CN116054171A - Wind-solar-storage direct-current micro-grid voltage self-adaptive control method and device - Google Patents
Wind-solar-storage direct-current micro-grid voltage self-adaptive control method and device Download PDFInfo
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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
- H02J3/381—Dispersed generators
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- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention provides a wind-solar-storage direct-current micro-grid voltage self-adaptive control method and device, and belongs to the field of direct-current micro-grids. Wherein the method comprises the following steps: establishing a virtual synchronous machine-like control equation for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid; the method comprises the steps of determining an adjusting range of an equivalent virtual capacitor and a virtual damping coefficient of a DC/AC converter controlled by a quasi-virtual synchronous machine by converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation; based on the adjustment range, the DC/AC converter and the equivalent virtual capacitance and virtual damping coefficient of the DC/DC converter are adaptively adjusted according to the voltage dynamic response condition and the capacity limit of the DC/AC converter. The invention can effectively improve the voltage quality, improve the stability of a new energy grid-connected system and effectively prolong the service life of the grid-connected converter in the voltage control of the wind-solar storage direct-current micro-grid.
Description
Technical Field
The invention belongs to the field of direct current micro-grids, and particularly relates to a wind-solar storage direct current micro-grid voltage self-adaptive control method and device.
Background
In order to cope with the energy crisis, the development and utilization of renewable energy sources such as wind energy, photovoltaic and the like with the advantages of abundant reserves, cleanness and no pollution are rapidly developed. The direct-current micro-grid constructed by the distributed energy and the energy storage unit can effectively realize comprehensive utilization of the energy, and the running and control of the direct-current system are not influenced by frequency and power angle, so that the electric energy quality and the power supply reliability can be effectively improved. The stability of the voltage of the direct current bus is the only standard for the stability of the direct current power grid, so that the ensuring of the constant voltage of the direct current bus is important.
The direct current micro-grid is a low-inertia network based on a power electronic device, abrupt fluctuation of direct current bus voltage can be caused by abrupt change of output power of an energy source side, switching of load and the like, and the direct current micro-grid is more serious in a high-power direct current system, so that the safety and stability of grid operation are directly jeopardized. Although the traditional droop control can quickly respond to voltage fluctuation, the voltage fluctuation is regulated in a differential mode, the larger the output power is, the larger the voltage deviation is caused, and the bus voltage still fluctuates severely under larger power disturbance due to the typical characteristic of small inertia and weak damping of a direct current power grid.
Therefore, if the virtual synchronous machine technology (virtual synchronous generator, VSG) widely applied to the alternating current power grid can be analogized, and the virtual inertia control is applied to the grid-connected converter of the direct current power grid, the direct current voltage mutation can be effectively restrained. Therefore, a learner has proposed a virtual synchronous machine-like control method (Analogous virtual synchronous generator, AVSG) for dc voltage control to enhance the inertia of the dc micro-grid and stabilize the bus voltage fluctuation. In AVSG control, the most critical parameters are virtual inertia and damping coefficients, and transient stability of the system can be improved by adjusting control parameters. However, the new energy output has randomness, and under the fluctuation of the power output of the power supply side, the fixed virtual inertia parameter cannot achieve the optimal control effect, so that the research of the self-adaptive control of the virtual inertia and damping parameters is significant.
At present, the voltage control method of the wind-solar energy storage power generation system at home and abroad has more researches, but has the defects, and the method is mainly characterized by the following two points:
1. there is no consideration to control the problem of voltage regulation static difference
The conventional AVSG control outer loop often adopts droop control, which has a static difference of voltage regulation, and in a high-power direct-current micro-grid, the problem is more remarkable.
2. Capacity limitations of the converters and coordination between the converters are not considered.
The prior virtual inertial control is mainly aimed at a single converter, and the voltage regulation capability of the multi-terminal converter is not fully utilized; the adaptive control is mainly focused on the deviation amount and the change rate of the direct current voltage, and the capacity of the converter and the coordination among the multiple converters are not considered, so that the long-term safe operation of the power electronic device is not facilitated.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a wind-solar-storage direct-current micro-grid voltage self-adaptive control method and device. The invention eliminates the static difference of direct current voltage through a voltage compensation link; the method and the device simultaneously consider the influence of voltage change and converter output power limitation in parameter self-adaptive control, can be applied to voltage control of a wind-solar storage direct-current micro-grid, effectively improve voltage quality, improve stability of a new energy grid-connected system, and simultaneously ensure that the grid-connected converter does not exceed the power limitation as much as possible in the running process, and prolong the service life of the grid-connected converter.
An embodiment of a first aspect of the present invention provides a method for adaptively controlling voltage of a wind-solar-storage direct-current micro-grid, including:
respectively establishing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, wherein the control equations comprise a voltage compensation link, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
Converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation, and performing root locus diagram drawing to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
based on the adjusting range, the equivalent virtual capacitance and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter are adaptively adjusted according to the voltage dynamic response condition and the capacity limit of the DC/AC converter, so as to realize the adaptive control of the wind-solar storage direct current micro-grid voltage.
In a specific embodiment of the present invention, the expression of the virtual synchronous machine-like control equation of the DC/AC converter is as follows:
wherein i is dc Injecting current into the direct current micro-grid for the DC/AC converter; i.e out The output direct current of the DC/AC converter; d (D) v Virtual damping coefficients for the DC/AC converter; c (C) v An equivalent virtual capacitance for the DC/AC converter; u (u) dcref Is a DC/AC converterA DC bus voltage reference value; u (U) n Rated voltage of the direct current bus;
wherein i is out ＝K p (U n -u dc )，K p For droop control factor, u dc The output voltage is the DC side.
In a specific embodiment of the present invention, the expression of the virtual synchronous machine-like control equation of the DC/DC converter is as follows:
Wherein i is b Inputting current to the DC/DC converter; i.e b_dc A current flowing into a DC bus for the DC/DC converter; c (C) vb2 An equivalent virtual capacitance of the DC/DC converter; d (D) vb2 Virtual damping coefficient of DC/DC converter; u (u) dcrefb2 A voltage reference is output for the DC/DC converter.
In a specific embodiment of the present invention, the expression of the virtual synchronous machine-like control small signal equation of the DC/AC converter is as follows:
wherein s is a differential operator; Δi dc (s) is a DC current increment; deltau dcref And(s) is a DC voltage increment.
In a specific embodiment of the present invention, the determining the adjustment range of the virtual damping coefficient and the equivalent virtual capacitance of the DC/AC converter controlled by the virtual synchronous machine includes:
according to the virtual synchronous machine-like control small signal equation, the DC bus voltage disturbance quantity delta u is obtained respectively dc D-axis current disturbance Δi d D-axis voltage disturbance delta u d DC disturbance quantity delta i dc The relation between the two is:
in U dc 、I dc Rated operating voltage and rated operating current respectively; c is a direct-current side voltage stabilizing capacitor; u (U) d Is the steady-state value of the d-axis voltage component at the network side, I d The steady-state value of the d-axis current component at the network side is obtained;
let Δi dref The controller of the current loop adopts a PI regulator, G i (s)＝k pi +k ii The small signal equation for the d-axis current component obtained by/s is:
wherein k is pi Is the proportionality coefficient, k of the current loop controller ii Is the integral coefficient of the current loop controller, L 1 And r are respectively a grid side filter inductor and a series resistor thereof;
the voltage compensation link adopts PI regulator and G 0 (s) represents G 0 (s)＝k p0 +k i0 And/s, the control equation of the compensation voltage is as follows:
(U n -u dc )G 0 (s)＝u dcref (6)
wherein k is p0 For scaling factor, k, of regulator in voltage compensation link i0 The integral coefficient of the regulator in the voltage compensation link;
by Deltau dc And Deltau dcref The method comprises the steps of respectively representing the disturbance quantity of the DC bus voltage and the disturbance quantity of a DC voltage reference value, and obtaining after Laplacian transformation of a control equation of the compensation voltage:
obtaining the DC side output voltage disturbance delta u according to formulas (3), (4), (5) and (7) dc (s) disturbance amount Deltai with output current dc The closed loop transfer function between(s) is:
wherein a=k p +D v 、m＝k pi k iv +k ii k pv ，
Wherein k is pwm Equivalent amplification gain for bridge voltage; k (k) pv 、k iv For the voltage outer loop PI regulator parameter, a i And b j Are all intermediate parameters i=1, …,5,j =1, …,6;
by performing stability analysis on the formula (8), G(s) is plotted on the virtual capacitance C v Pole profile under variation and G(s) at virtual damping D v Pole distribution diagram under variation, then respectively drawing C v 、D v Root trace of G(s) at change to determine C v 、D v Is a range of values.
In a specific embodiment of the present invention, the voltage dynamic response condition includes 4 phases:
stage 1: when the voltage change rate du of the direct current bus dc /dt>0, and voltage deviation Deltau>At 0, the virtual capacitance C of the DC/AC converter is increased by correlating the magnitude of the voltage change rate v And virtual capacitor C of DC/DC converter vb2 To reduce the voltage change rate and the virtual damping coefficient D of the DC/AC converter according to the magnitude of the voltage deviation v The response speed of the system is improved, and the voltage overshoot is reduced;
stage 2: when the voltage change rate du of the direct current bus dc /dt<0 and voltage deviation Deltau>At 0, C is reduced according to the magnitude of the voltage change rate v And C vb2 So that the voltage is restored to a stable value, D is increased according to the magnitude of the voltage deviation v To accelerate the decay rate of the voltage;
stage 3: when the voltage change rate du of the direct current bus dc /dt<0 and voltage deviation Deltau<At 0, C is increased according to the voltage change rate v And C vb2 To reduce the voltage change rate and D according to the magnitude of the voltage deviation v To accelerate the voltage regulation speed;
stage 4: when the DC voltage change rate du dc /dt>0 and voltage deviation Deltau<At 0, C is reduced according to the magnitude of the voltage change rate v And C vb2 Increase D according to magnitude of voltage deviation v To smooth out voltage fluctuations.
In a specific embodiment of the present invention, the adaptively adjusting the equivalent virtual capacitance and the virtual damping coefficient corresponding to the DC/AC converter and the DC/DC converter, respectively, includes:
virtual capacitor C of DC/AC converter v And virtual capacitor C of DC/DC converter vb2 The relation of the adaptive control is as follows:
wherein C is 01 C is the virtual capacitance initial value of the DC/AC converter 02 The virtual capacitance initial value of the DC/DC converter;
C vx to consider the virtual capacitance compensation value of the voltage response, C vy To take into account the compensation value of the virtual capacitance of the DC/AC converter capacity limitation, the expression is as follows:
wherein k is c1 、k c2 、k c3 As a virtual capacitance adjustment parameter, deltau is the deviation amount of the direct current voltage and the rated value; du/dt is the rate of change of the DC voltage; k (k) 1 Is a voltage change rate threshold; p is the output power of the DC/AC converter; p (P) N An upper power limit for the DC/AC converter;
virtual damping coefficient D of DC/DC converter vb2 ＝D 0 Virtual damping coefficient D of DC/AC converter v The adaptive adjustment is performed according to the dc voltage deviation amount as follows:
wherein D is 0 Is the initial value, k, of the virtual damping coefficient of the DC/AC converter d1 、k d2 For damping adjustment parameters, k 2 Is the voltage deviation amount threshold.
An embodiment of a second aspect of the present invention provides a wind-solar-storage dc micro-grid voltage adaptive control device, including:
the system comprises a virtual synchronous machine-like control equation construction module, a virtual synchronous machine-like control equation generation module and a virtual synchronous machine control module, wherein the virtual synchronous machine-like control equation construction module is used for respectively constructing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, the control equations comprise voltage compensation links, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
the control parameter adjusting range determining module is used for performing root locus diagram drawing by converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation so as to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
and the self-adaptive adjusting module is used for self-adaptively adjusting the equivalent virtual capacitor and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter according to the voltage dynamic response condition and the capacity limit of the DC/AC converter based on the adjusting range so as to realize the self-adaptive control of the wind-solar storage direct current micro-grid voltage.
An embodiment of a third aspect of the present invention provides an electronic device, including:
at least one processor; and a memory communicatively coupled to the at least one processor;
the memory stores instructions executable by the at least one processor, and the instructions are configured to perform the wind-solar direct current micro-grid voltage adaptive control method.
An embodiment of a fourth aspect of the present invention provides a computer readable storage medium, where the computer readable storage medium stores computer instructions, where the computer instructions are configured to cause the computer to execute the foregoing method for adaptively controlling a voltage of a wind-solar storage dc micro-grid.
The invention has the characteristics and beneficial effects that:
1) The invention adds a voltage compensation link in the traditional control, can realize the dead regulation of the busbar voltage of the direct current power grid, and improves the system stability problem caused by voltage deviation.
2) In the parameter self-adaptive adjustment, the invention enables the control parameters to simultaneously respond to the voltage dynamic adjustment rule and the available capacity of the converter, and can stabilize the voltage fluctuation and simultaneously give consideration to the long-term safe operation of the converter, thereby prolonging the service life of the converter to a certain extent.
3) The invention can be applied to the voltage control of the wind-solar storage direct-current micro-grid, solves the problem that the new energy source does not have voltage regulation capability due to the characteristics of low inertia and weak damping, can effectively improve the voltage quality through the control, improves the stability of a new energy source grid-connected system, simultaneously ensures that the power limit of the grid-connected converter is not exceeded as much as possible in the running process, and prolongs the service life of the grid-connected converter.
Drawings
Fig. 1 is an overall flowchart of a voltage adaptive control method for a wind-solar direct-current micro-grid according to an embodiment of the present invention.
FIG. 2 is a graph of G(s) pole distribution at different virtual damping in an embodiment of the present invention.
FIG. 3 is a graph of G(s) pole distribution at different virtual capacitances in an embodiment of the invention.
FIG. 4 is a simulation of the system operating characteristics during a sudden increase in illumination intensity in one embodiment of the invention.
FIG. 5 is a simulation of the system operating characteristics during a sudden load increase in an embodiment of the present invention.
FIG. 6 is a simulation diagram of the system operating characteristics with the addition of a voltage compensation link in an embodiment of the present invention.
Fig. 7 is a simulation diagram of the system operating characteristics under adaptive control taking into account the capacity of the converter in one embodiment of the invention.
Detailed Description
The invention provides a wind-solar direct-current micro-grid voltage self-adaptive control method and device, and the technical scheme in the embodiment of the invention is clearly and completely described below by combining specific embodiments and drawings. 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 fall within the scope of the invention.
An embodiment of a first aspect of the present invention provides a method for adaptively controlling voltage of a wind-solar-storage direct-current micro-grid, including:
respectively establishing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, wherein the control equations comprise a voltage compensation link, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation, and performing root locus diagram drawing to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
Based on the adjusting range, the equivalent virtual capacitance and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter are adaptively adjusted according to the voltage dynamic response condition and the capacity limit of the DC/AC converter, so as to realize the adaptive control of the wind-solar storage direct current micro-grid voltage.
In a specific embodiment of the present invention, the method for adaptively controlling voltage of a wind-solar direct current micro-grid, the overall flow is shown in fig. 1, includes the following steps: :
1) Establishing an AVSG control model;
in order to realize the cooperative control of the direct current power grid, the DC/AC converter (direct current-alternating current converter) adopts voltage-current droop control in the embodiment of the invention, and then the direct current side of the DC/AC converter outputs current i out The control equation of (2) is i out ＝K p (U n -u dc ) Wherein K is p For sag control factor, U n Rated for DC bus voltage, u dc The output voltage is the DC side.
The AVSG control equation applicable to the grid-connected DC/AC converter in the direct current micro-grid is constructed as follows:
wherein i is dc Injecting current into the direct current micro-grid for the DC/AC converter; i.e out The output direct current of the DC/AC converter; d (D) v Virtual damping coefficients for the DC/AC converter; c (C) v An equivalent virtual capacitance for the DC/AC converter; u (u) dcref A DC/AC converter DC bus voltage reference value; u (U) n Rated voltage of the direct current bus; t is time.
The AVSG control equation for constructing the DC/DC converter (DC converter) is as follows:
wherein i is b Inputting current to the DC/DC converter; i.e b_dc A current flowing into a DC bus for the DC/DC converter; c (C) vb2 An equivalent virtual capacitance of the DC/DC converter; d (D) vb2 Virtual damping coefficient of DC/DC converter; u (u) dcrefb2 A voltage reference is output for the DC/DC converter.
Since the input current reference value in the AVSG control is obtained by droop control, and the droop control is regulated in a differential way, steady-state errors exist when the control is used for regulating the voltage of the direct current bus, the initial voltage value cannot be recovered after dynamic regulation, and in a direct current power grid with a larger power level, the voltage deviation is more obvious, and the normal operation of the load is possibly influenced. In order to eliminate the static difference of the direct current bus, the embodiment adds a voltage compensation link in the traditional AVSG control, and a PI regulator is adopted as a compensator.
2) Based on the step 1), a control equation of the DC/AC converter is established, and an adjusting range of an equivalent virtual capacitor and a virtual damping coefficient controlled by the virtual synchronous machine is determined.
In the present embodiment, the DC-side output voltage u of the DC/AC converter, which is a state variable in the AVSG control equation shown in the formula (1) dc Output current i dc And (3) rewriting the DC/AC converter into a mode of adding steady-state quantity and small disturbance, linearizing the DC/AC converter near a steady-state point, ignoring disturbance items of 2 nd order or more, and carrying out Laplace transformation to obtain an AVSG control small signal equation of the DC/AC converter, wherein the AVSG control small signal equation is as follows:
wherein s is a differential operator; Δi dc (s) is a DC current increment; deltau dcref And(s) is a DC voltage increment.
In this embodiment, the current inner loop uses dq-axis decoupling control and operates at unity power factor, and therefore, the current inner loop q-axis current component i q By power balance, the DC bus voltage disturbance quantity Deltau can be obtained respectively dc D-axis current disturbance Δi d D-axis voltage disturbance delta u d DC disturbance quantity delta i dc The relation between the two is:
in U dc 、I dc Rated operating voltage and rated operating current respectively; c is a direct-current side voltage stabilizing capacitor; u (U) d Is the steady-state value of the d-axis voltage component at the network side, I d Is the net side d-axis current component steady state value.
Let Δi dref The controller of the current loop adopts a PI regulator G to represent the disturbance quantity of the d-axis current reference value i (s)＝k pi +k ii S, where k pi Is the proportionality coefficient, k of the current loop controller ii The small signal equation for obtaining the d-axis current component is as follows, wherein s is the integral coefficient of the current loop controller and s is the differential operator:
wherein L is 1 And r are the grid side filter inductance and the series resistance thereof respectively.
In this embodiment, the grid-connected control is composed of a voltage outer loop control and a current inner loop control. The improved AVSG designed in this embodiment is controlled as the controller on the voltage outer ring; the current inner loop adopts dq decoupling control, namely, the current is decomposed to two coordinate axes, wherein a PI regulator is adopted by a controller of the current inner loop, and the q-axis current component is 0, so that only the d-axis current component equation is analyzed.
The voltage compensation link adopts PI regulator and G 0 (s) represents G 0 (s)＝k p0 +k i0 S, where k p0 For scaling factor, k, of regulator in voltage compensation link i0 And (3) for the integral coefficient of the regulator in the voltage compensation link, s is a differential operator, and the control equation of the compensation voltage is as follows:
(U n -u dc )G 0 (s)＝u dcref (6)
by Deltau dc And Deltau dcref Control method for compensating voltage by respectively representing DC bus voltage disturbance and DC voltage reference value disturbanceThe process is obtained after Laplace transformation:
according to formulas (3), (4), (5) and (7), the series resistance of the filter inductor is ignored to obtain the DC side output voltage disturbance delta u dc (s) disturbance amount Deltai with output current dc The closed loop transfer function between(s) is:
wherein a=k p +D v 、m＝k pi k iv +k ii k pv ，
Wherein k is pwm Equivalent amplification gain for bridge voltage; k (k) pv 、k iv For the voltage outer loop PI regulator parameter, a i And b j Are all intermediate parameters i=1, …,5,j =1, …,6.
Stability analysis was performed on formula (8). First, G(s) is given in the virtual capacitance C v Pole profile under variation and G(s) at virtual damping D v Pole distribution diagram under variation, then respectively drawing C v 、D v Root trace of G(s) at change for determining C v 、D v Is selected in a range such that C v 、D v The stable operation of the system is not affected in the subsequent self-adaptive adjustment process.
FIG. 2 shows a virtual damping parameter D according to an embodiment of the present invention v Pole profile of G(s) at increasing from 100 to 800, indicated by arrow D v The direction of movement of the pole of G(s) at increasing time, the abscissa and ordinate in FIG. 2 represent the real part sigma and imaginary part omega, respectively, of the pole, and the symbol "X" in the figure represents D v The pole is located at each point of increase. As can be seen from FIG. 2, D v The larger the pole that changes (i.e., the pole on the real axis) is, the further from the imaginary axis the system stability is enhanced.
FIG. 3 is a graph of G(s) pole distribution at different virtual capacitances in an embodiment of the invention. Wherein FIG. 3 (a) is C v Pole profile of G(s) increasing from 1 μf to 60 μf, fig. 3 (b) C v Pole profile of G(s) increasing from 50 to 2000 uf. As can be seen from FIG. 3 (a), at C v During the increasing process, 1 pole of the change gradually approaches to the virtual axis, the system stability is reduced, the rest poles are less changed and are all in the left half plane, as shown in fig. 3 (b), when the virtual capacitor C v Further increasing, 1 pair of conjugate pole points will enter the right half plane, the system is unstable.
C v 、D v The parameter size of (2) will affect the stability of the system, each parameter setting corresponds to a pole in the graph, i.e. "X" in the graph, when the system is unstable, "X" will be on the right half plane of the graph, so C needs to be determined v 、D v The selection range of the parameter is that the stable operation of the system is not affected in the subsequent self-adaptive adjustment process, namely, the parameter setting is to keep 'X' at the left half plane of the figure.
From the above stability analysis, it can be seen that with the virtual damping parameter D v The system stability is improved, and therefore, in the adaptive control of the present embodiment, D is set v And is larger than 100, and a certain stability margin is ensured. But with C v Increase, decrease in stability of system, C v When the voltage is too large, the stability is even lost, so that in order to ensure the stable operation of the system, the size of the virtual capacitor should be limited in AVSG self-adaptive control, and the virtual capacitor should satisfy the following conditions in the adjustment process:
3) And (5) adaptively adjusting the control parameters.
In this embodiment, the adaptive adjustment control parameter includes: adaptively adjusting control parameters based on voltage dynamic response and adaptively adjusting control parameters based on converter capacity limits
Wherein, the self-adaptive adjustment control parameter according to the voltage dynamic response includes:
as can be seen from the virtual inertial control equations (1) and (2), the dc bus voltage deviation amount and the change rate can be changed by adjusting the magnitudes of the virtual capacitor and the virtual damper, thereby improving the dynamic response characteristics of the dc voltage. According to the fluctuation curve of the bus voltage after disturbance, the embodiment can divide the voltage change into the following 4 stages:
stage 1: DC bus voltage change rate du dc /dt>0, and voltage deviation Deltau>0, the virtual capacitance C of the DC/AC converter can be increased by correlating the magnitude of the voltage change rate v And virtual capacitor C of DC/DC converter vb2 To reduce the voltage change rate and increase the virtual capacitance C v Although the DC/AC converter can stabilize the voltage fluctuation, the response time of the system is prolonged, so that the virtual damping D of the DC/AC converter is reduced according to the magnitude of the voltage deviation v The response speed of the system is improved, and the voltage overshoot is reduced;
stage 2: DC bus voltage change rate du dc /dt<0 and voltage deviation Deltau>0, as the deviation amount gradually decreases, it is necessary to decrease C according to the magnitude of the voltage change rate v And C vb2 The voltage is restored to a stable value as soon as possible by increasing D according to the magnitude of the voltage deviation v The voltage attenuation speed is further increased;
stage 3: DC bus voltage change rate du dc /dt<0 and voltage deviation Deltau<0, the adjusting process is similar to the 1 st stage, the virtual inertia C is increased according to the voltage change rate v And C vb2 To reduce the voltage change rate and the virtual damping coefficient D according to the magnitude of the voltage deviation v To accelerate the voltage regulation speed;
stage 4: DC bus voltage change rate du dc /dt>0 and voltage deviation Deltau<0, the regulation process is similar to phase 2, C is reduced by correlating the magnitude of the voltage change rate v And C vb2 Increasing the virtual damping coefficient D according to the magnitude of the voltage deviation v Stabilizing the voltage fluctuation.
The adaptively adjusting control parameters according to the converter capacity limit includes:
the DC/AC converter bears a main voltage stabilizing task, and ensuring the normal operation of the DC/AC converter is important to maintaining the safety and stability of the system and the power balance. The capacity of the DC/AC converter limits the power output of the AC main network, if the DC/AC converter always outputs the exchange power with the maximum capacity, the service life of the converter may be affected, and when a large disturbance occurs in the system, the instantaneous output power may be too large, even reach the limit of itself, and switch to power-limited operation, thereby losing the voltage regulation capability. Therefore, in the virtual inertia adaptive control, the influence of the output power limit of the converter is considered, when the output power of the converter is closer to the upper limit, the virtual inertia value should be reduced along with the reduction of the residual capacity of the DC/AC converter, and meanwhile, the inertia of the DC/DC converter is increased by the same value so as to maintain the integral inertia level of the direct current power grid.
In particular, the virtual capacitance C of the DC/AC converter v And virtual capacitor C of DC/DC converter vb2 The relation of the adaptive control is as follows:
wherein C is 01 C is the virtual capacitance initial value of the DC/AC converter 02 The virtual capacitance initial value of the DC/DC converter; c (C) vx To consider the compensation value of the virtual capacitance of the voltage response, C vy To take into account the compensation value of the virtual capacitor of the capacity limitation of the DC/AC converter, the specific calculation formula is as follows:
wherein k is c1 、k c2 、k c3 For the virtual capacitance adjustment parameters, 10 are taken in this embodiment -6 1 and 1; Δu is the deviation between the dc voltage and the rated value; du/dt is the rate of change of the DC voltage; k (k) 1 Is a voltage change rate threshold; p is the output power of the DC/AC converter; p (P) N Is the upper power limit of the DC/AC converter.
The virtual damping coefficient of the DC/DC converter adopts a fixed value D vb2 ＝D 0 Virtual damping coefficient D of DC/AC converter v The adaptive adjustment is performed according to the dc voltage deviation amount as follows:
wherein D is 0 Is the initial value, k, of the virtual damping coefficient of the DC/AC converter d1 、k d2 For damping adjustment parameters, 0.0028 and 1 are taken in this embodiment; k (k) 2 Is the voltage deviation amount threshold.
The effect of the method according to the present invention will be described in detail with reference to simulation results of a specific embodiment.
In a specific embodiment of the invention, a basic model of the wind-solar energy storage system is built, wherein the wind power unit is connected to a direct current power grid through an AC/DC converter and a DC/DC converter. Which normally operates in a maximum power tracking (maximumpower point tracking, MPPT) mode to ensure maximum utilization of wind energy. The photovoltaic battery pack is integrated into a direct current power grid through a DC/DC converter, and generally operates in an MPPT mode, and can operate in a power reduction mode under special conditions. The energy storage unit is connected with the direct current bus through the bidirectional DC/DC converter by the storage battery, realizes charge and discharge control, and controls the direct current bus voltage together with the grid-connected converter when the system operates normally. The grid side adopts a grid-connected bidirectional DC/AC converter, and when the wind-solar direct-current power grid normally operates, the grid side and the storage battery side converter participate in voltage regulation together so as to maintain the voltage stability of a direct-current bus; when the output power of the grid-connected converter reaches the upper limit and the lower limit, the grid-connected converter is switched to operate in a current limiting mode. Simulation settings were performed according to the parameters shown in table 1.
Table 1 a system simulation parameter set table in one embodiment of the invention
1. Bus voltage fluctuation comparison under different control methods;
1) The illumination intensity is suddenly increased and simulated and compared;
In this embodiment, the system operates at rated load and constant wind speed, t=7s, the illumination intensity is suddenly increased from 600lx to 900lx, the busbar voltage is initially increased, and then is briefly adjusted to return to the initial value, so as to obtain a simulation curve as shown in fig. 4, wherein fig. 4 (a) is a schematic diagram of system power change, and fig. 4 (b) is a schematic diagram of busbar voltage change. As can be seen from fig. 4 (a), the illumination intensity suddenly increases at t=7s, while the wind speed and load power are unchanged; as can be seen from fig. 4 (b), at t=7s, since the output power of the energy source side suddenly increases, the voltage oscillates, and when only the conventional droop control is adopted, the adjustment time is longest, about 0.6s, the voltage fluctuation is most obvious, and the maximum voltage deviation reaches 22V; when fixed parameter AVSG control is adopted, voltage fluctuation is suppressed, and the maximum voltage deviation amount is 18V; by adopting the adaptive control method of the embodiment, the voltage fluctuation can be further suppressed, the voltage deviation amount is minimized, about 11V, and the adjustment time is shortened to 0.4s.
2) Load bump simulation comparison;
in this embodiment, when the wind speed and the illumination intensity are constant and t=7s, the load is suddenly increased from 5MW to 10MW, and a simulation curve is obtained as shown in fig. 5, where fig. 5 (a) is a schematic diagram of system power change and fig. 5 (b) is a schematic diagram of bus voltage change. As seen in fig. 5 (a), the load suddenly increased at t=7s, while the fan and photovoltaic output power were unchanged. As can be seen from fig. 5 (b), the voltage first drops when t=7s, then returns to the initial value after a short adjustment process, and the voltage adjustment time is longest and the overshoot is greatest by about 35v in a conventional droop control manner; when the fixed parameter AVSG control is adopted, the voltage regulating time is shortened, and the fluctuation amplitude is obviously reduced; when the parameter self-adaptive control is adopted, the voltage overshoot is minimum, about 13v, the voltage change rate is also minimum, and the voltage fluctuation is obviously restrained.
2. The voltage compensation link is used;
in this embodiment, when t=7s, the illumination intensity is increased from 600lx to 900lx, and a system operation characteristic simulation curve is obtained when a voltage compensation link is added, as shown in fig. 6, the dotted line is a parameter adaptive control without voltage compensation, the solid line is an adaptive control added to the voltage compensation link, where fig. 6 (a) is a schematic diagram of voltage change of a DC bus, and fig. 6 (b) is a schematic diagram of input power change of a DC/AC converter. As can be seen from fig. 6 (a), when t=7s, the voltage oscillates due to sudden increase of the illumination intensity, and when no voltage compensation is performed, the voltage is recovered and stabilized at about 8.5s, but the bus voltage has a static difference, and the larger the input power is, the larger the static difference is; after the voltage compensation is added, the direct current voltage is recovered to a constant value at about 7.5s, and the voltage overshoot and the adjustment time are reduced. As can be seen from fig. 6 (b), at t=7s, the input power of the DC/AC converter also increases suddenly due to the sudden increase of the input power of the system, and the input power tends to stabilize over about 0.2s in the case of voltage compensation, whereas the input power tends to stabilize over about 0.8s in the case of no voltage compensation. Therefore, the voltage compensation link not only can eliminate the static difference of voltage regulation, but also can improve the dynamic characteristic of the system after disturbance.
3. Taking the function of parameter self-adaptive control of the capacity of the converter into consideration;
in this embodiment, other parameters are set to be unchanged, t=7s, the illumination intensity is suddenly increased by 600lx, and the dynamic response of the system under the adaptive control taking the converter capacity into consideration is shown in fig. 7, where fig. 7 (a) is a schematic diagram of the change of the input power of the DC/AC converter, and fig. 7 (b) is a schematic diagram of the change of the voltage of the DC bus. As can be seen from the dashed line in fig. 7 (a), when the virtual inertia of the DC/AC converter is adjusted without considering the capacity constraint of the converter, the input power of the converter is suddenly increased by about 7.1s under a larger disturbance (wherein the dashed line is free of capacity constraint, the solid line is free of capacity constraint, the power of the converter is not limited before the moment, the power change rule is the same, and therefore, the front curves overlap), the instantaneous power exceeds the rated capacity by 15MW, the converter immediately changes to the limited power operation, and the power waveform suddenly changes at the moment; as is clear from the solid line in fig. 7 (a), when t=7s is considered after the capacity limit, the active power fluctuates, but the power is restored to be stable after the adjustment of about 0.3 s. As can be seen from the broken line of fig. 7 (b), when the capacity-free adaptive control is adopted, the DC/AC converter loses the voltage regulation capability at t=7.1 s, and the battery DC/DC converter is switched to constant voltage operation to maintain the stable bus voltage, but the regulation time is long, and the voltage is restored to the initial value at about 9.5 s; as shown by the solid line in fig. 7 (b), considering the constraint of the converter, the converter provides inertia to the system, and at the same time, the converter does not exceed the power limit value as much as possible, so that the converter still has voltage regulating capability under larger disturbance, and the bus voltage is stable at about 8 s.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
In order to achieve the above embodiments, an embodiment of a second aspect of the present invention provides a wind-solar-storage dc micro-grid voltage adaptive control device, including:
the system comprises a virtual synchronous machine-like control equation construction module, a virtual synchronous machine-like control equation generation module and a virtual synchronous machine control module, wherein the virtual synchronous machine-like control equation construction module is used for respectively constructing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, the control equations comprise voltage compensation links, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
the control parameter adjusting range determining module is used for performing root locus diagram drawing by converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation so as to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
and the self-adaptive adjusting module is used for self-adaptively adjusting the equivalent virtual capacitor and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter according to the voltage dynamic response condition and the capacity limit of the DC/AC converter based on the adjusting range so as to realize the self-adaptive control of the wind-solar storage direct current micro-grid voltage.
It should be noted that the foregoing explanation of the embodiment of the wind-solar-storage direct-current micro-grid voltage adaptive control method is also applicable to the wind-solar-storage direct-current micro-grid voltage adaptive control device of the present embodiment, and is not repeated herein. According to the wind-solar-storage direct-current micro-grid voltage self-adaptive control device provided by the embodiment of the invention, corresponding virtual synchronous machine-like control equations are respectively established for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar-storage direct-current micro-grid, wherein the control equations comprise a voltage compensation link, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters; converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation, and performing root locus diagram drawing to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine; based on the adjusting range, the equivalent virtual capacitance and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter are adaptively adjusted according to the voltage dynamic response condition and the capacity limit of the DC/AC converter, so as to realize the adaptive control of the wind-solar storage direct current micro-grid voltage. Therefore, in the voltage control of the wind-solar direct-current micro-grid, the voltage quality is effectively improved, the stability of a new energy grid-connected system is improved, and meanwhile, the power limit of the grid-connected converter is not exceeded as much as possible in the running process of the grid-connected converter, so that the service life of the grid-connected converter is prolonged.
To achieve the above embodiments, an embodiment of a third aspect of the present invention provides an electronic device, including:
at least one processor; and a memory communicatively coupled to the at least one processor;
the memory stores instructions executable by the at least one processor, and the instructions are configured to perform the wind-solar direct current micro-grid voltage adaptive control method.
To achieve the above embodiments, a fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to execute the above method for adaptively controlling a voltage of a wind-solar direct current micro-grid.
It should be noted that the computer readable medium described in the present disclosure may be a computer readable signal medium or a computer readable storage medium, or any combination of the two. The computer readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples of the computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this disclosure, a computer-readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. In the present disclosure, however, the computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, with the computer-readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: electrical wires, fiber optic cables, RF (radio frequency), and the like, or any suitable combination of the foregoing.
The computer readable medium may be contained in the electronic device; or may exist alone without being incorporated into the electronic device. The computer readable medium carries one or more programs which, when executed by the electronic device, cause the electronic device to perform a method for adaptively controlling voltage of a wind-solar direct current micro-grid according to the above embodiment.
Computer program code for carrying out operations of the present disclosure may be written in one or more programming languages, including an object oriented programming language such as Java, smalltalk, C ++ and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider).
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and further implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the embodiments of the present application.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium may even be paper or other suitable medium upon which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
Those of ordinary skill in the art will appreciate that all or a portion of the steps carried out in the method of the above-described embodiments may be implemented by a program to instruct related hardware, where the program may be stored in a computer readable storage medium, and where the program, when executed, includes one or a combination of the steps of the method embodiments.
In addition, each functional unit in each embodiment of the present application may be integrated in one processing module, or each unit may exist alone physically, or two or more units may be integrated in one module. The integrated modules may be implemented in hardware or in software functional modules. The integrated modules may also be stored in a computer readable storage medium if implemented as software functional modules and sold or used as a stand-alone product.
The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, or the like. Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (10)
1. The wind-solar-storage direct-current micro-grid voltage self-adaptive control method is characterized by comprising the following steps of:
respectively establishing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, wherein the control equations comprise a voltage compensation link, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation, and performing root locus diagram drawing to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
based on the adjusting range, the equivalent virtual capacitance and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter are adaptively adjusted according to the voltage dynamic response condition and the capacity limit of the DC/AC converter, so as to realize the adaptive control of the wind-solar storage direct current micro-grid voltage.
2. The method of claim 1, wherein the virtual synchronous machine-like control equation expression for the DC/AC converter is as follows:
wherein i is dc Injecting current into the direct current micro-grid for the DC/AC converter; i.e out The output direct current of the DC/AC converter; d (D) v Virtual damping coefficients for the DC/AC converter; c (C) v Is a DC/AC converterIs a virtual equivalent capacitance of (a); u (u) dcref A DC/AC converter DC bus voltage reference value; u (U) n Rated voltage of the direct current bus;
wherein i is out ＝K p (U n -u dc )，K p For droop control factor, u dc The output voltage is the DC side.
3. The method of claim 2, wherein the virtual synchronous machine-like control equation expression for the DC/DC converter is as follows:
wherein i is b Inputting current to the DC/DC converter; i.e b_dc A current flowing into a DC bus for the DC/DC converter; c (C) vb2 An equivalent virtual capacitance of the DC/DC converter; d (D) vb2 Virtual damping coefficient of DC/DC converter; u (u) dcrefb2 A voltage reference is output for the DC/DC converter.
4. A method according to claim 3, characterized in that the virtual synchronous machine-like control small signal equation expression of the DC/AC converter is as follows:
wherein s is a differential operator; Δi dc (s) is a DC current increment; deltau dcref And(s) is a DC voltage increment.
5. The method of claim 4, wherein said determining the adjustment range of the virtual damping coefficient and the equivalent virtual capacitance of the DC/AC converter controlled by the virtual synchronous machine comprises:
according to the virtual synchronous machine-like control small signal equation, respectively obtaining DC bus voltage disturbanceQuantity Deltau dc D-axis current disturbance Δi d D-axis voltage disturbance delta u d DC disturbance quantity delta i dc The relation between the two is:
in U dc 、I dc Rated operating voltage and rated operating current respectively; c is a direct-current side voltage stabilizing capacitor; u (U) d Is the steady-state value of the d-axis voltage component at the network side, I d The steady-state value of the d-axis current component at the network side is obtained;
let Δi dref The controller of the current loop adopts a PI regulator, G i (s)＝k pi +k ii The small signal equation for the d-axis current component obtained by/s is:
wherein k is pi Is the proportionality coefficient, k of the current loop controller ii Is the integral coefficient of the current loop controller, L 1 And r are respectively a grid side filter inductor and a series resistor thereof;
the voltage compensation link adopts PI regulator and G 0 (s) represents G 0 (s)＝k p0 +k i0 And/s, the control equation of the compensation voltage is as follows:
(U n -u dc )G 0 (s)＝u dcref (6) Wherein k is p0 For scaling factor, k, of regulator in voltage compensation link i0 The integral coefficient of the regulator in the voltage compensation link;
By Deltau dc And Deltau dcref The method comprises the steps of respectively representing the disturbance quantity of the DC bus voltage and the disturbance quantity of a DC voltage reference value, and obtaining after Laplacian transformation of a control equation of the compensation voltage:
obtaining the DC side output voltage disturbance delta u according to formulas (3), (4), (5) and (7) dc (s) disturbance amount Deltai with output current dc The closed loop transfer function between(s) is:
wherein a=k p +D v 、m＝k pi k iv +k ii k pv ，
Wherein k is pwm Equivalent amplification gain for bridge voltage; k (k) pv 、k iv For the voltage outer loop PI regulator parameter, a i And b j Are all intermediate parameters i=1, …,5,j =1, …,6;
by performing stability analysis on the formula (8), G(s) is plotted on the virtual capacitance C v Pole profile under variation and G(s) at virtual damping D v Pole distribution diagram under variation, then respectively drawing C v 、D v Root trace of G(s) at change to determine C v 、D v Is a range of values.
6. The method of claim 5, wherein the voltage dynamic response condition comprises 4 phases:
stage 1: when the voltage change rate du of the direct current bus dc /dt>0, and voltage deviation Deltau>At 0, the virtual capacitance C of the DC/AC converter is increased by correlating the magnitude of the voltage change rate v And virtual of DC/DC converterCapacitor C vb2 To reduce the voltage change rate and the virtual damping coefficient D of the DC/AC converter according to the magnitude of the voltage deviation v The response speed of the system is improved, and the voltage overshoot is reduced;
stage 2: when the voltage change rate du of the direct current bus dc /dt<0 and voltage deviation Deltau>At 0, C is reduced according to the magnitude of the voltage change rate v And C vb2 So that the voltage is restored to a stable value, D is increased according to the magnitude of the voltage deviation v To accelerate the decay rate of the voltage;
stage 3: when the voltage change rate du of the direct current bus dc /dt<0 and voltage deviation Deltau<At 0, C is increased according to the voltage change rate v And C vb2 To reduce the voltage change rate and D according to the magnitude of the voltage deviation v To accelerate the voltage regulation speed;
stage 4: when the DC voltage change rate du dc /dt>0 and voltage deviation Deltau<At 0, C is reduced according to the magnitude of the voltage change rate v And C vb2 Increase D according to magnitude of voltage deviation v To smooth out voltage fluctuations.
7. The method of claim 6, wherein the adaptively adjusting the equivalent virtual capacitance and the virtual damping coefficient of the DC/AC converter and the DC/DC converter, respectively, comprises:
virtual capacitor C of DC/AC converter v And virtual capacitor C of DC/DC converter vb2 The relation of the adaptive control is as follows:
wherein C is 01 C is the virtual capacitance initial value of the DC/AC converter 02 The virtual capacitance initial value of the DC/DC converter;
C vx To consider the virtual capacitance compensation value of the voltage response, C vy To take into account the compensation value of the virtual capacitance of the DC/AC converter capacity limitation, expression is madeThe formula is as follows:
wherein k is c1 、k c2 、k c3 As a virtual capacitance adjustment parameter, deltau is the deviation amount of the direct current voltage and the rated value; dudt is the rate of change of the DC voltage; k (k) 1 Is a voltage change rate threshold; p is the output power of the DC/AC converter; p (P) N An upper power limit for the DC/AC converter;
virtual damping coefficient D of DC/DC converter vb2 ＝D 0 Virtual damping coefficient D of DC/AC converter v The adaptive adjustment is performed according to the dc voltage deviation amount as follows:
wherein D is 0 Is the initial value, k, of the virtual damping coefficient of the DC/AC converter d1 、k d2 For damping adjustment parameters, k 2 Is the voltage deviation amount threshold.
8. The utility model provides a scene stores up direct current microgrid voltage self-adaptation controlling means which characterized in that includes:
the system comprises a virtual synchronous machine-like control equation construction module, a virtual synchronous machine-like control equation generation module and a virtual synchronous machine control module, wherein the virtual synchronous machine-like control equation construction module is used for respectively constructing corresponding virtual synchronous machine-like control equations for a DC/AC converter and a DC/DC converter which adopt voltage-current droop control in a wind-solar storage direct-current micro-grid, the control equations comprise voltage compensation links, and the control equations consider equivalent virtual capacitance and virtual damping coefficients of the corresponding converters;
The control parameter adjusting range determining module is used for performing root locus diagram drawing by converting a quasi-virtual synchronous machine control equation of the DC/AC converter into a quasi-virtual synchronous machine control small signal equation so as to determine the adjusting range of the equivalent virtual capacitor and the virtual damping coefficient of the DC/AC converter controlled by the quasi-virtual synchronous machine;
and the self-adaptive adjusting module is used for self-adaptively adjusting the equivalent virtual capacitor and the virtual damping coefficient respectively corresponding to the DC/AC converter and the DC/DC converter according to the voltage dynamic response condition and the capacity limit of the DC/AC converter based on the adjusting range so as to realize the self-adaptive control of the wind-solar storage direct current micro-grid voltage.
9. An electronic device, comprising:
at least one processor; and a memory communicatively coupled to the at least one processor;
wherein the memory stores instructions executable by the at least one processor, the instructions being arranged to perform the method of any of the preceding claims 1-7.
10. A computer readable storage medium storing computer instructions for causing the computer to perform the method of any one of claims 1-7.
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| CN116316707A (en) * | 2023-05-12 | 2023-06-23 | 广东电网有限责任公司广州供电局 | Virtual synchronous machine dynamic performance improvement method based on equivalent resistance-capacitance damping circuit |
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| CN116316707A (en) * | 2023-05-12 | 2023-06-23 | 广东电网有限责任公司广州供电局 | Virtual synchronous machine dynamic performance improvement method based on equivalent resistance-capacitance damping circuit |
| CN116316707B (en) * | 2023-05-12 | 2023-08-22 | 广东电网有限责任公司广州供电局 | Virtual synchronous machine dynamic performance improvement method based on equivalent resistance-capacitance damping circuit |
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