CN109149620A - One kind is from the soft straight system control method of energy storage multiterminal and system - Google Patents
One kind is from the soft straight system control method of energy storage multiterminal and system Download PDFInfo
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Abstract
The invention discloses one kind from the soft straight system control method of energy storage multiterminal and system, using anti-pushing manipulation designing system controller, realize the stabilization of DC voltage and the quick independent control of active reactive power, constraint instructions filter is introduced simultaneously to solve the anti-differential expansion and control saturation problem for pushing away control, and design compensation signal solves the error problem of filter, introducing self adaptive control guarantees system to the robustness of uncertain parameter, and adaptive uncertain parameter is optimized using projection operator, control law based on Lyapunov Theory of Stability designing system, improve the anti-interference ability of system, realize the asymptotically stability of whole system.Simulation model has finally been built in simulation software, it is compared with traditional PID control algorithm, instruction filtering Backstepping, simulation result shows that control method of the invention has better robustness and dynamic response performance, to provide theoretical foundation and technical support from the control algolithm of the soft lineal system of energy storage multiterminal.
Description
Technical Field
The invention belongs to the technical field of flexible direct current transmission control, and particularly relates to a control method and a control system of a self-energy-storage multi-terminal flexible direct current system.
Background
In recent years, with the continuous and high-speed development of economic society, the structures of all levels of power grids are remarkably strengthened. Consequently, high-reliability power supply and high-permeability distributed energy friendly access put higher demands on the power transmission technology of the power distribution network. Back-to-Back flexible direct current (Back-to-Back VSC-HVDC) is a newly developed power grid flexible control technology, and an AC-DC-AC decoupling and interconnecting system is carried out on an alternating current system based on a Voltage Source Converter (VSC) sharing a direct current bus so as to realize long-term safe loop closing operation of any feeder line and greatly improve the power supply reliability of a power grid; PQ four-quadrant control can accurately regulate and control power flow distribution of a power grid and improve the operation economy of the power grid; the direct-current circuit link is omitted, the cost and the complexity of the control system are reduced, and the method is more suitable for the practical operation of the power distribution network. The power flow control technology represented by back-to-back flexibility is still the regulation and control of a power level, and is embodied in that an energy level is that an 'energy container' is provided on a spatial axis by a power grid, and if the adjustable capacity of an interconnection feeder line is small, the operation optimization effect of a power distribution network is limited. The energy storage is used as an 'energy container' of a time axis, the problem of simultaneity of electric energy production, transmission and consumption is essentially changed/improved, and the effect of controlling direct-current bus voltage and shifting of peak clipping and valley filling energy of a power grid can be achieved.
The self-energy-storage multi-end back-to-back flexible straight technology is uniformly applied to the energy regulation and control technologies with two different dimensions of a space axis and a time axis, the control capability of a multi-end flexible straight system can be further enhanced, and a flexible interconnected power distribution network with 'source, network, load, storage and control' is constructed. The method plays a great role in the aspects of friendly grid connection of high-permeability distributed energy, high-reliability power supply of an urban power grid and the like, and the direct-current power transmission system adopts PID control in the prior art, so that the problems of large number of controllers, difficult parameter setting, poor transient performance and the like exist. When the system is disturbed or has a fault working condition, the direct-current voltage overshoot is too large, the system response time is long, and the rapid recovery is difficult.
Disclosure of Invention
Aiming at the problems, the invention provides a control method and a control system of a self-energy-storage multi-terminal flexible direct system. A constraint instruction filter is introduced in the direct-current voltage control to solve the problem of differential expansion of the reverse control, and a filter compensation signal is designed to solve the problems of self error of the filter and input saturation of a controller. And introducing adaptive control to ensure the robustness of the system to the uncertain parameters, optimizing the adaptive uncertain parameters by using a projection operator, and proving the gradual stability of the system based on Lyapunov stability theory. Finally, simulation verifies that the projection adaptive instruction filtering backward-pushing control has good robustness and dynamic responsiveness.
The technical purpose is achieved, the technical effect is achieved, and the invention is realized through the following technical scheme:
in a first aspect, the present invention provides a self-energy-storage multi-terminal flexible-straight system control method, including:
designing an energy storage controller and a voltage source converter controller by adopting a reverse-stepping method, and respectively obtaining control laws corresponding to the energy storage controller and the voltage source converter controller;
based on self-adaptive control, respectively optimizing self-adaptive parameters in each control law by using a projection method to obtain an energy storage controller and a voltage source converter controller;
the energy storage controller outputs control parameters to an energy storage device in the self-energy-storage multi-terminal flexible-straight system to realize control over the energy storage device; and the voltage source converter controller outputs control parameters to the corresponding voltage source converter in the self-energy-storage multi-terminal flexible direct-current system to realize the control of the corresponding voltage source converter.
Further, the designing of the energy storage controller and/or the voltage source converter controller by using the back-stepping method specifically includes:
respectively designing a Lyapunov function and a virtual control law, wherein the virtual control law is used for ensuring the absolute convergence of an energy storage device or a voltage source converter in the self-energy-storage multi-terminal flexible-direct system.
Furthermore, the self-energy-storage multi-end flexible straight system is a self-energy-storage back-to-back multi-end flexible straight system,
the control method further comprises obtaining a mathematical model derived from the energy storage back-to-back multi-end soft-straight system; the mathematical model of the self-energy-storage back-to-back multi-end flexible-straight system specifically comprises the following steps:
wherein C represents a DC side capacitance, UdcWhich represents the voltage of the dc bus,represents a voltage UdcDerivative of time t, Usdi、idiRepresenting the d-axis components, U, of the AC voltage and current, respectively, of the voltage source converterbRepresenting the outlet voltage, i, of the energy storage devicebRepresenting the current at the outlet side of the energy storage device.
Further, the designing of the energy storage controller by using a back-stepping method to obtain a corresponding control law includes: designing the energy storage controller by adopting a reverse-thrust method, and firstly obtaining a virtual control quantity in the energy storage controllerComprises the following steps:
in the formula:represents a reference value of the dc bus voltage,to representFirst derivative of (k)1Represents a tunable parameter greater than 0, z1Which is representative of the voltage tracking error,Udcrepresents the dc bus voltage;
the virtual controlSystem for measuringThe control circuit is used as a command value of the inner loop controller to participate in inner loop current control.
Further, the self-energy-storage multi-terminal flexible straight system control method further comprises the following steps:
using adaptive estimatesReplacing a capacitor C in the energy storage controller;
deriving new virtual control quantities taking into account adaptive estimationComprises the following steps:
further, the control method of the self-energy-storage multi-terminal flexible straight system further includes: introducing a constraint instruction filter into the energy storage controller; the new virtual control quantityOutput signal after passing through constrained instruction filterAnd derivatives thereofThe state space expression of the constraint instruction filter is as follows:
in the formula: y is1＝xc，δ＝xd，xdAs an input quantity, xcIn order to be an output quantity,derivative of the output quantity, ξ damping of the command filter, ωnIs the bandwidth, SR(. and S)M(. cndot.) represents rate and amplitude constraints, respectively;
designing a compensation signal to compensate the error of the constraint instruction filter, wherein the calculation formula of the compensation signal is as follows:
in the formula: epsilon is a compensation signal which is used as a compensation signal,to compensate for the derivative of the signal, k1Represents an adjustable parameter greater than 0 and,is the energy storage current reference value.
Further, the self-energy-storage multi-terminal flexible straight system control method further comprises the following steps: based on And a positive definite Lyapunov functionThe control law of the energy storage controller obtained by adopting a reverse-deducing method is as follows:
in the formula of UrbRepresenting the bridge arm side voltage, k, of the energy storage device1、k2Is an adjustment parameter greater than 0 and,is the derivative of the energy storage current reference value;Lbrepresenting the inductance, R, at the outlet side of the energy storage devicebRepresenting the resistance at the outlet side of the energy storage device, and respectively replacing the resistance R and the inductance L in the energy storage controller; z is a radical of2Representing the current tracking error of the energy storage device,the calculation formula of (2) is as follows:
wherein,in order to adapt the error of the estimated value,e1for adaptive estimation of valuesTo the reference value of (c).
Further, the self-adaptation law of the uncertain parameters obtained by optimizing the self-adaptation estimation value in the control law of the energy storage controller by using the projection method specifically comprises the following steps:
in the formula: proj (,) is a projection operator, γ1、γ2、γ3Is an error coefficient.
Further, an adaptive estimate is defined asL1Representing the equivalent inductance, R, of the network side1Representing the equivalent resistance of the power grid side, and the error of the estimated value ise4And e5Are respectively adaptive estimated valuesAnda positive definite Lyapunov function ofDesigning a voltage source converter controller by adopting a reverse-stepping method to obtain a control law in the voltage source converter controller as follows:
in the formula: u shaperd1、Urq1Are respectively a voltage source converterComponent of the AC side outlet voltage vector d-axis and q-axis, k3、k4Is an adjustable parameter greater than 0, id1、iq1The components of current vectors on the AC side of the voltage source converter, i.e. d-axis and q-axis, omega1Is the grid angular frequency;is a reference quantity of a d-axis component of a current vector on an alternating current side of the voltage source converter,is composed ofThe first derivative of (a);is a reference quantity of a q-axis component of a current vector on an alternating current side of the voltage source converter,is composed ofThe first derivative of (a); u shapesd1、Usq1The components of the voltage vector d-axis and q-axis of the grid side of the voltage source converter are respectively.
Further, using projection method to self-adapt estimation value of control law in voltage source converter controllerOptimizing to obtain the self-adaptive law of uncertain parameters as follows:
wherein Proj (,) is a projection operator, γ4、γ5Is an error coefficient.
In a second aspect, the present invention provides a self-energy-storage multi-end back-to-back flexible direct system control system, including:
the control law acquisition module of the controller is used for designing the energy storage controller and the voltage source converter controller by adopting a reverse-stepping method to acquire corresponding control laws;
a self-adaptive parameter optimization module; and the method is used for optimizing the adaptive parameters in each control law by using a projection method based on adaptive control to obtain an energy storage controller and a voltage source converter controller. Compared with the prior art, the invention has the beneficial effects that:
the invention provides a self-energy-storage multi-terminal flexible direct system control method and a system, firstly, the whole system is decomposed into a plurality of subsystems, and the subsystems are energy storage devices or voltage source converters; and then designing controllers of the subsystems respectively by adopting a reverse-thrust method. Because the direct-current voltage control introduces a constraint instruction filter to solve the differential expansion problem of the reverse control, a filter compensation signal is designed to solve the problems of the error of the constraint instruction filter and the input saturation of a controller; adaptive control is introduced to ensure the robustness of the self-energy-storage multi-terminal flexible-straight system to uncertain parameters, a projection operator is used for optimizing the self-adaptive uncertain parameters, and the gradual stability of the self-energy-storage multi-terminal flexible-straight system is proved based on Lyapunov stability theory. Finally, simulation verifies that the control method (namely projection adaptive instruction filtering backstepping control) of the invention has good robustness and dynamic responsiveness.
Drawings
FIG. 1 is a schematic diagram of the SES-MBTB system according to an embodiment of the present invention;
FIG. 2 is a schematic view of a topology of an energy storage device according to an embodiment of the invention;
fig. 3 is a schematic diagram of a VSC topology according to an embodiment of the present invention;
FIG. 4 is a system control block diagram of one embodiment of the present invention;
FIG. 5 is a schematic diagram of a constrained instruction filter according to an embodiment of the present invention;
FIG. 6 is a diagram comparing PID and PACBC control according to an embodiment of the present invention;
FIG. 7 is a comparison of CBC and PACBC control according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
The main conception of the invention is as follows:
(1) establishing a non-linear mathematical model of a self-energy-storage multi-terminal flexible-straight system;
(2) decomposing the self-energy-storage multi-terminal flexible direct system into a plurality of subsystems, wherein the subsystems are energy storage devices or voltage source converters;
(3) respectively designing each subsystem controller by adopting a reverse-thrust method; the port of the voltage source converter adopts constant power control; the energy storage device is controlled by direct current voltage, a constraint instruction filter is introduced into the direct current voltage control to solve the problem of differential expansion of reverse control, and a filter compensation signal is designed to solve the problems of self error of the filter and input saturation of a controller; furthermore, adaptive control is introduced to ensure the robustness of the system to uncertain parameters, a projection operator is used for optimizing the adaptive uncertain parameters, and the gradual stability of the self-energy-storage multi-terminal flexible-straight system is proved based on Lyapunov stability theory.
(4) Simulation verifies that the projection adaptive instruction filtering reverse-thrust control has good robustness and dynamic responsiveness.
Example 1
In the embodiment of the present invention, the self-energy-storage multi-terminal back-to-back flexible-straight system is taken as an example to describe the control method of the present invention.
Step one, establishing a non-linear mathematical model of a self-energy-storage multi-end back-to-back flexible straight system (SES-MBTB)
The self-energy-storage multi-end back-to-back flexible direct-current system in the prior art has three wiring modes of series connection, parallel connection and series-parallel connection, and the self-energy-storage multi-end back-to-back flexible direct-current system provided by the embodiment of the invention adopts a parallel connection mode, so that a direct-current circuit link is omitted. The energy storage device is internally provided with a DC/DC converter, the DC/DC converter is shared with the direct current sides of all voltage source converters, the stability of the direct current side voltage of the flexible direct current system is facilitated, the control is simple and flexible, the expansion is easy, and the five-port SES-MBTB device has the structural topology shown in figure 1.
The self-energy-storage back-to-back flexible-direct system is composed of a 4-terminal voltage source converter and a 1-terminal energy storage device, and under a normal operation state, the energy storage device is used as a relaxation node and is controlled by constant direct-current voltage, and meanwhile, the active power balance of the system is realized; the alternating current side of the voltage source converter is respectively connected with each feeder line of the power distribution network, flexible interconnection (alternating current-direct current-alternating current decoupling) among the plurality of feeder lines is achieved, and the voltage source converter is controlled by constant power. In the SES-MBTB system provided by the embodiment of the invention, the energy storage device is additionally arranged and has the energy timing sequence regulation capacity, so that the whole flexible-straight system becomes a highly integrated comprehensive energy conversion device.
The energy storage device takes charging as a positive direction, the topological structure of the energy storage device is shown in fig. 2, and the mathematical model of the energy storage device obtained from fig. 2 is as follows:
in the formula, LbIs an equivalent impedance, ibFor the current to flow on the outlet side of the energy storage device,represents the current ibDerivative with respect to time t, RbIs an equivalent resistance, UbFor the outlet voltage of the energy storage device, UrbFor bridge arm side voltage, U, of the energy storage devicerb＝dUdcWherein d is the duty cycle, UdcIs the dc bus voltage.
The voltage source converter takes the power injected into the alternating current network as the positive direction, the topological structure of the voltage source converter is shown in fig. 3, and the mathematical model of the voltage source converter obtained from fig. 3 is as follows:
wherein L is an equivalent reactance of the AC side reactor, iiIs the current of the power grid at the alternating current side,represents the current iiDerivative to time t, R is equivalent resistance of AC side reactor, UriIs the AC side voltage value, U, of the voltage source convertersiIs the ac side grid voltage.
When equation (2) is converted into dq synchronous rotating coordinate system, taking a voltage source converter as an example, for a voltage source converter outputting power (i.e. the voltage source converter outputs power), the mathematical model is as follows:
in the formula,respectively represent the current id1、iq1Derivative with respect to time t, id1、iq1The components of the grid-side current vectors d-axis and q-axis of the voltage source converter, omega1For grid angular frequency, Usd1、Usq1Components of the grid-side voltage vectors d-and q-axis, U, of the voltage source converterrd1、Urq1Components of d-and q-axes, L, respectively, of the outlet voltage vector at the AC side of the voltage source converter1Representing a grid-side equivalent inductance value; r1Representing the grid side equivalent resistance value.
For a voltage source converter of the absorption power type, the current is reversed.
The alternating current outlet reactor of the voltage source converter mainly plays a role in current limiting and filtering, the actual reactor is weak resistance, the resistance R is very small, the loss is negligible, and the active power and the reactive power of the voltage source converter under the steady-state condition can be represented as follows:
the d-axis is located in the direction of the grid voltage vector by the phase-locked loop, so that Usq1＝0，Usd1＝Us，UsRepresenting the grid voltage, equation (4) can be expressed as:
from equation (5), it can be seen that the active power and the reactive power can be controlled independently by controlling the dq-axis component of the voltage source converter current. Disregard the transverter loss, the alternating current-direct current both ends power from the gentle straight system of energy storage multiterminal equals, consequently, obtains from the mathematical model of the gentle straight system of energy storage multiterminal back-to-back and is:
wherein C is a DC side capacitor of a self-energy-storage multi-terminal back-to-back flexible direct-current system, UdcIs the DC bus voltage of the self-energy-storage multi-end back-to-back flexible-to-direct system,represents a voltage UdcDerivative of time t, Usdi、idiRepresenting the d-axis component, U, of the AC voltage and current of the voltage source converterbFor the voltage at the outlet side of the energy storage device, ibIs the current on the outlet side of the energy storage device.
As can be seen from the equation (6), the DC voltage can be maintained stable by controlling the current, and the DC voltage is kept constant in the steady-state operation modeSince the incoming power at each port (i.e., the tank port and the limp-dc port) is equal to the outgoing power, the dc voltage must be kept stable for smooth transmission of active power from the tank multi-port limp-dc system. When the power is unbalanced, the direct current voltage fluctuates, the energy storage device of the fixed direct current voltage is a power balance point, the charging and discharging characteristics of the energy storage device can balance the system power, and the influence of the power unbalance on the direct current voltage is weakened.
Designing an energy storage controller and a voltage source converter controller by adopting a reverse-stepping method, wherein in other embodiments of the invention, the energy storage controller or the voltage source converter controller can be designed by only utilizing the reverse-stepping method in the invention;
because the direct current voltage can fluctuate even exceed the limit when the power fluctuates, the embodiment of the invention applies a reverse-deducing method to the design of the controller, adds a constraint instruction filter to the constant direct current voltage control to solve the differential expansion and constraint problems of the reverse-deducing control, designs a compensation signal to solve the error problem of the filter, and introduces an adaptive projection operator to uncertain parameters in the self-energy-storage multi-terminal flexible direct current system to ensure the boundedness of an estimated value.
Firstly, decomposing a complete self-energy-storage multi-terminal flexible straight system into a plurality of subsystems, wherein the subsystems are energy storage devices or voltage source converters;
then, a Lyapunov function and a virtual control law are designed in each subsystem, and finally, a complete control system is obtained through reverse estimation, wherein the virtual control law is used for ensuring the absolute convergence of the subsystems, the self-energy-storage multi-terminal flexible-straight system obtains expected rapid tracking performance and better stability, and the overall control block diagram of the self-energy-storage multi-terminal flexible-straight system is shown in fig. 4.
The specific design of the energy storage controller is as follows:
defining voltage and current tracking error:
in the formula of UdcIs a voltage of the direct-current bus,is a DC bus reference value, ibFor the outlet-side current of the energy storage means,for the outlet-side current reference of the energy storage device, the derivative of the voltage tracking error can be expressed as:
setting the first positive definite Lyapunov function as:
derivation of equation (10) yields:
in the formula, k1Is an adjustable parameter greater than 0, andobtaining a virtual control quantityComprises the following steps:
by substituting formula (12) for formula (11)Therefore, the method conforms to the Lyapunov function control law.
Fourth, in the actual control system, since the capacitance C, the resistance R, and the inductance L cannot obtain accurate values, the adaptive estimation value is used in the embodiment of the present inventionMake a substitution wherein LbRepresenting the inductance, R, at the outlet side of the energy storage devicebRepresenting the resistance at the outlet side of the energy storage device, respectively replacing the resistance R and the inductance L in the energy storage controller, and defining the error of the self-adaptive estimation value ase1、e2And e3Are respectively asAndso equation (12) can be rewritten as:
the fifth step: a constraint instruction filter is introduced to solve the problems of differential expansion and control saturation of reverse control, and a compensation signal is designed to solve the error problem of the filter;
to obtain the output signal, the derivation of the virtual control quantity is required, which not only increases the complexity of the system, but also increases the influence of measurement noise. Constrained command filters may be used to solve differential expansion and control saturation problems for the reverse control. The basic idea is as follows: will control the quantity virtuallyObtaining a filtered output signal by a second order constraint filterAnd derivatives thereofThe filter structure is shown in FIG. 5, xdFor input, ξ damping of the command filter, ωnIs the bandwidth, xcIn order to be an output quantity,as a derivative of the output quantity,the integral process is represented, and the derivation process of the virtual control quantity is obtained in the constraint instruction filter through the integral process, so that direct derivation of the virtual control quantity is avoided. The state space expression of the constraint instruction filter is expressed as:
in the formula, y1＝xc，δ＝xdξ is damping of the command filter, ωnIs the bandwidth, SR(. and S)MRepresenting the rate and amplitude constraints, respectively, there must be an error x when the amplitude and rate of the virtual control quantity are greater than the maximum value that the system can toleratec-xdBy counting the bandwidth omeganTo adjust the virtual control signal xdConvergence can be faster and more accurate. OmeganAccording to the input signal xdThe frequency range of (a) is selected to be a reasonable value when ω isnIs much larger than the input signal xdFrequency of (2), input signal xdThe filter can pass through without attenuation, and the influence of high-frequency noise is greatly reduced.
When the gentle straight system can not track actual setting value, can cause the error accumulation, reduce gentle straight system's dynamic response performance, lead to gentle straight system to disperse even, consequently, need consider the influence of restraint instruction filter error in the controller design, redefine the voltage tracking error and be:
the compensation signal is designed as:
in the formula: epsilon is a compensation signal which is used as a compensation signal,to compensate for the derivative of the signal, k1Represents an adjustable parameter greater than 0 and,is the energy storage current reference value.
(6) Introducing adaptive control to ensure the robustness of the system to uncertain parameters, and optimizing the adaptive control by using a parameter projection method, which specifically comprises the following steps:
according to the formulae (6), (13) and (16):
the derivative of the current tracking error, which can be obtained from equations (1) and (8), is:
setting a second positive definite Lyapunov function as:
in the formula, gamma1、γ2、γ3For the error coefficient, the derivation is performed on equation (19):
wherein k is1、k2For an adjustment parameter greater than 0, the control law is calculated by equation (20):
the adaptive parameters in the control law in equation (21) are optimized by using a parameter projection method, and the adaptive law of the adaptive parameters is obtained by:
in the formula, Proj (,) is a projection operator.
Compared with the traditional controller, the controller of the invention simplifies the program, reduces the operation amount, can obtain better stability and dynamic tracking effect, and is more suitable for engineering application.
In the embodiment of the invention, the voltage source converter adopts constant power control, takes VSC1 as an example, and defines the self-adaptive estimated valueAdaptive estimate error ofe4And e5Are respectively asAndthe VSC1 controller design process is given below:
(1) define VSC1 current tracking error:
in the formula,for the current reference, the derivative of the tracking error can be expressed as:
(2) setting a third positive definite Lyapunov function as:
in the formula, gamma4、γ5Is an error coefficient;
(3) derivation of equation (27) yields:
wherein k is3、k4For the adjustable parameter larger than 0, the control law is calculated by the formula (28):
optimizing adaptive parameters in a control law in a voltage source converter controller by using a parameter projection method to obtain the adaptive law of the adaptive parameters as follows:
the voltage source converter controllers of the remaining VSCs are all of the same design as the voltage source converter controller of the VSC1 and will not be described further here.
The following analysis of the stability of the energy storage controller, the projection operator is defined as follows:
whereinIs an estimate of the value of theta and,is composed ofX is a determined adaptive function, and the two important properties of the projection operator are:
properties 1
Properties 2
ΩθTo define a constraint set, from property 1:
from property 2, the adaptive function can make the projection operator correctThe boundedness of the uncertain parameters is guaranteed.
This is obtained according to equations (20), (21) and (33):
from the formula (19), V2As a positive definite function, from the formula (34)For a negative constant function, for the energy storage controller V2≥0、Therefore, according to the Lyapunov stability theory, the control quantity U isrbUnder the action of (3), the energy storage device can be finally gradually stabilized, and can obtain V through the same principle3≥0、VSC1 is controlled by quantity Urd1、Urq1Finally, the stability of the whole self-energy-storage multi-terminal flexible-straight system meets the stability condition.
Example 2
In order to verify the feasibility and the effectiveness of the control algorithm provided by the invention, a five-terminal SES-MBTB system simulation model shown in FIG. 1 is built based on Matlab/Simulink.
The parameter settings of the simulation model are shown in table 1:
TABLE 1 simulation parameters
Table 2 shows active power changes of VSC1, VSC2, VSC3, and VSC4 in different periods, and the simulation is performed under the conventional PID control algorithm and the projection adaptive command filter reverse-thrust control (PACBC) algorithm of the present invention, respectively, and the simulation results are compared.
TABLE 2 simulation conditions
As shown in fig. 6, a comparison graph of PID control and PACBC effect is shown, in fig. 6, (a), (c), (e) are graphs of PID control effect of controlling the active power, dc bus voltage and ac side current harmonic distortion (THD) of each converter station, and in fig. 6, (b), (d), (f) are graphs of PACBC converter active power, dc bus voltage and ac side current THD control effect. Due to actual loss, each converter cannot send power according to the instruction value completely, the power values in fig. 6 slightly fluctuate near the instruction value, and the energy storage device makes up for power shortage through charging and discharging. The VSC1 power was changed 4MW by the 2MW sudden change during 0.4s, and energy memory is for keeping the system power balance 2MW offset power shortage that fluctuates down, and VSC2 power was changed 1MW by the 3MW sudden change during 0.6s, and energy memory takes place the action, and power is increased to 0 by-2 MW, has effectively balanced system power. As can be seen from FIG. 6, PACBC has better power tracking performance and dynamic response capability and less power fluctuation than PID control. The direct-current bus voltage of the self-energy-storage multi-terminal flexible direct-current system fluctuates at two moments of 0.4s and 0.6s due to power change, and as can be seen from fig. 6, the PACBC voltage overshoot is obviously smaller than that of PID control, and the tracking error is smaller. The alternating-current side current THD of the VSC is controlled by the PID to be 5.38%, the standard of national standard 5% is not reached, the alternating-current side current THD of the PACBC algorithm reaches 1.50%, and a good control effect is obtained.
The dc side capacitance acts to maintain the bus voltage,it is difficult to obtain accurate values in engineering applications. In order to verify the robustness of PACBC to uncertain parameters, the capacitance C at the direct current side is increased to twice of the original capacitance C, simulation is respectively carried out under the instruction filtering reverse-thrust control (CBC) and the PACBC algorithm, and direct-current voltage error z is corrected1And (6) carrying out analysis. FIG. 7(a) is a graph of CBC voltage error simulation results for different capacitance parameters, and FIG. 7(b) is a graph of PACBC voltage error simulation results for different capacitance parameters.
As can be seen from the graph in FIG. 7(a), the DC voltage has larger errors in steady state and disturbance under different capacitance parameters, which indicates that the CBC is more sensitive to the parameters, and the change of the capacitance parameters in the graph in FIG. 7(b) has smaller influence on the voltage, so that the PACBC has better robustness to uncertain parameters than the CBC algorithm and is more suitable for engineering application.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application 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 application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. A control method of a self-energy-storage multi-terminal flexible-straight system is characterized by comprising the following steps:
designing an energy storage controller and a voltage source converter controller by adopting a reverse-stepping method, and respectively obtaining control laws corresponding to the energy storage controller and the voltage source converter controller;
based on self-adaptive control, respectively optimizing self-adaptive parameters in each control law by using a projection method to obtain an energy storage controller and a voltage source converter controller;
the energy storage controller outputs control parameters to an energy storage device in the self-energy-storage multi-terminal flexible-straight system to realize control over the energy storage device; and the voltage source converter controller outputs control parameters to the corresponding voltage source converter in the self-energy-storage multi-terminal flexible direct-current system to realize the control of the corresponding voltage source converter.
2. The self-energy-storage multi-terminal flexible direct system control method according to claim 1, wherein: the design of the energy storage controller and the voltage source converter controller by adopting a reverse-thrust method specifically comprises the following steps:
respectively designing a Lyapunov function and a virtual control law, wherein the virtual control law is used for ensuring the absolute convergence of an energy storage device and a voltage source converter in the self-energy-storage multi-terminal flexible-direct system.
3. The self-energy-storage multi-terminal flexible direct system control method according to claim 1, wherein: the self-energy-storage multi-end flexible straight system is a self-energy-storage back-to-back multi-end flexible straight system,
the control method further comprises obtaining a mathematical model derived from the energy storage back-to-back multi-end soft-straight system; the mathematical model of the self-energy-storage back-to-back multi-end flexible-straight system specifically comprises the following steps:
wherein C represents a DC side capacitance, UdcWhich represents the voltage of the dc bus,represents a voltage UdcDerivative of time t, Usdi、idiRepresenting the d-axis components, U, of the AC voltage and current, respectively, of the voltage source converterbRepresenting the outlet voltage, i, of the energy storage devicebRepresenting the current at the outlet side of the energy storage device.
4. A self-storing multi-terminal soft straight system control method as claimed in any one of claims 1-3, which isIs characterized in that: the method for designing the energy storage controller by adopting a reverse-thrust method to obtain a corresponding control law comprises the following steps: designing the energy storage controller by adopting a reverse-thrust method, and firstly obtaining a virtual control quantity in the energy storage controllerComprises the following steps:
in the formula:represents a reference value of the dc bus voltage,to representFirst derivative of (k)1Represents a tunable parameter greater than 0, z1Which is representative of the voltage tracking error,Udcrepresents the dc bus voltage;
the virtual control quantityThe control circuit is used as a command value of the inner loop controller to participate in inner loop current control.
5. The self-energy-storage multi-terminal flexible direct system control method according to claim 4, wherein: further comprising:
using adaptive estimatesReplacing a capacitor C in the energy storage controller;
deriving new virtual control quantities taking into account adaptive estimationComprises the following steps:
6. the self-energy-storage multi-terminal flexible straight system control method according to claim 5, further comprising: introducing a constraint instruction filter into the energy storage controller; the new virtual control quantityOutput signal after passing through constrained instruction filterAnd derivatives thereofThe state space expression of the constraint instruction filter is as follows:
in the formula: y is1＝xc，δ＝xd，xdAs an input quantity, xcIn order to be an output quantity,derivative of the output quantity, ξ damping of the command filter, ωnIs the bandwidth, SR(. and S)M(. cndot.) represents rate and amplitude constraints, respectively;
designing a compensation signal to compensate the error of the constraint instruction filter, wherein the calculation formula of the compensation signal is as follows:
in the formula: epsilon is a compensation signal which is used as a compensation signal,to compensate for the derivative of the signal, k1Represents an adjustable parameter greater than 0 and,is the energy storage current reference value.
7. The self-energy-storage multi-terminal flexible direct system control method according to claim 6, further comprising: based onAnd a positive definite Lyapunov functionThe control law of the energy storage controller obtained by adopting a reverse-deducing method is as follows:
in the formula of UrbRepresenting the bridge arm side voltage, k, of the energy storage device1、k2Is an adjustment parameter greater than 0 and,is the derivative of the energy storage current reference value;Lbrepresenting the inductance, R, at the outlet side of the energy storage devicebIndicating the resistance at the outlet side of the energy storage device, minThe energy storage controller is used for replacing a resistor R and an inductor L in the energy storage controller; z is a radical of2Representing the current tracking error of the energy storage device, the calculation formula of (2) is as follows:
wherein,in order to adapt the error of the estimated value,e1for adaptive estimation of valuesTo the reference value of (c).
8. The method as claimed in claim 6, wherein the method comprises the steps of: the method for optimizing the self-adaptive estimated value in the control law of the energy storage controller by using the projection method to obtain the self-adaptive law of the uncertain parameters comprises the following steps:
in the formula: proj (,) is a projection operator, γ1、γ2、γ3Is an error coefficient.
9. A self-energy-storage multi-terminal back-to-back flexible straight system control method according to any one of claims 1-3, characterized in that: defining the adaptive estimate asL1Representing the equivalent inductance, R, of the network side1Representing the equivalent resistance of the power grid side, and the error of the estimated value ise4And e5Are respectively adaptive estimated valuesAnda positive definite Lyapunov function ofDesigning a voltage source converter controller by adopting a reverse-stepping method to obtain a control law in the voltage source converter controller as follows:
in the formula: u shaperd1、Urq1Components of d-and q-axes, k, respectively, of the outlet voltage vector at the AC side of the voltage source converter3、k4Is an adjustable parameter greater than 0, id1、iq1Current vectors d-and q-axis on the ac side of the voltage source converter, respectivelyComponent, ω1Is the grid angular frequency; is a reference quantity of a d-axis component of a current vector on an alternating current side of the voltage source converter,is composed ofThe first derivative of (a); is a reference quantity of a q-axis component of a current vector on an alternating current side of the voltage source converter,is composed ofThe first derivative of (a); u shapesd1、Usq1The components of the voltage vector d-axis and q-axis of the grid side of the voltage source converter are respectively.
10. The method of claim 9, wherein the method further comprises: adaptive estimation in control law in voltage source converter controller using projection methodOptimizing to obtain the self-adaptive law of uncertain parameters as follows:
wherein Proj (,) is a projection operator, γ4、γ5Is an error coefficient.
11. The utility model provides a from gentle straight system control system in energy storage multiterminal back-to-back which characterized in that includes:
the control law acquisition module of the controller is used for designing the energy storage controller and the voltage source converter controller by adopting a reverse-stepping method to acquire corresponding control laws;
a self-adaptive parameter optimization module; and the method is used for optimizing the adaptive parameters of each control law by using a projection method based on adaptive control to obtain an energy storage controller and a voltage source converter controller.
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