CN116780502A - Method and system for determining influence of power generation energy on low-frequency oscillation of power system - Google Patents
Method and system for determining influence of power generation energy on low-frequency oscillation of power system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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Abstract
The invention discloses a method and a system for determining the influence of power generation energy on low-frequency oscillation of an electric power system, which relate to the field of stability analysis of new energy electric power systems, and comprise the following steps: firstly, establishing a small signal model of each power generation energy source; the power generation energy sources comprise photo-thermal energy sources, thermal power energy sources, photovoltaic energy sources and wind power energy sources; then determining a state matrix of the new energy power system model; determining a sensitivity matrix of damping torque of each power generation energy area under each mode according to the state matrix and the oscillation mode of the new energy power system; determining the damping of each power generation energy region to the low-frequency oscillation region of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix; and finally, determining the access position and the access power of each power generation energy source according to the regional damping. Based on the state matrix and the sensitivity matrix, the method can determine the damping of the low-frequency oscillation area of the new energy power system in each mode of each power generation energy area, and further analyze the low-frequency oscillation of the power system.
Description
Technical Field
The invention relates to the field of stability analysis of new energy power systems, in particular to a method and a system for determining the influence of power generation energy on low-frequency oscillation of a power system.
Background
In recent years, high-energy consumption and high-pollution thermal power generating units are gradually replaced by new energy sources such as wind power, photovoltaic and photo-thermal power generating units, and the problem brought by the high-energy consumption and high-pollution thermal power generating units is that the integration of large-scale new energy stations possibly has negative influence on the stability of a power system, and particularly when the new energy sources such as wind power, photovoltaic and photo-thermal power generating units fluctuate or fail, the power system can be severely fluctuated, so that the analysis of the problem of low-frequency oscillation of the power system containing the new energy sources such as photo-thermal power generation, wind power and photovoltaic is particularly important.
However, in the prior art, the research on the low-frequency oscillation of the new energy power system mainly aims at the condition of single new energy grid connection, the research on the condition of multiple new energy grid connection is lacked, the research on the stability of the power system containing photo-thermal power generation in the prior art is less, and the influence of photo-thermal power generation grid connection on the low-frequency oscillation of the high-proportion new energy power system is not clear.
Disclosure of Invention
The invention aims to provide a method and a system for determining the influence of power generation energy on low-frequency oscillation of a power system, which can analyze the influence of multiple new energy grid connection on the low-frequency oscillation of the new energy power system.
The invention provides a method for determining the influence of power generation energy on low-frequency oscillation of an electric power system, which comprises the following steps:
step 1: establishing a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle;
step 2: determining a state matrix of a new energy power system model; the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy;
step 3: determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system;
step 4: determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix;
step 5: and determining the access position and the access power of each power generation energy source according to the regional damping.
Optionally, the step 3-4 specifically includes:
performing matrix decomposition and region-by-region expansion on the state matrix, and determining a power generation motor rotating speed variable, a first forward channel matrix and a second forward channel matrix of each power generation energy region; the first forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to the power generation energy source region; the second forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to any power generation energy source region except the power generation energy source region;
Determining a first damping torque matrix provided by the power generation energy region to the power generation energy region under each oscillation mode according to the power generation motor rotating speed variable of the power generation energy region, the first forward channel matrix and the oscillation mode of the new energy power system;
determining a second damping torque matrix provided by the power generation energy region to any power generation energy region except the power generation energy region in each oscillation mode according to the power generation motor rotation speed variable of the power generation energy region, the second forward channel matrix and the oscillation mode of the new energy power system;
calculating the regional damping provided by the power generation energy region to the low-frequency oscillation of the new energy power system under each mode according to the sensitivity matrix, the first damping torque matrix and the second damping torque matrix; the sensitivity matrix represents the influence capability of the power generation energy region on the mode.
Optionally, the method further comprises:
according toCalculating the sensitivity matrix, wherein S i,m Sensitivity matrix of mth oscillation mode to ith power generation energy region, lambda m Is the characteristic value of the mth oscillation mode, T i m Damping torque for the i-th power generation energy region.
Optionally, after step 4, the method further includes:
adjusting the access power of each power generation energy source for multiple times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system in each oscillation mode;
and determining the optimal access power of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple adjustment.
Optionally, after step 4, the method further includes:
adjusting the access position of each power generation energy source for a plurality of times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system in each oscillation mode;
and determining the optimal access position of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple times of adjustment.
Optionally, the small signal model of the photo-thermal power generation is specifically as follows:
wherein DeltaX sg ＝[Δδ，Δω，ΔE' q ，ΔE' fd ]The state vector of a small signal model for photo-thermal power generation is represented by delta as a power angle, omega as a rotor rotating speed and E' q Is the quadrature axis transient electromotive force, E' fd Is the dynamic value of the passive voltage regulator; deltaV sg ＝[ΔV x ,ΔV y ] T Is light and heat generatedInput vector of electric small signal model, V sg For the terminal voltage of synchronous generator, V x 、V y Respectively the components of the voltage of the machine terminal under xy coordinates, delta I sg ＝[ΔI x ,ΔI y ] T Output vector of small signal model for photo-thermal power generation, I sg Is the output current of the synchronous generator; i x And I y The components of the output current in the x coordinate and the y coordinate are respectively A sg A state matrix of a small signal model for photo-thermal power generation, B sg Input matrix of small signal model for photo-thermal power generation, C sg Output matrix D of small signal model for photo-thermal power generation sg A feed-forward matrix of a small signal model for photo-thermal power generation.
Optionally, the small signal model of the photovoltaic energy source is specifically as follows:
wherein DeltaX p ＝[ΔE f Δδ VSG Δω VSG ΔV dc ΔX] T State vector of small signal model of photovoltaic energy, E f For virtual synchronous machine output voltage delta VSG To output the voltage phase angle omega VSG Angular velocity, V, of internal potential of virtual synchronous machine VSG dc For the DC side voltage, deltaX is an intermediate variable, deltaX has an upper limit of 0, deltaU p ＝[ΔV gx ΔV gy ] T Input vector U of small signal model of photovoltaic energy p Voltage of grid-connected point of virtual synchronous machine, V gx 、V gy For the components of the grid-connected point voltage of the virtual synchronous machine under the x coordinate and the y coordinate, delta I p ＝[ΔI x ΔI y ] T Output vector of small signal model of photovoltaic energy, I p Injection current for virtual synchronous machine, I x And I y Respectively injecting components of current under xy coordinates for the virtual synchronous machine, A p State matrix of small signal model of photovoltaic energy source, B p Input matrix of small signal model for photovoltaic energy, C p Output matrix of small signal model of photovoltaic energy source, D p Is a feed-forward matrix of a small signal model of the photovoltaic energy source,
C dc is the capacitance value of the direct current side voltage stabilizing capacitor, V dc(0) Is the initial voltage value of the direct-current side voltage stabilizing capacitor, U oc Delta for open circuit voltage of photovoltaic cell VSG(0) 、I sc(0) 、V gx(0) 、V gy(0) 、V g(0) 、δ VSG(0) 、E f(0) 、I x(0) 、I y(0) Delta respectively VSG 、I sc 、V gx 、V gy 、V g 、δ VSG 、E f 、I x 、I y Initial value, X obtained after variable power flow calculation f For virtual synchronisationOutput voltage E of machine voltage f Point-to-virtual synchronous machine grid-connected point V g Reactance, omega n For the reference frequency of the power grid, J is the inertia constant of the VSG control link, D is the damping coefficient of the VSG control link, K is the voltage coefficient of the VSG control link, D q Reactive power coefficient K of VSG control link pv For P 'in VSG control' ref Proportional coefficient, K of control link PI controller iv For P 'in VSG control' ref Integral coefficient of control link PI controller, C 1 、C 2 Is an intermediate variable of the U-I equation of the photovoltaic cell.
Optionally, the small signal model of the wind power energy source is specifically as follows:
wherein DeltaX W State vector delta U of small signal model of wind power energy W ＝[ΔV gx-w ,ΔV gy-w ]Input vector U of small signal model of wind power energy W Grid-connected point voltage, V of PMSG-VSG gx-w 、V gy-w For the components of the grid-connected point voltage of the virtual synchronous machine under the x coordinate and the y coordinate, delta I W ＝[ΔI gx-w ,ΔI gy-w ] T Output vector of small signal model of wind power energy source, I W Injection current for PMSG-VSG, I gx-w 、I gy-w Injecting components of current in xy coordinates for a virtual synchronous machine, A W A state matrix of a small signal model of wind power energy, B W Input matrix of small signal model of wind power energy source, C W Output matrix D of small signal model of wind power energy W Is a feedforward matrix of a small signal model of wind power energy.
Optionally, determining, according to the state matrix and the sensitivity matrix, that each power generation energy region damps a region of the low-frequency oscillation of the new energy power system in each oscillation mode, where the damping is specifically as follows:
according to the formulaCalculating the region damping provided by each power generation energy region for low-frequency oscillation of the new energy power system;
wherein D is im Zone damping provided for the ith power generation zone to the new energy power system, S i,m For the sensitivity matrix of the mth modality to the ith power generation energy region,a torque matrix provided for the ith power generation energy region to the own region, S i-,m A sensitivity matrix for damping torque for the m-th oscillation mode to the non-i region; / >A torque matrix provided for the non-i region to the i-th region, S j,m Sensitivity matrix for the mth mode to the jth power generation energy region, +.>A torque matrix provided to the own region for the jth power generation energy region.
The invention also provides a system for determining the influence of the power generation energy source on the low-frequency oscillation of the power system, which comprises the following steps:
the small signal model building module is used for building a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle;
the state matrix module is used for determining a state matrix of the new energy power system model; the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy;
the sensitivity matrix module is used for determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system;
the damping calculation module is used for determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix;
And the position power determining module is used for determining the access position and the access power of each power generation energy source according to the regional damping.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a method and a system for determining the influence of power generation energy on low-frequency oscillation of an electric power system, wherein the method comprises the following steps: firstly, establishing a small signal model of each power generation energy source; the power generation energy sources comprise photo-thermal energy sources, thermal power energy sources, photovoltaic energy sources and wind power energy sources; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle; then, determining a state matrix of the new energy power system model; the new energy power system model is determined based on the small signal model of each power generation energy obtained by simulating grid connection of each power generation energy; determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system; determining the damping of each power generation energy region to the low-frequency oscillation region of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix; and finally, determining the access position and the access power of each power generation energy source according to the regional damping. The state matrix of the new energy power system model and the sensitivity matrix of damping torque of each power generation energy region established based on the small signal models of the photo-thermal energy source, the thermal power source, the photovoltaic energy source and the wind-electric energy source can determine the damping of each power generation energy region to the low-frequency oscillation region of the new energy power system under each oscillation mode, and the influence of different access positions and different access powers of each new energy source on the low-frequency oscillation of the power system can be analyzed by utilizing the damping of each region.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a low-frequency oscillation analysis method of an electric power system according to an embodiment of the present invention;
FIG. 2 is a photo-thermal field topology provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of a VSG control structure according to an embodiment of the present invention;
FIG. 4 is a power control diagram considering photovoltaic output characteristics according to an embodiment of the present invention;
FIG. 5 is a block diagram of a PMSG-VSG system provided by an embodiment of the present invention;
fig. 6 is a control block diagram of a machine side converter according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a new energy power system according to an embodiment of the present invention;
fig. 8 is a schematic view of area damping according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a method and a system for determining the influence of power generation energy on low-frequency oscillation of a power system, which can analyze the influence of multiple new energy grid connection on the low-frequency oscillation of the new energy power system.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in fig. 1, the present invention provides a method for determining the influence of a power generation energy source on low-frequency oscillation of an electric power system, comprising:
step 1: establishing a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle.
Step 2: determining a state matrix of a new energy power system model; and the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy.
Step 3: and determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system.
Step 4: and determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix.
Step 5: and determining the access position and the access power of each power generation energy source according to the regional damping.
In some embodiments, when modeling a small signal of a photo-thermal energy source, a photo-thermal power station mainly includes: the solar island light-gathering and heat-collecting system; a steam generation system, a turbo generator set and a heat storage system of a conventional island. In terms of structure and working principle, the conventional island of the photo-thermal power generation system is the same as a thermal power generating unit, belongs to the thermal power generating process, and is different in that the thermal power generating unit generates superheated steam by heating water working medium through combustion of fuel, the photo-thermal power generation collects solar heat energy through a condensation heat collection system, heats heat transfer working medium and generates superheated steam through a steam generating system. When only the low-frequency oscillation problem of the power system caused by the fact that the photo-thermal power station is connected to the power grid is researched, the model of the photo-thermal power generator set is not essentially different from the conventional thermal power, and a special model is not required to be established. The method researches the problem of low-frequency oscillation of the electric power system accessed by various new energy sources, so that the photo-thermal generator set adopts a small signal model which is the same as that of conventional thermal power. Therefore, a small signal model/thermal power small signal model of the photo-thermal energy source is established, and the method can be concretely as follows:
1) A simplified model commonly used for synchronous generators is determined, and the model is as follows:
in the formula (1), delta is a power angle, omega is a rotor rotating speed, omega 0 For synchronous rotation speed, M is the inertia constant of the rotor, D is the damping coefficient, P m For mechanical and electromagnetic power acting on the rotor E' q Is the quadrature axis transient electromotive force E q Is an empty electromotive force, E fd Is a forced no-load electromotive force.
2) A mathematical model of the automatic voltage regulator is determined, the model being as follows:
in the formula (2), K A For automatic voltage regulator gain, T A Gain time constant for automatic voltage regulator, V t And V ref For synchronizing the reference values of the terminal voltage signal and the extreme voltage of the generator, u pss Control signal for power system stabilizer PSS, E fd0 And E' fd Is a constant value of the exciting voltage and a dynamic value of the driven voltage regulator. P (P) e 、E q And V t Can be calculated from formula (3), specifically as follows:
in the formula (3), X d X is the direct axis synchronous reactance of the synchronous generator q For synchronous reactance of the quadrature axis, X' d Is a direct-axis transient reactance, V x 、V y 、I x And I y The components of the machine side voltage and the output current, respectively, in xy coordinates.
Specifically, V d 、V q 、I d And I q The components of the machine side voltage and the output current in the dq coordinate system can be calculated by the formula (4).
3) Linearizing the formulas (1) - (4) to obtain a photo-thermal power generation small signal model/a thermal power small signal model, wherein the model is as follows:
In formula (5), deltaX sg ＝[Δδ，Δω,ΔE' q ,ΔE' fd ]Is the state vector of the photo-thermal power generation small signal model, delta is the power angle, omega is the rotor rotating speed, E' q Is the quadrature axis transient electromotive force, E' fd Is the dynamic value of the passive voltage regulator; deltaV sg ＝[ΔV x ,ΔV y ] T Is the input vector of the photo-thermal power generation small signal model, V sg For the terminal voltage of synchronous generator, V x 、V y Respectively the components of the voltage of the machine terminal under xy coordinates, delta I sg ＝[ΔI x ,ΔI y ] T Is the output vector of the photo-thermal power generation small signal model, I sg Is the output current of the synchronous generator; i x And I y Respectively the components of the output current in xy coordinates, A sg A state matrix of a photo-thermal power generation small signal model, B sg Input matrix for photo-thermal power generation small signal model, C sg D is an output matrix of the photo-thermal power generation small signal model sg Is a feedforward matrix of a photo-thermal power generation small signal model.
However, the photo-thermal power generation capacity is small compared with the conventional thermal power generation unit, and a large photo-thermal power generation field generally includes a plurality of photo-thermal power generation units, and a plurality of photo-thermal power generation units are interconnected to a power system through a convergent network, so that the photo-thermal power generation field structure is as shown in fig. 1.
In some embodiments, the building of the small signal model of the photovoltaic energy source may specifically be as follows:
when a small signal model of the photovoltaic energy source is established, a photovoltaic cell model, a capacitor model, a grid-side converter and a control model thereof need to be established.
1) The photovoltaic cell model can be established specifically as follows:
because the photovoltaic power generation is controlled by a virtual synchronous machine (virtual synchronous gengrators, VSG), and the application of the VSG technology ensures that the photovoltaic power generation not only maintains the characteristics of a power electronic interface power supply, but also has the characteristics similar to a generator rotor, in the system stability research, a practical engineering photovoltaic cell model is often adopted, and the U-I equation of the photovoltaic cell under the non-standard condition is as follows:
in the formula (6), I sc For short-circuit current, U oc Is an open circuit voltage, I m And U m Is the current and voltage at the maximum power operating point.
2) The capacitor model can be built specifically as follows:
since the capacitor functions to stabilize the dc side voltage of the photovoltaic inverter, the capacitor model is as follows:
wherein C is dc Is the capacitance value of the direct current voltage stabilizing capacitor, V dc For DC side voltage, I pv For photovoltaic cell flow to intermediate capacitor current, P e Is the active power from the dc voltage stabilizing capacitor to the inverter.
3) The network-side converter and the control model thereof can be established as follows:
the primary topology circuit of the photovoltaic virtual synchronous machine shown in fig. 2 is characterized in that the network side converter is controlled by VSG, and the converter switching is controlled after the VSG output voltage control signal is subjected to pulse width modulation. Considering that the electromechanical characteristics are main research objects, the high-frequency links such as converter switching and the like are ignored in analysis, and the dynamic equation of the VSG control link can be as follows:
In the formula (8), ω VSG Angular velocity, delta, of the internal potential of the VSG VSG To output the voltage phase angle omega n For the reference frequency of the power grid, P ref And Q ref The control signals are respectively a virtual synchronous machine control signal and a reactive power control signal, J is an inertia constant of a virtual synchronous machine control link, D is a damping coefficient, K is a voltage coefficient and E f For virtual synchronous machine output voltage, V g And the grid-connected point voltage of the virtual synchronous machine is obtained.
Wherein P is e And Q e The active power and the reactive power are output for the converter respectively, and can be calculated by the following formula:
however, conventional VSG control is mainly designed for energy storage batteries on the dc side, i.e., constant voltage sources with infinite capacity on the dc side, but the dynamic characteristics of photovoltaic cells are more complex. The output range of the photovoltaic cell is [0, P max ]And has a stable operating region and an unstable operating region. As shown in fig. 4, the VSG control taking into account the dynamic characteristics of the photovoltaic cells should ensure its stable operation in a region, thus limiting the output power of the VSG control. VSG control segment P' ref And Q' ref The control equation for (2) is as follows:
in the formula (10), V dc-mpp For the corresponding DC voltage at the maximum power operating point of the photovoltaic cell, P max Is the maximum output power. The upper limit of DeltaX is set to 0 and the dynamic equation is K iv Is the integral coefficient of the PI controller.
4) Linearizing the PV-VSG dynamic model to obtain a small signal model of the photovoltaic energy, wherein the model is as follows:
in the formula (11), deltaX p ＝[ΔE f Δδ VSG Δω VSG ΔV dc ΔX] T State vector of small signal model of photovoltaic energy, E f For virtual synchronous machine output voltage delta VSG To output the voltage phase angle omega VSG Is the angular velocity of the internal potential of VSG, V dc The upper limit of DeltaX is 0 and DeltaU is the DC side voltage p ＝[ΔV gx ΔV gy ] T Input vector U of small signal model of photovoltaic energy p Voltage of grid-connected point of virtual synchronous machine, V gx 、V gy For the component of the virtual synchronous machine grid-connected point voltage under xy coordinates, delta I p ＝[ΔI x ΔI y ] T Output vector of small signal model of photovoltaic energy, I p Injection current for virtual synchronous machine, I x And I y Respectively injecting components of current under xy coordinates for the virtual synchronous machine, A p State matrix of small signal model of photovoltaic energy source, B p Input matrix of small signal model for photovoltaic energy, C p Output matrix of small signal model of photovoltaic energy source, D p Is a feed-forward matrix of a small signal model of the photovoltaic energy source.
Wherein C is dc Is the capacitance value of the direct current side voltage stabilizing capacitor, V dc(0) Is the initial voltage value of the direct-current side voltage stabilizing capacitor, U oc For open circuit voltage of photovoltaic cell, V gx(0) 、V gy(0) 、V g(0) 、δ VSG(0) 、E f(0) 、I x(0) 、I y(0) Is V (V) gx 、V gy 、V g 、δ VSG 、E f 、I x 、I y And (5) calculating an initial value obtained after variable power flow calculation. X is X f Representing virtual synchronous machine voltage output voltage (E f ) Point-to-virtual synchronous machine grid connection point (V) g ) Reactance between them. Omega n For the reference frequency of the power grid, J is the inertia constant of the VSG control link, D is the damping coefficient of the VSG control link, K is the voltage coefficient of the VSG control link, D q Reactive power coefficient K of VSG control link pv For P 'in VSG control' ref Proportional coefficient, K of control link PI controller iv For P 'in VSG control' ref Integral coefficient of control link PI controller, C 1 、C 2 Is a photovoltaic cell U-I equation parameter.
In some embodiments, a small signal model of the wind power source is built, which may be specifically as follows:
the direct-drive wind turbine mainly comprises a permanent magnet generator, a machine side converter and a grid side converter. As shown in fig. 4, the machine side converter adopts vector control, and the network side converter adopts virtual synchronous machine control.
When a small signal model of wind power energy is established, a permanent magnet generator model, a capacitor model, a machine side converter control model and a network side converter control model are required to be established.
(1) The permanent magnet generator model can be established specifically as follows:
in the formula (12), L sd And I sq Respectively the dq-axis component of the stator winding current, U sd And U sq Respectively the dq component of the rotor winding voltage, ω being the angular speed of the generator, L q And L d Respectively represent dq-axis components of stator inductances, ψ f Is the permanent magnetic flux of the rotor.
Specifically, the permanent magnet generator rotor is a single mass block model, and a rotor motion equation is as follows:
in the formula (13), D ω For damping coefficient, J w Is the inertia time constant of the motor, T ω And T e The mechanical torque and the electromagnetic torque of the generator rotor are respectively, np is pole pair number, omega 0 Is a rotor speed reference.
(2) The capacitor is used for stabilizing the direct-current side voltage of the wind turbine generator, and the capacitor model can be established as follows:
in the formula (14), C dc Is the capacitance value of the direct current voltage stabilizing capacitor, V dc Is a direct-current side voltage, P s For active power from the side converter to the capacitor, P g Is the active power from the capacitor to the grid-side inverter.
(3) The machine side converter control model can be established as follows:
the machine side converter adopts vector control, and the control target of the machine side converter is set to keep the direct current voltage stable so as to effectively utilize the kinetic energy of the rotor to provide the energy required by virtual inertia and damping. A block diagram of the machine side converter control model is shown in fig. 6. Direct current outer ring state quantity x is respectively introduced into a machine side converter control model 1 ，I sq Is the inner loop state quantity x of (2) 2 And I sd Is an inner loop intermediate variable state quantity x 3 The dynamic equation is:
in the formula (15), K i1 、K i2 And K i3 Integrating coefficients for PI controller, I sqref And I sdref Respectively stator winding current dq axis component reference values.
(4) The network-side converter control model can be established as follows:
the control target of the grid-side converter is set to inject the maximum power generated by the fan into the power grid. In the direct-drive wind turbine, a network-side converter is controlled by a virtual synchronous machine. And high-frequency links such as converter switching and the like are ignored in analysis. The dynamic equation of the VSG control method of the wind turbine generator is the same as that of photovoltaic power generation.
Linearizing the PMSG-VSG dynamic model to obtain a small signal model of wind and electric energy, wherein the model is as follows:
in formula (16), deltaX W State vector delta U of small signal model of wind power energy W ＝[ΔV gx-w ,ΔV gy-w ]Input vector U of small signal model of wind power energy W Grid-connected point voltage, V of PMSG-VSG gx-w 、V gy-w For the component of the virtual synchronous machine grid-connected point voltage under xy coordinates, delta I W ＝[ΔI gx-w ,ΔI gy-w ] T Output vector of small signal model of wind power energy source, I W Is PMInjection current of SG-VSG, I gx-w 、I gy-w The components of the current in xy coordinates are injected for the virtual synchronous machine. A is that W A state matrix of a small signal model of wind power energy, B W Input matrix of small signal model of wind power energy source, C W Output matrix D of small signal model of wind power energy W Is a feedforward matrix of a small signal model of wind power energy.
In this embodiment, the photo-thermal power generation small signal model, the thermal power small signal model, the photovoltaic energy small signal model and the wind power energy small signal model are represented in a matrix manner to obtain a new energy power system state matrix; the new energy power system state matrix comprises a power angle vector, a rotating speed variable vector and a residual state variable vector of the power generation motor, and is specifically as follows:
as shown in fig. 6, the new energy power system includes thermal power, wind power, photovoltaic power generation and photo-thermal power generation. Firstly, establishing a new energy power system small signal model by using a small signal model type (5), a formula (11), a formula (16) and a dynamic equation of a load in a system of simultaneous photo-thermal, photovoltaic, wind power and traditional thermal power to obtain a new energy power system state matrix, wherein the state matrix is shown as follows:
in the formula (17), delta is a power angle vector of the synchronous generator or the virtual synchronous machine, omega is a rotating speed vector of the generator or the virtual synchronous machine, and Z is a residual state variable vector.
In particular, the remaining state variable vector (Residual State Variable Vector) generally refers to a set of state variables that have not been measured or estimated during actual power system operation. These unmeasured or estimated state variables are typically estimated by modeling and state estimation algorithms of the power system.
Power systems typically include many parts and components such as generators, transformers, transmission lines, loads, and the like. Each part has its own physical and electrical parameters that affect the overall system characteristics and performance. Some of these parameters may be obtained by measurement and monitoring, but many of them cannot be measured directly or determined at all, such as the status of certain components, the impedance of certain lines, etc. In order to simulate, model, control and diagnose faults in a power system, these unknown parameters need to be estimated. In the state estimation algorithm, the unknown parameters are integrated together to form a residual state variable vector, and the residual state variable vector is solved by using an estimation mode. According to the system model and the state estimation algorithm, the state quantity of the unknown variable can be estimated by observing and processing the known input and output quantity of the power system and is presented in a vector form.
In some embodiments, steps 3-4 may be specifically as follows:
performing matrix decomposition and region-by-region expansion on the state matrix, and determining a power generation motor rotating speed variable, a first forward channel matrix and a second forward channel matrix of each power generation energy region; the first forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to the power generation energy source region; the second forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to any power generation energy source region except the power generation energy source region;
Determining a first damping torque matrix provided by the power generation energy region to the power generation energy region under each oscillation mode according to the power generation motor rotating speed variable of the power generation energy region, the first forward channel matrix and the oscillation mode of the new energy power system;
determining a second damping torque matrix provided by the power generation energy region to any power generation energy region except the power generation energy region in each oscillation mode according to the power generation motor rotation speed variable of the power generation energy region, the second forward channel matrix and the oscillation mode of the new energy power system;
calculating the regional damping provided by the power generation energy region to the low-frequency oscillation of the new energy power system under each mode according to the sensitivity matrix, the first damping torque matrix and the second damping torque matrix; the sensitivity matrix represents the influence capability of the power generation energy region on the mode.
The matrix decomposition and the area-wise expansion are performed on the state matrix, and a power generation motor rotation speed variable, a first forward channel matrix and a second forward channel matrix of each power generation energy area are determined, which may be specifically as follows:
dividing a power system into four power generation energy areas according to photo-thermal power generation, wind power, photovoltaic and traditional thermal power, and sequencing vectors according to the areas, namely delta omega= [ delta omega ] 1 Δω 2 Δω 3 Δω 4 ] T Wherein ω is i And (5) generating a rotational speed vector of the generator or the virtual synchronous machine for the ith power generation energy area.
Decomposing the formula (17) according to the state, wherein a state matrix of the decomposed new energy power system is as follows:
from the decomposed state matrix [ delta Z ]]＝(SI-A 33 ) -1 A 31 [Δδ]+(SI-A 33 ) -1 A 32 [Δω]Will [ delta Z ]]Substituted into (18) to obtainI.e. < ->In->S is a differential operator, and characteristic values of specific modes are substituted in calculation, and a vector omega is unfolded according to regions: />In the formula (25), ω i Is the rotational speed variable vector omega of the generator or the virtual synchronous machine in the region i i- Generator or virtual synchronous machine rotational speed variable vector in non-i region. G in matrix i,i Is i area directionFirst forward channel matrix of i-region generator or virtual synchronous machine electromechanical oscillation link, G i-,i And the second forward channel matrix is a non-i area-to-i area generator or virtual synchronous machine electromechanical oscillation link.
According to the rotation speed variable of the power generation motor of the power generation energy region, the first forward channel matrix and the oscillation modes of the new energy power system, a first damping torque matrix provided by the power generation energy region to the power generation energy region in each oscillation mode is determined, and the first damping torque matrix is specifically as follows:
according to the formulaDetermining a first damping torque matrix provided by the power generation energy source area to the target mode, wherein lambda is shown in the formula m Is the characteristic value of the m-th mode, +.>A torque matrix provided for the i region to the own region, G i,i And (3) a first forward channel matrix for the electromechanical oscillation link of the generator or the virtual synchronous machine from the i region (i.e. the i-th power generation energy region) to the i region.
The second damping torque matrix provided by the power generation energy region to any power generation energy region except the power generation energy region in each oscillation mode is determined according to the power generation motor rotation speed variable of the power generation energy region, the second forward channel matrix and the oscillation mode of the new energy power system, and specifically may be as follows:
according to the formulaDetermining a second damping torque matrix provided from a non-i region to an i region in the target mode, wherein lambda m Is the characteristic value of the m-th mode, +.>A torque matrix provided for the non-i region to the i region, G i-,i And the second forward channel matrix is a non-i area-to-i area generator or virtual synchronous machine electromechanical oscillation link.
According to the sensitivity matrix, the first damping torque matrix and the second damping torque matrix, calculating the area damping provided by the power generation energy area to the low-frequency oscillation of the new energy power system under each mode; the sensitivity matrix represents the influence capability of the power generation energy source region on the mode, and specifically can be as follows:
Specifically, a sensitivity matrix S of the mth oscillation mode to the damping torque of the ith region is defined i,m To evaluate the influence capability of the power generation energy region on the oscillation mode:
wherein S is i,m For the m-th mode sensitivity matrix to the i-region, lambda m Is the characteristic value of the mth oscillation mode, T i m Damping torque for the i-th power generation energy region.
Calculating the area damping provided by the power generation energy area to the low-frequency oscillation of the new energy power system under each oscillation mode according to a formula (20), wherein the formula (20) is as follows:
wherein D is im Zone damping provided to the power system for the ith zone, S i,m For the sensitivity matrix of the mth modality to the i-region,a torque matrix provided for the ith region to the own region, S i-,m A sensitivity matrix for damping torque for the m-th mode to the non-i region; />A torque matrix provided for the non-i region to the i-th region.
In particular, modal analysis is commonly used to analyze oscillation behavior and oscillation damping capabilities in a system. In oscillation analysis, damping torque is an important parameter describing the ability of the system to consume energy during oscillation. The damping torque can be calculated by the sensitivity index of each region to different oscillation modes. The sensitivity of the mode to the damping torque of the zones is thus the extent to which each zone contributes to the damping torque for a particular oscillation mode in the power system, and the magnitude of the damping torque contribution of each zone to the particular oscillation mode.
In an electrical power system, the magnitude of damping torque in a region may be affected by a variety of factors, such as power damping, motor inertia, load damping, and the like. Thus, there may be a large difference in sensitivity index of damping torque in different regions for different oscillation modes. By analyzing sensitivity indexes of damping torque of a modal pair region in the power system, engineers can be helped to better understand system oscillation behaviors, and the damping torque of the system is guided to be regulated so as to improve stability and reliability of the power system.
In some embodiments, after step 4, the method further includes adjusting access power or access location of each power generation energy source, which may specifically be as follows:
and (3) adjusting the access power of each power generation energy source for multiple times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system in each oscillation mode.
And determining the optimal access power of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple times of adjustment.
And (3) adjusting the access position of each power generation energy source for multiple times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system under each mode.
And determining the optimal access position of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple times of adjustment.
Because the damping of each power generation energy region to the low-frequency oscillation region of the new energy power system under each mode can be calculated according to the steps 1-4, after the damping provided by the power generation energy to the low-frequency oscillation different modes of the power system is calculated, the damping value provided by each power generation energy to the low-frequency oscillation different modes of the power system under the conditions of different access positions, access power, output ratio and the like is determined by more careful consideration. Therefore, more accurate data can be obtained, and the influence of different new energy access modes on the low-frequency oscillation of the power system can be further analyzed. Such an impact analysis is generally based on the magnitude of the damping value, since the larger the damping value, the smaller the probability of low frequency oscillations occurring.
Therefore, damping values of the new energy sources need to be compared to determine the optimal access position, the optimal access power and the optimal output ratio, so that the optimal control and management of the low-frequency oscillation of the power system are realized. For example, firstly, a system small signal model is established according to the determined parameters of the power system, and formulas used by different access systems (photo-thermal power generation, photovoltaic and wind power systems) are respectively formula (5), formula (11) and formula (16). The state matrix, that is, the matrix shown in the formula (17), is then obtained by the models of the formula (5), the formula (11), and the formula (16). For this model, a formula calculation according to formulas (18) - (20) is required, including calculating the damping value provided by each region to each oscillation mode. Wherein equation (20) is used to calculate the damping provided by each region to each oscillation mode. After the damping provided by each area to each oscillation mode is calculated, the damping value is recalculated by changing the method of the access power or the access position of photo-thermal, wind power, photovoltaic and the like. And finally, analyzing the influence of the change of the access power or the access position of the photo-thermal power, the wind power and the like on the low-frequency oscillation of the system according to the calculated damping value. For example, when other conditions are kept unchanged and the photo-thermal power generation access power is gradually increased, the area damping provided by photo-thermal power generation is calculated to be increased and then reduced, namely, a local damping maximum value exists, and then the access power corresponding to the local damping maximum value is the optimal access power of photo-thermal power generation in the current scene; when other conditions are kept unchanged, changing the wind power access position from the power transmission end to the power receiving end, and calculating to obtain that the area damping provided by wind power is increased, wherein compared with the power transmission end, the power receiving end is a better access position of wind power in the current scene.
The invention also provides a system for determining the influence of the power generation energy source on the low-frequency oscillation of the power system, which comprises the following steps:
the small signal model building module is used for building a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle.
The state matrix module is used for determining a state matrix of the new energy power system model; and the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy.
And the sensitivity matrix module is used for determining the sensitivity matrix of the damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system.
And the damping calculation module is used for determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix.
And the position power determining module is used for determining the access position and the access power of each power generation energy source according to the regional damping.
In summary, the invention has the following advantages:
according to the method and the system for determining the influence of the power generation energy on the low-frequency oscillation of the power system, provided by the invention, the small signal model of the new energy power system accessed by photo-thermal power generation, wind power and photovoltaic is established, the sensitivity index of each area on each oscillation mode is defined, and the influence of multiple new energy grid connection such as photo-thermal power generation, wind power and the like on the low-frequency oscillation of the power system can be clearly and effectively quantitatively analyzed.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (10)
1. A method for determining the effect of a power generation energy source on low frequency oscillations of an electrical power system, comprising:
step 1: establishing a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle;
step 2: determining a state matrix of a new energy power system model; the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy;
step 3: determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system;
step 4: determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix;
step 5: and determining the access position and the access power of each power generation energy source according to the regional damping.
2. The method according to claim 1, wherein the steps 3-4 specifically include:
Performing matrix decomposition and region-by-region expansion on the state matrix, and determining a power generation motor rotating speed variable, a first forward channel matrix and a second forward channel matrix of each power generation energy region; the first forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to the power generation energy source region; the second forward channel matrix is a forward channel matrix of an electromechanical oscillation link of the generator motor from the power generation energy source region to any power generation energy source region except the power generation energy source region;
determining a first damping torque matrix provided by the power generation energy region to the power generation energy region under each oscillation mode according to the power generation motor rotating speed variable of the power generation energy region, the first forward channel matrix and the oscillation mode of the new energy power system;
determining a second damping torque matrix provided by the power generation energy region to any power generation energy region except the power generation energy region in each oscillation mode according to the power generation motor rotation speed variable of the power generation energy region, the second forward channel matrix and the oscillation mode of the new energy power system;
calculating the regional damping provided by the power generation energy region to the low-frequency oscillation of the new energy power system under each mode according to the sensitivity matrix, the first damping torque matrix and the second damping torque matrix; the sensitivity matrix represents the influence capability of the power generation energy region on the mode.
3. The determination method according to claim 2, characterized by further comprising:
according toCalculating the sensitivity matrix, wherein S i,m Sensitivity matrix of mth oscillation mode to ith power generation energy region, lambda m Is the characteristic value of the mth oscillation mode, T i m Damping torque for the i-th power generation energy region.
4. The method of determining according to claim 1, further comprising, after step 4:
adjusting the access power of each power generation energy source for multiple times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system in each oscillation mode;
and determining the optimal access power of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple adjustment.
5. The method of determining according to claim 1, further comprising, after step 4:
adjusting the access position of each power generation energy source for a plurality of times, and repeating the steps 1-4 to obtain the damping of each power generation energy source region to the low-frequency oscillation region of the new energy power system in each oscillation mode;
and determining the optimal access position of each power generation energy according to the region damping corresponding to each power generation energy region obtained through multiple times of adjustment.
6. The method according to claim 1, wherein the small signal model of photo-thermal power generation is as follows:
ΔI sg ＝C sg ΔX sg +D sg ΔV sg
wherein DeltaX sg ＝[Δδ，Δω，ΔE′ q ，ΔE′ fd ]The state vector of a small signal model for photo-thermal power generation is represented by delta as a power angle, omega as a rotor rotating speed and E' q Is the quadrature axis transient electromotive force, E' fd Is the dynamic value of the passive voltage regulator; deltaV sg ＝[ΔV x ,ΔV y ] T Input vector of small signal model for photo-thermal power generation, V sg For the terminal voltage of synchronous generator, V x 、V y Respectively the components of the voltage of the machine terminal under xy coordinates, delta I sg ＝[ΔI x ,ΔI y ] T Small letter for photo-thermal power generationOutput vector of model number, I sg Is the output current of the synchronous generator; i x And I y The components of the output current in the x coordinate and the y coordinate are respectively A sg A state matrix of a small signal model for photo-thermal power generation, B sg Input matrix of small signal model for photo-thermal power generation, C sg Output matrix D of small signal model for photo-thermal power generation sg A feed-forward matrix of a small signal model for photo-thermal power generation.
7. The method of determining according to claim 1, wherein the small signal model of the photovoltaic energy source is as follows:
ΔI p ＝C p ΔX p +D p ΔU p
wherein DeltaX p ＝[ΔE f Δδ VSG Δω VSG ΔV dc ΔX] T State vector of small signal model of photovoltaic energy, E f For virtual synchronous machine output voltage delta VSG To output the voltage phase angle omega VSG Angular velocity, V, of internal potential of virtual synchronous machine VSG dc For the DC side voltage, deltaX is an intermediate variable, deltaX has an upper limit of 0, deltaU p ＝[ΔV gx ΔV gy ] T Input vector U of small signal model of photovoltaic energy p Voltage of grid-connected point of virtual synchronous machine, V gx 、V gy For the components of the grid-connected point voltage of the virtual synchronous machine under the x coordinate and the y coordinate, delta I p ＝[ΔI x ΔI y ] T Output vector of small signal model of photovoltaic energy, I p Injection current for virtual synchronous machine, I x And I y Respectively injecting components of current under xy coordinates for the virtual synchronous machine, A p State matrix of small signal model of photovoltaic energy source, B p Input matrix of small signal model for photovoltaic energy, C p Small signal as photovoltaic energy sourceOutput matrix of model, D p Is a feed-forward matrix of a small signal model of the photovoltaic energy source,
C dc is the capacitance value of the direct current side voltage stabilizing capacitor, V dc(0) Is the initial voltage value of the direct-current side voltage stabilizing capacitor, U oc Delta for open circuit voltage of photovoltaic cell VSG(0) 、I sc(0) 、V gx(0) 、V gy(0) 、V g(0) 、δ VSG(0) 、E f(0) 、I x(0) 、I y(0) Delta respectively VSG 、I sc 、V gx 、V gy 、V g 、δ VSG 、E f 、I x 、I y Initial value, X obtained after variable power flow calculation f Output voltage E for virtual synchronous machine f Point-to-virtual synchronous machine grid-connected point V g Reactance, omega n For the reference frequency of the power grid, J is the inertia constant of the VSG control link, D is the damping coefficient of the VSG control link, K is the voltage coefficient of the VSG control link, D q Reactive power coefficient K of VSG control link pv For P in VSG control r ' ef Proportional coefficient, K of control link PI controller iv For P in VSG control r ' ef Integral coefficient of control link PI controller, C 1 、C 2 Is an intermediate variable of the U-I equation of the photovoltaic cell.
8. The method of determining according to claim 1, wherein the small signal model of the wind power energy source is as follows:
ΔI W ＝C W ΔX W +D W ΔU W
wherein DeltaX W State vector delta U of small signal model of wind power energy W ＝[ΔV gx-w ,ΔV gy-w ]Input vector U of small signal model of wind power energy W Grid-connected point voltage, V of PMSG-VSG gx-w 、V gy-w For the components of the grid-connected point voltage of the virtual synchronous machine under the x coordinate and the y coordinate, delta I W ＝[ΔI gx-w ,ΔI gy-w ] T Output vector of small signal model of wind power energy source, I W Injection current for PMSG-VSG, I gx-w 、I gy-w Injecting components of current in xy coordinates for a virtual synchronous machine, A W A state matrix of a small signal model of wind power energy, B W Input matrix of small signal model of wind power energy source, C W Output matrix D of small signal model of wind power energy W Small signal model for wind power energyIs a feed forward matrix of (a).
9. The method according to claim 1, wherein determining, according to the state matrix and the sensitivity matrix, the damping of each power generation energy region to the region of the new energy power system low-frequency oscillation in each oscillation mode is specifically as follows:
According to the formulaCalculating the region damping provided by each power generation energy region for low-frequency oscillation of the new energy power system;
wherein D is im Zone damping provided for the ith power generation zone to the new energy power system, S i,m For the sensitivity matrix of the mth modality to the ith power generation energy region,a torque matrix provided for the ith power generation energy region to the own region, S i-,m A sensitivity matrix for damping torque for the m-th oscillation mode to the non-i region; />A torque matrix provided for the non-i region to the i-th region, S j,m Sensitivity matrix for the mth mode to the jth power generation energy region, +.>A torque matrix provided to the own region for the jth power generation energy region.
10. A system for determining the effect of a source of generated energy on low frequency oscillations of an electrical power system, comprising:
the small signal model building module is used for building a small signal model of each power generation energy source; the power generation energy sources comprise a photo-thermal energy source, a thermal power energy source, a photovoltaic energy source and a wind power energy source; the small signal model of the photo-thermal energy source is built based on the thermal power generation principle;
the state matrix module is used for determining a state matrix of the new energy power system model; the new energy power system model is determined based on a new energy power system obtained by simulating grid connection of each power generation energy and a small signal model of each power generation energy;
The sensitivity matrix module is used for determining a sensitivity matrix of damping torque of each power generation energy area under each oscillation mode according to the state matrix and the oscillation mode of the new energy power system;
the damping calculation module is used for determining the damping of each power generation energy area to the low-frequency oscillation area of the new energy power system under each oscillation mode according to the state matrix and the sensitivity matrix;
and the position power determining module is used for determining the access position and the access power of each power generation energy source according to the regional damping.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108667048A (en) * | 2018-05-31 | 2018-10-16 | 清华大学 | The frequency domain of new energy grid connection system oscillatory stability sentences steady method and device |
| CN110569577A (en) * | 2019-08-26 | 2019-12-13 | 清华大学 | Frequency domain mode method-based sub-synchronous oscillation tracing method and system for new energy system |
| CN111478364A (en) * | 2020-04-20 | 2020-07-31 | 郑州轻工业大学 | Damping controller coordination parameter optimization method based on steepest descent method |
| CN112202211A (en) * | 2020-10-10 | 2021-01-08 | 华北电力大学 | Multi-VSG grid-connected power frequency oscillation evaluation method based on modal analysis method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108667048A (en) * | 2018-05-31 | 2018-10-16 | 清华大学 | The frequency domain of new energy grid connection system oscillatory stability sentences steady method and device |
| CN110569577A (en) * | 2019-08-26 | 2019-12-13 | 清华大学 | Frequency domain mode method-based sub-synchronous oscillation tracing method and system for new energy system |
| CN111478364A (en) * | 2020-04-20 | 2020-07-31 | 郑州轻工业大学 | Damping controller coordination parameter optimization method based on steepest descent method |
| CN112202211A (en) * | 2020-10-10 | 2021-01-08 | 华北电力大学 | Multi-VSG grid-connected power frequency oscillation evaluation method based on modal analysis method |
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