CN111276993A - Controller parameter setting method, medium and equipment applied to high-voltage direct-current transmission - Google Patents

Controller parameter setting method, medium and equipment applied to high-voltage direct-current transmission Download PDF

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CN111276993A
CN111276993A CN202010073348.9A CN202010073348A CN111276993A CN 111276993 A CN111276993 A CN 111276993A CN 202010073348 A CN202010073348 A CN 202010073348A CN 111276993 A CN111276993 A CN 111276993A
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CN111276993B (en
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汪娟娟
陈威
叶运铭
龚英明
文兆新
吴秋媚
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South China University of Technology SCUT
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract

The invention discloses a controller parameter setting method, medium and equipment applied to high-voltage direct-current transmission, wherein the method comprises the steps of firstly obtaining network parameters and controller parameters of a high-voltage direct-current transmission system; the system is subdivided into submodules, and the submodules are described by using differential equations and algebraic equations to obtain a state space model; then linearizing the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model; calculating characteristic values of the matrix A under different parameter values; screening the characteristic values to determine a stable region of the controller parameters; converting the small interference dynamic model into a transfer function model, calculating the transfer function of a constant current controller or a constant voltage controller, and acquiring the unit step response of the transfer function; and calculating a dynamic time domain index according to the unit step response curve, and acquiring the optimal controller parameter according to the ITAE criterion. The invention can effectively improve the operating characteristics of the high-voltage direct-current transmission system and improve the small interference stability of the system.

Description

Controller parameter setting method, medium and equipment applied to high-voltage direct-current transmission
Technical Field
The invention relates to the technical field of small interference stability analysis of an alternating current and direct current transmission system, in particular to a method, medium and equipment for setting parameters of a controller applied to high-voltage direct current transmission.
Background
The high-voltage direct-current transmission of the power grid commutation converter has the advantages of long transmission distance, large capacity, low loss, mature technology and the like, and plays an important role in realizing optimal configuration of cross-regional power resources. However, with the continuous input of the direct current transmission project, the transmission capacity is continuously increased, the strength of the alternating current system on the inversion side is reduced, the stability problem of the system is seriously tested, and various problems such as phase commutation failure, subsynchronous oscillation, oscillation divergence or low-frequency oscillation are easy to occur in a weak alternating current system. The operating characteristics of the high-voltage direct-current transmission system can be effectively improved by reasonably selecting the parameters of the controller, and the small interference stability of the system is improved.
At present, the controller parameters of the actual high-voltage direct-current transmission project in China are mainly obtained through a trial and error method, the method is blindness and low in efficiency, only time domain information can be given when time domain simulation is adopted, frequency domain information does not exist, and the stability margin of a system cannot be given. The small interference stability analysis can be used for mining the oscillation frequency and damping condition of each oscillation mode of the system, and provides a theoretical basis for inhibiting the low-frequency oscillation of the system and setting the parameters of the controller. At present, the modeling method of the converter in China mainly adopts a quasi-steady-state formula, and the method omits the phase change process of the current on the valve side, so that a more detailed converter model is necessary to be established to improve the accuracy of an analysis result. In addition, two control strategies are mainly adopted in the current actual direct current transmission project: ABB control strategy and SIEMENS control strategy. In the ABB control strategy, a prediction type constant turn-off angle control is adopted on the inversion side in a steady state, and a parameter setting method aiming at the prediction type constant turn-off angle controller is rarely adopted at present.
In short, the existing controller parameter setting method for the direct current transmission project is low in efficiency and large in calculation amount, so that a controller parameter setting method which is efficient, strong in reliability and suitable for the actual direct current transmission project needs to be researched.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a controller parameter setting method applied to high-voltage direct-current transmission, which can effectively improve the operating characteristics of a high-voltage direct-current transmission system and improve the small-interference stability of the system.
A second object of the present invention is to provide a storage medium.
It is a third object of the invention to provide a computing device.
The first purpose of the invention is realized by the following technical scheme: a controller parameter setting method applied to high-voltage direct-current transmission comprises the following steps:
s1, acquiring network parameters and controller parameters of the high-voltage direct-current power transmission system;
s2, subdividing the high-voltage direct-current power transmission system into sub-modules, and describing each sub-module by using a differential equation and an algebraic equation based on network parameters and controller parameters to obtain a state space model of the high-voltage direct-current power transmission system;
s3, linearizing the state space model at a balance point of the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model of the high-voltage direct-current power transmission system;
s4, determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values based on the research range and the change step length;
screening the characteristic values, and obtaining a stable region of the controller parameters according to the screened characteristic values;
s5, converting a small interference dynamic model of the high-voltage direct-current power transmission system into a transfer function model, calculating a transfer function of a constant current controller or a constant voltage controller, and acquiring unit step response of the transfer function to obtain a unit step response curve;
and S6, calculating dynamic time domain indexes including overshoot and adjusting time according to the unit step response curve, and acquiring optimal controller parameters according to the ITAE criterion based on the dynamic time domain indexes.
Preferably, a rectification side of the high-voltage direct-current transmission system adopts constant current control, an inversion side adopts constant voltage control or prediction type constant turn-off angle control, and a phase-locked loop adopts a synchronous rotating coordinate phase-locked loop;
the controller parameters include: proportionality coefficient K of constant current controllerPIdcAnd integral coefficient KiIdcAnd the proportionality coefficient K of the rectification side phase-locked looppPLL1And integral coefficient KiPLL1Proportionality coefficient K of inversion side phase-locked looppPLL2And integral coefficient KiPLL2Constant voltage controller proportionality coefficient KpVOr the integral coefficient KiVOr a current deviation coefficient K of the predictive type constant off-angle control.
Preferably, in step S2, the sub-modules include an ac system, a filter, a converter, a dc transmission line and a control system;
describing each sub-module by using a differential equation and an algebraic equation to obtain a state space model of the high-voltage direct-current power transmission system, which is as follows:
(1) the direct current transmission line adopts a T-shaped equivalent circuit, and the state space model of the direct current transmission line is as follows:
Figure BDA0002377828120000031
wherein subscript 1 represents the rectification side; subscript 2 represents the inversion side; i isdc1Is direct current at the rectifying side; i isdc2The direct current is the direct current of the inversion side; rdcIs the resistance of the transmission line; l isdcIs the inductance of the transmission line; u shapedcCIs the capacitance voltage of the transmission line; cdcIs the capacitance of the transmission line;
Lec1equivalent inductance on the DC side for the rectifier-side converter, Lec2The equivalent inductance of the inverter side converter on the direct current side is represented by the following expression:
Figure BDA0002377828120000032
in the expression, μ1、μ2Respectively a rectification side commutation angle and an inversion side commutation angle; l isT1And LT2Respectively providing an equivalent inductance of the rectifier side converter transformer at the valve side and an equivalent inductance of the inverter side converter transformer at the valve side;
Udc1the expression is the mean value of the direct current voltage on the rectifying side:
Figure BDA0002377828120000033
in the expression, V1The effective value of the voltage of a no-load line at the valve side of a converter transformer at the rectification side; xT1α is a hysteresis trigger angle;
Udc2the average value of the DC voltage on the inversion side is expressed as follows:
Figure BDA0002377828120000034
wherein β is the leading flip angle of the inverter side, V2The effective value of the voltage of the no-load line at the valve side of the inverter side converter transformer is obtained; xT2The equivalent short-circuit reactance is arranged on the valve side of the inverter side converter transformer;
(2) the state space equations of the alternating current system and the filter take the inductive current and the capacitance voltage of a line as state variables, and corresponding state space equations are written according to a KCL or KVL law;
(3) considering the commutation process of the current at the valve side of the converter, the input-output relation of the converter is described by adopting a switching function method, wherein,
for a rectifier side converter, when only the fundamental wave of the valve side current is considered, the converter valve side current is represented as:
Figure BDA0002377828120000035
Figure BDA0002377828120000041
wherein ia、ib、icThe current of the valve side of the converter is the current; i isdc1Is direct current at the rectifying side; sia、Sib、SicA switching function for each phase current; omega0Is the rated angular frequency; t is time; theta01Is the initial phase of the AC bus voltage at the rectification side;
Figure BDA0002377828120000048
is the power factor angle;
according to Park transformation, the current on the network side of the rectification side is expressed as follows under a dq rotation coordinate system:
Figure BDA0002377828120000042
wherein icd1、icq1D-axis and q-axis components of the rectified side grid side current respectively; k1For the conversion ratio of the rectifier side converter transformer, theta01The initial phase of the alternating current bus voltage at the rectification side is obtained;
Figure BDA0002377828120000043
the primary phase of the alternating current bus voltage output by the rectification side phase-locked loop;
for an inverter-side converter, the grid-side current is expressed in dq rotation coordinate system as:
Figure BDA0002377828120000044
wherein icd2、icq2D-axis and q-axis components of the inverter side network side current respectively; k2For the transformation ratio of the inverter-side converter transformer, theta02The primary phase of the AC bus voltage at the inversion side is adopted;
Figure BDA0002377828120000045
the primary phase of the alternating current bus voltage output by the inversion side phase-locked loop is obtained; i isdc2The direct current is the direct current of the inversion side;
(4) the rectification side adopts a constant current control mode, and a state space equation and an algebraic equation of a constant current controller are as follows:
Figure BDA0002377828120000046
Figure BDA0002377828120000047
wherein x is10Is an intermediate variable; i isordThe command value is controlled by constant current; i isdc1mIs a direct current Idc1Measuring values after first-order inertia link filtering; g1、TIdcRespectively is a proportionality coefficient and an inertia time constant of a first-order inertia link; kpIdcProportional coefficient for constant current control; kiIdcAn integral coefficient for constant current control;
(5) the inverter side adopts a constant voltage control mode or a prediction type constant turn-off angle control mode, wherein a state space equation and an algebraic equation of the constant voltage controller are as follows:
Figure BDA0002377828120000051
Figure BDA0002377828120000052
in the expression, x20Is an intermediate variable; u shapedcrefThe direct current voltage instruction value is the direct current voltage instruction value of the inverter station; u shapedc2mIs a direct current voltage Udc2Measuring values after first-order inertia link filtering; kp1、Ki1Proportional coefficient and integral coefficient of constant voltage control respectively; g2And Tm1Respectively is a proportionality coefficient and a time constant of an inertia link;
the state space equation and the algebraic equation of the prediction type constant turn-off angle control mode are as follows:
Figure BDA0002377828120000053
Figure BDA0002377828120000054
in the expression, Idc2mIs a direct current Idc2Measuring the value after a first-order inertia link; g3The direct current is a proportional coefficient of an inversion side direct current filtering link; t ism3The inertia time constant of the inversion side direct current filtering link is obtained; t ism2An inertia time constant for current deviation control; x is the number of30Is an intermediate variable; k is a current deviation proportionality coefficient; gamma ray0Setting value of the turn-off angle; dxThe unit value is the equivalent commutation reactance of the inversion side; i isdNIs a rated value of the direct current; u shapedi0NThe rated value is the ideal no-load direct current voltage of the inversion side; u shapedi0The voltage is an ideal no-load direct current voltage of an inversion side;
(6) the rectification side and the inversion side both adopt synchronous rotating coordinate phase-locked loops, and the output of the phase-locked loops is defined as
Figure BDA0002377828120000055
Figure BDA0002377828120000056
The state space equation and the algebraic equation are as follows:
Figure BDA0002377828120000057
Figure BDA0002377828120000058
Figure BDA0002377828120000059
Figure BDA0002377828120000061
wherein, theta1For rectifying side locksThe phase of the AC bus voltage output by the phase loop; theta2The phase of the alternating current bus voltage output by the inversion side phase-locked loop; x is the number of11、x12Is an intermediate variable; kpPLL1、KpPLL2Proportional coefficients of rectification and inversion side phase-locked loop control are respectively; kiPLL1、KiPLL2Integral coefficients of rectification and inversion side phase-locked loop control are respectively; v. ofPCCd1、vPCCq1D-axis components and q-axis components of the rectified side alternating current bus voltage respectively; v. ofPCCd2、vPCCq2D-axis components and q-axis components of the inverter side bus voltage respectively; omega1The power grid angular frequency is output by the rectification side phase-locked loop; omega2The grid angular frequency is output by the inverter side phase-locked loop.
Preferably, in step S3, the state space model is linearized at the equilibrium point of the state space model, and the obtained small interference dynamic model is as follows:
Figure BDA0002377828120000062
in the model, A is a state space matrix; b is an input matrix; c is an output matrix; d is a feedforward matrix; Δ represents the amount of change in the parameter; x is a system state variable column vector; u is an input vector; y is a system output vector; when the inversion side adopts a constant voltage control mode, U is equal to [ I ]ord，Udcref]TWhen the inverter side adopts a prediction type constant turn-off angle control mode, U is equal to [ I ]ord，γ0]T，IordFor command values of constant current control, UdcrefFor a DC voltage command value, gamma, of the inverter station0For the setting of the off-angle, T represents the transpose of the matrix.
Preferably, in step S4, the eigenvalues of the matrix a under different parameter values are calculated by using a control variable method, which is specifically as follows:
aiming at each controller parameter needing to be researched, only changing the value of the parameter based on the research range and the change step length of the parameter, keeping the values of other parameters unchanged, calculating to obtain the minimum value and the maximum value of each controller parameter, and simultaneously calculating the characteristic value of the matrix A under different values.
Preferably, in step S4, the characteristic values are filtered, and a stable domain of the controller parameter is obtained according to the filtered characteristic values, which is as follows:
screening the characteristic values for the first time according to the condition that the real part of the characteristic value is less than 0, and selecting the characteristic value with the real part of the characteristic value less than 0;
aiming at each screened characteristic value, calculating the damping ratio zeta of the oscillation mode corresponding to each characteristic value according to a damping ratio calculation formula:
Figure BDA0002377828120000063
in the formula, σ is the real part of the eigenvalue, and ω is the imaginary part of the eigenvalue;
according to the condition that the minimum value of the oscillation mode damping ratio is larger than the threshold value, carrying out secondary screening on the characteristic values screened out for the first time, and selecting the characteristic values of which the minimum value of the oscillation mode damping ratio is larger than the threshold value, so as to obtain a stable region of the controller parameters;
modifying the controller parameters of which the real part of the characteristic value is not less than 0 or the minimum value of the damping ratio of the oscillation mode is not more than a threshold value;
and repeating the two screening and parameter changing until all the parameters of the controller meet the condition that the real part of the characteristic value is less than 0 and the minimum value of the damping ratio of the oscillation mode is greater than a threshold value, so as to complete the optimization of the controller.
Preferably, in step S5, the small disturbance dynamic model of the hvdc transmission system is converted into a transfer function model according to the conversion relation expression:
Η(s)＝C(sI-A)-1B+D；
in the formula, s is Laplace operator; h(s) is the closed-loop transfer function between the output and the output; i is an identity matrix; c is an output matrix; d is a feedforward matrix;
calculating a transfer function of a constant current controller or a constant voltage controller according to the model, wherein for the constant current controller, the input is a constant current instruction value, and the output is direct current at the rectifying side; for the constant voltage controller, the input is a constant voltage command value, and the output is an inverter-side direct-current voltage.
Preferably, in step S6, the overshoot and the adjustment time are calculated specifically as follows:
let T be the time when the step response reaches the steady state value, Δ Y (T) be the response curve, and T be the sampling interval0If sampling is started from 0 moment, the steady state value is delta Y (T), and the peak value is max (delta Y (t));
defining overshoot as a percentage of the ratio of the difference between the peak and steady state values to the steady state value, the overshoot being calculated as follows:
Figure BDA0002377828120000071
defining an adjustment time tsThe minimum time required for the response to reach and remain within ± 2% of the steady state value;
obtaining optimal controller parameters according to an ITAE criterion, specifically: aiming at the controller parameter combination corresponding to the characteristic value screened out in the step S4, calculating an objective function corresponding to each group of parameters according to an objective function expression of time multiplied by absolute error integral ITAE until the calculation is traversed to the last group of parameters, and then selecting the optimal controller parameter combination;
the target function expression is specifically as follows:
Figure BDA0002377828120000072
in the formula, the upper limit of integration tsTo adjust the time; e (t) is the absolute error integral; j. the design is a squareITAEIs an objective function, JITAEThe controller parameter corresponding to the minimum value of (a) is the optimal controller parameter combination.
The second purpose of the invention is realized by the following technical scheme: a storage medium stores a program which, when executed by a processor, implements a controller parameter tuning method for high-voltage direct-current power transmission according to a first object of the present invention.
The third purpose of the invention is realized by the following technical scheme: a computing device comprising a processor and a memory for storing a processor executable program, the processor, when executing the program stored in the memory, implementing the method for controller parameter tuning for high voltage direct current transmission according to the first object of the invention.
Compared with the prior art, the invention has the following advantages and effects:
(1) the invention relates to a controller parameter setting method applied to high-voltage direct-current transmission, which comprises the steps of firstly obtaining network parameters and controller parameters of a high-voltage direct-current transmission system; the system is subdivided into submodules, and the submodules are described by using differential equations and algebraic equations to obtain a state space model; then linearizing the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model; determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values; screening the characteristic values to determine a stable region of the controller parameters; converting the small interference dynamic model into a transfer function model, calculating the transfer function of a constant current controller or a constant voltage controller, and acquiring the unit step response of the transfer function; and calculating a dynamic time domain index according to the unit step response curve, and acquiring the optimal controller parameter according to the ITAE criterion. According to the method, the parameters of the controller are reasonably screened and then set and optimized, so that the optimization calculated amount of the controller is reduced, the optimization efficiency is higher, the operation characteristics of the high-voltage direct-current transmission system are effectively improved, and the small interference stability of the system is improved.
(2) The method considers the phase change process of the valve side current and the control mode of the predictive type fixed turn-off angle control, the established converter model is more detailed and comprehensive, and the accuracy and the reliability of the parameter setting of the controller are higher, so the method is more suitable for the actual direct current transmission engineering.
Drawings
Fig. 1 is a flowchart of a controller parameter setting method applied to high voltage direct current transmission according to the present invention.
Fig. 2 is a single line schematic of a high voltage direct current transmission system.
Fig. 3 is a control schematic diagram of the rectification side of the system of fig. 2.
Fig. 4 is a control schematic diagram of the inverter-side phase-locked loop of the system of fig. 2.
Fig. 5 is a schematic diagram of constant voltage control of the system of fig. 2.
Fig. 6 is a schematic diagram of predictive constant-off angle control of the system of fig. 2.
FIG. 7 shows the parameter setting ranges of the constant current control proportional coefficient and the integral coefficient.
Fig. 8 is a unit step response curve of a constant current controller transfer function.
Fig. 9 is a graph of the change in regulation time with the change in the proportionality coefficient and the integral coefficient of the current controller.
FIG. 10 is a graph of overshoot as a function of the scaling factor and the integral factor of the current controller.
Fig. 11 is a comparison graph of a small disturbance dynamic model and an electromagnetic transient model at a constant current command value step.
FIG. 12 is a comparison of a small disturbance dynamic model and an electromagnetic transient model at a constant voltage command value step.
Fig. 13 is an electromagnetic transient simulation diagram of the switching of the proportional coefficient and the integral coefficient of the direct current on the inversion side in the parameter setting range of fig. 7.
FIG. 14 is a graph of the step response of the constant current controller of the system of FIG. 2 for the controller parameters before and after optimization.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
The embodiment discloses a controller parameter setting method applied to high-voltage direct-current transmission, as shown in fig. 1, the method comprises the following steps:
and S1, acquiring network parameters and controller parameters of the high-voltage direct-current power transmission system. The rectification side of the high-voltage direct-current transmission system adopts constant current control, the inversion side adopts constant voltage control or prediction type constant turn-off angle control, and the phase-locked loop adopts a synchronous rotating coordinate phase-locked loop.
The controller parameters include: proportionality coefficient K of constant current controllerPIdcAnd integral coefficient KiIdcAnd the proportionality coefficient K of the rectification side phase-locked looppPLL1And integral coefficient KiPLL1Proportionality coefficient K of inversion side phase-locked looppPLL2And integral coefficient KiPLL2Constant voltage controller proportionality coefficient KpVOr the integral coefficient KiVOr a current deviation coefficient K of the predictive type constant off-angle control.
S2, subdividing the high-voltage direct-current transmission system into sub-modules including an alternating-current system, a filter, a current converter, a direct-current transmission line and a control system, and describing each sub-module by using a differential equation and an algebraic equation based on network parameters and controller parameters to obtain a state space model of the high-voltage direct-current transmission system, wherein the state space model is as follows:
(1) the direct current transmission line adopts a T-shaped equivalent circuit, and the state space model of the direct current transmission line is as follows:
Figure BDA0002377828120000091
wherein subscript 1 represents the rectification side; subscript 2 represents the inversion side; i isdc1Is direct current at the rectifying side; i isdc2The direct current is the direct current of the inversion side; rdcIs the resistance of the transmission line; l isdcIs the inductance of the transmission line; u shapedcCIs the capacitance voltage of the transmission line; cdcIs the capacitance of the transmission line;
Lec1equivalent inductance on the DC side for the rectifier-side converter, Lec2The equivalent inductance of the inverter side converter on the direct current side is represented by the following expression:
Figure BDA0002377828120000101
in the expression, μ1、μ2Respectively a rectification side commutation angle and an inversion side commutation angle; l isT1And LT2Equivalent inductance of the rectifier side converter transformer on the valve side and the inverter side converter transformerThe equivalent inductance of the pressure device on the valve side;
Udc1the expression is the mean value of the direct current voltage on the rectifying side:
Figure BDA0002377828120000102
in the expression, V1The effective value of the voltage of a no-load line at the valve side of a converter transformer at the rectification side; xT1The equivalent short-circuit reactance of the valve side of the converter transformer at the rectifier side, and α is a hysteresis trigger angle.
Udc2The average value of the DC voltage on the inversion side is expressed as follows:
Figure BDA0002377828120000103
wherein β is the leading flip angle of the inverter side, V2The effective value of the voltage of the no-load line at the valve side of the inverter side converter transformer is obtained; xT2The equivalent short-circuit reactance is arranged on the valve side of the inverter side converter transformer;
(2) the state space equations of the alternating current system and the filter take the inductive current and the capacitance voltage of a line as state variables, and corresponding state space equations are written according to the KCL or KVL law.
(3) Considering the commutation process of the current at the valve side of the converter, the input-output relation of the converter is described by adopting a switching function method, wherein,
for a rectifier side converter, when only the fundamental wave of the valve side current is considered, the converter valve side current is represented as:
Figure BDA0002377828120000104
Figure BDA0002377828120000105
wherein ia、ib、icThe current of the valve side of the converter is the current; i isdc1Is direct current at the rectifying side; sia、Sib、SicA switching function for each phase current; omega0Is the rated angular frequency; t is time; theta01Is the initial phase of the AC bus voltage at the rectification side;
Figure BDA0002377828120000111
is the power factor angle;
according to Park transformation, the current on the network side of the rectification side is expressed as follows under a dq rotation coordinate system:
Figure BDA0002377828120000112
wherein icd1、icq1D-axis and q-axis components of the rectified side grid side current respectively; k1For the conversion ratio of the rectifier side converter transformer, theta01The initial phase of the alternating current bus voltage at the rectification side is obtained;
Figure BDA0002377828120000113
the primary phase of the alternating current bus voltage output by the rectification side phase-locked loop;
for an inverter-side converter, the grid-side current is expressed in dq rotation coordinate system as:
Figure BDA0002377828120000114
wherein icd2、icq2D-axis and q-axis components of the inverter side network side current respectively; k2For the transformation ratio of the inverter-side converter transformer, theta02The primary phase of the AC bus voltage at the inversion side is adopted;
Figure BDA0002377828120000115
the primary phase of the alternating current bus voltage output by the inversion side phase-locked loop is obtained; i isdc2The direct current is the direct current of the inversion side.
(4) The rectification side adopts a constant current control mode, and a state space equation and an algebraic equation of a constant current controller are as follows:
Figure BDA0002377828120000116
Figure BDA0002377828120000117
wherein x is10Is an intermediate variable; i isordThe command value is controlled by constant current; i isdc1mIs a direct current Idc1Measuring values after first-order inertia link filtering; g1、TIdcRespectively is a proportionality coefficient and an inertia time constant of a first-order inertia link; kpIdcProportional coefficient for constant current control; kiIdcIs the integral coefficient of constant current control.
(5) The inverter side adopts a constant voltage control mode or a prediction type constant turn-off angle control mode, wherein a state space equation and an algebraic equation of the constant voltage controller are as follows:
Figure BDA0002377828120000118
Figure BDA0002377828120000119
in the expression, x20Is an intermediate variable; u shapedcrefThe direct current voltage instruction value is the direct current voltage instruction value of the inverter station; u shapedc2mIs a direct current voltage Udc2Measuring values after first-order inertia link filtering; kp1、Ki1Proportional coefficient and integral coefficient of constant voltage control respectively; g2And Tm1Respectively, the proportionality coefficient and the time constant of the inertia link.
The state space equation and the algebraic equation of the prediction type constant turn-off angle control mode are as follows:
Figure BDA0002377828120000121
Figure BDA0002377828120000122
in the expression, Idc2mIs straightCurrent Idc2Measuring the value after a first-order inertia link; g3The direct current is a proportional coefficient of an inversion side direct current filtering link; t ism3The inertia time constant of the inversion side direct current filtering link is obtained; t ism2An inertia time constant for current deviation control; x is the number of30Is an intermediate variable; k is a current deviation proportionality coefficient; gamma ray0Setting value of the turn-off angle; dxThe unit value is the equivalent commutation reactance of the inversion side; i isdNIs a rated value of the direct current; u shapedi0NThe rated value is the ideal no-load direct current voltage of the inversion side; u shapedi0The voltage is an ideal no-load direct current voltage of an inversion side.
(6) The rectification side and the inversion side both adopt synchronous rotating coordinate phase-locked loops, and the output of the phase-locked loops is defined as
Figure BDA0002377828120000123
Figure BDA0002377828120000124
The state space equation and the algebraic equation are as follows:
Figure BDA0002377828120000125
Figure BDA0002377828120000126
Figure BDA0002377828120000127
Figure BDA0002377828120000128
wherein, theta1The phase of the alternating current bus voltage output by the rectification side phase-locked loop; theta2The phase of the alternating current bus voltage output by the inversion side phase-locked loop; x is the number of11、x12Is an intermediate variable; kpPLL1、KpPLL2Proportional coefficients of rectification and inversion side phase-locked loop control are respectively; kiPLL1、KiPLL2Integral coefficients of rectification and inversion side phase-locked loop control are respectively; v. ofPCCd1、vPCCq1D-axis components and q-axis components of the rectified side alternating current bus voltage respectively; v. ofPCCd2、vPCCq2D-axis components and q-axis components of the inverter side bus voltage respectively; omega1The power grid angular frequency is output by the rectification side phase-locked loop; omega2The grid angular frequency is output by the inverter side phase-locked loop.
In this embodiment, the established state space model has the following basic form:
Figure BDA0002377828120000131
wherein the content of the first and second substances,
Figure BDA0002377828120000132
x is a system state variable column vector, U is an input vector, Y is a system output vector, F is a nonlinear function vector in which state variables are connected with the input vector, G is a nonlinear function vector in which the state variables, the input variables and the output variables are connected, n is the number of the state variables, r is the number of the input variables, and m is the number of the output variables.
When the differentials of all the state variables are 0 at the same time, the state at this time is called an equilibrium point.
S3, linearizing the state space model at the balance point of the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model of the high-voltage direct-current power transmission system, wherein the model is as follows:
Figure BDA0002377828120000133
in the model, A is a state space matrix; b is an input matrix; c is an output matrix; d is a feedforward matrix; Δ represents the amount of change in the parameter; when the inversion side adopts a constant voltage control mode, U is equal to [ I ]ord，Udcref]TWhen the inversion side adopts predictionWhen the mode is fixed and the angle is controlled, U ═ Iord，γ0]T(ii) a T denotes the transpose of the matrix.
And S4, determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values based on the research range and the change step length. In this embodiment, the eigenvalues of the matrix a under different parameter values are calculated by using a control variable method, which is specifically as follows:
(1) aiming at each controller parameter needing to be researched, only changing the value of the parameter based on the research range and the change step length of the parameter, keeping the values of other parameters unchanged, calculating to obtain the minimum value and the maximum value of each controller parameter, and simultaneously calculating the characteristic value of the matrix A under different values.
(2) Then, the characteristic values are screened, and a stable region of the controller parameter is obtained according to the screened characteristic values, which is as follows:
screening the characteristic values for the first time according to the condition that the real part of the characteristic value is less than 0, and selecting the characteristic value with the real part of the characteristic value less than 0;
aiming at each screened characteristic value, calculating the damping ratio zeta of the oscillation mode corresponding to each characteristic value according to a damping ratio calculation formula:
Figure BDA0002377828120000141
in the formula, σ is the real part of the eigenvalue, and ω is the imaginary part of the eigenvalue;
and according to the condition that the minimum value of the oscillation mode damping ratio is larger than the threshold value, carrying out secondary screening on the characteristic values screened for the first time, and selecting the characteristic values of which the minimum value of the oscillation mode damping ratio is larger than the threshold value. The threshold value is typically taken to be 5%.
When the characteristic value of the positive real part appears or the damping ratio of the oscillation mode is lower than the threshold value, the condition indicates that the high-voltage direct-current power transmission system is unstable under the parameter; and when all the characteristic values are negative real parts and the minimum value of the damping ratio of all the oscillation modes is greater than the threshold value, the high-voltage direct-current power transmission system is stable under the parameter, so that the stable domain of the controller parameter can be obtained according to the characteristic values which are selected twice and have the real parts smaller than 0 and the minimum value of the damping ratio of the oscillation modes greater than the threshold value.
(3) Modifying the controller parameters of which the real part of the characteristic value is not less than 0 or the minimum value of the damping ratio of the oscillation mode is not more than a threshold value;
and repeating the two screening and parameter changing until all the parameters of the controller meet the condition that the real part of the characteristic value is less than 0 and the minimum value of the damping ratio of the oscillation mode is greater than a threshold value, so as to complete the optimization of the controller.
S5, converting the small interference dynamic model of the high-voltage direct-current power transmission system into a transfer function model according to the conversion relation expression, wherein the model is as follows:
Η(s)＝C(sI-A)-1B+D；
wherein s is a Laplace operator; h(s) is the closed-loop transfer function between the output and the output; i is an identity matrix; c is an output matrix; d is a feedforward matrix;
and calculating according to the model to obtain a transfer function of the constant current controller or the constant voltage controller, and obtaining a unit step response of the transfer function to obtain a unit step response curve. For the constant current controller, the input is a constant current instruction value, and the output is direct current at the rectifying side; for the constant voltage controller, the input is a constant voltage command value, and the output is an inverter-side direct-current voltage.
S6, calculating a dynamic time domain index according to the unit step response curve, wherein the dynamic time domain index comprises overshoot and adjusting time, and the calculation is as follows:
let T be the time when the step response reaches the steady state value, Δ Y (T) be the response curve, and T be the sampling interval0If sampling is started from 0 moment, the steady state value is delta Y (T), and the peak value is max (delta Y (t));
defining overshoot as a percentage of the ratio of the difference between the peak and steady state values to the steady state value, the overshoot being calculated as follows:
Figure BDA0002377828120000142
defining an adjustment time tsThe minimum time required for the response to reach and remain within ± 2% of the steady state value;
then based on the dynamic time domain index, obtaining the optimal controller parameter according to the ITAE criterion, specifically: for the controller parameter combinations corresponding to the eigenvalues selected in step S4, calculating an objective function corresponding to each set of parameters according to an objective function expression of time-multiplied-by-absolute-error-Integral (ITAE) until the calculation is traversed to the last set of parameters, and then selecting the optimal controller parameter combination from the parameters;
the target function expression is specifically as follows:
Figure BDA0002377828120000151
in the formula, the upper limit of integration tsTo adjust the time; e (t) is the absolute error integral; j. the design is a squareITAEIs an objective function. Time-by-absolute error integral JITAEThe comprehensive performance index is used for measuring the excellent degree of the control system except the performance indexes such as overshoot, adjusting time and the like, and the smaller the value is, the better the dynamic performance is. Thus, JITAEThe controller parameter corresponding to the minimum value of (a) is the optimal controller parameter combination, and the system small interference stability under the parameter combination is optimal.
In this embodiment, the high-voltage direct-current transmission system is a CIGRE high-voltage direct-current standard test model, a single-line schematic diagram of the system is shown in fig. 2, system parameters are shown in table 1, and controller parameters are shown in table 2.
TABLE 1
Figure BDA0002377828120000152
TABLE 2
Figure BDA0002377828120000153
The control principle of the constant current controller and the control principle of the rectification side phase-locked loop are shown in fig. 3, the control principle of the inversion side phase-locked loop is shown in fig. 4, the control principle of the constant voltage controller is shown in fig. 5, the principle of the prediction type constant turn-off angle control is shown in fig. 6, and the principle diagrams correspond to corresponding state space equations one by one. The high-voltage direct-current transmission small-interference dynamic model is obtained by changing an inversion side control mode and a rectification side short-circuit ratio on the basis of a CIGRE high-voltage direct-current standard test model, and parameters such as reactance and transformation ratio of a phase-change transformer, a direct-current line and a filter are consistent with those of the CIGRE high-voltage direct-current standard test model.
When the inverter side adopts a constant voltage control mode,
Figure BDA0002377828120000161
Figure BDA0002377828120000162
Figure BDA0002377828120000163
U＝[Iord,Udcref]T；
when the inverter side adopts a prediction type constant turn-off angle control mode,
Figure BDA0002377828120000164
Figure BDA0002377828120000165
Figure BDA0002377828120000166
U＝[Iord,γ0]T。
in this embodiment, when the constant current control proportionality coefficient K is studiedpIdcAnd integral coefficient KiIdcIn the stable domain of (1), K can be selectedpIdcHas a variation range of [0.1, 5 ]]，KiIdcHas a variation range of [100, 600 ]]. Gradually increasing the proportional coefficient of the constant current controller from 0.01 to 5 and the integral coefficient from 100 to 600, and calculating the obtained controlThe stable range of the parameters of the device is shown in fig. 7, fig. 7 is a three-dimensional data graph, the z axis represents the damping ratio, and the larger the value is, the higher the small interference stability of the system is.
Taking the transfer function of the constant current controller as an example, the constant current command value is used as input, and the rectified side direct current is used as output. At the stable operating point, the unit step response curve is shown in fig. 8. Calculating overshoot and adjustment time according to the curve to obtain overshoot, adjustment time and JITAEWith KpIdcAnd KiIdcThe curve of the change.
FIG. 9 is a graph of adjustment time versus KpIdcAnd KiIdcGraph of the change, the z-axis represents the adjustment time. FIG. 10 is a graph of overshoot with KpIdcAnd KiIdcGraph of the variation, the z-axis represents the overshoot. This embodiment comprehensively considers overshoot, adjustment time, and JITAEFinally determined as JITAEThe controller parameter corresponding to the minimum value of (a) is taken as the optimized parameter, at this time KpIdc＝0.77，KiIdc＝110。
The embodiment also utilizes PSCAD/EMTDC software to establish a model of the high-voltage direct-current power transmission system, and the system parameters and the controller parameters of the model are the same as the small interference dynamic model, and the contents are verified through a simulation result.
In order to verify the correctness of the small interference dynamic model, the time domain responses of the electromagnetic transient model of the time domain response domain of the small interference dynamic model are compared, which specifically comprises the following steps:
taking the inverter side adopting a constant voltage control mode as an example, the system operates in a rated operation state in an initial state. At the 3 rd second, the current control command value I is fixeddcrefThe step change from 1.0 to 0.95 recovered from 0.95 to 1.0 after 1 second. The 6 th second timing voltage control instruction value U is used for controlling the system to be stabledcrefThe step change from 1.0 to 0.95 recovered to 1.0 after 1 second.
A comparison graph of the small-interference dynamic model and the electromagnetic transient model at the time of the step of the constant current command value is shown in fig. 11, and a comparison graph of the small-interference dynamic model and the electromagnetic transient model at the time of the step of the constant voltage command value is shown in fig. 12. It can be seen that the time domain response of the small interference dynamic model is substantially consistent with the time domain response of the electromagnetic transient model, and therefore the correctness of the small interference dynamic model is verified.
To verify the correctness of the controller parameter ranges shown in fig. 7, simulation verification is performed in the electromagnetic transient model, specifically as follows:
the initial state of the system is at a point A1 (K) within the stability region of FIG. 7pIdc＝2.2，KiIdc450), the control parameter is switched to a point B1 outside the stability domain at 3s (K)pIdc＝1，KiIdc450), the control parameter is switched to another point C1 (K) in the stable domain again at 4.9spIdc＝1，KiIdc＝150)。
The simulation result is shown in FIG. 13, and it can be seen from FIG. 13 that when the system parameter is switched from the stable domain inner fixed point A1 to the stable domain outer fixed point B1, i.e. KpIdcWhen the step is changed from 2.2 to 1, the direct current I on the inversion sidedc2The value begins to increase gradually, i.e. the system begins to diverge, and when the system parameter is switched from the point B1 to a point C1 or K in the stable domain againiIdcStep number 450 to 150, Idc2The system tends to a stable value, namely, the system gradually recovers to be stable, so that the correctness of the stable domain is verified, and meanwhile, the correctness and the validity of the parameter setting equation of the controller of the embodiment are also explained.
In order to verify the correctness of the algorithm of the present embodiment, the present embodiment also compares the step response of the constant current controller under the controller parameters before and after the setting optimization, and the comparison graph can be seen in fig. 14. As can be seen from fig. 14, the optimized overshoot is significantly reduced, the adjustment time is substantially consistent, which indicates that the step response is improved, and thus, the method of the embodiment can effectively improve the operating characteristics of the high-voltage direct-current transmission system and improve the small interference stability of the system.
Example 2
The present embodiment discloses a storage medium storing a program, which when executed by a processor, implements the method for setting the controller parameter applied to the high-voltage direct-current power transmission described in embodiment 1, specifically as follows:
s1, acquiring network parameters and controller parameters of the high-voltage direct-current power transmission system;
s2, subdividing the high-voltage direct-current power transmission system into sub-modules, and describing each sub-module by using a differential equation and an algebraic equation based on network parameters and controller parameters to obtain a state space model of the high-voltage direct-current power transmission system;
s3, linearizing the state space model at a balance point of the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model of the high-voltage direct-current power transmission system;
s4, determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values based on the research range and the change step length;
screening the characteristic values, and obtaining a stable region of the controller parameters according to the screened characteristic values;
s5, converting a small interference dynamic model of the high-voltage direct-current power transmission system into a transfer function model, calculating a transfer function of a constant current controller or a constant voltage controller, and acquiring unit step response of the transfer function to obtain a unit step response curve;
and S6, calculating dynamic time domain indexes including overshoot and adjusting time according to the unit step response curve, and acquiring optimal controller parameters according to the ITAE criterion based on the dynamic time domain indexes.
The storage medium in this embodiment may be a magnetic disk, an optical disk, a computer Memory, a Read-only Memory (ROM), a Random Access Memory (RAM), a usb disk, a removable hard disk, or other media.
Example 3
The embodiment discloses a computing device, which includes a processor and a memory for storing an executable program of the processor, and when the processor executes the program stored in the memory, the method for setting the controller parameter applied to the high-voltage direct-current power transmission described in embodiment 1 is implemented, specifically as follows:
s1, acquiring network parameters and controller parameters of the high-voltage direct-current power transmission system;
s2, subdividing the high-voltage direct-current power transmission system into sub-modules, and describing each sub-module by using a differential equation and an algebraic equation based on network parameters and controller parameters to obtain a state space model of the high-voltage direct-current power transmission system;
s3, linearizing the state space model at a balance point of the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model of the high-voltage direct-current power transmission system;
s4, determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values based on the research range and the change step length;
screening the characteristic values, and obtaining a stable region of the controller parameters according to the screened characteristic values;
s5, converting a small interference dynamic model of the high-voltage direct-current power transmission system into a transfer function model, calculating a transfer function of a constant current controller or a constant voltage controller, and acquiring unit step response of the transfer function to obtain a unit step response curve;
and S6, calculating dynamic time domain indexes including overshoot and adjusting time according to the unit step response curve, and acquiring optimal controller parameters according to the ITAE criterion based on the dynamic time domain indexes.
The computing device in this embodiment may be a desktop computer, a notebook computer, a tablet computer, an industrial personal computer, or other terminal devices with a processor function.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (10)

1. A controller parameter setting method applied to high-voltage direct-current transmission is characterized by comprising the following steps:
s1, acquiring network parameters and controller parameters of the high-voltage direct-current power transmission system;
s2, subdividing the high-voltage direct-current power transmission system into sub-modules, and describing each sub-module by using a differential equation and an algebraic equation based on network parameters and controller parameters to obtain a state space model of the high-voltage direct-current power transmission system;
s3, linearizing the state space model at a balance point of the state space model to obtain a state space matrix A, an input matrix B and a small interference dynamic model of the high-voltage direct-current power transmission system;
s4, determining the research range and the change step length of each controller parameter, and calculating the characteristic value of the matrix A under different parameter values based on the research range and the change step length;
screening the characteristic values, and obtaining a stable region of the controller parameters according to the screened characteristic values;
s5, converting a small interference dynamic model of the high-voltage direct-current power transmission system into a transfer function model, calculating a transfer function of a constant current controller or a constant voltage controller, and acquiring unit step response of the transfer function to obtain a unit step response curve;
and S6, calculating dynamic time domain indexes including overshoot and adjusting time according to the unit step response curve, and acquiring optimal controller parameters according to the ITAE criterion based on the dynamic time domain indexes.
2. The method according to claim 1, wherein a constant current control is adopted on a rectification side of the HVDC system, a constant voltage control or a predictive constant turn-off angle control is adopted on an inversion side, and a synchronous rotating coordinate phase-locked loop is adopted on the phase-locked loop;
the controller parameters include: proportionality coefficient K of constant current controllerPIdcAnd integral coefficient KiIdcAnd the proportionality coefficient K of the rectification side phase-locked looppPLL1And integral coefficient KiPLL1Proportionality coefficient K of inversion side phase-locked looppPLL2And integral coefficient KiPLL2Constant voltage controller proportionality coefficient KpVOr the integral coefficient KiVOr predictive turn-off angle controlThe coefficient of current deviation K.
3. The method for tuning controller parameters for HVDC transmission according to claim 1, wherein in step S2, the submodules include an AC system, a filter, a converter, a DC transmission line and a control system;
describing each sub-module by using a differential equation and an algebraic equation to obtain a state space model of the high-voltage direct-current power transmission system, which is as follows:
(1) the direct current transmission line adopts a T-shaped equivalent circuit, and the state space model of the direct current transmission line is as follows:
Figure FDA0002377828110000021
wherein subscript 1 represents the rectification side; subscript 2 represents the inversion side; i isdc1Is direct current at the rectifying side; i isdc2The direct current is the direct current of the inversion side; rdcIs the resistance of the transmission line; l isdcIs the inductance of the transmission line; u shapedcCIs the capacitance voltage of the transmission line; cdcIs the capacitance of the transmission line;
Lec1equivalent inductance on the DC side for the rectifier-side converter, Lec2The equivalent inductance of the inverter side converter on the direct current side is represented by the following expression:
Figure FDA0002377828110000022
in the expression, μ1、μ2Respectively a rectification side commutation angle and an inversion side commutation angle; l isT1And LT2Respectively providing an equivalent inductance of the rectifier side converter transformer at the valve side and an equivalent inductance of the inverter side converter transformer at the valve side;
Udc1the expression is the mean value of the direct current voltage on the rectifying side:
Figure FDA0002377828110000023
in the expression, V1The effective value of the voltage of a no-load line at the valve side of a converter transformer at the rectification side; xT1α is a hysteresis trigger angle;
Udc2the average value of the DC voltage on the inversion side is expressed as follows:
Figure FDA0002377828110000024
wherein β is the leading flip angle of the inverter side, V2The effective value of the voltage of the no-load line at the valve side of the inverter side converter transformer is obtained; xT2The equivalent short-circuit reactance is arranged on the valve side of the inverter side converter transformer;
(2) the state space equations of the alternating current system and the filter take the inductive current and the capacitance voltage of a line as state variables, and corresponding state space equations are written according to a KCL or KVL law;
(3) considering the commutation process of the current at the valve side of the converter, the input-output relation of the converter is described by adopting a switching function method, wherein,
for a rectifier side converter, when only the fundamental wave of the valve side current is considered, the converter valve side current is represented as:
Figure FDA0002377828110000025
Figure FDA0002377828110000031
wherein ia、ib、icThe current of the valve side of the converter is the current; i isdc1Is direct current at the rectifying side; sia、Sib、SicA switching function for each phase current; omega0Is the rated angular frequency; t is time; theta01Is the initial phase of the AC bus voltage at the rectification side;
Figure FDA0002377828110000032
is the power factor angle;
according to Park transformation, the current on the network side of the rectification side is expressed as follows under a dq rotation coordinate system:
Figure FDA0002377828110000033
wherein icd1、icq1D-axis and q-axis components of the rectified side grid side current respectively; k1For the conversion ratio of the rectifier side converter transformer, theta01The initial phase of the alternating current bus voltage at the rectification side is obtained;
Figure FDA0002377828110000034
the primary phase of the alternating current bus voltage output by the rectification side phase-locked loop;
for an inverter-side converter, the grid-side current is expressed in dq rotation coordinate system as:
Figure FDA0002377828110000035
wherein icd2、icq2D-axis and q-axis components of the inverter side network side current respectively; k2For the transformation ratio of the inverter-side converter transformer, theta02The primary phase of the AC bus voltage at the inversion side is adopted;
Figure FDA0002377828110000036
the primary phase of the alternating current bus voltage output by the inversion side phase-locked loop is obtained; i isdc2The direct current is the direct current of the inversion side;
(4) the rectification side adopts a constant current control mode, and a state space equation and an algebraic equation of a constant current controller are as follows:
Figure FDA0002377828110000037
Figure FDA0002377828110000038
wherein x is10Is an intermediate variable; i isordThe command value is controlled by constant current; i isdc1mIs a direct current Idc1Measuring values after first-order inertia link filtering; g1、TIdcRespectively is a proportionality coefficient and an inertia time constant of a first-order inertia link; kpIdcProportional coefficient for constant current control; kiIdcAn integral coefficient for constant current control;
(5) the inverter side adopts a constant voltage control mode or a prediction type constant turn-off angle control mode, wherein a state space equation and an algebraic equation of the constant voltage controller are as follows:
Figure FDA0002377828110000041
Figure FDA0002377828110000042
in the expression, x20Is an intermediate variable; u shapedcrefThe direct current voltage instruction value is the direct current voltage instruction value of the inverter station; u shapedc2mIs a direct current voltage Udc2Measuring values after first-order inertia link filtering; kp1、Ki1Proportional coefficient and integral coefficient of constant voltage control respectively; g2And Tm1Respectively is a proportionality coefficient and a time constant of an inertia link;
the state space equation and the algebraic equation of the prediction type constant turn-off angle control mode are as follows:
Figure FDA0002377828110000043
Figure FDA0002377828110000044
in the expression, Idc2mIs a direct current Idc2Measuring the value after a first-order inertia link; g3The direct current is a proportional coefficient of an inversion side direct current filtering link; t ism3For the direct current filtering ring at the inversion sideThe inertial time constant of the joint; t ism2An inertia time constant for current deviation control; x is the number of30Is an intermediate variable; k is a current deviation proportionality coefficient; gamma ray0Setting value of the turn-off angle; dxThe unit value is the equivalent commutation reactance of the inversion side; i isdNIs a rated value of the direct current; u shapedi0NThe rated value is the ideal no-load direct current voltage of the inversion side; u shapedi0The voltage is an ideal no-load direct current voltage of an inversion side;
(6) the rectification side and the inversion side both adopt synchronous rotating coordinate phase-locked loops, and the output of the phase-locked loops is defined as
Figure FDA0002377828110000045
Figure FDA0002377828110000046
The state space equation and the algebraic equation are as follows:
Figure FDA0002377828110000047
Figure FDA0002377828110000048
Figure FDA0002377828110000049
Figure FDA0002377828110000051
wherein, theta1The phase of the alternating current bus voltage output by the rectification side phase-locked loop; theta2The phase of the alternating current bus voltage output by the inversion side phase-locked loop; x is the number of11、x12Is an intermediate variable; kpPLL1、KpPLL2Proportional coefficients of rectification and inversion side phase-locked loop control are respectively; kiPLL1、KiPLL2Integral coefficients of rectification and inversion side phase-locked loop control are respectively; v. ofPCCd1、vPCCq1D-axis components and q-axis components of the rectified side alternating current bus voltage respectively; v. ofPCCd2、vPCCq2D-axis components and q-axis components of the inverter side bus voltage respectively; omega1The power grid angular frequency is output by the rectification side phase-locked loop; omega2The grid angular frequency is output by the inverter side phase-locked loop.
4. The method according to claim 1, wherein in step S3, the state space model is linearized at its equilibrium point, and the resulting small disturbance dynamic model is as follows:
Figure FDA0002377828110000052
in the model, A is a state space matrix; b is an input matrix; c is an output matrix; d is a feedforward matrix; Δ represents the amount of change in the parameter; x is a system state variable column vector; u is an input vector; y is a system output vector; when the inversion side adopts a constant voltage control mode, U is equal to [ I ]ord，Udcref]TWhen the inverter side adopts a prediction type constant turn-off angle control mode, U is equal to [ I ]ord，γ0]T，IordFor command values of constant current control, UdcrefFor a DC voltage command value, gamma, of the inverter station0For the setting of the off-angle, T represents the transpose of the matrix.
5. The method for setting the parameters of the controller applied to the hvdc transmission according to claim 1, wherein in step S4, the eigenvalue of the matrix a under different parameter values is calculated by using a control variable method, specifically as follows:
aiming at each controller parameter needing to be researched, only changing the value of the parameter based on the research range and the change step length of the parameter, keeping the values of other parameters unchanged, calculating to obtain the minimum value and the maximum value of each controller parameter, and simultaneously calculating the characteristic value of the matrix A under different values.
6. The method for tuning the parameters of the controller applied to the hvdc transmission according to claim 1, wherein in step S4, the characteristic values are screened, and the stability domain of the controller parameters is obtained according to the screened characteristic values, which is as follows:
screening the characteristic values for the first time according to the condition that the real part of the characteristic value is less than 0, and selecting the characteristic value with the real part of the characteristic value less than 0;
aiming at each screened characteristic value, calculating the damping ratio zeta of the oscillation mode corresponding to each characteristic value according to a damping ratio calculation formula:
Figure FDA0002377828110000061
in the formula, σ is the real part of the eigenvalue, and ω is the imaginary part of the eigenvalue;
according to the condition that the minimum value of the oscillation mode damping ratio is larger than the threshold value, carrying out secondary screening on the characteristic values screened out for the first time, and selecting the characteristic values of which the minimum value of the oscillation mode damping ratio is larger than the threshold value, so as to obtain a stable region of the controller parameters;
modifying the controller parameters of which the real part of the characteristic value is not less than 0 or the minimum value of the damping ratio of the oscillation mode is not more than a threshold value;
and repeating the two screening and parameter changing until all the parameters of the controller meet the condition that the real part of the characteristic value is less than 0 and the minimum value of the damping ratio of the oscillation mode is greater than a threshold value, so as to complete the optimization of the controller.
7. The method for tuning controller parameters for hvdc transmission according to claim 1, wherein in step S5, the small disturbance dynamic model of the hvdc transmission system is transformed into a transfer function model according to the transformational relational expression:
Η(s)＝C(sI-A)-1B+D；
in the formula, s is Laplace operator; h(s) is the closed-loop transfer function between the output and the output; i is an identity matrix; c is an output matrix; d is a feedforward matrix;
calculating a transfer function of a constant current controller or a constant voltage controller according to the model, wherein for the constant current controller, the input is a constant current instruction value, and the output is direct current at the rectifying side; for the constant voltage controller, the input is a constant voltage command value, and the output is an inverter-side direct-current voltage.
8. The method for tuning the controller parameter applied to the hvdc transmission according to claim 1, wherein in step S6, the overshoot and the adjustment time are calculated as follows:
let T be the time when the step response reaches the steady state value, Δ Y (T) be the response curve, and T be the sampling interval0If sampling is started from 0 moment, the steady state value is delta Y (T), and the peak value is max (delta Y (t));
defining overshoot as a percentage of the ratio of the difference between the peak and steady state values to the steady state value, the overshoot being calculated as follows:
Figure FDA0002377828110000062
defining an adjustment time tsThe minimum time required for the response to reach and remain within ± 2% of the steady state value;
obtaining optimal controller parameters according to an ITAE criterion, specifically: aiming at the controller parameter combination corresponding to the characteristic value screened out in the step S4, calculating an objective function corresponding to each group of parameters according to an objective function expression of time multiplied by absolute error integral ITAE until the calculation is traversed to the last group of parameters, and then selecting the optimal controller parameter combination;
the target function expression is specifically as follows:
Figure FDA0002377828110000063
in the formula, the upper limit of integration tsTo adjust the time; e (t) is the absolute error integral; j. the design is a squareITAEIs an objective function, JITAEThe controller parameter corresponding to the minimum value of (a) is the optimal controller parameter combination.
9. A storage medium storing a program, wherein the program, when executed by a processor, implements the controller parameter tuning method for high voltage direct current electric power transmission according to any one of claims 1 to 8.
10. A computing device comprising a processor and a memory for storing a program executable by the processor, wherein the processor, when executing the program stored by the memory, implements the method of controller parameter tuning as claimed in any one of claims 1 to 8 for application in high voltage direct current electric power transmission.
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CN112803862B (en) * 2021-01-04 2022-06-28 华北电力大学 Control method and system for direct-drive variable-speed pumped storage unit
CN112803862A (en) * 2021-01-04 2021-05-14 华北电力大学 Control method and system for direct-drive variable-speed pumped storage unit
CN112904133A (en) * 2021-02-10 2021-06-04 南方电网科学研究院有限责任公司 Step performance testing method and system of direct current control protection system
CN112904133B (en) * 2021-02-10 2022-02-25 南方电网科学研究院有限责任公司 Step performance testing method and system of direct current control protection system
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