Synchronization control method and device for composite current of network-forming inverter and computer readable storage medium

Abstract

The invention discloses a composite current synchronous control method and device for a network-forming inverter and a computer readable storage medium, and belongs to the technical field of inverter control, and the method comprises the steps: in a synchronous control loop, symmetrically introducing dq-axis grid-connected current components, carrying out the subtraction of the dq-axis grid-connected current components with a reference value, and outputting a dual angular frequency adjustment variable through inertia and droop links, thereby achieving the synchronous control of the dq-axis grid-connected current components; and a synchronous angular frequency adjusting quantity is generated through compounding, and a required synchronous phase angle theta is further obtained through an integration link. According to the invention, an instantaneous power calculator in the traditional network construction type control is omitted, and the synchronization of the network construction type inverter and the network voltage is realized by using the d-axis and q-axis network current components of the system, so that the robustness of the network construction type inverter to the network impedance change can be effectively enhanced, and better synchronization stability is achieved under a strong network.

Description

Technical Field

[0001] The present application relates to the field of inverter control, and in particular to a method, device and computer-readable storage medium for composite current synchronization control of a grid-type inverter. Background Art

[0002] As the connection interface between the new energy distributed power generation system and the power grid, the grid-connected inverter plays a vital role in the new power system. With the increase in the penetration rate of new energy, some grid-connected inverters need to change from the traditional current source control mode to the voltage source control mode. This type of inverter is called a grid-connected inverter, and its main function is to build the grid voltage and frequency, providing basic support for the stable operation of the power system.

[0003] Relevant research results show that the grid-connected inverter exhibits good stability under weak grid conditions and can effectively maintain system operation. However, under strong grid conditions, its synchronization performance is relatively weak, which is prone to sub- / super-synchronous oscillation problems. In addition, due to the intermittent, random and volatile characteristics of high-proportion renewable energy generation, the grid impedance will undergo dynamic changes in strength and weakness, which undoubtedly poses a severe challenge to the safe, stable and high-quality operation of the grid-connected inverter. Existing improvement strategies usually enhance synchronization stability by introducing additional damping links or virtual impedance control on the basis of traditional power synchronization control. However, the existing strategies still have certain limitations and urgently need further innovation and optimization to meet the growing demand for renewable energy grid connection. Summary of the invention

[0004] The present application aims to provide a method, device and computer-readable storage medium for composite current synchronization control of a grid-connected inverter with strong robustness.

[0005] In order to achieve the above-mentioned purpose, the technical solution of this application is: A composite current synchronous control method for a grid-connected inverter comprises the following steps: Step S1, detecting the inductor current i L_x , and perform coordinate transformation to obtain dq Inductor current in coordinate system i L_n ; Detect grid current i g_x , and perform coordinate transformation to obtain dq Grid current in coordinate system i g_n ; Detect output voltage v o_x , and perform coordinate transformation to obtain dq Output voltage in coordinate system v o_n; Among them, the subscript x express a , b , c , subscript n express d, q ; Step S2, according to d Axis grid current reference value i gref_d and d Axis grid current i g_d , calculate d Shaft angular frequency adjustment Δ ω d ; Step S3, according to q Axis grid current reference value i gref_q and q Axis grid current i g_q , calculate q Shaft angular frequency adjustment Δ ω q ; Step S4, according to d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n , calculate the output voltage phase angle of the grid-type inverter θ ; Step S5, according to q Axis grid current reference value i gref_q , Grid-connected rated voltage amplitude V n and q Axis grid current i g_q , calculate the output voltage amplitude reference of the grid-type inverter V ref ; Step S6: According to the grid-type inverter output voltage phase angle θ Reference to the output voltage amplitude of the grid-connected inverter V ref , use the voltage reference calculation formula to get the output voltage reference value v oref_n ; The output voltage reference value v oref_n include: d Output voltage reference value in the axis direction voref_d and q Output voltage reference value in the axis direction v oref_q ; Step S7, output voltage reference value v oref_n With output voltage v o_n The error is fed into the voltage controller G v , get the inductor current reference value i Lref_n ; Set the inductor current reference value i Lref_n and the inductor current i L_n The error is fed into the current controller G i , and get the modulated wave v m_n ; Modulate the wave v m_n Converted to the three-phase stationary coordinate system, we get v m_x , PWM control signal is generated by sinusoidal pulse width modulation.

[0006] Optionally, step S2 includes: d Axis grid-connected current reference value i gref_d and d Axis grid current i g_d Make the difference, then multiply by the inertia link m d ω d / ( s + ω d ) d Shaft angular frequency adjustment Δ ω d ;in, m d for d Shaft grid-connected current-frequency droop coefficient, ω d is the turning angular frequency of the inertia link, s is the Laplace coefficient. Optionally, in step S3, q Axis grid-connected current reference value i gref_q and q Axis grid current i g_q Make a difference and then multiply it by the high-pass filter link m qs / ( s + ω c ) q Shaft angular frequency adjustment Δ ω q ;in, m q for q Shaft grid-connected current-frequency droop coefficient, ω c is the corner frequency of the high-pass filter.

[0007] Optionally, in step S4, d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n Add and pass the integration phase 1 / s Get the phase angle of the grid inverter output voltage θ .

[0008] Optionally, in step S5, q Axis grid current reference value i gref_q and q Axis grid current i g_q Make a difference, multiply by the inertia link n q ω q / ( s + ω q ) generates a voltage variation ΔV, which is proportional to the grid-connected rated voltage amplitude V n Add together to get the amplitude reference of the grid inverter output voltage V ref ,in, n q for q Axis grid-connected current-voltage droop coefficient, ω q is the turning angular frequency of the inertia link.

[0009] Optionally, in step S6, the voltage reference calculation formula is: , .

[0010] Optionally, the voltage controllerG v It is a PI regulator.

[0011] Optionally, the current controller G i It is a proportional-integral controller.

[0012] A device, comprising: one or more processors; a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors execute a grid-type inverter composite current synchronization control method as described in any one of the above.

[0013] A computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, the computer program implements a grid-type inverter composite current synchronization control method as described in any one of the above.

[0014] The composite current synchronous control method of the grid-type inverter provided in the present application utilizes the system d Axis and q The axis grid current component realizes the synchronization of the grid-forming inverter and the grid voltage, omitting the instantaneous power calculation link in the traditional grid-forming inverter control, enabling the grid-forming inverter to operate reliably and stably, and effectively improving the robustness of the grid-forming inverter to grid impedance changes and the stability under strong grid conditions, thereby realizing plug-and-play in the grid.

[0015] In order to make the above features and advantages of the application more obvious and easy to understand, the following embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The schematic diagram of the system structure of the grid-type inverter under the traditional control method.

[0017] Figure 2 This is a flow chart of the composite current synchronous control method of the grid-type inverter provided in this application.

[0018] Figure 3 The present invention is a circuit block diagram of a grid-type inverter under the grid-type inverter composite current synchronous control method provided in the present application.

[0019] Figure 4 The following are simulation waveform diagrams of active power P and reactive power Q output by a grid-type inverter using the grid-type inverter composite current synchronization control method provided in the present application and the traditional control method under strong power grid conditions.

[0020] Figure 5The voltage simulation waveform diagram of the grid-type inverter output under strong power grid conditions using the grid-type inverter composite current synchronization control method provided in the present application and the traditional control method respectively.

[0021] Figure 6 The current simulation waveform diagram of the grid-type inverter output under strong power grid conditions using the grid-type inverter composite current synchronization control method provided in the present application and the traditional control method respectively. DETAILED DESCRIPTION

[0022] In order to make the purpose and technical solution of the embodiment of the present application clearer, the technical solution of the embodiment of the present application will be clearly and completely described in conjunction with the drawings of the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, not all of the embodiments. Based on the described embodiment of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] See also Figure 1 , Figure 1 1 is a control block diagram of a grid-type inverter under a traditional control method. The grid-type inverter 1 includes: a three-phase inverter bridge 111, an LC filter 112, and a public power grid 113, which are connected in sequence. Among them, the three-phase inverter bridge 111 includes a DC power supply V dc , capacitor C dc1 , capacitor C dc2 , switch unit 1111; LC filter 112 includes three sets of filter inductors L f and filter capacitors C f ; The public grid 113 includes a three-phase voltage source v g and equivalent grid impedance Z g .

[0024] Further, Figure 1 The system also includes: an active-frequency synchronous controller 12, a reactive-voltage synchronous controller 13, a grid-type inverter controller 14 and an instantaneous power calculator 15. The instantaneous power calculator 15 is connected to the first end of the active-frequency synchronous controller 12 and the first end of the reactive-voltage synchronous controller 13, respectively, and the second end of the active-frequency synchronous controller 12 and the second end of the reactive-voltage synchronous controller 13 are connected to the grid-type inverter controller 14, respectively.

[0025] The grid-type inverter controller 14 includes: abc / dqCoordinate converter 141, voltage and current double closed loop controller 142 and SPWM controller 143; abc / dq The first end of the coordinate converter 141 is connected to the active power-frequency synchronization controller 12. abc / dq The second end of the coordinate transformer 141 is connected to the LC filter 112, the first end of the voltage-current dual closed-loop controller 142 is connected to the second end of the active-frequency synchronization controller 12 and the second end of the reactive-voltage synchronization controller 13, the second end of the voltage-current dual closed-loop controller 142 is connected to the first end of the SPWM controller 143, and the second end of the SPWM controller 143 is connected to the three-phase inverter bridge 111.

[0026] exist Figure 1 In the structure of the conventional control method, the instantaneous power calculator 15 is first inputted with dq Output voltage in coordinate system v o_n and grid current i g_n , get the active power P and reactive power Q , active power P The output voltage phase angle of the grid-type inverter is obtained by the active power-frequency synchronization controller 12 , reactive power Q The output voltage reference value of the grid-type inverter is obtained by the reactive-voltage synchronous controller 13 V ref Then the voltage and current double closed-loop controller 142 is used to track the command value, thereby playing the role of voltage support, and finally the SPWM controller 143 is used to modulate the output PWM wave. Among them, the output voltage v o_n and grid current i g_n Depend on abc / dq The coordinate converter 141 samples and obtains n express d, q .

[0027] See also Figure 2 and Figure 3 ,like Figure 3 As shown, Figure 1 The active power-frequency synchronization controller 12 in the Figure 3 The grid-connected current-frequency synchronous controller 32 in which the composite d Axis grid-connected current-frequency synchronization controller 321 and q Axis grid-connected current-frequency synchronization controller 322; Figure 1 The reactive power-voltage synchronous controller 13 in the Figure 3 In q Axis grid-connected current-amplitude synchronization controller 33; d Axis grid-connected current-frequency synchronization controller 321 and q The first end of the axis grid-connected current-frequency synchronization controller 322 is connected to abc / dq The first end of the coordinate converter 341 is connected to the first end of the voltage-current dual closed-loop controller 342. q The second terminal of the axis grid-connected current-frequency synchronization controller 322 is connected to q The first end of the axis grid-connected current-amplitude synchronization controller 33 is connected, q The second end of the axis grid-connected current-amplitude synchronous controller 33 is connected to the first end of the voltage-current dual closed-loop controller 342. Figure 1 Compared with the conventional grid-type control, the instantaneous power calculator 15 is omitted.

[0028] Please continue reading Figure 2 and Figure 3 The control method provided by the present invention comprises the following steps: Step S1, detecting the inductor current i L_x , and perform coordinate transformation to obtain dq Inductor current in coordinate system i L_n ; Detect grid current i g_x , and perform coordinate transformation to obtain dq Grid current in coordinate system i g_n ; Detect output voltage v o_x , and perform coordinate transformation to obtain dq Output voltage in coordinate system v o_n ; Among them, the subscript x express a , b , c , subscript n express d, q .

[0029] Step S2, in d In the axis grid-connected current-frequency synchronization controller 321, receiving d Axis grid current i g_d ,according to d Axis grid current reference value i gref_d and d Axis grid current i g_d , calculated Shaft angular frequency adjustment Δ ω d .

[0030] As an example, d Axis grid-connected current reference value i gref_d and d Axis grid current i g_d Make the difference, then multiply by the inertia link m d ω d / (s+ω d ) produce d Shaft angular frequency adjustment Δ ω d .in, m d for d Shaft grid-connected current-frequency droop coefficient, ω d is the turning angular frequency of the inertia link, s is the Laplace coefficient. Step S3, q In the axis grid-connected current-frequency synchronization controller 322, receiving q Axis grid current i g_q ,according to q Axis grid current reference value i gref_q and q Axis grid current i g_q , calculate q Shaft angular frequency adjustment Δ ω q .

[0031] As an example, q Axis grid-connected current reference value i gref_q and q Axis grid current i g_q Make a difference and then multiply it by the high-pass filter link m q s / ( s + ω c ) q Shaft angular frequency adjustment Δ ω q .in, m q for qShaft grid-connected current-frequency droop coefficient, ω c is the corner frequency of the high-pass filter.

[0032] Step S4, according to d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n , calculate the output voltage phase angle of the grid-type inverter θ .

[0033] As an example, d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n Add and pass the integration phase 1 / s Get the output voltage phase angle of the grid-connected inverter θ .

[0034] Step S5, q In the axis grid-connected current-amplitude synchronization controller 33, receiving q Axis grid current i g_q ,according to q Axis grid current reference value i gref_q , Grid-connected rated voltage amplitude V n and q Axis grid current i g_q , calculate the output voltage amplitude reference of the grid-type inverter V ref .

[0035] As an example, q Axis grid current reference value i gref_q and q Axis grid current i g_q Make a difference, multiply by the inertia link n q ω q / ( s + ω q ) generates a voltage variation ΔV, which is proportional to the grid-connected rated voltage amplitudeV n Add together to get the grid inverter output voltage amplitude reference V ref .in, n q for q Axis grid-connected current-voltage droop coefficient, ω q is the turning angular frequency of the inertia link.

[0036] Step S6: In the grid-type inverter controller 34, according to the grid-type inverter output voltage phase angle θ Reference to the output voltage amplitude of the grid-connected inverter V ref , use the voltage reference calculation formula (Formula I and Formula II) to calculate the output voltage reference value v oref_n ;include d Output voltage reference value in the axis direction v oref_d and q Output voltage reference value in the axis direction v oref_q . d Output voltage reference value in the axis direction v oref_d Calculation formula (Formula I) and q Output voltage reference value in the axis direction v oref_q The calculation formula (Formula II) is as follows: (Formula I) (Formula II).

[0037] Step S7, output voltage reference value v oref_n With output voltage v o_n The error is fed into the voltage controller G v , get the inductor current reference value i Lref_n ; Set the inductor current reference value i Lref_n and the inductor current i L_n The error is fed into the proportional-integral current controller G i , and get the modulated wave v m_n ; Modulate the wave v m_n Convert to the three-phase stationary coordinate system to get the modulation wave v m_x, PWM control signal is generated by sinusoidal pulse width modulation.

[0038] In one embodiment of the present application, the voltage controller G v It is a PI regulator.

[0039] In one embodiment of the present application, the current controller G i It is a proportional-integral controller.

[0040] As an example, see Figure 4 , Figure 5 and Figure 6 , under the grid condition (Lg = 0.01mH, Rg = 0.001Ω), the grid-type inverters using the traditional control method and the control method proposed in this application are simulated and compared by PLECS simulation software to verify the superiority of the grid-type inverter composite current synchronization control method provided in this application. At t = 8s, the control mode is switched from the grid-type inverter composite current synchronization control method provided in this application to the traditional control method, and the following is obtained: Figure 4 , Figure 5 and Figure 6 The simulation results comparison chart is shown. Figure 4 The following are simulation waveforms of active power P and reactive power Q output by the grid-type inverter using the grid-type inverter composite current synchronization control method provided by the present application and the traditional control method under strong power grid conditions. Figure 5 The voltage simulation waveform diagram of the grid-type inverter output under strong power grid conditions using the grid-type inverter composite current synchronization control method provided by the present application and the traditional control method respectively. Figure 6 The current simulation waveform diagram of the grid-type inverter output under strong power grid conditions using the grid-type inverter composite current synchronization control method provided by the present application and the traditional control method respectively. Figure 4 , Figure 5 and 6 It can be seen that when the composite current synchronous control method of the grid-type inverter provided in this application is adopted, the output power, voltage and current waveforms of the grid-type inverter are stable and smooth, while when switching to the traditional control method, the grid-type inverter cannot guarantee the stability of the system under a strong power grid.

[0041] In another embodiment of the present application, a device is also provided, comprising: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors execute a grid-type inverter composite current synchronization control method as described in any one of the above.

[0042] In another embodiment of the present application, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, a composite current synchronous control method of a grid-type inverter as described in any one of the above is implemented.

[0043] In summary, the grid-type inverter composite current synchronous control method, device and computer-readable storage medium provided by the present application symmetrically introduces in the synchronous control loop dq The axis grid-connected current component is subtracted from the reference value and outputs a dual angular frequency adjustment through the inertia and droop links, which is then compounded to generate a synchronous angular frequency adjustment , and then the output voltage phase angle of the grid-connected inverter required for synchronization is obtained through the integration link θ The composite current synchronous control method of the grid-type inverter provided in this application is used to utilize the system d Axis and q The axis grid current component realizes the synchronization of the grid-forming inverter and the grid voltage, omitting the instantaneous power calculation link in the traditional grid-forming inverter control, enabling the grid-forming inverter to operate reliably and stably, and effectively improving the robustness of the grid-forming inverter to grid impedance changes and the stability under strong grid conditions, thereby realizing plug-and-play in the grid.

[0044] Although the present application has been disclosed as above with the embodiments, it is not intended to limit the present application. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be determined by the scope of the attached patent application.

Claims

1. A composite current synchronous control method for a grid-connected inverter, characterized in that: The following steps are involved: Step S1, detecting the inductor current i L_x , and perform coordinate transformation to obtain dq Inductor current in coordinate system i L_n ; Detect grid current i g_x , and perform coordinate transformation to obtain dq Grid current in coordinate system i g_n ; Detect output voltage v o_x , and perform coordinate transformation to obtain dq Output voltage in coordinate system v o_n ; Among them, the subscript x express a , b , c , subscript n express d, q ; Step S2, according to d Axis grid current reference value i gref_d and d Axis grid current i g_d , calculate d Shaft angular frequency adjustment Δ ω d ; Step S3, according to q Axis grid current reference value i gref_q and q Axis grid current i g_q , calculate q Shaft angular frequency adjustment Δ ω q ; Step S4, according to d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n , calculate the output voltage phase angle of the grid-type inverter θ ; Step S5, according to q Axis grid current reference value i gref_q , Grid-connected rated voltage amplitude V n and q Axis grid current i g_q , calculate the output voltage amplitude reference of the grid-type inverter V ref ; Step S6: According to the grid-type inverter output voltage phase angle θ Reference to the output voltage amplitude of the grid-connected inverter V ref , use the voltage reference calculation formula to get the output voltage reference value v oref_n ; The output voltage reference value v oref_n include: d Output voltage reference value in the axis direction v oref_d and q Output voltage reference value in the axis direction v oref_q ; Step S7, output voltage reference value v oref_n With output voltage v o_n The error is fed into the voltage controller G v , get the inductor current reference value i Lref_n ; Set the inductor current reference value i Lref_n and the inductor current i L_n The error is fed into the current controller G i , and get the modulated wave v m_n ; Modulate the wave v m_n Converted to the three-phase stationary coordinate system, we get v m_x , PWM control signal is generated by sinusoidal pulse width modulation.

2. The grid-type inverter composite current synchronous control method according to claim 1, characterized in that: The step S2 comprises: d Axis grid-connected current reference value i gref_d and d Axis grid current i g_d Make the difference, then multiply by the inertia link m d ω d / ( s + ω d )produce d Shaft angular frequency adjustment Δ ω d ; in, m d for d Shaft grid-connected current-frequency droop coefficient, ω d is the turning angular frequency of the inertia link, s is the Laplace coefficient.

3. The grid-type inverter composite current synchronous control method according to claim 2, characterized in that: In step S3, q Axis grid-connected current reference value i gref_q and q Axis grid current i g_q Make a difference and then multiply it by the high-pass filter link m q s / ( s + ω c ) q Shaft angular frequency adjustment Δ ω q ; in, m q for q Shaft grid-connected current-frequency droop coefficient, ω c is the corner frequency of the high-pass filter.

4. The grid-type inverter composite current synchronous control method according to claim 3, characterized in that: In step S4, d Shaft angular frequency adjustment Δ ω d , q Shaft angular frequency adjustment Δ ω q and angular frequency ratings ω n Add and pass the integration phase 1 / s Get the phase angle of the grid inverter output voltage θ .

5. The grid-type inverter composite current synchronous control method according to claim 4, characterized in that: In step S5, q Axis grid current reference value i gref_q and q Axis grid current i g_q Make a difference, multiply by the inertia link n q ω q / ( s + ω q ) generates a voltage variation ΔV, which is proportional to the grid-connected rated voltage amplitude V n Add together to get the amplitude reference of the grid inverter output voltage V ref ,in, n q for q Axis grid-connected current-voltage droop coefficient, ω q is the turning angular frequency of the inertia link.

6. The grid-type inverter composite current synchronous control method according to claim 5, characterized in that: In step S6, the voltage reference calculation formula is: ， 。 7. The grid-type inverter composite current synchronous control method according to claim 1, characterized in that: The voltage controller G v It is a PI regulator.

8. The grid-connected inverter composite current synchronous control method according to claim 1, characterized in that: The current controller G i It is a proportional-integral controller.

9. A device, characterized in that: The device includes: one or more processors; a memory for storing one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors execute a grid-type inverter composite current synchronization control method as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, a grid-type inverter composite current synchronization control method as described in any one of claims 1 to 8 is implemented.

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