shown: (3); Where S describes the amount of energy contained in the energy buffer model itself; a decrease in S indicates that the energy buffer model is releasing energy, corresponding to a decrease in the rotor speed of the doubly-fed variable-speed pumped hydro storage system or a decrease in the voltage of the electrochemical energy storage capacitor; T j T is used to describe the inertia when the state S changes. j The larger the value, the less likely the state S is to change, corresponding to a larger pumped storage J or a larger electrochemical storage C.

[0048] Step 3: Model the primary energy side.

[0049] The governor and turbine models are classified as the primary energy side model of a doubly-fed variable-speed pumped storage system, and their structure is as follows: Figure 4 As shown, where K p K i T represents the proportional and integral coefficients of the controller. y T represents the time constant of the electro-hydraulic servo system. wg Y and Y represent the water flow time constant. ref Y max Y min These represent the guide vane opening and its reference, maximum, and minimum values, respectively. The governor model has two control strategies: constant speed control and constant active power control. These two strategies are based on the speed deviation (ω) of the doubly-fed motor, respectively. ref -ω) and the deviation of active power (P) ref -P m Generate guide vane opening command value Y ref (The guide vane opening command value of a doubly-fed pumped storage system can also be considered as the mechanical power command value in per-unit form.) In the governor model, the electro-hydraulic servo system adjusts the guide vane opening Y according to the guide vane opening command value; the turbine model describes the guide vane opening and the output mechanical power P. m The relationship between them mainly simulates the water hammer effect.

[0050] The battery pack, DC / DC converter, and controller model are categorized as a primary energy side model for electrochemical energy storage, with the structure as follows: Figure 5 As shown, where P bat P batref P batmax P batmin Represents the battery power and its reference value, maximum value and minimum value, respectively, R b R p C p E represents the ohmic resistance, polarization resistance, and polarization capacitance of the battery pack, respectively. bat This represents the internal potential of the battery pack. The battery controller model has two control strategies: constant capacitor voltage control and constant active power control. These two strategies are based on the capacitor voltage deviation (V...). dcref -V dc The deviation between active power and active power (P) ref -P bat ), generates the active power command value P of the battery pack batref The DC / DC converter adjusts the battery pack output current I based on the active power command value and the battery pack voltage. bat The battery pack model primarily uses the Thevenin structure to simulate the battery pack voltage V. bat The polarization characteristics change with the output current, and an RC (resistor-capacitor) parallel circuit is used to simulate the polarization characteristics during the charging and discharging process.

[0051] The primary-side energy system model of the two types of energy storage models is mainly divided into two parts: control part: generating command values ​​for primary-side output power according to the control strategy; execution part: adjusting primary-side output power according to the command values ​​for primary-side output power.

[0052] Using the definitions of the state and primary-side output power of the energy buffer model in step 2, the control strategies of the above control parts for both energy storage systems can be summarized as: constant-S control and constant-P control. first Control can be represented by formula (4): (4); Among them, P first_ref S represents the primary side output power reference value. ref S and P represent the reference and actual values ​​of the energy buffer model state, respectively. ref P first These represent the active power reference value and the primary side output power, respectively.

[0053] The execution section reflects the physical process of energy release from the energy sources of the two types of energy storage. This is the most fundamental difference between energy storage models, and therefore each needs to be retained when establishing a general electromechanical transient model.

[0054] In summary, the general electromechanical transient model structure of the primary energy model is as follows: Figure 6 As shown, where P firstmax With P firstmin These represent the maximum and minimum values ​​of the primary energy model output power, respectively.

[0055] Step 4: Modeling the secondary energy side.

[0056] The doubly-fed generator grid-connected model, the generator-side converter and its controller model are classified into the energy secondary side model of doubly-fed variable-speed pumped storage, and its structure is as follows: Figure 7 As shown, where K pp K ip K represents the proportional and integral coefficients of active power control, respectively. pq K iq I represents the proportional and integral coefficients for reactive power control. pcmd I p I qcmd I q These represent the commanded and actual values ​​of active current and reactive current, respectively. pmax I pmin I qmax I qmin U represents the maximum and minimum values ​​of active current and reactive current, respectively. sref with Us These represent the reference and actual values ​​of the grid connection point voltage, respectively. xy This represents the actual output current. The active power control of the generator-side converter control model includes two control strategies: constant speed control and constant active power control. These two strategies are based on the speed deviation (ω) of the doubly-fed generator. ref -ω) and the deviation of active power (P) ref -P e ), generate active current command value I pcmd Reactive power control employs constant voltage control, based on the voltage deviation at the grid connection point (U). sref -U s Generate reactive current command value I qcmd The generator-side converter adjusts the rotor excitation according to the active and reactive current command values, thereby controlling the electromagnetic power and reactive power injected into the grid by the doubly-fed generator. Considering that this process responds quickly, it is replaced by an inertial element in the electromechanical transient modeling to simulate the slight delay of the modulation element.

[0057] The DC / AC converter and its controller model are classified as the energy secondary side model of electrochemical energy storage, and its structure is as follows: Figure 8 As shown. The active power control of the controller model includes two control strategies: constant capacitor voltage control and constant active power control. These two control strategies are based on the deviation of the capacitor voltage (V). dcref -V dc The deviation between active power and active power (P) ref -P e The active current command value is generated; reactive power control adopts constant voltage control, based on the voltage deviation at the grid connection point (U). sref -U s The reactive current command value is generated. The DC / AC converter adjusts the output voltage of the three-phase bridge inverter circuit according to the active and reactive current command values, thereby controlling the electromagnetic power and reactive power injected into the grid by the converter. Considering that this process responds quickly, this process is replaced by an inertial element in the electromechanical transient modeling to simulate the slight delay of the modulation element.

[0058] The secondary energy system model of the two types of energy storage models is mainly divided into two parts: the electrical control part, which generates the command values ​​of active and reactive current according to the control strategy; and the grid connection part, which controls the actual values ​​of active and reactive current output according to the command values ​​of active and reactive current.

[0059] Using the definition of the energy buffer model state in step 2, the active power control strategies of the two energy storage electrical control sections mentioned above can be summarized as: constant-s control and constant-p control. e Control, as shown in formula (5), the reactive power control strategy is constant voltage control, as shown in formula (6): (5); (6); In the grid-connected section, considering the rapid response of the generator-side converter and the DC / AC converter to the command value, an inertial link is used to simulate the delay of the modulation process, as shown in formula (7); at the same time, a phase-locked loop model is included to retain the grid-connected characteristics: ; (7); In summary, the general electromechanical transient model structure of the secondary energy model is as follows: Figure 9 As shown.

[0060] Step 5: Reference value generation model building.

[0061] The general electromechanical transient model of the reference value generation model mainly includes the generation of active power reference values ​​and the generation of energy buffer model state reference values.

[0062] The primary function of generating the active power reference value is to enable energy storage to participate in the system's frequency regulation process. The reference value generation model mainly simulates three frequency regulation characteristics: inertia control, droop control, and dead-zone control. Inertia control primarily uses a differential element to equivalently simulate the process of a rotating mass releasing kinetic energy to counteract frequency changes; droop control simulates the Pf droop characteristic of a synchronous machine; dead-zone control only responds to frequency regulation after the frequency exceeds a certain range, simulating the dead-zone characteristic of the frequency response. The active power reference value P considering these three frequency regulation characteristics is... ref The generation of the active power reference value is shown in formula (8), and the generation model of the active power reference value is as follows: Figure 10 As shown: (8); Among them, K droop and T droop K represents the proportional coefficient and time constant of the droop control, respectively. vi With T vi K represents the differential coefficient and time constant of the inertia control, respectively. fint f represents the integral coefficient, Δf represents the frequency deviation, and f lower with f upper represents the upper and lower limits of the dead zone and the integral coefficient of the dead zone control, respectively; P0 represents the initial active power reference value; and s represents the Laplace operator.

[0063] Regarding the generation of state reference values ​​for the energy buffer model, for doubly-fed variable-speed pumped storage, the speed corresponding to the turbine's highest efficiency can usually be found based on the active power reference value, and this speed is used as the reference value for the speed. Generally, the smaller the absolute value of the active power reference value, the smaller the corresponding speed reference value for the highest efficiency. An interpolation method can be used to establish a speed optimization model for doubly-fed variable-speed pumped storage, such as... Figure 11 As shown, where ω1~ω 10 Indicates different active references P ref The reference speed ω corresponding to (P1~P8, P+, P-) ref That is, the state reference value S ref P+ and P- represent the upper and lower limits of the turbine's off-duty power, respectively. When the power reference value is in the range of [P+, P-], the rotor is in a stopped state. When the active power reference value is less than 0, it can be seen that the speed reference value is also less than 0. The physical meaning is that when the pumped storage is in the charging state, the turbine rotor is in the reverse state.

[0064] Regarding the generation of the state reference value for the energy buffer model, for electrochemical energy storage, the capacitor voltage reference value does not change with the active power reference value; therefore, the corresponding state reference value for the energy buffer model is a constant. Thus, a general model for generating the state reference value for the energy buffer model can be established, such as... Figure 12 As shown, for a doubly-fed variable-speed pumped storage system, S1~S 10 Set to different active power reference values ​​P ref The corresponding speed reference value S ref This refers to the state reference value. For electrochemical energy storage, S1~S2 can be set. 10 The voltage is equal to and equal to the initial capacitor voltage, so that the capacitor voltage reference value remains unchanged.

[0065] Step 6: Model the energy state.

[0066] The general electromechanical transient model of the energy state model is modeled as a simplified abstract model, and its mathematical model is shown in formulas (9) and (10): (9); (10); Among them, P e P represents the active power injected into the power grid. e ' represents the charge and discharge power of the energy state model, and s in formula (9) represents the Laplace operator.

[0067] The energy state model defines the stored water volume of pumped hydro storage and the state of charge of electrochemical energy storage as energy states, with the energy state ranging from 0 to 1. When the electromagnetic power P... eWhen the value is greater than 0, it indicates that the stored energy is being discharged, and the energy state value will gradually decrease; when the electromagnetic power P e When the value is less than 0, it indicates that the energy storage is charging, and the energy state value will gradually increase. An energy state value of 1 indicates that the energy source (reservoir or battery pack) has reached its maximum storage capacity, at which point the I in the energy secondary side model will be... pmin When the energy state value is set to 0, the energy storage cannot be charged, it can only be discharged; when the energy state value is 0, the I in the energy secondary side model... pmax When set to 0, the stored energy cannot be discharged and can only be charged.

[0068] The structure of the energy state model is as follows Figure 13 As shown, where K out K represents the discharge efficiency. in T represents charging efficiency. total This represents the rated discharge time, which is the time required for the energy state to change from 1 to 0 under the rated discharge power.

[0069] Step 7: Overall model of general electromechanical transient model for energy storage.

[0070] P is determined using the primary energy side model first Taking the control and energy secondary side model as an example of S-control, the variable transfer relationships between the various sub-models are introduced: (1) First, based on the control mode, the reference value generation model will generate the active power reference value P. ref The energy is passed to the primary energy-side model, and the energy buffer model state reference value S is passed to it. ref Transmitted to the energy secondary side model; (2) The primary energy model is based on the active power reference value P. ref Generating primary side output power P first And pass it on to the energy buffer model; (3) The energy buffer model outputs power P on the primary side. first With electromagnetic power P e Under the influence of the energy, the state variable S begins to change and is transmitted to the energy secondary side model. (4) The energy secondary side model is based on the energy buffer model state reference value S. ref With the state variable S, the current I injected into the network is generated. xy Ultimately, the electromagnetic power P injected into the control network is controlled. e Simultaneously, as feedback, the electromagnetic power P e Transferred to the energy buffer model.

[0071] A general electromechanical transient model for energy storage, simulating pumped hydro storage and electrochemical energy storage, can be constructed. The variable transfer relationships between its structure and sub-models are as follows: Figure 14As shown, except for the primary energy model which retains some differences between doubly-fed pumped hydro storage and electrochemical energy storage, all other sub-models remain consistent. Therefore, by simply filling in different parameters, the dynamic characteristics of the two types of energy storage can be simulated. This not only simplifies the burden of model development but also increases the flexibility of model use.

[0072] It is important to note that the active power control strategy of the secondary energy model should be set with different control objects than the control strategy of the primary energy model. The primary energy model uses a constant P... first When using control, the energy quadratic model should be set to constant-S control; when the energy primary model uses constant-S control, the energy quadratic model should be set to constant-P control. e This control method allows for control over both the active power output of the energy storage model and the state of the energy buffer model, thus avoiding control conflicts.

[0073] When using constant-S control with a primary energy model, the secondary energy model should be set to constant-P control. e Taking control as an example, let's introduce the variable transfer relationships between the various sub-models: (1) First, based on the control mode, the reference value generation model generates the state reference value S. ref The active power reference value P is passed to the primary energy-side model. ref Transmitted to the energy secondary side model; (2) The primary energy model is based on the state reference value S ref Generating primary side output power P first And pass it on to the energy buffer model; (3) The energy buffer model outputs power P on the primary side. first With electromagnetic power P e Under the influence of the energy, the state variable S begins to change and is transmitted to the energy secondary side model. (4) The energy secondary side model is based on the active power reference value P ref With electromagnetic power P e Generates the current I injected into the network. xy Ultimately, the electromagnetic power injected into the network is controlled, and at the same time, the electromagnetic power P is used as feedback. e Transferred to the energy buffer model.

[0074] Example 2 This embodiment provides a general electromechanical transient modeling system for simulating various types of energy storage, including: The structural identification module is configured to perform structural identification on doubly fed variable speed pumped storage and electrochemical energy storage, and decompose them into multiple sub-models according to their functions. The modeling module is configured to: for each type of sub-model, analyze the similarities and differences between doubly fed variable speed pumped storage and electrochemical energy storage in terms of energy transfer, control strategies and grid connection characteristics, and establish a general electromechanical transient model including an energy buffer model, an energy primary side model, an energy secondary side model and a reference value generation model; The reference value generation model transmits corresponding reference values ​​to the primary energy model and the secondary energy model according to the control mode. The primary energy model generates the primary output power based on the received reference values ​​and inputs it into the energy buffer model. The energy buffer model changes the state variables under the combined action of the primary output power and the electromagnetic power, and transmits them to the secondary energy model. The secondary energy model generates the current injected into the network based on the received reference values, combined with the state variables or the electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

[0075] It should be noted that each module in this embodiment corresponds one-to-one with each step in Embodiment 1, and their specific implementation processes are the same, so they will not be repeated here.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A general electro-mechanical transient modeling method for simulating multi-type energy storages, characterized in that, include: Structural identification was performed on both doubly-fed variable-speed pumped storage and electrochemical energy storage, and both were decomposed into multiple sub-models according to their functions. For each type of sub-model, the similarities and differences between doubly-fed variable-speed pumped storage and electrochemical energy storage in terms of energy transfer, control strategies and grid connection characteristics are analyzed, and a general electromechanical transient model including an energy buffer model, a primary energy side model, a secondary energy side model and a reference value generation model is established. Among them, the reference value generation model transmits the corresponding reference values ​​to the primary energy side model and the secondary energy side model respectively according to the control mode; The primary energy model generates primary output power based on the received reference value and inputs it into the energy buffer model. The energy buffer model changes its state variables under the combined action of the primary output power and electromagnetic power, and transmits them to the secondary energy model. The secondary energy model generates the current injected into the network based on the received reference value, combined with the state variables or electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

2. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, When controlling the primary side output power using the primary energy-side model and controlling the secondary energy-side model using the state variables: The reference value generation model transmits the active power reference value to the primary energy side model and the state reference value to the secondary energy side model according to the control mode. The primary energy model generates the primary output power based on the active power reference value and inputs it into the energy buffer model. The energy buffer model changes its state variables under the influence of primary-side output power and electromagnetic power, and transmits these changes to the energy secondary-side model. The energy secondary side model generates the current injected into the network based on the state reference value and state variables, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

3. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, When the primary energy model uses constant state quantity control, the secondary energy model should be set to constant electromagnetic power control. The reference value generation model transmits the state reference value to the primary energy side model and the active power reference value to the secondary energy side model according to the control mode. The primary energy model generates the primary output power based on the state reference value and passes it to the energy buffer model; The energy buffer model changes its state variables under the influence of primary-side output power and electromagnetic power, and transmits these changes to the energy secondary-side model. The energy secondary side model generates the current injected into the network based on the active power reference value and the electromagnetic power, controls the electromagnetic power injected into the network, and sends the electromagnetic power back to the energy buffer model as a feedback signal to complete the closed-loop control.

4. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, For doubly-fed variable-speed pumped storage, the energy buffer model is the doubly-fed motor shaft system model, the primary energy side model includes the governor and turbine model, the secondary energy side model includes the doubly-fed motor grid-connected model, the turbine-side converter and its controller model, the reference value generation model is the speed optimization controller model, and the energy state model is the water storage state model.

5. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, For electrochemical energy storage, the energy buffer model is a capacitor model, the primary energy side model includes battery pack, DC / DC converter and its controller model, the secondary energy side model includes DC / AC converter and its controller model, and the energy state model is a state of charge model.

6. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, The reference value generation model is: ; wherein, P ref is an active reference value, K droop and T droop respectively represent a proportional coefficient and a time constant of droop control, K vi and T vi respectively represent a differential coefficient and a time constant of inertia control, f lower and f upper respectively represent upper and lower limits of a dead zone and an integral coefficient of dead zone control, P0 represents an initial active reference value, K fint represents an integral coefficient, △f represents a frequency deviation, and s represents a Laplace operator.

7. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, The energy primary side model is: ; wherein P first_ref represents a primary side output power reference value, S ref and S respectively represent a state reference value and a state quantity, P ref and P first respectively represent an active power reference value and a primary side output power, K p and K i represent proportional and integral coefficients of the controller, and s represents a Laplace operator.

8. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, The energy buffer model is: ; wherein S represents a state quantity, T j describes the inertia when the state quantity S changes, P first represents the primary side output power, P e represents the electromagnetic power.

9. A general electro-mechanical transient modeling method for analog multi-class energy storage as claimed in claim 1, wherein, The energy secondary side model is as follows: ； ； ； ； wherein K pp and K ip represent the proportional coefficient and the integral coefficient of the active control, respectively, K pq and K iq represent the proportional coefficient and the integral coefficient of the reactive control, respectively, I pcmd , I p , I qcmd and I q represent the command value of the active current, the actual value of the active current, the command value of the reactive current and the actual value of the reactive current, respectively, U sref and U s represent the reference value and the actual value of the grid-connected point voltage, respectively, S ref and S represent the state reference value and the state quantity, respectively, P ref represents the active power reference value, P e represents the electromagnetic power, and s represents the Laplace operator.

10. A general electro-mechanical transient modeling system for simulating multi-class energy storage, characterized in that, include: a structure identification module configured to perform structural identification on the doubly-fed variable-speed pumped storage and the electrochemical energy storage, both of which are disassembled into multiple types of sub-models according to functions; a modeling module configured to, for each type of sub-model, analyze similarities and differences between the doubly-fed variable-speed pumped storage and the electrochemical energy storage in energy transmission, control strategies and grid-connection characteristics, and establish a general electromechanical transient model including an energy buffer model, an energy primary side model, an energy secondary side model and a reference value generation model; wherein the reference value generation model transmits corresponding reference values to the energy primary side model and the energy secondary side model according to control modes; the energy primary side model generates primary side output power according to the received reference values and inputs the energy buffer model; the energy buffer model changes state variables under the joint action of the primary side output power and electromagnetic power, and transmits to the energy secondary side model; the energy secondary side model generates a current injected into the network according to the received reference values, controls electromagnetic power injected into the network, and transmits the electromagnetic power as a feedback signal to the energy buffer model, to complete closed-loop control.

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