Automatic active support control method considering broadband oscillation suppression of local power grid

Abstract

The invention discloses an automatic active support control method considering broadband oscillation suppression of a local power grid. The method comprises the following specific implementation steps: (1) considering active support of a wind storage system of local power grid tie line power and an energy storage SoC state; (2) dual-band PSS design considering local power grid frequency and voltage broadband oscillation; and (3) automatic active support control considering broadband oscillation suppression of the local power grid. According to the method, the frequency and voltage recovery process after disturbance can be remarkably improved, the broadband oscillation amplitude is effectively suppressed, and the dynamic stability of a regional power grid containing new energy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system operation and control, in particular to an automatic active support control method considering local grid broadband oscillation suppression. BACKGROUND

[0002] With the continuous deployment of wind power in mountainous areas, coastal areas, deserts, and dispersed load center areas, dispersed wind- energy storage systems have gradually become an important form of new energy consumption and local grid support. Unlike centralized large-scale wind farms, dispersed wind- energy storage systems are usually connected to the distribution network or the end of the regional grid in a multi-point and multi-scale manner. These access points are often weak in structure and are mainly used to improve local new energy consumption capacity, achieve peak load shifting, enhance disaster resistance, and ensure the power supply safety of important loads. In the system, wind turbines provide renewable energy generation, and energy storage systems undertake regulation and buffering, emergency support, and dynamic power management, enabling dispersed wind- energy storage systems to have the ability to respond quickly and support locally, which is a key resource for improving flexibility and stability in new power systems.

[0003] In the above application scenarios, the operating environment of dispersed wind- energy storage systems is more complex. On the one hand, wind power units are affected by terrain, wind speed, and wake effects, and the output power of different units differs significantly. On the other hand, energy storage devices are limited by state of charge (SoC), and their sustainable support capabilities are inconsistent. In addition, dispersed wind- energy storage systems are usually connected to weak grid areas, which have low short-circuit ratios and high impedance, and are prone to significant frequency and voltage deviations under disturbances. Under line short-circuit, sudden wind speed changes, rapid load increases, or natural disasters, the frequency and voltage at the grid-connected point often drop simultaneously, requiring wind- energy storage systems to quickly provide active and reactive power support.

[0004] Existing control modes usually use traditional active- frequency and reactive- voltage decoupling control methods. However, under weak grid coupling conditions, this method cannot accurately quantify the support capacity of wind power and energy storage, and may cause uncoordinated regulation, insufficient support, or resource waste. At the same time, since dispersed wind- energy storage systems are dominated by power electronic converters, the equivalent inertia and damping of the system are significantly reduced, and the control coupling between wind- energy storage units and the grid is more complex. During active support, the system is prone to excite low-frequency, subsynchronous, and even super-synchronous broadband oscillations, further weakening the transient stability of synchronous machines. Existing technologies focus on individual support strategies for wind power or energy storage, but there is still a lack of effective coordinated frequency- voltage support and broadband oscillation suppression schemes for the multi-point access characteristics, support capacity differences, and weak grid coupling oscillations of dispersed wind- energy storage systems. Therefore, under the background of high proportion of new energy access, it is of great significance to construct a dispersed wind- energy storage active support method that can adapt to weak grid characteristics to improve the safe and stable operation of regional grids. SUMMARY

[0005] The purpose of the present application is to provide an automatic active support control method considering local power grid broadband oscillation suppression. The present application designs a double-frequency-band virtual power system stabilizer (PSS) based on line power deviation and grid-connected point voltage deviation, respectively providing additional damping for low-frequency (0.2-2 Hz) and subsynchronous (10-40 Hz) oscillation modes. Simulation results show that this method can significantly improve the frequency and voltage recovery process after disturbance, effectively suppress the broadband oscillation amplitude, and improve the dynamic stability of regional power grids containing new energy.

[0006] The present application provides an automatic active support control method considering local power grid broadband oscillation suppression, and the specific implementation steps are as follows: (I) Considering the active support of wind storage system of local power grid tie line power and SoC state: Establish the active support of wind storage system, including the following active control links: enable the wind storage combined system to coordinate to provide frequency and voltage regulation; through an additional control strategy, the wind turbine generator and the energy storage can provide active frequency and voltage support to the power grid; considering the tie line power change, the wind turbine adjusts the droop control output according to the frequency deviation and tie line power change; considering the SoC state of the energy storage, the active output of the energy storage droop control is adjusted; the above active control links are integrated to perform decentralized wind storage system active support control; (II) Double-frequency-band PSS design considering local power grid frequency and voltage broadband oscillation: Design PSS in low-frequency and subsynchronous frequency bands to provide positive damping and suppress local power grid oscillation; the time constant of the double-frequency-band PSS is designed according to the oscillation frequency; Connect the PSS that suppresses the frequency oscillation of the local power grid to the wind turbine and the PSS that suppresses the voltage oscillation to the energy storage, and select the damping coefficient based on the oscillation frequency; considering the frequency and voltage broadband oscillation of the local power grid, perform power control for decentralized wind storage oscillation suppression; (III) Automatic active support control considering local power grid broadband oscillation suppression: Real-time acquisition of frequency deviation, frequency change rate, voltage deviation and tie line power signals of the local power grid, and suppression of different frequency band oscillation modes through double-frequency-band PSS; at the same time, based on virtual inertia and droop control mechanism, the wind turbine and energy storage jointly adjust the active / reactive output to quickly support the frequency and voltage of the local power grid; tie line power control further enhances the dynamic coordination ability between regions.

[0007] Further, in step (I), through an additional control strategy, the wind turbine generator and the energy storage can provide active frequency and voltage support, specifically: Introduce frequency change rate control in the active link of the doubly-fed induction generator to realize fast adjustment of output during disturbance, so that it exhibits the inertia characteristics of a synchronous generator, and the formula is as follows: (1); wherein, P wind1 is the active power output of the wind turbine in response to the system frequency variation; K wind_J is the inertia coefficient of the wind turbine, J is the virtual inertia of the wind turbine; f denotes the system frequency.

[0008] Further, in step (1), considering the tie-line power variation, the wind turbine adjusts the droop control output according to the frequency deviation and the tie-line power variation, specifically: Considering the tie-line power variation: (2); wherein, Δ P tl is the tie-line power adjustment error signal, P tl * is the planned active power of the tie-line, P tl is the actual active power of the tie-line; The wind turbine adjusts the droop control output according to the frequency deviation and the tie-line power variation: (3); wherein, P wind2 is the wind turbine droop control active output adjustment; f, f ref are the system frequency and the system frequency reference value, respectively; K wind2 ，K wind_tl are the frequency droop coefficient and the tie-line power droop coefficient, respectively.

[0009] Further, in step (1), considering the SoC state of the energy storage, the energy storage adjusts the droop control active output, specifically: In the process of actively supporting the energy storage system, its sustainable support capability is directly limited by the SoC. The SoC of the energy storage power station is calculated as: (4); wherein, SOC i is the SoC value of the energy storage power station; i SOC 0 is the initial value of the SoC; S rated denotes the power reference value, η is the charging and discharging efficiency of the energy storage; I t ​For output current; The limitation coefficient reflecting the remaining energy level of the energy storage is constructed, so that the output power can be adaptively adjusted with the SoC, ensuring the safety of the energy storage operation and realizing the dynamic matching of the support capacity and available energy. The SoC constraint coefficient is introduced K SOC for unified quantification and limitation of the maximum output power of the energy storage, and the expression is as follows: (5); In the formula, K soc is the energy storage power support coefficient; SOC max， SOC min respectively represent the maximum and minimum values of the energy storage SoC; Active output regulation of energy storage droop control: (6); Wherein, K ES is the frequency response gain coefficient of the energy storage system, f is the real-time operating frequency of the system, f ref is the system frequency reference value, K ES_tl is the gain coefficient of the tie-line power regulation channel, Δ P tl is the tie-line power regulation error signal.

[0010] Further, in step (1), the above active control links are integrated, and the active support control of the distributed wind storage system is specifically: (7); In the formula, P wind1 is the active power output by the wind turbine in response to the system frequency change; P wind2 is the active output regulation of wind turbine droop control; P WPESS_ref ，Q WPESS_ref is the active power reference value and the reactive power reference value of the distributed wind storage system active support; K q is the reactive voltage droop control coefficient, which is used to represent the adjustment sensitivity of the reactive power of the distributed wind storage system to the voltage deviation; U is the real-time voltage amplitude of the grid-connected point of the distributed wind storage system; U 0 is the rated operating voltage of the system or the set voltage reference value, which is used as the reference for reactive voltage control.

[0011] Further, in step (ii), PSSs are designed in low frequency and subsynchronous frequency band respectively to provide positive damping and suppress local grid oscillation; time constants of dual-band PSS are designed according to oscillation frequency, specifically: (8) ; wherein, f mode The current identified oscillation frequency is determined according to the small signal stability analysis or online modal identification result of the system; is a function of phase compensation; for PSS#1 of dual-band PSS, is adopted f mode =f i ∈[0.2, 2] ; for PSS#2 of dual-band PSS, is adopted f mode =f j ∈[10, 40] is the time constant of the lead-lag element of PSS, used to control the working frequency of the damper.

[0012] Further, in step (ii), the PSSs for suppressing local grid frequency oscillation are connected to the wind turbine and the PSSs for suppressing voltage oscillation are connected to the energy storage, and the damping coefficient selection is based on the oscillation frequency: (9) wherein, is the gain coefficient of the designed power system stabilizer (PSS), used to adjust the additional damping capacity of the wind turbine or energy storage converter under a specific oscillation mode; represents the PSS gain for suppressing low-frequency oscillation, generally corresponding to the electromechanical oscillation mode of 0.2-2 Hz, used for PSS#1 of dual-band PSS; represents the PSS gain for suppressing subsynchronous oscillation, generally corresponding to the oscillation frequency band of 10-40 Hz, used for PSS#2 of dual-band PSS, and to avoid overcompensation of low-frequency damping, generally satisfies the design requirement of ; When , it represents that the system is in a low-frequency oscillation mode generated by the electromechanical coupling between generator sets, at this time the gain is selected; when , it represents that the system is in a subsynchronous frequency band oscillation affected by the flexibility characteristics of power electronic interface or transmission line, at this time the gain is selected; wherein, , are the center frequency or typical oscillation frequency point of low-frequency mode and subsynchronous mode respectively; Power control of distributed wind-storage oscillation suppression: (10) wherein, represents PSS-based additional damping power provided by wind turbine in active power channel; represents additional damping reactive power provided by energy storage device in reactive power channel; both of them constitute active-reactive dual-channel damping output in distributed wind-storage oscillation suppression strategy; variable and are two damper transfer functions acting on wind turbine active power channel, usually corresponding to PSS filter structure of low frequency (PSS#1) and subsynchronous frequency band (PSS#2), which are in the form of lead-lag link or band-pass filter link, used to provide the required phase lead and amplitude gain near the target oscillation frequency; the two are superimposed to constitute the comprehensive damping characteristics of wind turbine active side; variable and are two damper transfer functions acting on energy storage reactive power channel, similar in structure to the active side, but the frequency band arrangement is more focused on voltage oscillation and high frequency mode, so that the energy storage converter can provide fast reactive power compensation on the voltage side.

[0013] Further, in step (three), the active support control method of distributed wind-storage system considering local power grid wide frequency oscillation suppression is specifically: (11) ; (12) ; wherein, and respectively represent the active reference value and the reactive reference value output by the virtual synchronous machine control unit, used to adjust the active support capability of the wind-storage combined system under frequency disturbance and voltage deviation, the active reference value and the reactive reference value are composed of the planned power and the incremental support amount; and are respectively the planned active power and the planned reactive power of the distributed wind-storage system under normal working condition, usually obtained by dispatching plan, power prediction or steady-state optimization, used as the baseline set value for wind-storage system operation; is the incremental active support amount generated by the VSG controller according to the local power grid frequency deviation, frequency change rate and tie-line power deviation, its typical form includes droop regulation term, inertia type response term and tie-line cooperative regulation term, used to enhance the active regulation capability of the system to the disturbance and suppress the frequency deviation and oscillation; The increment reactive power support generated by the VSG controller according to the voltage deviation at the grid connection point and the voltage dynamic characteristic can include a voltage droop adjustment term and a voltage change rate adjustment term, which are used to improve the local voltage support capability and suppress voltage oscillation and high-frequency resonance risk.

[0014] (13); (14); wherein, is an equivalent rotational inertia constant of the VSG, which is used to represent the inertia response capability of the wind storage system under frequency disturbance; is an active reference value generated by the VSG control unit, which is usually obtained by superimposing a planned active power and an increment support power based on factors such as frequency deviation and tie-line power deviation; is the actual electromagnetic active power output by the wind storage system to the grid, which is a feedback quantity in the active balance constraint; variable is the instantaneous angular frequency of the output voltage of the virtual synchronous machine, is the rated angular frequency (usually corresponding to the rated frequency of the grid, 50 Hz or 60 Hz). The difference between the two represents the frequency deviation of the system. The coefficient is an equivalent damping coefficient, which is used to simulate the natural damping effect of the synchronous machine damping winding and the speed regulation system on the frequency change. The greater the value, the higher the oscillation decay rate. In formula (14), is the reactive power output by the wind storage system, is the reactive reference value generated by the VSG controller, which is usually composed of a planned reactive power and an increment reactive support generated based on the voltage deviation; variable is the actual value of the voltage at the grid connection point of the wind storage system, is the rated voltage or given voltage reference value, and the difference between the two represents the voltage deviation at the grid connection point; parameter is the reactive voltage droop coefficient, which physically represents the sensitivity of reactive output to voltage change, determines the amplitude of the reactive regulation of the VSG to the voltage disturbance.

[0015] The working principle of the present application is as follows: In view of the problems of inertia and damping reduction and wide-frequency oscillation caused by the access of the distributed wind storage system to the weak grid, the present application constructs an automatic active support control framework for the local grid. Based on the collaborative control of the wind turbine and the energy storage, the method comprehensively utilizes multi-source information such as system frequency, voltage and tie-line power, to realize the unified coordination of frequency support, voltage regulation and oscillation suppression.

[0016] At the active control level, the fan side releases rotor kinetic energy at the initial stage of disturbance by introducing frequency change rate related to frequency deviation control, to provide equivalent inertia and droop support; at the same time, the tie-line power change is introduced into the active regulation channel to enhance the dynamic coordination ability in the process of regional power exchange. When participating in frequency support, the energy storage side introduces the state of charge constraint mechanism, so that the active output is adaptively adjusted according to the available energy level, so as to realize safe and sustainable active support. At the reactive power control level, the wind storage system carries out droop regulation according to the voltage deviation at the grid connection point, to provide fast reactive power compensation to stabilize the local voltage.

[0017] On the basis of the above active support, the application further designs a double-frequency-band power system stabilizer for low-frequency and subsynchronous frequency bands, which is connected to the fan active channel and the energy storage reactive channel respectively, to provide additional damping for different frequency band oscillation modes. Finally, the fan, energy storage automatic active support and double-frequency-band damping control are unified and coordinated through the virtual synchronous machine control framework, to realize the coordinated suppression of local grid frequency, voltage and wideband oscillation.

[0018] Compared with the prior art, the application has the following advantages: The frequency and voltage active support control method based on the distributed wind storage system can coordinate the active and reactive power output of the fan and the energy storage under large disturbance conditions, effectively suppress the wideband oscillation of the local grid, reduce the frequency valley and voltage drop during the fault, shorten the oscillation duration, and significantly improve the transient stability and operation safety of the weak end grid.

[0019] The application effectively makes up for the problem of insufficient inertia and damping of the local grid under the condition of high proportion of new energy access by introducing the coordinated active support control of the distributed wind storage system. Under large disturbance conditions, the fan and the local grid frequency and voltage change, and the energy storage realizes continuous controllable active and reactive regulation under the SoC constraint, thereby significantly reducing the frequency minimum point and voltage drop amplitude. By introducing the tie-line power information into the control process, the application enhances the dynamic coordination ability of regional power exchange and reduces the power flow impact during the fault. In addition, the designed double-frequency-band PSS can provide effective damping for low-frequency and subsynchronous oscillation, so that the oscillation amplitude is significantly reduced and the decay speed is accelerated, avoiding the amplification of oscillation between different frequency bands. Under the comprehensive action, the application can shorten the frequency and voltage recovery time after disturbance, improve the transient stability and operation safety of the weak grid, and is suitable for the operation scene of regional grid with high proportion of new energy access. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings of the application are as follows.

[0021] Figure 1 It is an automatic active support control method of a single distributed wind storage system considering local grid wideband oscillation suppression. Figure 2 is the topology diagram of the distributed wind storage system accessing the power grid in the application; Figure 3 is the frequency change diagram of the fault point in the application; Figure 4 is the voltage change diagram of the fault point in the application; Figure 5 is the active power output change diagram of the No. 1 wind turbine in the application; Figure 6 is the tie line power change diagram in the application.

[0022] Figure 7 is the No. 1 synchronous machine speed change diagram in the application. DETAILED DESCRIPTION

[0023] The application will be further described below in conjunction with the drawings and examples. It should be understood that the examples are only for the purpose of illustrating the application, and are not intended to limit the protection scope of the application.

[0024] Example: as shown in the figure, the embodiment of the application provides an automatic active support control method considering local power grid broadband oscillation suppression, and the specific implementation steps are as follows: Figure 1 (1) considering the active support of the wind storage system of the local power grid tie line power and the state of charge (SoC) of the energy storage: The access of the distributed wind storage system reduces the inertia and damping of the power grid, making it difficult to maintain stability of the frequency and voltage. Therefore, active support control is needed to enable the wind storage combined system to coordinate to provide frequency and voltage regulation and improve the stability of the local power grid. Through an additional control strategy, the wind turbine generator and the energy storage can provide active frequency and voltage support to the power grid. The frequency change rate control is introduced in the active link of the doubly-fed induction generator, which can realize rapid adjustment of the output during disturbance and make it exhibit the inertia characteristics of a synchronous generator.

[0025] (1); wherein, wind1 is the active power output of the wind turbine in response to the change of the system frequency. P wind_J is the inertia coefficient of the wind turbine, K is the virtual inertia of the wind turbine. J represents the system frequency. f

[0026] The load mutation will cause the frequency change. In order to enhance the inter-area frequency support capability of the wind storage system, the tie line power change (2); wherein, Δ P tl ​Interconnection line power regulation error signal, P tl * Planned active power of interconnection line, P tl Actual active power of interconnection line.

[0027] The frequency deviation and the interconnection line power change are used to adjust the droop control output of the fan: (3) ; In the formula, P wind2 The active output of the fan droop control is adjusted. f, f ref The system frequency and the system frequency reference value are respectively. K wind2 ，K wind_tl The frequency droop coefficient and the interconnection line power droop coefficient are respectively.

[0028] In the process of participating in active support, the sustainable support capability of the energy storage system is directly limited by SoC, and the SoC of the energy storage power station is calculated as: (4) ; In the formula, SOC i The SoC value of the energy storage power station i . SOC 0 The initial value of SoC. S rated The power reference value is represented, η The energy storage charging and discharging efficiency. I t The output current.

[0029] If high-power discharge is maintained when SoC is too low, not only will the battery be over-discharged and even damaged, but also the energy storage will not be able to provide support throughout the fault process. Therefore, it is necessary to build a limit coefficient reflecting the remaining energy level of the energy storage, so that its output power can be adaptively adjusted with the change of SoC, to ensure the safety of the energy storage operation and realize the dynamic matching of support capability and available energy. Based on this, the present application introduces a SoC constraint coefficient K SOC , which is used to uniformly quantify and limit the maximum output power of the energy storage, and its expression is as follows: (5) ; In the formula, K soc The energy storage power support coefficient is; SOC max， SOC minrespectively represent the maximum and minimum values of the energy storage SoC; Active output regulation of energy storage droop control: (6) ; wherein, K ES is the frequency response gain coefficient of the energy storage system, f is the real-time operating frequency of the system, f ref is the system frequency reference value, K ES_tl is the gain coefficient of the tie-line power regulation channel, Δ P tl Tie-line power regulation error signal.

[0030] Further, in step (1), the active support control of the distributed wind storage system is specifically: (7) ; wherein, P wind1 is the active power output of the wind turbine in response to the system frequency change; P wind2 is the active output regulation of wind turbine droop control; P WPESS_ref ，Q WPESS_ref is the active power reference value and the reactive power reference value of the distributed wind storage system active support; K q represents the reactive voltage droop control coefficient, which is used to represent the adjustment sensitivity of the reactive power of the distributed wind storage system to the voltage deviation; U represents the real-time voltage amplitude of the grid-connected point of the distributed wind storage system; U 0 represents the system rated operating voltage or the set voltage reference value, which is used as the reference for reactive voltage control.

[0031] (2) Double-frequency band PSS design considering local grid frequency and voltage wide-band oscillation: After the access of the distributed wind storage, due to the significant decrease of system inertia and damping, the coupling between wind storage controllers, the system may be dynamically unstable in low frequency, subsynchronous and other frequency bands, thereby forming a wide-band oscillation. The PSS is designed in low frequency and subsynchronous frequency bands to provide positive damping and suppress local grid oscillation. The double-frequency band PSS designs time constant according to the oscillation frequency: (8) ; wherein, f modeThe current identified oscillation frequency is determined according to the system small signal stability analysis or online modal identification results. is a function of phase compensation. For PSS#1, the gain f mode =f i ∈[0.2, 2] is used; for PSS#2, the gain f mode =f j ∈[10, 40] is used. is the time constant of the PSS lead-lag element, used to control the operating frequency of the damper.

[0032] The PSS connected to the wind turbine to suppress local grid frequency oscillations and the energy storage connected to suppress voltage oscillations are based on the selection of the damping coefficient of the oscillation frequency: (9) ; wherein, is the gain coefficient of the designed power system stabilizer (PSS), used to adjust the additional damping capability of the wind turbine or energy storage converter under a specific oscillation mode; represents the PSS gain for suppressing low-frequency oscillations, generally corresponding to the electromechanical oscillation mode of 0.2-2 Hz, used for PSS#1; represents the PSS gain for suppressing subsynchronous oscillations, generally corresponding to the oscillation frequency band of 10-40 Hz, used for PSS#2, and to avoid overcompensation of low-frequency damping, generally meets the design requirement of .

[0033] When , it indicates that the system is in a low-frequency oscillation mode generated by the electromechanical coupling between generator sets, at this time the gain is selected; when , it indicates that the system is in a subsynchronous frequency band oscillation affected by the flexibility characteristics of power electronic interfaces or transmission lines, at this time the gain is selected. Wherein, , are the center frequency or typical oscillation frequency point of the low-frequency mode and the subsynchronous mode, respectively.

[0034] Power control for decentralized wind storage oscillation suppression: (10) ; wherein, represents the additional damping power provided by the wind turbine in the active channel based on PSS; represents the additional damping reactive power provided by the energy storage in the reactive power channel. Together they constitute the active-reactive dual-channel damping output in the distributed wind-storage oscillation suppression strategy.

[0035] variable and are respectively the two damper transfer functions acting in the wind turbine active power channel, usually corresponding to the PSS filter structure for low frequency (PSS#1) and subsynchronous frequency band (PSS#2), which are in the form of lead-lag or band-pass filter sections, used to provide the required phase lead and amplitude gain around the target oscillation frequency. The two are superimposed to constitute the comprehensive damping characteristics of the wind turbine active side.

[0036] variable and are respectively the two damper transfer functions acting in the energy storage reactive power channel, similar in structure to the active side, but with a more voltage oscillation and high frequency mode focused frequency band arrangement, so that the energy storage converter can provide fast reactive power compensation on the voltage side.

[0037] (Three) Automatic active support control considering local grid wide frequency oscillation suppression: This method proposes an active support control strategy for frequency and voltage coordinated regulation in view of the problem of significant decrease in local grid inertia, insufficient damping and frequent 0.2-40Hz wide frequency oscillation caused by the access of distributed wind-storage system. The method identifies the dynamic coupling characteristics of low frequency oscillation mode (0.2-2Hz) and subsynchronous / super-synchronous oscillation mode (10-40Hz) through small signal modeling and eigenvalue analysis of the wind-storage system, and on this basis, builds an active support consisting of double-band PSS (PSS#1 and PSS#2) + frequency and voltage response.

[0038] The control method real-time collects the frequency deviation, frequency change rate, voltage deviation and tie-line power signals of the local grid, and through the double-band PSS, suppresses the oscillation modes of different frequency bands; at the same time, based on the virtual inertia and droop control mechanism, the wind turbine and energy storage jointly regulate the active / reactive output, quickly supporting the frequency and voltage of the local grid; the tie-line power control further enhances the dynamic coordination ability between regions. Through the coordinated release of kinetic energy and reactive power support by the wind turbine and energy storage system during disturbance, the method can significantly improve the equivalent damping of the local grid, reduce the frequency drop and voltage fluctuation amplitude, effectively suppress the wide frequency oscillation and improve the transient stability of synchronous machines. Distributed wind-storage system active support control method considering local grid wide frequency oscillation suppression: (11); (12); wherein, and P ref, active and P ref, reactive are the active and reactive reference values output by the VSG control unit, used to adjust the active and reactive support capability of the wind- storage system under frequency disturbance and voltage deviation. The reference values are composed of the scheduled power and the incremental support power. and P scheduled, active and P scheduled, reactive are the scheduled active and reactive power of the distributed wind-storage system under normal operating conditions, usually obtained by dispatching plan, power prediction or steady-state optimization, and used as the baseline setting value for the operation of the wind-storage system. P inc, active is the incremental active support power generated by the VSG controller according to the local grid frequency deviation, frequency change rate and tie-line power deviation, which typically includes droop regulation term, inertia-like response term and tie-line coordinated regulation term, used to enhance the active regulation capability of the system under disturbance and suppress frequency deviation and oscillation. P inc, reactive is the incremental reactive support power generated by the VSG controller according to the grid point voltage deviation and voltage dynamic characteristics, which can include voltage droop regulation term and voltage change rate regulation term, used to improve the local voltage support capability and suppress voltage oscillation and high-frequency resonance risk.

[0039] (13); (14); wherein, J is the equivalent rotational inertia constant of the Virtual Synchronous Generator (VSG), used to represent the inertia response capability of the wind-storage system under frequency disturbance; P ref, active is the active reference value generated by the VSG control unit, usually obtained by superimposing the scheduled active power and the incremental support power based on factors such as frequency deviation and tie-line power deviation; P active is the actual electromagnetic active power output by the wind-storage system to the grid, which is the feedback quantity in the active balance constraint.

[0040] Variable ω is the instantaneous angular frequency of the VSG output voltage, ω ref is the rated angular frequency (usually corresponding to the grid rated frequency 50 Hz or 60 Hz). The difference between the two represents the system frequency deviation. The coefficient J d is the equivalent damping coefficient, used to simulate the natural damping effect of the synchronous machine damping winding and speed regulation system on frequency change, the larger the value, the higher the oscillation decay rate.

[0041] In formula (14), P reactive is the reactive output power of the wind-storage system, For the reactive power reference generated by the VSG controller, it is usually composed of the scheduled reactive power and the incremental reactive power support generated based on the voltage deviation. Variable is the actual value of the grid-connected point voltage of the wind storage system, is the rated voltage or given voltage reference, and the difference between the two characterizes the grid-connected point voltage deviation. Parameter is the reactive voltage droop coefficient, which has the physical meaning of the sensitivity of the reactive output to the voltage change, determines the amplitude of the reactive regulation of the VSG to the voltage disturbance.

[0042] In an embodiment, as Figure 1 , Figure 2As shown, the application is based on an improved IEEE 39-node test system to build a simulation model. The system includes ten synchronous generators, several transmission lines and load nodes, and three sets of distributed wind power and energy storage systems are connected to nodes 40, 41 and 42. In the figure, the first generator G1 is located at bus 30, connected to the main network through node 2, located in the upper left part of the system; the second generator G2 is located at bus 31, connected to the middle network through nodes 7 and 6, distributed in the lower left area of the figure; the third generator G3 is located at bus 32, connected to nodes 10, 11 and 12 to form a middle power collection area with surrounding units; the fourth generator G4 is located at bus 34, connected to the right middle part of the main network through nodes 20 and 19; the fifth generator G5 is located at bus 33, distributed on the left side of G4, and forms a local parallel unit group with nodes 22 and 23; the sixth generator G6 is located at bus 35, located at the lower right end of the figure, connected to the lower branch through node 22; the seventh generator G7 is located at bus 36, located in the right middle area, connected to the main network through nodes 23, 24 and 21; the eighth generator G8 is located at bus 38, which is the main power supply in the upper right area, connected to the system through nodes 29 and 21; the ninth generator G9 is located at bus 39, distributed in the left middle part, connected to the main network through nodes 9, 8 and 5; the tenth generator G10 is located at bus 37, at the top of the figure, connected to the upper main network through nodes 26 and 25. There are three sets of distributed wind power and energy storage systems in the figure, of which the first distributed wind storage system WP-ESS1 is located at node 40, connected to the branch of nodes 14-15, located in the left middle part of the system, and the disturbance test point is at the red arrow; the second distributed wind storage system WP-ESS2 is located at node 41, distributed in the right middle area, connected to nodes 16 and 24 and their adjacent lines; the third distributed wind storage system WP-ESS3 is located at node 42, distributed in the upper right area of the figure, connected to the main network through nodes 17, 26 and 28. The numbers 1-42 in the figure represent the positions of the system buses, and the numbers marked on the lines, such as 12, 18, 20, 25, etc., represent the branch numbers, which are used to indicate the connection relationship and power flow direction of the main network.

[0043] wherein the distributed wind storage system is composed of several doubly-fed induction generator wind turbines, and each set of wind storage unit is configured with a battery energy storage device, and the energy storage state of charge (which can be different to reflect the difference in supporting capacity of the distributed wind storage unit in actual working conditions) is Firstly, active active support control is constructed on the fan side. The fan provides a virtual inertia response according to the system frequency change rate when the disturbance occurs, and the active increment is determined by formula (1); subsequently, in order to enhance the inter-regional mutual assistance capability, the power deviation of the tie line is introduced into the active regulation channel, and the tie line power compensation term is obtained according to formula (2); on this basis, combined with the system frequency deviation, the active droop regulation amount on the fan side is formed through formula (3). The fan active support amount is composed of inertia response, frequency droop and tie line compensation, so as to quickly enhance the frequency support capability at the initial stage of disturbance.

[0044] Secondly, the active support mechanism under the SoC constraint is constructed on the energy storage side. The state of charge of the energy storage is dynamically updated according to formula (4); in order to prevent the energy storage from continuing to discharge at high power when the SoC is too low, the SoC limiting coefficient is introduced, the calculation of which is given by formula (5), and the coefficient is applied to the active output of the energy storage through formula (6), so that the energy storage can automatically adjust the output level according to the available energy to realize safe and continuous support. At the same time, voltage droop control is introduced into the reactive regulation channel of the doubly-fed fan and the energy storage, and the reactive output is automatically adjusted according to the grid connection point voltage deviation according to formula (7), so as to realize voltage stability support. In summary, the fan side and the energy storage side together form the active support reference amount of the distributed wind storage system (formula (8)).

[0045] On the basis of the above active support, the invention further constructs a double-frequency PSS for wide-frequency oscillation suppression. Due to the wind storage access, the system inertia and damping decrease at the same time, and there is strong coupling between the wind storage controller and the weak power grid, so the local power grid is easy to appear low-frequency and subsynchronous oscillation in the range of 0.2-40 Hz. Therefore, the invention designs two filter channels for low-frequency oscillation (0.2-2 Hz) and subsynchronous oscillation (10-40 Hz) respectively, and the core parameters are determined according to formula (9) and formula (10). According to the real-time identified oscillation frequency, the invention selects different PSS gain coefficients, in which is used in formula (11) for low-frequency mode, is used for subsynchronous mode, and the constraint relationship of avoiding over-compensation is met. The output of the PSS acts on the fan active channel and the energy storage reactive channel respectively through formula (12), providing double-channel wide-frequency damping capability for the system.

[0046] Further, the application unifies the active support amount and the damping control amount into a virtual synchronous machine (VSG) framework. The active and reactive power reference values of the wind storage system are superimposed by the planned power and the incremental support amount, and the expression is shown in formula (13)-(15). The VSG rotor motion equation is described by formula (14), which comprehensively considers inertia, damping and actual electromagnetic power feedback, so that the wind storage system has dynamic characteristics similar to synchronous machines; the reactive-voltage support relationship is given by formula (15), which can realize the rapid response of the wind storage system to voltage disturbance. Through the VSG unified coordination of the inertia and droop of the wind turbine, the rapid regulation of the energy storage and the wide-frequency damping of the PSS, the application finally forms a frequency-voltage-damping coordinated active support control framework, and the overall characteristics are described by formula (16).

[0047] To verify the effectiveness of the distributed wind storage active support control method, the above-mentioned IEEE 39-node, distributed wind storage system integrated simulation model is built on the MATLAB / Simulink platform, and the following larger disturbance conditions are set: at the simulation time s, an active load sudden increase is applied at node 15 to simulate the scene of a larger disturbance in the local power grid, and the total simulation time is 80 s The simulation results show that: under condition (1), the fault point frequency and voltage oscillate obviously, the lowest frequency point is deep, the recovery time is long, and the low-frequency and subsynchronous oscillation decays slowly; under condition (2), the oscillation of the frequency band is suppressed, but the fault point frequency recovers slowly; under condition (3), the fault point frequency curve is shown in Figure 3 , the frequency drop amplitude is obviously reduced, and the recovery speed is significantly accelerated; the voltage response is shown in Figure 4 , the fault point voltage oscillation is effectively suppressed; the wind storage active output is shown in Figure 5 , the wind turbine releases rotor kinetic energy through tie-line power control, and the energy storage realizes sustainable active and reactive support through the SoC limiting coefficient ; the synchronous generator speed and tie-line power are shown in Figure 6 and Figure 7 , the oscillation amplitude and duration are obviously reduced, the system synchronous angle stability margin and primary frequency modulation capacity are significantly improved.

[0048] As can be seen from the above embodiments, the frequency and voltage active support control method based on the distributed wind storage system can coordinate the active and reactive hybrid output of the wind turbine and the energy storage under large disturbance conditions, effectively suppress the wide-frequency oscillation of the local power grid, reduce the frequency valley and voltage drop during the fault, shorten the oscillation duration, and significantly improve the transient stability and operation safety of the weak end power grid.

[0049] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An automatic active support control method considering the suppression of broadband oscillations in the local power grid, characterized in that, The specific implementation steps are as follows: (a) Active support for wind-storage systems considering local grid interconnection power and energy storage SoC status: Establishing active support for the wind-storage system includes the following active power control components: enabling the wind-storage integrated system to coordinate and provide frequency and voltage regulation; through additional control strategies, enabling wind turbines and energy storage to provide active frequency and voltage support to the grid; considering tie-line power variations, adjusting the droop control output of the wind turbines based on frequency deviations and tie-line power variations; considering the energy storage SoC status, regulating the active power output of the energy storage droop control; and integrating the above active power control components to implement active support control for the distributed wind-storage system. (ii) Dual-band PSS design considering local power grid frequency and voltage broadband oscillation: Positive damping is provided by PSS in the low-frequency and subsynchronous frequency bands to suppress local power grid oscillations; the time constant of the dual-band PSS is designed according to the oscillation frequency. The damping coefficient for suppressing local grid frequency oscillations is selected based on the damping coefficient of the oscillation frequency. Considering the wide-band oscillations of local grid frequency and voltage, power control for distributed wind-storage oscillation suppression is implemented. (III) Automatic active support control considering local power grid broadband oscillation suppression: Real-time acquisition of local power grid frequency deviation, frequency change rate, voltage deviation and tie line power signal, and suppression of oscillation modes in different frequency bands through dual-band PSS; At the same time, based on virtual inertia and droop control mechanism, wind turbine and energy storage jointly regulate active / reactive output to quickly support local power grid frequency and voltage; Tie line power control further enhances the dynamic coordination capability between regions.

2. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (one), through additional control strategies, the wind turbine generator and energy storage can provide active frequency and voltage support to the power grid, specifically as follows: Introducing frequency change rate control into the active power circuit of a doubly-fed induction generator enables rapid output adjustment during disturbances, allowing it to exhibit inertial characteristics similar to a synchronous generator. The formula is as follows: (1)； In the formula, P wind1 The active power output by the wind turbine in response to changes in the system frequency; K wind_J The inertia coefficient of the fan. J This represents the virtual inertia of the wind turbine. f Indicates the system frequency.

3. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (one), considering the power variation of the tie line, the fan adjusts the droop control output according to the frequency deviation and the power variation of the tie line, specifically as follows: Considering the power variation of the tie line: (2)； Where, Δ P tl Wiring line power regulation error signal P tl * For the planned active power of the tie line, P tl This represents the actual active power of the tie line. The fan adjusts its droop control output based on frequency deviation and changes in tie line power. (3)； In the formula, P wind2 For adjusting the active power output to control the droop of the wind turbine; f, f ref These are the system frequency and the system frequency reference value, respectively. K wind2 ，K wind_tl For the frequency droop factor and the tie line power droop factor, respectively.

4. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (one), considering the energy storage SoC state, the active power output is adjusted by energy storage droop control, specifically as follows: During the active support process of energy storage systems, their sustainable support capability is directly limited by the System-on-Chips (SoC). The SoC calculation for energy storage power stations is as follows: (4)； In the formula, SOC i For energy storage power stations i SoC value; SOC 0 Initial values ​​for the SoC; S rated Indicates the power reference value. η To improve the charging and discharging efficiency of energy storage; I t For output current; A constraint coefficient reflecting the remaining energy level of the energy storage is constructed, enabling its output power to adaptively adjust with changes in the System-on-Chips (SoC), ensuring the safety of energy storage operation and achieving dynamic matching between support capacity and available energy; an SoC constraint coefficient is introduced. K SOC This is used to uniformly quantify and limit the maximum output power of energy storage, and its expression is as follows: (5)； In the formula, K soc This refers to the energy storage power support coefficient. SOC max， SOC min These represent the maximum and minimum values ​​of the energy storage SoC, respectively. Energy storage droop control for active power output regulation: (6)； in, K ES The frequency response gain coefficient of the energy storage system. f For the system's real-time operating frequency, f ref This is the system frequency reference value. K ES_tl Δ is the gain coefficient of the tie-line power regulation channel. P tl Connection line power regulation error signal.

5. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (one), the distributed wind-storage system actively supports control by integrating the above-mentioned active power control links, specifically as follows: (7)； In the formula, P wind1 The active power output by the wind turbine in response to changes in the system frequency; P wind2 For adjusting the active power output to control the droop of the wind turbine; P WPESS_ref ，Q WPESS_ref Provides active power reference values ​​and reactive power reference values ​​for distributed wind storage systems; K q It represents the reactive voltage droop control coefficient, which is used to characterize the sensitivity of reactive power in a distributed wind power storage system to voltage deviation. U This indicates the real-time voltage amplitude at the grid connection point of the distributed wind-storage system; U 0 This indicates the system's rated operating voltage or a set voltage reference value, used as a benchmark for reactive power voltage control.

6. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (ii), a PSS is designed in both the low-frequency and subsynchronous frequency bands to provide positive damping and suppress local power grid oscillations; the time constant of the dual-band PSS is designed according to the oscillation frequency, specifically as follows: (8)； in, f mode The currently identified oscillation frequency is determined based on the system's small-signal stability analysis or online modal identification results; A function for compensating for phase; for PSS#1 of dual-band PSS, the following is adopted: f mode =f i ∈[0.2, 2] For PSS#2 of dual-band PSS, the following is adopted: f mode =f j ∈[10, 40] The time constant of the PSS lead-lag element is used to control the operating frequency of the damper.

7. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (ii), the PSS (Power Supply System) for suppressing local grid frequency oscillations is connected to the wind turbine, and the damping coefficient for suppressing voltage oscillations is connected to the energy storage system. The selection is based on the damping coefficient of the oscillation frequency. (9)； in, The gain coefficient of the designed power system stabilizer (PSS) is used to adjust the additional damping capability of the wind turbine or energy storage converter under specific oscillation modes. This indicates the PSS gain used to suppress low-frequency oscillations, generally corresponding to electromechanical oscillation modes of 0.2–2 Hz, and is PSS#1 used for dual-band PSS. This represents the PSS gain used to suppress subsynchronous oscillations, typically corresponding to the oscillation frequency band of 10–40 Hz. It is used for PSS#2 in dual-band PSS, and to avoid overcompensation of low-frequency damping, it usually satisfies… Design requirements; when When this occurs, it indicates that the system is in a low-frequency oscillation mode caused by electromechanical coupling between generator sets. In this case, the gain is selected... ;when When this occurs, it indicates subsynchronous frequency band oscillation caused by the influence of the power electronic interface or the flexibility of the transmission line. In this case, the gain is selected... ;in, , These are the center frequencies or typical oscillation frequencies of the low-frequency mode and the subsynchronous mode, respectively. Power control for distributed wind-storage oscillation suppression: (10)； in, This represents the additional damping power based on PSS provided by the wind turbine in the active power channel; This indicates the additional damping reactive power provided by the energy storage device in the reactive power channel; together, they constitute the active-reactive dual-channel damping output in the distributed wind-storage oscillation suppression strategy. variable and These are the transfer functions of two dampers acting in the active power channel of the wind turbine, which usually correspond to the PSS filter structure of PSS#1 and PSS#2. They are in the form of a lead-lag element or a bandpass filter element, used to provide the required phase lead and amplitude gain near the target oscillation frequency. The two are superimposed to form the comprehensive damping characteristics of the active side of the wind turbine. variable and These are the transfer functions of the two dampers acting on the reactive power channel of the energy storage. The structure is similar to that of the active side, but the frequency band arrangement focuses more on voltage oscillation and high-frequency modes, so that the energy storage converter can provide fast reactive power compensation on the voltage side.

8. The automatic active support control method considering local power grid broadband oscillation suppression as described in claim 1, characterized in that: In step (iii), the active support control method for the distributed wind-storage system, which considers the suppression of broadband oscillations in the local power grid, is specifically as follows: (11)； (12)； in, and These represent the active and reactive power reference values ​​output by the virtual synchronous machine control unit, respectively, which are used to adjust the active support capability of the wind-storage combined system under frequency disturbances and voltage deviations. The active and reactive power reference values ​​are composed of the superposition of planned power and incremental support. and These are the planned active power and planned reactive power of a distributed wind power-energy storage system under normal operating conditions, which are usually obtained from scheduling plans, power predictions or steady-state optimizations, and are used as the benchmark setpoints for the operation of the wind-storage system. The incremental active power support generated by the VSG controller based on the local power grid frequency deviation, frequency change rate, and tie-line power deviation typically includes droop adjustment terms, inertia response terms, and tie-line coordinated adjustment terms, which are used to enhance the system's active power regulation capability against disturbances and suppress frequency offset and oscillation. The incremental reactive power support generated by the VSG controller based on the grid connection point voltage deviation and voltage dynamic characteristics may include voltage droop adjustment and voltage change rate adjustment terms, which are used to improve local voltage support capability and suppress voltage oscillation and high-frequency resonance risks. (13)； (14)； in, The equivalent rotational inertia constant of VSG is used to characterize the inertial response capability of the wind-storage system under frequency disturbances. The active power reference value generated for the VSG control unit is usually obtained by superimposing the planned active power with the incremental support power based on factors such as frequency deviation and tie-line power deviation. The electromagnetic active power actually output by the wind-storage system to the grid is the feedback quantity in the active power balance constraint; variable The instantaneous angular frequency of the output voltage of the virtual synchronous machine. The rated angular frequency; the difference between the two. Characterizing system frequency shift; coefficients is the equivalent damping coefficient, used to simulate the natural damping effect of the synchronous machine damping winding and speed control system on frequency changes. The larger its value, the higher the oscillation decay rate; in equation (14), This refers to the reactive power output of the wind-storage system. The reactive power reference value generated by the VSG controller is typically composed of the planned reactive power and the incremental reactive power support based on voltage deviation; variables This represents the actual voltage at the grid connection point of the wind-storage system. The difference between the rated voltage or the given voltage reference value. Characterizes the voltage offset at the grid connection point; parameters This is the reactive voltage droop factor, which physically represents the sensitivity of reactive power output to voltage changes. This determines the reactive power regulation range of the VSG in response to voltage disturbances.

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