CN117578453A - Stability analysis and active control method for independent power grid of hybrid converter cluster - Google Patents
Stability analysis and active control method for independent power grid of hybrid converter cluster 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
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J3/381—Dispersed generators
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a stability analysis and active control method for a hybrid converter cluster independent power grid. The method comprises the following steps: the small signal voltage current relation modeling method of the grid-built converter and the small signal voltage current relation modeling method of the grid-built converter which considers the influence of the output power of the converter; based on model parameter characteristics, realizing cluster aggregation, and determining a network-structured converter cluster and network-following converter cluster impedance model aggregation method considering positive and negative sequence coupling; under the operation scene of an independent power grid, establishing an independent power grid decoupling positive sequence and negative sequence impedance modeling method and a stability analysis method which consider interaction between a grid-structured converter and a grid-following converter cluster; and (3) carrying out an active stable control strategy of coordinating, optimizing and regulating and controlling the power of the independent power grid of the grid-structured converter cluster and the grid-following converter hybrid cluster based on the designed centralized controller.
Description
Technical Field
The invention relates to the field of stability analysis and control of small interference of independent power grids, in particular to a stability analysis and active control method of a hybrid converter cluster independent power grid.
Background
With the rapid development of renewable energy sources such as wind power and photovoltaic, an ac independent power grid system mainly composed of a distributed power source has attracted attention in recent years. Such systems provide inertial and damped support due to the lack of synchronous generators, and the problem of small disturbance instability is significant.
On the one hand, in the aspect of stability analysis, the prior art mainly controls the converters of the same type, and because the grid-following converters cannot form a grid independently, the prior art concentrates on a grid-following converter independent power grid system, and the technology for analyzing the stability of the mixed independent power grid with the grid-following converters and the grid-following converters simultaneously has a technical blank.
On the other hand, in the aspect of active stability control strategies, a large number of bottom layer optimization strategies based on converters are discussed and proposed. The method comprises a power oscillation damping link and a virtual impedance strategy related to the grid-built converter, phase-locked loop damping characteristic remodeling related to the grid-built converter, virtual admittance based on grid-connected point voltage and the like. The strategy has guiding significance on the equipment level, but the equipment bottom layer optimization needs detailed data and a large amount of engineering experiments, and is difficult to be directly applied to a current running system.
Therefore, the stability analysis and active stability control strategies of the hybrid cluster independent power grid of the grid-following converter and the grid-structuring converter from the system operation level all have a technical blank to be perfected.
Disclosure of Invention
Therefore, the invention aims to overcome the defect that the stability analysis and active stability control strategy of the mixed cluster independent power grid of the grid-connected converter and the grid-structured converter in the prior art is blank, thereby providing an active stability control strategy starting from the system operation level.
In order to achieve the above purpose, the present invention provides the following technical solutions:
in a first aspect, an embodiment of the invention provides a method for analyzing stability of a hybrid converter cluster independent power grid. The method comprises the following steps:
based on the respective circuit topology and control system structure of the grid-connected converter and the grid-connected converter, a small signal modeling method is adopted to establish a grid-connected converter voltage-current relation model and a grid-connected converter voltage-current relation model which comprise converter control parameters, circuit parameters and converter output power;
respectively carrying out aggregation calculation on converter control parameters, circuit parameters and converter output power in the grid-structured converter voltage-current relation model and the grid-following converter voltage-current relation model in a cluster multi-converter parallel scene, establishing a grid-structured converter cluster aggregation voltage-current relation model and a grid-following converter cluster aggregation voltage-current relation model, and solving a grid-structured converter cluster aggregation impedance model and a grid-following converter cluster aggregation impedance model;
based on the grid-built converter cluster aggregation impedance model and the grid-following converter cluster aggregation impedance model, determining an equivalent circuit model of a hybrid converter cluster independent power grid according to a circuit topology structure, respectively aiming at a system positive sequence disturbance and a system negative sequence disturbance injection scene, establishing positive sequence and negative sequence equivalent circuit models of the hybrid converter cluster independent power grid, and analyzing the influence of output power of the grid-built converter cluster and the grid-following converter cluster on the system stability by adopting a Nyquist stability criterion;
in one embodiment, a modeling method for determining a small-signal voltage-current relation model of a grid-built converter and a small-signal voltage-current relation of a following grid converter is characterized by considering the influence of output power of the converter. Comprising the following steps: based on the circuit topology and the control system structure of the grid-connected converter, the relation among the disturbance voltage, the disturbance current, the disturbance power and the disturbance phase angle of the grid-connected converter under the disturbance frequency is considered, and a relation matrix model between the disturbance voltage and the disturbance current of the grid-connected converter is established under a synchronous rotation coordinate system (dq coordinate system). Based on the circuit topology and the control system structure of the grid-following converter, the relation among the disturbance voltage, the disturbance current, the disturbance power and the disturbance phase angle of the grid-following converter under the disturbance frequency is considered, and a relation matrix model between the disturbance voltage and the disturbance current of the grid-following converter is established under a synchronous rotation coordinate system (dq coordinate system).
In one embodiment, a method for aggregating impedance models of a grid-built converter cluster and a grid-following converter cluster is established, wherein the model power parameter characteristics and positive and negative sequence coupling are considered. Comprising the following steps: according to a small signal voltage current relation model of the grid-structured converter considering the influence of the output power of the converter, determining that the direct aggregation condition of the grid-structured converter clusters is that the output power of the grid-structured converters in the clusters is consistent, aggregating based on the total power, and obtaining an aggregated grid-structured converter cluster sequence impedance model by adopting equivalent transformation from a synchronous rotation coordinate system to a sequence coordinate system. According to a small signal voltage-current relation model of the grid-following converter considering the influence of the output power of the converter, determining that the grid-following converter clusters can be aggregated based on total power under the condition that the output power of each grid-following converter in the clusters is inconsistent, and obtaining an aggregated grid-following converter cluster sequence impedance model by adopting equivalent transformation from a synchronous rotation coordinate system to a sequence coordinate system.
In an embodiment, a method for modeling decoupling positive sequence and negative sequence impedance in an independent power grid and a method for analyzing system stability are provided, which are characterized in that interaction between a grid-built converter and a grid-following converter cluster and an independent power grid operation scene are considered. Comprising the following steps: under the operation scene of an independent power grid, establishing a positive-negative sequence coupling equivalent circuit of a grid-structured converter cluster based on an independent grid-structured converter cluster aggregate impedance model; based on an independent grid-connected converter cluster aggregate impedance model, a grid-connected converter cluster positive and negative sequence coupling equivalent circuit is established, and then an independent power grid equivalent circuit is determined. And respectively considering positive sequence disturbance and negative sequence disturbance for the equivalent circuit of the independent power grid, performing positive and negative sequence decoupling according to voltage-current interaction among clusters, determining a positive sequence impedance model and a negative sequence impedance model of decoupling of the grid-constructed converter clusters and the grid-following converter clusters in the independent power grid scene, and adopting a generalized Nyquist criterion to judge the stability analysis method of the influence of the system on different system capacity planning and actual operation working points.
In a second aspect, an embodiment of the present invention provides an active stability control method for a hybrid converter cluster independent power grid. The method comprises the following steps: based on the analysis result of the influence of the output power of the converter cluster on the system stability, establishing a following network type converter cluster active power and reactive power instruction database for maintaining the system operation; and after receiving the system small-interference instability instruction, the central controller adjusts the active power and reactive power reference values of the follow-up network type converter based on the database self-adaptive issuing instruction to perform active stability control.
In a third aspect, an embodiment of the invention provides a stability analysis and active control system for an independent power grid of a hybrid converter cluster. The system comprises: the small signal model calculation module is used for establishing a grid-formed current transformer voltage-current relation model and a grid-following current transformer voltage-current relation model; the cluster impedance aggregation calculation module is used for solving a cluster impedance aggregation model of the current transformer; the independent power grid stability analysis module is used for analyzing the stability of the independent power grid system of the hybrid converter cluster and establishing a system stable operation maintenance instruction database; and the active stability control module is used for performing active control when the system is unstable due to small interference, so that the system is recovered and stabilized.
The technical scheme of the invention has the following advantages:
1) The invention provides a method for analyzing stability of a mixed cluster independent power grid of a follow-up grid type converter and a grid-structured converter. The method for aggregating the impedance models of the grid-structured converter cluster and the follow-up grid converter cluster, which is realized based on the model parameter characteristics and takes the positive and negative sequence coupling into consideration, provides a detailed analysis theoretical model of stability.
2) The invention provides a method for analyzing stability of a mixed cluster independent power grid of a follow-up grid type converter and a grid-structured converter. The method for modeling the decoupling positive sequence and the negative sequence impedance of the independent power grid by considering interaction between the grid-connected converter and the grid-connected converter cluster and the method for analyzing the stability by considering the influence of system capacity planning and actual operation working points are established, and the blank of the current research on the method for analyzing the stability of the power operation level of the independent power grid of the grid-connected converter and the grid-connected converter hybrid cluster is filled.
3) The invention provides an active stabilization control method for a hybrid cluster independent power grid of a grid-connected converter and a grid-structured converter, which is used for carrying out coordination, optimization and regulation and control on independent power grid power based on a designed centralized controller and fills the blank of the active stabilization control strategy for the stability of the power operation level of the hybrid cluster independent power grid of the grid-connected converter and the grid-structured converter in the current research.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a specific example of a method for analyzing and improving stability of a hybrid cluster independent power grid of a grid-connected converter and a grid-structured converter according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a mixed cluster independent power grid of a grid-following converter and a grid-constructing converter according to an embodiment of the present invention;
fig. 3 is a control block diagram of a heel-net type converter and a grid-constructed converter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a cluster aggregation method of a grid-connected converter and a grid-structured converter according to an embodiment of the present invention;
fig. 5 is an equivalent circuit diagram of an independent power grid after positive and negative sequence coupling and decoupling according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an active stability control method of a hybrid cluster independent power grid of a grid-connected converter and a grid-structured converter according to an embodiment of the present invention;
fig. 7 is a reactive power regulation strategy effect diagram in the active stabilization control method according to the embodiment of the present invention;
FIG. 8 is a graph showing the effect of an active power adjustment strategy in an active stability control method according to an embodiment of the present invention;
FIG. 9 is a flowchart of a specific example of a control system provided by an embodiment of the present invention;
fig. 10 is a composition diagram of a specific example of a computer device according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. 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.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Example 1
The embodiment of the invention provides a stability analysis method for a hybrid converter cluster independent power grid, which is shown in fig. 1, and comprises the following steps of S11 to S13, wherein the method comprises the following steps of:
step S11: in the mixed cluster independent power grid scene of the grid-following converter and the grid-constituting converter shown in fig. 2, a small signal voltage current relation model of the grid-constituting converter and a small signal voltage current relation model of the grid-constituting converter are established based on the grid-constituting converter and a control system thereof and the grid-constituting converter and a control system structure thereof shown in fig. 3.
Specifically, the grid-connected converter and the follow-up grid converter of the embodiment of the invention both adopt standard control strategies, and the problem of small interference stability is influenced by each link in the control system. In addition, the influence of the system running power is particularly prominent in the scene of a mixed cluster independent power grid of a grid-connected converter and a grid-structured converter. And establishing a converter equivalent small-signal voltage-current relation model which mainly considers the influence of the operating power. The step S11 includes steps S21 to S22, and specifically includes the following steps:
step S21: for a single grid-structured converter, a small signal voltage current relation model of the grid-structured converter is established based on the circuit topology structure and the control system structure of the grid-structured converter in fig. 3 (a).
In the subsequent step, the system running state variables such as voltage, current, power and the like are obtained through secondary equipment monitoring, sampling and signal processing links; the converter parameters are provided by the converter.
The transfer function model of each part of the network converter is complete in the existing research, the transfer function model of each part is not deduced in detail, and a conclusion is directly given:
transfer function of voltage loop of grid-built converter: f (F) E_M ＝k pe_M +k ie_M S, wherein: s is the Laplace differential operator (consistent hereinafter), k pe_M And k ie_M The current loop ratio coefficient and the integral coefficient are respectively; current loopTransfer function: f (F) I_M ＝k pi_M +k ii_M S, wherein: s is a Laplace differential operator, k pi_M And k ii_M The current loop ratio coefficient and the integral coefficient are respectively; transfer function of power synchronization link: f (F) θ_M ＝-1.5(s(Js+D)) -1 Wherein: j is an inertia coefficient and D is a damping coefficient; reactive sagging link: f (F) q_M ＝-k q Wherein: k (k) q Is a reactive sag coefficient; filter circuit F f_M ＝R f_M +sL f_M Wherein: r is R f_M And L f_M The filter resistor and the filter inductor are respectively arranged.
In addition, to make the polymerization method in the subsequent step S12 more intuitive, aΔe is used for a single converter dq +BΔI dq The form of =0 instead of impedance matrix Z describes its output small signal voltage-current relationship, q where: ΔE dq ＝[ΔE d ,ΔE q ] T ,ΔI dq ＝[ΔI d ,ΔI q ] T A, B is a transfer function matrix, and the current flows out in a positive direction; meanwhile, in order to intuitively analyze the influence of the static working point of the island system, the steady-state current I in the impedance model of the synchronous rotation coordinate system (dq coordinate system) is calculated d ，I q The active power P and the reactive power Q are used for replacement, and the phase synchronization of the network-structured converter is considered to be based on a voltage phasing d-axis, namely E q_M =0, there are:
wherein the subscript M denotes a grid converter, hereinafter referred to as such. Combining transfer functions of the parts, and finishing to obtain the product:
wherein:
B M_11 ＝-F I_M -F f_M +F I_M F θ_M Q M
B M_12 ＝-(F I_M F E_M +1)(1.5F q_M E M E M )
B M_21 ＝-(F I_M F E_M +1)(1.5F θ_M E M E M )-F I_M F θ_M P M
B M_22 ＝-F I_M -F f_M
the small signal voltage-current relation model of the typical network-structured converter shown in fig. 3 (a) is obtained.
Step S22: for a single grid-connected converter, a small signal voltage-current relation model of the grid-connected converter is built based on the circuit topology structure and the control system structure of the grid-connected converter in fig. 3 (b).
Specifically, the transfer function model of each part of the follow-up grid type converter is complete in the existing research, the transfer function model of each part is not deduced in detail, and a conclusion is directly given:
transfer function of direct current voltage ring of grid-connected converter: f (F) dc_L ＝k pdc_L +k idc_L S, wherein: k (k) pdc_L And k idc_L The proportional coefficient and the integral coefficient of the direct current voltage ring are respectively; reactive power loop transfer function: f (F) q_L ＝k pq_L +k iq_L S, wherein: k (k) pq_L And k iq_L Respectively isThe proportional coefficient and the integral coefficient of the reactive power loop; current loop transfer function: f (F) I_L ＝k pi_L +k ii_L S, wherein: k (k) pi_L And k ii_L The current loop ratio coefficient and the integral coefficient are respectively; phase-locked loop transfer function: h PLL (s)＝k pPLL +k iPLL S, wherein: k (k) pPLL And k iPLL The phase-locked loop ratio coefficient and the integral coefficient are respectively; voltage feedforward filtering link: f (F) V_L ＝1/(1+sT V_L ) Wherein: t (T) V_L Is a filtering time constant; filter circuit F f_M ＝R f_L +sL f_L Wherein: r is R f_L And L f_L The filter resistor and the filter inductor are respectively arranged.
Also adopt A delta E dq +BΔI dq The form of =0 instead of impedance matrix Z describes the voltage-current relationship of the output small signal and the same voltage phase d-axis as the net type converter, i.e. E q_L =0, there are:
wherein the subscript L denotes a grid-connected inverter, hereinafter referred to as such. Combining transfer functions of the parts, and finishing to obtain the product:
wherein:
B L_11 ＝-F I_L F dc_L (1.5E L )-F I_L -F f_L
B L_12 ＝0
B L_21 ＝0
B L_22 ＝-F I_L F q_L (1.5E L )-F I_L -F f_L
(F PLL ＝H PLL (s)(s+H PLL (s)E L ) -1 )
the small signal voltage-current relation model of the typical follow-net type converter shown in the figure 3 (b) is obtained.
Step S12: on the basis of the small signal voltage-current relation model of the grid-built current transformer and the small signal voltage-current relation model of the following grid-built current transformer established in the step S11, an aggregation condition is determined based on the respective small signal voltage-current relations of the grid-built current transformer and the following grid-built current transformer, and an aggregation method of the grid-built current transformer cluster and the following grid-built current transformer cluster impedance model is established, as shown in fig. 4.
In particular, the converters within a cluster are connected to a unified common grid-tie point, the voltage sampling of each converter is uniform for any cluster, and the single converter aΔe dq +BΔI dq The voltage-current relationship of=0 can be aggregated as:
with a single current transformer aΔe dq +BΔI dq The voltage-current relationship for =0 is similar, and the column writes the cluster voltage-current relationship expression:
A C ΔE dq_C +B C ΔI dq_C ＝0 (6)
wherein: subscript C denotes the cluster, small disturbance delta E of the cluster output voltage dq_C ＝ΔE dq Small disturbance quantity delta I of cluster output current dq_C ＝∑ΔI dq_i And (3) sorting the relation between the output voltage and the current of the clusters to obtain:
it is easily seen from (7): the conditions under which clusters can be directly aggregated are:
1)A i can be directly overlapped;
2)B i is uniform for all converters i.
A in formula (2) M Contains the power product term: p (P) M P M ，P M Q M Etc., B M The power term is contained in the following components: p (P) M ，Q M . Therefore, for GFM clusters, to meet the above conditions, it is necessary to ensure that the output power of each unit is consistent.
Such power cooperative control methods are available and widely employed in typical networked converter systems, such as energy storage systems.
And with the net type converter cluster, because of A L_i Can be directly overlapped and B L_i All the power generation units i are consistent, and the polymerization can be directly carried out under the condition of different output powers.
The actual running is clustered with the number of the grid-connected converters, and a photovoltaic system is taken as an example, the maximum power tracking control is adopted, the output power difference is caused by different unit illumination intensity differences, and the aggregation method provided by the invention is applicable to the output power scene of the grid-connected converters.
The polymerization process described above is shown in FIG. 4. Based on formulas (2), (6) and (7), an aggregate voltage-current relation model matrix A of the grid-connected converter cluster is obtained MC And B MC ：
Wherein n=n GFM Is in a clusterThe number of the grid-formed converters. Similarly, an aggregate voltage-current relationship model matrix A of the grid-connected current transformer cluster can be obtained LC And B LC 。
Step S13: based on the aggregation method of the grid-structured converter cluster and the grid-following converter cluster impedance model in the step S12, the voltage-current relationship in the dq coordinate system is converted into the coupling equivalent circuit relationship in the sequence impedance, and decoupling is performed respectively for independent positive sequence disturbance and independent negative sequence disturbance scenes, so that a decoupling positive sequence and negative sequence impedance modeling method and a system stability analysis method in an independent power grid are provided, as shown in fig. 5.
Specifically, based on the form A.DELTA.E dq +BΔI dq The relation between the output voltage and the current of the component=0 is arranged to obtain the dq coordinate system, equivalent impedance model Z of constructed network type converter cluster and follow network type converter cluster MC_dq And Z LC_dq ：
Considering line impedance, and converting the grid-connected converter cluster and the grid-connected converter cluster to a common grid-connected point voltage E load And obtaining a network converter cluster containing tie lines and a network following converter cluster impedance model under the dq coordinate system corresponding to the d axis:
wherein:r is the impedance of the cluster line of the network-structured converter l_MC And L l_MC Line resistance and inductance, respectively. Root network converter cluster line impedance Z l_LC_dq And the same is true.
The matrix model under the dq coordinate system is difficult to directly use for small-interference stability analysis, and the physical concept is not intuitive enough. Therefore, transformation to the sequence domain model is required to develop subsequent studies:
wherein:note that the sequence impedance model of the system has positive and negative sequence coupling portions, characterized in fig. 5 in the form of a controlled voltage source.
And decoupling the sequence domain coupled impedance model by independently analyzing the disturbance source. Taking positive sequence impedance as an example, discussion of positive sequence disturbance I alone inj,p During injection, negative sequence current is injected into I inj,n =0. Based on the Hoff voltage and current law of positive and negative sequence circuits, the equivalent positive sequence impedance Z of the grid-type converter cluster is obtained LC_p And equivalent positive sequence impedance Z of network-structured converter cluster MC_p The method comprises the steps of carrying out a first treatment on the surface of the Similarly, we get a solution that only considers positive order disturbance I inj,n When in injection, equivalent negative sequence impedance Z of the grid-connected converter cluster LC_n Equivalent negative sequence impedance Z of grid-connected transformer cluster MC_n And (5) finishing to be (10).
Based on the formula (12), a mixed independent power grid positive sequence equivalent circuit and a mixed independent power grid negative sequence equivalent circuit model which are shown in fig. 5 and are in interaction with the grid-type converter clusters and the grid-type converter clusters can be obtained.
Considering the different external characteristics of the current source and the voltage source, the nyquist stability analysis function of the system is shown as formula (13):
based on formulas (1) - (13), the system Nyquist criterion L p And L n There are 8 influencing factors as follows: installation design parameters: number of network-structured converters N GFM Number of heel-net type converters N GFL The method comprises the steps of carrying out a first treatment on the surface of the Operating power parameters: active power P output by network-structured converter cluster MC And reactive power Q MC Active power P output by following net type converter cluster LC And reactive power Q LC Load active power P load And reactive power Q load . The running power has correlation, and the uncontrolled dynamic change power P in the running process is selected in consideration of the actual running characteristic of the system LC ，Q LC ，P load And Q load As independent variable, let P MC ，Q MC As a power balance term. Stability discussion can be further developed.
The method provides basis for an active stability control strategy, and the stability analysis conclusion based on the method is as follows:
1) In a mixed independent power grid of a grid-connected converter cluster and a grid-structured converter cluster, the larger the grid-structured converter cluster capacity is, the higher the system stability is, and a certain storage capacity of the grid-structured converter cluster needs to be ensured in consideration of the small interference stability requirement.
2) At the running level of the hybrid independent power grid, the high active power output of the grid-following converter, the low reactive power output of the grid-following converter and the reduction of the active load or the increase of the reactive load all cause the reduction of the stability of small interference of the system.
The correlation results will be demonstrated in the results of example 2.
Example 2
The embodiment of the invention provides a method for actively stabilizing and controlling a hybrid converter cluster independent power grid, which is shown in fig. 6 and comprises the following steps:
the oscillation monitoring link is used for judging whether the system generates small-interference unstable oscillation or not, and a large number of maturation methods exist in the section, which is not the key point of the invention; the energy storage residual capacity monitoring link is used for monitoring the residual capacity of the energy storage batteries of the grid-structured converter cluster and providing reference for the coordination control of the central controller; coordination control link of the central controller: and generating a stable regulating signal according to each monitoring signal, and sending the stable regulating signal to converters in the following-net type converter cluster.
Specifically, the power generation characteristics of the actual running system and the grid-connected converter cluster determine that the output active power has an upper limit, the active power is easy to downwards adjust rather than upwards adjust, and the stability analysis result shows that the method for improving the stability of the system is feasible and easy to apply by adjusting the power of the grid-connected converter cluster in a mode of reducing the active power or improving the reactive power.
On the other hand, considering the overall operation condition of the system, under the condition that the residual capacity of the grid-connected converter cluster is lower, in order to keep the active power output generated by the grid-connected converter cluster as much as possible, the stability of the system is improved by increasing the reactive power output generated by the grid-connected converter cluster, and under the condition that the residual capacity of the grid-connected converter cluster is higher, a strategy for reducing the active power output generated by the grid-connected converter cluster is adopted.
When the oscillation monitoring link monitors the oscillation, the central controller enables a corresponding power regulation strategy based on the energy storage residual capacity monitoring, and based on the power flow monitoring result, the step S13 of the embodiment 1 is called to calculate and obtain active and reactive power regulation instructions, and the active and reactive power regulation instructions are issued to each following net type converter controller through the instruction issuing link.
The central controller adopts an active power adjustment strategy when the energy storage residual capacity of the grid-connected converter is more than 60 percent, and the corresponding simulation result shows that the energy storage residual capacity of the grid-connected converter is as shown in fig. 7: and when the energy storage residual capacity of the grid-structured converter is less than or equal to 60%, the central controller adopts a reactive power regulation strategy, and the corresponding simulation result is illustrated as shown in figure 8.
Example 3
The embodiment of the invention provides a system for decoupling control and reactive power rapid adjustment of a self-synchronous power supply of a weak power grid, which is shown in fig. 9 and comprises the following steps:
the small signal model calculation module 1 is used for extracting system running state sampling information from the power grid monitoring secondary equipment; calculating a grid-structured converter voltage-current relation and a grid-following converter voltage-current relation model based on the sampled voltage-current data, the converter control parameters and the circuit parameters; this module performs the method described in step S11 in embodiment 1, and will not be described here.
The cluster impedance aggregation calculation module 2 is used for calculating a cluster aggregation impedance model of the grid-structured converter based on the voltage-current relation model of the grid-structured converter determined by the small signal model calculation module and by combining the cluster running state sampling information; based on the voltage-current relation model of the grid-connected converter determined by the small signal model calculation module, calculating a cluster aggregation impedance model of the grid-connected converter by combining cluster operation state sampling information; this module performs the method described in step S12 in embodiment 1, and will not be described here.
The independent power grid stability analysis module 3 is used for analyzing the influence of the change of the active power and the reactive power output by the cluster of the grid-following converter on the system stability by combining the cluster impedance of the grid-constructed converter and the cluster impedance of the grid-following converter obtained by the cluster impedance aggregation calculation module with the nyquist stability criterion in combination with the sampling information of the running state of the independent power grid, and establishing a database of active power and reactive power regulation instructions of the grid-following converter cluster required for maintaining the stable running of the system based on the analysis result; this module performs the method described in step S13 in embodiment 1, and will not be described here.
The active stability control module 4 is used for receiving the system small-interference instability signal, and generating a power control instruction of the grid-following converter cluster according to the active power and reactive power instruction database of the grid-following converter cluster of the independent power grid stability analysis module and the energy storage residual electric quantity of the grid-following converter; the power control instruction is issued to the following network type converter cluster by adopting low-bandwidth communication; this module performs the method described in embodiment 2, and is not described here.
Example 4
An embodiment of the present invention provides a computer device, as shown in fig. 10, including: at least one processor 401, such as a CPU (Central Processing Unit ), at least one communication interface 403, a memory 404, at least one communication bus 402. Wherein communication bus 402 is used to enable connected communications between these components. The communication interface 403 may include a Display screen (Display) and a Keyboard (Keyboard), and the optional communication interface 403 may further include a standard wired interface and a wireless interface. The memory 404 may be a high-speed RAM memory (Ramdom Access Memory, volatile random access memory) or a non-volatile memory (non-volatile memory), such as at least one disk memory. The memory 404 may also optionally be at least one storage device located remotely from the aforementioned processor 401. The processor 401 may execute the method for analyzing the stability of the independent power grid of the current transformer cluster in embodiment 1 and the method for actively controlling the stability of the independent power grid of the hybrid current transformer cluster in embodiment 2. A set of program codes is stored in the memory 404, and the processor 401 calls the program codes stored in the memory 404 for executing the converter cluster independent grid stability analysis method in embodiment 1 and the hybrid converter cluster independent grid active stability control method in embodiment 2.
The communication bus 402 may be a peripheral component interconnect standard (peripheral component interconnect, PCI) bus or an extended industry standard architecture (extended industry standard architecture, EISA) bus, among others. Communication bus 402 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one line is shown in fig. 8, but not only one bus or one type of bus.
Wherein the memory 404 may include volatile memory (English) such as random-access memory (RAM); the memory may also include a nonvolatile memory (english: non-volatile memory), such as a flash memory (english: flash memory), a hard disk (english: hard disk drive, abbreviated as HDD) or a solid-state drive (english: SSD); memory 404 may also include a combination of the above types of memory.
The processor 401 may be a central processor (English: central processing unit, abbreviated: CPU), a network processor (English: network processor, abbreviated: NP) or a combination of CPU and NP.
Wherein the processor 401 may further comprise a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a Programmable Logic Device (PLD), or a combination thereof (English: programmable logic device). The PLD may be a complex programmable logic device (English: complex programmable logic device, abbreviated: CPLD), a field programmable gate array (English: field-programmable gate array, abbreviated: FPGA), a general-purpose array logic (English: generic array logic, abbreviated: GAL), or any combination thereof.
Optionally, the memory 404 is also used for storing program instructions. The processor 401 may invoke program instructions to implement the method for analyzing the stability of the independent power grid of the converter cluster in embodiment 1 and the method for actively controlling the stability of the independent power grid of the hybrid converter cluster in embodiment 2 as executed in the present application.
The embodiment of the invention also provides a computer readable storage medium, and computer executable instructions are stored on the computer readable storage medium, and the computer executable instructions can execute the method for analyzing the stability of the hybrid converter cluster independent power grid in the embodiment 1 and the method for actively controlling the stability of the hybrid converter cluster independent power grid in the embodiment 2. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a Flash Memory (Flash Memory), a Hard Disk (HDD), or a Solid-State Drive (SSD); the storage medium may also comprise a combination of memories of the kind described above.
The invention is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical aspects of the present invention, and is intended to be illustrative only and not limiting.
Claims (12)
1. The stability analysis and active control method for the independent power grid of the hybrid converter cluster is characterized by comprising the following steps of:
based on the respective circuit topology and control system structure of the grid-connected converter and the grid-connected converter, a small signal modeling method is adopted to establish a grid-connected converter voltage-current relation model and a grid-connected converter voltage-current relation model which comprise converter control parameters, circuit parameters and converter output power;
respectively carrying out aggregation calculation on converter control parameters, circuit parameters and converter output power in the grid-structured converter voltage-current relation model and the grid-following converter voltage-current relation model in a cluster multi-converter parallel scene, establishing a grid-structured converter cluster aggregation voltage-current relation model and a grid-following converter cluster aggregation voltage-current relation model, and solving a grid-structured converter cluster aggregation impedance model and a grid-following converter cluster aggregation impedance model;
based on the grid-built converter cluster aggregation impedance model and the grid-following converter cluster aggregation impedance model, determining an equivalent circuit model of a hybrid converter cluster independent power grid according to a circuit topology structure, respectively aiming at a system positive sequence disturbance and a system negative sequence disturbance injection scene, establishing positive sequence and negative sequence equivalent circuit models of the hybrid converter cluster independent power grid, and analyzing the influence of output power of the grid-built converter cluster and the grid-following converter cluster on the system stability by adopting a Nyquist stability criterion;
based on the analysis result of the influence of the output power of the converter cluster on the system stability, establishing a following network type converter cluster active power and reactive power instruction database for maintaining the system operation; and after receiving the system small-interference instability instruction, the central controller adjusts the active power and reactive power reference values of the follow-up network type converter based on the database self-adaptive issuing instruction to perform active stability control.
2. The method for analyzing and actively controlling the stability of the independent power grid of the hybrid converter cluster according to claim 1, wherein the voltage-current relation model of the grid-structured converter and the voltage-current relation model of the grid-structured converter are specifically determined as follows:
based on the circuit topology and the control system structure of the grid-connected converter, calculating the relation among the disturbance voltage, the disturbance current, the disturbance power and the disturbance phase angle of the grid-connected converter under the disturbance frequency, and establishing a voltage-current relation model of the grid-connected converter under a synchronous rotation coordinate system (dq coordinate system);
based on the circuit topology and the control system structure of the grid-connected converter, calculating the relation among the disturbance voltage, the disturbance current, the disturbance power and the disturbance phase angle of the grid-connected converter under the disturbance frequency, and establishing a voltage-current relation model of the grid-connected converter under a synchronous rotation coordinate system (dq coordinate system).
3. The method for analyzing and actively controlling the stability of the independent power grid of the hybrid converter cluster according to claim 1, wherein the aggregate impedance model and the follow-up converter cluster aggregate impedance model are specifically established as follows:
based on a voltage-current relation model of the grid-built current transformer, analyzing the aggregation characteristics of a current transformer control parameter, a circuit parameter and a current transformer output power in the model in a multi-current transformer parallel scene in a cluster, determining the direct aggregation condition of the grid-built current transformer cluster and the equivalent parameter after cluster aggregation, establishing a grid-built current transformer cluster aggregation voltage-current relation model under a synchronous rotation coordinate system (dq coordinate system), and obtaining an aggregated grid-built current transformer cluster sequence impedance model by adopting equivalent transformation from the synchronous rotation coordinate system to a sequence coordinate system;
based on a voltage-current relation model of the grid-following converter, analyzing the aggregation characteristics of converter control parameters, circuit parameters and converter output power in a cluster multi-converter parallel scene in the model, establishing a grid-following converter cluster aggregation voltage-current relation model under a synchronous rotation coordinate system (dq coordinate system), and obtaining an aggregated grid-following converter cluster sequence impedance model by adopting equivalent transformation from the synchronous rotation coordinate system to a sequence coordinate system.
4. The method for analyzing and actively controlling the stability of the independent power grid of the hybrid current transformer cluster according to claim 1, wherein the positive sequence and negative sequence equivalent circuit models of the independent power grid of the hybrid current transformer cluster are specifically calculated as follows:
based on the grid-built converter cluster aggregation impedance model and the grid-following converter cluster aggregation impedance model, determining an equivalent circuit model of the independent power grid of the hybrid converter cluster according to a circuit topological structure, respectively carrying out positive sequence disturbance injection and negative sequence disturbance injection on the equivalent circuit model of the independent power grid, and decoupling based on a kirchhoff current law and a kirchhoff voltage law to obtain the positive sequence equivalent circuit model and the negative sequence equivalent circuit model of the independent power grid of the hybrid converter cluster.
5. The method for analyzing and actively controlling the stability of the independent power grid of the hybrid converter cluster according to claim 1, wherein the active stability control strategy for performing power coordination optimization regulation based on the central controller comprises the following steps:
based on positive sequence and negative sequence equivalent circuit models of the independent power grid of the hybrid converter cluster, analyzing the influence of output power of the grid-built converter cluster and the grid-following converter cluster on the system stability by adopting a Nyquist stability analysis method, determining the change trend of the system stability along with the output power of the grid-following converter cluster, and establishing a grid-following converter cluster active power and reactive power regulation command database for maintaining the system operation; and after the system is determined to be unstable due to small interference, the central controller adjusts the active power reference value and the reactive power reference value of the follow-up network type converter based on the database self-adaptive issuing instruction.
6. The stability analysis and active control system of the independent power grid of the hybrid converter cluster is characterized by comprising the following components:
the small signal model calculation module is used for establishing a grid-formed current transformer voltage-current relation model and a grid-following current transformer voltage-current relation model; the cluster impedance aggregation calculation module is used for solving a cluster impedance aggregation model of the current transformer; the independent power grid stability analysis module is used for analyzing the stability of the independent power grid system of the hybrid converter cluster and establishing a system stable operation maintenance instruction database; and the active stability control module is used for performing active control when the system is unstable due to small interference, so that the system is recovered and stabilized.
7. The system for analyzing and actively controlling the stability of a hybrid converter cluster independent power grid according to claim 6, wherein the small signal model calculation module is specifically configured to:
extracting system operation state sampling information from power grid monitoring secondary equipment; and calculating a grid-structured converter voltage-current relation and a grid-connected converter voltage-current relation model based on the sampled voltage-current data, the converter control parameters and the circuit parameters.
8. The system for analyzing and actively controlling the stability of a hybrid converter cluster independent power grid according to claim 6, wherein the cluster impedance aggregation calculation module is specifically configured to:
based on the voltage-current relation model of the grid-structured converter determined by the small signal model calculation module, calculating a cluster aggregation impedance model of the grid-structured converter by combining cluster operation state sampling information; and calculating a cluster aggregation impedance model of the grid-connected converter based on the voltage-current relation model of the grid-connected converter determined by the small signal model calculation module and by combining cluster operation state sampling information.
9. The system for analyzing and actively controlling the stability of an independent power grid of a hybrid converter cluster according to claim 6, wherein the independent power grid stability analyzing module is specifically configured to:
based on the cluster impedance of the grid-structured converter and the cluster impedance of the grid-following converter obtained by the cluster impedance aggregation calculation module, by combining with the operation state sampling information of the independent power grid, and adopting a Nyquist stability criterion, the stability analysis of the independent power grid is carried out, the influence of the change of the active power and the reactive power output by the grid-following converter on the stability of the system is analyzed, and based on the analysis result, a regulation command database of the active power and the reactive power of the grid-following converter cluster required for maintaining the stable operation of the system is established.
10. The system for analyzing and actively controlling the stability of a hybrid converter cluster independent power grid according to claim 6, wherein the active stability control module is specifically configured to:
receiving a system small interference instability signal, and generating a power control instruction of the grid-following converter cluster according to an active power and reactive power instruction database of the grid-following converter cluster of the independent power grid stability analysis module and combining the energy storage residual electric quantity of the grid-forming converter; and low bandwidth communication is adopted to send the power control instruction to the following network type converter cluster.
11. A computer 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 to cause the at least one processor to perform the hybrid converter cluster independent grid stability analysis and active control method of any of claims 1-5.
12. A computer readable storage medium, wherein the computer readable storage medium stores computer instructions for causing the computer to perform the hybrid converter cluster independent grid stability analysis and active control method of any one of claims 1-10.
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