CN117254527B

CN117254527B - Control parameter optimization method and device for grid-structured converter

Info

Publication number: CN117254527B
Application number: CN202311532505.8A
Authority: CN
Inventors: 王伟胜; 雷雨; 郭梓暄; 肖云涛; 李光辉; 何国庆; 高丽萍
Original assignee: China Electric Power Research Institute Co Ltd CEPRI
Current assignee: China Electric Power Research Institute Co Ltd CEPRI
Priority date: 2023-11-17
Filing date: 2023-11-17
Publication date: 2024-03-15
Anticipated expiration: 2043-11-17
Also published as: CN117254527A

Abstract

The invention relates to the technical field of new energy grid-connected control, and particularly provides a method and a device for optimizing control parameters of a grid-formed converter.

Description

Control parameter optimization method and device for grid-structured converter

Technical Field

The invention relates to the technical field of new energy grid-connected control, in particular to a method and a device for optimizing control parameters of a grid-structured converter.

Background

Grid-connected control is the key of network source coordination in the process of new energy power generation development and utilization. New energy grid-connected control is divided into grid-following (GFL) and grid-forming (GFM) groups, which are proposed by university of Weisconsin, erickson M J, et al in 2011. The grid-connected control is performed in a grid-connected control mode, namely, the new energy power generation follows the voltage and the frequency of the power grid, and the grid-formed grid-connected control is performed in a grid-connected control mode, namely, the new energy power generation participates in the construction of the voltage and the frequency of the power grid. The network control is originally derived from an uninterruptible power supply. In 1991, the university of Weisconsin Chandorkar M C et al proposed a droop control method, which by simulating the droop operation mode of a synchronous generator, realized that UPS multiple DC/AC units were connected in parallel. In 1997, the scholars of Tuladhar A, the university of british Columbia, added a current loop into the droop control voltage loop, so that the droop control has the over-current and harmonic current inhibition capability, and the power outer loop and the voltage-current inner loop become typical structures of the droop control.

With the continuous improvement of the new energy power generation duty ratio, the synchronous moment of inertia in a large power grid is reduced, and the frequency stability risk is increased. In 2007, the virtual synchronous machine (virtual synchronous generator, VSG) concept was proposed by scholars, beck H P et al, university of lakepital industry, germany, european VSYNC working group. In 2008, students such as Gao F of Canada Toronto university and the like add a moment of inertia and damping winding simulation link to an active power loop based on sagging control, so that VSG based on grid-connected control is realized. In 2009, students such as Zhong Q at university of lafuburg, uk, proposed a static synchronous generator, improving the reactive-voltage excitation control link of VSG. Compared with droop control, the VSG can respond to not only the change of the frequency and the voltage of the power grid, but also the change rate of the frequency of the power grid. In 2019, related researches further show that the network-structured VSG access system can also improve the stability of a weak power grid and reduce the risk of high-proportion new energy power generation secondary/super-synchronous oscillation. The grid-structured VSG becomes an important device for supporting high-proportion new energy to stably operate under a weak electric network.

With the continuous and intensive research, the stability problem of the network-structured converter is gradually revealed. Literature [ Li Peng, yang Shiwang, yan Ziheng ] microgrid voltage stabilizing decoupling droop control method based on relative gain matrix [ J ]. Chinese motor engineering journal 2015, 35 (05): 1041-1050] studies have shown that the resistive component of the low voltage line results in active and reactive control coupling, reducing the stability margin of the grid-tied converter. Document [ LI M, ZHANG X, YANG Y. The grid impedance adaptation dual mode control strategy in weak grid [ C ]. 2018 International Power Electronics Conference (IPEC-Niigata 2018-ECCE Asia), 2015:2973-2979 states that even though there is no resistive component in the line, subsynchronous oscillations of the grid-formed converter may occur in a strong electric network with a low inductive impedance. Literature [ by-strength, duwenjuan, wang Haifeng. Influence of multiple virtual synchronous generator access on electromechanical oscillation mode of electric power system [ J ]. Chinese motor engineering journal, 2018, 38 (19): 5615-5624+5919] adopts a damping torque method, researches on the influence mechanism of network-structured converter access on the electromechanical oscillation mode of the power system show that: when the open-loop mode of the access network type converter is close to other open-loop modes of the converter, the stability margin of the system under the electromechanical frequency band is reduced.

Aiming at the stability improvement of the grid-structured converter, partial researches are carried out: document [ Qin Benshuang, xu Yonghai, yuan Chang, et al, P/ω admittance modeling and power frequency oscillation analysis of multiple VSG grid-connected systems [ J ]. Chinese motor engineering journal, 2020, 40 (09): 2932-2942 states that increasing the grid impedance, decreasing the number of grid-connected converters, helps to reduce the oscillation amplitude, and has practical difficulties in engineering due to the need to modify the system hardware configuration. In contrast, by improving control for impedance remodeling, it is a more efficient way to improve the stability of a grid-formed converter under a strong grid.

At present, the method for remolding the impedance of the grid-structured converter based on the stability margin improvement under the strong power grid has the following problems: 1) The method aims at stable operation under a strong power grid, and an improved impedance remodelling method based on power loop control comprises the steps of optimizing droop coefficients, damping coefficients, inertia coefficients, cut-off frequencies of low-pass filters and the like, so that the power control bandwidth under the weak power grid is reduced, and the following rapidity of power regulation is affected; 2) The method aims at stable operation under a strong power grid, and an improved impedance remodelling method based on voltage and current inner loop control comprises virtual admittance, virtual impedance and the like, which can lead to reduction of voltage and current control bandwidth under a weak power grid and influence the disturbance resistance performance of voltage and current control. The stability margin improvement under the strong power grid and the dynamic response of power, voltage and current under the weak power grid are contradictory, and the impedance remodeling of the grid-structured converter becomes a key problem.

Currently, there are patents on the design of control parameters for a grid-built converter, such as:

chinese patent application CN 113962181A, a method for optimizing control parameters of a grid-structured voltage source converter, and CN 116404691A, a method for optimizing control parameters of a grid-structured new energy power generation system, and an optimizing device;

the technical scheme is a typical network-structured converter control design method. The basic principle idea is as follows: firstly, determining the hardware and control structure of a network-structured converter, and drawing a small signal transfer function structure diagram; then, according to the small signal transfer function structure diagram, the transfer function of the voltage ring and the current ring is obtained; and finally, drawing a frequency domain graph, and solving control parameters of the voltage ring and the current ring according to the relation between the parameter change and the frequency domain index by utilizing the graphs such as a Bode graph, a zero pole graph, a D-segmentation graph and the like.

However, the grid is the grid-connected object of the grid-tied converter, and grid strength variations will significantly affect the grid-tied converter voltage loop, current loop control bandwidth and phase margin. In the technical scheme, the small signal transfer function structure diagram is from hardware to the filter capacitor C of the converter _f That is, the transfer functions of the voltage ring and the current ring do not include the power grid intensity information, and essentially the influence of the power grid intensity change on the dynamic response of the grid-structured converter is not considered. According to the technical scheme, the control parameters of the voltage ring and the current ring are designed, so that the change of the power grid strength, particularly the stability when the power grid strength is high, and the control bandwidth and the dynamic performance of the voltage ring and the current ring of the grid-built converter under the weak power grid with the low power grid strength cannot be ensured.

In summary, the parameter design of the above technical solution does not consider the problem of stable operation under the strong power grid of the grid-structured converter. According to the first prior art, the control parameters of the voltage ring and the current ring are designed, so that the change of the power grid strength cannot be ensured, and particularly, the stable operation of the grid-built converter under the strong current grid with higher power grid strength cannot be ensured.

Chinese patent application CN 110021959A, the grid-connected inverter dual-mode control method based on short circuit ratio under weak current network, which is described: the current source (the follow-up network converter) has stronger stability under a strong power grid, and has insufficient stability margin under a weak power grid, so that oscillation is easy to occur; the voltage source (grid-structured converter) has stronger stability under a weak electric network, and has insufficient stability margin under a strong electric network, so that oscillation is easy to occur. Therefore, the second prior art proposes a dual-mode control method of the grid-connected inverter based on the short-circuit ratio, wherein the grid-connected inverter is switched to voltage source control under a weak power grid and is switched to current source control under a strong power grid by detecting the equivalent short-circuit ratio of the system. The method needs to detect the power grid strength and switch the control modes.

According to the technical scheme, the grid-connected converter stably operates under the condition of power grid strength change by detecting the equivalent short circuit ratio of the system and switching the grid-formed/grid-following control modes. For a power grid, a large number of grid-connected converter control modes are frequently switched, so that the characteristics of the power grid are changed in a complex manner, and the scheduling optimization operation and management are not facilitated. In addition, under the condition that a large number of grid-connected converters of the new energy base are interconnected, the equivalent short circuit of the system is more complex than the detection algorithm, and accurate detection is difficult to realize.

Chinese patent application CN 112271737A discloses a virtual synchronous machine strong power grid stability control method based on inductive current differential feedback. According to the method, the output power oscillation under the strong power grid of the virtual synchronous machine is restrained by virtual synchronous machine control and inductance current differential feedback control on the premise that actual inductance is not added, filter cost is not increased, and a current sensor on the grid side is not added, so that stable operation under the strong power grid of the virtual synchronous machine is realized.

According to the technical scheme, stable operation of the virtual synchronous machine under the strong power grid is realized through impedance remodelling control based on inductance current differential feedback control. However, inductor current differential feedback is equivalent to increasing the virtual inductance. Although the virtual inductor can improve the stability margin under the strong current network, the dynamic power response performance of the virtual synchronous machine under the weak current network can be reduced, and the stability margin improvement under the strong current network and the dynamic performance comprehensive optimization under the weak current network are difficult to realize.

Disclosure of Invention

In order to overcome the defects, the invention provides a method and a device for optimizing control parameters of a grid-structured converter.

In a first aspect, a method for optimizing control parameters of a grid-connected converter is provided, where the method includes:

solving the current loop control parameter model under the current loop dynamic response constraint condition to obtain the current loop control parameter of the grid-built converter, and solving the voltage loop control parameter model under the voltage loop dynamic response constraint condition to obtain the voltage loop control parameter of the grid-built converter;

solving an active loop control parameter model under the dynamic response constraint condition of an active loop to obtain an active loop control parameter of a first grid-structured converter, solving an impedance analysis model of an alternating current port of the grid-structured converter under the strong constraint condition of the grid-structured converter to obtain an active loop control parameter of a second grid-structured converter, and taking the intersection of the active loop control parameter of the first grid-structured converter and the active loop control parameter of the second grid-structured converter as the active loop control parameter of the grid-structured converter;

and taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme.

Preferably, the current loop dynamic response constraint condition comprises that the equivalent inductance of the power grid is larger than a preset equivalent inductance demarcation value of the strong and weak power grid, and the bandwidth and the phase margin of the current loop are respectively equal to the corresponding given values;

The voltage loop dynamic response constraint condition comprises: the equivalent inductance of the power grid is larger than the preset equivalent inductance demarcation value of the strong and weak power grid, and the bandwidth and the phase margin of the voltage ring are respectively equal to the corresponding given values.

Preferably, the dynamic response constraint condition of the active ring includes: the equivalent inductance of the power grid is larger than the preset equivalent inductance demarcation value of the strong and weak power grid, and the bandwidth of the active zone is equal to the corresponding given value;

the stability constraint conditions under the strong power grid of the grid-structured converter comprise: the equivalent inductance of the power grid is smaller than the preset boundary value of the equivalent inductance of the strong and weak power grid, and the stability margin of the impedance ratio of the grid-structured converter and the power grid system is equal to the corresponding given value.

Preferably, the current loop control parameters of the grid-connected converter include: current loop ratio coefficient and integral coefficient; the voltage loop control parameters of the grid-connected converter comprise: voltage loop ratio coefficient and integral coefficient; the active loop control parameters of the network-structured converter comprise: active sag coefficient and inertia coefficient.

Preferably, the current loop control parameter model is as follows:

in the above, G _i (s) is the current loop open loop transfer function, s is the first laplace operator, s=j2pi×f _p ，f _p For the disturbance frequency, j is the imaginary unit, For a given value corresponding to the current loop bandwidth, +.>For a given value corresponding to the phase margin of the current loop, +.>Is the circumference ratio.

Further, the current loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row and column element in the open loop transfer function matrix of the current loop, < >>For the first row and the second column elements in the current loop open-loop transfer function matrix, < >>For the second row and first column elements in the current loop open-loop transfer function matrix,a second row and a second column of elements in the open loop transfer function matrix for the current loop, wherein:

in the above formula, A is a first coefficient matrix, T _pwm For a grid-tied converter PWM period,is a filter inductance matrix, B is a second coefficient matrix, C is a third coefficient matrix, H _i (s) is a current loop controller transfer function.

Further, the first coefficient matrix, the second coefficient matrix and the third coefficient matrix are as follows:

the PWM period and the filter inductance matrix of the grid-structured converter are as follows:

in the above, L _f R is the filter inductance of the network-structured converter _d Is the equivalent resistance of the power grid, C _f In order to construct the filter capacitor of the network type converter,for the rated angular frequency of the power grid, L _g Is the equivalent inductance of the power grid, e is a natural constant, T _s For sampling period, K of network-structured converter _pwm Is a pulse width modulation gain.

Further, the voltage loop control parameter model is as follows:

in the above, G _v (s) is the open loop transfer function of the voltage loop,for a given value corresponding to the voltage loop bandwidth, +.>Is a given value corresponding to the voltage loop phase margin.

Further, the voltage loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row, column element in the open-loop transfer function matrix of the voltage loop, < >>For the first row, the second column element in the voltage loop open-loop transfer function matrix, < >>For the second row and first column elements in the voltage loop open-loop transfer function matrix,for a second row and a second column of elements in the voltage loop open-loop transfer function matrix, wherein:

in the above, H _v (s) is a transfer function of the voltage loop controller, and I is a 2 x 2 order identity matrix.

Further, the active loop control parameter model is as follows:

in the above, G _p (s) is an active ring open loop transfer function,is a given value corresponding to the active zone bandwidth.

Further, the active ring open loop transfer function is as follows:

in the above, D _p For the active sag factor, J is the inertia factor, V _n Is the phase voltage amplitude rating.

Further, the impedance analysis model of the ac port of the grid-structured converter is as follows:

In the above, Y _GFM For the admittance of the ac port of the grid-built converter,for the fourth matrix>For the fifth matrix, H _p (s) is a transfer function of a power synchronization link, P _v As a voltage active coefficient matrix, P _i Is a current active coefficient matrix, < >>For a sixth matrix, Y _Cf For filter capacitance matrix, Z _GFM Is the AC port impedance of the network-structured converter.

Further, the current active coefficient matrix and the voltage active coefficient matrix are as follows:

in the above, F(s) ₁ ) For the transfer function of the sampler, V ₁ For a the steady-state fundamental frequency component of the alternating voltage,for the steady-state fundamental frequency component conjugation of a-phase alternating voltage I ₁ For a alternating current steady-state fundamental frequency component, +.>For the steady-state fundamental frequency component conjugation of a alternating current, s ₁ For the second Laplace operator, +.>，f _p For the disturbance frequency f ₁ For rated frequency +.>,,/>,/>,/>For a phase of fundamental frequency component of alternating voltage, +.>A phase of the alternating current fundamental frequency component;

the fourth, fifth and sixth matrices are as follows:

in the above, K _m For PWM gain, V _dc Is the voltage of a direct current bus, T _s As a time constant matrix for delay, F _v As a matrix of voltage coefficients, F _i As a matrix of current coefficients, F _θ Is a synchronous angle coefficient matrix;

the voltage coefficient matrix, the current coefficient matrix and the synchronous angle coefficient matrix are as follows:

In the above, M _d For d-axis modulated signal steady state matrix, M _q For steady-state matrix of q-axis modulation signal, T _sin Is a sine coefficient matrix, T _cos Is a matrix of cosine coefficients which are,E _dθ for the d-axis synchronization of the angular coefficient matrix of the modulated signal,E _qθ for the q-axis synchronization of the angular coefficient matrix of the modulated signal,E _dv for the d-axis modulated signal voltage coefficient matrix,E _qv for the q-axis modulated signal voltage coefficient matrix,E _di the signal current coefficient matrix is modulated for the d-axis,E _qi modulating a signal current coefficient matrix for a q-axis;

the d-axis synchronous angle coefficient matrix, the q-axis synchronous angle coefficient matrix, the d-axis modulated signal voltage coefficient matrix, the q-axis modulated signal voltage coefficient matrix, the d-axis modulated signal current coefficient matrix and the q-axis modulated signal current coefficient matrix of the modulated signals are as follows:

in the above, H _qd (s) is a sagging control transfer function, H _v (s ₁ ) For the transfer function of the voltage controller, H _i (s ₁ ) Is transmitted to a current controllerThe transfer function is used to transfer the data to the memory,Q _i is a matrix of reactive current coefficients,Q _v is a matrix of reactive voltage coefficients, which is a matrix of reactive voltage coefficients,D _di is a matrix of d-axis current coefficients,D _qi for the q-axis current coefficient matrix,B _dv is a matrix of d-axis voltage coefficients,B _qv for the q-axis voltage coefficient matrix,B _dθ is a d-axis voltage-synchronous angle coefficient matrix,B _qθ for the q-axis voltage-synchronization angle coefficient matrix,D _dθ for the d-axis current-synchronization angle coefficient matrix, D _qθ For q-axis current-synchronous angular coefficient matrix, K _d Is a current loop decoupling coefficient;

the d-axis voltage coefficient matrix, the q-axis voltage coefficient matrix, the d-axis voltage-synchronization angle coefficient matrix, the q-axis voltage-synchronization angle coefficient matrix, the d-axis current coefficient matrix, the q-axis current coefficient matrix, the d-axis current-synchronization angle coefficient matrix, and the q-axis current-synchronization angle coefficient matrix are as follows:

in the above-mentioned method, the step of,is the synchronous angular steady state phase.

Further, the stability constraint condition under the strong power grid of the grid-structured converter includes:

in the above, Z _g For the impedance of the electric network, Z _GFM For the ac port impedance of the grid-formed converter,for a given value corresponding to the active loop phase margin, < >>Is of circumference rate>And j is an imaginary unit for a given value corresponding to the active zone bandwidth.

In a second aspect, there is provided a grid-structured converter control parameter optimization apparatus, the grid-structured converter control parameter optimization apparatus including:

the first analysis module is used for solving the current loop control parameter model under the current loop dynamic response constraint condition to obtain the current loop control parameter of the grid-built converter, and solving the voltage loop control parameter model under the voltage loop dynamic response constraint condition to obtain the voltage loop control parameter of the grid-built converter;

The second analysis module is used for solving the active loop control parameter model under the dynamic response constraint condition of the active loop to obtain the active loop control parameter of the first grid-structured converter, solving the alternating current port impedance analysis model of the grid-structured converter under the stability constraint condition of the strong grid of the grid-structured converter to obtain the active loop control parameter of the second grid-structured converter, and taking the intersection of the active loop control parameter of the first grid-structured converter and the active loop control parameter of the second grid-structured converter as the active loop control parameter of the grid-structured converter;

and the control parameter optimization module is used for taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme.

In a third aspect, there is provided a computer device comprising: one or more processors;

the processor is used for storing one or more programs;

and when the one or more programs are executed by the one or more processors, the network-structured converter control parameter optimization method is realized.

In a fourth aspect, a computer readable storage medium is provided, on which a computer program is stored, the computer program, when executed, implementing the method for optimizing control parameters of a grid-built converter.

The technical scheme provided by the invention has at least one or more of the following beneficial effects:

the invention relates to the technical field of new energy grid-connected control, and particularly provides a method and a device for optimizing control parameters of a grid-structured converter, wherein the method comprises the following steps: solving the current loop control parameter model under the current loop dynamic response constraint condition to obtain the current loop control parameter of the grid-built converter, and solving the voltage loop control parameter model under the voltage loop dynamic response constraint condition to obtain the voltage loop control parameter of the grid-built converter; solving an active loop control parameter model under the dynamic response constraint condition of an active loop to obtain an active loop control parameter of a first grid-structured converter, solving an impedance analysis model of an alternating current port of the grid-structured converter under the strong constraint condition of the grid-structured converter to obtain an active loop control parameter of a second grid-structured converter, and taking the intersection of the active loop control parameter of the first grid-structured converter and the active loop control parameter of the second grid-structured converter as the active loop control parameter of the grid-structured converter; and taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme. According to the technical scheme provided by the invention, under the given constraint condition, the feasible domains of the control parameters of the current loop, the voltage loop and the power loop are obtained by gradually solving the frequency domain equation of the current loop, the voltage loop and the power loop, so that the stable operation under the strong power grid of the grid-structured converter is finally realized, and the dynamic response performance under the weak power grid is considered, namely: the stability margin meets the requirements under a given strong power grid, and the control bandwidths of the current loop, the voltage loop and the power loop meet the requirements under a given weak power grid.

Drawings

FIG. 1 is a flow chart of main steps of a method for optimizing control parameters of a grid-connected converter according to an embodiment of the present invention;

fig. 2 is a hardware and control structure diagram of a grid-structured converter according to an embodiment of the present invention;

FIG. 3 is a diagram of a power loop control architecture for a grid-tied converter in accordance with an embodiment of the present invention;

FIG. 4 is a diagram of a control structure of a voltage loop and a current loop of a grid-tied converter according to an embodiment of the present invention;

fig. 5 is a graph comparing the results before and after impedance remodeling of a networked converter according to an embodiment of the present invention.

Detailed Description

The following describes the embodiments of the present invention in further detail with reference to the drawings.

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

As disclosed in the background art, grid-connected control is a key of grid source coordination in the process of new energy power generation development and utilization. New energy grid-connected control is divided into grid-following (GFL) and grid-forming (GFM) groups, which are proposed by university of Weisconsin, erickson M J, et al in 2011. The grid-connected control is performed in a grid-connected control mode, namely, the new energy power generation follows the voltage and the frequency of the power grid, and the grid-formed grid-connected control is performed in a grid-connected control mode, namely, the new energy power generation participates in the construction of the voltage and the frequency of the power grid. The network control is originally derived from an uninterruptible power supply. In 1991, the university of Weisconsin Chandorkar M C et al proposed a droop control method, which by simulating the droop operation mode of a synchronous generator, realized that UPS multiple DC/AC units were connected in parallel. In 1997, the scholars of Tuladhar A, the university of british Columbia, added a current loop into the droop control voltage loop, so that the droop control has the over-current and harmonic current inhibition capability, and the power outer loop and the voltage-current inner loop become typical structures of the droop control.

In order to improve the problems, the invention relates to the technical field of new energy grid-connected control, and particularly provides a method and a device for optimizing control parameters of a grid-structured converter, wherein the method comprises the following steps: solving the current loop control parameter model under the current loop dynamic response constraint condition to obtain the current loop control parameter of the grid-built converter, and solving the voltage loop control parameter model under the voltage loop dynamic response constraint condition to obtain the voltage loop control parameter of the grid-built converter; solving an active loop control parameter model under the dynamic response constraint condition of an active loop to obtain an active loop control parameter of a first grid-structured converter, solving an impedance analysis model of an alternating current port of the grid-structured converter under the strong constraint condition of the grid-structured converter to obtain an active loop control parameter of a second grid-structured converter, and taking the intersection of the active loop control parameter of the first grid-structured converter and the active loop control parameter of the second grid-structured converter as the active loop control parameter of the grid-structured converter; and taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme. According to the technical scheme provided by the invention, under the given constraint condition, the feasible domains of the control parameters of the current loop, the voltage loop and the power loop are obtained by gradually solving the frequency domain equation of the current loop, the voltage loop and the power loop, so that the stable operation under the strong power grid of the grid-structured converter is finally realized, and the dynamic response performance under the weak power grid is considered, namely: the stability margin meets the requirements under a given strong power grid, and the control bandwidths of the current loop, the voltage loop and the power loop meet the requirements under a given weak power grid.

The above-described scheme is explained in detail below.

Example 1

Referring to fig. 1, fig. 1 is a schematic flow chart of main steps of a method for optimizing control parameters of a grid-formation type converter according to an embodiment of the present invention. As shown in fig. 1, the method for optimizing the control parameters of the grid-connected converter in the embodiment of the invention mainly comprises the following steps:

step S101: solving the current loop control parameter model under the current loop dynamic response constraint condition to obtain the current loop control parameter of the grid-built converter, and solving the voltage loop control parameter model under the voltage loop dynamic response constraint condition to obtain the voltage loop control parameter of the grid-built converter;

step S102: solving an active loop control parameter model under the dynamic response constraint condition of an active loop to obtain an active loop control parameter of a first grid-structured converter, solving an impedance analysis model of an alternating current port of the grid-structured converter under the strong constraint condition of the grid-structured converter to obtain an active loop control parameter of a second grid-structured converter, and taking the intersection of the active loop control parameter of the first grid-structured converter and the active loop control parameter of the second grid-structured converter as the active loop control parameter of the grid-structured converter;

Step S103: and taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme.

In one embodiment, the hardware and control structure of the grid-connected converter applying the grid-connected converter control parameter optimization method are shown in fig. 2, and the grid-connected converter hardware and control structure comprises a direct current power supply 01, a three-phase converter bridge 02, a three-phase filter inductor 03, a three-phase filter capacitor 04, a three-phase equivalent power grid inductor 05 and a three-phase power grid 06; the network-structured converter software part comprises a power loop controller 07, a Park conversion unit 08, a voltage loop controller 09, a current loop controller 10, an inverse Park conversion unit 11 and a PWM unit 12; in the figure, L _g The equivalent inductance value of the power grid; l (L) _f Is the inductance value of the filtering inductor; c (C) _f The capacitance value of the filter capacitor; v _a 、v _b 、v _c The three-phase voltages are grid-connected points respectively; i.e _a 、i _b 、i _c Three-phase output currents respectively; u (u) _ga ，u _gb ，u _gc Is the three-phase grid voltage; u (U) _dc Is a direct current voltage; m is m _d 、m _q Respectively dq axis modulation signals; m is m _a 、m _b 、m _c Respectively three-phase modulation signals; v _d 、v _q Respectively the dq axis voltages of the grid connection points; v (V) _ref Is an output voltage reference value; v _dref 、v _qref Is the dq axis voltage reference value; i.e _dref 、i _qref Outputting a current reference value for the dq axis; i.e _d 、i _q Respectively dq axesOutputting a current; h _PQ (s) is a power loop controller transfer function; h _v (s) is a voltage loop controller transfer function; h _i (s) is the transfer function of the current loop controller, e _a 、e _b 、e _c A, b, c three-phase modulation voltage, θ _s Control phase angle, v, for grid-formed converters _abc Is three-phase AC voltage, i _abc Is three-phase alternating current;

the invention sequentially carries out parameter design on the current loop controller 10, the voltage loop controller 09 and the power loop controller 07, realizes stable operation of the grid-structured converter under the strong power grid, and gives consideration to dynamic response performance under the weak power grid;

the power loop control structure of a given network-structured converter is shown in fig. 3, in which ω _ref For the nominal frequency of the system, θ _s The phase angle is controlled for the grid-structured converter; p (P) _ref The active power instruction is adopted, and P is electromagnetic active power; j is the inertia coefficient, D _p Is the active sag factor; n is the reactive sag coefficient, U _pcc For output voltage s is the first Lapladuo operator, Q _ref For reactive power instruction, U _ref The voltage command is given, and Q is electromagnetic reactive power;

the control structure of the voltage ring and the current ring of the grid-built type converter is shown in figure 4, wherein K is as follows _vp 、K _vi The voltage ring proportion and integration coefficient, K _ip 、K _ii The current loop proportion and integral coefficients are respectively; k (K) _d Is a current loop decoupling coefficient;

in this embodiment, the current loop dynamic response constraint condition includes that the power grid equivalent inductance is greater than a preset strong and weak power grid equivalent inductance demarcation value, and the current loop bandwidth and the phase margin are respectively equal to their respective corresponding given values;

In this embodiment, the current loop control parameters of the grid-configured converter include: current loop ratio coefficient and integral coefficient; the voltage loop control parameters of the grid-connected converter comprise: voltage loop ratio coefficient and integral coefficient; the active loop control parameters of the network-structured converter comprise: active sag coefficient and inertia coefficient.

In this embodiment, the current loop control parameter model is as follows:

in the above, G _i (s) is the current loop open loop transfer function, s is the first laplace operator, s=j2pi×f _p ，f _p For the disturbance frequency, j is the imaginary unit,for a given value corresponding to the current loop bandwidth, +.>For a given value corresponding to the phase margin of the current loop, +.>Is the circumference ratio.

In one embodiment, the current loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row in the current loop open loop transfer function matrixColumn element (s)/(S)>For the first row and the second column elements in the current loop open-loop transfer function matrix, < >>For the second row and first column elements in the current loop open-loop transfer function matrix,a second row and a second column of elements in the open loop transfer function matrix for the current loop, wherein:

In one embodiment, the first coefficient matrix, the second coefficient matrix, and the third coefficient matrix are as follows:

in the above, L _f R is the filter inductance of the network-structured converter _d Is the equivalent resistance of the power grid, C _f For constructing net type current transformer filterThe wave-capacitor is used to control the voltage across the capacitor,for the rated angular frequency of the power grid, L _g Is the equivalent inductance of the power grid, e is a natural constant, T _s For sampling period, K of network-structured converter _pwm Is a pulse width modulation gain.

In one embodiment, the voltage loop control parameter model is as follows:

In one embodiment, the voltage loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row, column element in the open-loop transfer function matrix of the voltage loop, < >>For the first row, the second column element in the voltage loop open-loop transfer function matrix, < >>For the second row and first column elements in the voltage loop open-loop transfer function matrix,for the second row and the second column elements in the voltage loop open-loop transfer function matrixWherein:

/>

In one embodiment, the active loop control parameter model is as follows:

In one embodiment, the active ring open loop transfer function is as follows:

In one embodiment, the mesh converter ac port impedance analysis model is as follows:

In one embodiment, the current and voltage active coefficient matrices are as follows:

the fourth, fifth and sixth matrices are as follows:

in the above, H _qd (s) is a sagging control transfer function, H _v (s ₁ ) For the transfer function of the voltage controller, H _i (s ₁ ) As a function of the transfer of the current controller,Q _i is a matrix of reactive current coefficients,Q _v is a matrix of reactive voltage coefficients, which is a matrix of reactive voltage coefficients,D _di is a matrix of d-axis current coefficients,D _qi for the q-axis current coefficient matrix,B _dv is a matrix of d-axis voltage coefficients, B _qv For the q-axis voltage coefficient matrix,B _dθ is a d-axis voltage-synchronous angle coefficient matrix,B _qθ for the q-axis voltage-synchronization angle coefficient matrix,D _dθ for the d-axis current-synchronization angle coefficient matrix,D _qθ for q-axis current-synchronous angular coefficient matrix, K _d Is a current loop decoupling coefficient;

In one embodiment, the stability constraint condition under the strong grid of the grid-structured converter includes:

The contradictory constraint between the stability margin improvement under the strong power grid and the dynamic response under the weak power grid is a key problem for improving the impedance remodelling control of the grid-structured converter. According to the method for optimizing the control parameters of the grid-structured converter, under the requirements of given power grid strength, stability margin, control bandwidth and the like, the feasible fields of the control parameters of the current loop, the voltage loop and the power loop are obtained by gradually solving the frequency domain equations of the current loop, the voltage loop and the power loop, and finally, the stable operation under the strong power grid of the grid-structured converter is realized, and the dynamic response performance under the weak power grid is considered, namely: the stability margin meets the requirements under a given strong power grid, and the control bandwidths of the current loop, the voltage loop and the power loop meet the requirements under a given weak power grid.

Taking a certain 1.5MW grid-connected transformer as an example, the implementation and results of the present invention will be described. The topology of the grid-connected converter is shown in fig. 1, and rated parameters and main circuit parameters of the grid-connected converter are shown in table 1.

TABLE 1

Parameters (parameters)	Numerical value
		Rated power	1.5 MW
Rated voltage	690 V
		Rated frequency	50 Hz
DC bus rated voltage	1050 V
		AC filter inductor	0.11 mH
AC filter capacitor	0.0005 F
		DC bus capacitor	12960×10 ^-6 F
Switching frequency	4500 Hz

The method for optimizing the control parameters of the grid-structured converter considering the dynamic response and the stable operation constraint is adopted to obtain the result pairs such as shown in figure 5 before and after the impedance remodeling of the grid-structured converter. Wherein, the solid line is the positive sequence impedance curve of the network-structured converter before impedance remodeling, and the dash-dot line is the positive sequence impedance curve of the network-structured converter after impedance remodeling. The method can be used for indicating that the impedance phase before remodeling has capacitive negative damping between 40 and 50Hz, and the oscillation risk under a strong power grid is high. And after the remolding, the capacitive negative damping of the impedance phase in the frequency range of 40-50 Hz is eliminated, and the grid-structured converter does not have the risks of oscillation and instability under a strong power grid.

Example 2

Based on the same inventive concept, the invention also provides a control parameter optimizing device of the grid-structured converter, which comprises:

Preferably, the current loop control parameter model is as follows:

Further, the current loop open loop transfer function is as follows:

/>

Further, the voltage loop control parameter model is as follows:

Further, the voltage loop open loop transfer function is as follows:

Further, the active loop control parameter model is as follows:

Further, the active ring open loop transfer function is as follows:

In the above, Y _GFM Is of the structureThe ac port admittance of the net type converter,for the fourth matrix>For the fifth matrix, H _p (s) is a transfer function of a power synchronization link, P _v As a voltage active coefficient matrix, P _i Is a current active coefficient matrix, < >>For a sixth matrix, Y _Cf For filter capacitance matrix, Z _GFM Is the AC port impedance of the network-structured converter.

the fourth, fifth and sixth matrices are as follows:

in the above, H _qd (s) is a sagging control transfer function, H _v (s ₁ ) For the transfer function of the voltage controller, H _i (s ₁ ) As a function of the transfer of the current controller,Q _i is a matrix of reactive current coefficients,Q _v is a matrix of reactive voltage coefficients, which is a matrix of reactive voltage coefficients,D _di is a matrix of d-axis current coefficients,D _qi for the q-axis current coefficient matrix,B _dv is a matrix of d-axis voltage coefficients,B _qv for the q-axis voltage coefficient matrix,B _dθ is a d-axis voltage-synchronous angle coefficient matrix,B _qθ for the q-axis voltage-synchronization angle coefficient matrix,D _dθ for the d-axis current-synchronization angle coefficient matrix, D _qθ For q-axis current-synchronous angular coefficient matrix, K _d Is a current loop decoupling coefficient;

Example 3

Based on the same inventive concept, the invention also provides a computer device comprising a processor and a memory for storing a computer program comprising program instructions, the processor for executing the program instructions stored by the computer storage medium. The processor may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processor, digital signal processor (Digital Signal Processor, DSP), application specific integrated circuit (ApplicationSpecificIntegrated Circuit, ASIC), off-the-shelf Programmable gate array (FPGA) or other Programmable logic device, discrete gate or transistor logic device, discrete hardware components, etc., which are the computational core and control core of the terminal adapted to implement one or more instructions, in particular to load and execute one or more instructions in a computer storage medium to implement the corresponding method flow or corresponding functions, to implement the steps of a method for optimizing control parameters of a grid-connected converter in the above embodiments.

Example 4

Based on the same inventive concept, the present invention also provides a storage medium, in particular, a computer readable storage medium (Memory), which is a Memory device in a computer device, for storing programs and data. It is understood that the computer readable storage medium herein may include both built-in storage media in a computer device and extended storage media supported by the computer device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also stored in the memory space are one or more instructions, which may be one or more computer programs (including program code), adapted to be loaded and executed by the processor. The computer readable storage medium herein may be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one magnetic disk memory. One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the steps of a method for optimizing control parameters of a grid-tied converter in the above embodiments.

It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.

Claims

1. The method for optimizing the control parameters of the grid-formed converter is characterized by comprising the following steps of:

solving an active loop control parameter model under the dynamic response constraint condition of an active loop to obtain a first active loop control parameter of the grid-structured converter, solving an impedance analysis model of an alternating current port of the grid-structured converter under the strong constraint condition of the grid-structured converter, obtaining a second active loop control parameter of the grid-structured converter, and taking the intersection of the first active loop control parameter of the grid-structured converter and the second active loop control parameter of the grid-structured converter as the active loop control parameter of the grid-structured converter;

taking the current loop control parameter, the voltage loop control parameter and the active loop control parameter as a grid-formed converter control parameter optimization scheme;

the current loop control parameter model is as follows:

In the above, G _i (s) is the current loop open loop transfer function, s is the first laplace operator, s=j2pi×f _p ，f _p For the disturbance frequency, j is the imaginary unit,for a given value corresponding to the current loop bandwidth, +.>For a given value corresponding to the phase margin of the current loop, +.>Is the circumference ratio;

the current loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row and column element in the open loop transfer function matrix of the current loop, < >>For the first row and the second column elements in the current loop open-loop transfer function matrix, < >>For the first column element of the second row in the current loop open-loop transfer function matrix,/for the second row in the current loop open-loop transfer function matrix>A second row and a second column of elements in the open loop transfer function matrix for the current loop, wherein:

2. The method of claim 1, wherein the current loop dynamic response constraint condition comprises that the power grid equivalent inductance is larger than a preset strong and weak power grid equivalent inductance demarcation value, and the current loop bandwidth and the phase margin are respectively equal to the corresponding given values;

3. The method of claim 1, wherein the active ring dynamic response constraint comprises: the equivalent inductance of the power grid is larger than the preset equivalent inductance demarcation value of the strong and weak power grid, and the bandwidth of the active zone is equal to the corresponding given value;

4. The method of claim 1, wherein the current loop control parameters of the grid-tied converter comprise: current loop ratio coefficient and integral coefficient; the voltage loop control parameters of the grid-connected converter comprise: voltage loop ratio coefficient and integral coefficient; the active loop control parameters of the network-structured converter comprise: active sag coefficient and inertia coefficient.

5. The method of claim 1, wherein the first coefficient matrix, the second coefficient matrix, and the third coefficient matrix are as follows:

6. The method of claim 5, wherein the voltage loop control parameter model is as follows:

7. The method of claim 6, wherein the voltage loop open loop transfer function is as follows:

in the above-mentioned method, the step of,for the first row, column element in the open-loop transfer function matrix of the voltage loop, < >>For the first row, the second column element in the voltage loop open-loop transfer function matrix, < >>For the first column element of the second row in the voltage loop open-loop transfer function matrix,/for the second row in the voltage loop open-loop transfer function matrix>For a second row and a second column of elements in the voltage loop open-loop transfer function matrix, wherein:

8. The method of claim 7, wherein the active loop control parameter model is as follows:

in the above, G _p (s) is an active ring open loop transfer function, Is a given value corresponding to the active zone bandwidth.

9. The method of claim 8, wherein the active ring open loop transfer function is as follows:

10. The method of claim 9, wherein the mesh converter ac port impedance analysis model is as follows:

11. The method of claim 10, wherein the current and voltage active coefficient matrices are as follows:

in the above, F(s) ₁ ) For the transfer function of the sampler, V ₁ For a the steady-state fundamental frequency component of the alternating voltage,for the steady-state fundamental frequency component conjugation of a-phase alternating voltage I ₁ For a alternating current steady-state fundamental frequency component, +.>For the steady-state fundamental frequency component conjugation of a alternating current, s ₁ For the second Laplace operator, +.>，f _p For the disturbance frequency f ₁ For rated frequency +.>,/>,,/>, />For a phase of fundamental frequency component of alternating voltage, +.>A phase of the alternating current fundamental frequency component;

the fourth, fifth and sixth matrices are as follows:

in the above, K _m For PWM gain, V _dc Is the voltage of a direct current bus, T _s As a time constant matrix for delay, F _v As a matrix of voltage coefficients, F _i Is a current systemNumber matrix, F _θ Is a synchronous angle coefficient matrix;

In the above, H _qd (s) is a sagging control transfer function, H _v (s ₁ ) For the transfer function of the voltage controller, H _i (s ₁ ) As a function of the transfer of the current controller,Q _i is a matrix of reactive current coefficients,Q _v is a matrix of reactive voltage coefficients, which is a matrix of reactive voltage coefficients,D _di is a matrix of d-axis current coefficients,D _qi for the q-axis current coefficient matrix,B _dv is d-axisA matrix of voltage coefficients is provided which,B _qv for the q-axis voltage coefficient matrix,B _dθ is a d-axis voltage-synchronous angle coefficient matrix,B _qθ for the q-axis voltage-synchronization angle coefficient matrix,D _dθ for the d-axis current-synchronization angle coefficient matrix,D _qθ for q-axis current-synchronous angular coefficient matrix, K _d Is a current loop decoupling coefficient;

12. A method according to claim 3, wherein the stability constraints under the grid-tied converter strong grid include:

in the above, Z _g For the impedance of the electric network, Z _GFM For the ac port impedance of the grid-formed converter,for a given value corresponding to the active loop phase margin, < >>Is of circumference rate >And j is an imaginary unit for a given value corresponding to the active zone bandwidth.

13. An apparatus based on the method of optimizing control parameters of a grid-tied converter according to any one of claims 1 to 12, characterized in that it comprises:

the second analysis module is used for solving the active loop control parameter model under the dynamic response constraint condition of the active loop to obtain a first active loop control parameter of the grid-structured converter, solving the alternating current port impedance analysis model of the grid-structured converter under the stability constraint condition of the strong grid of the grid-structured converter to obtain a second active loop control parameter of the grid-structured converter, and taking the intersection of the first active loop control parameter of the grid-structured converter and the second active loop control parameter of the grid-structured converter as the active loop control parameter of the grid-structured converter;

14. A computer device, comprising: one or more processors;

the processor is used for executing one or more programs;

the method for optimizing control parameters of a grid-built converter according to any one of claims 1 to 12, when said one or more programs are executed by said one or more processors.

15. A computer readable storage medium, having stored thereon a computer program which, when executed, implements the grid-tied converter control parameter optimization method of any one of claims 1 to 12.