CN107994573B - Multi-objective optimization design method for multi-terminal flexible direct current power transmission system - Google Patents
Multi-objective optimization design method for multi-terminal flexible direct current power transmission system Download PDFInfo
- Publication number
- CN107994573B CN107994573B CN201711287515.4A CN201711287515A CN107994573B CN 107994573 B CN107994573 B CN 107994573B CN 201711287515 A CN201711287515 A CN 201711287515A CN 107994573 B CN107994573 B CN 107994573B
- Authority
- CN
- China
- Prior art keywords
- transmission system
- voltage
- flexible direct
- direct current
- sub
- 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.)
- Active
Links
- 230000005540 biological transmission Effects 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000005457 optimization Methods 0.000 title claims abstract description 34
- 238000013461 design Methods 0.000 title claims abstract description 18
- 239000003990 capacitor Substances 0.000 claims abstract description 58
- 238000004422 calculation algorithm Methods 0.000 claims abstract description 13
- 238000004364 calculation method Methods 0.000 claims abstract description 12
- 230000002068 genetic effect Effects 0.000 claims abstract description 8
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 238000012544 monitoring process Methods 0.000 claims abstract description 4
- 238000004088 simulation Methods 0.000 claims abstract description 4
- 238000012163 sequencing technique Methods 0.000 claims description 14
- 230000001052 transient effect Effects 0.000 claims description 5
- 230000000630 rising effect Effects 0.000 claims description 4
- 230000014759 maintenance of location Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000007717 exclusion Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000012545 processing Methods 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
-
- 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
- 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)
- Inverter Devices (AREA)
Abstract
The invention discloses a multi-objective optimization design method for a multi-terminal flexible direct current power transmission system, which comprises the following steps: building a multi-terminal flexible direct current power transmission system model; starting the model simulation of the multi-terminal flexible direct current transmission system; detecting the direct current capacitor voltage of each submodule of the multi-terminal flexible direct current transmission system in real time; monitoring the direction of current of each bridge arm of the multi-end flexible direct-current power transmission system in real time to serve as a judgment basis for capacitor charging and discharging; calculating the number m of sub-modules required to be switched on by the jth bridge arm of the ith-end VSC in each switching period
ijCorrecting the capacitor voltage through the parameter to be optimized; determining the input cutting-off state of the sub-module, transmitting the input cutting-off state to a control system, and establishing a voltage fluctuation objective function and a switching frequency objective function during stable operation; and solving the optimal solution set of the optimization variables by adopting a multi-objective genetic algorithm. The invention meets the requirements of better voltage balance effect and lower switching frequency at the same time, enables both the voltage balance effect and the switching frequency to better meet the requirements, has higher calculation efficiency, and is particularly suitable for occasions of multi-terminal flexible direct current power transmission.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a multi-target optimization design method for a multi-terminal flexible direct current power transmission system.
Background
A Multi-terminal flexible direct current transmission system (VSC-MTDC) refers to a flexible direct current transmission system that includes 3 or more Voltage Source Converter stations (VSCs) under the same direct current grid. The power supply device has the most remarkable characteristic of realizing multi-power supply and multi-drop point power receiving. As a more flexible and faster power transmission mode, the multi-end flexible direct-current power transmission system has wide application prospects in the fields of wind power and other new energy grid connection, urban direct-current power distribution network construction and the like. With the rapid development of the voltage source converter, the direct current transmission system based on the voltage source converter has become the main trend of the development of the direct current transmission system. Among numerous voltage source converter topologies, a Modular Multilevel Converter (MMC) based on H half-bridge cascade is one of the preferred topologies of the VSC-MTDC engineering in the future due to the advantages of low switching frequency, small harmonic content, capability of expanding to any level, and the like.
Each converter bridge arm in the MMC direct current transmission project is provided with a plurality of sub-modules (SM), and the equalization of SM capacitor voltage becomes a problem which cannot be avoided in the application of the MMC project. In actual engineering, the number of SMs is very large, and a traditional voltage-sharing method generally adopts an SM capacitor voltage sequencing gating method, but sequencing of pure capacitor voltages causes high switching loss, and when the number of bridge arms SM is too large, sequencing of SM voltages with the number reaching hundreds or even thousands of scattered arrangements is undoubtedly a great engineering difficulty, and energy balance among SMs becomes very difficult. Moreover, the number of the ends of the multi-end flexible direct-current transmission system is more than that of the traditional direct-current transmission system, the number of the sub-modules is increased in a multiple mode, and the required calculated amount is more complex.
In the balancing method of the invention, a group of voltage upper and lower limits are set near a rated value of the capacitor voltage, and the balance control is mainly put on the SM with the capacitor voltage out of limit, so that the direct current capacitor voltage fluctuation can be reduced to a very small range by processing and then sequencing according to the out-of-limit condition, but frequent switching on and off of the switching frequency in the SM is caused, and the switching frequency of the MMC is increased. The capacitor voltage-sharing algorithm for maintaining the sequencing is added, so that the state maintaining parameters are introduced, the unnecessary repeated switching phenomenon of the same Insulated Gate Bipolar Transistor (IGBT) caused by the sequencing algorithm is effectively avoided, and the loss is reduced.
Therefore, in the traditional voltage-sharing method, the capacitance-voltage balance of the SM and the switching frequency of the MMC are in a pair of contradictions, the mutual exclusion of the two targets cannot be met at the same time, and an effective solution for solving the problems is still lacking in the prior art.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a multi-objective optimization design method of a multi-terminal flexible direct-current transmission system.
A multi-objective optimization design method for a multi-terminal flexible direct current power transmission system comprises the following steps:
the method comprises the following steps: building a multi-terminal flexible direct-current power transmission system model in power system transient simulation software according to actual engineering;
step two: setting initial parameters of model operation and initial values of parameters to be optimized;
step three: starting the model simulation of the multi-terminal flexible direct current transmission system;
step four: detecting the direct current capacitor voltage of each submodule of the multi-terminal flexible direct current power transmission system in real time and storing the direct current capacitor voltage in real time;
step five: monitoring the direction of current of each bridge arm of the multi-end flexible direct-current power transmission system in real time to serve as a judgment basis for capacitor charging and discharging and storing the judgment basis in real time;
step six: calculating the number m of sub-modules required to be switched on by the jth bridge arm of the ith-end VSC in each switching period according to a nearest level approximation debugging method
ijVSC is a voltage source converter station;
step seven: correcting the capacitor voltage through the parameter to be optimized;
step eight: determining the input cutting state of the sub-modules according to the capacitor voltage sequencing result and transmitting the input cutting state to a control system;
step nine: judging whether the model operation is finished, if so, turning to the step ten, otherwise, performing the next switching period calculation, and returning to the step four until the model operation is finished;
step ten: establishing a voltage fluctuation objective function and a switching frequency objective function during stable operation;
step eleven: solving an optimal solution set of the optimization variables by adopting a multi-objective genetic algorithm; and judging whether the maximum algebra is reached, if so, obtaining the optimal value of the optimal solution set of the variable parameters and applying the optimal value to the actual project of the multi-terminal flexible direct current power transmission system, and if not, adding 1 to the optimized algebra and returning to the step three to perform the next cycle calculation.
Further, in the second step, the initial parameter of the model operation includes a model operation time, and the initial value of the parameter to be optimized includes an initial value of a state maintaining parameter, an initial value of a state changing parameter, an initial value of a voltage rising parameter, and an initial value of a voltage falling parameter of a jth bridge arm of the ith-end VSC of the multi-end flexible direct-current transmission system.
Further, an iterative optimization algebra of the multi-target genetic algorithm is also set in the second step.
Further, in the seventh step, the correcting the capacitor voltage according to the parameter to be optimized specifically includes:
the j-th bridge arm of the i-th end VSC multiplies the SM capacitor voltage in the input state by a state change parameter h when the current flows to the SM, namely the SM is charged
2ijMultiplying the SM capacitor voltage in the cut-off state with the capacitor voltage below the lower voltage limit by a voltage droop parameter l
2ij。
Further, in the seventh step, when the current flows out of the SM, that is, the SM discharges, in the jth arm of the i-th VSC, the capacitor voltage of the SM in the discharge state is multiplied by the state maintaining parameter h
1ij(ii) a Multiplying the SM capacitor voltage in the cut-off state with the capacitor voltage above the upper voltage limit by a voltage rise parameter l
1ij。
Further, in the eighth step, the SMs of the jth bridge arm of the ith-end VSC of the multi-end flexible direct-current transmission system are sorted according to the capacitance voltage values, and if the current flows to the SM, that is, the SM is charged, m is input according to the sequence of the capacitance voltage from high to low
ijCutting off the rest SM; if the current flows out of the SM, namely the SM discharges, m is put into the capacitor according to the sequence from low to high of the capacitor voltage
ijCutting off the rest SM;
and transmitting the SM switching state of each bridge arm of the flexible direct current power transmission system to a control system to control the switching state of the sub-modules.
Further, in the step ten, a voltage fluctuation objective function and a switching frequency objective function during stable operation are established: state maintaining parameter h of multi-terminal flexible direct current transmission system
1ijA state change parameter h
2ijVoltage rise parameter l
1ijVoltage drop parameter l
2ijAs an optimization variable [ h ]
1ijh
2ijl
1ijl
2ij](ii) a Establishing a voltage fluctuation objective function F during stable operation
1And switching times objective function F
2。
Further, the voltage fluctuation objective function F
1Defined as the maximum value of the fluctuation amount of the capacitance voltage of all the submodules in the statistical stable operation time:
F
1＝max(|U
Cijz-U
C|)
wherein, U
CijkThe capacitance voltage of the z-th sub-module of the j-th bridge arm of the i-th end VSC of the multi-end flexible direct current transmission system in one switching period is obtained; u shape
CIs the rated capacitor voltage of the submodule.
Further, the switching frequency objective function F
2Defined as statistically stable running timeSwitching times of all sub-modules in the system:
wherein, X
ij(k) The switching times of all sub-modules on the jth bridge arm of the ith-end VSC in the kth switching period are set; s
ijz(k) Is the working state of the z-th sub-module of the j-th bridge arm of the ith-end VSC of the kth switching period, S
ijz(k +1) is the working state of the z-th sub-module of the j-th bridge arm of the ith-end VSC in the (k +1) -th switching period.
Further, the method comprises the eleventh step of selecting a Pareto optimal solution by adopting a multi-target decision model based on Nash equilibrium points.
Further, the multi-target optimization method of the multi-terminal flexible direct current transmission system is characterized in that the applied multi-terminal flexible direct current transmission system is composed of four-terminal voltage source converter stations (VSC), the VSC of the VSC adopts a topological structure of modular cascade multi-level MMC, each phase of the VSC comprises an upper bridge arm and a lower bridge arm, the structure of each phase is the same, and the AC side is connected with a series reactance L
sAnd a resistance R
s；L
0The bridge arms are connected in series between an upper bridge arm and a lower bridge arm;
each bridge arm is formed by connecting n identical submodules SM in series, and each submodule comprises two IGBTs, a freewheeling diode and a direct-current capacitor; when the upper IGBT of the sub-module is switched on and the lower IGBT of the sub-module is switched off, the sub-module is put into use; when the lower IGBT of the sub-module is switched on and the upper IGBT of the sub-module is switched off, the sub-module is cut off, and the control of the output voltage of the sub-module can be realized through the switching of the switch state.
Compared with the prior art, the invention has the beneficial effects that:
(1) the traditional method can only meet the requirements of reducing the fluctuation of the capacitor voltage or reducing the switching frequency, and the mutual exclusion of the two targets can not be met at the same time. According to the invention, the SM capacitor voltage can be better corrected and the capacitor voltage sequencing effect can be optimized through multi-objective optimization design of the state holding parameter, the state change parameter, the voltage rising parameter and the voltage falling parameter, and meanwhile, the better voltage balance effect and the lower switching frequency are met, so that the SM capacitor voltage and the capacitor voltage can better meet the requirements.
(2) The traditional method can only calculate the switching state of one bridge arm submodule through one-time calculation, the multi-terminal flexible direct current transmission system at least comprises nine bridge arms of three-terminal VSC, and the capacity voltage-sharing optimization calculation amount is huge. According to the method, the minimum voltage fluctuation and the minimum switching times are taken as optimization targets, the state maintaining parameters, the state change parameters, the voltage rising parameters and the voltage falling parameters are optimized simultaneously by adopting an intelligent parallel algorithm, the switching states of the sub-modules on a plurality of VSC bridge arms can be obtained simultaneously, and the calculation efficiency is higher.
(3) According to the invention, a multi-terminal flexible direct-current transmission system model is built in power system transient simulation software according to engineering practice, the electric quantity in a multi-terminal flexible direct-current transmission system is detected in real time, the number of sub-modules required to be switched on by each bridge arm is calculated according to a recent level approximation debugging method, the multi-terminal flexible direct-current transmission system model is operated for multiple times, namely, the multi-iterative optimization of a multi-objective genetic algorithm NSGA-II is carried out, the values of a state holding parameter, a state change parameter, a voltage rise parameter and a voltage fall parameter are continuously optimized, the minimum fluctuation of capacitance and voltage and the minimum switching frequency of a sub-module during stable operation are realized, and a multi-objective optimization design result is applied to the actual multi-. The method meets the requirements of a better voltage balance effect and a lower switching frequency at the same time, enables the voltage balance effect and the switching frequency to meet the requirements better, has higher calculation efficiency, and is particularly suitable for occasions of multi-terminal flexible direct current power transmission.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of a multi-objective optimization design method for a multi-terminal flexible direct current transmission system;
FIG. 2 is a schematic diagram of a main connection of a multi-terminal flexible DC power transmission system project;
fig. 3 is a schematic diagram of a single-ended main circuit of a multi-ended flexible dc power transmission system;
fig. 4 is a schematic diagram of Pareto optimal solution set of optimization parameters of a multi-terminal flexible direct current transmission system.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As introduced in the background art, in the prior art, there is a pair of contradiction between capacitance voltage balance of the SM and switching frequency of the MMC, and the two objectives are mutually exclusive and cannot be met at the same time.
In an exemplary embodiment of the present application, a schematic main connection diagram of a multi-terminal flexible dc transmission system project, which is composed of four-terminal voltage source converter stations (VSC), is provided as shown in fig. 2.
FIG. 3 is a schematic diagram of a main circuit of a voltage source converter station (VSC) of a multi-terminal flexible direct current transmission system, which adopts a topological structure of modular cascade multi-level (MMC), wherein each phase of the VSC comprises an upper bridge arm and a lower bridge arm, the structure of each phase is the same, and a series reactance L is connected to an alternating current side
sAnd a resistance R
s；L
0The current can be restrained to a certain extent by connecting the upper bridge arm and the lower bridge arm in series. Each timeEach bridge arm is formed by connecting n identical Submodules (SM) in series, and each submodule comprises two IGBTs, a freewheeling diode and a direct-current capacitor. When the upper IGBT of the sub-module is switched on and the lower IGBT of the sub-module is switched off, the sub-module is put into use; and when the lower IGBT of the sub-module is switched on and the upper IGBT of the sub-module is switched off, the sub-module is cut off. The control of the output voltage of the sub-module can be realized by switching the switch state.
In actual engineering, a multi-terminal flexible direct current transmission system comprises more than 3 voltage source converter stations (VSC), the number of SMs is very large, a method for sequencing and gating SM capacitor voltages is generally adopted in a traditional voltage-sharing method, sequencing of pure capacitor voltage sharing causes high switching loss, sequencing of SM voltages with the number reaching hundreds or even thousands of distributed arrangement is undoubtedly a huge engineering difficulty when the number of bridge arms SM is too large, and energy balance among SMs is also very difficult.
As shown in fig. 1, the multi-objective optimization design method for the multi-terminal flexible direct current power transmission system of the invention specifically comprises the following steps:
(1) building a multi-terminal flexible direct-current power transmission system model in power system transient simulation software according to engineering practice, and setting the model running time to be 1 second; setting initial values of parameters to be optimized: state maintaining parameter initial value h of jth bridge arm of ith-end VSC of multi-end flexible direct-current transmission system
1ij1.02, variable range [ 1.0-1.05%](ii) a Initial value h of state change parameter
2ij0.98, and the variation range is 0.95-1.0](ii) a The initial value of the voltage rise parameter is l
1ij1.05, and the variation range is [ 1.0-1.1 ]](ii) a Initial value of voltage droop parameter l
2ij0.95, and the variation range is 0.9-1.0](ii) a Setting an iterative optimization algebra Gen of a multi-target genetic algorithm NSGA-II to be 50;
(2) starting the simulation of a multi-terminal flexible direct-current power transmission system in the transient simulation software of the power system;
(3) detecting the direct current capacitor voltage of each submodule in the multi-terminal flexible direct current power transmission system in real time and storing the direct current capacitor voltage in real time aiming at each switching period; and monitoring the direction of the current of each bridge arm of the multi-end flexible direct current transmission system in real time, taking the direction as a judgment basis for charging and discharging of the capacitor, and storing the direction in real time.
(4) Calculating the number m of sub-modules required to be switched on by the jth bridge arm of the ith-end VSC in each switching period according to a nearest level approximation debugging method
ij；
(5) The j-th bridge arm of the i-th end VSC multiplies the SM capacitor voltage in the input state by a state change parameter h when the current flows to the SM, namely the SM is charged
2ijMultiplying the SM capacitor voltage in the cut-off state with the capacitor voltage below the lower voltage limit by a voltage droop parameter l
2ij(ii) a When current flows out of SM, namely SM discharges, the capacitor voltage of SM in the discharge state is multiplied by a state holding parameter h
1ij(ii) a SM capacitor voltage in the off state with the capacitor voltage above the upper voltage limit multiplied by a voltage rise parameter l
1ij；
(6) In the switching period, sequencing the SM of the jth bridge arm of the ith-end VSC of the multi-end flexible direct-current transmission system according to the capacitance voltage value, and inputting m according to the sequence of capacitance voltage from high to low if the current flows to the SM, namely SM is charged
ijCutting off the rest SM; if the current flows out of the SM, namely the SM discharges, m is put into the capacitor according to the sequence from low to high of the capacitor voltage
ijCutting off the rest SM;
(7) and in the switching period, the SM switching state of each bridge arm of the flexible direct current power transmission system is transmitted to the control system to control the switching state of the sub-modules.
(8) Repeating the step (2) to the step (7) in the next switching period until the model operation is finished;
(9) state maintaining parameter h of multi-terminal flexible direct current transmission system
1ijA state change parameter h
2ijVoltage rise parameter l
1ijVoltage drop parameter l
2ijAs an optimization variable [ h ]
1ijh
2ijl
1ijl
2ij](ii) a The steady running time is generally taken to be a time period between 0.5 and 0.7 seconds; establishing a voltage fluctuation objective function F during stable operation
1And switching times objective function F
2；
Voltage fluctuation objective function F
1Defined as the maximum value of the fluctuation amount of the capacitance voltage of all the submodules in the statistical stable operation time:
F
1＝max(|U
Cijz-U
C|)
wherein, U
CijkThe capacitance voltage of the z-th sub-module of the j-th bridge arm of the i-th end VSC of the multi-end flexible direct current transmission system in one switching period is obtained; u shape
CThe rated capacitance voltage of the submodule is obtained;
switching frequency objective function F
2Defined as counting the switching times of all submodules in the stable running time:
wherein, X
ij(k) The switching times of all sub-modules on the jth bridge arm of the ith-end VSC in the kth switching period are set; s
ijz(k) Is the working state of the z-th sub-module of the j-th bridge arm of the ith-end VSC of the kth switching period, S
ijz(k +1) is the working state of the z-th sub-module of the jth bridge arm of the ith-end VSC in the (k +1) th switching period;
(10) solving optimization variable [ h ] by adopting multi-objective genetic algorithm NSGA-II
1ijh
2ijl
1ijl
2ij]Iteratively optimizing an algebraic Gen plus 1 for the Pareto optimal solution set;
(11) if the iterative optimization algebra Gen is less than or equal to 50, repeating the steps (2) to (10);
(12) selecting Pareto optimal solution [ h ] by adopting a multi-target decision model based on Nash equilibrium points
1ijh
2ijl
1ijl
2ij]As shown in fig. 4, the method is applied to the actual engineering of the multi-terminal flexible direct-current transmission system.
The invention aims at the problem that the traditional method can only reduce the fluctuation of the capacitor voltage or reduce the switching frequency, and the mutual exclusion of the two targets can not be met at the same time. The optimal working state S of three bridge arms of the flexible direct current transmission system is obtained by the method
*Can simultaneously reduce the submodule and the switching frequency, and solves the problem of electricity of the flexible direct current transmission systemThe fundamental problem of pressure-equalizing control is solved.
In addition, the traditional method can only obtain the switching state of one bridge arm submodule through one-time calculation, and the traditional sequencing voltage-sharing control method has the calculation complexity of
The computational complexity of the invention is n x n
gen，n
genIs an evolution algebra of an intelligent algorithm. Since the number of bridge arms SM is very large, up to several hundreds or even thousands, n
gen< n. The flexible direct current transmission system comprises three bridge arms, and if the number of the bridge arms of the multi-terminal flexible direct current system is more, the algorithm efficiency is more obvious, and the calculation complexity is lower.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (8)
1. A multi-objective optimization design method for a multi-terminal flexible direct current power transmission system is characterized by comprising the following steps:
the method comprises the following steps: building a multi-terminal flexible direct-current power transmission system model in power system transient simulation software according to actual engineering;
step two: setting initial parameters of model operation and initial values of parameters to be optimized;
step three: starting the model simulation of the multi-terminal flexible direct current transmission system;
step four: detecting the direct current capacitor voltage of each submodule of the multi-terminal flexible direct current power transmission system in real time and storing the direct current capacitor voltage in real time;
step five: monitoring the direction of current of each bridge arm of the multi-end flexible direct-current power transmission system in real time to serve as a judgment basis for capacitor charging and discharging and storing the judgment basis in real time;
step six: calculating the required opening of the jth bridge arm of the ith-end VSC in each switching period according to a nearest level approach debugging methodNumber of general sub-modules m
ijThe VSC is a voltage source type converter station;
step seven: correcting the capacitor voltage through the parameter to be optimized;
step eight: determining the input cutting state of the sub-modules according to the capacitor voltage sequencing result and transmitting the input cutting state to a control system;
step nine: judging whether the model operation is finished, if so, turning to the step ten, otherwise, performing the next switching period calculation, and returning to the step four until the model operation is finished;
step ten: establishing a voltage fluctuation objective function and a switching frequency objective function during stable operation: state maintaining parameter h of multi-terminal flexible direct current transmission system
1ijA state change parameter h
2ijVoltage rise parameter l
1ijVoltage drop parameter l
2ijAs an optimization variable [ h ]
1ijh
2ijl
1ijl
2ij](ii) a Establishing a voltage fluctuation objective function F during stable operation
1And switching times objective function F
2；
The switching frequency objective function F
2Defined as counting the number of switching times of all sub-modules during steady operation:
wherein, X
ij(k) The switching times of all sub-modules on the jth bridge arm of the ith-end VSC in the kth switching period are set; s
ijz(k) Is the working state of the z-th sub-module of the j-th bridge arm of the ith-end VSC of the kth switching period, S
ijz(k +1) is the working state of the z-th sub-module of the jth bridge arm of the ith-end VSC in the (k +1) th switching period;
step eleven: solving an optimal solution set of the optimization variables by adopting a multi-objective genetic algorithm; and judging whether the maximum algebra is reached, if so, obtaining the optimal value of the optimal solution set of the optimized variables and applying the optimal value to the actual project of the multi-terminal flexible direct current power transmission system, and if not, adding 1 to the optimized algebra and returning to the step three to perform the next cycle calculation.
2. The multi-objective optimization design method for the multi-terminal flexible direct current transmission system according to claim 1, wherein in the second step, the initial parameter of the model operation comprises the model operation time, and the initial value of the parameter to be optimized comprises an initial value of a state keeping parameter, an initial value of a state change parameter, an initial value of a voltage rising parameter and an initial value of a voltage falling parameter of a jth bridge arm of an ith-terminal VSC of the multi-terminal flexible direct current transmission system.
3. The multi-objective optimization design method of the multi-terminal flexible direct current transmission system according to claim 2, wherein an iterative optimization algebra of a multi-objective genetic algorithm is further set in the second step.
4. The multi-objective optimization design method for the multi-terminal flexible direct-current transmission system according to claim 1, wherein in the seventh step, the correcting the capacitor voltage through the parameter to be optimized specifically comprises:
when the current flows to the submodule, namely the submodule to be charged, the jth bridge arm of the ith-end VSC multiplies the capacitance voltage of the submodule in the input state by a state change parameter h
2ijMultiplying the sub-module capacitor voltage in the cut-off state and with the capacitor voltage lower than the lower voltage limit by a voltage drop parameter l
2ij。
5. The multi-objective optimization design method of the multi-terminal flexible direct-current transmission system according to claim 4, wherein in the seventh step, when current flows out of a submodule, namely a submodule, of a jth bridge arm of the VSC at an ith terminal, the capacitance voltage of the submodule in a discharge state is multiplied by a state retention parameter h
1ij(ii) a Multiplying the sub-module capacitor voltage in the cut-off state and with the capacitor voltage higher than the upper voltage limit by a voltage rise parameter l
1ij。
6.The multi-objective optimization design method of the multi-terminal flexible direct current transmission system according to claim 1, wherein in the step eight, the sub-modules of the j-th bridge arm of the i-th VSC of the multi-terminal flexible direct current transmission system are sorted according to the capacitance voltage values, and if the current flows to the sub-modules, namely the sub-modules, m is thrown according to the sequence of the capacitance voltage from high to low
ijA submodule, and cutting off the rest submodules; if the current flows out of the sub-modules, namely the sub-modules are discharged, m is put into the sub-modules in the sequence from low to high of the capacitor voltage
ijA submodule, and cutting off the rest submodules;
and transmitting the switching state of the sub-module of each bridge arm of the flexible direct current transmission system to a control system to control the switching state of the sub-module.
7. The multi-objective optimization design method for the multi-terminal flexible direct current transmission system according to claim 1, wherein the voltage fluctuation objective function F
1Defined as the maximum value of the fluctuation amount of the capacitance voltage of all the submodules during the statistical stable operation:
F
1＝max(|U
Cijz-U
C|)
wherein, U
CijkThe capacitance voltage of the z-th sub-module of the j-th bridge arm of the i-th end VSC of the multi-end flexible direct current transmission system in one switching period is obtained; u shape
CIs the rated capacitor voltage of the submodule.
8. The multi-objective optimization design method of the multi-terminal flexible direct-current transmission system according to claim 1, wherein in the eleventh step, a Pareto optimal solution is selected by adopting a multi-objective decision model based on Nash equilibrium points.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711287515.4A CN107994573B (en) | 2017-12-07 | 2017-12-07 | Multi-objective optimization design method for multi-terminal flexible direct current power transmission system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711287515.4A CN107994573B (en) | 2017-12-07 | 2017-12-07 | Multi-objective optimization design method for multi-terminal flexible direct current power transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107994573A CN107994573A (en) | 2018-05-04 |
| CN107994573B true CN107994573B (en) | 2020-02-11 |
Family
ID=62036436
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711287515.4A Active CN107994573B (en) | 2017-12-07 | 2017-12-07 | Multi-objective optimization design method for multi-terminal flexible direct current power transmission system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107994573B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109149981B (en) * | 2018-08-20 | 2019-10-25 | 华中科技大学 | A kind of Multipurpose Optimal Method based on genetic algorithm suitable for MMC |
| CN111368489B (en) * | 2020-02-11 | 2023-05-16 | 南方电网科学研究院有限责任公司 | Test sequence modeling method and device for multi-terminal direct current transmission system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016004427A1 (en) * | 2014-07-03 | 2016-01-07 | Massachusetts Institute Of Technology | High-frequency, high-density power factor correction conversion for universal input grid interface |
| CN105281356B (en) * | 2015-11-10 | 2018-12-18 | 中国科学院电工研究所 | A kind of control method for coordinating of Multi-end flexible direct current transmission system |
-
2017
- 2017-12-07 CN CN201711287515.4A patent/CN107994573B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN107994573A (en) | 2018-05-04 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106649927B (en) | FPGA-based real-time simulation combined modeling method for power electronic element | |
| CN103647310B (en) | Swap modules realize MMC battery energy storage system mutually in the method for SOC balance | |
| CN104917406B (en) | Common-mode-injection-based nearest level modulation method for MMC | |
| CN106787884B (en) | The pressure modulator approach and press modulating device that nearest level approaches | |
| CN105245087B (en) | Modularization multi-level converter capacitor voltage-sharing control method based on classification | |
| CN107994573B (en) | Multi-objective optimization design method for multi-terminal flexible direct current power transmission system | |
| CN109617079B (en) | Method for analyzing existence and stability of tidal current solution of direct-current power distribution system | |
| Chen et al. | Sneak circuit theory based approach to avoiding short-circuit paths in reconfigurable battery systems | |
| CN107968433B (en) | Direct-current topological structure for improving utilization efficiency of photovoltaic inverter and control method | |
| CN105356508B (en) | Power grid wind access evaluation system and its method based on PSD-BPA | |
| CN114884312A (en) | High-voltage direct-hanging battery energy storage system and parameter design method | |
| CN109787497A (en) | A kind of ovennodulation method for equalizing voltage of mixed type MMC | |
| CN111464061B (en) | Single carrier modulation loss modeling method for modular medium-voltage high-power inverter power supply | |
| Ismail et al. | Power losses minimization in distribution system using soft open point | |
| CN107968432B (en) | Control method for improving output utilization rate of photovoltaic cell panel | |
| CN110427660B (en) | Simulation method of high-voltage direct-current circuit breaker | |
| Zhong et al. | A bus-based battery equalization via modified isolated cuk converter governed by adaptive control | |
| CN204180008U (en) | A kind of photovoltaic plant based on block coupled in series structure | |
| CN109274285B (en) | Capacitance voltage balancing method of hybrid modular multilevel converter | |
| CN114553020B (en) | Capacitor multiplexing type modular multilevel converter and control method thereof | |
| CN114336700B (en) | Capacity utilization rate control method for medium-voltage direct-hanging energy storage system | |
| CN113300367B (en) | Online rapid identification method for key section of power grid and power transmission limit making method and device | |
| CN114899899A (en) | Method and system for controlling in-phase SOC balance of chain type energy storage system | |
| CN110867885B (en) | Submodule alternation control method of direct current energy consumption device | |
| CN107528488A (en) | Flexible direct current transmission converter valve submodule switching frequency optimization method and control system |
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 | ||
| CB02 | Change of applicant information | ||
| CB02 | Change of applicant information |
Address after: Ji'nan City, Shandong Province Wang Yue Road 250003 No. 2000 Applicant after: Electric Power Research Institute of State Grid Shandong Electric Power Company Applicant after: National Network Intelligent Technology Co., Ltd. Applicant after: Qingdao Power Supply Company, State Grid Shandong Electric Power Company Applicant after: State Grid Corporation of China Address before: Ji'nan City, Shandong Province Wang Yue Road 250003 No. 2000 Applicant before: Electric Power Research Institute of State Grid Shandong Electric Power Company Applicant before: Shandong Luneng Intelligent Technology Co., Ltd. Applicant before: Qingdao Power Supply Company, State Grid Shandong Electric Power Company Applicant before: State Grid Corporation of China |
|
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20210302 Address after: 250002 Wang Yue Road, Ji'nan City, Shandong Province, No. 2000 Patentee after: ELECTRIC POWER RESEARCH INSTITUTE OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee after: Shandong Luneng Software Technology Co.,Ltd. intelligent electrical branch Patentee after: QINGDAO POWER SUPPLY COMPANY OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee after: STATE GRID CORPORATION OF CHINA Address before: 250003 2000 Wang Yue Road, Ji'nan, Shandong Patentee before: ELECTRIC POWER RESEARCH INSTITUTE OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee before: National Network Intelligent Technology Co.,Ltd. Patentee before: QINGDAO POWER SUPPLY COMPANY OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee before: STATE GRID CORPORATION OF CHINA |
|
| CP01 | Change in the name or title of a patent holder | ||
| CP01 | Change in the name or title of a patent holder |
Address after: 250002 Wang Yue Road, Ji'nan City, Shandong Province, No. 2000 Patentee after: ELECTRIC POWER RESEARCH INSTITUTE OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee after: Shandong luruan Digital Technology Co.,Ltd. smart energy branch Patentee after: QINGDAO POWER SUPPLY COMPANY OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee after: STATE GRID CORPORATION OF CHINA Address before: 250002 Wang Yue Road, Ji'nan City, Shandong Province, No. 2000 Patentee before: ELECTRIC POWER RESEARCH INSTITUTE OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee before: Shandong Luneng Software Technology Co.,Ltd. intelligent electrical branch Patentee before: QINGDAO POWER SUPPLY COMPANY OF STATE GRID SHANDONG ELECTRIC POWER Co. Patentee before: STATE GRID CORPORATION OF CHINA |