Primary frequency modulation control method and device based on flywheel energy storage system

Abstract

The invention discloses a primary frequency modulation control method and device based on a flywheel energy storage system, and the method and device are applied to the flywheel energy storage system, and the method comprises the steps: obtaining the frequency deviation of a power system; if the frequency deviation is greater than or equal to a frequency deviation threshold, determining an adaptive control coefficient based on the frequency deviation and a change rate of the frequency deviation, and further determining a first active reference signal according to the adaptive control coefficient and the change rate of the frequency deviation; and performing primary frequency modulation control on the power system based on the first active reference signal. The invention provides a primary frequency modulation control strategy based on a flywheel energy storage system, and the beneficial effect of improving the stability of a power system is achieved.

Description

Technical Field

[0001] The present invention relates to a primary frequency modulation control strategy, and in particular to a primary frequency modulation control method and device based on a flywheel energy storage system. Background Art

[0002] With the large-scale access of new energy sources such as solar energy and wind energy to the power grid and the retirement of traditional thermal power units, new energy has gradually become an important part of the new installed capacity of the power system. New energy power electronic devices have the characteristics of low inertia and low interference immunity, and the proportion of traditional units with high inertia continues to decline, resulting in a decrease in the stability of the system frequency and an increase in the risk of frequency over-limit. When the system is disturbed, the frequency change rate is large and the lowest frequency point is low, which poses a challenge to the safe and stable operation of the power grid. Traditional frequency regulation methods have a slow response speed and cannot meet the new requirements of new power systems with strong volatility for frequency stability. At present, there is an urgent need for an effective frequency regulation method to improve the stability of the power system. Summary of the invention

[0003] In order to solve at least one technical problem in the above-mentioned background technology, the present invention proposes a primary frequency modulation control method and device based on a flywheel energy storage system.

[0004] In order to achieve the above object, according to one aspect of the present invention, a primary frequency modulation control method based on a flywheel energy storage system is provided, the method is applied to the flywheel energy storage system, and the method comprises:

[0005] Obtain frequency deviation of power system;

[0006] If the frequency deviation is greater than or equal to a frequency deviation threshold, determining an adaptive control coefficient based on the frequency deviation and a rate of change of the frequency deviation, and further determining a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation;

[0007] A frequency modulation control is performed on the power system based on the first active power reference signal.

[0008] Optionally, the primary frequency modulation control method based on the flywheel energy storage system further includes:

[0009] If the frequency deviation is less than the frequency deviation threshold, a second active reference signal is calculated according to the current flywheel charge state, and then self-recovery control is performed on its own flywheel charge state according to the second active reference signal.

[0010] Optionally, the performing a frequency modulation control on the power system based on the first active power reference signal includes:

[0011] Based on the first active reference signal and by applying model predictive control, a frequency modulation control is performed on the power system.

[0012] Optionally, the performing a frequency modulation control on the power system based on the first active reference signal and applying model predictive control includes:

[0013] Using the first active reference signal as an optimization target of the model predictive control;

[0014] The optimal power control command is obtained by solving the objective function to minimize the optimization target while satisfying the physical constraints of the flywheel energy storage system;

[0015] The power control instruction is converted into a control signal of the converter, and the converter is then controlled based on the control signal.

[0016] Optionally, the mathematical model of the flywheel energy storage system used in the model predictive control is:

[0017] dψ d / dt=(R s i d -ω e ψ q ) / L s

[0018] dψ q / dt=(R s i q +ω e ψ d ) / L s

[0019] dω e / dt=(Te-T L ) / J

[0020]

[0021] Where, the subscripts d and q are the components of the two-phase rotating coordinate system in the d and q directions; ψ is the stator flux of the motor; R s is the stator winding resistance of the motor; ω e is the angular velocity of the motor rotor; i is the current of the motor; L s is the synchronous inductance; p n is the number of pole pairs of the motor; T e is the electromagnetic torque; P e is the mechanical power output by the motor; T L is the flywheel load torque; J is the moment of inertia of the motor rotor and flywheel system.

[0022] Optionally, the objective function used in the model predictive control is:

[0023]

[0024] Where F is the objective function, representing the overall optimization goal; T is the predicted time range; ω t is the weight factor used to adjust the relative importance of frequency deviation; Δf is the frequency deviation; r t is the weight factor, which is used to adjust the smoothness of the flywheel output power; p t is the output power of the flywheel at time t.

[0025] Optionally, the physical constraints include: energy constraints and flywheel speed constraints;

[0026] The energy constraint is:

[0027]

[0028]

[0029] In the formula, E charge is the charging energy of the flywheel energy storage system during a frequency modulation period, E discharge is the discharge energy of the flywheel energy storage system during a frequency modulation period; are the maximum energy that the flywheel energy storage system can absorb and emit respectively; J f is the sum of the rotational inertia of the flywheel and the permanent magnet synchronous motor; Ω max ,Ω min are the maximum and minimum mechanical angular velocities of the flywheel energy storage system respectively; Ω is the current mechanical angular velocity of the flywheel;

[0030] The flywheel speed constraint is:

[0031]

[0032] Where Ω′ is the mechanical angular velocity of the flywheel after primary frequency modulation, and ΔE is the energy actually emitted or absorbed by the flywheel energy storage system.

[0033] Optionally, determining an adaptive control coefficient based on the frequency deviation and a rate of change of the frequency deviation includes:

[0034] The adaptive control coefficient is determined according to the following formula:

[0035]

[0036] Where A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation, K 1 is the first proportionality coefficient, K 2 is the second proportionality coefficient.

[0037] Optionally, determining the first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation includes:

[0038] The first active reference signal is determined according to the following formula:

[0039]

[0040] Among them, P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation.

[0041] Optionally, calculating the second active reference signal according to the current flywheel charge state includes:

[0042] The second active reference signal is calculated according to the following formula:

[0043]

[0044] Among them, P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, SOC is the current flywheel charge state, SOC max is the maximum state of charge of the flywheel, SOC min is the minimum charge state of the flywheel, K p is the proportionality coefficient, K i is the integral coefficient, ω is the electrical angular velocity of the permanent magnet synchronous motor, ω max is the maximum electrical angular velocity of the permanent magnet synchronous motor, ω min is the minimum electrical angular velocity of the permanent magnet synchronous motor.

[0045] In order to achieve the above object, according to another aspect of the present invention, a primary frequency modulation control device based on a flywheel energy storage system is provided, the device is applied to the flywheel energy storage system, and the device comprises:

[0046] A frequency deviation acquisition unit, used for acquiring a frequency deviation of a power system;

[0047] a first active reference signal determining unit, configured to determine an adaptive control coefficient based on the frequency deviation and a rate of change of the frequency deviation if the frequency deviation is greater than or equal to a frequency deviation threshold, and further determine a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation;

[0048] A primary frequency modulation control unit is used to perform primary frequency modulation control on the power system based on the first active power reference signal.

[0049] Optionally, the primary frequency modulation control device based on the flywheel energy storage system further includes:

[0050] The self-recovery control unit is used to calculate a second active reference signal according to the current flywheel charge state if the frequency deviation is less than the frequency deviation threshold, and then perform self-recovery control on its own flywheel charge state according to the second active reference signal.

[0051] Optionally, the primary frequency regulation control unit is specifically used to perform primary frequency regulation control on the power system based on the first active reference signal and applying model predictive control.

[0052] In order to achieve the above-mentioned purpose, according to another aspect of the present invention, a computer device is also provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the primary frequency regulation control method based on the flywheel energy storage system are implemented.

[0053] In order to achieve the above-mentioned purpose, according to another aspect of the present invention, a computer-readable storage medium is further provided, on which a computer program / instruction is stored, and when the computer program / instruction is executed by a processor, the steps of the primary frequency regulation control method based on the flywheel energy storage system are implemented.

[0054] In order to achieve the above object, according to another aspect of the present invention, a computer program product is further provided, including a computer program / instruction, which, when executed by a processor, implements the steps of the primary frequency regulation control method based on a flywheel energy storage system.

[0055] The beneficial effects of the present invention are:

[0056] In the present invention, when the frequency deviation of the power system is greater than or equal to the frequency deviation threshold, the flywheel energy storage system determines an adaptive control coefficient based on the frequency deviation and the rate of change of the frequency deviation, and then determines a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation, and then performs a frequency modulation control on the power system based on the first active reference signal, thereby achieving the beneficial effect of improving the stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0058] Figure 1 is a flow chart of a primary frequency modulation control method based on a flywheel energy storage system according to an embodiment of the present invention;

[0059] Figure 2 is a flow chart of the model predictive control of an embodiment of the present invention;

[0060] Figure 3 It is a flow chart of a frequency modulation method of a flywheel energy storage adaptive model predictive control strategy according to an embodiment of the present invention;

[0061] Figure 4 This is a primary frequency modulation structure diagram of a flywheel energy storage system according to an embodiment of the present invention;

[0062] Figure 5 is a frequency curve of the frequency modulation measure applied in the embodiment of the present invention;

[0063] Figure 6 is a frequency and phase angle curve output by a phase-locked loop according to an embodiment of the present invention;

[0064] Figure 7 is the SOC curve of the flywheel energy storage system according to an embodiment of the present invention;

[0065] Figure 8 is a given charging absorption power command Pref curve of the flywheel energy storage system according to an embodiment of the present invention;

[0066] Fig. 9 It is a structural block diagram of a primary frequency modulation control device based on a flywheel energy storage system according to an embodiment of the present invention;

[0067] Fig.10 It is a schematic diagram of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0068] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0069] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0070] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0071] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0072] In order to solve the problems of large volatility, low stability and insufficient frequency regulation capability of traditional synchronous generators in the new power system, the present invention provides a primary frequency regulation control strategy based on a flywheel energy storage system. The flywheel energy storage system includes: a permanent magnet synchronous motor, an inverter, a flywheel, a gearbox, a system frequency monitoring unit and a frequency regulation control unit. The flywheel is coaxially connected to the rotor side of the permanent magnet synchronous motor through a speed regulator to store rotor kinetic energy; the speed ratio of the gearbox is set to provide greater kinetic energy for the flywheel; the stator side of the permanent magnet synchronous motor is connected to the power grid through an inverter, and the absorption and release of active power are achieved by controlling the trigger signal of the inverter; the system frequency monitoring unit monitors the system frequency in real time through a phase-locked loop, and transmits the frequency signal to the frequency regulation control unit; the frequency regulation control unit calculates the inverter trigger signal according to the system frequency and the current operating state of the permanent magnet synchronous motor, and realizes parameter-adaptive primary frequency regulation control.

[0073] It should be noted that the primary frequency modulation control method based on the flywheel energy storage system in the following embodiments of the present invention is applied to the flywheel energy storage system, and specifically to the frequency modulation control unit in the flywheel energy storage system.

[0074] Figure 1 is a flow chart of a primary frequency modulation control method based on a flywheel energy storage system according to an embodiment of the present invention. Figure 1 As shown, in one embodiment of the present invention, the primary frequency regulation control method based on the flywheel energy storage system of the present invention includes steps S101 to S103.

[0075] Step S101, obtaining the frequency deviation of the power system.

[0076] In one embodiment of the present invention, this step can specifically monitor the frequency deviation Δf of the power system in real time through a phase-locked loop through a system frequency monitoring unit in the flywheel energy storage system. The present invention monitors the three-phase voltage of the bus and converts it to a two-phase synchronous coordinate system, obtains phase information through a phase detector of a phase-locked loop, and processes and adjusts the phase information through a loop filter and a voltage-controlled oscillator to achieve tracking and locking of the power system frequency f.

[0077] The specific scheme of the system frequency monitoring unit to monitor the frequency deviation Δf of the power system in real time through a phase-locked loop is as follows:

[0078] The sampling frequency of the phase-locked loop is f s , assuming the current grid frequency is f grid , then the actual grid operation angle θ within the N sampling times of the phase-locked loop is N for:

[0079] θ N =N×f grid ×360° / f s (1)

[0080] The angle tracked by the phase-locked loop in N sampling times is composed of two parts: one part is accumulated at a fixed step size (Δθ = 360° / N) in each sampling period, and the other part is the angle error Δθ output by the phase-locked loop PI regulator in each sampling period. i The accumulation of:

[0081]

[0082] In formula (2), N is the number of sampling times, Δθ i is the accumulated angle error of the PI regulator, θ 0 is the initial angle, is the phase-locked loop tracking angle.

[0083] Furthermore, after the phase-locked loop is stable, the phase-locked loop tracking angle is equal to the angle of the power grid, that is, By simplifying formula (1) and formula (2), we can get:

[0084]

[0085] The grid frequency can be obtained from formula (3), and then the frequency deviation Δf = f grid -f N , f N is the rated frequency, f N =50Hz.

[0086] Step S102, if the frequency deviation is greater than or equal to the frequency deviation threshold, determining an adaptive control coefficient based on the frequency deviation and the rate of change of the frequency deviation, and then determining a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation.

[0087] Step S103: performing a frequency modulation control on the power system based on the first active power reference signal.

[0088] like Figure 3 As shown, after obtaining the frequency deviation Δf, the present invention determines |Δf|≥f 0 Is it established? 0 is the frequency deviation threshold. If it does not hold, the system frequency is considered stable, and the frequency modulation control unit performs self-recovery control on the flywheel state of charge (SOC) of the flywheel energy storage system.

[0089] If |Δf|≥f 0 Established, that is, when the frequency deviation exceeds the frequency regulation dead zone, a primary frequency regulation is required. Primary frequency regulation refers to the participation of the flywheel energy storage system in the power system, and by adjusting its own power output, it realizes the control and stabilization of the grid frequency. In the primary frequency regulation, the present invention adopts different control coefficients according to different frequency regulation requirements. Specifically, the present invention determines an adaptive control coefficient based on the frequency deviation and the rate of change of the frequency deviation, and the adaptive control coefficient is used to represent different frequency regulation requirements, and then determines a first active reference signal based on the adaptive control coefficient and the rate of change of the frequency deviation, and finally the frequency regulation control unit performs a primary frequency modulation control based on the first active reference signal.

[0090] In the present invention, when performing a frequency modulation, the frequency modulation control unit specifically controls the converter according to the first active reference signal, and the converter adjusts the operating state of the permanent magnet synchronous motor, thereby controlling the flywheel energy storage system to output or absorb active power to achieve the frequency modulation target.

[0091] like Figure 3 As shown, in one embodiment of the present invention, if |Δf|≥f 0 If it is established, a frequency modulation is performed, and different control coefficients are used according to different frequency modulation requirements. In the frequency deterioration stage, that is, When the frequency is restored to the rated value quickly, a large control coefficient is used; in the frequency recovery stage, that is, When , a small control coefficient is used to avoid overshoot and frequency fluctuation. At this time, the reference active signal of the flywheel energy storage system (ie, the first active reference signal) is shown in formula (4).

[0092]

[0093] In formula (4), P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation.

[0094] Furthermore, the adaptive control coefficient A is determined by equation (5).

[0095]

[0096] In formula (5), A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation, K 1 is the first proportionality coefficient, K 2 is the second proportionality coefficient.

[0097] In one embodiment of the present invention, the primary frequency modulation control method based on the flywheel energy storage system of the present invention further includes:

[0098] If the frequency deviation is less than the frequency deviation threshold, a second active reference signal is calculated according to the current flywheel charge state, and then self-recovery control is performed on its own flywheel charge state according to the second active reference signal.

[0099] The frequency control unit is the executor of the flywheel state of charge (SOC) self-recovery control. It ref , generate specific control signals and adjust the working state of the converter. The converter adjusts the power flow according to the output signal of the frequency modulation control unit, so that the SOC of the flywheel system gradually returns to the target range.

[0100] In the present invention, if |Δf|≥f 0 If it is not established, the system frequency is considered stable, and the flywheel state of charge (SOC) self-recovery control is performed. At this time, the flywheel speed is controlled to run stably within the set operating range. When the SOC is lower than the set value, the SOC <SOC min When SOC is higher than the set value, SOC>SOC max When SOC is between the maximum and minimum set values, the active power reference value of the flywheel energy storage system remains unchanged.

[0101] In one embodiment of the present invention, the above step of calculating the second active reference signal according to the current flywheel charge state specifically includes:

[0102] The second active reference signal is calculated according to the following formula:

[0103]

[0104] In formula (6) and formula (7), P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, SOC is the current flywheel charge state, SOC max is the maximum state of charge of the flywheel, SOC min is the minimum charge state of the flywheel, K p is the proportionality coefficient, K i is the integral coefficient, ω is the electrical angular velocity of the permanent magnet synchronous motor, ω max is the maximum electrical angular velocity of the permanent magnet synchronous motor, ω min is the minimum electrical angular velocity of the permanent magnet synchronous motor.

[0105] As can be seen from formula (6), the present invention calculates the active reference signal (second active reference signal) of the self-recovery control through PI (proportional-integral) control, thereby being able to respond quickly to frequency deviations, quickly adjust the power output of the flywheel energy storage system to restore the grid frequency, and also eliminate the steady-state error of the system to ensure that the frequency can be accurately restored to the set value. Calculating the active reference signal through PI control can not only quickly respond to frequency deviations and accurately restore frequency, but also has the advantages of simple algorithm, good robustness and easy implementation. It is a stable and efficient control method that is highly consistent with the self-recovery requirements of the flywheel energy storage system.

[0106] In one embodiment of the present invention, the performing of frequency modulation control on the power system based on the first active power reference signal in step S103 specifically includes:

[0107] Based on the first active reference signal and by applying model predictive control, a frequency modulation control is performed on the power system.

[0108] In one embodiment of the present invention, the process of performing a frequency control on a power system using model predictive control (MPC) based on a first active reference signal includes: first, combining the mathematical model and physical constraints of the flywheel energy storage system to construct an objective function and predict the future state of the system; then, by solving the objective function, an optimized power control instruction is generated; finally, the power control instruction is converted into a control signal of the converter, the charge and discharge power of the flywheel is adjusted, the frequency deviation is quickly compensated, and the dynamic recovery and stabilization of the grid frequency are achieved.

[0109] In one embodiment of the present invention, a flywheel energy storage system applies model predictive control (MPC) in primary frequency modulation, and the change in the speed of the permanent magnet synchronous motor in the flywheel energy storage system is used to characterize the charging and discharging process of the energy storage system. Therefore, the present invention can use the mathematical model of the permanent magnet synchronous motor as the mathematical model of the model predictive control. The mathematical model of the flywheel energy storage system used in the model predictive control is specifically:

[0110] dψ d / dt=(R s i d -ω e ψ q ) / L s

[0111] dψ q / dt=(R s i q +ω e ω d ) / L s

[0112] dω e / dt=(Te-T L ) / J

[0113]

[0114] In formula (8), the subscripts d and q are the components of the two-phase rotating coordinate system in the d and q directions; ψ is the stator flux of the motor; R s is the stator winding resistance of the motor; ω e is the angular velocity of the motor rotor; i is the current of the motor; L s is the synchronous inductance; p n is the number of pole pairs of the motor; t e is the electromagnetic torque; P e is the mechanical power output by the motor; T L is the flywheel load torque; J is the moment of inertia of the motor rotor and flywheel system.

[0115] like Figure 2 As shown, in one embodiment of the present invention, the above steps are based on the first active reference signal and apply model predictive control to perform a frequency control on the power system, specifically including steps S201 to S203.

[0116] Step S201: taking the first active reference signal as the optimization target of the model predictive control.

[0117] In the power system, the first active reference signal reflects the current frequency deviation and frequency regulation demand of the system. In the model predictive control (MPC), this signal is used as the optimization target to predict the future response behavior of the flywheel energy storage system, aiming to minimize the frequency deviation by adjusting the flywheel output power, thereby providing target guidance for subsequent optimization calculations.

[0118] Step S202, obtaining the optimal power control instruction by solving the objective function to minimize the optimization target while satisfying the physical constraints of the flywheel energy storage system.

[0119] In one embodiment of the present invention, based on the mathematical model of the flywheel energy storage system, the present invention constructs an objective function with frequency deviation and flywheel power smoothness as the target, and considers physical constraints such as flywheel energy and speed. Within each prediction time range, the MPC solver minimizes the objective function through an optimization algorithm to obtain the optimal power command that meets the system constraints, ensuring that the flywheel can effectively participate in primary frequency control.

[0120] Step S203: convert the power control instruction into a control signal of the converter, and then control the converter based on the control signal.

[0121] In one embodiment of the present invention, the present invention generates PWM signals for controlling the converter by calculating the required current and voltage signals according to the power control instructions obtained by the solution. These PWM signals drive the converter to adjust the charge and discharge power of the flywheel energy storage system so that the actual power output is consistent with the optimization instructions, thereby achieving accurate regulation and stable recovery of the power system frequency.

[0122] In one embodiment of the present invention, the present invention calculates the corresponding PWM duty cycle according to the power control instruction. This can be calculated through the voltage and power relationship of the inverter: through the power control instruction, the required current is inferred, and then the corresponding voltage is calculated. A triangular wave or a sawtooth wave is used as a reference signal, which is compared with the target voltage signal to generate a PWM signal. The generated PWM signal is applied to the control of the converter to drive the bridge arm of the inverter. In the actual control process, the system monitors the speed of the flywheel and the frequency of the power grid in real time, and feeds this information back to the control algorithm for necessary corrections. The control strategy of the flywheel energy storage system working in coordination with the thermal power unit can further enhance the frequency response capability of the system, avoid frequent output of the thermal power unit during primary frequency modulation, reduce the regulation requirements of the thermal power unit when responding to frequency changes, and at the same time maximize the use of the flywheel energy storage frequency modulation capacity and ensure the operation safety during the flywheel energy storage frequency modulation.

[0123] In one embodiment of the present invention, the objective function used in the model predictive control is:

[0124]

[0125] In formula (9), F is the objective function, which represents the overall optimization goal; T is the predicted time range; ω t is the weight factor used to adjust the relative importance of frequency deviation; Δf is the frequency deviation; r t is the weight factor, which is used to adjust the smoothness of the flywheel output power; p t is the output power of the flywheel at time t.

[0126] In the model predictive control (MPC) of flywheel energy storage systems participating in primary frequency regulation, the design of the objective function is crucial. For the application of flywheel energy storage systems in primary frequency regulation, the objective function aims to minimize the frequency deviation of the power grid and smooth the flywheel output power.

[0127] In the present invention, when the model predictive control is used to perform primary frequency regulation control on the power system, the physical constraints of the flywheel energy storage system also need to be considered.

[0128] In one embodiment of the present invention, the physical constraints include: energy constraints and flywheel speed constraints;

[0129] The energy constraint is:

[0130]

[0131] In formula (10), E charge is the charging energy of the flywheel energy storage system during a frequency modulation period, E discharge is the discharge energy of the flywheel energy storage system during a frequency modulation period; are the maximum energy that the flywheel energy storage system can absorb and emit respectively; J f is the sum of the rotational inertia of the flywheel and the permanent magnet synchronous motor; Ω max ,Ω min are the maximum and minimum mechanical angular velocities of the flywheel energy storage system respectively; Ω is the current mechanical angular velocity of the flywheel;

[0132] The flywheel speed constraint is:

[0133]

[0134] In formula (11), Ω′ is the mechanical angular velocity of the flywheel after primary frequency modulation, and ΔE is the energy actually emitted or absorbed by the flywheel energy storage system.

[0135] Specific application examples of the present invention will be introduced below.

[0136] In this application example, Figure 4In the power system shown in the figure, the left side of the system is a traditional synchronous generator, which is connected to the flywheel energy storage system and the power system load through the power line. The system is initially in a stable operating state. When t=50s, the load suddenly decreases, causing the system frequency to fluctuate. The flywheel energy storage adaptive coordinated control strategy frequency modulation method described in the present invention is used for frequency modulation. The system parameters are shown in Table 1.

[0137] Table 1 Main electrical parameters of power system

[0138]

[0139] Figure 5 The system frequency fluctuations under two conditions when the system suddenly reduces load, relying only on the synchronous generator for primary frequency regulation (Scheme 1) and using the flywheel energy storage adaptive model predictive control strategy frequency regulation method of the present invention (Scheme 2) are compared. Figure 5 It can be seen that when using scheme 1, the maximum frequency is 1.035pu (51.75Hz), and when using scheme 2, the maximum frequency is 1.016pu (50.8Hz), and the maximum frequency drops by 0.95Hz. At the same time, the flywheel energy storage system absorbs energy from the power grid and increases the speed of the flywheel to achieve the purpose of energy storage. On this basis, since the flywheel energy storage system uses a permanent magnet synchronous motor, the system frequency and voltage stability are effectively improved.

[0140] Depend on Figure 6 It can be seen that when the load is cut off at 50s, the system frequency rises, and the phase-locked loop can accurately track the frequency and phase angle of the power grid. Figure 7 It can be seen that when the flywheel energy storage adaptive model predictive control strategy frequency modulation method (Scheme 2) of the present invention is adopted, the SOC change curve of the flywheel energy storage system. SOC is usually a number less than 1, indicating the energy storage status of the current energy storage system, ranging from 0 to 1. SOC = 1 means that the flywheel energy storage system is in a fully charged state and stores the maximum energy; SOC = 0 means that the energy is completely exhausted. In the daily operation of the flywheel energy storage system, the SOC will not always remain at the extremes of 0 or 1, but will fluctuate within a certain range. Generally speaking, the flywheel energy storage system will maintain an SOC range of 0.5 to 0.8 during daily operation. In this application example, the SOC runs at 0.55. From Figure 7 It can be seen that when the grid frequency increases, the flywheel energy storage system can absorb power, the speed increases, and the SOC increases until the frequency stabilizes again. The flywheel energy storage system reaches stability again, and the SOC is 0.82 at this time.

[0141] P ref is the excess power command absorbed by the flywheel energy storage system. When the system is running stably, the power is balanced, P refis 0; when the load is cut and the frequency rises, there is a power surplus and the flywheel energy storage system needs to absorb the excess power, P ref Started to increase by Figure 8 Can be added, the maximum increase is 0.7, as the frequency recovers, P ref Approaching 0 again.

[0142] It can be seen that in order to solve the problems of large volatility, low stability and insufficient frequency regulation capability of traditional synchronous generators in the new power system, the present invention proposes a primary frequency regulation control strategy based on a flywheel energy storage system. The present invention takes into account the grid architecture of the new power system including traditional generators, flywheel energy storage systems, loads and other electrical equipment, and proposes a frequency regulation method suitable for flywheel energy storage adaptive model predictive control strategy. After measuring the frequency of the power system through a phase-locked loop, the present invention determines whether to enter SOC self-recovery control according to the frequency difference. Secondly, if the system frequency is high, the flywheel energy storage system works in charging mode, controls the speed of the permanent magnet synchronous motor to increase, and the rotor kinetic energy increases; if the system frequency is low, the flywheel energy storage system works in discharge mode, controls the speed of the permanent magnet synchronous motor to decrease, and the rotor kinetic energy decreases. The adaptive inertia coefficient is jointly determined by the system frequency deviation and the SOC of the flywheel energy storage system; the larger the absolute value of the system frequency deviation, the larger the inertia coefficient, and the stronger the anti-load disturbance capability of the flywheel energy storage system; when the system frequency deviation is negative, the flywheel energy storage system is in discharge mode, and transmits electric energy to the power grid through the control of the converter, while the flywheel speed decreases and the system frequency increases. When the system frequency deviation is positive, the flywheel energy storage system is in charging mode, and the electric energy drives the motor to rotate after the inverter frequency modulation, the flywheel speed increases, the rotor kinetic energy is stored, and the system frequency decreases. The flywheel energy storage adaptive model predictive control strategy frequency modulation method proposed in the present invention is suitable for new power systems and can effectively improve the stability of the power system.

[0143] The primary frequency modulation control method based on the flywheel energy storage system of the present invention achieves at least the following beneficial effects:

[0144] The present invention proposes a flywheel energy storage adaptive model predictive control strategy frequency regulation method based on flywheel energy storage to assist thermal power units. The present invention can compensate for system unbalanced power, enhance frequency stability, and reduce equipment failures caused by frequency fluctuations in new power systems, and has significant economic benefits; it can better reduce the frequency regulation pressure of coal-fired units and increase the inertia of the system.

[0145] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0146] Based on the same inventive concept, an embodiment of the present invention also provides a primary frequency regulation control device based on a flywheel energy storage system, which can be used to implement the primary frequency regulation control method based on a flywheel energy storage system described in the above embodiment, as described in the following embodiment. Since the principle of solving the problem by the primary frequency regulation control device based on a flywheel energy storage system is similar to that of the primary frequency regulation control method based on a flywheel energy storage system, the embodiment of the primary frequency regulation control device based on a flywheel energy storage system can refer to the embodiment of the primary frequency regulation control method based on a flywheel energy storage system, and the repeated parts will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0147] Fig. 9 This is a structural block diagram of a primary frequency modulation control device based on a flywheel energy storage system according to an embodiment of the present invention. It should be noted that the primary frequency modulation control device based on a flywheel energy storage system according to the present invention is applied to a flywheel energy storage system, specifically, to a frequency modulation control unit in a flywheel energy storage system. Fig. 9 As shown, in one embodiment of the present invention, the primary frequency regulation control device based on the flywheel energy storage system of the present invention includes:

[0148] A frequency deviation acquisition unit 1, used to acquire a frequency deviation of a power system;

[0149] A first active reference signal determination unit 2, configured to determine an adaptive control coefficient based on the frequency deviation and the rate of change of the frequency deviation if the frequency deviation is greater than or equal to a frequency deviation threshold, and further determine a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation;

[0150] The primary frequency modulation control unit 3 is used to perform primary frequency modulation control on the power system based on the first active power reference signal.

[0151] In one embodiment of the present invention, the primary frequency modulation control device based on the flywheel energy storage system of the present invention further includes:

[0152] The self-recovery control unit is used to calculate a second active reference signal according to the current flywheel charge state if the frequency deviation is less than the frequency deviation threshold, and then perform self-recovery control on its own flywheel charge state according to the second active reference signal.

[0153] In one embodiment of the present invention, the primary frequency regulation control unit is specifically configured to perform primary frequency regulation control on the power system based on the first active reference signal and by applying model predictive control.

[0154] In one embodiment of the present invention, the primary frequency modulation control unit includes:

[0155] An optimization target determination module, configured to use the first active reference signal as an optimization target for the model predictive control;

[0156] An optimal power control instruction determination module is used to obtain the optimal power control instruction by solving the objective function to minimize the optimization target while satisfying the physical constraints of the flywheel energy storage system;

[0157] The converter control module is used to convert the power control instruction into a control signal of the converter, and then control the converter based on the control signal.

[0158] In one embodiment of the present invention, the first active reference signal determining unit 2 includes:

[0159] The adaptive control coefficient determination module is used to determine the adaptive control coefficient according to the following formula:

[0160]

[0161] Where A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation, K 1 is the first proportionality coefficient, K 2 is the second proportionality coefficient.

[0162] In one embodiment of the present invention, the first active reference signal determining unit 2 includes:

[0163] The first active reference signal determination module is used to determine the first active reference signal according to the following formula:

[0164]

[0165] Among them, P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation.

[0166] In one embodiment of the present invention, the self-recovery control unit includes:

[0167] The second active reference signal determination module is used to calculate the second active reference signal according to the following formula:

[0168]

[0169] Among them, P ref is the active reference signal, P ref0is the active reference signal of the previous moment, SOC is the current flywheel charge state, SOC max is the maximum state of charge of the flywheel, SOC min is the minimum charge state of the flywheel, K p is the proportionality coefficient, K i is the integral coefficient, ω is the electrical angular velocity of the permanent magnet synchronous motor, ω max is the maximum electrical angular velocity of the permanent magnet synchronous motor, ω min is the minimum electrical angular velocity of the permanent magnet synchronous motor.

[0170] In order to achieve the above object, according to another aspect of the present application, a computer device is also provided. Fig.10 As shown, the computer device includes a memory, a processor, a communication interface and a communication bus. A computer program that can be executed on the processor is stored in the memory. When the processor executes the computer program, the steps in the above-mentioned embodiment method are implemented.

[0171] The processor may be a central processing unit (CPU). The processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination of the above chips.

[0172] The memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer executable programs and units, such as the corresponding program units in the above method embodiments of the present invention. The processor executes various functional applications of the processor and works data processing by running the non-transitory software programs, instructions and modules stored in the memory, that is, implementing the method in the above method embodiments.

[0173] The memory may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created by the processor, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0174] The one or more units are stored in the memory, and when executed by the processor, the method in the above embodiment is performed.

[0175] The specific details of the above-mentioned computer device can be understood by referring to the corresponding related descriptions and effects in the above-mentioned embodiments, and will not be repeated here.

[0176] In order to achieve the above purpose, according to another aspect of the present application, a computer-readable storage medium is also provided, wherein the computer-readable storage medium stores a computer program, and the computer program implements the steps in the primary frequency modulation control method based on the flywheel energy storage system when executed in a computer processor. Those skilled in the art can understand that the implementation of all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and the program can include the processes of the embodiments of the above-mentioned methods when executed. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory (Flash Memory), a hard disk (Hard Disk Drive, abbreviated as: HDD) or a solid-state drive (SSD), etc.; the storage medium can also include a combination of the above-mentioned types of memory.

[0177] In order to achieve the above-mentioned purpose, according to another aspect of the present application, a computer program product is further provided, including a computer program / instruction, which, when executed by a processor, implements the steps of the above-mentioned primary frequency regulation control method based on a flywheel energy storage system.

[0178] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0179] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A primary frequency modulation control method based on a flywheel energy storage system, characterized in that: Applied to a flywheel energy storage system, the method comprises: Obtain frequency deviation of power system; If the frequency deviation is greater than or equal to a frequency deviation threshold, determining an adaptive control coefficient based on the frequency deviation and a rate of change of the frequency deviation, and further determining a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation; A frequency modulation control is performed on the power system based on the first active power reference signal.

2. The primary frequency modulation control method based on the flywheel energy storage system according to claim 1 is characterized in that: Also includes: If the frequency deviation is less than the frequency deviation threshold, a second active reference signal is calculated according to the current flywheel charge state, and then self-recovery control is performed on its own flywheel charge state according to the second active reference signal.

3. The primary frequency modulation control method based on the flywheel energy storage system according to claim 1 is characterized in that: The performing a frequency modulation control on the power system based on the first active reference signal includes: Based on the first active reference signal and by applying model predictive control, a frequency modulation control is performed on the power system.

4. The primary frequency modulation control method based on the flywheel energy storage system according to claim 3 is characterized in that: The performing a frequency modulation control on the power system based on the first active reference signal and applying model predictive control includes: Using the first active reference signal as an optimization target of the model predictive control; The optimal power control command is obtained by solving the objective function to minimize the optimization target while satisfying the physical constraints of the flywheel energy storage system; The power control instruction is converted into a control signal of the converter, and the converter is then controlled based on the control signal.

5. The primary frequency modulation control method based on the flywheel energy storage system according to claim 3 is characterized in that: The mathematical model of the flywheel energy storage system used in the model predictive control is: dψ d / dt=(R s I d -oh e ψ q ) / L s dψ q / dt=(R s I q +oh e ψ d ) / L s dω e / dt=(Te-T L ) / J Where, the subscripts d and q are the components of the two-phase rotating coordinate system in the d and q directions; ψ is the stator flux of the motor; R s is the stator winding resistance of the motor; ω e is the angular velocity of the motor rotor; i is the current of the motor; L s is the synchronous inductance; p n is the number of pole pairs of the motor; T e is the electromagnetic torque; P e is the mechanical power output by the motor; T L is the flywheel load torque; J is the moment of inertia of the motor rotor and flywheel system.

6. The primary frequency modulation control method based on the flywheel energy storage system according to claim 4 is characterized in that: The objective function used in the model predictive control is: In the formula, F is the objective function, which represents the overall optimization goal; T is the time horizon of the forecast; ω t is the weight factor used to adjust the relative importance of frequency deviation; Δf is the frequency deviation; r t is the weight factor, which is used to adjust the smoothness of the flywheel output power; p t is the output power of the flywheel at time t.

7. The primary frequency modulation control method based on the flywheel energy storage system according to claim 4 is characterized in that: The physical constraints include: energy constraints and flywheel speed constraints; The energy constraint is: In the formula, E charge is the charging energy of the flywheel energy storage system during a frequency modulation period, E discharge is the discharge energy of the flywheel energy storage system during a frequency modulation period; are the maximum energy that the flywheel energy storage system can absorb and emit respectively; J f is the sum of the rotational inertia of the flywheel and the permanent magnet synchronous motor; Ω max ,Ω min are the maximum and minimum mechanical angular velocities of the flywheel energy storage system respectively; Ω is the current mechanical angular velocity of the flywheel; The flywheel speed constraint is: Where Ω′ is the mechanical angular velocity of the flywheel after primary frequency modulation, and ΔE is the energy actually emitted or absorbed by the flywheel energy storage system.

8. The primary frequency modulation control method based on the flywheel energy storage system according to claim 1, characterized in that: The step of determining an adaptive control coefficient based on the frequency deviation and the rate of change of the frequency deviation includes: The adaptive control coefficient is determined according to the following formula: Where A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation, K1 is the first proportional coefficient, and K2 is the second proportional coefficient.

9. The primary frequency modulation control method based on the flywheel energy storage system according to claim 1, characterized in that: The determining the first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation includes: The first active reference signal is determined according to the following formula: Among them, P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, A is the adaptive control coefficient, Δf is the frequency deviation, is the rate of change of frequency deviation.

10. The primary frequency modulation control method based on the flywheel energy storage system according to claim 2, characterized in that: The step of calculating the second active reference signal according to the current flywheel charge state includes: The second active reference signal is calculated according to the following formula: Among them, P ref is the active reference signal, P ref0 is the active reference signal of the previous moment, SOC is the current flywheel charge state, SOC max is the maximum state of charge of the flywheel, SOC min is the minimum charge state of the flywheel, K p is the proportionality coefficient, K i is the integral coefficient, ω is the electrical angular velocity of the permanent magnet synchronous motor, ω max is the maximum electrical angular velocity of the permanent magnet synchronous motor, ω min is the minimum electrical angular velocity of the permanent magnet synchronous motor.

11. A primary frequency modulation control device based on a flywheel energy storage system, characterized in that: Applied to a flywheel energy storage system, the device comprises: A frequency deviation acquisition unit, used for acquiring a frequency deviation of a power system; a first active reference signal determining unit, configured to determine an adaptive control coefficient based on the frequency deviation and a rate of change of the frequency deviation if the frequency deviation is greater than or equal to a frequency deviation threshold, and further determine a first active reference signal according to the adaptive control coefficient and the rate of change of the frequency deviation; A primary frequency modulation control unit is used to perform primary frequency modulation control on the power system based on the first active power reference signal.

12. The primary frequency modulation control device based on the flywheel energy storage system according to claim 11, characterized in that: Also includes: The self-recovery control unit is used to calculate a second active reference signal according to the current flywheel charge state if the frequency deviation is less than the frequency deviation threshold, and then perform self-recovery control on its own flywheel charge state according to the second active reference signal.

13. The primary frequency modulation control device based on the flywheel energy storage system according to claim 11, characterized in that: The primary frequency regulation control unit is specifically used to perform primary frequency regulation control on the power system based on the first active reference signal and by applying model predictive control.

14. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 10 are implemented.

15. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 10 are implemented.

16. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 10 are implemented.

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