CN113809767A - Novel multi-terminal flexible direct-current power distribution system coordination control method - Google Patents
Novel multi-terminal flexible direct-current power distribution system coordination control method Download PDFInfo
- Publication number
- CN113809767A CN113809767A CN202110795196.8A CN202110795196A CN113809767A CN 113809767 A CN113809767 A CN 113809767A CN 202110795196 A CN202110795196 A CN 202110795196A CN 113809767 A CN113809767 A CN 113809767A
- Authority
- CN
- China
- Prior art keywords
- voltage
- control
- current
- controller
- distribution system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000011159 matrix material Substances 0.000 claims abstract description 14
- 238000004088 simulation Methods 0.000 claims description 17
- 238000013178 mathematical model Methods 0.000 claims description 12
- 238000005259 measurement Methods 0.000 claims description 8
- 238000011217 control strategy Methods 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 230000009471 action Effects 0.000 claims description 2
- 229920001184 polypeptide Polymers 0.000 claims 1
- 102000004196 processed proteins & peptides Human genes 0.000 claims 1
- 108090000765 processed proteins & peptides Proteins 0.000 claims 1
- 238000012795 verification Methods 0.000 claims 1
- 230000004043 responsiveness Effects 0.000 abstract description 4
- 230000000694 effects Effects 0.000 description 10
- 230000005540 biological transmission Effects 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000004044 response Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 240000006829 Ficus sundaica Species 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
-
- 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]
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention belongs to the field of power electronic converter control, and particularly relates to a novel coordination control method for a multi-terminal flexible direct-current power distribution system. On the basis of analyzing the advantages and the disadvantages of the traditional double-closed-loop PI control, the novel URC controller is provided, different working modes are set in the controller according to different parameter matrix values, multi-mode smooth switching of a multi-terminal flexible direct-current power distribution system is realized, the dynamic responsiveness and the power fluctuation of a multi-terminal high-voltage direct-current power grid can be improved, and the stability and the robustness of the system are improved.
Description
Technical Field
The invention belongs to the field of power electronic converter control, and particularly relates to a novel coordination control method for a multi-terminal flexible direct-current power distribution system.
Background
With the rapid development of social economy, high-reliability power supply and high-proportion clean energy friendly access have raised higher requirements on the power transmission technology of the power distribution network. The traditional interconnection switch of the power distribution network only has two states of on and off, and the problems of short-circuit current increase, electromagnetic looped network, circulating power and the like easily occur in the operation process, so that the concept of the multi-port flexible direct-current power distribution system is provided. The multi-end flexible direct-current power distribution system is a novel system based on a power electronic technology, an alternating-current system is decoupled and interconnected in an alternating-current-direct-alternating-current mode, loop closing operation of different feeders is realized, active power and reactive power can be adjusted in four quadrants, and power flow distribution in a power grid can be flexibly adjusted and controlled; in addition, when the system breaks down, the flexible and straight system provides active and reactive emergency support, and power supply reliability is improved.
The voltage stabilization of the direct current side is the premise of normal work of the multi-terminal flexible direct current system. However, the voltage outer ring has a nonlinear characteristic, and disturbance such as sudden port power change and alternating voltage fluctuation can cause voltage fluctuation at the direct current side and affect normal operation of the system. In order to control voltage stability, PI control is adopted in the prior research, but a plurality of PI controllers are arranged in a multi-end flexible-direct system, parameter setting is difficult, control precision is not high, and anti-interference capability is poor. And an inner loop current controller is designed based on model prediction, so that the dynamic response speed of the system is improved, but the problems of integral saturation, low voltage stability and the like of an outer loop PI controller are not considered, and the safe and stable operation of the system is not facilitated. In the existing foreign research, a controller is designed by adopting reverse control, so that the problem of large voltage fluctuation in the system mode switching process is effectively solved, but the control operation amount is increased by carrying out multiple derivatives on the virtual control amount, and the system control complexity is increased.
In view of the defects in the prior art, the inventor develops a novel coordination control method of a multi-terminal flexible direct current power distribution system based on years of abundant experience and professional knowledge of the materials, and combines theoretical analysis and research innovation, and provides a novel URC controller on the basis of analyzing the advantages and the disadvantages of the traditional double closed loop PI control.
Disclosure of Invention
The invention aims to provide a novel coordination control method for a multi-terminal flexible direct current power distribution system, and provides a novel URC controller.
The technical purpose of the invention is realized by the following technical scheme:
the invention provides a novel coordination control method for a multi-terminal flexible direct-current power distribution system, which comprises the following steps:
step 1: firstly, a mathematical model of the multi-end flexible direct-current power distribution system is established, and the characteristics of direct-current voltage control nonlinearity are analyzed on the basis.
Step 2: according to the characteristic of analyzing the nonlinearity of direct current voltage control in the step 1 and the advantages and disadvantages of the traditional double-closed-loop PI control, the novel URC controller is provided on the basis, different working modes are set according to different parameter matrix values in the controller, and multi-mode smooth switching of the multi-terminal flexible direct current power distribution system is achieved.
And step 3: and (3) according to the novel voltage controller designed in the step (2), a four-terminal flexible direct-current power distribution system model is built in Matlab/Siemlink, and the effectiveness and feasibility of the designed voltage controller and the coordinated control strategy are verified through simulation.
Further, in the step 1, firstly, a mathematical model of the multi-end flexible direct current power distribution system is established, and on the basis, the nonlinear characteristic of direct current voltage control is analyzed, so that a novel URC controller designed in the next step is used as a theoretical support.
Furthermore, in the step 2, according to the mathematical model of the multi-terminal flexible direct-current power distribution system established in the step 1, the advantages and the disadvantages of the traditional double-closed-loop PI control are firstly analyzed, and on the basis, a novel URC controller is provided, different working modes are set in the controller according to different parameter matrix values, and multi-mode smooth switching of the multi-terminal flexible direct-current power distribution system is realized.
Furthermore, in the step 3, according to the novel voltage controller designed in the step 2, a four-terminal flexible direct current power distribution system model is built in Matlab/Siemlink, validity and feasibility of the designed voltage controller and a coordination control strategy are verified in a simulation mode, and experimental results show that the designed controller can effectively improve stability and robustness of the multi-terminal flexible direct current power distribution system.
Further, in step 1, the kirchhoff law shows that the three-phase dynamic differential equation at the alternating current side of the voltage source converter is as follows:
wherein: l, R is the equivalent reactance and equivalent resistance of the AC reactor; u shapesk，ik，Urk(k ═ a, b, c) are the grid side voltage, grid side current and VSC ac side voltage, respectively; in order to realize the independent decoupling control of active power and reactive power, dq coordinate transformation is required to be performed on the formula (1), and a mathematical model of the converter under a dq coordinate system is obtained as follows:
in the formula: i.e. idq1For d-and q-axis current components on the AC mains side, Usdq1For the d-and q-axis voltage components on the AC mains side, Urdq1Voltage components of d-axis and q-axis at the outlet of the AC side of the converter, omega is the angular frequency of the power grid, a small scale 1 represents the converter 1, and the voltage component of the d-axis at the side of the power grid is positioned in the direction of the voltage vector of the power grid through a phase-locked loop under the steady state, so that Usd1＝Us，Usq1When the converter AC outlet reactor is 0, the current limiting and filtering effect is mainly played, the actual reactor is weak resistance, the loss of the resistance R is small, and the active power and the reactive power absorbed by the VSC1Can be expressed as:
as can be seen from the equations (4) and (5), the alternating-current side current i is measuredd1，iq1The control can independently control the active and reactive power output by the converter. Under the normal operating condition of electric wire netting, neglecting the transverter loss, system alternating current side and direct current side power keep balance, the power conservation of system is the formula:
in the formula: u shapedcIs the DC side bus voltage, and C is the DC side capacitance. In steady state operation, the dc bus voltage of the system is kept constant, i.e., the left side of equation (6) is equal to 0. Therefore, the system inflow power is equal to the outflow power, so in order to maintain the stability of the direct-current voltage, the smooth transmission of the system active power must be maintained.
In the step 2: the control modes of the inverter are various. Among the control modes, the vector control mode has better control effect and decoupling effect, so the vector control mode is usually selected for converter control. The vector control is designed based on a converter mathematical model under a dq coordinate system and mainly comprises an outer loop controller and an inner loop current controller. The outer ring is controlled by constant direct current voltage and constant reactive power, and a current reference value obtained through a PI control link is sent to the inner ring controller; the current control of the inner ring tracks the reference current value sent into the inner ring by the outer ring in real time by dynamically controlling the output voltage of the converter, thereby realizing the control of the converter. In two-terminal or multi-terminal flexible direct-current transmission, a converter is required to adopt constant direct-current voltage control and cooperate with reactive power control to maintain the active power balance and the direct-current voltage stability of the system. The inner loop current control adopts current feedback voltage feedforward compensation, the response rate of a control system is improved, the steady-state error of current tracking is eliminated through the amplitude limiting PI controller, and the system can be protected by carrying out amplitude limiting on the PI controller.
The basic principle of the traditional double closed loop PI control is introduced, but the problems of large voltage fluctuation, difficult PI parameter setting, integral saturation and the like in the traditional outer loop PI control exist. Based on the method, a novel voltage controller is designed, multi-mode smooth switching of the multi-end flexible direct current power distribution system is achieved, power fluctuation of the multi-end flexible direct current power distribution system in the mode switching process is restrained, dynamic responsiveness of the system is improved, and stability and robustness of the system are enhanced.
The main control architecture of the VSC in the present invention is the designed controller (URC).
Further, the control scheme provided by the invention consists of an internal current controller and an external controller. d axis (i)d,ref) The current reference in (c) is determined by a controller designed to rely on local measurements and upper layer commands. Reference value (i) of q-axis currentq,ref) Determined by a reactive power controller or an ac voltage controller. The structure of the URC is shown in FIG. 4, PsetIs the set power value, AKIs a parameter matrix shown in formula (1), frefIs a frequency reference value, f is a frequency actual measurement value, VdcrefIs a reference value of DC voltage, VdcIs the actual measurement of the dc voltage.
In the controller according to the parameter matrix AKDifferent working modes are set according to different values, so that smooth switching of the switching modes is facilitated. In addition to fixed power control, the parameter matrix A may be usedKThe different selection of values other modes of operation are summarized as follows:
mode 1: frequency control: kpf≠0，KIf≠0，Kpu＝0，KIuWhen the value is 0:
mode 2: controlling direct-current voltage: kpf＝0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref)(9)
mode 3: kpf＝0，KIf＝0，Kpu≠0，KIuIn case of not equal to 0:
mode 4: p-f deceleration control: kpf≠0，KIf＝0，Kpu＝0，KIuWhen the value is 0:
Pref＝Pset+Kpf(fref-f) (11)
mode 5: vdc-f controlling: kpf≠0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref)+Kpf(fref-f) (12)。
in conclusion, the invention has the following beneficial effects:
the invention provides a novel coordination control method for a multi-terminal flexible direct current power distribution system, which can effectively improve the dynamic responsiveness and power fluctuation of the multi-terminal flexible direct current power distribution system and improve the stability and robustness of the system.
Drawings
Fig. 1 shows a VSC topology.
Fig. 2 is a block diagram of a structure of a dual-loop controller of the PI converter.
Fig. 3 is a control block diagram of the VSC converter station.
Fig. 4 is a diagram of the structure of the URC controller in the embodiment.
Fig. 5 is a simulation waveform of the PI control dc voltage port when the ac voltage is suddenly changed in the embodiment.
Fig. 6 is a simulation waveform of the URC controlling dc voltage port ac voltage abrupt change in the embodiment.
Fig. 7 is a simulation waveform of an alternating-current voltage of an active power voltage port of the PI control VSC1 in an embodiment when the alternating-current voltage suddenly changes.
Fig. 8 is a simulation waveform of the URC controlled VSC1 active power voltage port ac voltage sudden change in the embodiment.
FIG. 9 is a simulation waveform of the system when the DC voltage is disturbed under the PI control of the embodiment.
Fig. 10 is a simulation waveform of the system when the dc voltage is disturbed under the control of the URC according to the embodiment.
Fig. 11 is a simulation waveform of a system when active power of VSC1 interferes under PI control according to the embodiment.
Fig. 12 is a simulation waveform of the system when the active power of the VSC1 interferes under the control of the URC according to the embodiment.
Detailed Description
To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined object, the detailed description of the embodiments, features and effects of the novel coordination control method for a multi-terminal flexible dc power distribution system according to the present invention is provided below.
The embodiment of the invention discloses a novel coordination control method for a multi-terminal flexible direct current power distribution system, which comprises the following steps:
step 1: firstly, a mathematical model of the multi-end flexible direct-current power distribution system is established, and the characteristics of direct-current voltage control nonlinearity are analyzed on the basis.
Step 2: according to the characteristic of analyzing the nonlinearity of direct-current voltage control in the step 1 and the advantages and disadvantages of the traditional double-closed-loop PI control, a novel URC controller is provided on the basis, and according to a parameter matrix A in the controllerKDifferent working modes are set according to different values, and multi-mode smooth switching of the multi-terminal flexible direct current power distribution system is achieved.
And step 3: and (3) according to the novel voltage controller designed in the step (2), a four-terminal flexible direct-current power distribution system model is built in Matlab/Siemlink, and the effectiveness and feasibility of the designed voltage controller and the coordinated control strategy are verified through simulation.
Each step is described in further detail below:
in the step 1: the topological structure of the converter VSC is shown in FIG. 1, and according to kirchhoff's law, the three-phase dynamic differential equation at the AC side of the voltage source converter is as follows:
wherein: l, R is the equivalent reactance and equivalent resistance of the AC reactor; u shapesk，ik，Urk(k ═ a, b, c) are the grid side voltage, grid side current and VSC ac side voltage, respectively; in order to realize the independent decoupling control of active power and reactive power, dq coordinate transformation is required to be performed on the formula (1), and a mathematical model of the converter under a dq coordinate system is obtained as follows:
in the formula: i.e. idq1For d-and q-axis current components on the AC mains side, Usdq1For the d-and q-axis voltage components on the AC mains side, Urdq1Voltage components of d-axis and q-axis at the outlet of the AC side of the converter, omega is the angular frequency of the power grid, a small scale 1 represents the converter 1, and the voltage component of the d-axis at the side of the power grid is positioned in the direction of the voltage vector of the power grid through a phase-locked loop under the steady state, so that Usd1＝Us，U sq10, transverter exchanges export reactor and mainly plays current-limiting and filtering action, and the actual reactor is weak resistive nature, and the less its loss of resistance R can be ignored, and the absorptive active power of VSC1 and reactive power can be expressed as:
as can be seen from the equations (4) and (5), the alternating-current side current i is measuredd1，iq1The control can independently control the active and reactive power output by the converter. Under the normal operating condition of electric wire netting, neglecting the transverter loss, system alternating current side and direct current side power keep balance, the power conservation of system is the formula:
in the formula: u shapedcIs the DC side bus voltage, and C is the DC side capacitance. In steady state operation, the dc bus voltage of the system is kept constant, i.e., the left side of equation (6) is equal to 0. Therefore, the system inflow power is equal to the outflow power, so in order to maintain the stability of the direct-current voltage, the smooth transmission of the system active power must be maintained.
In the step 2: the control modes of the inverter are various. Among the control modes, the vector control mode has better control effect and decoupling effect, so the vector control mode is usually selected for converter control. The vector control is designed based on a converter mathematical model under a dq coordinate system and mainly comprises an outer loop controller and an inner loop current controller.
Fig. 2 is a block diagram of a converter dual-loop controller. The outer ring is controlled by constant direct current voltage and constant reactive power, and a current reference value obtained through a PI control link is sent to the inner ring controller; the current control of the inner ring tracks the reference current value sent into the inner ring by the outer ring in real time by dynamically controlling the output voltage of the converter, thereby realizing the control of the converter. In two-terminal or multi-terminal flexible direct-current transmission, a converter is required to adopt constant direct-current voltage control and cooperate with reactive power control to maintain the active power balance and the direct-current voltage stability of the system. The inner loop current control adopts current feedback voltage feedforward compensation, the response rate of a control system is improved, the steady-state error of current tracking is eliminated through the amplitude limiting PI controller, and the system can be protected by carrying out amplitude limiting on the PI controller.
The basic principle of the traditional double closed loop PI control is introduced, but the problems of large voltage fluctuation, difficult PI parameter setting, integral saturation and the like in the traditional outer loop PI control exist. Based on the method, a novel voltage controller is designed, multi-mode smooth switching of the multi-end flexible direct current power distribution system is achieved, power fluctuation of the multi-end flexible direct current power distribution system in the mode switching process is restrained, dynamic responsiveness of the system is improved, and stability and robustness of the system are enhanced. Fig. 3 shows the main control architecture of the proposed VSC, which is mainly characterized by the designed controller (URC).
The control scheme shown in fig. 3 is similar to the conventional double closed loop PI control of VSC-HVDC, and consists of an internal current controller and an external controller. d axis (i)d,ref) The current reference in (c) is determined by a controller designed to rely on local measurements and upper layer commands. Reference value (i) of q-axis currentq,ref) Determined by a reactive power controller or an ac voltage controller. The structure of the URC is shown in FIG. 4, PsetIs the set power value, AKIs a parameter matrix shown in formula (1), frefIs a frequency reference value, f is a frequency actual measurement value, VdcrefIs a reference value of DC voltage, VdcIs the actual measurement of the dc voltage.
In the controller according to the parameter matrix AKDifferent working modes are set according to different values, so that smooth switching of the switching modes is facilitated. In addition to fixed power control, the parameter matrix A may be usedKThe different selection of values other modes of operation are summarized as follows:
mode 1: frequency ofControlling: kpf≠0，KIf≠0，Kpu＝0，KIuWhen the value is 0:
mode 2: controlling direct-current voltage: kpf＝0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref) (9)
mode 3: kpf＝0，KIf＝0，Kpu≠0，KIuIn case of not equal to 0:
mode 4: p-f deceleration control: kpf≠0，KIf＝0，Kpu＝0，KIuWhen the value is 0:
Pref＝Pset+Kpf(fref-f) (11)
mode 5: vdc-f controlling: kpf≠0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref)+Kpf(fref-f) (12)；
in the step 3: in order to verify the tacticity and the effectiveness of the control method of the embodiment, a simulation model of a 10kV four-terminal flexible direct current system is built in MATLAB/Simulink. The system works in a master-slave control mode, wherein the VSC1 is a master converter and works in a U statedc-a Q mode; the VSC2-VSC4 are slave converters and work in a P-Q mode. The simulation parameters for the four-terminal flexurally straight system are shown in table 1.
In the running process of the flexible-straight system, port load change and alternating-current side transient fault can generate interference on the system, three simulation scenes are designed in the text, and PI control strategies and URC control strategies are adopted for comparative analysis. Defining the power inflow direct current side as positive and the outflow as negative, the VSC1-VSC4 active power under the initial state is respectively: -2MW, -1.5MW, 1.5 MW; the reactive power is 0.
The voltage fluctuation of the alternating current side can influence the voltage stability of the direct current side and the system power transmission, and in order to verify the control effect of the provided algorithm under the condition of the voltage fluctuation of the alternating current side, U is set to be 1sdcThe three-phase symmetrical voltage of the alternating-current side of the Q port drops by 30% for 0.1s, and the voltage of the alternating-current side of the Q port returns to normal for 1.1 s. Fig. 5 is a simulation waveform when the ac side voltage fluctuates.
By adopting PI control, when the voltage on the AC side of the VSC1 drops, the DC voltage rises by 6V and is recovered to be stable after 20ms, and the VSC1 has active overshoot of 0.62MW and is recovered to be stable after 24 ms; after the voltage of the alternating current side of the VSC1 recovers, the direct current voltage drops by 7.8V and is recovered to be stable through 18ms, and the VSC1 has active overshoot of 0.89MW and is recovered to be stable through 22 ms. By adopting URC control, when the voltage on the AC side of the VSC1 drops, the DC voltage rises by 2.9V and is recovered to be stable after 10ms, and the VSC1 is overshoot with 0.61MW and is recovered to be stable after 12 ms; after the voltage of the alternating current side of the VSC1 recovers, the direct current voltage drops by 3.4V and is recovered to be stable through 10ms, and the VSC1 is actively overshot by 0.88MW and is recovered to be stable through 11 ms. It can be seen that UdcWhen the voltage of the alternating-current side of the Q port suddenly changes, the URC control is adopted, the voltage fluctuation is effectively reduced, and the voltage and power recovery time is shortened.
In order to verify the control effect of the URC algorithm when multiple disturbances occur simultaneously. When the setting time is 1s, the active power of the VSC3 is suddenly changed from-1.5 MW to-0.5 MW, and U is simultaneously addeddc-the Q port ac side voltage amplitude drops by 30%; 1.1s VSC2 active power was suddenly changed from 2MW to 1MW, while U was simultaneously presentdc-the Q port ac side voltage returns to normal; the VSC4 active power is unchanged.
As shown in fig. 6, with PI control, when disturbance occurs for the first time, the dc voltage rises by 13.7V and recovers to be stable after 30ms, and the VSC1 has an active overshoot of 0.62MW and recovers to be stable after 32 ms; when disturbance occurs for the second time, the direct-current voltage drops by 16V and is recovered to be stable after 24ms, and the VSC1 has active overshoot of 1.26MW and is recovered to be stable after 18 ms. By adopting URC control, when disturbance occurs for the first time, the direct-current voltage rises by 6.5V and is recovered to be stable after 14ms, and the VSC1 has active overshoot of 0.61MW and is recovered to be stable after 16 ms; when disturbance occurs for the second time, the direct-current voltage drops by 7.3V and is recovered to be stable through 12ms, and the VSC1 has active overshoot of 1.2MW and is recovered to be stable through 8 ms. Therefore, when a system has multiple disturbances at the same time, the URC control still has a good anti-interference effect.
Compared with the traditional PI control, the simulation results under different scenes show that the URC controller has better control precision and anti-interference capability, and the stability and robustness of the system are effectively improved.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (11)
1. A novel coordination control method for a multi-terminal flexible direct current power distribution system is characterized by comprising the following steps:
step 1, establishing a mathematical model of a multi-end flexible direct-current power distribution system, and analyzing the characteristic of direct-current voltage control nonlinearity on the basis;
step 2, analyzing the advantages and disadvantages of the traditional double closed loop PI control according to the characteristic of analyzing the direct current voltage control nonlinearity in the step 1, designing a URC controller on the basis, setting different working modes according to different parameter matrix values in the URC controller, and realizing the multi-mode smooth switching of the multi-terminal flexible direct current power distribution system;
and 3, according to the design of the URC controller in the step 2, building a four-end flexible direct current power distribution system model in Matlab/Siemlink, and performing simulation verification on the effectiveness and feasibility of the URC control and coordination control strategy.
2. The novel coordination control method for the multi-terminal flexible direct-current power distribution system according to claim 1, wherein in the step 1, a specific method for establishing a mathematical model of the multi-terminal flexible direct-current power distribution system is as follows, and a three-phase dynamic differential equation at the alternating-current side of the voltage source converter is obtained through kirchhoff's law:
wherein: l, R is the equivalent reactance and equivalent resistance of the AC reactor; u shapesk，ik，Urk(k ═ a, b, c) are the grid side voltage, grid side current and VSC1 ac side voltage, respectively; in order to realize the independent decoupling control of active power and reactive power, dq coordinate transformation is carried out on the formula (1) to obtain a mathematical model of the converter under a dq coordinate system as follows:
in the formula: i.e. idq1For d-and q-axis current components on the AC mains side, Usdq1For the d-and q-axis voltage components on the AC mains side, Urdq1Voltage components of d-axis and q-axis at the outlet of the AC side of the converter, omega is the angular frequency of the power grid, and the voltage component of the d-axis at the side of the power grid in a steady state is positioned in the direction of the voltage vector of the power grid through a phase-locked loop, so that U is the voltage component of the d-axis at the AC side of the convertersd1＝Us，Usq10, transverter exchanges export reactor and plays current-limiting and filtering action, and the actual reactor is weak hindering nature, and its loss that resistance R is less is disregarded, and the absorptive active power of VSC1 and reactive power express as:
by the formulas (4) and (5) through the alternating side current id1，iq1The active power and the reactive power output by the converter are independently controlled, the converter loss is ignored under the condition that a power grid normally operates, the power of an alternating current side and the power of a direct current side of the system are kept balanced, and the power conservation mode of the system is as follows:
in the formula: u shapedcIs the DC side bus voltage, and C is the DC side capacitance.
3. The novel coordination control method for the multi-terminal flexible direct current power distribution system according to claim 1, characterized in that the control mode of the VSC converter is a vector control mode designed based on a converter mathematical model under a dq coordinate system, and comprises an internal current controller and an external controller, and a d-axis i isd,refIs determined by the URC controller, which relies on local measurements and upper layer commands, a reference value i for the q-axis currentq,refDetermined by a reactive power controller or an ac voltage controller.
4. The novel coordination control method for multi-terminal flexible direct current power distribution system according to claim 3, characterized in that in the dq coordinate system, d-axis i isd,refIs determined by the URC controller; reference value i of q-axis currentq,refDetermined by a reactive power controller or an ac voltage controller.
5. A novel polypeptide according to claim 3The coordination control method of the end flexible direct current power distribution system is characterized in that in the URC controller, PsetIs the set power value, AKIs the parameter matrix in equation (1), frefIs a frequency reference value, f is a frequency actual measurement value, VdcrefIs a reference value of DC voltage, VdcIs the actual measured value of the DC voltage, then
Wherein A iskRepresents a parameter matrix, where Kpf＝1.5，KIf＝1.8、Kpu＝2，KIu＝2.5；
According to a parameter matrix A in the URC controllerKDifferent working modes are set according to different values, and smooth switching of the switching modes is achieved.
6. The novel coordinated control method for the multi-terminal flexible direct-current power distribution system according to claim 4, wherein the working modes include: frequency control, DC voltage control, Kpf＝0，KIf＝0，Kpu≠0，KIuNot equal to 0 mode, P-f downshift control and Vdc-f control.
7. The method as claimed in claim 5, wherein the frequency control is Kpf≠0，KIf≠0，Kpu＝0，KIuWhen the value is 0:
8. the method as claimed in claim 5, wherein the DC voltage control is Kpf＝0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref) (9)。
9. the novel multi-terminal flexible direct current power distribution system coordination control method according to claim 5, characterized in that K ispf＝0，KIf＝0，Kpu≠0，KIuThe mode not equal to 0 is that,
10. the method as claimed in claim 5, wherein the P-f speed reduction control is Kpf≠0，KIf＝0，Kpu＝0，KIuWhen the value is 0:
Pref＝Pset+Kpf(fref-f) (11)。
11. the novel multi-terminal flexible direct current power distribution system coordination control method according to claim 5, characterized in that V isdc-f controls arepf≠0，KIf＝0，Kpu≠0，KIuWhen the value is 0:
Pref＝Pset+Kpu(Vdc-Vdcref)+Kpf(fref-f) (12)。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110795196.8A CN113809767A (en) | 2021-07-14 | 2021-07-14 | Novel multi-terminal flexible direct-current power distribution system coordination control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110795196.8A CN113809767A (en) | 2021-07-14 | 2021-07-14 | Novel multi-terminal flexible direct-current power distribution system coordination control method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113809767A true CN113809767A (en) | 2021-12-17 |
Family
ID=78893115
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110795196.8A Pending CN113809767A (en) | 2021-07-14 | 2021-07-14 | Novel multi-terminal flexible direct-current power distribution system coordination control method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113809767A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114285066A (en) * | 2021-12-28 | 2022-04-05 | 国网北京市电力公司 | Power balance coordination control method and system for multi-terminal flexible interconnection power distribution system |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109038642A (en) * | 2018-08-29 | 2018-12-18 | 国网江苏省电力有限公司电力科学研究院 | One kind is from the soft straight system control method of energy storage multiterminal and device |
| CN109149620A (en) * | 2018-09-17 | 2019-01-04 | 国网江苏省电力有限公司电力科学研究院 | One kind is from the soft straight system control method of energy storage multiterminal and system |
| CN110021952A (en) * | 2019-04-18 | 2019-07-16 | 天津大学 | The sagging control coefrficient optimization method of multiterminal flexible direct current system based on small-signal modeling |
| CN110247419A (en) * | 2019-07-11 | 2019-09-17 | 中国能源建设集团江苏省电力设计院有限公司 | It is a kind of suitable for multiterminal back-to-back soft straight control method |
| CN112600239A (en) * | 2020-12-03 | 2021-04-02 | 成都大学 | Wind power grid-connected control method |
| CN113113928A (en) * | 2021-04-12 | 2021-07-13 | 国网江苏省电力有限公司电力科学研究院 | Flexible-direct system direct-current bus voltage control method and device based on deep reinforcement learning |
-
2021
- 2021-07-14 CN CN202110795196.8A patent/CN113809767A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109038642A (en) * | 2018-08-29 | 2018-12-18 | 国网江苏省电力有限公司电力科学研究院 | One kind is from the soft straight system control method of energy storage multiterminal and device |
| CN109149620A (en) * | 2018-09-17 | 2019-01-04 | 国网江苏省电力有限公司电力科学研究院 | One kind is from the soft straight system control method of energy storage multiterminal and system |
| CN110021952A (en) * | 2019-04-18 | 2019-07-16 | 天津大学 | The sagging control coefrficient optimization method of multiterminal flexible direct current system based on small-signal modeling |
| CN110247419A (en) * | 2019-07-11 | 2019-09-17 | 中国能源建设集团江苏省电力设计院有限公司 | It is a kind of suitable for multiterminal back-to-back soft straight control method |
| CN112600239A (en) * | 2020-12-03 | 2021-04-02 | 成都大学 | Wind power grid-connected control method |
| CN113113928A (en) * | 2021-04-12 | 2021-07-13 | 国网江苏省电力有限公司电力科学研究院 | Flexible-direct system direct-current bus voltage control method and device based on deep reinforcement learning |
Non-Patent Citations (6)
| Title |
|---|
| 张海波 等: "VSC-MTDC 系统变截距直流电压下垂控制策略", 电力自动化设备, no. 10, pages 60 - 64 * |
| 王鹤;金儒孔;周宏伟;刘禹彤;: "多端柔性直流输电系统直流电压控制无缝切换方法", 电力系统及其自动化学报, no. 9, pages 93 - 100 * |
| 田园园;廖清芬;刘涤尘;彭思成;邹宏亮;: "基于VSC-HVDC的风电分散并网下垂控制策略", 电力系统自动化, no. 3, pages 109 - 115 * |
| 窦飞 等: "基于深度强化学习的多端背靠背柔性直流系统直流电压控制", 电力系统自动化, pages 1 - 14 * |
| 陈海荣;: "基于VSC的多端直流输电系统的控制策略", 电力建设, no. 8, pages 63 - 68 * |
| 韩笑: "基于VSC-HVDC的风电场联网的协调控制技术研究", CNKI优秀硕士学位论文全文库, no. 3, pages 1 - 62 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114285066A (en) * | 2021-12-28 | 2022-04-05 | 国网北京市电力公司 | Power balance coordination control method and system for multi-terminal flexible interconnection power distribution system |
| CN114285066B (en) * | 2021-12-28 | 2024-02-20 | 国网北京市电力公司 | Power balance coordination control method and system for multi-terminal flexible interconnection power distribution system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109149620B (en) | Self-energy-storage multi-terminal flexible-straight system control method and system | |
| CN109038642B (en) | Self-energy-storage multi-terminal flexible-straight system control method and device | |
| CN108429281A (en) | A kind of LCL type gird-connected inverter parallel virtual impedance adjustment | |
| CN106786647A (en) | A kind of three-phase four-wire system parallel connection non-linear composite control method of APF two close cycles | |
| CN106712552B (en) | A kind of aviation more electric engin VIENNA rectifier control method | |
| CN111555318A (en) | Control method of super-capacitor energy storage grid-connected system based on improved LADRC | |
| CN112688307B (en) | AC/DC hybrid micro-grid controller and control method | |
| CN105262113A (en) | Photovoltaic power generation system reactive power control method based on probabilistic fuzzy neural network | |
| CN101847873A (en) | Novel nonlinear control method for active filter | |
| CN112103983B (en) | Control method based on mixed MMC-HVDC | |
| CN107732959A (en) | The smooth feed forward control method of non-linear differential for distributed light storage grid-connected system | |
| CN113809767A (en) | Novel multi-terminal flexible direct-current power distribution system coordination control method | |
| CN112653176B (en) | Variable working point droop control method for multi-end flexible direct current system | |
| Ma et al. | Second-order linear active disturbance rejection control and stability analysis of energy storage grid-connected inverter | |
| Huang et al. | A novel fuzzy-based and voltage-oriented direct power control strategy for rectifier | |
| CN105977979B (en) | The monocyclic control algolithm of single-phase shunt active power filter | |
| CN115425674B (en) | Double-ring active disturbance rejection control method for bidirectional converter of flexible direct current traction power supply system | |
| CN108736517B (en) | VSG-based inverter type distributed power supply adaptive damping control method | |
| CN112600255B (en) | Energy-storage-free photovoltaic voltage type control method, storage medium and computing device | |
| Wang et al. | Operation control strategy for photovoltaic/battery micro-grid | |
| CN115912450A (en) | Flexible direct-current power transmission system control method and device based on virtual synchronous control | |
| CN112366967B (en) | Parallel inverter power control method based on bidirectional impedance power droop | |
| Zhang et al. | An improved robust model predictive and repetitive combined control for three-phase four-leg active power filters with fixed switching frequency | |
| Yuvaraj et al. | STATCOM Based of Adaptive Control Technique to Enhance Voltage Stability on Power Grid | |
| Zhang et al. | Grid-forming inverter primary control using robust-residual-observer-based digital-twin model |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |