Grid-connected inverter frequency support control method based on direct current capacitor dynamic coupling

Abstract

The invention relates to a grid-connected inverter frequency support control method based on direct-current capacitor dynamic coupling, and the method comprises the steps: collecting and processing the three-phase current output by the alternating-current side of a three-phase grid-connected inverter, and obtaining a three-phase synchronous resonance suppression voltage compensation component; collecting and processing the direct current side capacitor voltage of the three-phase grid-connected inverter to obtain a modulation voltage phase of the three-phase grid-connected inverter; collecting and processing reactive power of an alternating current side of the grid-connected inverter to obtain a modulation voltage amplitude; calculating a fundamental wave three-phase voltage modulation quantity according to the modulation voltage phase and the modulation voltage amplitude; and superposing the fundamental wave three-phase voltage modulation quantity and the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal. According to the invention, the grid-connected inverter can actively sense the real-time frequency fluctuation state of the alternating-current power grid, and provides corresponding inertia power support or absorbs redundant electric energy when the frequency changes sharply, so that the effect of reducing the frequency fluctuation amplitude and the change rate is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy grid-connected power generation, and in particular to a frequency support control method for a grid-connected inverter based on dynamic coupling of direct current capacitors. Background Art

[0002] With the vigorous development of new energy, its proportion in the power system is increasing, becoming an important way to alleviate the pressure of fossil energy and promote the sustainable use of energy. Grid-connected inverters, as key interface devices between new energy and the power grid, play a vital role in the high-quality power conversion and control of new energy such as wind and light. However, due to the lack of mechanical rotating parts, power electronic devices cannot provide frequency support for the power grid independently during the power generation process. With the high penetration of new energy such as photovoltaics and wind power in the power grid, the system's rotational inertia will be reduced, making the frequency more prone to transient instability under active disturbance accidents, such as excessive absolute value of the frequency change rate, frequency extreme deviation exceeding the safety threshold, etc., which may cause power outages.

[0003] In order to deal with this problem, the existing technology improves the control strategy of the grid-connected inverter to give it a certain frequency support capability. The mainstream frequency support control methods include virtual synchronous machine technology, active power instruction correction method based on frequency deviation, and active power instruction correction method based on frequency change rate. The core idea of ​​these methods is to use the control flexibility of the grid-connected inverter to provide inertial power support when active power disturbance occurs in the system, thereby effectively reducing the absolute value of the frequency change rate and the frequency extreme value deviation. However, this type of method requires the grid-connected inverter to have a common physical condition, that is, the DC side needs to be equipped with an energy storage device to provide or absorb active power when needed.

[0004] Although the prior art provides some effective frequency support control methods, they all rely on energy storage devices on the DC side of the grid-connected inverter. For distributed new energy power sources without energy storage devices, the above mainstream frequency support control methods cannot be effectively implemented because their DC side cannot provide instantaneous active output or absorption. This limits the application of grid-connected inverters without energy storage in auxiliary control of grid frequency. Summary of the invention

[0005] In view of this, it is necessary to provide a frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors to solve the above-mentioned defects of the prior art.

[0006] In order to solve the above problems, in a first aspect, an embodiment of the present invention provides a frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors, comprising:

[0007] The three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed through a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component;

[0008] The capacitor voltage on the DC side of the three-phase grid-connected inverter is collected and processed by an active damping controller to obtain the modulation voltage phase of the three-phase grid-connected inverter;

[0009] The reactive power on the AC side of the grid-connected inverter is collected and processed by an integral controller to obtain the modulation voltage amplitude of the three-phase grid-connected inverter;

[0010] The fundamental three-phase voltage modulation amount is calculated according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0011] Preferably, the three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed by a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component, including:

[0012] Collect the three-phase current output from the AC side of the three-phase grid-connected inverter;

[0013] The three-phase current is converted into d-axis and q-axis current components by abc / dq coordinate transformation;

[0014] The synchronous resonance damper is used to receive the current components on the d and q axes, and the d and q components of the synchronous resonance suppression voltage are calculated;

[0015] The d and q components of the synchronous resonance suppression voltage are converted into three-phase synchronous resonance suppression voltage compensation components through dq / abc coordinate transformation.

[0016] Preferably, the frequency domain expression equation of the synchronous resonance damper is:

[0017]

[0018] In the formula, R l is the resonance damping resistance, ω c is the cutoff frequency of the high-pass filter, and s is a complex variable.

[0019] Preferably, the collecting and processing of the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter includes:

[0020] Collecting the DC side capacitor voltage and comparing it with a preset DC side capacitor reference voltage to obtain a voltage error;

[0021] The active damping controller calculates a frequency dynamic correction compensation amount according to the voltage error amount;

[0022] The frequency dynamic correction compensation amount is compared with the rated frequency reference amount, the comparison result is processed through an integral link, and the modulation voltage phase of the three-phase grid-connected inverter is output.

[0023] Preferably, the frequency domain expression equation of the active damping controller is:

[0024]

[0025] In the formula, G d (s) is the transfer function of the active damping controller, C is the DC side capacitance of the grid-connected inverter, T h is the inertia time constant, R d is the virtual damping resistor, K C is the voltage-frequency coupling amplification factor.

[0026] Preferably, the collecting and processing of the reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter includes:

[0027] Collect reactive power on the AC side of the three-phase grid-connected inverter;

[0028] After comparing the reactive power measurement value with the preset reactive power reference value, the modulation voltage amplitude of the three-phase grid-connected inverter is output through the integral link;

[0029] The calculation formula of the modulation voltage amplitude of the three-phase grid-connected inverter is:

[0030] M=k I ∫[Q ref (t)-Q m (t)]dt

[0031] Where M is the modulation voltage amplitude, Q ref (t) is the reactive power reference value, Q m (t) is the reactive power measurement value of the AC side of the three-phase grid-connected inverter, k I is the integral control coefficient.

[0032] Preferably, the calculation formula of the modulation signal of the three-phase grid-connected inverter is:

[0033] w a =Mcosθ+v fa

[0034]

[0035] In the formula, w a , w b , w c are the modulation signals of phases a, b, and c of the three-phase grid-connected inverter, respectively, and v fa 、v fb、v fc They are the a, b, and c phase synchronous resonance suppression voltage compensation components respectively.

[0036] In a second aspect, an embodiment of the present invention provides a grid frequency support control system for a grid-connected inverter based on dynamic coupling of DC capacitors, comprising:

[0037] The synchronous resonance damping module is used to collect the three-phase current outputted from the AC side of the three-phase grid-connected inverter, and process it through the synchronous resonance damper to obtain the three-phase synchronous resonance suppression voltage compensation component;

[0038] A virtual synchronous control module is used to collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter;

[0039] Reactive power control module, used to collect and process reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter;

[0040] The modulation instruction generation module is used to calculate the fundamental three-phase voltage modulation amount according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0041] In a third aspect, the present invention further provides an electronic device, including a memory and a processor, wherein:

[0042] The memory is used to store programs;

[0043] The processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in the grid-connected inverter frequency support control method based on DC capacitor dynamic coupling as described in the embodiment of the first aspect of the present invention.

[0044] In a fourth aspect, the present invention further provides a computer-readable storage medium for storing computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors as described in the embodiment of the first aspect of the present invention.

[0045] The grid-connected inverter frequency support control method based on dynamic coupling of DC capacitors provided by the present invention can actively sense the real-time frequency fluctuation state of the AC power grid by dynamically associating the DC side capacitor voltage with the frequency of the AC power grid. When the frequency drops sharply, the DC side capacitor releases energy to provide inertial power support for the AC side power grid, thereby reducing the rate and amplitude of the frequency drop; when the frequency rises sharply, the DC side capacitor will actively absorb excess electrical energy on the AC side, thereby slowing down the rate and height of the frequency rise; when the frequency is in a stable operating state, the DC side capacitor energy is in a balanced state. The grid-connected inverter frequency support control method proposed by the present invention can effectively support the frequency stability of power systems with a high proportion of power electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A flow chart of a frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors provided by the present invention;

[0047] Figure 2 The frequency support control principle diagram of the grid-connected inverter provided by the present invention;

[0048] Figure 3 A comparison diagram of system frequency response using the frequency support control method proposed by the present invention and the traditional constant power control method;

[0049] Figure 4 A comparison diagram of the system frequency change rate using the frequency support control method proposed by the present invention and the traditional constant power control method;

[0050] Figure 5 A structural block diagram of a frequency support control system for a grid-connected inverter based on dynamic coupling of DC capacitors provided by the present invention;

[0051] Figure 6 This is a structural block diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0053] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] The high penetration of new energy sources such as photovoltaics and wind power in the power grid will cause the system's rotational inertia to decrease, making the frequency more prone to transient instability under active disturbance accidents. In order to address this problem, the prior art improves the control strategy of the grid-connected inverter and gives it a certain frequency support capability, namely, the frequency support control method. The mainstream frequency support control methods include virtual synchronous machine technology, active power instruction correction method based on frequency deviation, and active power instruction correction method based on frequency change rate. Although the prior art provides some effective frequency support control methods, they all rely on energy storage devices on the DC side of the grid-connected inverter. For distributed new energy power sources without energy storage devices, the above-mentioned mainstream frequency support control methods cannot be effectively implemented because their DC side cannot provide instantaneous active power output or absorption. This limits the application of grid-connected inverters without energy storage in grid frequency support and increases the economic burden of the system.

[0055] In view of this, the present invention provides a frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors, which only uses the electric energy stored in the DC side capacitors to provide inertial power support for the power grid, without the need to add energy storage devices on the DC side, thereby achieving effective support for the grid frequency and ensuring the economy of the system. In addition, the grid-connected inverter under this control method can also achieve self-synchronization with the power grid without using a phase-locked loop. The following will be explained and introduced through multiple embodiments.

[0056] Figure 1 The flowchart of the frequency support control method of the grid-connected inverter based on the dynamic coupling of DC capacitors provided by the present invention is as follows. Figure 1 As shown, the frequency support control method of the grid-connected inverter based on the dynamic coupling of DC capacitors includes steps S1 to S4, wherein:

[0057] Step S1, collecting the three-phase current outputted by the AC side of the three-phase grid-connected inverter, processing it through a synchronous resonance damper, and obtaining a three-phase synchronous resonance suppression voltage compensation component.

[0058] Figure 2 This is a frequency support control principle diagram of the grid-connected inverter provided by the present invention. Figure 2 The DC side of the three-phase (a-phase, b-phase, c-phase) grid-connected inverter includes capacitors for stabilizing the DC voltage, and the AC side of the three-phase grid-connected inverter is connected to the grid. The three-phase grid-connected inverter is used to convert the DC power generated by the photovoltaic array into AC power and connect it to the grid. The pulse width modulation (PWM) signal is provided to the three-phase grid-connected inverter through the PWM generator.

[0059] In step S1, first, the three-phase current outputted by the AC side of the three-phase grid-connected inverter is collected to provide accurate current data for subsequent analysis.

[0060] Next, the three-phase current is converted into d and q axis current components by abc / dq coordinate transformation. The current in the three-phase stationary coordinate system (abc coordinate system) is converted into the current component in the rotating coordinate system (dq coordinate system) by dq transformation (conversion from rectangular coordinate system to polar coordinate system).

[0061] Furthermore, the synchronous resonance damper is used to receive the current components on the d and q axes, and the d and q components of the synchronous resonance suppression voltage are calculated; wherein the frequency domain expression equation of the synchronous resonance damper is:

[0062]

[0063] In the formula, R l is the resonance damping resistance, ω c is the cutoff frequency of the high-pass filter, and s is a complex variable.

[0064] Finally, the d and q components of the synchronous resonance suppression voltage are converted into three-phase synchronous resonance suppression voltage compensation components through dq / abc coordinate transformation. Here, the voltage compensation component in the dq coordinate system is converted back to the three-phase synchronous resonance suppression voltage compensation component in the abc coordinate system in order to match the original three-phase current signal.

[0065] In this embodiment, the synchronous resonant damper analyzes the resonant components in the d-axis and q-axis current components based on a specific frequency domain expression equation and calculates corresponding voltage compensation components. These compensation components are used to offset the resonance phenomenon and improve the stability of the system.

[0066] Step S2, collecting and processing the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter.

[0067] Specifically, in step S2, first, the DC link capacitor voltage is collected and compared with a preset DC link capacitor reference voltage to obtain a voltage error.

[0068] Next, the active damping controller is used to calculate the frequency dynamic correction compensation based on the voltage error. The active damping controller receives the voltage error as input, and after signal processing, outputs the frequency dynamic correction compensation. The frequency domain expression equation of the active damping controller is:

[0069]

[0070] In the formula, G d (s) is the transfer function of the active damping controller, C is the DC side capacitance of the grid-connected inverter, T h is the inertia time constant, R d is the virtual damping resistor, K C is the voltage-frequency coupling amplification factor.

[0071] Finally, the frequency dynamic correction compensation is compared with the rated frequency reference to obtain the frequency error. The frequency error is integrated through the integral link, and the modulation voltage phase of the three-phase grid-connected inverter is obtained according to the integral result.

[0072] In this implementation, by adjusting the output frequency and phase of the three-phase grid-connected inverter, the three-phase grid-connected inverter can respond to the frequency fluctuation of the power grid and provide or absorb energy when necessary to improve the stable operation capability of the power grid frequency. This embodiment implements virtual synchronous control through sampling, comparison, active damping control, integral link and other steps, so that the grid-connected inverter can better interact and operate synchronously with the power grid.

[0073] Step S3, collecting and processing the reactive power of the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter.

[0074] Specifically, the reactive power on the AC side of the three-phase grid-connected inverter is collected. After comparing the reactive power measurement value with the preset reactive power reference value, the modulation voltage amplitude of the three-phase grid-connected inverter is output through the integral link. Integral control helps to eliminate the steady-state error of the system and achieve precise control of reactive power.

[0075] The calculation formula of the modulation voltage amplitude of the three-phase grid-connected inverter is:

[0076] M=k I ∫[Q ref (t)-Q m (t)]dt

[0077] Where M is the modulation voltage amplitude, Q ref (t) is the reactive power reference value, Q m (t) is the reactive power measurement value of the AC side of the three-phase grid-connected inverter, k I is the integral control coefficient.

[0078] Step S4, calculating the fundamental three-phase voltage modulation amount according to the modulation voltage phase and the modulation voltage amplitude; superimposing the fundamental three-phase voltage modulation amount and the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0079] Specifically, the fundamental three-phase voltage modulation amount is calculated according to the modulation voltage phase obtained in step S2 and the modulation voltage amplitude obtained in step S3. Then, the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component obtained in step S1 to obtain the three-phase grid-connected inverter modulation signal. In this embodiment, by superimposing the fundamental three-phase voltage modulation amount and the synchronous resonance suppression voltage compensation component, the resonance suppression strategy is integrated into the control of the three-phase grid-connected inverter, ensuring that the three-phase grid-connected inverter achieves the purpose of frequency support control while being able to damp the synchronous resonance phenomenon caused by the inductive line.

[0080] Among them, the calculation formula of the modulation signal of the three-phase grid-connected inverter is:

[0081] w a =Mcosθ+v fa

[0082]

[0083] In the formula, w a , w b , w c are the modulation signals of phases a, b, and c of the three-phase grid-connected inverter, respectively, and v fa 、v fb 、v fc They are the a, b, and c phase synchronous resonance suppression voltage compensation components respectively.

[0084] The grid-connected inverter frequency support control method based on dynamic coupling of DC capacitors provided by the present invention can actively sense the real-time frequency fluctuation state of the AC power grid by dynamically associating the DC side capacitor voltage with the frequency of the AC power grid. When the frequency drops sharply, the DC side capacitor releases energy to provide inertial power support for the AC side power grid, thereby reducing the rate and amplitude of the frequency drop; when the frequency rises sharply, the DC side capacitor will actively absorb excess electrical energy on the AC side, thereby slowing down the rate and height of the frequency rise; when the frequency is in a stable operating state, the DC side capacitor energy is in a balanced state. The grid-connected inverter frequency support control method proposed by the present invention can effectively support the frequency stability of power systems with a high proportion of power electronics.

[0085] In a preferred embodiment of the present invention, Figure 3 A comparison diagram of system frequency responses using the frequency support control method proposed by the present invention (the "proposed method" in the figure) and the traditional constant power control method (the "conventional method" in the figure); Figure 4 The following is a comparison chart of the system frequency change rate using the frequency support control method proposed by the present invention and the traditional constant power control method. Figure 3 and Figure 4It can be seen that a sudden increase in active power disturbance will cause the system frequency to drop, but compared with the traditional constant power control method, the frequency support control method proposed in the present invention can increase the lowest point of the frequency drop by about 0.05Hz and reduce the initial frequency change rate by about 0.2Hz / s. It can be seen from the results of the embodiment that the grid-connected inverter frequency support control method based on DC capacitor dynamic coupling provided by the present invention can autonomously sense the system active power disturbance, and provide a certain inertial power support for the grid frequency when the system frequency drops, thereby effectively improving the transient stability characteristics of the frequency and enhancing the frequency stability capability of the new energy high penetration power system.

[0086] Figure 5 The structural block diagram of the frequency support control system of the grid-connected inverter based on DC capacitor dynamic coupling provided by the present invention is shown in FIG. Figure 5 The grid-connected inverter frequency support control system 500 based on DC capacitor dynamic coupling includes:

[0087] The synchronous resonance damping module 501 is used to collect the three-phase current outputted from the AC side of the three-phase grid-connected inverter, and process it through the synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component;

[0088] The virtual synchronization control module 502 is used to collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter;

[0089] The reactive power control module 503 is used to collect and process the reactive power of the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter;

[0090] The modulation instruction generating module 504 is used to calculate the fundamental three-phase voltage modulation amount according to the modulation voltage phase and the modulation voltage amplitude; and superimpose the fundamental three-phase voltage modulation amount with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0091] The grid-connected inverter frequency support control system based on DC capacitor dynamic coupling provided by the present invention executes the grid-connected inverter frequency support control method based on DC capacitor dynamic coupling provided by the above-mentioned embodiments through the above-mentioned modules. The grid-connected inverter frequency support control method based on DC capacitor dynamic coupling has been described in detail in the above-mentioned embodiments, and this embodiment will not be repeated here.

[0092] The grid-connected inverter frequency support control system based on DC capacitor dynamic coupling provided by the present invention is intended to improve the frequency stability of a high-proportion power electronic power system. The grid-connected inverter is enabled to actively sense the real-time frequency fluctuation state of the AC power grid and provide corresponding inertial power support or absorb excess electric energy when the frequency changes sharply, so as to achieve the effect of reducing the frequency fluctuation amplitude and change rate.

[0093] Figure 6 The structural block diagram of the electronic device provided by the present invention is as follows: Figure 6 As shown, the present invention also provides an electronic device, and the electronic device 600 can be a computing device such as a mobile terminal, a desktop computer, a notebook, a palm computer, and a server. The electronic device 600 includes a processor 601 and a memory 602, wherein the memory 602 stores a grid-connected inverter frequency support control program 606 based on DC capacitor dynamic coupling.

[0094] In some embodiments, the memory 602 may be an internal storage unit of a computer device, such as a hard disk or memory of the computer device. In other embodiments, the memory 602 may also be an external storage device of the computer device, such as a plug-in hard disk equipped on the computer device, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Furthermore, the memory 602 may also include both an internal storage unit of the computer device and an external storage device. The memory 602 is used to store application software and various types of data installed on the computer device, such as program codes for installing the computer device. The memory 602 can also be used to temporarily store data that has been output or is to be output. In one embodiment, when the grid-connected inverter frequency support control program 606 based on DC capacitor dynamic coupling is executed by the processor 601, the following steps are implemented:

[0095] The three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed through a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component;

[0096] Collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter;

[0097] Collect and process the reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter;

[0098] The fundamental three-phase voltage modulation amount is calculated according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0099] In some embodiments, the processor 601 can be a central processing unit (CPU), a microprocessor or other data processing chip, used to run the program code or process data stored in the memory 602, such as executing a grid-connected inverter frequency support control program based on DC capacitor dynamic coupling.

[0100] This embodiment further provides a computer-readable storage medium, on which a grid-connected inverter frequency support control program based on DC capacitor dynamic coupling is stored. When the grid-connected inverter frequency support control program based on DC capacitor dynamic coupling is executed by a processor, the following steps are implemented:

[0101] The three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed through a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component;

[0102] Collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter;

[0103] Collect and process the reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter;

[0104] The fundamental three-phase voltage modulation amount is calculated according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

[0105] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors, characterized in that: include: The three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed through a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component; Collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter; Collect and process the reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter; The fundamental three-phase voltage modulation amount is calculated according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

2. The frequency support control method for grid-connected inverter based on DC capacitor dynamic coupling according to claim 1, characterized in that: The three-phase current outputted from the AC side of the three-phase grid-connected inverter is collected and processed by a synchronous resonance damper to obtain a three-phase synchronous resonance suppression voltage compensation component, including: Collect the three-phase current output from the AC side of the three-phase grid-connected inverter; The three-phase current is converted into d-axis and q-axis current components by abc / dq coordinate transformation; The synchronous resonance damper is used to receive the current components on the d and q axes, and the d and q components of the synchronous resonance suppression voltage are calculated; The d and q components of the synchronous resonance suppression voltage are converted into three-phase synchronous resonance suppression voltage compensation components through dq / abc coordinate transformation.

3. The frequency support control method for grid-connected inverter based on DC capacitor dynamic coupling according to claim 2, characterized in that: The frequency domain expression equation of the synchronous resonant damper is: In the formula, H l (s) is the transfer function of the synchronous resonant damper, R l is the resonance damping resistance, ω c is the cutoff frequency of the high-pass filter, and s is a complex variable.

4. The method for controlling the frequency support of a grid-connected inverter based on dynamic coupling of DC capacitors according to claim 1, characterized in that: The collecting and processing of the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter includes: Collecting the DC side capacitor voltage and comparing it with a preset DC side capacitor reference voltage to obtain a voltage error; The active damping controller calculates a frequency dynamic correction compensation amount according to the voltage error amount; The frequency dynamic correction compensation amount is compared with the rated frequency reference amount, the comparison result is processed through an integral link, and the modulation voltage phase of the three-phase grid-connected inverter is output.

5. The frequency support control method for grid-connected inverter based on DC capacitor dynamic coupling according to claim 4, characterized in that: The frequency domain expression equation of the active damping controller is: In the formula, G d (s) is the transfer function of the active damping controller, C is the DC side capacitance of the grid-connected inverter, T h is the inertia time constant, R d is the virtual damping resistor, K C is the voltage-frequency coupling amplification factor.

6. The frequency support control method for grid-connected inverter based on DC capacitor dynamic coupling according to claim 5, characterized in that: The collecting and processing of the reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter includes: Collect reactive power on the AC side of the three-phase grid-connected inverter; After comparing the reactive power measurement value with the preset reactive power reference value, the modulation voltage amplitude of the three-phase grid-connected inverter is output through the integral link; The calculation formula of the modulation voltage amplitude of the three-phase grid-connected inverter is: M=k I ∫[Q ref (t)-Q m (t)]dt Where M is the modulation voltage amplitude, Q ref (t) is the reactive power reference value, Q m (t) is the reactive power measurement value of the AC side of the three-phase grid-connected inverter, k I is the integral control coefficient.

7. The method for controlling the frequency support of a grid-connected inverter based on dynamic coupling of DC capacitors according to claim 6, characterized in that: The calculation formula of the modulation signal of the three-phase grid-connected inverter is: w a =Mcosθ+v fa In the formula, w a , w b , w c are the modulation signals of phases a, b, and c of the three-phase grid-connected inverter, respectively, and v fa 、v fb 、v fc They are the a, b, and c phase synchronous resonance suppression voltage compensation components respectively.

8. A grid frequency support control system for a grid-connected inverter based on dynamic coupling of DC capacitors, characterized in that: include: The synchronous resonance damping module is used to collect the three-phase current outputted from the AC side of the three-phase grid-connected inverter, and process it through the synchronous resonance damper to obtain the three-phase synchronous resonance suppression voltage compensation component; A virtual synchronous control module is used to collect and process the DC side capacitor voltage of the three-phase grid-connected inverter to obtain the modulation voltage phase of the three-phase grid-connected inverter; Reactive power control module, used to collect and process reactive power on the AC side of the grid-connected inverter to obtain the modulation voltage amplitude of the three-phase grid-connected inverter; The modulation instruction generation module is used to calculate the fundamental three-phase voltage modulation amount according to the modulation voltage phase and the modulation voltage amplitude; the fundamental three-phase voltage modulation amount is superimposed with the synchronous resonance suppression voltage compensation component to obtain a three-phase grid-connected inverter modulation signal.

9. An electronic device, It is characterized in that comprising a memory and a processor, wherein: The memory is used to store programs; The processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in the grid-connected inverter frequency support control method based on DC capacitor dynamic coupling as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the frequency support control method for a grid-connected inverter based on dynamic coupling of DC capacitors as described in any one of claims 1 to 7.

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