Cooperative control method and device for doubly-fed gravity energy storage system with network construction characteristic

Abstract

The invention discloses a double-fed gravity energy storage system cooperative control method and device with a network construction characteristic. The method comprises the following steps: determining a voltage phase output by a stator side according to a voltage frequency of the stator side obtained based on a phase-locked loop; according to the voltage phase, performing coordinate conversion on a pre-acquired stator side static two-phase voltage to obtain a d-axis voltage under a two-phase rotating coordinate system; determining feedforward of stator-side electromagnetic active power based on the stator-side output voltage frequency reference value and the voltage frequency of the stator side; meanwhile, based on a stator side output voltage amplitude reference value and the d-axis voltage, feedforward of stator side electromagnetic reactive power is determined; and determining the state of the rotor-side converter according to the feedforward of the stator-side electromagnetic active power and the feedforward of the stator-side electromagnetic reactive power. According to the invention, the frequency and amplitude of the grid-connected point can be supported.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a coordinated control method and device for a double-fed gravity energy storage system with networking characteristics. Background Art

[0002] In the transition to clean, low-carbon energy, the efficient development and large-scale application of gravity energy storage systems has become a pressing technical challenge. Based on the differences in control strategies, gravity energy storage systems can be divided into two major technical approaches: grid-following control and grid-forming control. Grid-following control uses high-precision phase-locked loop technology to achieve real-time tracking of grid-connected parameters, ensuring strict synchronization between the device and the grid. Grid-forming control, based on droop characteristic control and virtual synchronous machine control, establishes a stable voltage amplitude and frequency reference, providing continuous and reliable support for grid-connected nodes even in abnormal situations such as grid failures.

[0003] Existing technologies generally only perform grid-following control on gravity energy storage systems, and do not coordinate the processing of grid data on the stator and rotor sides. The general grid-following control has the defect of changing with the grid transformation, and cannot actively support the grid connection point in the event of sudden disturbances, that is, sudden changes in grid frequency or amplitude. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a collaborative control method and device for a doubly-fed gravity energy storage system with networking characteristics, so as to achieve active support for the grid connection point.

[0005] In a first aspect, an embodiment of the present invention provides a method for cooperative control of a double-fed gravity energy storage system with grid-forming characteristics, the method comprising: S102: obtaining a voltage frequency f on the stator side according to a phase-locked loop; s_pll Determine the voltage phase θ outputted by the stator side; S104: According to the voltage phase θ, the pre-acquired stator side static two-phase voltage U sαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate system sd_pll ; S106: Based on the preset stator side output voltage frequency reference value f s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s ; S108: According to the feedforward ΔP of the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

[0006] Furthermore, S106 includes: ΔP s =K f (f s_ref -f s_pll ); where K f is the pre-acquired frequency coefficient constant; ΔQ s =K U (U sd_ref -U sd_pll ); where K U is the pre-acquired amplitude coefficient constant.

[0007] Furthermore, S102 includes: Here, s is the differential operator.

[0008] Furthermore, S104 includes: Among them, U sdq_pll The overall representation is the d-axis voltage U in the rotating coordinate system sd_pll and q-axis voltage U sq_pll .

[0009] Furthermore, S108 includes: S1082: feedforward ΔP of the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the current reference value in the rotating coordinate system on the rotor side S1084: Determine the dual closed-loop feedforward Δu of voltage and current rdq ; S1086: According to the current reference value in the rotating coordinate system of the rotor side and double closed-loop feedforward Δu rdq Determine the conduction state of the rotor-side converter.

[0010] Furthermore, S1082 includes: Among them, G PI_U (s) is the preset proportional integral controller, P s_error is the pre-acquired active power error, Q s_error is the reactive power error obtained in advance, U sd_pll is the d-axis voltage in the rotating coordinate system, ω grid is the voltage frequency f on the stator side s_pll The corresponding speed, L m is the mutual inductance between the coaxial equivalent windings of the stator and rotor in the rotating coordinate system.

[0011] Furthermore, S1084 includes: Among them, R r 、ω slip ,σ,ψ sd, respectively represent the pre-acquired rotor resistance, speed slip, leakage inductance coefficient, and stator flux of the d-axis in the two-phase rotating coordinate system; L m 、L s 、L r , I rq , I rd They respectively represent the mutual inductance between the coaxial equivalent windings of the stator and rotor in the rotating coordinate system, the self-inductance of the stator equivalent two-phase winding in the rotating coordinate system, the self-inductance of the rotor equivalent two-phase winding in the rotating coordinate system, the q-axis current on the rotor side in the rotating coordinate system, and the d-axis current on the rotor side in the rotating coordinate system.

[0012] Furthermore, S102 also includes: information of a phase-locked loop based on closed-loop collection.

[0013] In a second aspect, an embodiment of the present invention provides a coordinated control device for a double-fed gravity energy storage system with a grid-forming characteristic, the device comprising: a first control module for controlling the voltage frequency f of the stator side obtained by the phase-locked loop; s_pll Determine the voltage phase θ output on the stator side; a second control module is used to obtain the pre-acquired stator side static two-phase voltage U according to the voltage phase θ sαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate system sd_pll The third control module is used to output the stator side voltage frequency reference value f based on the preset s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s ; The fourth control module is used to feed forward ΔP according to the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

[0014] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program. Furthermore, when the computer program is executed by a processor, the steps of the collaborative control method of the doubly-fed gravity energy storage system with networking characteristics are implemented.

[0015] The beneficial effects of the embodiments of the present invention are as follows:

[0016] The embodiment of the present invention is a method for cooperative control of a double-fed gravity energy storage system with network-building characteristics and a transposition method, which adds network-building characteristic feedforward ΔP on the basis of network-following control. s , ΔQ s, to achieve active support for the grid connection point, specifically: obtain the stator side output voltage frequency fs_pll and voltage amplitude U through the phase-locked loop sd_pll With reference value f s_ref 、U sd_ref By comparing and confirming the feedforward, the corresponding feedforward is applied to the active and reactive power control loops at the grid connection point, thereby actively supporting the voltage frequency and amplitude at the grid connection point. Simultaneously, the rotor speed can be calculated based on the feedforward, thereby controlling the speed of the weight. Applying a control strategy that coordinates grid-forming characteristic feedforward with grid-following control to a doubly-fed gravity energy storage system not only achieves precise control of the weight speed but also actively supports the grid connection point. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flowchart of a collaborative control method for a doubly-fed gravity energy storage system with networking characteristics provided for the implementation of the present invention;

[0018] Figure 2 A schematic diagram of a phase-locked loop provided for the implementation of the present invention;

[0019] Figure 3 A flowchart of a collaborative control method for a doubly-fed gravity energy storage system with networking characteristics provided for the implementation of the present invention;

[0020] Figure 4 A block diagram of coordinated control of network characteristics feedforward and grid-following control of a double-fed gravity energy storage system provided for the implementation of the present invention;

[0021] Figure 5 A frequency waveform diagram of the grid end and the grid-connected end for a sudden change of grid frequency under grid-following control provided by the present invention;

[0022] Figure 6 A grid frequency waveform diagram of a grid-connected end and a grid-connected end under a grid-feedforward cooperative grid-following control provided by the present invention;

[0023] Figure 7 A diagram of active power flowing from the power grid into a doubly-fed gravity energy storage system provided for the implementation of the present invention;

[0024] Figure 8 A grid-side voltage waveform diagram of a grid-connected terminal and a grid-connected terminal voltage sudden change under grid-following control provided by the present invention;

[0025] Figure 9 A grid-connected terminal voltage waveform diagram of a grid d-axis voltage mutation under a grid-connected characteristic feedforward cooperative grid-following control provided by the present invention;

[0026] Figure 10A reactive power diagram of a power grid flowing into a double-fed gravity energy storage system provided for the implementation of the present invention;

[0027] Figure 11 A schematic diagram of a storage medium provided for the implementation of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Gravity energy storage technology, a new physical energy storage solution, achieves spatial and temporal energy translation by constructing a gravitational potential energy conversion system. During the energy storage phase, this system utilizes excess electrical energy to drive a lifting mechanism, lifting high-density objects to a predetermined height to store potential energy. During the energy release phase, the system controls the objects' descent, driving a power generation device that efficiently converts potential energy into high-quality electricity. This technology system boasts zero performance degradation throughout its lifecycle, is inherently safe and pollution-free, and is adaptable to a wide range of geographical environments, opening up new avenues for large-scale energy storage applications.

[0030] In the process of building a new power system, gravity energy storage and wind and solar power generation have natural synergistic advantages. By constructing a combined gravity energy storage and renewable energy power generation system, not only can fluctuations in renewable energy output be effectively smoothed, but the overall energy efficiency of the system can also be significantly improved. Notably, the unique mechanical moment of inertia of the gravity energy storage system provides the power system with additional anti-disturbance reserves, demonstrating excellent stability improvement when dealing with abnormal operating conditions such as grid frequency fluctuations.

[0031] Doubly-fed motors (DFGs) feature bidirectional energy flow. Their stators are directly connected to the grid, while their rotors interact with the grid via a bidirectional inverter. This significantly enhances the flexibility of renewable energy consumption. By adjusting the rotor excitation current phase, reactive power output can be dynamically adjusted, improving the grid power factor. As a core component of a new generation of power electronics, DFGs demonstrate significant technological advantages in renewable energy grid-connected control. Their innovative control models provide crucial support for renewable energy consumption.

[0032] The evolution of doubly-fed generator control technology provides a crucial guarantee for renewable energy grid integration. Based on differences in control strategies, it can be categorized into two main technical approaches: grid-following control and grid-forming control. Grid-following control utilizes high-precision phase-locked loop technology to achieve real-time tracking of grid-connected parameters, ensuring strict synchronization between the device and the grid. Grid-forming control, on the other hand, utilizes droop characteristic control and virtual synchronous machine control. By establishing stable voltage amplitude and frequency references, it can provide continuous and reliable support to grid-connected nodes even in abnormal situations such as grid faults, significantly enhancing the robustness of renewable energy grid-connected systems.

[0033] The present invention proposes a collaborative control strategy for a doubly-fed gravity energy storage system with grid-building characteristics, which adds feedforward with grid-building characteristics to the grid-following control, so that the grid-following control can also achieve active support for the grid connection point to a certain extent.

[0034] Example 1

[0035] like Figure 1 FIG. 1 is a flow chart of a coordinated control method for a double-fed gravity energy storage system with a grid-forming characteristic, the method comprising:

[0036] S102: The voltage frequency f on the stator side obtained by the phase-locked loop s_pll Determine the voltage phase θ output on the stator side.

[0037] Specifically, if Figure 2 The figure shows a closed schematic diagram of a phase-locked loop, that is, a schematic diagram of a signal processing process. The collected signal is a three-phase AC voltage signal. After the phase-locked loop updates and processes it, it returns the updated data and can output the voltage frequency f s_pll .

[0038] The phase-locked loop is generally composed of a phase detector (PD), a loop filter (LF) and a voltage-controlled oscillator (VCO). Its control structure is as follows: Figure 2 As shown, the signal processing process is:

[0039] First, collect the three-phase AC voltage v a 、v b 、v c Signal;

[0040] The virtual orthogonal components are then reconstructed to construct a two-phase rotating coordinate system;

[0041] Then, the phase difference between the input signal and the internal synchronization signal is calculated in real time based on the two rotating coordinate systems. This phase difference is processed by a filter and used to adjust the voltage-controlled oscillator parameters.

[0042] Finally, the oscillator will output the reference signal, f s_pll ; Among them, f s_pll With input voltage v a 、v b 、v c The fundamental frequency and phase of the signals are precisely synchronized.

[0043] Figure 2 The closed-loop feedback mechanism of the phase-locked loop can realize the s_pll Dynamic tracking and real-time acquisition of f s_pll , which is also one of the innovations of this application.

[0044] S104: According to the voltage phase θ, the pre-acquired stator side static two-phase voltage Usαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate system sd_pll .

[0045] S106: Based on the preset stator side output voltage frequency reference value f s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s .

[0046] Specifically, frequency modulation and voltage regulation can be achieved through S106, which is not available in the existing grid-following control. It is similar to the feedforward in the grid-forming control, but there is an essential difference. The frequency fs and voltage Us compared in the grid-forming control are constructed through the control algorithm, while the frequency fs and voltage Us compared in this step are actual values ​​sampled by the phase-locked loop. Applying feedforward with grid-forming characteristics to the grid-following control is one of the innovations of the present invention, which can achieve active support capabilities for the grid connection points.

[0047] S108: Feedforward ΔP based on the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

[0048] Specifically, according to the calculated feedforward ΔP s , ΔQ s The pre-processed data such as current and stator flux can be used to adjust the converter state (on or off) on the rotor side, thereby adjusting the speed of the rotor in the gravity energy storage system.

[0049] The coordinated control method of the double-fed gravity energy storage system with grid-forming characteristics in this embodiment adds grid-forming characteristic feedforward ΔP on the basis of grid-following control. s , ΔQ s , to achieve active support for the grid connection point, specifically: obtain the stator side output voltage frequency fs_pll and voltage amplitude U through the phase-locked loop sd_pll With reference value f s_ref 、U sd_refBy comparing and confirming the feedforward, the corresponding feedforward is applied to the active and reactive power control loops at the grid connection point, thereby actively supporting the voltage frequency and amplitude at the grid connection point. Simultaneously, the rotor speed can be calculated based on the feedforward, thereby controlling the speed of the weight. Applying a control strategy that coordinates grid-forming characteristic feedforward with grid-following control to a doubly-fed gravity energy storage system not only achieves precise control of the weight speed but also actively supports the grid connection point.

[0050] Example 2

[0051] like Figure 3 As shown, this embodiment provides a flowchart of another method for coordinated control of a doubly-fed gravity energy storage system with grid-building characteristics. This embodiment is a specific explanation of the previous embodiment.

[0052] In this embodiment, the data that need to be acquired in advance include: various reference values, constants, and the voltage frequency f on the stator side acquired based on the phase-locked loop. s_pll , stator side three-phase voltage U sABC , stator side three-phase current I sABC , rotor side three-phase current I rabc , the rotor speed of the doubly fed generator ω r 、R r 、ω slip ,σ,ψ sd 、L m 、L s 、L r , I rq , I rd 、R s , stator side instantaneous line voltage u sABC , stator side instantaneous line current i sABC .

[0053] S102: According to the voltage frequency f on the stator side obtained based on the phase-locked loop s_pll Determine the voltage phase θ output on the stator side.

[0054] S102 includes: setting the voltage frequency f on the stator side output by the phase-locked loop s_pll After integration, the stator side output voltage phase θ is obtained:

[0055]

[0056] Here, s is the differential operator.

[0057] S104: According to the voltage phase θ, the pre-acquired stator side static two-phase voltage U sαβ Convert to get d-axis voltage U sd_pll .

[0058] S1042: The phase reference value θ is used as the feedback of the phase-locked loop for stator-side coordinate transformation, transforming the two-phase stationary coordinate system into a rotating two-phase coordinate system to obtain the stator-side stationary two-phase voltage U sαβ ,include:

[0059]

[0060] S1044: Calculate U sd_pll ,include:

[0061]

[0062] Among them, U sdq_pll The overall representation is the d-axis voltage U in the rotating coordinate system sd_pll and q-axis voltage U sq_pll .

[0063] S106: Based on the preset stator side output voltage frequency reference value f s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s At the same time, based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s .

[0064] S106 includes:

[0065] ΔP s =K f (f s_ref -f s_pll ) Formula 4;

[0066] Among them, K f is the pre-acquired frequency coefficient constant;

[0067] ΔQ s =K U (U sd_ref -U sd_pll ) Formula 5;

[0068] Among them, K U is the pre-acquired amplitude coefficient constant.

[0069] S108: Feedforward ΔP based on the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

[0070] S1082: Feedforward ΔP based on the stator side electromagnetic active power sand the stator side electromagnetic reactive power feedforward ΔQ s Determine the current reference value in the rotating coordinate system on the rotor side

[0071] S1082 includes:

[0072]

[0073] Among them, G PI_U (s) is the preset proportional integral controller, P s_error is the pre-acquired active power error, Q s_error is the reactive power error obtained in advance, U sd_pll is the d-axis voltage in the rotating coordinate system on the stator side, ω grid is the voltage frequency f on the stator side s_pll The corresponding speed, L m is the mutual inductance between the coaxial equivalent windings of the stator and rotor in the pre-acquired rotating coordinate system.

[0074] The steps of calculating the power error include:

[0075] Stator side active and reactive power reference value P s_ref , Q s_ref Subtract the actual measured value of active and reactive power P on the stator side respectively s_rea , Q s_rea , and get the power error P s_error , Q s_error :

[0076] S10822:P s_rea =u sA i sA +u sB i sB +u sC i sC Formula 8;

[0077]

[0078] Among them, u sABC is the instantaneous line voltage on the stator side, i sABC is the instantaneous line current on the stator side.

[0079] S10824:P s_error =P s_ref -P s_rea Formula 10;

[0080] Q s_error =Q s_ref -Q s_rea Formula 11.

[0081] Among them, ωgrid =2πf s_pll Formula 12.

[0082] S10826: Calculate the current reference value in the rotating coordinate system on the rotor side based on Formula 6 and Formula 7

[0083] S1084: Determine the dual closed-loop feedforward Δu of voltage and current rdq .

[0084] S1084 includes:

[0085]

[0086] Among them, R r 、ω slip ,σ,ψ sd , respectively represent the pre-acquired rotor resistance, speed slip, leakage inductance coefficient, and stator flux of the d-axis in the two-phase rotating coordinate system; L m 、L s 、L r , I rq , I rd They respectively represent the mutual inductance between the coaxial equivalent windings of the stator and rotor in the rotating coordinate system, the self-inductance of the stator equivalent two-phase winding in the rotating coordinate system, the self-inductance of the rotor equivalent two-phase winding in the rotating coordinate system, the q-axis current on the rotor side in the rotating coordinate system, and the d-axis current on the rotor side in the rotating coordinate system.

[0087] S10842: stator side voltage frequency f s_pll Corresponding speed ω grid (Formula 12 can be obtained) minus the rotor speed ω r , get the speed slip ω slip , after the integration link, the phase slip θ is obtained slip :

[0088]

[0089] S10844: Convert the rotor side three-phase current into the stationary coordinate two-phase current, and then calculate the current based on the phase slip θ slip Confirm the current I in the rotating coordinate system on the rotor side rdq :

[0090]

[0091] Among them, the rotor side three-phase current I rABC It is pre-fetched.

[0092] S10846: The process for calculating the stator flux of the d-axis in a two-phase rotating coordinate system is as follows:

[0093] First, the pre-acquired stator side three-phase current I sABC Perform coordinate transformation and integration to obtain its expression in the stationary two-phase coordinate system:

[0094]

[0095] Among them, R s is the pre-obtained stator resistance, U sαβ is the result of formula 2, I sABC is the pre-acquired three-phase current on the stator side.

[0096] Finally, the stator flux is rotated to change the coordinates:

[0097]

[0098] Among them, ψ sdq To obtain the stator flux in the two-phase rotating coordinate system, θ is the calculation result of formula 1.

[0099] S10848: Calculate Δu based on formula 13 rdq .

[0100] Δu rdq It is the feedforward of the voltage and current double closed loop, used for decoupling, and is part of the control.

[0101] Among them, the leakage inductance coefficient

[0102] S1086: Based on the current reference value in the rotating coordinate system of the rotor side and double closed-loop feedforward Δu rdq Determine the conduction state of the rotor-side converter.

[0103] S10862: In current closed-loop control, the rotor current reference value and the rotor current I in the actual rotating coordinate system are rdq The difference is processed by the proportional integral controller, plus the feedforward Δu rdq That is, the rotor voltage reference value in the rotating coordinate system is obtained

[0104] in, It is confirmed based on formula 6 and formula 7, I rdq is determined based on formula 16, G PI_I (s) is the proportional-integral controller, k p_I is the pre-acquired proportional coefficient, k i_I is the pre-acquired integral coefficient.

[0105] S10864: The rotor voltage reference value is obtained The rotor-side converter is controlled to be on and off by space vector pulse width modulation (SVPWM) to achieve coordinated control of the doubly fed gravity energy storage system.

[0106] The prerequisites for implementing this embodiment are as follows:

[0107] 1) According to the formula:

[0108] in, is the grid voltage phasor, is the grid connection point voltage phasor, P and Q are the active power and reactive power flowing from the grid connection point to the grid, R and X are the line resistance and line impedance between the grid connection point and the grid, and j is an imaginary unit. This formula shows the relationship between the changes in the voltage at the output (grid connection point) of the energy storage system and the grid terminal and the transmitted active and reactive power.

[0109] 2) ΔU represents the change in the amplitude of the grid connection point voltage and the grid voltage, and δU represents the change in the phase of the grid connection point voltage and the grid voltage. It can be obtained that:

[0110]

[0111] Typically, the line is inductive, meaning the line impedance X is much greater than the line resistance R. Therefore, the grid connection point voltage can be improved by adjusting the reactive power fed into the grid from the stator side of the doubly-fed gravity energy storage system, thereby supporting the grid connection point voltage. Adjusting the active power fed into the grid from the stator side of the doubly-fed gravity energy storage system can also support the grid connection point frequency. This formula specifically expresses the amplitude and phase of the voltage change. Generally, the line is inductive, and the active and reactive power are decoupled, meaning that changes in the voltage phase (the integral of the frequency) are only related to the active power, while changes in the voltage amplitude are only related to the reactive power. Therefore, when the grid-side frequency suddenly changes, the change in the grid connection point frequency can be slowed by adjusting the active power; when the grid-side voltage amplitude suddenly changes, the grid connection point voltage can be raised by adjusting the reactive power. This is how the grid connection point voltage is supported through feedforward, and its specific implementation is expressed in the following two expressions.

[0112] 3) The active power-frequency network characteristic feedforward is shown in the following formula:

[0113] ΔP s =K f (f s_ref -f s_pll ) Formula 4;

[0114] where ΔP s is the feedforward in the stator electromagnetic active power link, K f is the frequency coefficient, f s_refis the stator side output voltage frequency reference value, that is, the ideal grid frequency during normal operation, f s_pll is the stator side output voltage frequency actually measured by the phase-locked loop (PLL). s_pll Less than the reference value f s_ref When , the active power fed into the grid from the stator side is increased.

[0115] 4) The reactive-amplitude grid characteristic feedforward is shown in the following formula:

[0116] ΔQ s =K U (U sd_ref -U sd_pll ) Formula 5;

[0117] where ΔQ s is the feedforward in the stator electromagnetic reactive power link, K U is the voltage amplitude coefficient, U sd_ref is the reference value of the d-axis amplitude of the stator side output voltage, that is, the d-axis voltage amplitude of the ideal power grid during normal operation, U sd_pll is the stator side output voltage frequency actually measured by the phase-locked loop. sd_pll Less than the reference value U sd_ref When , the reactive power fed into the grid from the stator side is increased.

[0118] In addition, in gravitational potential energy storage systems, traditional solutions mostly use synchronous motors as the core energy conversion device, and their operating characteristics are strictly coupled with the grid frequency. That is, the rotor speed of the synchronous motor must precisely match the synchronous speed corresponding to the grid operating frequency. This causes the lifting rate of heavy objects to be locked at a fixed value determined by the grid frequency. Therefore, the energy storage system can only change the power fed into the grid by adjusting the single dimension of load torque.

[0119] After the doubly-fed asynchronous motor is introduced in this embodiment, the system has a more flexible operation and control capability. By independently controlling the rotor excitation frequency, the mechanical speed and the grid frequency are decoupled. This makes the gravity energy storage system show a dual advantage in power regulation: it can adjust the power output by changing the mechanical torque of the weight, and optimize the energy conversion efficiency by adjusting the rotor speed (i.e., the speed of the weight block), which significantly enriches the power regulation means. This is one of the innovations of this invention. The specific implementation process is as follows:

[0120] This embodiment adopts a mechanical torque input model (in this model, the mechanical torque changes follow a given reference value, and the rotor speed is controlled by a speed loop). The implementation process is as follows:

[0121] The rotor speed ω r Reference value ω r_ref With the actual value ωr_rea The physical quantities such as τ and τ are used as the model input, and the reference value T of the electromagnetic torque is obtained through the speed loop in the model. e (i.e. the process from S202 to S208):

[0122] S202: Calculate the electromagnetic power P output on the stator side es :

[0123]

[0124] Where L m is the mutual inductance between the coaxial equivalent windings of the stator and rotor in the dq coordinate system; ird and irq are the d-axis component and q-axis component of the rotor side current in the rotating dq coordinate system, respectively; isd and isq are the d-axis component and q-axis component of the stator side current in the rotating dq coordinate system, respectively; ω1 is the pre-acquired synchronous speed.

[0125] S204: Calculate the rotor side output electromagnetic power P er :

[0126]

[0127] Where ω slip is the speed slip, the stator side voltage frequency f s_pll Corresponding speed ω grid (Formula 12 can be obtained) minus the rotor speed ω r Get the speed slip ω slip .

[0128] S206: Calculate the total electromagnetic power P output by the DFIG unit e :

[0129]

[0130] S208: Calculate the electromagnetic torque T in the dq coordinate system e :

[0131] T e =n p L m (i sq i rd -i sd i rq ) Formula 28;

[0132] Where n p is the number of motor pole pairs.

[0133] S210: The electromagnetic torque T e Multiplying it with the pre-obtained synchronous speed ω1 gives the stator side active power reference value f s_ref (ie, the reference value in S106).

[0134] According to the above formulas 25-28, it can be seen that the stator electromagnetic power P fed into the grid from the stator side and the rotor side is e and electromagnetic torque T e So by adjusting the mechanical torque (i.e. the load torque of the weight), the electromagnetic torque T is changed. e This allows for regulation of the power fed into the grid, and the rotor speed ω r It only affects the electromagnetic power fed into the grid on the rotor side, by adjusting the rotor speed ω r (i.e., the speed of the weight, i.e., the control of the rotor-side converter state in 10864) The stator-side active power reference value f can be adjusted s_ref , and thus the proportion of active power fed into the grid from the stator side in the total active power can be controlled, thereby achieving active support for the grid connection point.

[0135] The beneficial effects of the embodiments of the present invention are as follows:

[0136] 1) Formulas 4 and 5 implement frequency and voltage modulation, which are not present in grid-following control. This is similar to feedforward in grid-building control, but there is a fundamental difference. In grid-building control, the frequency fs and voltage Us compared are constructed by the control algorithm, while in Formulas 4 and 5, the frequency fs and voltage Us are compared using actual values ​​sampled by a phase-locked loop. Applying feedforward, which exhibits grid-building characteristics, to grid-following control is one of the innovations of this invention.

[0137] 2) While doubly-fed motors enhance control flexibility, they also bring about changes in the system inertia characteristics. Compared with synchronous motors, the moment of inertia and damping coefficient of the doubly-fed motor group are significantly reduced. Although this improves the response speed, it also weakens its natural suppression ability for grid frequency fluctuations. To compensate for this deficiency, the present invention has made targeted designs in the grid-connected control strategy: utilizing the inductance characteristics of the line, the active power fed into the node is dynamically adjusted to support the grid connection point frequency (i.e., Formula 4 and Formula 5), ​​while coordinating the real-time adjustment of reactive power to maintain the grid connection point voltage level.

[0138] 3) The present invention can adjust the power output by changing the mechanical torque of the weight through S202-S210, and optimize the energy conversion efficiency by adjusting the rotor speed (i.e., the speed of the weight block), which significantly enriches the power control means.

[0139] Example 3

[0140] This embodiment is to experimentally illustrate the method of the above embodiment. Figure 4-10 shown.

[0141] A double-fed gravity energy storage system is built in Simulink, and the control strategy of coordinated grid-forming characteristic feedforward and grid-following control proposed in this invention is adopted. The control block diagram is as follows: Figure 4 Verification of the frequency support of the grid connection point: Set the grid frequency to suddenly change from 50Hz to 49.5Hz at 0.5s and from 49.5Hz to 50Hz at 1s. The frequency change waveform under grid control is as follows Figure 5 As shown in the figure, the frequency change waveform under the feedforward cooperative network control of the network characteristics is as follows: Figure 6 As shown, compared Figure 5 and Figure 6 ,It can be seen from the rise time that the grid-following control cannot buffer the sudden change of the grid frequency, and the frequency change rate of the grid-connected end is consistent with the frequency change rate of the grid end; while the control strategy of the coordinated grid characteristic feedforward and grid-following control can effectively buffer the sudden change of the grid frequency, such as Figure 7 As shown in the figure, by changing the active power flowing through the grid connection point to provide support for the grid connection point frequency, the frequency change rate of the grid connection end is significantly smaller than the frequency change rate of the grid end. Verification of the grid connection point voltage amplitude support: Set the grid voltage amplitude per unit value to suddenly change from 1 to 0.8 at 0.8s, from 0.8 to 0.9 at 1s, and from 0.9 to 1 at 1.2s. The d-axis voltage change waveform under grid control is as follows Figure 8 As shown in the figure, the d-axis voltage change waveform under the grid-forming characteristic feedforward cooperative grid control is as follows: Figure 9 As shown, compared Figure 8 and Figure 6 From the voltage amplitude, it can be seen that the grid-following control cannot improve the sudden change of the grid voltage amplitude. The d-axis voltage at the grid-connected end is basically consistent with the d-axis voltage at the grid end. However, the control strategy of the coordinated feedforward of the grid characteristics and the grid-following control can effectively improve the change of the grid d-axis voltage, such as Figure 10 As shown in the figure, by changing the reactive power flowing through the grid connection point to provide support for the grid connection point voltage amplitude, when the grid suddenly changes to 0.8pu, the grid connection point amplitude can be raised to 0.826pu, and when the grid suddenly changes to 0.9pu, the grid connection point amplitude can be raised to 0.915pu.

[0142] This technology can realize the active support capability for grid connection points.

[0143] Example 4

[0144] The embodiment of the present invention provides a doubly fed gravity energy storage system cooperative control device with grid-forming characteristics, the device comprising: a first control module for obtaining a voltage frequency f on the stator side according to a phase-locked loop; s_pll Determine the voltage phase θ output on the stator side; a second control module is used to obtain the pre-acquired stator side static two-phase voltage U according to the voltage phase θ sαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate systemsd_pll The third control module is used to output the stator side voltage frequency reference value f based on the preset s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s ; The fourth control module is used to feed forward ΔP according to the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

[0145] The beneficial effects of the cooperative control device for a doubly-fed gravity energy storage system with networking characteristics provided in an embodiment of the present invention are the same as those of the aforementioned embodiment of the cooperative control method for a doubly-fed gravity energy storage system with networking characteristics, and will not be described in detail in this embodiment.

[0146] Example 5

[0147] The embodiment of the present invention further provides an electronic device 130, such as Figure 11 FIG. 1 is a schematic diagram of the structure of an electronic device 130 provided in an embodiment of the present invention, comprising a processor 131, a memory 132, and a bus 133. The memory 132 stores machine-readable instructions executable by the processor 131. When the electronic device 130 is running, the processor 131 communicates with the memory 132 via the bus 133, and the machine-readable instructions are used by the processor 131 to execute the method described in the above method embodiment.

[0148] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the above-mentioned method for cooperative control of a dual-fed gravity energy storage system with networking characteristics is executed. It is clear to those skilled in the art that for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the method embodiment, and will not be repeated in the present invention. In the several embodiments provided by the present invention, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection shown or discussed can be through some communication interface, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical or other forms. In addition, the functional units in the various embodiments of the present invention can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into a unit. If the functions are implemented in the form of software functional 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, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0149] The above embodiments are provided for illustrative purposes only and are not intended to limit the scope of implementation. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to provide an exhaustive list of all implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A collaborative control method for a doubly-fed gravity energy storage system with networking characteristics, characterized in that: The method comprises: S102: The voltage frequency f on the stator side obtained by the phase-locked loop s_pll Determine the voltage phase θ output on the stator side; S104: According to the voltage phase θ, the pre-acquired stator side static two-phase voltage U sαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate system sd_pll ; S106: Based on the preset stator side output voltage frequency reference value f s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s ; S108: Feedforward ΔP based on the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

2. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 1 is characterized in that: S106 includes: ΔP s =K f (f s_ref -f s_pll ); Among them, K f is the pre-acquired frequency coefficient constant; ΔQ s =K U (U sd_ref -U sd_pll ); Among them, K U is the pre-acquired amplitude coefficient constant.

3. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 2 is characterized in that: S102 includes: Here, s is the differential operator.

4. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 3 is characterized in that: S104 includes: Among them, U sdq_pll The overall representation is the d-axis voltage U in the rotating coordinate system sd_pll and q-axis voltage U sq_pll .

5. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 1 is characterized in that: S108 includes: S1082: Feedforward ΔP based on the stator side electromagnetic active power s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the current reference value in the rotating coordinate system on the rotor side S1084: Determine the dual closed-loop feedforward Δu of voltage and current rdq ; S1086: Based on the current reference value in the rotating coordinate system of the rotor side and double closed-loop feedforward Δu rdq Determine the conduction state of the rotor-side converter.

6. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 5 is characterized in that: S1082 includes: Among them, G PI_U (s) is the preset proportional-integral controller, P s_error is the pre-acquired active power error, Q s_error is the reactive power error obtained in advance, U sd_pll is the d-axis voltage in the rotating coordinate system, ω grid is the voltage frequency f on the stator side s_pll The corresponding speed, L m is the mutual inductance between the coaxial equivalent windings of the stator and rotor in the rotating coordinate system.

7. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 6 is characterized in that: S1084 includes: Among them, R r 、ω slip ,σ,ψ sd , respectively represent the pre-acquired rotor resistance, speed slip, leakage inductance coefficient, and stator flux of the d-axis in the two-phase rotating coordinate system; L m , L s , L r , I rq , I rd They respectively represent the mutual inductance between the coaxial equivalent windings of the stator and rotor in the rotating coordinate system, the self-inductance of the stator equivalent two-phase winding in the rotating coordinate system, the self-inductance of the rotor equivalent two-phase winding in the rotating coordinate system, the q-axis current on the rotor side in the rotating coordinate system, and the d-axis current on the rotor side in the rotating coordinate system.

8. The coordinated control method of a doubly-fed gravity energy storage system with networking characteristics according to claim 1, characterized in that: S102 also includes: information of a phase-locked loop based on closed-loop collection.

9. A coordinated control device for a double-fed gravity energy storage system with networking characteristics, characterized in that: The device comprises: The first control module is used to obtain the voltage frequency f of the stator side according to the phase-locked loop s_pll Determine the voltage phase θ output on the stator side; The second control module is used to convert the pre-acquired stator side static two-phase voltage U sαβ Perform coordinate transformation to obtain the d-axis voltage U in the rotating coordinate system sd_pll ; The third control module is used to control the frequency of the stator side output voltage based on the preset stator side output voltage frequency reference value f s_ref and the voltage frequency f on the stator side s_pll Determine the feedforward ΔP of the stator side electromagnetic active power s ; Based on the stator side output voltage amplitude reference value U sd_ref , the d-axis voltage U in the rotating coordinate system sd_pll Determine the feedforward ΔQ of the stator-side electromagnetic reactive power s ; The fourth control module is used to feed forward ΔP of the electromagnetic active power on the stator side s and the stator side electromagnetic reactive power feedforward ΔQ s Determine the rotor-side converter status.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the collaborative control method of a double-fed gravity energy storage system with grid-forming characteristics as described in any one of claims 1 to 8 above are implemented.

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