CN114530885B - Net-structured flexible interconnection device and control method thereof - Google Patents
Net-structured flexible interconnection device and control method thereof Download PDFInfo
- Publication number
- CN114530885B CN114530885B CN202210189191.5A CN202210189191A CN114530885B CN 114530885 B CN114530885 B CN 114530885B CN 202210189191 A CN202210189191 A CN 202210189191A CN 114530885 B CN114530885 B CN 114530885B
- Authority
- CN
- China
- Prior art keywords
- phase
- bridge arm
- voltage
- loop
- unit
- 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
- 238000000034 method Methods 0.000 title claims description 70
- 238000004146 energy storage Methods 0.000 claims description 58
- 239000003990 capacitor Substances 0.000 claims description 29
- 238000009826 distribution Methods 0.000 claims description 22
- 230000008569 process Effects 0.000 claims description 12
- 230000001360 synchronised effect Effects 0.000 claims description 11
- 230000002457 bidirectional effect Effects 0.000 claims description 9
- 238000005520 cutting process Methods 0.000 claims description 9
- 230000033228 biological regulation Effects 0.000 claims description 6
- 238000003860 storage Methods 0.000 claims description 5
- 230000009466 transformation Effects 0.000 claims description 5
- 238000012937 correction Methods 0.000 claims description 3
- 238000001914 filtration Methods 0.000 claims description 3
- 230000010354 integration Effects 0.000 claims description 3
- 238000012163 sequencing technique Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 abstract description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 230000001276 controlling effect Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 238000011084 recovery Methods 0.000 description 3
- 238000011217 control strategy Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
-
- 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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
-
- 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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
-
- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses a net-structured flexible interconnection device, which comprises: three phase units, each phase unit comprising three bridge arms; the input sides of the three phase units are input with the same three-phase power supply, the positive end of a first bridge arm of each phase unit is connected with a first power supply through a bridge arm inductor, the positive end of a second bridge arm of each phase unit is connected with a second power supply through a bridge arm inductor, and the positive end of a third bridge arm of each phase unit is connected with a third power supply through a bridge arm inductor; the negative ends of the three bridge arms of each phase unit are connected to serve as the outlet ends of the corresponding phase units, and the outlet ends of each phase unit are connected with the reactor and the first mechanical switch in series between the electric phases of the power grid. The invention adopts a modularized design, is easy to integrate production and redundant expansion, and has higher reliability.
Description
Technical Field
The invention relates to the technical field of power converters, in particular to a net-structured flexible interconnection device and a control method thereof.
Background
With the continuous improvement of the permeability of the distributed new energy, the inherent output uncertainty, the access mode and the diversity of the power generation internet modes of the distributed new energy have increasingly obvious influence on the power distribution network, so that the operation scheduling of the power distribution network faces new challenges. The distribution network faces the serious challenges of safe and stable absorption of source load fluctuation power, inhibition of three-phase imbalance, coordination of multiple main bodies under a market mechanism and the like. Meanwhile, the power electronic device represented by the current transformer can be applied to the distribution network in a large scale, so that the power flow flexible regulation and control capability of the distribution network can be remarkably improved. The key nodes of the distribution network are replaced by the flexible power electronic converter device to replace the traditional tie switch, so that the advantages of bidirectional and flexible regulation and control of the power of the flexible power electronic converter device are fully exerted, the distribution network is converted from the traditional rigid distribution network to the flexible distribution network, and a new solution way can be provided for the problems caused by high-proportion access of the distributed new energy.
The existing flexible interconnection device adopts a scheme of a power frequency transformer and a back-to-back converter, realizes flexible interconnection of a power distribution network by directly controlling port current, and is difficult to realize flexible loop closing due to the fact that voltage amplitude and phase of feeder lines on two sides are unequal when feeder line looped network connection is carried out, closing impact current is easy to generate, service life of a device is influenced, and the flexible loop closing is difficult to realize. When the load of a feeder line suddenly increases, if the spare capacity of the connected feeder line is insufficient, the system is easy to generate frequency and voltage fluctuation, so that the power supply quality is reduced. Meanwhile, under abnormal working conditions such as short-circuit faults and the like of the power distribution network, the conventional flexible interconnection device enters a fault protection or fault ride-through control mode, namely, current output is blocked, the power distribution network voltage is passively waited to recover to be normal, the power distribution network voltage has no voltage supporting capability, and positive effects on the power distribution network voltage recovery after fault clearing cannot be achieved.
Disclosure of Invention
The invention provides a net-structured flexible interconnection device and a control method thereof, which are used for solving the problems of low expansibility, low reliability, low waveform quality and large closing impulse current in the prior art.
The invention provides a net-structured flexible interconnection device, which comprises: three phase units, each of which comprises three bridge arms; the input sides of the three phase units are input with the same three-phase power supply, the positive end of a first bridge arm of each phase unit is connected with a first power supply in the three-phase power supply through a bridge arm inductor in the bridge arm, the positive end of a second bridge arm of each phase unit is connected with a second power supply in the three-phase power supply through a bridge arm inductor in the bridge arm, and the positive end of a third bridge arm of each phase unit is connected with a third power supply in the three-phase power supply through a bridge arm inductor in the bridge arm; the negative ends of the three bridge arms of the first phase unit are connected to serve as the outgoing line end of the first phase unit, and a reactor and a first mechanical switch are connected in series between the outgoing line end of the first phase unit and the first phase of the power grid; the negative ends of the three bridge arms of the second phase unit are connected to serve as outlet ends of the phase unit, and a reactor and a second mechanical switch are connected in series between the outlet ends of the second phase unit and the second phase of the power grid; the negative ends of the three bridge arms of the third phase unit are connected to serve as the outgoing line ends of the phase unit, and a reactor and a third mechanical switch are connected in series between the outgoing line ends of the third phase unit and the third phase of the power grid.
Further, each of the three legs of the phase unit includes: a plurality of energy storage sub-modules connected in series; the energy storage submodule comprises: the full-bridge circuit and the battery energy storage units are connected in parallel at two ends of the capacitor in the full-bridge circuit.
Further, the full bridge circuit includes: full-control type switching tube S 1, full-control type switching tube S 2, full-control type switching tube S 3, full-control type switching tube S 4 and direct current capacitor C 1; The battery energy storage unit comprises a battery pack U E, an energy storage inductor L m, a full-control switching tube S 5 and a full-control switching tube S 6; The fully-controlled switching tube S 1 and the fully-controlled switching tube S 3 are connected in series; the fully-controlled switching tube S 2 and the fully-controlled switching tube S 3 are connected in series; The fully-controlled switching tube S 5 and the fully-controlled switching tube S 6 are connected in series; The fully-controlled switching tube S 1 and the fully-controlled switching tube S 3 which are connected in series, the fully-controlled switching tube S 2 and the fully-controlled switching tube S 4 which are connected in series, The fully-controlled switching tube S 5 and the fully-controlled switching tube S 6 which are connected in series are connected in parallel with each other through a direct-current capacitor C 1; The battery pack U E and the energy storage inductor L m are connected in series and then connected to two ends of the fully-controlled switching tube S 6 in parallel.
The invention also provides a control method of the network-structured flexible interconnection device, which comprises the following steps:
An input side voltage control method of a phase unit; the output side flexible loop closing control method of the three phase units comprises the following steps of; the capacitor voltage control method of the bridge arm unit; the output side parallel/off-grid seamless switching control method of the phase unit; the control method of the energy storage sub-module;
Before closing the loop, firstly executing an input side voltage control method of the phase unit simultaneously; the output side flexible loop closing control method of the three phase units comprises the following steps of; the capacitor voltage control method of the bridge arm unit; executing a seamless switching control method of the output side parallel/off-grid of the phase unit; the control method of the energy storage sub-module;
after closing the loop, executing an input side voltage control method of the phase unit; the capacitor voltage control method of the bridge arm unit; the output side parallel/off-grid seamless switching control method of the phase unit; the control method of the energy storage sub-module;
Specifically, the input side voltage control method of the phase unit comprises the following steps:
step S1.1: collecting capacitance voltage values u Cxyi of all bridge arms in the y-phase unit;
step S1.2: calculating the capacitance voltage sum of all bridge arms in the y-phase unit, and obtaining the direct current component of the capacitance voltage sum through low-pass filtering to be used as a feedback signal of the closed-loop controller
Step S1.3: based on the given value 3nu dc of the sum of the capacitance voltages of all bridge arms in the y-phase unit and the feedback signalThe difference value of the active current reference value i dyi * of the input y phase is obtained;
Step S1.4: calculating an input side current reference value i ayi *、ibyi *、icyi * of each bridge arm of the y-phase unit according to the active current reference value i dyi *;
the output side flexible loop closing control method of the three phase units comprises the following steps:
Step S2.1: before grid connection and loop closing, when closed-loop control is obtained through a voltage presynchronization control process, an output side active current reference value i do * and an output side reactive current reference value i qo * generated by a closed-loop controller are obtained;
Step S2.2: according to the output side active current reference value i do * and the output side reactive current reference value i qo *; calculating the output current reference value i uo *、ivo *、iwo * of each phase unit bridge arm;
The capacitor voltage control method of the bridge arm unit comprises the following steps:
Step S3.1: calculating the average value of the capacitance voltage sum direct current component of each bridge arm of the y-phase unit
Wherein the method comprises the steps ofAndDirect current components respectively representing the sum of capacitance voltages of ay, by and cy bridge arms;
Step S3.2: performing closed-loop control on the difference value between the direct current component of the capacitor voltage sum of each bridge arm and the average value of the direct current component of the capacitor voltage sum of each bridge arm of the y-phase unit by using a proportional-integral controller;
Wherein Δp ays、Δpbys、Δpcys represents the power reference values required to be absorbed or emitted by the ay, by and cy bridge arms respectively;
step S3.3: the distribution of active power among bridge arms is regulated, so that the average value of capacitance voltage of each bridge arm is the same;
Step S3.4: calculating a voltage reference value u ay *、uby *、ucy * of each bridge arm of the y-phase unit;
step S3.5: according to the voltage reference value of each bridge arm, the input or the cutting of the energy storage submodule in each phase of bridge arm is respectively controlled by adopting the nearest level approximation modulation;
step S3.6: when u gd＝ugd1,ugq＝ugq1 is reached, the mechanical switch connected with the output side of each phase is controlled to be closed, and the feeder line loop closing is completed;
the method for controlling the seamless switching of the output side parallel/off-grid of the phase unit comprises the following steps of;
step S4.1: after the grid connection and the loop closing, supporting the frequency and the voltage of the distribution network through automatic power regulation and control at an output side;
Step S4.2: repeating the step S2.1 and the capacitor voltage control method of the bridge arm unit;
The control method of the energy storage sub-module comprises the following steps:
Step S5.1: the reference value P e * of the output power of each battery energy storage unit is calculated, and the specific formula is as follows:
wherein P i represents the total power of the input sides of the three phase units;
Step S5.2: the current reference value i e * of each battery energy storage unit is calculated, and the specific formula is as follows:
Wherein U E represents the voltages at two ends of the storage battery pack;
Step S5.3: according to the current on the inductance in each battery energy storage unit and the reference value P e *, the battery energy storage units are independently controlled
Step S5.4: and respectively controlling the input or the cutting of each energy storage sub-module in each phase of bridge arm by adopting a nearest level approximation modulation algorithm.
Further, the specific process of the step 2.1 is as follows:
Step S2.1.1: collecting three-phase voltages u u1、uv1 and u w1 at the quasi-grid-connected loop feeder line;
Step S2.1.2: the component of the voltage in S2.1.1 under the two-phase synchronous rotation coordinate system is calculated and used as the voltage given value u gd1、ugq1 of the output side grid-connected point, and the specific formula is as follows:
wherein, theta o is the output angle of the feeder voltage phase-locked loop;
Step S2.1.3: collecting three-phase voltages u u、uv and u w of grid-connected points at the output end of the mechanical switch;
Step S2.1.4: the component of the voltage in S2.1.3 under the two-phase synchronous rotation coordinate system is calculated and used as a feedback value u gd、ugq of voltage closed-loop control, and the specific formula is as follows:
Step S2.1.5: and performing closed-loop control on grid-connected point voltage by using a proportional-integral controller, wherein output signals generated by the closed-loop controller are an active current reference value i do * and a reactive current reference value i qo *.
Further, the active power distribution in step S3.3 is as follows:
Where i ciryay *、iciryby *、icirycy * represents the loop reference values of ay, by, and cy bridge arms, respectively, θ y represents the phase of the y-phase output side voltage, and u gd represents the d-axis component of the output side voltage.
Further, the specific process of step S3.4 is as follows:
Step S3.4.1: collecting inductance current in each bridge arm as a feedback value i xy of closed-loop control;
Step S3.4.2: the reference value i xy * of each bridge arm current of the y-phase unit is calculated, and the specific formula is as follows:
Step S3.4.3: taking the difference value of i xy * and i xy as an input signal of a proportional-resonant controller, adding a voltage feedforward term after the output of a closed-loop controller, wherein the reference value of each bridge arm voltage of a y-phase unit is as follows:
further, the specific process of step S4.1 is as follows:
Step S4.1.1: collecting three-phase voltages u u、uv and u w and three-phase currents i u、iv and i w of a grid-connected point at the output end of a mechanical switch, and converting the three-phase voltages and the three-phase currents into a two-phase synchronous rotation coordinate system through the following formula:
Wherein, theta * is the output angle of the power outer loop control;
Step S4.1.2: calculating active power P g and reactive power Q g according to the grid-connected point voltage and current, and using the active power P g and the reactive power Q g as feedback values of closed-loop control;
Step S4.1.3: the output side voltage vector amplitude reference value V * and the phase reference value theta * are calculated according to the following specific formulas:
Wherein, P * and Q * respectively represent an active power given value and a reactive power given value, m p and n q respectively represent active-frequency and reactive-voltage control correction coefficients, a and b are filter coefficients, and theta * is a coordinate transformation angle used for inner loop control;
Step S4.1.4: reference values u gd * and u gq * of the output-side grid-connected point voltage in a two-phase rotation coordinate system:
ugd *＝V*,ugq *＝0
further, the specific process of step S5.3 is as follows:
Step S5.3.1: collecting current on the inductance of each battery energy storage unit as a feedback signal i ei of the closed-loop controller;
Step S5.3.2: when P e * is less than 0, taking the difference value of i e * and i ei as an input signal of a closed-loop controller, wherein the closed-loop controller is a proportional-integral controller, and generating a control signal of a switching tube S 5 of the bidirectional DC/DC converter;
Step S5.3.3: when P e * >0, the difference between i ei and i e * is used as the input signal of a closed-loop controller, wherein the closed-loop controller is a proportional-integral controller, and a control signal of a switching tube S 6 of the bidirectional DC/DC converter is generated.
Further, the specific process of step S5.4 is as follows:
Step S5.4.1: the number n xy of energy storage submodules required to be put into each bridge arm is determined according to the bridge arm voltage reference value, and the specific formula is as follows:
Step S5.4.2: the state of charge SOC i (t) of the battery pack is estimated according to the ampere-hour integration method, and the specific formula is as follows:
Wherein SOC i (0) represents the initial state of charge of the battery, and Q N represents the rated capacity of the battery pack;
step S5.4.3: the weighted energy state p xyi of each energy storage sub-module is calculated, and the specific formula is as follows
pxyi＝kuCxyi 2+(1-k)SOCi(t),0＜k＜1
Wherein k represents a weighting coefficient of the capacitor voltage, and u Cxyi represents the capacitor voltage of the ith energy storage sub-module of the xy bridge arm;
step S5.4.4: and sequencing the p xyi, and respectively controlling the input or the cutting of each energy storage submodule in each phase of bridge arm by adopting the nearest level approximation modulation.
The invention has the beneficial effects that:
1. the modular design is adopted, so that the integrated production and the redundancy expansion are easy, and the reliability is high;
2. The number of output levels is large, and the waveform quality of voltage and current is high;
3. the flexible closing ring between the feed lines is realized, and the closing impact current is reduced;
4. And compensating power load fluctuation, and seamlessly switching a grid-connected mode and a grid-disconnected mode to provide voltage and frequency support.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and should not be construed as limiting the invention in any way, in which:
FIG. 1 is a topological structure diagram of a web-formed flexible interconnect device in accordance with an embodiment of the present invention;
FIG. 2 is a first phase unit network control block diagram in accordance with an embodiment of the present invention;
FIG. 3 is a diagram of a coordinate transformation in accordance with an embodiment of the present invention;
FIG. 4 is a graph of amplitude-frequency curve of a power control filtering link in an embodiment of the present invention;
fig. 5 is a block diagram illustrating current control of an energy storage battery according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The specific embodiment discloses a net-structured flexible interconnection device and a control method thereof, as shown in fig. 1, the net-structured flexible interconnection device comprises three phase units u, v and w, and each phase unit comprises three parallel bridge arms; the positive end of the first bridge arm of each phase unit is connected with an input first phase power supply a through a bridge arm inductor, the positive end of the second bridge arm of each phase unit is connected with an input second phase power supply b through a bridge arm inductor, and the positive end of the third bridge arm of each phase unit is connected with an input third phase power supply c through a bridge arm inductor; the negative ends of the three bridge arms in each phase unit are connected as the outlet end of the phase unit and are connected in series with a reactor L o, and the reactor L o is respectively connected with the u, v and w phases of the three-phase power grid through a mechanical switch S u、 Sv、Sw; each bridge arm of the three phase units is formed by connecting n identical energy storage sub-modules in series, and the voltage of feeder lines at two sides is 10kV for example, wherein n is 20; each energy storage sub-module comprises a full-bridge circuit and battery energy storage systems connected in parallel at two ends of a capacitor, wherein the full-bridge circuit consists of four switching tubes (S 1、S2、S3、S4) and a direct-current capacitor (C 1), and the rated value u dc of the capacitor voltage of the sub-module is 1kV; the battery energy storage system consists of a battery module, an energy storage inductor (L m) and two switching tubes (S 5、S6). Aiming at the topology, the network-structured control strategy determines a reference value of bridge arm voltage according to control of input and output sides and bridge arm capacitance voltage control; determining a power reference value of the energy storage battery according to the power difference value of the input side and the output side, and independently controlling the power reference value; and respectively controlling the input or the cutting of each sub-module in each phase of bridge arm by adopting the nearest level approximation modulation according to the capacitance voltage value of the full-bridge sub-module and the charge state of the battery.
The three phase units have similarity in structure, the input side control is the same, and the input side control aim of each phase unit is to enable the capacitance voltage average value of the submodule in each phase unit to be stabilized at a given value. Taking u-phase as an example, the input side voltage control method will be specifically described with reference to fig. 2 (a):
And collecting capacitance voltages u Cxui of each bridge arm submodule of the u phase, wherein x (x=a, b and c) represents that the bridge arm is connected with the input x phase. The sum of the capacitance voltages of all the sub-modules of the U phase is calculated, and the direct current component is obtained through a low-pass filter with the cutoff frequency of 1kHz and is used as a feedback signal Sigma U Cu of a closed-loop controller:
∑UCu＝∑UCau+ΣUCbu+ΣUCcu (1)
In the formula, Σu Cau,ΣUCbu and Σu Ccu represent direct current components of au, bu, and cu arm capacitor voltages, respectively.
The difference value between the given value 3nu dc of the sum of the capacitance voltages of all the sub-modules in the U phase and the sigma U Cu is used as an input signal of a closed-loop controller, wherein the closed-loop controller is a proportional-integral controller, and the generated signal is an active current reference value i dui * of the input U phase. Calculating a reference value i aui *、ibui *、icui * of the input current of each bridge arm of the u phase under a three-phase static coordinate system according to the formula (2):
Where i denotes the input-side bus voltage phase angle, which can be obtained by the phase-locked loop in fig. 3, i qui * denotes the reactive current reference value of the input u phase, and i qui * =0 is usually set, or other values can be set according to the control target.
The output side realizes synchronous function and parallel/off-grid seamless switching through a network construction control strategy, and realizes flexible loop closing of the feeder line based on voltage presynchronization control, so that closing impact current is reduced; and the support to the frequency is provided based on the power automatic regulation control, so that the voltage recovery capability of the power distribution network after faults is improved. The following describes a net-structured control method with reference to fig. 2 (b):
Before the grid connection and the loop connection, three-phase voltages u u1、uv1 and u w1 at a feeder line of the quasi-grid connection and the loop connection are collected, and the component of the voltage under a two-phase synchronous rotation coordinate system is calculated according to a formula (3) and is used as a voltage given value u gd1、ugq1 of an output side grid connection point:
Wherein, theta o is the output angle of the feeder voltage phase-locked loop.
Collecting three-phase voltages u u、uv and u w of the grid-connected point of the output end, and calculating the components of the three-phase voltages under a two-phase synchronous coordinate system according to a formula (4) to serve as feedback values u gd、ugq of voltage closed-loop control:
As shown in fig. 2 (b), the voltage of the grid-connected point is closed-loop controlled by a proportional-integral controller, and an output signal generated by the closed-loop controller is an output side active current reference value i do * and a reactive current reference value i qo *. The three bridge arms in each phase unit are symmetrical in structure, so that the output current of each phase is equally divided among the three bridge arms in each phase, and the reference value i uo *、ivo *、iwo * of the output current of each phase unit bridge arm is calculated according to the formula (5):
In order to ensure safe and stable operation of the system, the capacitance voltage of the submodule of each bridge arm unit needs to be maintained near a given value, and the balance of the average capacitance voltage of the bridge arms is realized through closed-loop control of the capacitance voltage. Taking each bridge arm of u phase as an example, the capacitor voltage balance control will be specifically described with reference to fig. 2 (c):
calculating the average value of the capacitance voltage and the direct current component of each bridge arm submodule of the u phase as the feedback value of the capacitance voltage control of each bridge arm in the phase
The dc components Σu Cau、ΣUCbu、∑UCcu of the sum of the au, bu, cu arm capacitor voltages are already obtained in the aforementioned input side control. And (3) performing closed-loop control on the difference value between the direct current component and the average value of the sum of the capacitance voltages of each bridge arm by using a proportional-integral controller:
The outputs Δp aus、Δpbus and Δp cus of the closed loop controller represent the power references that au, bu, cu legs need to absorb or emit, respectively. The distribution of active power among the bridge arms is adjusted by constructing a circulation according to the formula (8), so that the average value of capacitance voltage of each bridge arm is the same:
in the formula, i ciruau *、icirubu *、icirucu * represents the loop reference values of au, bu and cu arms, and o t represents the phase of the u-phase output side voltage.
As can be seen from fig. 1, each bridge arm current is composed of three parts of input current, output current and circulating current, so the reference value i xu * of each bridge arm current of u phase is:
And collecting the inductance current of each bridge arm of the u phase as a feedback value i xu of closed loop control. Taking the difference between i xu * and i xu as the input signal of the proportional-resonant controller, adding a voltage feedforward term after the output of the closed-loop controller, and according to fig. 2 (d), the reference value of each bridge arm voltage of u phases is:
wherein G di(s) represents the transfer function of the proportional resonant controller, and is specifically shown in formula (11):
Where k p and k pm represent the ratio and the resonance coefficient of the controller, respectively, and ω i、ωo represents the angular frequency of the input and output sides, respectively, where ω i＝o =314 rad/s.
Before closing the ring, the battery system in the sub-module is in a blocking state, and after the reference value of the voltage of each bridge arm is obtained, the input and the cutting of the sub-module of each bridge arm are controlled according to the conventional nearest level approximation modulation. When the output side voltage u gd＝ugd1、ugq＝ugq1 is equal to the voltage amplitude phase of the feeder line to be connected, the mechanical switch S u、Sv、Sw is controlled to be closed, and flexible loop closing between the feeder lines is achieved.
After closing the loop, a primary power automatic regulation control loop is added in front of the output side voltage loop, as shown in fig. 2 (b). Collecting three-phase currents i u、iv and i w of grid-connected points at an output end, and calculating a component i gd、igq of the current under a two-phase synchronous rotation coordinate system according to a formula (12):
Wherein, θ * is the output angle of the power outer loop control.
Active power P g and reactive power Q g are calculated according to the grid-connected point voltage and current and are used as feedback values of closed loop control, and a calculation formula is as follows:
Automatically adjusting the power according to the formula (14), outputting a voltage vector amplitude reference value V * and a phase reference value theta *, wherein the phase is a synchronous signal:
Wherein, P * and Q * respectively represent an active power given value and a reactive power given value of an output side; m p and n q are active-frequency and reactive-voltage control correction coefficients, respectively, where m p＝50,nq =28; a and b are filter coefficients, where a=2.533 e-8, b=9.947e-5, the cut-off frequency of the filter element is 1000Hz, and the influence of the voltage and current higher harmonics on the frequency control can be reduced by the low-pass filter element in the formula (14), and the amplitude-frequency characteristic curve is shown in fig. 4.θ * is the coordinate transformation angle used for inner loop control, and initially θ *＝θo.
When the power supply in the feeder line area connected with the output side fails, the output side is converted from a grid-connected mode into a grid-off mode, the mode of the formula (14) is rewritten into the mode of the formula (15) to realize seamless switching of grid-off, voltage is established through the flexible interconnection device, and the voltage recovery capability after fault elimination is improved:
Where U * denotes the voltage vector magnitude set point, ω o * denotes the output angular frequency set point, where U * = 8.165kV (phase voltage magnitude), ω o * = 314rad/s.
Further, reference values u gd and u gq of the output-side grid-connected point voltage in the two-phase rotation coordinate system:
ugd *＝V*,ugq *＝0 (16)
The power control after loop closing can be realized by making the output side voltage set value u gd1＝ugd *,ugq1＝ugq * and the coordinate transformation angle theta o＝θ*.
After the ring closing is completed, the battery energy storage system is put into operation and is responsible for compensating the difference value between the power of the input side and the power of the output side, and the battery energy storage system has two working modes of charging and discharging. The battery energy storage system adopts a constant-power charge-discharge strategy, so that the power of the system is kept balanced, and the stability of voltage and frequency is ensured. The battery current control method of the energy storage sub-module is shown in fig. 5, and the specific implementation manner is as follows:
calculating a reference value P e * of the output power of each battery energy storage system according to the formula (17):
Wherein P i represents the total power of the input sides of the three phase units, which can be calculated according to formula (18):
Pi＝uaia+ubib+ucic (18)
Defining the voltage across the battery pack as U E, where U E =800V, taking the current reference i e * for each battery energy storage system calculated according to the following equation:
The energy management of the storage battery pack is realized by controlling the bidirectional DC/DC converter, and independent PWM control is adopted for the switching tube S 5、S6 in the battery energy storage system, so that the switching tube S 5、S6 is charged and discharged as required to maintain the energy balance of the system. The working modes of the storage battery pack are different according to the difference of positive and negative of P e *. The current on the inductance L m of each battery energy storage system is collected and used as a feedback signal i ei of the closed-loop controller.
When P e * <0, the battery absorbs energy, and the bidirectional DC/DC converter works in Buck mode, i charge_ref＝ie *. As shown in fig. 5 (a), the difference between i charge_ref and i ei is used as an input signal of a closed loop controller, wherein the closed loop controller is a proportional-integral controller, the output signal is a control signal of a switching tube S 5 of the bidirectional DC/DC converter, and the switching tube S 6 is always turned off. U E/udc in fig. 5 (a) represents the steady-state duty cycle.
When P e * >0, the battery releases energy and the bi-directional DC/DC converter operates in Boost mode, i discharge_ref＝ie *. As shown in fig. 5 (b), the difference between i ei and i discharge_ref is used as an input signal of a closed loop controller, wherein the closed loop controller is a proportional-integral controller, the output signal is a control signal of a switching tube S 6 of the bidirectional DC/DC converter, and the switching tube S 5 is always turned off.
And each bridge arm needs to be input with a certain number of sub-modules so that the low-frequency component of the output voltage is the desired voltage, and the input or the cutting of each sub-module in each phase of bridge arm is respectively controlled by adopting a nearest level approximation modulation algorithm. Taking au bridge arms as an example, firstly, determining the number n au of submodules required to be put into according to a bridge arm voltage reference value:
where round represents a rounding function.
Then, the state of charge SOC i (t) of the storage battery is estimated according to an ampere-hour integration method:
where SOC i (0) represents the initial state of charge of the battery and Q N represents the rated capacity of the battery pack.
Then, calculating the weighted energy state p aui of each energy storage sub-module of the au bridge arm:
paui＝kuCaui 2+(1-k)SOCi(t),0＜k＜1 (22)
Where k represents a weighting coefficient of the capacitance voltage, and u Caui represents the capacitance voltage of the i-th sub-module of the au bridge arm.
Finally, sequencing p aui, and when the sub-modules are discharged, putting n au sub-modules according to the sequence of p aui from large to small so as to keep the energy states of the sub-modules consistent; when the sub-modules are charged, n au sub-modules are put into the order from small to large according to p aui.
Although embodiments of the present invention have been described in connection with the accompanying drawings, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, and such modifications and variations are within the scope of the invention as defined by the appended claims.
Claims (6)
1. A web-formed flexible interconnect device, comprising: three phase units, each of which comprises three bridge arms; the input sides of the three phase units are input with the same three-phase power supply, the positive end of a first bridge arm of each phase unit is connected with a first power supply in the three-phase power supply through a bridge arm inductor in the bridge arm, the positive end of a second bridge arm of each phase unit is connected with a second power supply in the three-phase power supply through a bridge arm inductor in the bridge arm, and the positive end of a third bridge arm of each phase unit is connected with a third power supply in the three-phase power supply through a bridge arm inductor in the bridge arm; the negative ends of the three bridge arms of the first phase unit are connected to serve as the outgoing line end of the first phase unit, and a reactor and a first mechanical switch are connected in series between the outgoing line end of the first phase unit and the first phase of the power grid; the negative ends of the three bridge arms of the second phase unit are connected to serve as outlet ends of the phase unit, and a reactor and a second mechanical switch are connected in series between the outlet ends of the second phase unit and the second phase of the power grid; the negative ends of the three bridge arms of the third phase unit are connected to be used as the outlet end of the phase unit, a reactor and a third mechanical switch are connected in series between the outlet end of the third phase unit and the third phase of the power grid,
Wherein, the three bridge arms of the phase unit all include: a plurality of energy storage sub-modules connected in series; the energy storage submodule comprises: the full-bridge circuit and connect in parallel the battery energy storage unit at electric capacity both ends in the full-bridge circuit, the full-bridge circuit includes: full-control type switching tube S 1, full-control type switching tube S 2, full-control type switching tube S 3, A full-control switch tube S 4 and a direct-current capacitor C 1; The battery energy storage unit comprises a battery pack U E, an energy storage inductor L m, a full-control switching tube S 5 and a full-control switching tube S 6; The fully-controlled switching tube S 1 and the fully-controlled switching tube S 3 are connected in series; the fully-controlled switching tube S 2 and the fully-controlled switching tube S 3 are connected in series; The fully-controlled switching tube S 5 and the fully-controlled switching tube S 6 are connected in series; The fully-controlled switching tube S 1 and the fully-controlled switching tube S 3 which are connected in series, the fully-controlled switching tube S 2 and the fully-controlled switching tube S 4 which are connected in series, The fully-controlled switching tube S 5 and the fully-controlled switching tube S 6 which are connected in series are connected in parallel with each other through a direct-current capacitor C 1; The battery pack U E and the energy storage inductor L m are connected in series and then connected to two ends of the fully-controlled switching tube S 6 in parallel.
2. A control method of a web-formed flexible interconnection device, applicable to the web-formed flexible interconnection device as claimed in claim 1, comprising:
An input side voltage control method of a phase unit; the output side flexible loop closing control method of the three phase units comprises the following steps of; the capacitor voltage control method of the bridge arm unit; the output side parallel/off-grid seamless switching control method of the phase unit; the control method of the energy storage sub-module;
Before closing the loop, firstly executing an input side voltage control method of the phase unit simultaneously; the output side flexible loop closing control method of the three phase units comprises the following steps of; the capacitor voltage control method of the bridge arm unit; executing a seamless switching control method of the output side parallel/off-grid of the phase unit; the control method of the energy storage sub-module;
after closing the loop, executing an input side voltage control method of the phase unit; the capacitor voltage control method of the bridge arm unit; the output side parallel/off-grid seamless switching control method of the phase unit; the control method of the energy storage sub-module;
Specifically, the input side voltage control method of the phase unit comprises the following steps:
step S1.1: collecting capacitance voltage values u Cxyi of all bridge arms in the y-phase unit;
step S1.2: calculating the capacitance voltage sum of all bridge arms in the y-phase unit, and obtaining direct current components of the capacitance voltage sum through low-pass filtering to serve as a feedback signal Sigma U Cy of the closed-loop controller;
step S1.3: according to the difference value between the given value 3nu dc of the sum of the capacitance voltages of all bridge arms in the y-phase unit and the feedback signal sigma U Cy, an active current reference value i dyi * of the input y-phase is obtained;
Step S1.4: calculating an input side current reference value i ayi *、ibyi *、icyi * of each bridge arm of the y-phase unit according to the active current reference value i dyi *;
the output side flexible loop closing control method of the three phase units comprises the following steps:
Step S2.1: before grid connection and loop closing, when closed-loop control is obtained through a voltage presynchronization control process, an output side active current reference value i do * and an output side reactive current reference value i qo * generated by a closed-loop controller are obtained;
Step S2.2: according to the output side active current reference value i do * and the output side reactive current reference value i qo *; calculating the output current reference value i uo *、ivo *、iwo * of each phase unit bridge arm;
The capacitor voltage control method of the bridge arm unit comprises the following steps:
Step S3.1: calculating the average value of the capacitance voltage sum direct current component of each bridge arm of the y-phase unit
Wherein Σu Cay,∑UCby and Σu Ccy represent the direct current component of the sum of the capacitance voltages of ay, by, cy bridge arms, respectively;
Step S3.2: performing closed-loop control on the difference value between the direct current component of the capacitor voltage sum of each bridge arm and the average value of the direct current component of the capacitor voltage sum of each bridge arm of the y-phase unit by using a proportional-integral controller;
Wherein Δp ays、Δpbys、Δpcys represents the power reference values required to be absorbed or emitted by the ay, by and cy bridge arms respectively;
Step S3.3: the distribution of active power among bridge arms is adjusted to make the average value of capacitance voltage of each bridge arm identical, and the distribution mode of the active power is as follows:
Wherein i ciryay *、iciryby *、icirycy * represents the loop reference values of ay, by and cy bridge arms respectively, θ y represents the phase of the y-phase output side voltage, and u gd represents the d-axis component of the output side voltage;
Step S3.4: the specific process of calculating the voltage reference value u ay *、uby *、ucy * of each bridge arm of the y-phase unit is as follows from step S3.4.1 to step S3.4.3:
Step S3.4.1: collecting inductance current in each bridge arm as a feedback value i xy of closed-loop control;
Step S3.4.2: the reference value i xy * of each bridge arm current of the y-phase unit is calculated, and the specific formula is as follows:
Step S3.4.3: taking the difference value of i xy * and i xy as an input signal of a proportional-resonant controller, adding a voltage feedforward term after the output of a closed-loop controller, wherein the reference value of each bridge arm voltage of a y-phase unit is as follows:
step S3.5: according to the voltage reference value of each bridge arm, the input or the cutting of the energy storage submodule in each phase of bridge arm is respectively controlled by adopting the nearest level approximation modulation;
step S3.6: when u gd＝ugd1,ugq＝ugq1 is reached, the mechanical switch connected with the output side of each phase is controlled to be closed, and the feeder line loop closing is completed;
the method for controlling the seamless switching of the output side parallel/off-grid of the phase unit comprises the following steps of;
step S4.1: after the grid connection and the loop closing, supporting the frequency and the voltage of the distribution network through automatic power regulation and control at an output side;
Step S4.2: repeating the step S2.1 and the capacitor voltage control method of the bridge arm unit;
The control method of the energy storage sub-module comprises the following steps:
Step S5.1: the reference value P e * of the output power of each battery energy storage unit is calculated, and the specific formula is as follows:
wherein P i represents the total power of the input sides of the three phase units;
Step S5.2: the current reference value i e * of each battery energy storage unit is calculated, and the specific formula is as follows:
Wherein U E represents the voltages at two ends of the storage battery pack;
Step S5.3: according to the current on the inductance in each battery energy storage unit and the reference value P e *, the battery energy storage units are independently controlled
Step S5.4: and respectively controlling the input or the cutting of each energy storage sub-module in each phase of bridge arm by adopting a nearest level approximation modulation algorithm.
3. The method for controlling the network-structured flexible interconnection device according to claim 2, wherein the specific process of step 2.1 is as follows:
Step S2.1.1: collecting three-phase voltages u u1、uv1 and u w1 at the quasi-grid-connected loop feeder line;
Step S2.1.2: the component of the voltage in S2.1.1 under the two-phase synchronous rotation coordinate system is calculated and used as the voltage given value u gd1、ugq1 of the output side grid-connected point, and the specific formula is as follows:
wherein, theta o is the output angle of the feeder voltage phase-locked loop;
Step S2.1.3: collecting three-phase voltages u u、uv and u w of grid-connected points at the output end of the mechanical switch;
Step S2.1.4: the component of the voltage in S2.1.3 under the two-phase synchronous rotation coordinate system is calculated and used as a feedback value u gd、ugq of voltage closed-loop control, and the specific formula is as follows:
Step S2.1.5: and performing closed-loop control on grid-connected point voltage by using a proportional-integral controller, wherein output signals generated by the closed-loop controller are an active current reference value i do * and a reactive current reference value i qo *.
4. The method for controlling a network-structured flexible interconnection device according to claim 2, wherein the specific process of step S4.1 is as follows:
Step S4.1.1: collecting three-phase voltages u u、uv and u w and three-phase currents i u、iv and i w of a grid-connected point at the output end of a mechanical switch, and converting the three-phase voltages and the three-phase currents into a two-phase synchronous rotation coordinate system through the following formula:
Wherein, theta * is the output angle of the power outer loop control;
Step S4.1.2: calculating active power P g and reactive power Q g according to the grid-connected point voltage and current, and using the active power P g and the reactive power Q g as feedback values of closed-loop control;
Step S4.1.3: the output side voltage vector amplitude reference value V * and the phase reference value theta * are calculated according to the following specific formulas:
Wherein, P * and Q * respectively represent an active power given value and a reactive power given value, m p and n q respectively represent active-frequency and reactive-voltage control correction coefficients, a and b are filter coefficients, and theta * is a coordinate transformation angle used for inner loop control;
Step S4.1.4: reference values u gd * and u gq * of the output-side grid-connected point voltage in a two-phase rotation coordinate system:
ugd *＝V*,ugq *＝0。
5. The method for controlling a network-structured flexible interconnection device according to claim 2, wherein the specific process of step S5.3 is as follows:
Step S5.3.1: collecting current on the inductance of each battery energy storage unit as a feedback signal i ei of the closed-loop controller;
Step S5.3.2: when P e * is less than 0, taking the difference value of i e * and i ei as an input signal of a closed-loop controller, wherein the closed-loop controller is a proportional-integral controller, and generating a control signal of a switching tube S 5 of the bidirectional DC/DC converter;
Step S5.3.3: when P e * >0, the difference between i ei and i e * is used as the input signal of a closed-loop controller, wherein the closed-loop controller is a proportional-integral controller, and a control signal of a switching tube S 6 of the bidirectional DC/DC converter is generated.
6. The method for controlling a network-structured flexible interconnection device according to claim 2 or 5, wherein the specific process of step S5.4 is as follows:
step S5.4.1: the number n xy of energy storage submodules required to be put into each bridge arm is determined according to the bridge arm voltage reference value, and the specific formula is as follows:
Step S5.4.2: the state of charge SOC i (t) of the battery pack is estimated according to the ampere-hour integration method, and the specific formula is as follows:
Wherein SOC i (0) represents the initial state of charge of the battery, and Q N represents the rated capacity of the battery pack;
step S5.4.3: the weighted energy state p xyi of each energy storage sub-module is calculated, and the specific formula is as follows
pxyi＝kuCxyi 2+(1-k)SOCi(t),0＜k＜1
Wherein k represents a weighting coefficient of the capacitor voltage, and u Cxyi represents the capacitor voltage of the ith energy storage sub-module of the xy bridge arm;
step S5.4.4: and sequencing the p xyi, and respectively controlling the input or the cutting of each energy storage submodule in each phase of bridge arm by adopting the nearest level approximation modulation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210189191.5A CN114530885B (en) | 2022-02-28 | 2022-02-28 | Net-structured flexible interconnection device and control method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210189191.5A CN114530885B (en) | 2022-02-28 | 2022-02-28 | Net-structured flexible interconnection device and control method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114530885A CN114530885A (en) | 2022-05-24 |
| CN114530885B true CN114530885B (en) | 2024-07-26 |
Family
ID=81624592
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210189191.5A Active CN114530885B (en) | 2022-02-28 | 2022-02-28 | Net-structured flexible interconnection device and control method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114530885B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102545644A (en) * | 2012-03-14 | 2012-07-04 | 山东大学 | Matrix AC (alternating current)-AC high voltage frequency converter topology structure |
| CN113285620A (en) * | 2021-06-25 | 2021-08-20 | 上海交通大学 | Multi-alternating-current port modular multi-level converter and control method thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN209313433U (en) * | 2018-06-19 | 2019-08-27 | 全球能源互联网研究院有限公司 | A kind of transmission system |
| CN113452066B (en) * | 2021-05-28 | 2022-12-02 | 北方工业大学 | Optimization method of flexible interconnection device control strategy |
| CN114070115B (en) * | 2021-11-24 | 2024-09-03 | 上海交通大学 | Multi-AC-port high-voltage direct-hanging energy storage power conversion system and control method thereof |
-
2022
- 2022-02-28 CN CN202210189191.5A patent/CN114530885B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102545644A (en) * | 2012-03-14 | 2012-07-04 | 山东大学 | Matrix AC (alternating current)-AC high voltage frequency converter topology structure |
| CN113285620A (en) * | 2021-06-25 | 2021-08-20 | 上海交通大学 | Multi-alternating-current port modular multi-level converter and control method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114530885A (en) | 2022-05-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110380626B (en) | High-power-density single-phase cascade H-bridge rectifier, control method and control system | |
| CN113285620A (en) | Multi-alternating-current port modular multi-level converter and control method thereof | |
| CN110022071B (en) | Hybrid energy storage type direct current transformer and control method thereof | |
| CN115085241B (en) | Power conversion method of alternating current direct grid-connected battery energy storage system | |
| Pardhi et al. | High gain non isolated DC converter employed in single-phase grid-tied solar photovoltaic supply system | |
| CN115663864A (en) | High-voltage direct-current cascade energy storage system and control protection method thereof | |
| Tolbert et al. | Multilevel power converters | |
| US11811310B2 (en) | Power conversion system and control method | |
| Liao et al. | Unbalanced voltage/power control in bipolar DC distribution grids using power flow controller | |
| CN114530885B (en) | Net-structured flexible interconnection device and control method thereof | |
| Ahmed et al. | Modified half-bridge modular multilevel converter for HVDC systems with DC fault ride-through capability | |
| CN110690723B (en) | Control method of energy storage type modular multilevel converter in offshore wind power system | |
| Torres-Olguin et al. | Grid Integration of offshore wind farms using a Hybrid HVDC composed by an MMC with an LCC-based transmission system | |
| Neira et al. | A novel three-port NPC converter for grid-tied photovoltaic systems with integrated battery energy storage | |
| Mishra et al. | Novel voltage balancing techniques for modular multilevel PV inverters | |
| Jeyapradha et al. | Investigations on service extensions of solid state transformer | |
| Missanda et al. | Nonlinear control of three-phase three-level four-wire NPC converter | |
| Zhang | Constant frequency operated autonomous AC microgrid with different MPPT methods applied to PV panels and with converting circuit for powering unbalanced loads | |
| Guo et al. | Modeling and simulation of a power conditioning system for the hybrid fuel-cell/turbine power plant | |
| Hao et al. | Multi Busbar Sub-module Modular Multilevel STATCOM with Partially Rated Energy Storage Configured in Sub-stacks | |
| Chandaka et al. | A 5L Switched-Capacitor Based H7 Inverter Topology with Reduced Leakage Current | |
| Pi et al. | Three-phase Four-wire Photovoltaic System with Power Quality Condition Function | |
| Butt et al. | Single Phase Grid Tied PV System Modeling and Control with Low Voltage Ride Through Capability | |
| Li et al. | Parallel Virtual Impedance Based Fluctuation Power Delivery Strategy For MMC Based SST | |
| Townsend et al. | Capacitance minimisation & alleviation of per-phase power imbalances in cascaded PV converters |
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 | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20220818 Address after: 212300 No. 218, Yuquan Road, Danyang City, Zhenjiang City, Jiangsu Province Applicant after: Danyang power supply branch of State Grid Jiangsu Electric Power Co.,Ltd. Applicant after: STATE GRID JIANGSU ELECTRIC POWER Co.,Ltd. ZHENJIANG POWER SUPPLY BRANCH Applicant after: State Grid Jiangsu Electric Power Co.,Ltd. innovation and Innovation Center Applicant after: STATE GRID JIANGSU ELECTRIC POWER Co.,Ltd. Address before: 218 Yuquan Road, Danyang Development Zone, Zhenjiang City, Jiangsu Province Applicant before: Danyang power supply branch of State Grid Jiangsu Electric Power Co.,Ltd. Applicant before: STATE GRID JIANGSU ELECTRIC POWER Co.,Ltd. ZHENJIANG POWER SUPPLY BRANCH |
|
| TA01 | Transfer of patent application right | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |