Power grid operation frequency control method, device, equipment and medium

Abstract

The invention relates to a power grid operation frequency control method and device, equipment and a medium, and the method comprises the steps: determining a frequency feed-forward item of each network-building type inverter according to a difference value between the center frequency of a network-building type inverter group and the rated angular frequency of a power system; calculating a phase angle and a virtual internal electromotive force amplitude of each grid-forming inverter according to the operation parameters and the frequency feed-forward item of the grid-forming inverter and the control equation of the grid-forming inverter for each grid-forming inverter; according to the phase angle and the virtual internal electromotive force amplitude, determining a three-phase modulation wave of the grid-forming inverter; controlling the operation state of the network-forming inverter based on the three-phase modulation wave; the operation state of the grid-forming inverter is related to the operation frequency of the power system. According to the method, the frequency deviation can be compensated in advance by introducing the frequency feed-forward item, so that the grid-forming inverter can respond to the change of the frequency of the power system more quickly, and the stability of the operation frequency of the power grid can be effectively controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy power generation, in particular to a power grid operating frequency control method, device, equipment and medium. BACKGROUND

[0002] With the large access of new energy power generation, the power system presents the characteristics of low inertia and weak damping, which leads to the fluctuation of the power grid operating frequency. The fluctuation of the power grid operating frequency may cause damage to power equipment, decrease power supply quality, and even cause system collapse. Therefore, the stability of the power grid operating frequency is crucial to the safe operation of the power system.

[0003] In the related art, the stability of the power grid operating frequency is controlled by a grid-forming inverter. However, under the condition of a weak power grid, the grid-forming inverter cannot effectively control the stability of the power grid operating frequency. SUMMARY

[0004] Therefore, it is necessary to provide a power grid operating frequency control method, device, computer equipment, computer readable storage medium and computer program product in view of the above technical problems.

[0005] In a first aspect, the present application provides a power grid operating frequency control method, which is applied to a power system including a grid-forming inverter group, the grid-forming inverter group including a plurality of grid-forming inverters connected in parallel with each other, and the method further includes:

[0006] determining a frequency feedforward term of each grid-forming inverter according to a difference between a center frequency of the grid-forming inverter group and a rated angular frequency of the power system;

[0007] for each grid-forming inverter, calculating a phase angle and a virtual internal electromotive force amplitude of the grid-forming inverter according to an operating parameter of the grid-forming inverter, the frequency feedforward term and a control equation of the grid-forming inverter;

[0008] determining a three-phase modulation wave of the grid-forming inverter according to the phase angle and the virtual internal electromotive force amplitude;

[0009] controlling an operating state of the grid-forming inverter based on the three-phase modulation wave; the operating state of the grid-forming inverter is related to an operating frequency of the power system.

[0010] In one embodiment, the operating parameter includes a first operating parameter and a second operating parameter, and the control equation includes an active loop control equation and a reactive control equation; calculating the phase angle and the virtual internal electromotive force amplitude of the grid-forming inverter according to the operating parameter of the grid-forming inverter, the frequency feedforward term and the control equation of the grid-forming inverter includes:

[0011] According to the first operating parameter, the frequency feedforward term and the active loop control equation, the phase angle is calculated; the first operating parameter comprises an active reference value, an active measured value and a virtual inertia of the grid-forming inverter;

[0012] According to the second operating parameter, the frequency feedforward term and the reactive control equation, the virtual internal electromotive force amplitude is calculated; the second operating parameter comprises a reactive inertia coefficient, a change rate of the virtual internal electromotive force amplitude, a reactive-voltage droop coefficient, a rated output voltage, a reactive reference value and a reactive measured value of the grid-forming inverter.

[0013] In one of the embodiments, according to the first operating parameter, the frequency feedforward term and the active loop control equation, the phase angle is calculated, comprising:

[0014] According to the first operating parameter and the active loop control equation, the output angular frequency of the grid-forming inverter is calculated;

[0015] According to the integral value of the output angular frequency and the sum of the frequency feedforward terms, the phase angle is obtained.

[0016] In one of the embodiments, the active loop control equation is: , wherein, is a virtual inertia of the i-th grid-forming inverter; is a rated angular frequency of the grid-forming inverter group; is a change rate of the angular frequency of the power system; is a damping coefficient of the i-th grid-forming inverter; is an output angular frequency of the i-th grid-forming inverter; is an active reference value of the i-th grid-forming inverter; is an active measured value of the i-th grid-forming inverter. In one of the embodiments, is determined according to a product value of a matching coefficient of the grid-forming inverter and an adaptive virtual inertia of the grid-forming inverter. In one of the embodiments, the reactive control equation of the grid-forming inverter is: , wherein,

[0017] is a reactive inertia coefficient of the i-th grid-forming inverter; is a change rate of the virtual internal electromotive force amplitude of the i-th grid-forming inverter;

[0018] In one of the embodiments, the reactive control equation of the grid-forming inverter is: , wherein, is a reactive-voltage droop coefficient of the i-th grid-forming inverter; is a reactive inertia coefficient of the i-th grid-forming inverter; is a change rate of the virtual internal electromotive force amplitude of the i-th grid-forming inverter; is a reactive-voltage droop coefficient of the i-th grid-forming inverter; is a reactive-voltage droop coefficient of the i-th grid-forming inverter; ​​a rated output voltage of the grid-forming inverter; a reactive reference value of the first grid-forming inverter; a reactive reference value of the first grid-forming inverter.

[0019] In one of the embodiments, the method further comprises:

[0020] determining a center frequency of the group of grid-forming inverters according to the virtual inertia coefficient of each grid-forming inverter, the initial output angular frequency of each grid-forming inverter, and a preset formula; wherein the preset formula is: , a center frequency of the group of grid-forming inverters; a virtual inertia coefficient of the first grid-forming inverter; an initial output angular frequency of the first grid-forming inverter.

[0021] In a second aspect, the present application further provides a power grid operating frequency control device, which comprises:

[0022] a frequency feedforward term determination module configured to determine a frequency feedforward term of each grid-forming inverter according to a difference between the center frequency of the group of grid-forming inverters and a rated angular frequency of the power system;

[0023] an internal control variable determination module configured to calculate, for each grid-forming inverter, a phase angle and a virtual internal electromotive force amplitude of the grid-forming inverter according to an operating parameter of the grid-forming inverter, the frequency feedforward term, and a control equation of the grid-forming inverter;

[0024] a three-phase modulation wave determination module configured to determine a three-phase modulation wave of the grid-forming inverter according to the phase angle and the virtual internal electromotive force amplitude;

[0025] a power grid operating frequency control module configured to control an operating state of the grid-forming inverter based on the three-phase modulation wave; the operating state of the grid-forming inverter is related to an operating frequency of the power system.

[0026] In a third aspect, the present application further provides a computer device, which comprises a memory and a processor; the memory stores a computer program; and the processor implements the following steps when executing the computer program:

[0027] determining a frequency feedforward term of each grid-forming inverter according to a difference between the center frequency of the group of grid-forming inverters and a rated angular frequency of the power system;

[0028] For each grid-type inverter, the phase angle and virtual internal electromotive force amplitude of the grid-type inverter are calculated based on the operating parameters, frequency feedforward term and control equation of the grid-type inverter.

[0029] The three-phase modulation wave of the grid-type inverter is determined based on the phase angle and the amplitude of the virtual internal electromotive force.

[0030] The operating state of the grid-type inverter is controlled by a three-phase modulated wave; the operating state of the grid-type inverter is related to the operating frequency of the power system.

[0031] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the following steps:

[0032] The frequency feedforward term of each grid-type inverter is determined based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system.

[0033] For each grid-type inverter, the phase angle and virtual internal electromotive force amplitude of the grid-type inverter are calculated based on the operating parameters, frequency feedforward term and control equation of the grid-type inverter.

[0034] The three-phase modulation wave of the grid-type inverter is determined based on the phase angle and the amplitude of the virtual internal electromotive force.

[0035] The operating state of the grid-type inverter is controlled by a three-phase modulated wave; the operating state of the grid-type inverter is related to the operating frequency of the power system.

[0036] Fifthly, this application also provides a computer program product comprising a computer program that, when executed by a processor, performs the following steps:

[0037] The frequency feedforward term of each grid-type inverter is determined based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system.

[0038] For each grid-type inverter, the phase angle and virtual internal electromotive force amplitude of the grid-type inverter are calculated based on the operating parameters, frequency feedforward term and control equation of the grid-type inverter.

[0039] The three-phase modulation wave of the grid-type inverter is determined based on the phase angle and the amplitude of the virtual internal electromotive force.

[0040] The operating state of the grid-type inverter is controlled by a three-phase modulated wave; the operating state of the grid-type inverter is related to the operating frequency of the power system.

[0041] The aforementioned power grid operating frequency control method, device, equipment, and medium first determine the frequency feedforward term for each grid-type inverter based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system. Then, for each grid-type inverter, the phase angle and virtual internal electromotive force amplitude are calculated based on the inverter's operating parameters, frequency feedforward term, and control equations. Next, the three-phase modulation wave of the grid-type inverter is determined based on the phase angle and virtual internal electromotive force amplitude. Finally, the operating state of the grid-type inverter is controlled based on the three-phase modulation wave. The operating state of the grid-type inverter is related to the operating frequency of the power system. This application employs the aforementioned method, which, by introducing a frequency feedforward term, can compensate for frequency deviations in advance, enabling the grid-type inverter to respond more quickly to changes in power system frequency and improving the system's dynamic response performance. Furthermore, by accurately calculating the phase angle and virtual internal electromotive force amplitude, and generating a three-phase modulation wave based on these parameters, precise control of the grid-type inverter output is achieved, thereby enhancing the stability of the power system and reducing the impact of frequency fluctuations on the power system. Attached Figure Description

[0042] Figure 1 Application environment diagrams for the power grid operating frequency control method provided in some embodiments of this application;

[0043] Figure 2 Flowcharts of power grid operating frequency control methods provided in some embodiments of this application;

[0044] Figure 3 A flowchart for calculating the virtual internal electromotive force amplitude provided for some embodiments of this application;

[0045] Figure 4 A flowchart for calculating phase angles is provided for some embodiments of this application;

[0046] Figure 5 This application provides control schematic diagrams for power grid operating frequency control methods in some embodiments.

[0047] Figure 6 This is a schematic diagram of the power response waveform of a grid-type inverter when using traditional control methods and having a small virtual inertia.

[0048] Figure 7 This is a schematic diagram of the power response waveform of a grid-type inverter when using traditional control methods and having a large virtual inertia.

[0049] Figure 8 This is a schematic diagram of the power response waveform of a grid-connected inverter when using the grid operation frequency control method provided in the embodiments of this application;

[0050] Figure 9Structural block diagram of a power grid operating frequency control device provided in some embodiments of this application;

[0051] Figure 10 This is an internal structural diagram of a computer device provided in some embodiments of this application. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0053] The power grid operating frequency control method provided in this application embodiment can be applied to, for example... Figure 1 The power system shown includes a grid-connected inverter group, a power grid, and a control system. The grid-connected inverter group consists of multiple grid-connected inverters connected in parallel. These inverters are connected in parallel to the same busbar via line impedance, and the busbar is connected to the power grid. Each grid-connected inverter adopts a two-level three-phase bridge circuit topology. It is the DC bus voltage. It is the filter inductor of the grid-connected inverter. It is the filter resistor of the grid-connected inverter; These are the filter capacitors for grid-connected inverters. It is the equivalent inductance of the power grid; It is the equivalent resistance of the power grid.

[0054] The control system includes a sampling and conditioning circuit, a grid-type inverter controller, and a drive protection circuit. The sampling and conditioning circuit controls the voltage of the filter capacitor on the AC side of the grid-type inverter. With inductor current Sampling is performed to obtain sampled data. The sampled data, after being converted by the AD sampling circuit in the sampling conditioning circuit, is sent to the grid-type inverter controller for processing. The grid-type inverter controller can execute the grid operating frequency control method provided in the embodiments of this application. That is, it can first determine the frequency feedforward term of each grid-type inverter based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system; then, for each grid-type inverter, based on the operating parameters of the grid-type inverter, the frequency feedforward term, and the control parameters of the grid-type inverter, it can further determine the frequency feedforward term of each grid-type inverter. The equations are used to calculate the phase angle and virtual internal electromotive force (EMF) amplitude of the grid-connected inverter. Then, based on the phase angle and virtual EMF amplitude, the three-phase modulation wave of the grid-connected inverter is determined. Finally, the operating state of the grid-connected inverter is controlled based on the three-phase modulation wave. Specifically, after pulse width modulation of the three-phase modulation wave, a duty cycle signal is generated. Based on the duty cycle signal, the switching transistors in the grid-connected inverter are controlled to turn on and off, thereby suppressing fluctuations in the grid operating frequency and ensuring the effective control of the grid operating frequency stability through the grid-connected inverter group.

[0055] In one embodiment, such as Figure 2 As shown, this method is applied to Figure 1 This embodiment uses a grid-connected inverter controller as an example for illustration. The method includes the following steps:

[0056] Step 202: Determine the frequency feedforward term of each grid-type inverter based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system.

[0057] The center frequency of a grid-connected inverter array is a core frequency value around which the array operates, reflecting its overall operating frequency characteristics. The rated angular frequency of the power system is a fixed value specified according to the power system's design standards and operating requirements. For example, when the rated frequency of the power system is 50Hz, the corresponding rated angular frequency is 2πf = 2π × 50 = 100π rad / s. The rated angular frequency of the power system is the reference frequency for stable operation. By comparing the difference between the center frequency of the grid-connected inverter array and the rated angular frequency of the power system, it can be determined whether the inverter's operating frequency deviates from the rated frequency of the power system, allowing for appropriate adjustments. The frequency feedforward term of the grid-connected inverter is used to compensate for frequency deviations in advance. Specifically, during inverter control, the frequency feedforward term compensates for potential frequency deviations in advance, thereby improving the inverter's response speed and control accuracy to frequency changes, enabling the inverter to adapt to power system frequency changes more quickly, and enhancing the stability of the power system.

[0058] Optionally, the center frequency can be calculated by first measuring the output frequency of each grid-type inverter in the grid-type inverter group; then, the frequency feedforward term of each grid-type inverter can be determined based on the difference between the center frequency and the rated angular frequency of the power system and the frequency feedforward coefficient.

[0059] Specifically, the frequency feedforward term for each grid-type inverter can be determined using the following calculation formula:

[0060] ;

[0061] In the formula, For the first Frequency feedforward term of individual grid-type inverters; The frequency feedforward coefficient can be determined based on the characteristics and empirical values ​​of the grid-type inverter. It is the center frequency of the grid-connected inverter group. It is the rated angular frequency of the power system; The difference obtained is the frequency deviation of the grid-type inverter group.

[0062] Step 204: For each grid-type inverter, calculate the phase angle and virtual internal electromotive force amplitude of the grid-type inverter based on its operating parameters, frequency feedforward term, and control equations.

[0063] The operating parameters of a grid-connected inverter include, but are not limited to, output voltage, output current, active power, reactive power, and output frequency. These parameters reflect the electrical state of the inverter during actual operation. The control equations of a grid-connected inverter are mathematical expressions describing the relationships between internal electrical quantities and the control strategy. Common control equations include the active power-frequency control equation (active power loop control equation) and the reactive power-voltage control equation (reactive power control equation). The function of the control equations is to calculate the phase angle and virtual internal electromotive force amplitude of the grid-connected inverter based on its operating parameters and frequency feedforward term. This allows for precise control of the output voltage and frequency of the grid-connected inverter, enabling it to operate in a predetermined manner to meet the requirements of the power system.

[0064] Optionally, the frequency feedforward term can be substituted into the control equations of the grid-type inverter. Combined with the inverter's operating parameters (such as active power, reactive power, etc.), the phase angle and virtual internal electromotive force amplitude can be obtained by solving the control equations. For example, the phase angle and virtual internal electromotive force amplitude can be obtained by solving the active-frequency control equation and the reactive-voltage control equation simultaneously.

[0065] Step 206: Determine the three-phase modulation wave of the grid-type inverter based on the phase angle and the amplitude of the virtual internal electromotive force.

[0066] In this context, the phase angle is the phase angle of the output voltage or current of the grid-connected inverter relative to a reference signal. It reflects the time position of the voltage or current, and thus determines the phase relationship of the three-phase modulation wave. The virtual internal electromotive force amplitude is an equivalent electromotive force calculated in the control model of the grid-connected inverter, used to determine the magnitude of the three-phase modulation wave amplitude. The three-phase modulation wave refers to the three sinusoidal signals used to control the on / off times of the power switching devices in the grid-connected inverter, corresponding to phases A, B, and C in the three-phase circuit. By controlling the on / off times of the power switching devices in the grid-connected inverter, the three-phase modulation wave converts DC power into three-phase AC power and can adjust the amplitude and frequency of the output voltage, thereby controlling the operating state of the grid-connected inverter and effectively controlling the stability of the power system's operating frequency.

[0067] Optionally, a three-phase modulation wave can be generated using trigonometric functions based on the phase angle and the amplitude of the virtual internal electromotive force. For example, the three-phase voltage command for each grid-type inverter can be obtained first using the following calculation formula. , and :

[0068] ;

[0069] ;

[0070] ;

[0071] In the formula, It is the first The virtual internal electromotive force amplitude of a grid-type inverter; It is the first Phase angle of a grid-type inverter.

[0072] The three-phase modulation waves of each grid-type inverter are then obtained using the following calculation formulas:

[0073] ;

[0074] ;

[0075] ;

[0076] In the formula, It is the A-phase voltage value of the filter capacitor in a grid-connected inverter; It is the B-phase voltage value of the filter capacitor in a grid-connected inverter; This is the C-phase voltage value of the filter capacitor in a grid-connected inverter. , and It can be obtained through a voltage sensor (such as a Hall voltage sensor); It is the A-phase current value of the filter inductor in a grid-connected inverter; It is the B-phase current value of the filter inductor in a grid-connected inverter; This is the C-phase current value of the filter inductor in a grid-connected inverter. , and It can be obtained through a current sensor (such as a Hall current sensor); It is the filter inductance of the grid-connected inverter, which can be calculated according to the existing formula for calculating filter inductance; It is the filter resistor of the grid-connected inverter; It is the proportional gain of the QPR (Quasi-Proportional Resonant) controller, which can be determined based on factors such as the open-loop gain and steady-state error requirements of the system. It is the damping coefficient of the QPR controller, which can be determined according to the damping ratio requirements of the system; It is the Laplace operator.

[0077] Step 208: Control the operating status of the grid-type inverter based on the three-phase modulation wave.

[0078] Among them, the operating status of grid-connected inverters is related to the operating frequency of the power system.

[0079] Optionally, the three-phase modulated wave can be input into the drive circuit of the grid-type inverter. The drive circuit controls the on / off times of the switching transistors within the grid-type inverter, thereby controlling the output voltage and frequency of the grid-type inverter. For example, pulse width modulation (PWM) technology can be used to adjust the on and off times of the switching transistors within the grid-type inverter based on the amplitude and phase of the three-phase modulated wave, so that the grid-type inverter outputs the required three-phase AC voltage.

[0080] The aforementioned grid operation frequency control method, by introducing a frequency feedforward term, can compensate for frequency deviations in advance, enabling the grid-connected inverter to respond more quickly to changes in power system frequency and improving the system's dynamic response performance. Furthermore, by accurately calculating the phase angle and virtual internal electromotive force amplitude, and generating a three-phase modulation wave based on these parameters, precise control of the grid-connected inverter output is achieved, thereby enhancing power system stability and reducing the impact of frequency fluctuations on the power system. In addition, this method can automatically adjust the operating state of the grid-connected inverter according to the actual operating conditions of the power system, enabling the grid-connected inverter to adapt to different power system environments, thus improving the system's adaptability and reliability.

[0081] In one embodiment, the operating parameters include a first operating parameter and a second operating parameter, and the control equations include an active power loop control equation and a reactive power control equation; such as Figure 3 As shown, based on the operating parameters, frequency feedforward term, and control equations of the grid-connected inverter, the phase angle and virtual internal electromotive force amplitude of the grid-connected inverter are calculated, including:

[0082] Step 302: Calculate the phase angle based on the first operating parameters, the frequency feedforward term, and the active power loop control equation.

[0083] The first operating parameter includes the active power reference value, active power measurement value, and virtual inertia of the grid-connected inverter. The active power loop control equation is used to simulate the inertia and damping characteristics of a synchronous generator, and the active power is controlled by adjusting the output angular frequency of the grid-connected inverter.

[0084] Optionally, the initial operating parameters can be obtained first, then these parameters can be substituted into the active power loop control equations and solved to obtain the output angular frequency of the grid-connected inverter. The phase angle can then be obtained based on the integral value of the output angular frequency and the frequency feedforward term. Here, the output angular frequency is the angular velocity of the output voltage or current of the grid-connected inverter as a function of time. By adjusting the output angular frequency, the phase angle difference between the output voltage of the grid-connected inverter and the power system voltage can be changed, thereby regulating the transmission of active power.

[0085] Step 304: Calculate the virtual internal electromotive force amplitude based on the second operating parameters, frequency feedforward term, and reactive power control equation.

[0086] The second operating parameter includes the reactive inertia coefficient, the rate of change of the virtual internal electromotive force (EMF) amplitude, the reactive-voltage droop coefficient, the rated output voltage, the reactive reference value, and the reactive measured value of the grid-connected inverter. The reactive power control equation is used to adjust the virtual EMF amplitude of the grid-connected inverter, thereby controlling the reactive power output of the inverter.

[0087] Optionally, the second operating parameters can be obtained first, and then these parameters can be substituted into the reactive power control equation to solve the equation and obtain the virtual internal electromotive force amplitude.

[0088] In this embodiment, by utilizing the active power loop control equation and the reactive power control equation respectively, combined with the corresponding operating parameters and frequency feedforward term, the active power and reactive power output of the grid-type inverter can be controlled independently and accurately, thereby helping to maintain system frequency stability and system voltage stability, and improving the power quality of the power system.

[0089] In one embodiment, such as Figure 4 As shown, the phase angle is calculated based on the first operating parameter, the frequency feedforward term, and the active power loop control equation, including:

[0090] Step 402: Calculate the output angular frequency of the grid-type inverter based on the first operating parameters and the active power loop control equation.

[0091] Optionally, the first operating parameter can be substituted into the active power loop control equation and solved using the numerical integration method to obtain the output angular frequency.

[0092] Step 404: The phase angle is obtained by summing the integral value of the output angular frequency and the frequency feedforward term.

[0093] Optionally, the sum of the integral value of the output angular frequency and the frequency feedforward term can be used as the phase angle of the grid-type inverter.

[0094] In this embodiment, by first calculating the output angular frequency of the grid-connected inverter and then calculating the phase angle based on the output angular frequency, precise control of the active power output of the inverter can be achieved. Precise control of the phase angle allows the active power output of the inverter to better track the active power reference value, thereby reducing the fluctuation of active power and improving the stability and power quality of the power system.

[0095] In one embodiment, the active power loop control equation is: .

[0096] in, For the first Virtual inertia of a grid-type inverter; The rated angular frequency of the grid-type inverter group; The rate of change of the angular frequency of the power system; For the first Damping coefficient of a grid-type inverter; For the first The output angular frequency of a grid-type inverter; For the first Active power reference value for individual grid-type inverters; For the first Active power measurement values ​​of individual grid-type inverters.

[0097] Specifically, the value of virtual inertia is a parameter that can be artificially set to simulate the inertial characteristics of a synchronous generator. The value of the rated angular frequency can be determined according to power system standards; for example, the rated angular frequency corresponding to the 50Hz grid operating frequency is 100π rad / s. The rate of change of the angular frequency of the power system can be measured in real time by a frequency measuring device (such as a high-precision frequency sensor) installed in the power system. The damping coefficient of the grid-type inverter can be determined according to the characteristics of the grid-type inverter. The output angular frequency of the grid-type inverter can be obtained in real time by installing a frequency measuring device, such as a Hall sensor or voltage transformer, at the output end of the grid-type inverter. The active power reference value of the grid-type inverter can be determined by the active power reference value issued by the upper-level dispatch center based on factors such as system load demand and power generation plan. The active power measurement value of the grid-type inverter can be obtained in real time by installing a power measuring device, such as a power sensor or energy meter, at the output end of the grid-type inverter.

[0098] In this embodiment, the output angular frequency of each grid-type inverter can be calculated using the above-mentioned active power loop control equations. Furthermore, the characteristics of synchronous generators can be simulated and precise control of active power can be achieved, thereby providing stability to the power system.

[0099] In one embodiment, It is determined based on the product of the matching coefficient of the grid-type inverter and the adaptive virtual inertia of the grid-type inverter.

[0100] Optionally, the matching coefficient of the grid-type inverter can be calculated first using the following formula. :

[0101] ;

[0102] In the formula, It is the first The damping coefficient of a grid-type inverter can be determined based on the damping characteristics of a synchronous generator, since the control of a grid-type inverter simulates the operating characteristics of a synchronous generator. The damping of a synchronous generator mainly comes from the damping winding in its rotor winding and the eddy current loss in its stator winding. It is the first The capacity of a grid-connected inverter can be determined based on the type of load and power requirements connected to it.

[0103] Then, calculate the adaptive virtual inertia of the grid-type inverter according to the following formula. :

[0104] ;

[0105] In the formula, It is a fixed total virtual inertia, which can be determined based on factors such as the total capacity of generators in the power system, load fluctuations, and the system's requirements for frequency stability. This is the adaptive coefficient for the rate of change of frequency, which can be determined based on the operational stability of the power system and the characteristics of the grid-connected inverter. Generally speaking, the worse the stability of the power system, the more adaptive the frequency change coefficient. The larger the value; This is the frequency deviation adaptive coefficient, which can be determined based on the power system's tolerance (sensitivity) to frequency deviation. When the frequency deviation of the power system is large, it can be appropriately increased. The value of enables grid-type inverters to respond to frequency deviations more quickly; It is the center frequency of the grid-connected inverter group. It is the rated angular frequency of the power system; The difference obtained is the frequency deviation of the grid-type inverter group; It is the rate of change of the center frequency of the grid-connected inverter group, which can be determined by installing a high-precision frequency measurement device, such as a Hall sensor or voltage transformer, at the common connection point of the grid-connected inverter group.

[0106] Finally, according to the calculation formula: Calculate the first Virtual inertia of a grid-type inverter .

[0107] It is understandable that in a system composed of multiple grid-connected inverters, there may be differences in capacity, performance, etc. between different grid-connected inverters. The matching coefficient can be used to reasonably distribute the power in the system according to the damping coefficient of each inverter. For example, a larger inverter has a larger matching coefficient and undertakes a relatively larger power change task in the system power regulation, thereby realizing the coordinated power distribution among multiple inverters and avoiding the situation where some grid-connected inverters are overloaded while other inverters are lightly loaded.

[0108] The adaptive virtual inertia of a grid-connected inverter is a quantity that dynamically adjusts according to changes in the power system frequency. The operating conditions of a power system are constantly changing; when the power system frequency is disturbed, it fluctuates. The adaptive virtual inertia can automatically adjust its size based on the rate of frequency change and frequency deviation. In other words, by dynamically adjusting the virtual inertia, the adaptive virtual inertia can better cope with various disturbances in the system, enhance the system's inertial response and damping characteristics, and improve the system's stability and anti-interference capability.

[0109] In this embodiment, since virtual inertia can simulate the inertial characteristics of synchronous generators, grid-connected inverters can absorb or release energy when the power system frequency changes, thus slowing down the rate of power system frequency change. The virtual inertia of each grid-connected inverter is determined based on the product of the matching coefficient and the adaptive virtual inertia of the grid-connected inverter. This allows each grid-connected inverter to provide a suitable virtual inertia according to its own actual situation, thereby enhancing the inertial response capability of the entire power system, reducing the amplitude of power system frequency fluctuations, and thus improving the stability of the power system.

[0110] In one embodiment, as described above (step 404), the sum obtained by adding the integral value of the output angular frequency and the frequency feedforward term is used as the phase angle of the grid-type inverter.

[0111] Specifically, the phase angle of each grid-type inverter can be calculated using the following formula:

[0112] ;

[0113] In the formula, For the first Phase angle of a grid-type inverter; For the first The integral value of the output angular frequency of a grid-type inverter; For the first Frequency feedforward term of a grid-type inverter.

[0114] In one embodiment, the reactive power control equation for a grid-connected inverter is: .

[0115] in, For the first The reactive inertia coefficient of a grid-type inverter; For the first The rate of change of the virtual internal electromotive force amplitude of a grid-type inverter; For the first Reactive power-voltage droop coefficient of individual grid-type inverters; This is the rated output voltage of the grid-connected inverter; For the first Reactive power reference value for individual grid-type inverters; For the first Reactive power measurement values ​​of individual grid-type inverters.

[0116] Specifically, the reactive power inertia coefficient of a grid-connected inverter can be determined based on its circuit structure, control strategy, and the characteristics of the connected power grid. For example, in a grid-connected inverter based on virtual synchronous generator control, the theoretical value of the reactive power inertia coefficient can be calculated based on the inverter's equivalent circuit model and electromagnetic transient equations, combined with the system's requirements for reactive power response speed and stability. The amplitude of the virtual internal electromotive force (EMF) of the grid-connected inverter can be measured in real time using a high-precision voltage sensor, and its rate of change can be calculated using a differential approximation method. The reactive power-voltage droop coefficient of the grid-connected inverter can be determined according to the power system's requirements for reactive power distribution and voltage regulation. Generally, larger-capacity grid-connected inverters can be set with a smaller droop coefficient, allowing them to undertake more tasks in reactive power regulation. The rated output voltage of the grid-connected inverter can be determined based on the rated voltage standard of the power grid to which it is connected. The reactive power reference value of a grid-connected inverter can be determined by the power system dispatch center based on the system's reactive power demand and the reactive power reference value reached under operating conditions. The reactive power measurement value of a grid-connected inverter can be determined in real time by reactive power measurement devices (such as power analyzers, power quality monitors, etc.) that measure the inverter's reactive power output power.

[0117] The reactive power control equation of the grid-type inverter in this embodiment can dynamically adjust the reactive power output of the grid-type inverter by introducing the rate of change of the virtual internal electromotive force amplitude and the reactive power-voltage droop coefficient, thereby maintaining the stability of the system voltage.

[0118] In one embodiment, the method further includes: determining the center frequency of the grid inverter group based on the virtual inertia coefficient of each grid inverter, the initial output angular frequency of each grid inverter, and a preset calculation formula.

[0119] The preset formula is: , The center frequency of the grid-type inverter group; For the first The virtual inertia coefficient of the grid-type inverter reflects the first The importance of a grid-type inverter in the formation of the center frequency of the entire grid-type inverter group is determined by the virtual inertia coefficient. The larger the virtual inertia coefficient, the greater the influence of the grid-type inverter on the center frequency of the grid-type inverter group. During the system frequency regulation process, the inverter with a larger virtual inertia coefficient will have a more significant effect on the center frequency due to the change in its output angular frequency. For the first The initial output angular frequency of a grid-type inverter.

[0120] Understandably, in traditional power systems, synchronous generators possess rotational inertia, enabling them to store or release energy when frequency disturbances occur in the power system, thereby suppressing rapid changes in the power system's operating frequency. The grid-connected inverter in this embodiment simulates this inertial characteristic of synchronous generators by introducing a virtual inertia coefficient. Furthermore, the larger the virtual inertia coefficient, the stronger the grid-connected inverter's ability to absorb or release energy when the power system frequency changes, thus better maintaining system frequency stability.

[0121] Optional, the first Virtual inertia coefficient of individual grid-type inverters It can be determined according to the following calculation formula:

[0122] ;

[0123] In the formula, It is the first Damping coefficient of a grid-type inverter; It is the first The capacity of a grid-type inverter.

[0124] The preset calculation formula in this embodiment, by comprehensively considering the virtual inertia coefficient and initial output angular frequency of each grid-type inverter, can accurately reflect the center frequency of the entire inverter group, which helps to ensure the accuracy and reliability of the final center frequency of the grid-type inverter group.

[0125] like Figure 5 As shown, the grid operating frequency control method of this application, compared with traditional technology, optimizes the damping of grid-connected inverter groups (multi-grid inverters) through frequency feedforward compensation when the grid operating frequency is disturbed. This enables the grid-connected inverters to output active power quickly, thereby improving the overall response speed of the multi-grid inverter grid-connected system. Furthermore, considering the differentiated requirements of the inertia response stage and the recovery stage, the virtual inertia of the multi-machine system can be adaptively adjusted, and dynamic coordination of the multi-grid inverter grid-connected system can be achieved through inertia allocation.

[0126] Specifically, the grid operating frequency control method of this application can be simulated by building a grid-connected system model of two grid-connected inverters in Simulink simulation software. In the simulation, the grid operating frequency is set to change from 50Hz to 49.9Hz at t=2s, and then from 49.9Hz to 50Hz at t=4s. The simulation results are as follows. Figure 6 to Figure 8 As shown, where, Figure 6 The power response waveform of a grid-type inverter using traditional control methods and with a small virtual inertia; Figure 7 The power response waveform of a grid-type inverter using traditional control methods and with a large virtual inertia; Figure 8The power response waveform of the grid-type inverter when using the grid operation frequency control method proposed in this application is shown.

[0127] The power response speed can be evaluated by comparing the rise time (the time it takes for the power to increase from 10% of the setpoint change to 90% of the final value). Figure 6 It can be seen that when using the traditional control method and with a small virtual inertia (J1+J2=0.1), the rise time of the power response is approximately 0.53 seconds; from Figure 7 It can be seen that when using the traditional control method and with a large virtual inertia (J1+J2=3), the rise time of the power response is approximately 0.28 seconds, and it exhibits a large overshoot; from Figure 8 As can be seen, under the power grid operating frequency control method proposed in this application, the rise time of the power response is approximately 0.22 seconds, with no overshoot. Therefore, when the power grid operating frequency changes, the power grid operating frequency control method proposed in this application can quickly provide power support.

[0128] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0129] Based on the same inventive concept, this application also provides a power grid operating frequency control device for implementing the power grid operating frequency control method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more power grid operating frequency control device embodiments provided below can be found in the limitations of the power grid operating frequency control method described above, and will not be repeated here.

[0130] In one embodiment, such as Figure 9 As shown, a power grid operating frequency control device is provided, comprising: a frequency feedforward term determination module 902, an internal control variable determination module 904, a three-phase modulation wave determination module 906, and a power grid operating frequency control module 908, wherein:

[0131] The frequency feedforward determination module 902 is used to determine the frequency feedforward of each grid-type inverter based on the difference between the center frequency of the grid-type inverter group and the rated angular frequency of the power system.

[0132] The internal control variable determination module 904 is used to calculate the phase angle and virtual internal electromotive force amplitude of each grid-type inverter based on the operating parameters, frequency feedforward term and control equation of the grid-type inverter.

[0133] The three-phase modulation wave determination module 906 is used to determine the three-phase modulation wave of the grid-type inverter based on the phase angle and the amplitude of the virtual internal electromotive force.

[0134] The grid operation frequency control module 908 is used to control the operating status of the grid-type inverter based on the three-phase modulation wave; the operating status of the grid-type inverter is related to the operating frequency of the power system.

[0135] In one embodiment, the internal control variable determination module 904 is further configured to: calculate the phase angle based on the first operating parameters, the frequency feedforward term, and the active power loop control equation; the first operating parameters include the active power reference value, the active power measurement value, and the virtual inertia of the grid-connected inverter; calculate the virtual internal electromotive force amplitude based on the second operating parameters, the frequency feedforward term, and the reactive power control equation; the second operating parameters include the reactive power inertia coefficient, the rate of change of the virtual internal electromotive force amplitude, the reactive power-voltage droop coefficient, the rated output voltage, the reactive power reference value, and the reactive power measurement value of the grid-connected inverter.

[0136] In one embodiment, the internal control variable determination module 904 is further configured to: calculate the output angular frequency of the grid-type inverter based on the first operating parameters and the active power loop control equation; and obtain the phase angle based on the integral value of the output angular frequency and the sum of the frequency feedforward term.

[0137] In one embodiment, the internal control variable determination module 904 is further configured to define the active power loop control equation as follows: ,in, For the first Virtual inertia of a grid-type inverter; The rated angular frequency of the grid-type inverter group; The rate of change of the angular frequency of the power system; For the first Damping coefficient of a grid-type inverter; For the first The output angular frequency of a grid-type inverter; For the first Active power reference value for individual grid-type inverters; For the first Active power measurement values ​​of individual grid-type inverters.

[0138] In one embodiment, the internal control variable determination module is also used to: define It is determined based on the product of the matching coefficient of the grid-type inverter and the adaptive virtual inertia of the grid-type inverter.

[0139] In one embodiment, the internal control variable determination module 904 is also used to define the reactive power control equation of the grid-connected inverter as follows: ,in, For the first The reactive inertia coefficient of a grid-type inverter; For the first The rate of change of the virtual internal electromotive force amplitude of a grid-type inverter; For the first Reactive power-voltage droop coefficient of individual grid-type inverters; This is the rated output voltage of the grid-connected inverter; For the first Reactive power reference value for individual grid-type inverters; For the first Reactive power measurement values ​​of individual grid-type inverters.

[0140] In one embodiment, the device is further configured to: determine the center frequency of the grid-type inverter group based on the virtual inertia coefficient of each grid-type inverter, the initial output angular frequency of each grid-type inverter, and a preset calculation formula; wherein the preset formula is: , The center frequency of the grid-type inverter group; For the first Virtual inertia coefficient of a grid-type inverter; For the first The initial output angular frequency of a grid-type inverter.

[0141] Each module in the aforementioned power grid operation frequency control device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0142] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10As shown, the computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a power grid operating frequency control method. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0143] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0144] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0145] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0146] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0147] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0148] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0149] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method of grid operating frequency control, characterized by, The method is applied to a power system comprising a grid-forming inverter bank, the grid-forming inverter bank comprising a plurality of grid-forming inverters connected in parallel, the method comprising: determining, according to a difference between a center frequency of the grid-forming inverter bank and a rated angular frequency of the power system, a frequency feedforward term of each of the grid-forming inverters; for each of the grid-forming inverters, calculating, according to an operating parameter of the grid-forming inverter, the frequency feedforward term, and a control equation of the grid-forming inverter, a phase angle and a virtual internal electromotive force amplitude of the grid-forming inverter; determining, according to the phase angle and the virtual internal electromotive force amplitude, a three-phase modulation wave of the grid-forming inverter; controlling, based on the three-phase modulation wave, an operating state of the grid-forming inverter; the operating state of the grid-forming inverter being related to an operating frequency of the power system.

2. The method of claim 1, wherein, The operating parameter comprises a first operating parameter and a second operating parameter, and the control equation comprises an active loop control equation and a reactive control equation; the calculating, according to the operating parameter of the grid-forming inverter, the frequency feedforward term, and the control equation of the grid-forming inverter, the phase angle and the virtual internal electromotive force amplitude of the grid-forming inverter comprises: calculating, according to the first operating parameter, the frequency feedforward term, and the active loop control equation, the phase angle; the first operating parameter comprising an active reference value, an active measurement value, and a virtual inertia of the grid-forming inverter; calculating, according to the second operating parameter, the frequency feedforward term, and the reactive control equation, the virtual internal electromotive force amplitude; the second operating parameter comprising a reactive inertia coefficient, a change rate of the virtual internal electromotive force amplitude, a reactive-voltage droop coefficient, a rated output voltage, a reactive reference value, and a reactive measurement value of the grid-forming inverter.

3. The method of claim 2, wherein, The calculating, according to the first operating parameter, the frequency feedforward term, and the active loop control equation, the phase angle comprises: calculating, according to the first operating parameter and the active loop control equation, an output angular frequency of the grid-forming inverter; obtaining, according to a sum of an integral value of the output angular frequency and the frequency feedforward term, the phase angle.

4. The method of claim 2, wherein, The active power loop control equation is as follows: ,in, For the first Virtual inertia of a grid-type inverter; The rated angular frequency of the grid-type inverter group; The rate of change of the angular frequency of the power system; For the first Damping coefficient of a grid-type inverter; For the first The output angular frequency of a grid-type inverter; For the first Active power reference value for individual grid-type inverters; For the first Active power measurement values ​​of individual grid-type inverters.

5. The method of claim 4, wherein, is determined according to a product value of a matching coefficient of the grid-forming inverter and an adaptive virtual inertia of the grid-forming inverter.

6. The method of claim 2, wherein, The reactive power control equation for the grid-type inverter is: ,in, For the first The reactive inertia coefficient of a grid-type inverter; For the first The rate of change of the virtual internal electromotive force amplitude of a grid-type inverter; For the first Reactive power-voltage droop coefficient of individual grid-type inverters; The rated output voltage of the grid-type inverter; For the first Reactive power reference value for individual grid-type inverters; For the first Reactive power measurement values ​​of individual grid-type inverters.

7. The method of claim 1, wherein, The method further comprises: The center frequency of the grid-type inverter group is determined based on the virtual inertia coefficient of each grid-type inverter, the initial output angular frequency of each grid-type inverter, and a preset calculation formula; wherein the preset formula is: , The center frequency of the grid-type inverter group; For the first Virtual inertia coefficient of a grid-type inverter; For the first The initial output angular frequency of a grid-type inverter.

8. A power grid operating frequency control device, characterized by, The device comprises: a frequency feedforward term determination module configured to determine, according to a difference between a center frequency of the grid-forming inverter bank and a rated angular frequency of the power system, a frequency feedforward term of each of the grid-forming inverters; an internal control variable determination module configured to, for each of the grid-forming inverters, calculate, according to an operating parameter of the grid-forming inverter, the frequency feedforward term, and a control equation of the grid-forming inverter, a phase angle and a virtual internal electromotive force amplitude of the grid-forming inverter; a three-phase modulation wave determination module configured to determine, according to the phase angle and the virtual internal electromotive force amplitude, a three-phase modulation wave of the grid-forming inverter; a power grid operating frequency control module configured to control, based on the three-phase modulation wave, an operating state of the grid-forming inverter; the operating state of the grid-forming inverter being related to an operating frequency of the power system. 9.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-8 when the computer program is executed by the processor. The processor, when executing the computer program, implements the steps of the method of any one of claims 1 to 7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program, which is executed by a processor, implements the steps of the method according to any one of claims 1 to 7.

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