CN112510769A - Alternating current-direct current hybrid power supply system and online impedance scanning analysis method thereof - Google Patents

Alternating current-direct current hybrid power supply system and online impedance scanning analysis method thereof Download PDF

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CN112510769A
CN112510769A CN202011338172.1A CN202011338172A CN112510769A CN 112510769 A CN112510769 A CN 112510769A CN 202011338172 A CN202011338172 A CN 202011338172A CN 112510769 A CN112510769 A CN 112510769A
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phase
source device
current
power supply
supply system
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CN112510769B (en
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姜云龙
司鑫尧
史明明
张宸宇
刘瑞煌
葛雪峰
肖小龙
苏伟
孙天奎
郭佳豪
缪惠宇
杨景刚
袁晓冬
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State Grid Corp of China SGCC
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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State Grid Corp of China SGCC
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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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
    • H02J4/00—Circuit arrangements for mains or distribution networks not specified as ac or dc
    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • 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
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses an alternating current-direct current hybrid power supply system and an online impedance scanning analysis method thereof, which are used for acquiring an impedance amplitude frequency curve and a phase frequency curve of the direct current power supply system under the current operating power; according to the current running power of the direct current power supply system, extracting an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in the current running power section of the direct current power supply system by inquiring a pre-acquired impedance amplitude frequency curve and a pre-acquired phase frequency curve of the disturbance source device; and judging the current running power section of the direct current power supply system, and obtaining the phase difference between the impedance phase frequency curve of the disturbance source device and the impedance phase frequency curve of the direct current power supply system, which corresponds to the impedance intersection point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system, so as to obtain whether the system is unstable or not. The method and the device realize on-line quick judgment of the instability and the stability margin of the AC/DC hybrid power supply system.

Description

Alternating current-direct current hybrid power supply system and online impedance scanning analysis method thereof
Technical Field
The invention relates to the technical field of electric power, in particular to an alternating current-direct current hybrid power supply system and an online impedance scanning analysis method thereof.
Background
Although the flexible control of the power electronic conversion equipment such as a distributed power supply, energy storage and an alternating current/direct current load in the alternating current/direct current hybrid power supply system is beneficial to quickly responding to the change of the load and power supply, the flexibility of the system is improved, and the operation efficiency of the system is improved, at the same time, the operation characteristic and behavior of the alternating current/direct current hybrid power supply system are also deeply influenced by the nonlinear control characteristic of the power electronic device, because the alternating current/direct current hybrid power supply system shows different impedance characteristics in different frequency bands due to the effect of the power electronic device controlling a large number of power devices to be quickly switched on/off, the system damping is reduced particularly when the direct current load is increased and the number of interconnected ports is increased, even negative damping is generated, and the.
At present, no online impedance scanning analysis method for an alternating current-direct current hybrid power supply system exists, generally, impedance scanning is performed on a full-digital simulation model of a single power electronic device or a primary power loop model of the single power electronic device is placed in a simulator and is in butt joint with an external real secondary controller, impedance scanning is performed in a ring based on controller hardware, and online impedance scanning for a direct current power supply system comprising a plurality of power electronic device devices does not exist.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides an alternating current-direct current hybrid power supply system and an online impedance scanning analysis method thereof, and solves the problem of online impedance scanning of a direct current power supply system comprising a plurality of power electronic equipment devices.
In order to achieve the above purpose, the invention adopts the following technical scheme: an on-line impedance scanning analysis method for an alternating current-direct current hybrid power supply system comprises the following steps:
acquiring corresponding steady-state operation impedance amplitude frequency points and phase frequency points of the direct current power supply system after injection of each voltage disturbance quantity under the current operation power of the direct current power supply system, and connecting the points one by one to obtain an impedance amplitude frequency curve and a phase frequency curve of the direct current power supply system under the current operation power;
according to the current running power of the direct current power supply system, extracting an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in the current running power section of the direct current power supply system by inquiring a pre-acquired impedance amplitude frequency curve and a pre-acquired phase frequency curve of the disturbance source device;
and calculating the phase difference between the impedance phase frequency curve of the disturbance source device and the impedance phase frequency curve of the direct current power supply system, which corresponds to the impedance intersection point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system in the current operating power section of the direct current power supply system, and judging whether the direct current power supply system is unstable or not according to the phase difference.
Further, the pre-acquired impedance amplitude frequency curve and phase frequency curve of the disturbance source device are acquired by the method comprising the following steps:
establishing a primary loop model of the disturbance source device in a real-time simulation system, butting the real-time simulator and a secondary controller of the disturbance source device through an electric/communication interface, changing the running power of the disturbance source device by changing the disturbance current in the primary loop model of the disturbance source device, and acquiring an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in each power section of the disturbance source device in advance.
Further, the disturbance source device primary loop model includes: the three-phase alternating current power grid comprises an equivalent controlled current source, a disturbance source device primary topological structure model and a three-phase alternating current power grid which are sequentially connected in series, wherein a current given signal of the equivalent controlled current source is a steady-state current i0And the disturbance current delta i are superposed.
Further, the method for obtaining the impedance amplitude frequency curve and the phase frequency curve of the disturbance source device in each power section of the disturbance source device in advance by changing the disturbance current in the primary loop model of the disturbance source device, changing the operating power of the disturbance source device, and comprises the following steps:
respectively realizing that the hardware of the disturbance source device controller operates in a loop simulation steady state from 0 to 110% P0N is equal to or greater than 2, N is equal to 1, 2, 3 … … N, Pn is equal to 110% x P0X N/N, steady state current i0＝Pn/U0，U0Setting the rated voltage for the DC output of the DC power supply systemThe initial Δ i is 0; p0Rated power for the disturbance source device;
when the loop simulation runs on Pn in a steady state, setting the value delta i to be k1 multiplied by i0The method comprises the steps of multiplying by sin (2 x pi x f1), wherein k1 is an amplitude coefficient of a current disturbance signal, f1 is a disturbance frequency of a disturbance source device, according to a certain time sequence interval, voltage and current of a direct current input side of the disturbance source device are recorded when working conditions of each disturbance frequency point are simulated and stably run, division calculation of a voltage vector and a current vector is carried out, impedance points of the direct current input side of the disturbance source device under the working conditions of a power section Pn and various disturbance frequencies are obtained, the points are sequentially connected point by point, an nth impedance amplitude frequency curve and a corresponding impedance phase frequency curve of the disturbance source device under the nth power section Pn are obtained, and an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device of each power section are obtained in advance.
Further, the acquiring of the steady-state operating impedance amplitude frequency point and the phase frequency point of the dc power supply system corresponding to the injected voltage disturbance amount under the current operating power of the dc power supply system, and performing point-by-point connection to obtain an impedance amplitude frequency curve and a phase frequency curve of the dc power supply system under the current operating power includes the steps of:
a, B, C three-phase voltage signal u for detecting three-phase alternating current power grida、ubAnd ucThe vector rotation angle theta of the three-phase AC network voltage is obtained by means of a phase-locked loop PLL method and is used together with A, B, C three-phase voltage signals u of the three-phase AC networka、ubAnd ucCalculating d, q axis DC component u of three phase AC network voltaged、uq；
Three-phase current signal i of alternating current output end A, B, C of disturbance source device is detecteda、ibAnd icD-q rotation vector transformation is carried out by utilizing the vector rotation angle theta to obtain a direct current component i under a synchronous rotation d-q axis coordinate systemd、iq；
Voltage command value u for outer ring of DC bus voltage of disturbance source deviceref1Superposing the voltage disturbance quantity delta u to obtain the actual external ring of the DC bus voltage of the disturbance source deviceVoltage command value uref＝uref1Plus Δ u, setting initial Δ u to 0;
the actual voltage instruction value u of the outer ring of the DC bus voltage of the disturbance source devicerefThe difference value of the d-axis reference current i and the actual voltage u1 of the direct current input end of the disturbance source device is obtained through a voltage proportional integral PI regulatordref(ii) a Setting q-axis reference current i output by disturbance source deviceqref＝0；
D-axis reference current i output by disturbance source devicedrefAnd a DC current component idAfter passing through a first current proportional integral PI regulator, the difference value of (A) and (B) is compared with-wLiqAnd d-axis direct-current component u of three-phase alternating-current network voltagedAdding to obtain d-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemd1(ii) a Q-axis reference current i output by disturbance source deviceqrefAnd a DC current component iqAfter passing through a second current proportional integral PI regulator, the difference value of (A) and (B) is compared with wLidAnd q-axis direct-current component u of the three-phase network voltageqAdding to obtain q-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemq1Wherein, w is the angular frequency of the three-phase AC power grid voltage, and L is the inductance value of the three-phase filter reactor;
using the vector rotation angle theta of the three-phase AC network voltage to convert ud1And uq1Carrying out Park inverse transformation to obtain an alpha axis component u of the voltage modulation signal of the disturbance source device under the two-phase static coordinate systemαAnd a beta axis component uβThen, a pulse width modulation method is adopted to obtain pulse width modulation pulse signals of all IGBT devices in the disturbance source device;
voltage instruction value u of direct current bus voltage outer ring based on disturbance source deviceref1Voltage disturbance amounts Δ U of respective disturbance frequencies are sequentially added and injected at regular time intervals, and the value of Δ U is set to k2 × U0The voltage and the current of a direct current bus output by the direct current power supply system are recorded after the direct current power supply system responds to disturbance and enters steady-state operation, and the voltage and the current pass through the voltageAnd dividing the vector by the current vector, calculating and obtaining the corresponding impedance amplitude frequency point and phase frequency point of the DC power supply system in steady state operation after the disturbance quantity delta u of each disturbance frequency and voltage under the current operation power is injected, and connecting the points one by one to obtain an impedance amplitude frequency curve and a phase frequency curve of the DC power supply system under the current operation power.
Further, whether the direct current power supply system is unstable or not is judged according to the phase difference, and the judging method is as follows: judging whether the phase difference between the impedance phase frequency curve of the disturbance source device corresponding to the impedance cross-point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system and the impedance phase frequency curve of the direct current power supply system is greater than 180 degrees or not in the current running power section of the direct current power supply system, and if the phase difference is greater than 180 degrees, destabilizing the direct current power supply system; if the phase difference is far less than 180 degrees, the stability margin of the direct current power supply system is high; if the phase difference is slightly less than 180 degrees, the stability margin of the direct current power supply system is low, the instability risk exists, and the stability margin is the difference value between 180 degrees and the phase difference.
An AC/DC hybrid power supply system comprising: the system comprises a direct current power supply system, a disturbance source device and a three-phase alternating current power grid which are sequentially connected in series; the disturbance source device is used for realizing alternating current-direct current conversion and generation of disturbance signals.
Further, the primary topology of the disturbance source device includes: and the AC output end of the A-phase bridge arm, the AC output end of the B-phase bridge arm and the AC output end of the C-phase bridge arm are respectively connected with the A-phase, B-phase and C-phase filter reactances of the three-phase filter reactor and then are connected to a three-phase AC power network.
The invention achieves the following beneficial effects: the online disturbance function of the converter device between the direct current power supply system and the alternating current power grid is added, the converter device is transformed into the disturbance source device, and disturbance is injected into the direct current power supply system online, so that the hardware cost investment of a newly-built disturbance source device is reduced, the impedance characteristic curve relation between the direct current power supply system and the disturbance source device is accurately and effectively acquired and analyzed online, whether the alternating current-direct current hybrid power supply system is unstable or not and the stability margin are rapidly judged online, and a new online stability analysis method is provided for the alternating current-direct current hybrid power supply system.
Drawings
FIG. 1 is a schematic diagram of an AC/DC hybrid power supply system;
FIG. 2 is a block diagram of a disturbance source device controller hardware-in-the-loop impedance scan;
FIG. 3 is a schematic diagram of online impedance scanning curve analysis of an online operation condition AC/DC hybrid system.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1:
as shown in fig. 1, an ac/dc hybrid power supply system includes: the direct current power supply system, disturbance source device and three-phase alternating current electric network that establish ties in proper order, the topological structure of once of disturbance source device includes: the AC output end of the A-phase bridge arm, the AC output end of the B-phase bridge arm and the AC output end of the C-phase bridge arm are respectively connected with the A-phase, B-phase and C-phase filter reactances of the three-phase filter reactor and then are connected to a three-phase AC power grid, wherein the A-phase bridge arm is formed by connecting an upper tube IGBT device and a lower tube IGBT device in series, the connection point of an upper tube and a lower tube of the A-phase is the AC output end of the A-phase bridge arm, the B-phase bridge arm is formed by connecting the upper tube IGBT device and the lower tube IGBT device in series, the connection point of an upper tube and a lower tube of the B-phase is the AC output end of the B-phase bridge arm, the C-phase bridge arm is formed by connecting the upper tube IGBT device and the lower tube IGBT device in series, and the connection point of the.
The disturbance source device is used for: alternating current and direct current conversion and generation of disturbance signals are achieved.
Example 2:
an on-line impedance scanning analysis method for an alternating current-direct current hybrid power supply system comprises the following steps:
step 1, establishing a disturbance source device primary loop model in a real-time simulation system, butting a real-time simulator and a disturbance source device secondary controller through an electric/communication interface, changing the running power of the disturbance source device by changing the disturbance current in the disturbance source device primary loop model, and acquiring the impedance amplitude frequency curve and the phase frequency curve of the disturbance source device in each power section in advance;
the disturbance source device secondary controller is used for controlling the disturbance source device to generate disturbance signals and realizing the exchange of power between the alternating current and direct current systems.
As shown in fig. 2, the disturbance source device primary circuit model includes an equivalent controlled current source, a disturbance source device primary topological structure model and a three-phase ac power grid which are sequentially connected in series;
the current given signal of the equivalent controlled current source is composed of a steady-state current i0The disturbance source device controller hardware loop simulation system is formed by superposing disturbance current delta i, the real-time simulator is in butt joint with the disturbance source device secondary controller through an electrical/communication interface, wherein the electrical interface comprises a digital input DI (digital input) interface, a digital output DO (digital output), an analog input AI (analog input) interface and an analog input AO (analog output) interface circuit board card, the communication interface comprises communication interface circuits such as RS232, RS485 and TCP/IP (transmission control protocol/Internet protocol) and corresponding communication protocols, and the purpose that the disturbance source device controller hardware loop simulation steady-state operation is 0-110% P0N power segments Pn between, N ≧ 2, N ═ 1, 2, 3 … … N, preferably, N ═ 110, Pn ═ 110% × P0X N/N, steady state current i0＝Pn/U0，U0Setting initial delta i to be 0 for the direct current output rated voltage of the direct current power supply system; p0Rated power for the disturbance source device;
in-loop simulation of disturbance source device controller hardware is prior art.
When the loop simulation runs on Pn in a steady state, setting the value delta i to be k1 multiplied by i0X sin (2 x pi x f1), wherein k1 is an amplitude coefficient of a current disturbance signal, which can be 1% to 10% in general, f1 is a disturbance frequency of a disturbance source device, f1 is set to be 1, 2, 3 and 4 … … 1000Hz respectively according to a certain time interval, such as 30 seconds, and the working condition simulation of each disturbance frequency point stably runsAnd recording the voltage and the current of the direct current input side of the disturbance source device, performing division calculation of a voltage vector and a current vector to obtain each impedance point of the direct current input side of the disturbance source device under the working conditions that the power section Pn and the disturbance frequency are 1, 2, 3 and 4 … … 1000Hz respectively, connecting the impedance points point by point in sequence to obtain an nth impedance amplitude frequency curve and a corresponding impedance phase frequency curve of the disturbance source device under the nth power section Pn, and obtaining the impedance amplitude frequency curve and the phase frequency curve of the disturbance source device of each power section in advance.
Step 2, according to a secondary control strategy of a disturbance source device, superposing and injecting a voltage disturbance quantity delta u of disturbance frequency, recording the voltage and current of a direct current bus output by the direct current power supply system detected on line after the direct current power supply system responds to disturbance and enters steady-state operation, dividing the voltage vector by a current vector, calculating on line to obtain a corresponding impedance amplitude frequency point and a corresponding phase frequency point of the direct current power supply system after the voltage disturbance quantity delta u of each disturbance frequency under the current operation power of the direct current power supply system is injected, and connecting point by point to obtain an impedance amplitude frequency curve and a phase frequency curve of the direct current power supply system under the current operation power;
the specific process comprises the following steps:
a, B, C three-phase voltage signal u for detecting three-phase alternating current power grida、ubAnd ucThe vector rotation angle theta of the three-phase AC network voltage is obtained by means of a phase-locked loop PLL method and is used together with A, B, C three-phase voltage signals u of the three-phase AC networka、ubAnd ucCalculating d, q axis DC component u of three phase AC network voltaged、uq；
Three-phase current signal i of alternating current output end A, B, C of disturbance source device is detecteda、ibAnd icD-q rotation vector transformation is carried out by utilizing the vector rotation angle theta to obtain a direct current component i under a synchronous rotation d-q axis coordinate systemd、iq；
Voltage command value u for outer ring of DC bus voltage of disturbance source deviceref1Superposing the voltage disturbance quantity delta u with certain amplitude and wide frequency to obtain a direct current bus of the disturbance source deviceActual voltage command value u of voltage outer loopref＝uref1Plus Δ u, setting initial Δ u to 0;
the actual voltage instruction value u of the outer ring of the DC bus voltage of the disturbance source devicerefThe difference value of the d-axis reference current i and the actual voltage u1 of the direct current input end of the disturbance source device is obtained through a voltage proportional integral PI regulatordref；
In order to make the output current of the disturbance source device in the same phase with the voltage of the three-phase alternating current network, a q-axis reference current i output by the disturbance source device is setqref＝0；
D-axis reference current i output by disturbance source devicedrefAnd a DC current component idAfter passing through a first current proportional integral PI regulator, the difference value of (A) and (B) is compared with (-wLi)q) And d-axis direct-current component u of three-phase alternating-current network voltagedAdding to obtain d-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemd1(ii) a Q-axis reference current i output by disturbance source deviceqrefAnd a DC current component iqAfter passing through a second current proportional integral PI regulator, the difference value of (A) and (B) is compared with wLidAnd q-axis direct-current component u of the three-phase network voltageqAdding to obtain q-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemq1Wherein, w is the angular frequency of the three-phase AC power grid voltage, and L is the inductance value of the three-phase filter reactor;
using the vector rotation angle theta of the three-phase AC network voltage to convert ud1And uq1Carrying out Park inverse transformation to obtain an alpha axis component u of the voltage modulation signal of the disturbance source device under the two-phase static coordinate systemαAnd a beta axis component uβThen, pulse width modulation (SVPWM) method is adopted to obtain pulse width modulation pulse signals of each IGBT device in the disturbance source device, such as PWM1, PWM2, PWM3, PWM4, PWM5 and PWM6 in fig. 1, where the pulse width modulation pulse signals drive the disturbance source device to convert the dc power output by the dc power supply system into ac power and incorporate the ac power into the three-phase ac power grid, so as to realize that the actual voltage u1 at the dc input end of the disturbance source device is applied to the actual voltage command value u1 at the dc bus voltage outer ring of the disturbance source devicerefHeel ofTracking control;
voltage instruction value u of direct-current bus voltage outer ring based on disturbance source device on lineref1Voltage disturbance quantity delta U of disturbance frequencies of 1 Hz, 2 Hz and 3 … … 1000Hz are sequentially added and injected at certain time intervals, such as 1 minute, and the delta U is set to be k2 multiplied by U0The method comprises the steps that x sin (2 x pi x f2) is adopted, k2 is an amplitude coefficient of a voltage disturbance signal, 1% to 10% can be generally taken, f2 is disturbance frequency, f2 is 1, 2, 3 and 4 … … 1000Hz respectively set, after a direct-current power supply system responds to disturbance and enters steady-state operation, voltage and current of a direct-current bus output by the direct-current power supply system are recorded, voltage vectors are divided by current vectors, corresponding steady-state operation impedance amplitude frequency points and phase frequency points of the direct-current power supply system after voltage disturbance quantity delta u of each disturbance frequency under current operation power is injected are obtained through online calculation, and impedance amplitude frequency curves and phase frequency curves of the direct-current power supply system under the current operation power are obtained through point-by point connection;
step 3, according to the current running power of the direct current power supply system, extracting an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device of the current running power section of the direct current power supply system by inquiring the impedance amplitude frequency curve and the phase frequency curve of the disturbance source device of each power section which are obtained in advance in the step 1;
judging the current running power section of the direct current power supply system on line, and judging whether the phase difference between the impedance phase frequency curve of the disturbance source device corresponding to the impedance cross-point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system is larger than 180 degrees or not, if the phase difference is larger than 180 degrees, the direct current power supply system is unstable; if the phase difference is far less than 180 degrees, the stability margin of the direct current power supply system is high; if the phase difference is slightly less than 180 degrees, the stability margin of the direct current power supply system is low, and the instability risk exists, wherein the frequency stability margin of the intersection point is the difference between 180 degrees and the phase difference.
As shown in fig. 3, in a certain system operating power section, an impedance amplitude frequency curve of the dc power supply system and an impedance amplitude frequency curve of the disturbance source device intersect at about 4Hz, a phase difference between the two phase frequency curves corresponding to the intersection point is 156 ° and is close to 180 °, a stability margin is (180-; the impedance amplitude frequency curve of the direct current power supply system and the impedance amplitude frequency curve of the disturbance source device are intersected at about 25Hz, the phase difference of the phase frequency curves corresponding to the intersection point is basically 0 degrees, the stability margin is (180-0) which is 180 degrees, and the oscillation risk at about 25Hz does not exist; therefore, the system is stable in the power section of operation of the system, but the stability margin of about 4Hz is only 24 degrees, and certain oscillation risk exists.
The original converter device is transformed into the disturbance source device, the hardware cost input of the newly-built disturbance source device is reduced, the impedance characteristic curve relation between the direct current power supply system and the disturbance source device can be accurately and effectively obtained and analyzed on line, whether the alternating current and direct current hybrid power supply system is unstable or not and the stability margin are rapidly judged on line, and the online stability analysis of the alternating current and direct current hybrid power supply system is supported.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (8)

1. An on-line impedance scanning analysis method for an alternating current-direct current hybrid power supply system is characterized by comprising the following steps: the method comprises the following steps:
acquiring corresponding steady-state operation impedance amplitude frequency points and phase frequency points of the direct current power supply system after injection of each voltage disturbance quantity under the current operation power of the direct current power supply system, and connecting the points one by one to obtain an impedance amplitude frequency curve and a phase frequency curve of the direct current power supply system under the current operation power;
according to the current running power of the direct current power supply system, extracting an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in the current running power section of the direct current power supply system by inquiring a pre-acquired impedance amplitude frequency curve and a pre-acquired phase frequency curve of the disturbance source device;
and calculating the phase difference between the impedance phase frequency curve of the disturbance source device and the impedance phase frequency curve of the direct current power supply system, which corresponds to the impedance intersection point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system in the current operating power section of the direct current power supply system, and judging whether the direct current power supply system is unstable or not according to the phase difference.
2. The on-line impedance scanning analysis method of the alternating current-direct current hybrid power supply system according to claim 1, which is characterized in that: the pre-acquired disturbance source device impedance amplitude frequency curve and phase frequency curve are acquired by the following method:
establishing a primary loop model of the disturbance source device in a real-time simulation system, butting the real-time simulator and a secondary controller of the disturbance source device through an electric/communication interface, changing the running power of the disturbance source device by changing the disturbance current in the primary loop model of the disturbance source device, and acquiring an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in each power section of the disturbance source device in advance.
3. The on-line impedance scanning analysis method of the alternating current-direct current hybrid power supply system according to claim 2, which is characterized in that: the disturbance source device primary loop model comprises: the three-phase alternating current power grid comprises an equivalent controlled current source, a disturbance source device primary topological structure model and a three-phase alternating current power grid which are sequentially connected in series, wherein a current given signal of the equivalent controlled current source is a steady-state current i0And the disturbance current delta i are superposed.
4. The on-line impedance scanning analysis method of the alternating current-direct current hybrid power supply system according to claim 3, which is characterized in that: the method comprises the following steps of changing disturbance current in a primary loop model of the disturbance source device, changing operating power of the disturbance source device, and acquiring an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device in each power section of the disturbance source device in advance, wherein the method comprises the following steps:
respectively realizing that the hardware of the disturbance source device controller operates in a loop simulation steady state from 0 to 110% P0N is equal to or greater than 2, N is equal to 1, 2, 3 … … N, Pn is equal to 110% x P0X N/N, steady state current i0＝Pn/U0，U0Setting initial delta i to be 0 for the direct current output rated voltage of the direct current power supply system; p0Rated power for the disturbance source device;
when the loop simulation runs on Pn in a steady state, setting the value delta i to be k1 multiplied by i0The method comprises the steps of multiplying by sin (2 x pi x f1), wherein k1 is an amplitude coefficient of a current disturbance signal, f1 is a disturbance frequency of a disturbance source device, according to a certain time sequence interval, voltage and current of a direct current input side of the disturbance source device are recorded when working conditions of each disturbance frequency point are simulated and stably run, division calculation of a voltage vector and a current vector is carried out, impedance points of the direct current input side of the disturbance source device under the working conditions of a power section Pn and various disturbance frequencies are obtained, the points are sequentially connected point by point, an nth impedance amplitude frequency curve and a corresponding impedance phase frequency curve of the disturbance source device under the nth power section Pn are obtained, and an impedance amplitude frequency curve and a phase frequency curve of the disturbance source device of each power section are obtained in advance.
5. The on-line impedance scanning analysis method of the alternating current-direct current hybrid power supply system according to claim 1, which is characterized in that: the method comprises the following steps of obtaining corresponding steady-state operation impedance amplitude frequency points and phase frequency points of the direct current power supply system after injection of each voltage disturbance quantity under the current operation power of the direct current power supply system, and connecting the points one by one to obtain an impedance amplitude frequency curve and a phase frequency curve of the direct current power supply system under the current operation power, and comprises the following steps:
a, B, C three-phase voltage signal u for detecting three-phase alternating current power grida、ubAnd ucThe vector rotation angle theta of the three-phase AC network voltage is obtained by means of a phase-locked loop PLL method and is used together with A, B, C three-phase voltage signals u of the three-phase AC networka、ubAnd ucCalculating d, q axis DC component u of three phase AC network voltaged、uq；
Three-phase current signal i of alternating current output end A, B, C of disturbance source device is detecteda、ibAnd icD-q rotation vector transformation is carried out by using the vector rotation angle theta to obtain synchronous rotation dDirect current component i in q-axis coordinate systemd、iq；
Voltage command value u for outer ring of DC bus voltage of disturbance source deviceref1Superposing the voltage disturbance quantity delta u to obtain the actual voltage command value u of the outer ring of the DC bus voltage of the disturbance source deviceref＝uref1Plus Δ u, setting initial Δ u to 0;
the actual voltage instruction value u of the outer ring of the DC bus voltage of the disturbance source devicerefThe difference value of the d-axis reference current i and the actual voltage u1 of the direct current input end of the disturbance source device is obtained through a voltage proportional integral PI regulatordref(ii) a Setting q-axis reference current i output by disturbance source deviceqref＝0；
D-axis reference current i output by disturbance source devicedrefAnd a DC current component idAfter passing through a first current proportional integral PI regulator, the difference value of (A) and (B) is compared with-wLiqAnd d-axis direct-current component u of three-phase alternating-current network voltagedAdding to obtain d-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemd1(ii) a Q-axis reference current i output by disturbance source deviceqrefAnd a DC current component iqAfter passing through a second current proportional integral PI regulator, the difference value of (A) and (B) is compared with wLidAnd q-axis direct-current component u of the three-phase network voltageqAdding to obtain q-axis component u of voltage modulation signal of disturbance source device under two-phase rotating coordinate systemq1Wherein, w is the angular frequency of the three-phase AC power grid voltage, and L is the inductance value of the three-phase filter reactor;
using the vector rotation angle theta of the three-phase AC network voltage to convert ud1And uq1Carrying out Park inverse transformation to obtain an alpha axis component u of the voltage modulation signal of the disturbance source device under the two-phase static coordinate systemαAnd a beta axis component uβThen, a pulse width modulation method is adopted to obtain pulse width modulation pulse signals of all IGBT devices in the disturbance source device;
voltage instruction value u of direct current bus voltage outer ring based on disturbance source deviceref1Sequentially superposing and injecting voltage disturbance quantity delta u of each disturbance frequency according to a certain time sequence interval,setting U as k2 × U0The method comprises the steps of multiplying by sin (2 multiplying by pi multiplying by f2), wherein k2 is an amplitude coefficient of a voltage disturbance signal, f2 is disturbance frequency, after a direct-current power supply system responds to disturbance and enters steady-state operation, the voltage and the current of an output direct-current bus of the direct-current power supply system detected on line are recorded, the voltage vector is divided by the current vector, the corresponding steady-state operation impedance amplitude frequency point and phase frequency point of the direct-current power supply system after the disturbance frequency voltage disturbance quantity delta u under the current operation power is injected are calculated and obtained, and an impedance amplitude frequency curve and a phase frequency curve of the direct-current power supply system under the current operation power are obtained through point-by-point connection.
6. The on-line impedance scanning analysis method of the alternating current-direct current hybrid power supply system according to claim 1, which is characterized in that: and judging whether the direct current power supply system is unstable or not according to the phase difference, wherein the judging method comprises the following steps: judging whether the phase difference between the impedance phase frequency curve of the disturbance source device corresponding to the impedance cross-point frequency between the impedance amplitude frequency curve of the disturbance source device and the impedance amplitude frequency curve of the direct current power supply system and the impedance phase frequency curve of the direct current power supply system is greater than 180 degrees or not in the current running power section of the direct current power supply system, and if the phase difference is greater than 180 degrees, destabilizing the direct current power supply system; if the phase difference is far less than 180 degrees, the stability margin of the direct current power supply system is high; if the phase difference is slightly less than 180 degrees, the stability margin of the direct current power supply system is low, the instability risk exists, and the stability margin is the difference value between 180 degrees and the phase difference.
7. An alternating current-direct current hybrid power supply system is characterized in that: the method comprises the following steps: the system comprises a direct current power supply system, a disturbance source device and a three-phase alternating current power grid which are sequentially connected in series; the disturbance source device is used for realizing alternating current-direct current conversion and generation of disturbance signals.
8. The ac-dc hybrid power supply system according to claim 7, wherein: the primary topology of the disturbance source device comprises: and the AC output end of the A-phase bridge arm, the AC output end of the B-phase bridge arm and the AC output end of the C-phase bridge arm are respectively connected with the A-phase, B-phase and C-phase filter reactances of the three-phase filter reactor and then are connected to a three-phase AC power network.
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