CN115579951A - Distributed cooperative stability control method for multi-inverter new energy power station - Google Patents
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- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- 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
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- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02M1/00—Details of apparatus for conversion
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- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
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- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
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Abstract
The invention discloses a distributed cooperative stability control method for a multi-inverter new energy power station, and belongs to the field of electrical engineering. Aiming at the problems that the control performance of the inverter is reduced and even the system becomes unstable due to uncertain conditions such as random plug and play of the inverter, impedance fluctuation of a power grid and the like, the invention designs a nonlinear observer based on a port controlled Hamilton structure, and solves the problems of parameter perturbation, unmodeled errors, uncertain factors such as plug and play of the inverter and the like and the reduction of the passive control performance of a nonlinear change band while still meeting the passivity and stability conditions after the observer is introduced; and self-adaptive dynamic damping control based on power grid impedance identification is adopted, and damping is set according to a predefined nonlinear curve, so that the overall dynamic performance of the multi-inverter power station is ensured, and communication is not needed. The method is simple to implement, realizes the distributed cooperative stable control of the multi-inverter power station, and improves the power grid adaptability of the multi-inverter power station.
Description
Technical Field
The invention relates to the field of electrical engineering, in particular to a distributed cooperative stable control method and device for a multi-inverter new energy power station and the new energy power station.
Background
Renewable energy is vigorously developed, greenhouse gas emission is reduced, and the construction of environment-friendly countries has very important significance on national energy safety, environmental improvement, economic sustainable development and the like of China. Renewable energy power generation such as wind power generation and photovoltaic power generation is used as a power generation mode with the greatest large-scale development and application prospect, and the technology is mature day by day and is gradually widely applied. However, with the increasing installed capacity of the wind power, photovoltaic and other renewable energy grid-connected power generation systems, on one hand, at the power supply side, due to uncertainty of wind and light, the inverter has a plug-and-play operating characteristic, and the structure/parameters of the power grid change nonlinearly; on the other hand, on the power grid side, because the new energy power station is generally built at the end of the power grid, parameters such as power grid impedance and voltage present a large fluctuation characteristic, and great challenges are brought to the control performance of a new energy grid-connected system. One of the challenges is that the proportional-integral controller designed based on the linear theory in the conventional grid-connected inverter control has good stability for a given power grid structure/parameter, and once the proportional-integral controller is applied to uncertain scenes such as nonlinear change of power grid characteristics, the problem of small-signal stability caused by insufficient adaptability is expressed as broadband oscillation of electric quantities such as voltage/current in a power grid. Research has shown that: when multiple machines are connected and the characteristics of the power grid change, the interaction between the power electronic equipment and the power grid is the main cause of broadband oscillation.
Active dampers are an effective way to suppress broadband oscillations and are typically installed at the point of common coupling in multi-inverter power plants. Its capacity is determined by the size of the power plant, which is very large. Therefore, the cost of this solution is high. Another approach is to design appropriate stability control techniques for each inverter to provide additional oscillation damping, such as active damping and virtual impedance techniques. However, this design is more efficient in predetermined grids with fixed structures and parameters. Due to uncertain conditions such as random plug and play of the inverter, power grid impedance fluctuation and the like, the control performance of the inverter is deteriorated, and even a system becomes unstable.
Passive control of grid-connected inverters is another technology that can provide stability control for multi-inverter plants, taking into account the design and energy remodeling of the controller. When a plurality of subsystems which are controlled and designed based on the passivity theory are connected in parallel to form a large system, the passivity of the large system can be utilized to ensure the stability of the whole system. Thus, many such parallel grid-tied inverters will remain passive and stable as long as the controller of the single inverter is designed by passivity theory.
At present, aiming at a stability control method of a grid-connected inverter based on passivity, both academic papers have made deep theoretical analysis on the stability control method and engineering methods applied practically, such as:
1) Zeng Zheng and Yang Huan et al published in 2012 "grid technology" at volume 36, phase 4 in the text "LC filtering grid-connected inverter control based on passive Hamilton system theory". The scheme provides a reference current generation algorithm from the viewpoint of system passivity, and has static and dynamic response capabilities and harmonic suppression capabilities.
2) Lemin and Xuqu issue are listed in the text of LCL filtering grid-connected inverter control based on IDA-PBC on No. 26, no. 4 of the 2014 electric power system and its automatic chemical newspaper. The article provides a port controlled dissipation Hamilton mathematical model of an LCL filtering three-phase grid-connected inverter, and then provides a passive control strategy based on interconnection and damping configuration, so that the gradual stability of a closed-loop system is guaranteed theoretically.
3) Huangmin, chenfan et al are published in "Passive control strategy for grid-connected inverter without phase-locked loop under Weak current grid" on 26 rd 3 of the journal of Motor and control of 2022. Aiming at a weak power grid scene under high power grid impedance, the passive controller without the phase-locked loop is adopted, and the passive controller has better stability and anti-interference capability.
4) In the 'passive quasi-PR control method of the photovoltaic grid-connected inverter under the weak grid', published in 30.6.2020 of Chinese patent document CN 111355257A, the change rate of an error energy storage equation of an inverter system is obtained by analyzing the energy relation of a single-phase full-bridge inverter under the weak grid, so that the change rate of the error energy storage equation is adjusted through damping parameters, and the passive control is realized.
5) "Liu Guihua, wang Wenxiu, zhu Xiaohui, wang Wei, improved past-based control method of grid-connected PV inverter in the grids" published in the 21 st International Motor and System Conference in 2018,11 (8): 2144. the document provides an improved passive control method based on a quasi-PR control method, and the improved passive control method is suitable for a high-grid-impedance scene.
However, such methods suffer from the following disadvantages: the passive control is a model-based scheme, is designed for a given grid-connected inverter and a power grid structure/parameter, and depends heavily on an accurate system mathematical model. Considering that perturbation of parameters of a main circuit filter of grid-connected inverter hardware during actual operation, line and switch loss and even sensor measurement errors are uncertain parameters which are often difficult to accurately know in practice and can change along with time; moreover, as the grid size becomes larger and the grid structure becomes more complex, and the plug and play of the devices leads to the grid structure/parameters also presenting non-linear variations and uncertainties, it is also difficult to model accurately. The existing passive control scheme usually assumes that a power grid is a single-machine infinite system, and the parameters and the structure of a grid-connected object cannot be changed. Thus, uncertainty in model parameters, external disturbances, and structural changes in the controlled object may degrade its performance. In order to solve the problems of parameter uncertainty and disturbance, a method for improving passive control of a three-phase grid-connected inverter based on disturbance observer compensation, which is disclosed by CN 109004669B in 2018, 12, and 14, proposes that the disturbance observer is used for output compensation, so that the influence of uncertain factors such as parameter perturbation, unmodeled errors, disturbance and the like on steady/dynamic response characteristics is suppressed, and the robustness of a passive controller is improved. However, the non-linear state observer provided by the invention is an additionally introduced link, and cannot guarantee whether the passivity and the stability of the system can still be guaranteed after the passive controller is introduced. Similarly, chinese patent document CN108021719A, "a passive control method for grid connection of wind farm", published in 5, month and 11 of 2018, proposes that a passive control method using integral compensation is used to eliminate a steady-state error caused when large interference or inaccurate parameters occur. However, the integrator link is introduced in the scheme, which will cause the dynamic response characteristic of the inverter to deteriorate, and the problem also exists whether the passivity and stability of the system can still be ensured after the integrator is introduced into the passive controller.
In addition to the problem that the control performance of the inverter will be deteriorated due to the uncertainty of random plug and play of the inverter, power grid impedance fluctuation and the like, the existing passive control scheme has the problem of coordinating the dynamic performance of a plurality of inverters once being extended from a single inverter to a multi-inverter power station. In consideration of the plug and play characteristic of the inverter, the guarantee of the system-level oscillation damping characteristic of the multi-inverter power station is very important. Since it is difficult to guarantee the dynamic performance of the whole plant even if the single inverter has perfect damping characteristics. In this case, mutual cooperation between the inverters is necessary.
At present, for a technology for realizing cooperative control among multiple inverters based on an passivity grid-connected inverter, the technology can be realized through communication among the multiple inverters, but the performance of the technology is limited by communication bandwidth. For example, "y.han, h.li, p.shen, e.a.a.coelho, and j.m.guerrero," Review of active and reactive power sharing strategies in hierarchical controlled grids, "IEEE trans.power electronics, vol.32, no.3, pp.2427-2451, mar.2016" ("Review of active and reactive power sharing strategies for hierarchical controlled micro-grids") published in the IEEE power electronics collection, month 4, 2016, which suggests that existing cooperative control is typically applied under slow dynamic requirements, such as power scheduling between multiple inverters, and for applications of fast oscillation damping, communication-based cooperative control is difficult to work because the required bandwidth is too high. The other method of cooperative control is to directly use local measurement information, set a cooperative rule in advance, realize mutual cooperation among a plurality of inverters, and exhibit a distributed control characteristic, which is called distributed cooperative control. For example, "t.lee and p.cheng," Design of a new cooperative harmonic filtering strategy for distributed generation interface converters in an island network, "IEEE trans.power electronics, vol.22, no.5, pp.1919-1927, sep.2007" published in the IEEE 9 th university of electricity and electronics, 2007, the document proposes to establish a droop relationship between the harmonic conductance command and the harmonic reactive power consumption of each inverter to share the harmonic filtering capability without communication. However, this method is still a linear solution in nature, and it is also difficult to provide satisfactory performance when the number of parallel inverters varies randomly in the case of nonlinear plug and play, and there is a problem of suppressing nonlinear wide-band oscillation failure.
In summary, the prior art has the following problems:
(1) When multiple machines are connected and the characteristics of a power grid change, broadband oscillation is caused by interaction among power electronic equipment and between the power electronic equipment and the power grid, and the active damper, the active damping and the virtual impedance technology proposed by the existing scheme are designed aiming at the structure or parameters of a fixed power grid, so that uncertain conditions such as random plug and play of an inverter, power grid impedance fluctuation and the like cannot be coped with;
(2) The inverter passive control scheme proposed by the existing literature depends on accurately known model parameters such as an inverter filter and the like, and the inverter control performance is reduced under the conditions of plug and play of a weak grid-connected multi-inverter system and nonlinear change of grid characteristics on the assumption that a power grid is in a given structure and parameters. For this reason, the existing documents propose to introduce a disturbance observer and an integrator to compensate the uncertainty of the parameters of passive control, but the existing documents cannot guarantee whether the passivity and the stability of the system can still be guaranteed after the additionally introduced disturbance observer and the integrator are introduced into the passive controller;
(3) The communication-based multi-inverter cooperative control proposed by the existing literature is applied to rapid oscillation damping, and the required bandwidth is too high, so that the communication-based multi-inverter cooperative control is difficult to play a role; the existing distributed cooperative control is still a linear scheme in nature, when the number of the parallel inverters is randomly changed under the condition of nonlinear plug and play, satisfactory performance is difficult to provide, and the problem of nonlinear broadband oscillation failure suppression exists.
(4) The existing literature schemes do not design a nonlinear observer based on a port-controlled Hamilton structure, and solve the problems of uncertain factors such as parameter perturbation, unmodeled errors, inverter plug and play and the like and the reduction of the passive control performance of a nonlinear change band while still meeting the passivity and stability conditions after the observer is introduced.
(5) The existing multi-inverter cooperative control documents do not relate to the problem that the overall dynamic performance of a multi-inverter power station is ensured by setting damping according to a predefined nonlinear curve by adopting adaptive dynamic damping control based on power grid impedance identification and communication is not needed.
Disclosure of Invention
In order to overcome the limitations of various technical schemes, the invention provides a distributed cooperative stable control method, a distributed cooperative stable control device and a distributed cooperative stable control system for a multi-inverter new energy power station, aiming at the problems that the control performance of an inverter is reduced and even a system becomes unstable due to uncertain conditions such as random plug and play of the inverter and power grid impedance fluctuation. The control method is characterized in that a nonlinear observer based on a port controlled Hamilton structure is designed, and the problems of uncertain factors such as parameter perturbation, unmodeled errors, inverter plug and play and the like and the reduction of the passive control performance of a nonlinear change band are solved while passivity and stability conditions are still met after the observer is introduced; and self-adaptive dynamic damping control based on power grid impedance identification is adopted, and damping is set according to a predefined nonlinear curve, so that the overall dynamic performance of the multi-inverter power station is ensured without communication. The method is simple to implement, realizes the distributed cooperative stable control of the multi-inverter power station, and improves the power grid adaptability of the multi-inverter power station.
The object of the invention is thus achieved. The invention provides a distributed cooperative stability control method for a multi-inverter new energy power station, which comprises the following steps:
Preferably, the step 1 comprises the following steps:
step 1.1, collecting voltage u of a point of common coupling PCCa 、u PCCb 、u PCCc Collecting the side current i of the inverter La 、i Lb 、i Lc And collecting DC voltage u of inverter dc ；
Step 1.2, collection according to step 1.1Voltage u of point of common coupling PCCa 、u PCCb 、u PCCc Obtaining the voltage dq axis component u of the point of common coupling through a transformation equation from a three-phase static coordinate system to a two-phase rotating coordinate system PCCd 、u PCCq (ii) a Voltage u of common coupling point PCCa 、u PCCb 、u PCCc Obtaining a voltage phase angle theta of a public coupling point through phase locking of a phase-locked loop;
the transformation equation from the three-phase stationary coordinate system to the two-phase rotating coordinate system of the voltage of the point of common coupling is as follows:
the formula for calculating the voltage phase angle theta of the point of common coupling is as follows:
wherein, ω is 0 Angular frequency, K, of the voltage at the point of common coupling p_PLL Proportional adjustment factor, K, for phase-locked loop PI regulators i_PLL An integral adjustment coefficient of a phase-locked loop PI adjuster is obtained, and s is a Laplace operator;
step 1.3, converting the inverter side current i collected in step 1.1 into a two-phase rotating coordinate system through a three-phase static coordinate system according to the voltage phase angle theta of the point of common coupling obtained in step 1.2 La 、i Lb 、i Lc Converting the current into an inverter side current dq component i under a two-phase rotating coordinate system Ld And i Lq ；
The transformation equation of the output grid-connected current from the three-phase static coordinate system to the two-phase rotating coordinate system is as follows:
step 1.4, obtaining the inverter direct-current voltage u according to the step 1.1 and the step 1.3 respectively dc And an inverter-side current dq component i Ld And i Lq And calculating to obtain a state variable matrix x, namely:
wherein, C dc Is the DC side capacitance of the inverter.
Preferably, the step 2 comprises the following steps:
step 2.1, establishing a mathematical model of the grid-connected inverter in a two-phase rotating coordinate system:
wherein u is d 、u q ，u gd 、u gq ，i Ld 、i Lq ，m d 、m q Respectively, the inverter bridge output voltage, the grid voltage, the inverter inductor current, and the d-axis and q-axis components of the switching modulation, and having u d ＝m d u dc 、u q ＝m q u dc ，i dc Is a direct current, C dc Is a DC side capacitor, L is a filter inductor, omega is a rated angular frequency, r is a line equivalent damping resistor, u is a DC side capacitor dc Is a direct current voltage;
step 2.2, according to the step 2.1, a port controlled Hamilton model which takes the grid-connected inverter as a control object is established, namely:
wherein x represents a state changeQuantity matrix, J (x) is interconnection matrix, R (x) is dissipation matrix, H (x) is Hamiltonian, u is system control law, g u (x) Is an input matrix, and xi is a disturbance matrix;
step 2.3, defining the interconnection matrix J (x) and the dissipation matrix R (x) as follows, according to step 2.1 and step 2.2:
defining an input matrix g u (x) And the system control law u is:
define the Hamiltonian H (x) as:
wherein Q = diag [ L,1];
defining a disturbance matrix xi as:
ξ＝[-u gd /L,-u gq /L,-u dc i dc ] T
step 2.4, according to the disturbance matrix xi defined in step 2.3, obtaining the disturbance matrix xi after external disturbance brought by the plug and play of the inverter as follows:
ξ＝g e (x)U e +gρ(x)ρ
where ρ = [ ρ = vd ,ρ vq ,ρ i ] T Is an external disturbance matrix; u shape e ＝[-u gd ,-u gq ,u dc i dc ] T An external disturbance input matrix is adopted, and superscript T represents matrix transposition; g e (x)＝g ρ (x)＝diag[1/L,1/L,1]Is a coefficient matrix, diag denotes a diagonal matrix;
step 2.5, establishing a port controlled Hamilton model after external disturbance vectors after introducing alternating current side voltage interference and direct current side current interference parameters, namely:
step 2.6, a nonlinear observer loop based on a port controlled Hamilton form is defined, the state variable matrix x obtained in the step 1 is input into the nonlinear observer loop, and a state variable observed value is obtained
And external disturbance matrix estimation
The expression of the nonlinear observer loop is:
wherein x is d Is the steady state value of the state variable matrix x; k is a radical of 1 、k 2 Respectively represent the gains of the nonlinear observer and satisfy
Superscript T represents matrix transposition; h d (x) Is a closed-loop Hamiltonian, and is
Preferably, the step of step 3 is as follows:
step 3.1, establishing a current inner ring continuous domain model based on passive control, namely:
wherein u is gd0 、u gq0 A grid-connected point voltage steady-state value of the inverter is obtained; e.g. of a cylinder 1 ＝x 1 -x 1d ，e 2 ＝x 2 -x 2d ，x 1 And x 2 The first two elements in the state variable matrix x are respectively: i.e. i Ld And i Lq ；x 1d And x 2d Are respectively x 1 And x 2 A steady state value of (d);
step 3.2, establishing a current inner loop discrete domain model based on passive control, namely:
G c (z)＝[(r a +r)T s +(1-z -1 )L]/T s
wherein r is a Is the damping coefficient;
step 3.3, establishing a discrete domain transfer function from the voltage at the bridge arm side of the inverter to the current at the inverter side as follows:
wherein,
a＝(Lω r T s +L g sinω r T s )/(ω r L(L g +L))，b＝(Lω r T s cosω r T s +L g sinω r T s )/(Lω r T s +L g sinω r T s )，
L g for grid inductance, C f As filter capacitors, T s Is the sampling frequency, s is the laplace operator;
step 3.4, according to step 3.2 and step 3.3, establishing a discrete domain transfer function from the inverter current command value to the inverter side current as follows:
G(z)＝z -1 G c (z)G uz (z)/(1+z -1 G c (z)G uz (z))
step 3.5, according to the step 3.4, obtaining the damping coefficient r a Relative inverter current command value to inversionThe characteristic equation of the discrete domain transfer function of the machine side current is:
A c (z -1 )＝1-(2cosω r T s +1)z -1
+((2cosω r T s +1)+a(r a +r)+aL/T s )z -2
+(-1-2a(r a +r)b-2abL/T s -aL/T s )z -3
+(a(r a +r)+aL/T s +2abL/T s )z -4 -aL/T s z -5
step 3.6, according to step 3.5, set the desired damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A m (z -1 )＝1+a m1 z -1 +a m2 z -2 +a m3 z -3 +a m4 z -4 +a m5 z -5
step 3.7, according to step 3.5 and step 3.6, set A m (z -1 )＝A c (z -1 ) To obtain a damping coefficient r a And the grid inductance L g The relationship between, namely: r is a ＝f(L g )。
Preferably, the step 4 comprises the following steps:
step 4.1, construct the desired interconnection matrix J d (x) And a desired dissipation matrix R d (x) Respectively as follows:
wherein,
k is an introduced parameter used for ensuring that the system control law u has a unique solution;
step 4.2, establishing an expected system passive control closed loop equation as follows:
wherein, U ed ＝[-u gd0 ,-u gq0 ,u dc0 i dc0 ] T Is an external disturbance input matrix U ed A steady state value of (d);
step 4.3, according to the observed values of the state variables obtained in the step 2 and the step 3
External disturbance matrix estimation
And a damping coefficient r a And inputting the system control law into the expected system passive control closed loop equation established in the step 4.2 to obtain a system control law u.
The embodiment of the invention also provides a distributed cooperative stability control device for the multi-inverter new energy power station, which comprises:
the sampling matrix module is used for sampling the voltage and the current of the inverter and calculating to obtain a state variable matrix x;
the observation estimation module is used for inputting the state variable matrix x into a nonlinear observer loop to obtain a state variable observation value
And external disturbance matrix estimation
A damping inductance relation module for inputting the state variable matrix x into the adaptive dynamic cooperative loop to obtain a damping coefficient r a And the grid inductance L g The relation between;
a system control rate module forThe state variable observed value
The external disturbance matrix estimation value
And the damping coefficient r a And inputting the input data into a passive control loop to obtain a system control law u.
Preferably, the sampling matrix module is specifically configured to implement the following steps:
step 1.1, collecting voltage u of a point of common coupling PCCa 、u PCCb 、u PCCc And collecting the current i of the inverter side La 、i Lb 、i Lc And collecting DC voltage u of inverter dc ；
Step 1.2, according to the voltage u of the point of common coupling collected in step 1.1 PCCa 、u PCCb 、u PCCc Obtaining the voltage dq axis component u of the point of common coupling through a transformation equation from a three-phase static coordinate system to a two-phase rotating coordinate system PCCd 、u PCCq (ii) a The voltage u of the point of common coupling PCCa 、u PCCb 、u PCCc Obtaining a voltage phase angle theta of a public coupling point through phase locking of a phase-locked loop;
the transformation equation from the three-phase stationary coordinate system to the two-phase rotating coordinate system of the voltage of the point of common coupling is as follows:
the formula for calculating the voltage phase angle theta of the point of common coupling is as follows:
wherein omega is the point of common couplingAngular frequency of compression, K p_PLL Proportional adjustment factor, K, for phase-locked loop PI regulators i_PLL An integral regulating coefficient of a phase-locked loop PI regulator is obtained, and s is a Laplace operator;
step 1.3, converting the inverter side current i collected in step 1.1 into a two-phase rotating coordinate system through a three-phase static coordinate system according to the voltage phase angle theta of the point of common coupling obtained in step 1.2 La 、i Lb 、i Lc Converting the current into an inverter side current dq component i under a two-phase rotating coordinate system Ld And i Lq ；
The transformation equation of the output grid-connected current from the three-phase static coordinate system to the two-phase rotating coordinate system is as follows:
step 1.4, the inverter dc voltage u obtained according to step 1.1 and step 1.3 respectively dc And an inverter side current dq component i Ld And i Lq And calculating to obtain a state variable matrix x, namely:
wherein, C dc Is the dc side capacitance of the inverter.
Preferably, the observation estimation module is specifically configured to implement the following steps:
step 2.1, establishing a mathematical model of the grid-connected inverter in a two-phase rotating coordinate system:
wherein u is d 、u q ，u gd 、u gq ，i Ld 、i Lq ，m d 、m q Respectively, the inverter bridge output voltage, the grid voltage, the inverter inductor current, and the d-axis and q-axis components of the switching modulation, and having u d ＝m d u dc 、u q ＝m q u dc ，i dc Is a direct current, C dc Is a DC side capacitor, L is a filter inductor, omega is a rated angular frequency, r is a line equivalent damping resistor, u is a DC side capacitor dc Is a direct current voltage;
step 2.2, according to the step 2.1, a port controlled Hamilton model which takes the grid-connected inverter as a control object is established, namely:
wherein x represents a state variable matrix, J (x) is an interconnection matrix, R (x) is a dissipation matrix, H (x) is a Hamiltonian, u is a system control law, g u (x) Is an input matrix, and xi is a disturbance matrix;
step 2.3, defining the interconnection matrix J (x) and the dissipation matrix R (x) as follows, according to step 2.1 and step 2.2:
defining an input matrix g u (x) And the system control law u is:
define the Hamiltonian H (x) as:
wherein Q = diag [ L,1];
defining the disturbance matrix xi as:
ξ＝[-u gd /L,-u gq /L,-u dc i dc ] T
step 2.4, according to the disturbance matrix xi defined in step 2.3, obtaining the disturbance matrix xi after external disturbance brought by the plug and play of the inverter as follows:
ξ＝g e (x)U e +g ρ (x)ρ
where ρ = [ ρ = vd ,ρ vq ,ρ i ] T Is an external disturbance matrix; u shape e ＝[-u gd ,-u gq ,u dc i dc ] T An external disturbance input matrix is adopted, and superscript T represents matrix transposition; g e (x)＝g ρ (x)＝diag[1/L,1/L,1]Is a coefficient matrix, diag denotes a diagonal matrix;
step 2.5, establishing a port controlled Hamilton model after external disturbance vectors after introducing alternating current side voltage interference and direct current side current interference parameters, namely:
step 2.6, a nonlinear observer loop based on a port controlled Hamilton form is defined, the state variable matrix x obtained in the step 1 is input into the nonlinear observer loop, and a state variable observed value is obtained
And external disturbance matrix estimation
The expression of the nonlinear observer loop is:
wherein x is d Is the steady state value of the state variable matrix x; k is a radical of 1 、k 2 Respectively represents the gains of the nonlinear observers and satisfies
Superscript T represents matrix transposition; h d (x) Is a closed-loop Hamiltonian, and is
Preferably, the damping inductance relationship module is specifically configured to implement the following steps:
step 3.1, establishing a current inner ring continuous domain model based on passive control, namely:
wherein u is gd0 、u gq0 The grid-connected point voltage steady-state value of the inverter is obtained; e.g. of the type 1 ＝x 1 -x 1d ，e 2 ＝x 2 -x 2d ，x 1 And x 2 The first two elements in the state variable matrix x are respectively: i.e. i Ld And i Lq ；x 1d And x 2d Are respectively x 1 And x 2 A steady state value of;
step 3.2, establishing a current inner loop discrete domain model based on passive control, namely:
G c (z)＝[(r a +r)T s +(1-z -1 )L]/T s
wherein r is a Is the damping coefficient;
step 3.3, establishing a discrete domain transfer function from the voltage at the bridge arm side of the inverter to the current at the bridge arm side of the inverter as follows:
wherein,
a＝(Lω r T s +L g sinω r T s )/(ω r L(L g +L))，b＝(Lω r T s cosω r T s +L g sinω r T s )/(Lω r T s +L g sinω r T s )，
L g for grid inductance, C f Being filter capacitors, T s Is the sampling frequency, s is the laplace operator;
step 3.4, according to step 3.2 and step 3.3, establishing a discrete domain transfer function from the inverter current command value to the inverter side current as follows:
G(z)＝z -1 G c (z)G uz (z)/(1+z -1 G c (z)G uz (z))
step 3.5, according to the step 3.4, obtaining the damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A c (z -1 )＝1-(2cosω r T s +1)z -1
+((2cosω r T s +1)+a(r a +r)+aL/T s )z -2
+(-1-2a(r a +r)b-2abL/T s -aL/T s )z -3
+(a(r a +r)+aL/T s +2abL/T s )z -4 -aL/T s z -5
step 3.6, according to step 3.5, set the desired damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A m (z -1 )＝1+a m1 z -1 +a m2 z -2 +a m3 z -3 +a m4 z -4 +a m5 z -5
step 3.7, according to step 3.5 and step 3.6, set A m (z -1 )＝A c (z -1 ) Obtaining a damping coefficient r a And the grid inductance L g The relationship between, namely: r is a ＝f(L g )。
Preferably, the system control rate module is specifically configured to implement the following steps:
step 4.1, construct the desired interconnection matrix J d (x) And a desired dissipation matrix R d (x) Respectively as follows:
wherein,
k is an introduced parameter used for ensuring that the system control law u has a unique solution;
step 4.2, establishing an expected system passive control closed loop equation as follows:
wherein, U ed ＝[-u gd0 ,-u gq0 ,u dc0 i dc0 ] T Is an external disturbance input matrix U ed A steady state value of (d);
step 4.3, according to the observed values of the state variables obtained in the step 2 and the step 3
External disturbance matrix estimation
And a damping coefficient r a And inputting the control law into the expected system passive control closed-loop equation established in the step 4.2 to obtain a system control law u.
The embodiment of the invention also provides a new energy power station, which comprises: a plurality of inverters;
the plurality of inverters are operated based on the distributed cooperative stable control method of the multi-inverter new energy power station.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides the mutual cooperation of the three control loops, the implementation mode is simple and effective, the distributed cooperative stable control of the multi-inverter power station is realized, and the power grid adaptability of the multi-inverter power station is improved.
2. The passive control loop is a basic controller of a single grid-connected inverter, the passivity of the system is guaranteed through the design from the energy reconstruction angle, and the passivity and the stability of the whole system are guaranteed when the passive control loop is expanded to a multi-inverter power station.
3. The nonlinear observer loop based on the port-controlled Hamilton structure, which is designed by the invention, can solve the problems of uncertain factors such as parameter perturbation, unmodeled errors, inverter plug and play and the like and the reduction of the passive control performance of a nonlinear change band while still meeting the passivity and stability conditions after the observer is introduced.
4. According to the invention, the self-adaptive dynamic damping control loop based on the power grid impedance identification is adopted to set the damping according to the predefined nonlinear curve, so that the overall dynamic performance of the multi-inverter power station is ensured without communication, and the cost, the volume and the system loss of the system are not increased.
Drawings
FIG. 1 is a schematic view of a topological structure of a multi-inverter new energy power station adopted by the invention;
FIG. 2 is a schematic diagram of a distributed cooperative stability control method for a multi-inverter new energy power station according to the present invention;
FIG. 3 is a schematic diagram of a damping nonlinear curve of an adaptive dynamic damping control loop based on power grid impedance identification according to the present invention;
FIG. 4 shows a d-axis grid current step command i without considering grid impedance Ldref Step response i Ld And the simulation waveform of the output value of the nonlinear observer;
FIG. 5 shows a d-axis grid current step command i when the grid impedance is equal to 0.1p.u Ldref Step response i Ld The simulated waveform of (2);
FIG. 6 shows a d-axis grid current step command i when the grid impedance is equal to 1p.u Ldref Step response i Ld The simulated waveform of (2);
FIG. 7 shows a d-axis grid current step command i when the grid impedance is equal to 5p.u Ldref Step response i Ld The simulated waveform of (2);
FIG. 8 is a three-phase grid-connected current step response simulation waveform when the grid impedance is equal to 5p.u;
FIG. 9 is a three-phase grid-connected current step response simulation waveform adopting a traditional proportional-integral linear control strategy when the grid impedance is equal to 5p.u.
Detailed Description
The embodiment of the invention provides a distributed cooperative stable control method for a multi-inverter new energy power station, which aims to solve the problems that in the prior art, the inverter is subjected to random plug and play, the impedance fluctuation of a power grid and other uncertain conditions are caused, the control performance of the inverter is deteriorated, and even a system becomes unstable; and self-adaptive dynamic damping control based on power grid impedance identification is adopted, and damping is set according to a predefined nonlinear curve, so that the overall dynamic performance of the multi-inverter power station is ensured, and communication is not needed. The method is simple to implement, realizes the distributed cooperative stable control of the multi-inverter power station, and improves the power grid adaptability of the multi-inverter power station.
The technical solution of the present invention will be clearly and completely described with reference to the accompanying drawings.
The topological structure schematic diagram of the multi-inverter new energy power station adopted by the invention is shown in figure 1. The multiple inversionThe topological structure of the new energy power station consists of a plurality of identical grid-connected inverters, the number of the grid-connected inverters in the multi-inverter system is n, n is a positive integer, and n is>1; each grid-connected inverter topological structure comprises a direct-current side capacitor C dc Three-phase bridge type inversion topology, inverter side inductor L and filter capacitor C f Line equivalent damping resistance r and network side inductance L 2 The filter passes through a common coupling point PCC and has a power grid impedance Z g Is connected to the three-phase network of g To the network impedance Z g Resistive component of L g To the network impedance Z g The perceptual component of (a). In this example, C dc ＝600μF，L＝2.5mH，C f ＝36μF，r＝0.15Ω，r g ＝0，L 2 ＝0.1mH，L g ＝1mH。
Fig. 2 is a schematic diagram of a distributed cooperative stability control method for a multi-inverter new energy power station according to the present invention. As can be seen from fig. 2, the steps of the control method in the embodiment of the present invention are as follows:
The step 1 comprises the following steps:
step 1.1, collecting voltage u of a point of common coupling PCCa 、u PCCb 、u PCCc Collecting the side current i of the inverter La 、i Lb 、i Lc And collecting DC voltage u of inverter dc 。
Step 1.2, according to the voltage u of the common coupling point collected in step 1.1 PCCa 、u PCCb 、u PCCc Obtaining the voltage dq axis component u of the point of common coupling through a transformation equation from a three-phase static coordinate system to a two-phase rotating coordinate system PCCd 、u PCCq (ii) a Voltage u of common coupling point PCCa 、u PCCb 、u PCCc And obtaining the voltage phase angle theta of the point of common coupling through phase locking of a phase-locked loop.
The transformation equation from the three-phase stationary coordinate system to the two-phase rotating coordinate system of the voltage of the point of common coupling is as follows:
the formula for calculating the voltage phase angle theta of the point of common coupling is as follows:
where ω is the angular frequency of the voltage at the point of common coupling, K p_PLL Proportional adjustment factor, K, for phase-locked loop PI regulators i_PLL And s is a Laplace operator, and is an integral regulation coefficient of the phase-locked loop PI regulator. In the present example, ω =314rad/s, K p_PLL ＝2000，K i_PLL ＝1。
Step 1.3, obtaining according to step 1.2Converting the voltage phase angle theta of the public coupling point from a three-phase static coordinate system to a two-phase rotating coordinate system, and converting the inverter side current i acquired in the step 1.1 La 、i Lb 、i Lc Converting the current into an inverter side current dq component i under a two-phase rotating coordinate system Ld And i Lq 。
The transformation equation of the output grid-connected current from the three-phase static coordinate system to the two-phase rotating coordinate system is as follows:
step 1.4, obtaining the inverter direct-current voltage u according to the step 1.1 and the step 1.3 respectively dc And an inverter-side current dq component i Ld And i Lq And calculating to obtain a state variable matrix x, namely:
wherein, C dc Is the DC side capacitance of the inverter.
The step 2 comprises the following steps:
step 2.1, establishing a mathematical model of the grid-connected inverter in a two-phase rotating coordinate system:
wherein u is d 、u q ，u gd 、u gq ，i Ld 、i Lq ，m d 、m q Respectively, the inverter bridge output voltage, the grid voltage, the inverter inductor current, and the d-axis and q-axis components of the switching modulation, and having u d ＝m d u dc 、u q ＝m q u dc ，i dc Is a direct current, C dc Is a DC side capacitor, L is a filter inductor, omega is a rated angular frequency, r is a line equivalent damping resistor, u is a DC side capacitor dc Is a direct current voltage.
Step 2.2, according to the step 2.1, a port controlled Hamilton model which takes the grid-connected inverter as a control object is established, namely:
wherein x represents a state variable matrix, J (x) is an interconnection matrix, R (x) is a dissipation matrix, H (x) is a Hamiltonian, u is a system control law, g u (x) To the input matrix, ξ is the perturbation matrix.
Step 2.3, defining the interconnection matrix J (x) and the dissipation matrix R (x) as follows, according to step 2.1 and step 2.2:
defining an input matrix g u (x) And the system control law u is:
define the Hamiltonian H (x) as:
wherein Q = diag [ L,1];
defining the disturbance matrix xi as:
ξ＝[-u gd /L,-u gq /L,-u dc i dc ] T
step 2.4, according to the disturbance matrix xi defined in step 2.3, obtaining the disturbance matrix xi after introducing external disturbance brought by the plug and play of the inverter as follows:
ξ＝g e (x)U e +g ρ (x)ρ
where ρ = [ ρ = vd ,ρ vq ,ρ i ] T Is an external disturbance matrix; u shape e ＝[-u gd ,-u gq ,u dc i dc ] T An external disturbance input matrix is adopted, and superscript T represents matrix transposition; g e (x)＝g ρ (x)＝diag[1/L,1/L,1]Is a coefficient matrix and diag denotes a diagonal matrix.
Step 2.5, establishing a port controlled Hamilton model after external disturbance vectors after the introduction of AC side voltage interference and DC side current interference parameters, namely:
step 2.6, a nonlinear observer loop based on a port controlled Hamilton form is defined, the state variable matrix x obtained in the step 1 is input into the nonlinear observer loop, and a state variable observed value is obtained
And external disturbance matrix estimation
The expression of the nonlinear observer loop is:
wherein x is d Is the steady state value of the state variable matrix x; k is a radical of 1 、k 2 Respectively represents the gains of the nonlinear observers and satisfies
Superscript T represents matrix transposition; h d (x) Is a closed-loop Hamiltonian, and is
In the present embodiment, the sum of the nonlinear observer estimation error and the hamiltonian H (x) is defined as the leiampiroff function V:
wherein,
and
an estimated error matrix representing the non-linear observer.
The derivative of the Lyapunov function V with respect to time is calculated, namely:
wherein,
and
respectively represent x d 、ε x And ε ρ The superscript T represents the matrix transpose over the derivative of time. Due to the fact that
Therefore, the system after the nonlinear observer is introduced can meet the Lyapunov stability condition.
The step 3 comprises the following steps:
step 3.1, establishing a current inner loop continuous domain model based on passive control, namely:
wherein u is gd0 、u gq0 The grid-connected point voltage steady-state value of the inverter is obtained; e.g. of the type 1 ＝x 1 -x 1d ，e 2 ＝x 2 -x 2d ，x 1 And x 2 The first two elements in the state variable matrix x are respectively: i all right angle Ld And i Lq ；x 1d And x 2d Are respectively x 1 And x 2 The steady state value of (c).
Step 3.2, establishing a current inner loop discrete domain model based on passive control, namely:
G c (z)＝[(r a +r)T s +(1-z -1 )L]/T s
wherein r is a Is the damping coefficient.
Step 3.3, establishing a discrete domain transfer function from the voltage at the bridge arm side of the inverter to the current at the bridge arm side of the inverter as follows:
wherein,
a＝(Lω r T s +L g sinω r T s )/(ω r L(L g +L))，b＝(Lω r T s cosω r T s +L g sinω r T s )/(Lω r T s +L g sinω r T s )，
L g as inductance of the grid, C f As filter capacitors, T s For the sampling frequency, s is the laplacian operator.
Step 3.4, according to step 3.2 and step 3.3, establishing a discrete domain transfer function from the inverter current command value to the inverter side current as follows:
G(z)＝z -1 G c (z)G uz (z)/(1+z -1 G c (z)G uz (z))
step 3.5, according to the step 3.4, obtaining the damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A c (z -1 )＝1-(2cosω r T s +1)z -1
+((2cosω r T s +1)+a(r a +r)+aL/T s )z -2
+(-1-2a(r a +r)b-2abL/T s -aL/T s )z -3
+(a(r a +r)+aL/T s +2abL/T s )z -4 -aL/T s z -5
step 3.6, according to step 3.5, set the desired damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A m (z -1 )＝1+a m1 z -1 +a m2 z -2 +a m3 z -3 +a m4 z -4 +a m5 z -5
step 3.7, according to step 3.5 and step 3.6, set A m (z -1 )＝A c (z -1 ) Obtaining a damping coefficient r a And the grid inductance L g The relationship between, namely: r is a radical of hydrogen a ＝f(L g )。
The expression obtained in step 3.7 shows the impedance L of the power grid g And damping coefficient r of passive controller dissipation matrix a A non-linear curve in between. In the embodiment of the present invention, fig. 3 is a schematic diagram of a damping nonlinear curve of an adaptive dynamic damping control loop based on grid impedance identification according to the present invention. As can be seen from fig. 3, by setting the damping according to a predefined non-linear curve, the overall dynamic performance of the multi-inverter plant can be ensured without the problem of communication.
The step 4 comprises the following steps:
step 4.1, construct the desired interconnection matrix J d (x) And a desired dissipation matrix R d (x) Respectively as follows:
wherein,
wherein K is an introduced parameter used for ensuring that the system control law u has a unique solution.
Step 4.2, establishing an expected system passive control closed loop equation as follows:
wherein, U ed ＝[-u gd0 ,-u gq0 ,u dc0 i dc0 ] T Is an externally perturbed input matrix U ed The steady state value of (c).
Step 4.3, according to the observed values of the state variables obtained in the step 2 and the step 3
External disturbance matrix estimation
And a damping coefficient r a And inputting the system control law into the expected system passive control closed loop equation established in the step 4.2 to obtain a system control law u.
FIG. 4 shows a d-axis grid current step command i without considering grid impedance Ldref Step response i Ld And a simulated waveform of the output value of the proposed nonlinear observer. As can be seen from fig. 4, the grid-connected current response can quickly track the command signal, and the adopted non-linear observer can accurately obtain the corresponding current value without error.
FIG. 5, FIG. 6 and FIG. 7 are respectively the grid impedancesEqual to 0.1p.u., 1p.u and 5p.u, the d-axis grid current step command i obtained by the method Ldref Step response i Ld The simulated waveform of (2). Comparing fig. 5, 6 and 7, it can be seen that: the larger the power grid impedance is, the larger the overshoot of the current step response of the grid-connected inverter based on the passive control is, and the longer the adjustment time is, but the system can always ensure stable operation. When the power grid impedance is equal to 5p.u., a three-phase grid-connected current step response simulation waveform under the condition of adopting the method and a three-phase grid-connected current step response simulation waveform adopting a traditional proportional-integral linear control strategy are respectively shown in the figures 8 and 9. I in FIGS. 8 and 9 La 、i Lb 、i Lc The three phases of grid-connected currents A, B and C are respectively shown. Comparing fig. 8 and fig. 9, it can be seen that when the conventional proportional-integral-linear control strategy is adopted, the grid-connected current waveform generates an obvious harmonic amplification phenomenon, and the control strategy provided by the present invention can always ensure good quality of the grid-connected current.
Compared with the fig. 3-9, the distributed cooperative stable control method for the multi-inverter new energy power station can effectively solve the problems that the inverter control performance is reduced and even the system becomes unstable due to uncertain conditions such as random plug and play of the inverter and power grid impedance fluctuation in the prior art, and effectively improves the power grid adaptability of the multi-inverter power station.
Based on the distributed cooperative stability control method for the multi-inverter new energy power station, the embodiment of the invention also provides a distributed cooperative stability control device for the multi-inverter new energy power station, and the distributed cooperative stability control device for the multi-inverter new energy power station comprises:
the sampling matrix module is used for sampling the voltage and the current of the inverter and calculating to obtain a state variable matrix x;
an observation estimation module for inputting the state variable matrix x into a nonlinear observer loop to obtain a state variable observed value
And external disturbance matrix estimation
A damping inductance relation module for inputting the state variable matrix x into the adaptive dynamic cooperative loop to obtain a damping coefficient r a And the grid inductance L g The relation between;
a system control rate module to apply the state variable observations
The external disturbance matrix estimation value
And the damping coefficient r a And inputting the input data into a passive control loop to obtain a system control law u.
The sampling matrix module, the observation estimation module, the damping inductance relation module and the system control rate module respectively implement the methods of step 1 to step 4, which are not described in detail.
Based on the distributed cooperative stability control method for the multi-inverter new energy power station, the embodiment of the invention also provides a new energy power station, and the new energy power station comprises: a plurality of inverters;
and (4) the plurality of inverters are operated based on the distributed cooperative stable control method of the multi-inverter new energy power station in any one of the steps 1 to 4.
In conclusion, the control method provided by the invention has the advantages that the three control loops are mutually matched, the implementation mode is simple, convenient and effective, the distributed cooperative stable control of the multi-inverter power station is realized, and the power grid adaptability of the multi-inverter power station is improved; the passive control loop is a basic controller of a single grid-connected inverter, the passivity of the system is guaranteed by design from the energy reconstruction angle, and the passivity and the stability of the whole system are guaranteed when the passive control loop is expanded to a multi-inverter power station. The designed nonlinear observer loop based on the port controlled Hamilton structure can solve the problems of uncertain factors such as parameter perturbation, unmodeled errors, inverter plug and play and the like and the reduction of the passive control performance of a nonlinear change band while still meeting the passivity and stability conditions after the observer is introduced; the self-adaptive dynamic damping control loop based on the power grid impedance identification sets the damping according to the predefined nonlinear curve, ensures the whole dynamic performance of the multi-inverter power station without the problem of communication, and does not increase the cost, the volume and the system loss of the system.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a component of' 8230; \8230;" does not exclude the presence of another like element in a process, method, article, or apparatus that comprises the element.
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 (10)
1. A distributed cooperative stability control method for a multi-inverter new energy power station is characterized by comprising the following steps:
step 1, sampling voltage and current of an inverter, and calculating to obtain a state variable matrix x;
step 2, inputting the state variable matrix x obtained in the step 1 into a nonlinear observer loop to obtain a state variable observed value
And external disturbance matrix estimation
Step 3, inputting the state variable matrix x obtained in the step 1 into the self-adaptive dynamic cooperative loop to obtain a damping coefficient r a And the grid inductance L g A relation therebetween;
step 4, observing values of the state variables obtained in the step 2 and the step 3
External disturbance matrix estimation
And a damping coefficient r a And inputting the input data into a passive control loop to obtain a system control law u.
2. The distributed cooperative stability control method for the multi-inverter new energy power station according to claim 1, wherein the step 1 comprises the following steps:
step 1.1, collecting voltage u of a point of common coupling PCCa 、u PCCb 、u PCCc Collecting the side current i of the inverter La 、i Lb 、i Lc And collecting DC voltage u of inverter dc ；
Step 1.2, according to the voltage u of the point of common coupling collected in step 1.1 PCCa 、u PCCb 、u PCCc Obtaining the voltage dq axis component u of the point of common coupling through a transformation equation from a three-phase static coordinate system to a two-phase rotating coordinate system PCCd 、u PCCq (ii) a The voltage u of the point of common coupling PCCa 、u PCCb 、u PCCc Obtaining a voltage phase angle theta of a public coupling point through phase locking of a phase-locked loop;
the transformation equation from the three-phase stationary coordinate system to the two-phase rotating coordinate system of the voltage of the point of common coupling is as follows:
the formula for calculating the voltage phase angle theta of the point of common coupling is as follows:
where ω is the angular frequency of the voltage at the point of common coupling, K p_PLL Proportional adjustment factor, K, for phase-locked loop PI regulators i_PLL An integral adjustment coefficient of a phase-locked loop PI adjuster is obtained, and s is a Laplace operator;
step 1.3, converting the inverter side current i acquired in step 1.1 into a two-phase rotating coordinate system through a three-phase static coordinate system according to the voltage phase angle theta of the point of common coupling obtained in step 1.2 La 、i Lb 、i Lc Converting the current into an inverter side current dq component i under a two-phase rotating coordinate system Ld And i Lq ；
The transformation equation of the output grid-connected current from the three-phase static coordinate system to the two-phase rotating coordinate system is as follows:
step 1.4, obtaining the inverter direct-current voltage u according to the step 1.1 and the step 1.3 respectively dc And an inverter-side current dq component i Ld And i Lq And calculating to obtain a state variable matrix x, namely:
wherein, C dc Is the DC side capacitance of the inverter.
3. The distributed cooperative stability control method for the multi-inverter new energy power station according to claim 2, wherein the step 2 comprises the following steps:
step 2.1, establishing a mathematical model of the grid-connected inverter in a two-phase rotating coordinate system:
wherein u is d 、u q ，u gd 、u gq ，i Ld 、i Lq ，m d 、m q Respectively, the inverter bridge output voltage, the grid voltage, the inverter inductor current, and the d-axis and q-axis components of the switching modulation, and having u d ＝m d u dc 、u q ＝m q u dc ，i dc Is a direct current, C dc Is a DC side capacitor, L is a filter inductor, omega is a rated angular frequency, r is a line equivalent damping resistor, u is a DC side capacitor dc Is a direct current voltage;
step 2.2, according to the step 2.1, a port controlled Hamilton model taking the grid-connected inverter as a control object is established, namely:
wherein x represents a state variable matrix, J (x) is an interconnection matrix, R (x) is a dissipation matrix, H (x) is a Hamiltonian, u is a system control law, g u (x) Is an input matrix, and xi is a disturbance matrix;
step 2.3, defining the interconnection matrix J (x) and the dissipation matrix R (x) as follows, according to step 2.1 and step 2.2:
defining an input matrix g u (x) And the system control law u is:
define the Hamiltonian H (x) as:
wherein Q = diag [ L,1];
defining a disturbance matrix xi as:
ξ＝[-u gd /L,-u gq /L,-u dc i dc ] T
step 2.4, according to the disturbance matrix xi defined in step 2.3, obtaining the disturbance matrix xi after introducing external disturbance brought by the plug and play of the inverter as follows:
ξ＝g e (x)U e +g ρ (x)ρ
where ρ = [ ρ = vd ,ρ vq ,ρ i ] T Is an external disturbance matrix; u shape e ＝[-u gd ,-u gq ,u dc i dc ] T An external disturbance input matrix is adopted, and superscript T represents matrix transposition; g e (x)＝g ρ (x)＝diag[1/L,1/L,1]Is a coefficient matrix, diag denotes a diagonal matrix;
step 2.5, establishing a port controlled Hamilton model after external disturbance vectors after introducing alternating current side voltage interference and direct current side current interference parameters, namely:
step 2.6, a nonlinear observer loop based on a port controlled Hamilton form is defined, and the shape obtained in the step 1 is processedInputting the state variable matrix x into the nonlinear observer loop to obtain state variable observed value
And external disturbance matrix estimation
The expression of the nonlinear observer loop is:
wherein x is d Is the steady state value of the state variable matrix x; k is a radical of 1 、k 2 Respectively represents the gains of the nonlinear observers and satisfies
Superscript T represents matrix transposition; h d (x) Is a closed-loop Hamiltonian, and is
4. The distributed cooperative stability control method for the multi-inverter new energy power station according to claim 2, wherein the step 3 comprises the following steps:
step 3.1, establishing a current inner loop continuous domain model based on passive control, namely:
wherein u is gd0 、u gq0 The grid-connected point voltage steady-state value of the inverter is obtained; e.g. of the type 1 ＝x 1 -x 1d ，e 2 ＝x 2 -x 2d ，x 1 And x 2 The first two elements in the state variable matrix x are respectively:i Ld and i Lq ；x 1d And x 2d Are each x 1 And x 2 A steady state value of;
step 3.2, establishing a current inner loop discrete domain model based on passive control, namely:
G c (z)＝[(r a +r)T s +(1-z -1 )L]/T s
wherein r is a Is the damping coefficient;
step 3.3, establishing a discrete domain transfer function from the voltage at the bridge arm side of the inverter to the current at the bridge arm side of the inverter as follows:
wherein,
a＝(Lω r T s +L g sinω r T s )/(ω r L(L g +L))，b＝(Lω r T s cosω r T s +L g sinω r T s )/(Lω r T s +L g sinω r T s )，
L g as inductance of the grid, C f Being filter capacitors, T s Is the sampling frequency, s is the laplace operator;
step 3.4, according to step 3.2 and step 3.3, establishing a discrete domain transfer function from the inverter current command value to the inverter side current as follows:
G(z)＝z -1 G c (z)G uz (z)/(1+z -1 G c (z)G uz (z))
step 3.5, according to the step 3.4, obtaining the damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A c (z -1 )＝1-(2cosω r T s +1)z -1 +((2cosω r T s +1)+a(r a +r)+aL/T s )z -2 +(-1-2a(r a +r)b-2abL/T s -aL/T s )z -3 +(a(r a +r)+aL/T s +2abL/T s )z -4 -aL/T s z -5
step 3.6, according to step 3.5, set the desired damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A m (z -1 )＝1+a m1 z -1 +a m2 z -2 +a m3 z -3 +a m4 z -4 +a m5 z -5
step 3.7, according to step 3.5 and step 3.6, set A m (z -1 )＝A c (z -1 ) To obtain a damping coefficient r a And the grid inductance L g The relationship between them, namely: r is a radical of hydrogen a ＝f(L g )。
5. The distributed cooperative stability control method for the multi-inverter new energy power station according to claim 4, wherein the step 4 comprises the following steps:
step 4.1, construct the desired interconnection matrix J d (x) And a desired dissipation matrix R d (x) Respectively as follows:
wherein,
k is an introduced parameter used for ensuring that the system control law u has a unique solution;
step 4.2, establishing an expected system passive control closed loop equation as follows:
wherein, U ed ＝[-u gd0 ,-u gq0 ,u dc0 i dc0 ] T Is an external disturbance input matrix U ed A steady state value of (d);
step 4.3, according to the state variable observed value obtained in the step 2 and the step 3
External disturbance matrix estimation
And a damping coefficient r a And inputting the control law into the expected system passive control closed-loop equation established in the step 4.2 to obtain a system control law u.
6. The distributed cooperative stability control device for the multi-inverter new energy power station is characterized by comprising the following components:
the sampling matrix module is used for sampling the voltage and the current of the inverter and calculating to obtain a state variable matrix x;
the observation estimation module is used for inputting the state variable matrix x into a nonlinear observer loop to obtain a state variable observation value
And external disturbance matrix estimation
A damping inductance relation module for inputting the state variable matrix x into the adaptive dynamic cooperative loop to obtain a damping coefficient r a And the grid inductance L g A relation therebetween;
a system control rate module to apply the state variable observations
The external disturbance matrix estimation value
And the damping coefficient r a And inputting the input data into a passive control loop to obtain a system control law u.
7. The distributed cooperative stability control device for the multi-inverter new energy power station according to claim 6, wherein the sampling matrix module is specifically configured to implement the following steps:
step 1.1, collecting voltage u of a point of common coupling PCCa 、u PCCb 、u PCCc And collecting the current i of the inverter side La 、i Lb 、i Lc And collecting DC voltage u of inverter dc ；
Step 1.2, according to the voltage u of the point of common coupling collected in step 1.1 PCCa 、u PCCb 、u PCCc Obtaining the voltage dq axis component u of the point of common coupling through a transformation equation from a three-phase static coordinate system to a two-phase rotating coordinate system PCCd 、u PCCq (ii) a The voltage u of the point of common coupling PCCa 、u PCCb 、u PCCc Obtaining a voltage phase angle theta of a public coupling point through phase locking of a phase-locked loop;
the transformation equation from the three-phase stationary coordinate system to the two-phase rotating coordinate system of the voltage of the point of common coupling is as follows:
the formula for calculating the voltage phase angle theta of the point of common coupling is as follows:
where ω is the angular frequency of the voltage at the point of common coupling, K p_PLL Proportional adjustment factor, K, for phase-locked loop PI regulators i_PLL An integral adjustment coefficient of a phase-locked loop PI adjuster is obtained, and s is a Laplace operator;
step 1.3, converting the inverter side current i acquired in step 1.1 into a two-phase rotating coordinate system through a three-phase static coordinate system according to the voltage phase angle theta of the point of common coupling obtained in step 1.2 La 、i Lb 、i Lc Converting the component into an inverter side current dq under a two-phase rotating coordinate system Ld And i Lq ；
The transformation equation of the output grid-connected current from the three-phase static coordinate system to the two-phase rotating coordinate system is as follows:
step 1.4, obtaining the inverter direct-current voltage u according to the step 1.1 and the step 1.3 respectively dc And an inverter side current dq component i Ld And i Lq And calculating to obtain a state variable matrix x, namely:
wherein, C dc Is the DC side capacitance of the inverter.
8. The distributed cooperative stability control apparatus for a multi-inverter new energy power station as claimed in claim 7, wherein the observation estimation module is specifically configured to implement the following steps:
step 2.1, establishing a mathematical model of the grid-connected inverter in a two-phase rotating coordinate system:
wherein u is d 、u q ，u gd 、u gq ，i Ld 、i Lq ，m d 、m q Respectively, the inverter bridge output voltage, the grid voltage, the inverter inductor current, and the d-axis and q-axis components of the switching modulation, and having u d ＝m d u dc 、u q ＝m q u dc ，i dc Is a direct current, C dc Is a DC side capacitor, L is a filter inductor, omega is a rated angular frequency, r is a line equivalent damping resistor, u is a DC side capacitor dc Is a direct current voltage;
step 2.2, according to the step 2.1, a port controlled Hamilton model taking the grid-connected inverter as a control object is established, namely:
wherein x represents a state variable matrix, J (x) is an interconnection matrix, R (x) is a dissipation matrix, H (x) is a Hamiltonian, u is a system control law, g u (x) Is an input matrix, and xi is a disturbance matrix;
step 2.3, defining the interconnection matrix J (x) and the dissipation matrix R (x) as follows, according to step 2.1 and step 2.2:
defining an input matrix g u (x) And the system control law u is:
define the Hamiltonian H (x) as:
wherein Q = diag [ L,1];
defining the disturbance matrix xi as:
ξ＝[-u gd /L,-u gq /L,-u dc i dc ] T
step 2.4, according to the disturbance matrix xi defined in step 2.3, obtaining the disturbance matrix xi after external disturbance brought by the plug and play of the inverter as follows:
ξ＝g e (x)U e +gρ(x)ρ
where ρ = [ ρ ] vd ,ρ vq ,ρ i ] T Is an external disturbance matrix; u shape e ＝[-u gd ,-u gq ,u dc i dc ] T An external disturbance input matrix is adopted, and superscript T represents matrix transposition; g e (x)＝g ρ (x)＝diag[1/L,1/L,1]Is a coefficient matrix, diag denotes a diagonal matrix;
step 2.5, establishing a port controlled Hamilton model after external disturbance vectors after the introduction of AC side voltage interference and DC side current interference parameters, namely:
step 2.6, a nonlinear observer loop based on a port controlled Hamilton form is defined, the state variable matrix x obtained in the step 1 is input into the nonlinear observer loop, and a state variable observed value is obtained
And external disturbance matrix estimation
The expression of the nonlinear observer loop is:
wherein x is d Is the steady state value of the state variable matrix x; k is a radical of 1 、k 2 Respectively represent the gains of the nonlinear observer and satisfy
Superscript T represents matrix transposition; h d (x) Is a closed-loop Hamiltonian, and is
9. The distributed cooperative stability control apparatus for the multi-inverter new energy power station of claim 7, wherein the damping inductance relationship module is specifically configured to implement the following steps:
step 3.1, establishing a current inner loop continuous domain model based on passive control, namely:
wherein u is gd0 、u gq0 A grid-connected point voltage steady-state value of the inverter is obtained; e.g. of the type 1 ＝x 1 -x 1d ，e 2 ＝x 2 -x 2d ，x 1 And x 2 The first two elements in the state variable matrix x are respectively: i all right angle Ld And i Lq ；x 1d And x 2d Are respectively x 1 And x 2 A steady state value of;
step 3.2, establishing a current inner loop discrete domain model based on passive control, namely:
G c (z)＝[(r a +r)T s +(1-z -1 )L]/T s
wherein r is a Is the damping coefficient;
step 3.3, establishing a discrete domain transfer function from the voltage at the bridge arm side of the inverter to the current at the bridge arm side of the inverter as follows:
wherein,
a＝(Lω r T s +L g sinω r T s )/(ω r L(L g +L))，b＝(Lω r T s cosω r T s +L g sinω r T s )/(Lω r T s +L g sinω r T s )，
L g for grid inductance, C f Being filter capacitors, T s Is the sampling frequency, s is the laplace operator;
step 3.4, according to step 3.2 and step 3.3, establishing a discrete domain transfer function from the inverter current command value to the inverter side current as follows:
G(z)＝z -1 G c (z)G uz (z)/(1+z -1 G c (z)G uz (z))
step 3.5, according to the step 3.4, obtaining the damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A c (z -1 )＝1-(2cosω r T s +1)z -1 +((2cosω r T s +1)+a(r a +r)+aL/T s )z -2 +(-1-2a(r a +r)b-2abL/T s -aL/T s )z -3 +(a(r a +r)+aL/T s +2abL/T s )z -4 -aL/T s z -5
step 3.6, according to step 3.5, set the desired damping coefficient r a The characteristic equation of the discrete domain transfer function of the relevant inverter current command value to the inverter side current is as follows:
A m (z -1 )＝1+a m1 z -1 +a m2 z -2 +a m3 z -3 +a m4 z -4 +a m5 z -5
step 3.7, according to step 3.5 and step 3.6, set A m (z -1 )＝A c (z -1 ) Obtaining a damping coefficient r a And the grid inductance L g The relationship between, namely: r is a ＝f(L g )。
10. A new energy power plant, characterized in that the new energy power plant comprises: a plurality of inverters;
the plurality of inverters are operated based on the distributed collaborative stability control method of the multi-inverter new energy power station according to any one of claims 1-5.
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