Power control method and grid-connected inverter system

Abstract

The embodiment of the present application discloses a power control method and a grid-connected inverter system, the method comprising: obtaining a voltage signal u input by the grid-connected inverter system abc , for the voltage signal u abc Perform integration processing; wherein, the integration processing includes a differential link with a small time constant. abc Frequency lock control is performed to obtain the frequency change rate of the grid-connected inverter system. An inertia reference is obtained based on the frequency change rate, and power tracking control is performed based on the inertia reference. By employing the embodiments of the present application, fluctuations in the frequency change rate can be reduced, filtering delay can be reduced, and dynamic response speed can be improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics and new energy power generation technology, and in particular to a power control method and a grid-connected inverter system. Background Art

[0002] As the global energy crisis and environmental pollution become increasingly prominent, renewable energy generation, represented by photovoltaic power generation, wind power generation, and hydropower generation, is rapidly developing and will occupy a significant position in the future energy mix. With the widespread application of new energy power electronic equipment in power systems, the frequency stability of power systems is becoming increasingly important.

[0003] Currently, traditional power systems utilize power generation units to participate in system frequency regulation and detect changes in grid frequency. If the rate of change of the grid frequency deviates from a preset threshold, the control system of the generator units in the grid automatically adjusts the increase or decrease of the unit's active power, providing inertia active power support. This can limit grid frequency fluctuations and stabilize the grid frequency. However, this approach is limited by frequency change rate detection accuracy, high-frequency interference introduced by differentials, and filtering delays. Furthermore, the response time of the virtual inertia is relatively long. Summary of the Invention

[0004] The embodiments of the present application provide a power control method and a grid-connected inverter system, which can avoid high-frequency disturbances caused by differentiation, improve the response time of the overall virtual inertia, and enhance the adaptability to weak networks.

[0005] In a first aspect, an embodiment of the present application provides a power control method, which is applied to a grid-connected inverter system, comprising: obtaining a voltage signal u input by the grid-connected inverter system; abc , for the voltage signal u abc Perform integration processing; wherein, the integration processing includes a differential link with a small time constant. abc Perform frequency locking control to obtain a frequency change rate of the grid-connected inverter system, obtain an inertia setting based on the frequency change rate, and perform power tracking control based on the inertia setting.

[0006] By adopting the embodiments of the present application, the voltage signal obtained from the grid-connected inverter input is integrated and the voltage signal after integration is frequency-locked, thereby reducing the fluctuation of the frequency change rate, avoiding the high-frequency disturbance caused by differentiation, improving the response time of the overall virtual inertia, and enhancing the adaptability to weak networks.

[0007] In one possible design, the method further includes: abc After integration processing, the error signal ε is obtained vAnd the grid signal qv'. v The grid signal qv' is frequency-locked and controlled to obtain the frequency change rate of the grid-connected inverter system. Based on this design, the voltage signal after integration can be frequency-locked, thereby reducing the fluctuation of the frequency change rate and avoiding high-frequency disturbances caused by differentiation.

[0008] In a possible design, the voltage signal u after integration is abc The equation for frequency locking control is:

[0009]

[0010] Where, ω' is the grid frequency of the grid-connected inverter system, k is the gain coefficient, s is the Laplace operator, T FLL For the time period.

[0011] In one possible design, the frequency change rate is filtered to obtain a smoothly varying frequency change rate. Based on such a design, the embodiment of the present application can mitigate the fluctuation of the frequency change rate.

[0012] In one possible design, when the frequency change rate is positive and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned. Based on this design, embodiments of the present application can enhance adaptability to weak networks.

[0013] In one possible design, when the frequency change rate is negative and outside the dead zone, or the frequency is outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned. Based on this design, embodiments of the present application can enhance adaptability to weak networks.

[0014] In a second aspect, an embodiment of the present application further provides a grid-connected inverter system, comprising a power converter and a controller, wherein the controller is electrically connected to the power converter, and the controller is used to control the switch state in the power converter, and is used to: obtain a voltage signal u input to the grid-connected inverter system abc , for the voltage signal u abc Perform integration processing; wherein, the integration processing includes a differential link with a small time constant; the voltage signal u after integration processing abc Perform frequency locking control to obtain the frequency change rate of the grid-connected inverter system; obtain an inertia setting according to the frequency change rate, and perform power tracking control according to the inertia setting.

[0015] The grid-connected inverter system of the embodiment of the present application integrates the acquired voltage signal and performs frequency locking control on the voltage signal after integration, thereby reducing the fluctuation of the frequency change rate, avoiding high-frequency disturbances caused by differentiation, improving the response time of the overall virtual inertia, and enhancing the adaptability to weak networks.

[0016] In one possible design, the grid-connected inverter system also includes an energy storage device, which includes multiple power output branches. Each of the power output branches includes a battery unit and a power supply unit. The battery unit is electrically connected to the power supply unit. The output ends of the multiple power output branches are connected in parallel to output electrical energy to the power converter.

[0017] In one possible design, the controller is further configured to: abc After integration processing, the error signal ε is obtained v and the grid signal qv'; the error signal ε v The controller performs frequency lock control on the integrated voltage signal qv' to obtain the frequency change rate of the grid-connected inverter system. Based on this design, the controller can perform frequency lock control on the voltage signal after integration, thereby reducing fluctuations in the frequency change rate and avoiding high-frequency disturbances caused by differentiation.

[0018] In one possible design, the controller is used to process the voltage signal u after integration. abc The equation for frequency locking control is:

[0019]

[0020] Where, ω' is the grid frequency of the grid-connected inverter system, k is the gain coefficient, s is the Laplace operator, T FLL For the time period.

[0021] In one possible design, the controller is further configured to filter the frequency change rate to obtain a smoothly varying frequency change rate. Based on such a design, the embodiment of the present application can mitigate fluctuations in the frequency change rate.

[0022] In one possible design, the controller is further configured to: when the frequency change rate is positive and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, unidirectionally assign a value to the frequency change rate of the current beat. Based on this design, embodiments of the present application can enhance adaptability to weak networks.

[0023] In one possible design, the controller is further configured to: when the frequency change rate is negative and outside the dead zone, or when the frequency is outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, unidirectionally assign a value to the frequency change rate of the current beat. Based on this design, embodiments of the present application can enhance adaptability to weak networks.

[0024] The power control method and grid-connected inverter system provided by the embodiments of the present application can reduce the fluctuation of the frequency change rate in the frequency-locked loop, improve the response time of the overall virtual inertia, and also enhance the adaptability to weak networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the grid-connected inverter system according to an embodiment of the present application.

[0026] Figure 2 This is a schematic structural diagram of an energy storage device according to an embodiment of the present application.

[0027] Figure 3 This is another structural schematic diagram of the energy storage device according to an embodiment of the present application.

[0028] Figure 4 This is another structural diagram of the power control system according to an embodiment of the present application.

[0029] Figure 5 This is a schematic structural diagram of the improved SOGI unit according to an embodiment of the present application.

[0030] Figure 6 The Bode diagram of the embodiment of the present application and the Bode diagram of the prior art are shown.

[0031] Figure 7 This is a structural diagram of the improved FLL unit according to an embodiment of the present application.

[0032] Figure 8 This is a flow chart of a power control method according to an embodiment of the present application.

[0033] Figure 9 This is another flow chart of the power control method according to an embodiment of the present application.

[0034] Figure 10 This is a schematic diagram of the structure of the controller of an embodiment of the present application.

[0035] Description of main component symbols

[0036] Power control system 100 Power System 200 Power grid 210 transformer 220 Controller 10 Voltage and current acquisition module 12 Processing Module 14 power converters 20 Energy storage devices 30 battery cells 31 Power supply unit 32 Photovoltaic unit 33 Coordinate transformation unit 141 Improved SOGI unit 142 Improved FLL unit 143 Positive sequence extraction unit 144 Filter unit 146 Weak network adaptability enhancement unit 147 Virtual inertia unit 148 Power Control Unit 149

[0037] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0038] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0039] It should be noted that when an element is considered to be “connected” to another element, it may be directly connected to the other element or there may be a centrally disposed element. When an element is considered to be “disposed on” another element, it may be directly disposed on the other element or there may be a centrally disposed element.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] See also Figure 1 , Figure 1 FIG2 is a block diagram of a grid-connected inverter system according to an embodiment of the present application. The grid-connected inverter system may include a power control system 100 and a power system 200. The power control system 100 in this embodiment may be electrically connected to the power system 200. It will be appreciated that the power control system 100 can improve the inertia response speed of power electronic equipment, effectively support the stability of the grid frequency, and enhance the adaptability of inertia control in weak grid conditions.

[0042] In a possible application scenario, such as Figure 1 As shown, the power system 200 may include a power grid 210 and a transformer 220. The power grid 210 may be electrically connected to the transformer 220, and the transformer 220 may be electrically connected to the power control system 100. It will be understood that the power control system 100 may serve as a power electronic device to output power to the power system 200.

[0043] In one possible implementation, the transformer 220 may be used to receive the power output by the power control system 100, convert the voltage of the power, and transmit the converted power to the power grid 210. Thus, the power grid 210 may use the received power to power a load.

[0044] It is understood that the power control system 100 in the embodiment of the present application may include a controller 10, a power converter 20, and an energy storage device 30. It is understood that in one possible scenario, the energy storage device 30 may be an energy storage system (ESS).

[0045] Specifically, in the implementation process of the present application, the controller 10 can be coupled to the power converter 20 and the transformer 220, the energy storage device 30 can be coupled to the power converter 20, and the power converter 20 can be coupled to the transformer 220. It can be understood that in one embodiment, the controller 10 can be used to collect operating parameters of the power system 200. For example, in a specific scenario, the controller 10 can collect electrical quantities such as voltage and current of the power system 200. Therefore, the controller 10 can analyze and process the collected parameters to obtain control signals for controlling the on and off of switches in the power converter 20.

[0046] The controller 10 in the embodiment of the present application can also be used to obtain the voltage signal u input by the grid-connected inverter system. abc , and the voltage signal u abc It is understood that the integration process includes a differential step with a small time constant.

[0047] In one embodiment, the controller 10 can also process the voltage signal u after the integration process. abc By performing frequency locking control, the frequency change rate of the grid-connected inverter system can be obtained. Therefore, the controller 10 can obtain the inertia setting according to the frequency change rate and perform power tracking control according to the inertia setting.

[0048] Based on such a design, the grid-connected inverter system of the embodiment of the present application can reduce the fluctuation of the frequency change rate, avoid high-frequency disturbances caused by differentiation, improve the response time of the overall virtual inertia, and enhance the adaptability to weak networks.

[0049] It is understood that the energy storage device 30 is an energy storage device that can be used to provide power to the power converter 20. The power converter 20 can be used to transmit power to the power grid 210. In some possible implementations, the energy storage device 30 can provide power to the power converter 20 through a photovoltaic storage DC coupling method or an energy storage DC coupling method.

[0050] In one possible implementation, Figure 2As shown, the energy storage device 30 may include multiple battery units 31, multiple power supply units 32, and multiple photovoltaic units 33. It is understood that the power supply unit 32 may be any one of a current source, a voltage source, or a voltage conversion unit, which is not limited in this application.

[0051] It can be understood that a battery cell 31 is connected in series with a power supply unit 32 to form a first power output branch, and a photovoltaic cell 33 is connected in series with a power supply unit 32 to form a second power output branch. The output ends of multiple first power output branches and the output ends of multiple second power output branches are connected in parallel. Based on this design, the energy storage device 30 can output electrical energy to the power converter 20.

[0052] In another possible implementation, Figure 3 As shown, the energy storage device 30 may include a plurality of battery units 31 and a plurality of power supply units 32 .

[0053] It is understood that a battery unit 31 is connected in series with a power supply unit 32 to form a power output branch. The output ends of multiple power output branches are connected in parallel. Based on this design, the energy storage device 30 can output electrical energy to the power converter 20.

[0054] See also Figure 4 The following will illustrate the grid-connected inverter system provided in the embodiment of the present application with examples in combination with the accompanying drawings and actual application scenarios.

[0055] Figure 4 This is a schematic diagram of the structure of a controller disclosed in an embodiment of the present application. The controller 10 can be used to execute Figure 8 or Figure 9 For details, please refer to the power control method described in part or all of the steps. Figure 8 or Figure 9 The relevant description in will not be repeated here.

[0056] In the embodiment of the present application, the controller 10 may include a voltage and current acquisition module 12 and a processing module 14 .

[0057] The voltage and current acquisition module 12 is used to acquire operating parameters of the power system 200. For example, the voltage and current acquisition module 12 can acquire the voltage and current of the power grid 210. In one embodiment, the voltage and current acquisition module 12 can acquire the current and voltage output by the power system 200.

[0058] In this embodiment, the voltage and current acquisition module 12 may transmit the acquired voltage and current of the power grid 210 to the processing module 14 , and the processing module 14 may process and analyze the voltage and current to improve the inertia response speed of the power electronic device.

[0059] It can be understood that in one possible implementation, in this embodiment, the processing module 14 can obtain the voltage signal u input by the grid-connected inverter system. abc , and the voltage signal u abc In a specific implementation, the processing module 14 may include a coordinate conversion unit 141, a modified second order generator integrator (M-SOGI) unit 142, a modified frequency locked loop (M-FLL) unit 143, a positive sequence extraction unit 144, a filtering unit 146, a weak network adaptability enhancement unit 147, a virtual inertia unit 148, and a power control unit 149.

[0060] It can be understood that the voltage and current acquisition module 12 in this embodiment can acquire the voltage signal u output by the power system 200. abc The coordinate conversion unit 141 can be used to convert the collected voltage signal u abc The three-phase coordinate system and the two-phase coordinate system are converted to obtain the voltage components αβ in the two-phase stationary coordinate system. That is, the coordinate conversion unit 141 can output the voltage signal u αβ .

[0061] It can be understood that in the embodiment of the present application, the voltage signal u αβ It can include the voltage signal u α And the voltage signal u β .

[0062] In a possible implementation, the voltage signal u α And the voltage signal u β The voltage signal u can be input to the two improved SOGI units 142 respectively. α and the voltage signal u β After the integration processing of the improved SOGI unit 142 , the input signal of the improved FLL unit 143 can be obtained.

[0063] Specifically, one of the improved SOGI units 142 can be configured to generate a voltage signal u according to the grid frequency ω and the voltage signal u. α To obtain three components, the three components can be respectively the error signal ε vα, voltage signal u' a , voltage signal qv' a .

[0064] Furthermore, another improved SOGI unit 142 can be configured to generate a voltage signal u according to the grid frequency ω and the voltage signal u β To obtain three components, the three components can be respectively the error signal ε vβ , voltage signal u' β , voltage signal qv' β .

[0065] It is understood that the processing module 14 in the embodiment of the present application can also process the voltage signal u after the integration process. abc , frequency locking control is performed, and then the frequency change rate of the grid-connected inverter system can be obtained.

[0066] In this embodiment, the positive sequence extraction unit 144 can be used to receive the voltage signal u output by the coordinate conversion unit 141. αβ , and according to the received voltage signal u αβ Perform positive and negative sequence separation to output positive sequence voltage component u α + and the positive sequence voltage component u β + to the improved FLL unit 143.

[0067] It can be understood that in some scenarios, the transfer function of the traditional second-order generalized integrator is:

[0068]

[0069]

[0070] From the above formulas (1) and (2), we can see that the error signal ε of the second-order generalized integrator is v By multiplying the qv' signal after the second-order low-pass filter, the control equation of the frequency-locked loop can be obtained:

[0071]

[0072] It can be seen that the traditional second-order generalized integrator will cause the frequency change rate dω / dt obtained by the frequency-locked loop to fluctuate greatly, which may increase the delay of the low-pass filter.

[0073] Therefore, the embodiments of the present application propose an improved second-order generalized integrator unit and an improved frequency-locked loop unit. The improved SOGI unit and the improved FLL unit in the embodiments of the present application can solve the above-mentioned problems.

[0074] In this embodiment, the implementation block diagram of the improved SOGI unit is as follows Figure 5 It is shown in that the damping term can be constructed on the controlled object of the improved FLL unit by improving the second-order generalized integrator and the frequency locked loop.

[0075] like Figure 5 As shown, in the embodiment of the present application, the improved SOGI unit can abc An integration process is performed, wherein the integration process may include a differential link with a small time constant. Therefore, the embodiment of the present application may improve the SOGI unit by adding a partial differential link with a small time constant.

[0076] Specifically, a partial differential link with a small time constant can be connected in series to the branch of the voltage signal u' in the improved SOGI unit, or a partial differential link with a small time constant can be connected in series to the branch of the voltage signal qv' in the second-order generalized integrator unit. For example, in the improved SOGI unit 142, the front stage of the integrator in the branch of the voltage signal u' and the front stage of the integrator in the branch of the voltage signal qv' are both connected in series to a partial differential link with a small time constant. As a result, the ε generated in the improved SOGI unit va When the signal and qv' signal pass through the frequency-locked loop control, a damping term can be constructed on the controlled object of the frequency-locked loop.

[0077] It can be understood that in the embodiment of the present application, after the improvement of the improved SOGI unit 142, the improved FLL unit 143 can process the voltage signal u after the integration process. abc To perform frequency locking control, the improved FLL unit 143 in this embodiment processes the voltage signal u after the integration process. abc The equation for frequency locking control is:

[0078]

[0079] Where, ω' is the grid frequency of the grid-connected inverter system, k is the gain coefficient, s is the Laplace operator, T FLL is the time period of the improved FLL unit 143.

[0080] like Figure 6 , which is a Bode diagram obtained by using the improved SOGI unit 142 of the embodiment of the present application. It can be seen that by introducing a partial differential link with a small time constant in the improved SOGI unit, the phase information of the controlled object of the improved FLL unit 143 will change slowly when it changes.

[0081] In this embodiment, the improved FLL unit 143 can be used to perform frequency locking control and extract the frequency change rate, thereby constructing a damping term on the controlled object of the frequency locked loop unit, thereby reducing the fluctuation of the frequency change rate dω / dt.

[0082] In this embodiment, the implementation block diagram of the improved FLL unit is as follows: Figure 7 As shown in FIG, since the improved SOGI unit may attenuate the signal at the center frequency, the improved FLL unit needs to compensate for the positive sequence component of the normalized parameter. The compensation coefficients may be m and n, respectively.

[0083] In this embodiment, the frequency change rate dω / dt output by the improved FLL unit 143 can be filtered by the filtering unit 146 to obtain a smoothly varying frequency change rate, thereby mitigating fluctuations in the frequency change rate. In one possible implementation, the filtering unit 146 can be implemented using a second-order low-pass filtering unit and a sliding average filtering unit.

[0084] It is understood that the frequency change rate dω / dt can be the rate of change of the grid frequency during the disturbance process, which can be measured and recorded in real time by a phase-locked loop or a frequency-locked loop. Furthermore, the frequency change rate dω / dt can be processed by the weak network adaptability enhancement unit 147, thereby significantly enhancing weak network adaptability.

[0085] It can be understood that when the frequency change rate is positive and outside the dead zone, and the grid frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, the final output frequency change rate is assigned a unidirectional value. Based on this design, when the frequency fluctuates in a weak grid, the inertia active power can be prevented from fluctuating along with it, thereby preventing system oscillations.

[0086] It can be understood that when the frequency change rate is negative and outside the dead zone, and the grid frequency is also outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, the final output frequency change rate is assigned a unidirectional value. Based on this design, when the frequency fluctuates in a weak grid, the inertia active power can be prevented from fluctuating along with it, thereby preventing system oscillations.

[0087] It can be understood that in the embodiment of the present application, if the inertia trigger condition is met, the inertia must be enabled for a period of time. Even if the frequency change rate is less than the threshold during this period, the inertia will be enabled to ensure that the power grid will not be further deteriorated due to inertia when the frequency oscillates.

[0088] It can be understood that in a possible implementation, the virtual inertia unit 148 can calculate the inertia setting according to the frequency change rate, and transmit the inertia setting to the power control unit 149.

[0089] The power control unit 149 may receive the inertia setting and perform power tracking control according to the inertia setting, thereby completing inertia frequency modulation.

[0090] It is understood that the division of the various modules in the controller 10 is only for illustration. In other embodiments, the controller 10 can be divided into different modules as needed to complete all or part of the functions of the controller 10. The implementation of each module in the controller 10 provided in the embodiment of the present application can be in the form of a computer program. The specific implementation of each module in the embodiment of the present application can also refer to Figure 8 or Figure 9 For details, please refer to the following specific embodiment of the power control method, which will not be described in detail here.

[0091] See also Figure 8 , which is a flow chart of a power control method provided in one embodiment of the present application. The power control method of this embodiment can be applied to control Figure 1 as well as Figure 4 The power control system 100 shown in FIG. 1 may include the following steps:

[0092] Step S81: Acquire a voltage signal of the grid-connected inverter system.

[0093] It is understood that the following will be combined Figure 4 The grid-connected inverter system shown in FIG. 1 is used for illustration. In an embodiment of the present application, the power control system 100 can obtain operating parameters of the power grid 210. For example, the voltage and current acquisition module 12 in the power control system 100 can acquire parameter data such as the voltage and current of the power grid 210. The voltage and current acquisition module 12 can acquire the current and voltage output by the power system 200. For example, in an embodiment of the present application, the voltage signal u in the grid-connected inverter system can be obtained. abc .

[0094] Step S82: the voltage signal u abc An integration process is performed, wherein the integration process includes a differentiation component with a small time constant.

[0095] In this embodiment, the processing module 14 in the power control system 100 can also analyze and process the collected voltage and current. For example, the coordinate conversion unit 141 in the processing module 14 can analyze and process the collected voltage signal uabc The three-phase coordinate system and the two-phase coordinate system are converted to obtain the voltage components αβ in the two-phase stationary coordinate system. That is, the coordinate conversion unit 141 can obtain the voltage signal u αβ .

[0096] It can be understood that in the embodiment of the present application, the voltage signal u αβ It can include the voltage signal u α And the voltage signal u β The voltage signal u α and the voltage signal u β After the integration processing, the signals are input to the improved FLL unit 143 .

[0097] Specifically, one of the improved SOGI units 142 can be configured to generate a voltage signal u according to the grid frequency ω and the voltage signal u. α To obtain three components, the three components can be respectively the error signal ε vα , voltage signal u' a , voltage signal qv' a Furthermore, another improved SOGI unit 142 can be configured to generate a voltage signal u according to the grid frequency ω and the voltage signal u β To obtain three components, the three components can be respectively the error signal ε vβ , voltage signal u' β , voltage signal qv' β Wherein, the signal u' a A second-order bandpass filter can be used to extract the signal corresponding to the AC frequency. The signal qv' a It can be the output signal of the second-order low-pass filter, which can make the original voltage signal u α A 90-degree phase lag is applied.

[0098] In this embodiment, a partial differential link with a small time constant can be connected in series to the branch of the voltage signal u' in the improved SOGI unit, or a partial differential link with a small time constant can be connected in series to the branch of the voltage signal qv' in the second-order generalized integrator unit. For example, in the improved SOGI unit 142, the front stage of the integrator in the branch of the voltage signal u' and the front stage of the integrator in the branch of the voltage signal qv' are both connected in series to a partial differential link with a small time constant. As a result, the ε generated in the improved SOGI unit 142 is va When the signal and qv' signal pass through the frequency-locked loop control, a damping term can be constructed on the controlled object of the frequency-locked loop.

[0099] Step S83: The voltage signal u after integration is processed. abc Perform frequency locking control to obtain the frequency change rate of the grid-connected inverter system.

[0100] It can be understood that in the embodiment of the present application, after the improvement of the improved SOGI unit 142, the improved FLL unit 143 can process the voltage signal u after the integration process. abc To perform frequency locking control, the improved FLL unit 143 in this embodiment processes the voltage signal u after the integration process. abc The equation for frequency locking control is:

[0101]

[0102] In this embodiment, the implementation block diagram of the improved FLL unit 143 is as follows: Figure 7 As shown in FIG, since the improved SOGI unit may attenuate the signal at the center frequency, the improved FLL unit needs to compensate for the positive sequence component of the normalized parameter. The compensation coefficients may be m and n, respectively.

[0103] Step S84: Calculate the inertia setting according to the frequency change rate.

[0104] The virtual inertia unit 148 in this embodiment can calculate the inertia reference and transmit the inertia reference to the power control unit 149 .

[0105] Step S85: Perform power tracking control according to the inertia setting.

[0106] The power control unit 149 in this embodiment can receive the inertia setting and perform power tracking control according to the inertia setting, thereby completing inertia frequency modulation.

[0107] See also Figure 9 , which is a flow chart of a power control method provided by another embodiment of the present application. The power control method of this embodiment can also be applied to control Figure 1 as well as Figure 4 The power control method of this embodiment may include the following steps:

[0108] Step S91: Acquire a voltage signal of the grid-connected inverter system.

[0109] It is understood that the following will be combined Figure 4The grid-connected inverter system shown in FIG. 1 is used for illustration. In an embodiment of the present application, the power control system 100 can obtain operating parameters of the power grid 210. For example, the voltage and current acquisition module 12 in the power control system 100 can acquire parameter data such as the voltage and current of the power grid 210. The voltage and current acquisition module 12 can acquire the current and voltage output by the power system 200. For example, in an embodiment of the present application, the voltage signal u in the grid-connected inverter system can be obtained. abc .

[0110] Step S92: the voltage signal u abc An integration process is performed, wherein the integration process includes a differentiation component with a small time constant.

[0111] Step S93: the voltage signal u after integration processing abc Perform frequency locking control to obtain the frequency change rate of the grid-connected inverter system.

[0112] Step S94: filtering the frequency change rate.

[0113] The frequency change rate dω / dt output by the improved FLL unit 143 in this embodiment may be filtered by the second-order low-pass filter unit 146 and the sliding average filter unit 146 to obtain a smoothly varying frequency change rate.

[0114] Step S95: enhancing the adaptability to weak networks.

[0115] After the frequency locking control by the improved FLL unit 143 , the frequency change rate dω / dt may be processed by the weak network adaptability enhancement unit 147 , thereby significantly enhancing the weak network adaptability.

[0116] It is understood that when the frequency change rate is a positive value and is outside the dead zone, and the grid frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, a one-way assignment is performed on the frequency change rate of the final output. Based on such a design, it is possible to avoid the inertia active power fluctuating along with the frequency under a weak network, thereby avoiding system oscillation. It is understood that when the frequency change rate is a negative value and is outside the dead zone, and the grid frequency is outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, a one-way assignment is performed on the frequency change rate of the final output. Based on such a design, it is possible to avoid the inertia active power fluctuating along with the frequency under a weak network, thereby avoiding system oscillation.

[0117] It can be understood that in the embodiment of the present application, if the inertia trigger condition is met, the inertia must be enabled for a period of time. Even if the frequency change rate is less than the threshold during this period, the inertia will be enabled to ensure that the power grid will not be further deteriorated due to inertia when the frequency oscillates.

[0118] Step S96: Calculate the inertia setting according to the frequency change rate.

[0119] The virtual inertia unit 148 in this embodiment can calculate the inertia reference and transmit the inertia reference to the power control unit 149 .

[0120] Step S97: Perform power tracking control according to the inertia setting.

[0121] The power control unit 149 in this embodiment can receive the inertia setting and perform power tracking control according to the inertia setting, thereby completing inertia frequency modulation.

[0122] See Figure 10 FIG. 1 is another structural diagram of the controller 10 provided in an embodiment of the present application. In one embodiment, the controller 10 includes a memory 101 and at least one processor 102. It should be understood by those skilled in the art that Figure 10 The structure of the controller 10 shown does not constitute a limitation of the embodiments of the present application. The controller 10 may also include more or less other hardware or software than shown in the figure, or a different component arrangement.

[0123] In some embodiments, the controller 10 includes a terminal that can automatically perform numerical calculations and / or information processing according to pre-set or stored instructions, and its hardware includes but is not limited to a microprocessor, an application-specific integrated circuit, a programmable gate array, a digital processor, and an embedded device. In some embodiments, the memory 101 is used to store program code and various data. The memory 101 may include a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0124] In some embodiments, the at least one processor 102 may include an integrated circuit, such as a single packaged integrated circuit, or multiple packaged integrated circuits with the same or different functions, including a combination of a microprocessor, a digital processing chip, a graphics processor, and various control chips. The at least one processor 102 is the control core (Control Unit) of the controller, and executes the various functions of the controller 10 and processes data by running or executing programs or modules stored in the memory 101 and calling data stored in the memory 101.

[0125] The above-mentioned integrated unit implemented in the form of a software functional module can be stored in a computer-readable storage medium. The above-mentioned software functional module is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, terminal, or network device, etc.) or a processor to execute part of the method described in each embodiment of the present application.

[0126] The memory 101 stores program codes, and the at least one processor 102 can call the program codes stored in the memory 101 to execute related functions. In one embodiment of the present application, the memory 101 stores a plurality of instructions, and the plurality of instructions are executed by the at least one processor 102 to implement the virtual inertia control method. Specifically, the specific implementation method of the at least one processor 102 for the above instructions can be referred to Figure 8 or Figure 9 The description of the relevant steps in the corresponding embodiments will not be repeated here.

[0127] The power control method employed in the embodiments of this application can reduce fluctuations in the frequency change rate (df / dt), reduce filtering steps, improve inertia response speed, and more effectively support grid frequency stability. During the inertia power calculation process, a weak network adaptability enhancement module is introduced. This utilizes a one-way frequency change rate assignment and an inertia trigger hysteresis loop to improve weak network adaptability and effectively address weak network oscillation issues.

[0128] An embodiment of the present application further provides a storage medium, wherein the storage medium stores computer instructions, which, when executed on a computing device, enable the computing device to execute the power control method provided in the aforementioned embodiment.

[0129] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. Any appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application, as long as they are within the spirit of the present application.

Claims

1. A power control method, applied to a grid-connected inverter system, characterized in that: The power control method comprises: Obtain the voltage signal u input by the grid-connected inverter system abc , for the voltage signal u abc Performing an integration process; wherein the integration process includes a differential link with a small time constant; For the voltage signal u abc After integration processing, the error signal ε is obtained v and grid signal qv ' , for the error signal ε v and the grid signal qv ' Performing frequency locking control to obtain a frequency change rate of the grid-connected inverter system; An inertia setting is obtained according to the frequency change rate, and power tracking control is performed according to the inertia setting.

2. The power control method according to claim 1, wherein: After the integration process, the voltage signal u abc The equation for frequency locking control is: ； Among them, ω ' is the grid frequency of the grid-connected inverter system, k is the gain coefficient, s is the Laplace operator, T FLL For the time period.

3. The power control method according to claim 1 or 2, wherein: Before obtaining the inertia reference according to the frequency change rate, the method further includes: The frequency change rate is filtered to obtain a smoothly changing frequency change rate.

4. The power control method according to claim 3, wherein: Also includes: When the frequency change rate is positive and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned.

5. The power control method according to claim 3, wherein: Also includes: When the frequency change rate is negative and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned.

6. A grid-connected inverter system, characterized in that: The grid-connected inverter system includes a power converter and a controller, wherein the controller is electrically connected to the power converter and configured to control a switch state in the power converter and: Obtain the voltage signal u input by the grid-connected inverter system abc , for the voltage signal u abc Performing an integration process; wherein the integration process includes a differential link with a small time constant; For the voltage signal u abc After integration processing, the error signal ε is obtained v and grid signal qv ' , for the error signal ε v and the grid signal qv ' Performing frequency locking control to obtain a frequency change rate of the grid-connected inverter system; An inertia setting is obtained according to the frequency change rate, and power tracking control is performed according to the inertia setting.

7. The grid-connected inverter system according to claim 6, characterized in that: The grid-connected inverter system also includes an energy storage device, which includes multiple power output branches. Each of the power output branches includes a battery unit and a power supply unit. The battery unit is electrically connected to the power supply unit. The output ends of the multiple power output branches are connected in parallel to output electrical energy to the power converter.

8. The grid-connected inverter system according to claim 6 or 7, characterized in that: The controller is further configured to filter the frequency change rate to obtain a smoothly changing frequency change rate.

9. The grid-connected inverter system according to claim 8, characterized in that: The controller is also used for: When the frequency change rate is positive and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is greater than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned.

10. The grid-connected inverter system according to claim 8, wherein: The controller is also used for: When the frequency change rate is negative and outside the dead zone, and the frequency is outside the dead zone, if the frequency change rate of the current beat is less than the frequency change rate of the previous beat, the frequency change rate of the current beat is unidirectionally assigned.

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