A pumped storage unit frequency support method and device

Abstract

This application provides a frequency support method and apparatus for a pumped storage hydroelectric unit. The unit includes a flexible DC excitation system with energy storage-type fully controlled devices. The method includes: determining the state of charge (SOC) of the energy storage device based on its energy storage parameters; calculating the energy stored in the energy storage device based on its SOC and voltage parameters; determining the frequency differential control coefficient and droop control coefficient of the excitation system based on the SOC, energy storage parameters, and stored energy; obtaining the frequency deviation and frequency change rate of the power grid; and determining the frequency support strategy provided by the unit to the power grid based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient. By coordinating the control of the pump turbine and excitation system to participate in frequency regulation, the frequency regulation performance of the unit can be improved, ensuring the stable operation of the power system.

Description

Technical Field

[0001] This application relates to the field of pumped storage technology, and in particular to a method and apparatus for frequency support of pumped storage units. Background Technology

[0002] In new power systems, energy storage is a key technology for promoting the integration and consumption of a high proportion of renewable energy. Pumped storage units have the advantages of fast start-up and shutdown, large energy storage capacity, and high reliability, and have significant advantages in solving the frequency security problems faced by power systems.

[0003] The regulation system of a pumped-storage hydroelectric unit includes a pump-turbine speed control system and a generator-motor excitation system. The speed control system adjusts the unit's speed and active power by controlling the turbine's guide vane opening, enabling the unit to participate in grid frequency regulation. The thyristor-based excitation system controls the unit's voltage and reactive power but lacks active power regulation capabilities. Due to the operating characteristics of the pump-turbine, pumped-storage hydroelectric units can only adjust their output in real-time during power generation; they are essentially unable to dynamically adjust active power during pumping, severely limiting their frequency regulation capabilities. Furthermore, because the pump-turbine has a large inertial response time constant and a frequency regulation dead zone, the output of pumped-storage hydroelectric units struggles to keep pace with power fluctuations in renewable energy units, requiring improvement in active power regulation speed. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a frequency support method and apparatus for pumped storage units to solve the problem of insufficient frequency regulation capability of the units.

[0005] Based on the above objectives, this application provides a frequency support method for a pumped storage unit, the unit including a flexible DC excitation system with energy storage-type fully controlled devices, and the method includes:

[0006] The state of charge of the energy storage device is determined based on the energy storage parameters of the excitation system.

[0007] The energy stored in the energy storage device is calculated based on its state of charge and voltage parameters.

[0008] Based on the state of charge, energy storage parameters, and stored energy, determine the frequency differential control coefficient and droop control coefficient of the excitation system;

[0009] Obtain the frequency deviation and frequency change rate of the power grid;

[0010] Based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient, the frequency support strategy provided by the generating unit to the grid is determined.

[0011] Optionally, the energy storage device includes a battery bank and a supercapacitor bank; the state of charge of the energy storage device is determined based on the energy storage parameters of the excitation system, using the following method:

[0012]

[0013] Among them, S SOC Q represents the state of charge of the energy storage device. N S represents the rated capacity of the energy storage device. SOC_bat For the state of charge of the battery pack, S SOC_sc Q represents the state of charge of the supercapacitor bank. bat Q is the rated capacity of the battery pack. sc Q is the rated capacitance of the supercapacitor bank. B This refers to the remaining capacity of the energy storage device;

[0014] The energy stored in the energy storage device is calculated based on its state of charge and voltage parameters. The method is as follows:

[0015] E B =u N Q N S SOC (2)

[0016] Among them, E B For the energy of the energy storage device, u N This is the rated voltage of the energy storage device.

[0017] Optionally, the frequency differential control coefficients of the excitation system are determined based on the state of charge, energy storage parameters, and stored energy, using the following method:

[0018]

[0019] Among them, K d Rocof is the frequency differential control coefficient. max t is the maximum allowable rate of change of frequency for the system. dmax S represents the maximum duration of the inertial response of the energy storage device. SOCmax S represents the maximum state of charge of the energy storage device. SOCmin This represents the minimum state of charge of the energy storage device.

[0020] Optionally, the droop control coefficient of the excitation system is determined based on the state of charge, energy storage parameters, and stored energy, using the following method:

[0021]

[0022] in,

[0023] Among them, K BLet λ, a, and b be the droop control coefficients of the excitation system, and P be the coefficients of the Logistic function. BN Let f be the rated power of the energy storage device, σ* be the droop coefficient of the energy storage device, and f be the rated power of the energy storage device. N Δf is the rated frequency of the power grid, and Δf is the frequency deviation of the power grid.

[0024] Optionally, based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient, a frequency support strategy for the unit to supply to the grid is determined, including:

[0025] When the product of the frequency deviation and the frequency change rate is positive, the unit provides active inertia support to the power grid through the excitation system; wherein, the excitation system provides active inertia support based on the frequency differential control coefficient and the frequency change rate;

[0026] When the frequency deviation is outside the primary frequency regulation dead zone, the unit participates in grid frequency regulation through the water pump turbine or excitation system.

[0027] Optionally, determine the frequency support strategy provided by the generating unit to the grid, including:

[0028] When the unit is in power generation mode, the synchronous generator of the unit provides inertial support, and the water pump turbine participates in the primary frequency regulation of the power grid, while the excitation system provides active inertial support.

[0029] When the unit is in pumping mode, the synchronous motor of the unit provides inertial support, the water pump turbine does not participate in frequency regulation, the excitation system provides active inertial support, and participates in primary frequency regulation according to the droop control coefficient and frequency deviation.

[0030] Optionally, when the unit is in generating mode, the frequency regulation power command set for the unit is:

[0031]

[0032] Wherein, ΔP ref For pumped storage units, the frequency regulation power command is ΔP. B For the frequency regulation power command of the energy storage device in the excitation system, ΔP H For the frequency regulation power command of the water pump turbine, K d K represents the frequency differential control coefficient of the excitation system. H Δf is the primary frequency regulation droop control coefficient of the water pump turbine; Δf is the frequency deviation, df / dt is the rate of frequency change, and f is the frequency deviation. thr This is a frequency modulation dead zone.

[0033] Optionally, when the unit is in pumping mode, the set frequency regulation power command for the unit is:

[0034]

[0035] Wherein, ΔP B For the frequency regulation power command of the energy storage device in the excitation system, ΔP B1 The active inertia support power command for the energy storage device of the excitation system, ΔP B2 K is the primary frequency regulation power command for the energy storage device of the excitation system. d K represents the frequency differential control coefficient of the excitation system. B denoted as the droop control coefficient of the excitation system, Δf as the frequency deviation, and df / dt as the frequency change rate.

[0036] Optionally, the method further includes:

[0037] Establish a cycle life consumption model for the energy storage device;

[0038] The optimal power distribution between the battery pack and the supercapacitor pack in the energy storage device is determined by solving the cycle life consumption model using a preset algorithm.

[0039] This application embodiment also provides a frequency support device for a pumped storage unit, the unit including a flexible DC excitation system with energy storage-type fully controlled devices, and the device including:

[0040] The charge calculation module is used to determine the state of charge of the energy storage device based on the energy storage parameters of the energy storage device in the excitation system.

[0041] The energy calculation module is used to calculate the energy stored in the energy storage device based on the state of charge and voltage parameters of the energy storage device.

[0042] The coefficient calculation module is used to determine the frequency differential control coefficient and droop control coefficient of the excitation system based on the state of charge, energy storage parameters and stored energy.

[0043] The acquisition module is used to acquire the frequency deviation and frequency change rate of the power grid;

[0044] The strategy determination module is used to determine the frequency support strategy provided by the generating unit to the grid based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient.

[0045] As can be seen from the above, the pumped storage unit frequency support method and apparatus provided in this application determine the state of charge (SOC) of the energy storage device based on the energy storage parameters of the energy storage device in the flexible DC excitation system of the energy storage-type fully controlled device; calculate the energy stored in the energy storage device based on the SOC and voltage parameters; determine the frequency differential control coefficient and droop control coefficient of the excitation system based on the SOC, energy storage parameters, and stored energy; obtain the frequency deviation and frequency change rate of the power grid; and determine the frequency support strategy provided by the unit to the power grid based on the frequency deviation and frequency change rate. This application can solve the problem that the unit cannot participate in frequency regulation under pumping conditions. By coordinating the control of the pump turbine and excitation system to participate in frequency regulation, the frequency regulation performance of the unit can be improved, ensuring the stable operation of the power system. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the excitation system structure according to an embodiment of this application;

[0048] Figure 2 This is a partial structural schematic diagram of the excitation system according to an embodiment of this application;

[0049] Figure 3 This is a schematic diagram of the method flow of an embodiment of this application;

[0050] Figure 4 This is a schematic diagram of the frequency regulation control principle under power generation conditions in an embodiment of this application;

[0051] Figure 5 This is a schematic diagram of the frequency modulation control principle under pumping conditions in an embodiment of this application;

[0052] Figure 6 This is a schematic diagram of the droop control coefficient as a function of state of charge in an embodiment of this application.

[0053] Figure 7 This is a block diagram of the device structure according to an embodiment of this application;

[0054] Figure 8 This is a block diagram of the electronic device structure according to an embodiment of this application. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0056] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0057] In related technologies, pumped storage units can participate in grid frequency regulation, but their frequency regulation capability is significantly limited by the operating characteristics of pump-turbine units. The flexible DC excitation system with energy storage-type fully controlled devices connects an energy storage device in parallel with the power electronic converter section. This allows for the adjustment of excitation voltage, grid-side reactive power, and active power, which is beneficial for the stable operation of the power system and provides a possibility for improving the frequency regulation performance of pumped storage units.

[0058] In view of this, the embodiments of this application provide a frequency support method and device for pumped storage units, which realizes the frequency regulation control of the unit participating in the power grid based on the flexible DC excitation system of energy storage type fully controlled devices. This can solve the problem that the unit cannot participate in frequency regulation under pumping conditions, improve the frequency regulation performance of the unit, and ensure the stable operation of the power system.

[0059] The technical solution of this application will be further described in detail below through specific embodiments.

[0060] like Figure 1 , 2 As shown, the pumped storage unit in this embodiment of the application includes a flexible DC excitation system with energy storage type fully controlled devices. The excitation system includes an excitation system controller, an energy storage device, an excitation transformer, and a power converter. The excitation transformer is connected to the synchronous motor terminals to supply power to the excitation system.

[0061] The excitation system controller comprises an upper-level control section and a main circuit control section. The upper-level control section includes a voltage control module, a damping control module, a frequency control module, and an energy storage power optimization allocation module. The frequency control module calculates the frequency deviation and rate of change based on the acquired grid frequency, and determines the frequency regulation power command for the generating unit to participate in frequency regulation based on the frequency deviation and rate of change. The energy storage power optimization allocation module determines the optimal output allocation of different energy storage units in the energy storage device based on the determined frequency regulation power command, so that the energy storage device injects or absorbs active power into the grid according to the optimal output allocation, achieving inertia support for the grid and / or primary frequency regulation. The voltage control module controls reactive power based on the acquired grid parameters to maintain grid voltage stability. The damping control module enhances the power system damping through the excitation and reactive power channels.

[0062] The main circuit control section includes a VSC control module, a chopper control module, and an energy storage charging / discharging control module. The VSC control module employs a direct power control method based on grid-side d-axis and q-axis decoupling to achieve independent control of the reactive and active power of the excitation system. The active current command value varies depending on the energy storage device mode; when the energy storage unit is operating, the voltage outer loop is eliminated, and the active current command value is provided by the active power controller. The chopper control module controls the excitation current by adjusting the chopper's duty cycle to regulate the excitation voltage. The energy storage charging / discharging control module controls the flow of active power between the energy storage device and the grid, as well as the rational distribution of active power among the various energy storage units within the energy storage device.

[0063] The power converter includes a grid-side AC / DC converter, a DC-side voltage regulator, and a DC / DC chopper. The AC / DC converter is a voltage source converter, including but not limited to two-level, three-level, and five-level multi-level structures. The voltage source converter controls the on / off state of its internal fully controlled components according to switching signals, enabling the direct absorption or injection of active or reactive power into the grid. The DC-side voltage regulator ensures DC-side voltage stability, providing a stable voltage source for the inverter to output reactive power to the grid and for the excitation current obtained from the chopper. The DC / DC chopper controls the on / off state of its internal fully controlled components according to switching signals, thereby controlling the generator's excitation current and indirectly absorbing or injecting reactive power into the grid through the generator.

[0064] The energy storage device is connected in parallel with the DC-side stabilizing capacitor of the power converter, sharing a voltage source converter with the power converter for grid connection, thereby achieving controllable active power injection at the generator end. The energy storage device includes battery banks and supercapacitor banks. The battery bank (BAT) is an energy-type energy storage unit with a long discharge time and high energy density, but a short cycle life; the supercapacitor bank (SC) is a power-type energy storage unit with a short continuous discharge time, high power density, and long cycle life. The two types of energy storage units complement each other well in terms of energy density and power density. The battery bank and the filter inductor (L) are also connected. bat The supercapacitor bank is connected in series with the DC-side voltage regulator capacitor C via the energy storage-side chopper converter; the supercapacitor bank is connected in parallel with the filter inductor L. sc The batteries are connected in series, and the energy storage-side chopper converter is connected in parallel with the DC-side voltage regulator C. By switching the devices on and off, the energy storage device is controlled to absorb or inject active power into the grid, and the optimal power output allocation between the battery bank and the supercapacitor bank is determined according to the established model.

[0065] like Figure 3 As shown in the figure, this application provides a method for frequency support of pumped storage units, including:

[0066] S301: Determine the state of charge of the energy storage device based on the energy storage parameters of the excitation system's energy storage device;

[0067] In this embodiment, various energy storage parameters of the energy storage device in the excitation system are obtained, and the current state of charge (SOC) of the energy storage device is calculated based on these parameters. The energy storage device is a hybrid energy storage device comprising a battery bank and a supercapacitor bank. The energy storage parameters of the hybrid energy storage device include the rated capacity and SOC of the battery bank, and the rated capacity and SOC of the supercapacitor bank. The method for calculating the SOC of the energy storage device is as follows:

[0068]

[0069] Among them, S SOC Q represents the state of charge of the energy storage device. N S represents the rated capacity of the energy storage device. SOC_bat For the state of charge of the battery pack, S SOC_sc Q represents the state of charge of the supercapacitor bank. bat Q is the rated capacity of the battery pack. sc Q is the rated capacitance of the supercapacitor bank. B This represents the remaining capacity of the energy storage device.

[0070] S302: Calculate the energy stored in the energy storage device based on the state of charge and voltage parameters of the energy storage device;

[0071] In this embodiment, after calculating the state of charge (SBC) of the energy storage device, the energy currently stored in the energy storage device is calculated based on the SBC and the rated voltage of the energy storage device. The calculation method is as follows:

[0072] E B =u N Q N S SOC (2)

[0073] Among them, E B For the energy of the energy storage device, u N This is the rated voltage of the energy storage device.

[0074] S303: Determine the frequency differential control coefficient and droop control coefficient of the excitation system based on the state of charge and the stored energy;

[0075] In this embodiment, after determining the current state of charge and stored energy of the energy storage device, the frequency differential control coefficient of the excitation system is determined based on the state of charge and stored energy. The method is as follows:

[0076]

[0077] Among them, K d Rocof is the frequency differential control coefficient. max t is the maximum allowable rate of change of frequency for the system. dmax S represents the maximum duration of the inertial response of the energy storage device. SOCmax S represents the maximum state of charge of the energy storage device. SOCmin This represents the minimum state of charge of the energy storage device.

[0078] Simultaneously, based on the state of charge of the energy storage device, energy storage parameters, and the droop coefficient of the generator set, the droop control coefficient of the excitation system is determined using the following method:

[0079]

[0080] in,

[0081] Formula (4) is the droop control coefficient K B It is set in the form of a Logistic function to avoid the depletion or saturation of the State of Charge (SOC) of the energy storage device, where λ, a, and b are the coefficients of the Logistic function, and P... BN Let f be the rated power of the energy storage device, σ* be the droop coefficient of the energy storage device, and f be the rated power of the energy storage device. N is the rated frequency of the power grid, and ×f is the frequency deviation of the power grid.

[0082] In some configurations, when the capacity of the energy storage device is configured to be 10% to 20% of the pumped storage unit capacity, the values ​​of each parameter can be K.BN =10, λ=0.01, a=13, b=0.5, S SOCmax =0.8, S SOCmin =0.2. For example... Figure 6 The curves shown represent the variation of the droop control coefficient with the state of charge. When the frequency deviation is greater than zero, the droop control coefficient decreases with the increase of the state of charge. When the frequency deviation is less than zero, the droop control coefficient increases with the increase of the state of charge.

[0083] S304: Obtain the frequency deviation and frequency change rate of the power grid;

[0084] S305: Determine the frequency support strategy provided by the generating unit to the grid based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient.

[0085] In this embodiment, the actual frequency value of the power grid is obtained from the frequency measurement device, the difference between the actual frequency value and the rated value is calculated to obtain the frequency deviation, and the frequency change rate of the power grid within a predetermined time is statistically analyzed. Based on the frequency deviation and frequency change rate of the power grid, the frequency state of the power grid is determined, and then the frequency support strategy that the pumped storage unit needs to provide to the power grid is determined.

[0086] In some implementations, the frequency support strategies that the generating unit can provide to the grid include:

[0087] When the product of frequency deviation and frequency change rate is positive, the unit provides active inertial support to the power grid through the excitation system based on the frequency differential control coefficient and frequency change rate.

[0088] When the frequency deviation is outside the primary frequency regulation dead zone, the unit participates in grid frequency regulation through the water pump turbine or excitation system.

[0089] In this embodiment, the product of frequency deviation Δf and frequency change rate df / dt is first calculated. If the product Δf×(df / dt)>0, the grid frequency is in the disturbance stage, and the frequency differential control loop of the energy storage device is activated. The unit provides active inertial support to the grid through the excitation system, which can quickly suppress grid frequency fluctuations and improve the stability of the power system. If the product Δf×(df / dt)≤0, the grid frequency is in the recovery stage, and the frequency differential control loop of the energy storage device is locked to avoid the energy storage device from generating negative power regulation on the grid. When the frequency deviation is outside the frequency regulation dead zone, i.e. Δf≤-f thr Or Δf≥f thr f thr As a primary frequency regulation dead zone, pumped storage units participate in grid frequency regulation through water pumps, turbines, or excitation systems.

[0090] When pumped storage units are operating under different conditions, the frequency support strategies that the units can provide to the grid include:

[0091] When the unit is in power generation mode, the synchronous generator provides inertial support, and the unit participates in the primary frequency regulation of the power grid through the pump turbine. The excitation system provides active inertial support. That is, in power generation mode, the unit participates in frequency regulation through the pump turbine, and the excitation system does not need to participate in frequency regulation. When the frequency of the power grid fluctuates greatly, the unit can not only provide inertial support through the synchronous generator, but also provide active inertial support through the excitation system. This can quickly suppress frequency fluctuations and ensure the stability of the power grid. The fact that the excitation system does not participate in the primary frequency regulation can reduce the energy consumption of the energy storage device.

[0092] When the unit is in pumping operation, the synchronous motor provides inertial support, the pump-turbine does not participate in frequency regulation, and the excitation system provides active inertial support and participates in primary frequency regulation. That is, under pumping conditions, considering the operating characteristics of the pump-turbine, the pump-turbine does not participate in frequency regulation; instead, the excitation system provides active inertial support and participates in primary frequency regulation. Because the energy storage device offers flexible control and a fast response time, the primary frequency regulation dead zone can be set to zero.

[0093] In some methods, when the unit is in generating mode, the frequency regulation power command set for the unit is:

[0094]

[0095] Wherein, ΔP ref For pumped storage units, the frequency regulation power command is ΔP. B For the frequency regulation power command of the energy storage device in the excitation system, ΔP H For the frequency regulation power command of the water pump turbine, K d K represents the frequency differential control coefficient of the excitation system. H This is the primary frequency regulation droop control coefficient for the water pump turbine.

[0096] like Figure 4 As shown, under power generation conditions, based on the actual frequency value f and the rated frequency f of the power grid... N The difference between the values ​​determines the frequency deviation Δf. When the frequency deviation Δf is outside the primary frequency regulation dead zone, the pump-turbine participates in frequency regulation, based on the primary frequency regulation droop control coefficient K of the pump-turbine. H The frequency deviation determines the frequency regulation power command ΔP of the water pump turbine. H When the product of frequency deviation and frequency change rate is positive, the energy storage device of the excitation system provides active inertia support, based on the frequency differential control coefficient K. d The frequency regulation power command ΔP of the energy storage device is determined by the rate of change of frequency. B .

[0097] In some methods, when the unit is in pumping mode, the frequency regulation power command set for the unit is:

[0098]

[0099] Wherein, ΔP B1 The active inertia support power command for the energy storage device of the excitation system, ΔP B2 K is the primary frequency regulation power command for the energy storage device of the excitation system. d K represents the frequency differential control coefficient of the excitation system. B This is the droop control coefficient for the excitation system.

[0100] like Figure 5 As shown, under pumping conditions, when the product of frequency deviation and frequency change rate is positive, the energy storage device of the excitation system provides active inertia support, based on the frequency differential control coefficient K. d The active inertia support power command ΔP of the energy storage device is determined by the frequency change rate df / dt. B1 Simultaneously, based on the droop control coefficient K of the excitation system... B The frequency deviation determines the primary frequency regulation power command ΔP for the energy storage device to participate in primary frequency regulation. B2 .

[0101] In some embodiments, the frequency support method for pumped storage units further includes:

[0102] Establish a cycle life consumption model for energy storage devices;

[0103] The optimal power distribution between the battery pack and the supercapacitor pack in the energy storage device is determined by solving the cycle life consumption model using a preset algorithm.

[0104] In this embodiment, the energy storage device of the excitation system is a hybrid energy storage device including a battery pack and a supercapacitor pack. In order to rationally allocate the output of the battery pack and the supercapacitor pack and reduce the cycle life loss of the hybrid energy storage device, a cycle life consumption model of the energy storage device is established. By solving the optimal solution of the model, the output allocation of the battery pack and the supercapacitor pack is determined, and the power allocation of the energy storage device is optimized.

[0105] In some approaches, the lifespan of energy storage devices is related to factors such as cyclic aging, operating temperature, and charge-discharge cycles. Frequent and deep cycle discharges accelerate the cyclic aging of energy storage devices and reduce their cycle life. By establishing a cycle life consumption model, the cycle life of energy storage devices can be predicted. Let t... i-1 and t i These are two adjacent charge / discharge transition times, in the interval [t]. i-1 , t i The depth of discharge (DOD) for the i-th charge-discharge cycle half-cycle is Di, which is calculated as follows:

[0106] D i=|S SOC (t i )-S SOC (t i-1 (7)

[0107] Among them, S SOC (t i-1 ) for energy storage devices at t i-1 The state of charge at time S SOC (t i ) for energy storage devices at t i The state of charge at any given moment.

[0108] Based on the discharge depth of the i-th charge-discharge cycle half-cycle, the corresponding equivalent number of full cycles can be obtained, calculated as follows:

[0109]

[0110] in, k represents the equivalent number of full cycles corresponding to the depth of discharge Di. A higher equivalent number of full cycles results in greater cycle life loss. p Let be the characteristic constant of the energy storage device, and k be the characteristic constant of the battery pack and the supercapacitor pack, respectively. p_bat and k p_sc .

[0111] The equivalent total cycle count of the battery pack in one day can be obtained as follows:

[0112]

[0113] in, is the equivalent full cycle number corresponding to the depth of discharge in the i-th half-cycle of the battery pack; j is the number of half-cycles of the battery pack recorded in a day.

[0114] Similarly, the equivalent total number of cycles of the supercapacitor bank in one day can be obtained. for:

[0115]

[0116] in, is the equivalent full cycle number corresponding to the discharge depth within the i-th half-cycle of the supercapacitor bank; l is the number of half-cycles of the supercapacitor bank recorded in one day.

[0117] When grid frequency fluctuations occur, the next frequency power command for the energy storage device cannot be determined. In order to decompose the equivalent full cycle number corresponding to the discharge depth within a half-cycle into each control cycle within the half-cycle, it is necessary to estimate the equivalent full cycle number corresponding to each control cycle. The estimation method is as follows:

[0118]

[0119] Where, d i,k Let ΔP be the depth of discharge of the energy storage device after k control cycles of duration Δt, starting from the end of the i-th half-cycle. B For frequency regulation power commands of energy storage devices; E B For the energy of the energy storage device, This represents the equivalent full cycle count within the (k+1)th control cycle.

[0120] If ΔP B A change in the sign of d indicates a change in the charging or discharging state of the energy storage device, i.e., a transition from a charging state to a discharging state or vice versa. Let d i,k =0, and update i and k, so that the value of i is incremented by 1 and the value of k returns to 1. Substitute the updated value into equation (11) and estimate the equivalent full cycle number corresponding to each control cycle according to the updated value.

[0121] Since different types of energy storage devices have different cycle lives, to reduce the cycle losses of hybrid energy storage devices, an objective function is established with the goal of minimizing the sum of the equivalent total cycle life losses of the hybrid energy storage device during each charge and discharge cycle:

[0122]

[0123] Among them, P bat For the power command of the battery pack to be optimized, P sc The power command for the supercapacitor bank to be optimized. To achieve a cycle life of 100% depth of discharge for the battery pack, To achieve a cycle life of 100% depth of discharge for supercapacitor banks; Let be the equivalent full cycle count of the battery pack during the k-th control cycle after the end of the i-th half-cycle. This represents the equivalent full cycle count of the supercapacitor bank during the k-th control cycle after the i-th half-cycle ends.

[0124] To ensure the safe operation of hybrid energy storage devices, the devices must meet power limit constraints and state-of-charge (SOC) operating range constraints, specifically as follows:

[0125]

[0126] Among them, P bat_max P represents the maximum charging and discharging power of the battery pack. sc_max S represents the maximum charging and discharging power of the supercapacitor bank. SOC_bat For the state of charge of the battery pack, S SOC_sc This refers to the state of charge of the supercapacitor bank.

[0127] To achieve frequency regulation, the sum of the power commands of the battery pack and the supercapacitor pack should equal the frequency regulation power command of the energy storage device, expressed as:

[0128] P bat +P sc =ΔP B (14)

[0129] To avoid energy exchange between different types of energy storage units in a hybrid energy storage device, the power direction of the hybrid energy storage device should satisfy the same-direction constraint:

[0130] P bat P sc ≥0 (15)

[0131] Therefore, based on the cycle life consumption model established by equation (12), and with (13)-(15) as constraints, the optimal solution of the cycle life consumption model is obtained by using a preset algorithm, and the output distribution P of the battery pack and supercapacitor pack in the hybrid energy storage device is determined. bat P sc Thus, according to the optimal output allocation P bat P sc Determining the output power of the battery pack and supercapacitor pack can reduce the cycle life loss of the energy storage device. Optionally, an improved particle swarm optimization algorithm can be used to solve the model; the specific method of improving the particle swarm optimization algorithm is not described or limited.

[0132] The frequency support method for pumped storage units provided in this application embodiment is based on a flexible DC excitation system of energy storage-type fully controlled devices. In power generation mode, the pump-turbine participates in grid frequency regulation, and the excitation system provides active inertia support. In pumping mode, the excitation system provides active inertia support and participates in primary frequency regulation. By coordinating the control of the pump-turbine and excitation system, the problem of the pump-turbine being unable to participate in frequency regulation under pumping mode can be solved, improving the unit's frequency regulation performance. The active inertia support provided by the excitation system can quickly suppress frequency fluctuations and ensure grid stability.

[0133] It should be noted that the method in this embodiment can be executed by a single device, such as a computer or server. The method can also be applied in a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method in this embodiment, and the multiple devices will interact with each other to complete the method described.

[0134] It should be noted that the above description describes specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims may be performed in a different order than that shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0135] like Figure 7 As shown in the embodiment of this application, a frequency support device for a pumped storage unit is also provided, comprising:

[0136] The charge calculation module is used to determine the state of charge of the energy storage device based on the energy storage parameters of the energy storage device in the excitation system.

[0137] The energy calculation module is used to calculate the energy stored in the energy storage device based on the state of charge and voltage parameters of the energy storage device.

[0138] The coefficient calculation module is used to determine the frequency differential control coefficient and droop control coefficient of the excitation system based on the state of charge, energy storage parameters and stored energy.

[0139] The acquisition module is used to acquire the frequency deviation and frequency change rate of the power grid;

[0140] The strategy determination module is used to determine the frequency support strategy provided by the generating unit to the grid based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient.

[0141] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing the embodiments of this application, the functions of each module can be implemented in one or more software and / or hardware.

[0142] The apparatus described above is used to implement the corresponding methods in the foregoing embodiments and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0143] Figure 8 This embodiment illustrates a more specific hardware structure of an electronic device, which may include a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, memory 1020, input / output interface 1030, and communication interface 1040 are interconnected internally via the bus 1050.

[0144] The processor 1010 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0145] The memory 1020 can be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program code is stored in the memory 1020 and is called and executed by the processor 1010.

[0146] The input / output interface 1030 is used to connect input / output modules to realize information input and output. Input / output modules can be configured as components within the device (not shown in the figure) or externally connected to the device to provide corresponding functions. Input devices may include keyboards, mice, touchscreens, microphones, various sensors, etc., while output devices may include displays, speakers, vibrators, indicator lights, etc.

[0147] The communication interface 1040 is used to connect a communication module (not shown in the figure) to enable communication between this device and other devices. The communication module can communicate via wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.).

[0148] Bus 1050 includes a pathway for transmitting information between various components of the device, such as processor 1010, memory 1020, input / output interface 1030, and communication interface 1040.

[0149] It should be noted that although the above-described device only shows the processor 1010, memory 1020, input / output interface 1030, communication interface 1040, and bus 1050, in specific implementations, the device may also include other components necessary for normal operation. Furthermore, those skilled in the art will understand that the above-described device may only include the components necessary for implementing the embodiments of this specification, and not necessarily all the components shown in the figures.

[0150] The electronic devices described above are used to implement the corresponding methods in the foregoing embodiments and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0151] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0152] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0153] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this application, the well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of the implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the embodiments of this application can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0154] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0155] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this disclosure.

Claims

1. A pumped storage plant frequency support method, characterized by, The unit includes a flexible DC excitation system with energy storage-type fully controlled devices, and the method includes: The state of charge of the energy storage device is determined based on the energy storage parameters of the excitation system. The energy stored in the energy storage device is calculated based on its state of charge and voltage parameters. Based on the state of charge, energy storage parameters, and stored energy, determine the frequency differential control coefficient and droop control coefficient of the excitation system; Obtain the frequency deviation and frequency change rate of the power grid; Based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient, the frequency support strategy provided by the generating unit to the grid is determined, including: When the product of the frequency deviation and the frequency change rate is positive, the unit provides active inertia support to the power grid through the excitation system; wherein, the excitation system provides active inertia support based on the frequency differential control coefficient and the frequency change rate; When the frequency deviation is outside the primary frequency regulation dead zone, the unit participates in grid frequency regulation through the water pump turbine or excitation system; When the unit is in power generation mode, the synchronous generator of the unit provides inertial support, and the water pump turbine participates in the primary frequency regulation of the power grid, while the excitation system provides active inertial support. When the unit is in pumping mode, the synchronous motor of the unit provides inertial support, the water pump turbine does not participate in frequency regulation, the excitation system provides active inertial support, and participates in primary frequency regulation according to the droop control coefficient and frequency deviation.

2. The method of claim 1, wherein, The energy storage device includes a battery bank and a supercapacitor bank; the state of charge of the energy storage device is determined based on the energy storage parameters of the excitation system, using the following method: （1） in, The state of charge of the energy storage device. The rated capacity of the energy storage device, The state of charge of the battery pack. This refers to the state of charge of the supercapacitor bank. The rated capacity of the battery pack. This refers to the rated capacity of the supercapacitor bank. This refers to the remaining capacity of the energy storage device; The energy stored in the energy storage device is calculated based on its state of charge and voltage parameters. The method is as follows: （2） in, For the energy of the energy storage device, This is the rated voltage of the energy storage device.

3. The method according to claim 2, characterized in that, The frequency differential control coefficients of the excitation system are determined based on the state of charge, energy storage parameters, and stored energy, using the following method: （3） in, These are the frequency differential control coefficients. This represents the maximum allowable rate of change of frequency for the system. This represents the maximum duration of the inertial response of the energy storage device. This represents the maximum state of charge of the energy storage device. This represents the minimum state of charge of the energy storage device.

4. The method according to claim 2, characterized in that, The droop control coefficient of the excitation system is determined based on the state of charge, energy storage parameters, and stored energy, using the following method: （4） in, This represents the droop control coefficient of the excitation system. These are the coefficients of the Logistic function. The rated power of the energy storage device. This is the droop coefficient of the energy storage device. The rated frequency of the power grid. This represents the frequency deviation of the power grid.

5. The method according to claim 1, characterized in that, When the unit is in generating mode, the frequency regulation power command set for the unit is: （5） in, This is the frequency regulation power command for pumped storage units. This is the frequency regulation power command for the energy storage device of the excitation system. This is the frequency regulation power command for the water pump turbine. Here are the frequency differential control coefficients of the excitation system. This is the primary frequency regulation droop control coefficient for the water pump turbine; For frequency deviation, The rate of change of frequency, This is a frequency modulation dead zone.

6. The method according to claim 1, characterized in that, When the unit is in pumping operation, the set frequency regulation power command is: （6） in, This is the frequency regulation power command for the energy storage device of the excitation system. The active inertia support power command for the energy storage device of the excitation system. This is the primary frequency regulation power command for the energy storage device of the excitation system. Here are the frequency differential control coefficients of the excitation system. This represents the droop control coefficient of the excitation system. For frequency deviation, This represents the rate of change of frequency.

7. The method according to claim 1, characterized in that, Also includes: Establish a cycle life consumption model for the energy storage device; The optimal power distribution between the battery pack and the supercapacitor pack in the energy storage device is determined by solving the cycle life consumption model using a preset algorithm.

8. A frequency support device for a pumped storage unit, characterized in that, The unit includes a flexible DC excitation system with energy storage-type fully controlled devices, and the equipment includes: The charge calculation module is used to determine the state of charge of the energy storage device based on the energy storage parameters of the energy storage device in the excitation system. The energy calculation module is used to calculate the energy stored in the energy storage device based on the state of charge and voltage parameters of the energy storage device. The coefficient calculation module is used to determine the frequency differential control coefficient and droop control coefficient of the excitation system based on the state of charge, energy storage parameters and stored energy. The acquisition module is used to acquire the frequency deviation and frequency change rate of the power grid; The strategy determination module is used to determine the frequency support strategy provided by the generating unit to the power grid based on the frequency deviation, frequency change rate, frequency differential control coefficient, and droop control coefficient. This includes: when the product of the frequency deviation and the frequency change rate is positive, the generating unit provides active inertia support to the power grid through the excitation system; wherein the excitation system provides active inertia support based on the frequency differential control coefficient and the frequency change rate; when the frequency deviation is outside the primary frequency regulation dead zone, the generating unit participates in grid frequency regulation through the pump-turbine or the excitation system; when the generating unit is in generating mode, the unit's synchronous generator provides inertia support, participates in primary grid frequency regulation through the pump-turbine, and the excitation system provides active inertia support; when the generating unit is in pumping mode, the unit's synchronous motor provides inertia support, the pump-turbine does not participate in frequency regulation, the excitation system provides active inertia support, and participates in primary frequency regulation based on the droop control coefficient and the frequency deviation.

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