CN106452133B - A kind of core current transformer and its control method constructing bipolarity direct-current micro-grid - Google Patents

A kind of core current transformer and its control method constructing bipolarity direct-current micro-grid Download PDF

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Publication number
CN106452133B
CN106452133B CN201610853462.7A CN201610853462A CN106452133B CN 106452133 B CN106452133 B CN 106452133B CN 201610853462 A CN201610853462 A CN 201610853462A CN 106452133 B CN106452133 B CN 106452133B
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voltage
current
bridge
module
isolation level
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CN106452133A (en
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张国澎
胡治国
杨明
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Henan University of Technology
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Henan University of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a kind of core current transformers for constructing bipolarity direct-current micro-grid, the interface current transformer as high-voltage alternating distribution and low voltage dipole direct-current micro-grid.It is constituted including input filter, rectification stage and isolation level three parts；Modularized design.Rectification stage uses H bridge cascade structure, and modular isolation level uses the improved active full bridge structure in three ports, and output bus correspondence is in parallel, to realize the matching of current transformer two sides network voltage, power.The invention also discloses the control methods of above-mentioned current transformer: rectification stage uses the vector controlled of injected zero-sequence voltage, and isolation level uses the decoupling phase shifting control of voltage, current double closed-loop.The invention enables energy can free exchange between two power grids and between two buses of bipolarity direct-current micro-grid.Realize that the function integration of the Industrial Frequency Transformer, rectifier, balance of voltage device of conventional construction bipolarity direct-current micro-grid improves the power density of building equipment to optimize the building mode of bipolarity direct-current micro-grid.

Description

A kind of core current transformer and its control method constructing bipolarity direct-current micro-grid
Technical field
The present invention relates to electronic power convertor technical fields, more particularly to a kind of connecing for building bipolarity direct-current micro-grid Mouth current transformer.
Background technique
The direct-current grid of bipolarity power supply, in the new energy such as photovoltaic, fuel cell access efficiency, data center and computer room Power supply efficiency, the flexibility of load and the access of micro- source, all various aspects such as reliability, system earth of power supply all show it is congenital Advantage.But compared with other types direct-current micro-grid, there are particularity for its building, are embodied in the construction and middle line of microgrid middle line The equilibrium problem of voltage.Since in bipolarity direct-current micro-grid, load, there are different access ways in micro- source, bipolar extension will cause The unbalanced of power is carried, thus causes neutral voltage uneven.It is another negative if a load is articulated between microgrid positive and negative anodes bus Load is articulated between microgrid positive electrode bus and middle line.
The building of traditional bipolarity direct-current micro-grid, generallys use two level or three-level rectifier forms DC bus；It will DC bus is incorporated to after the series connection of capacitor group again, the concatenated midpoint of capacitor draws middle line, ultimately forms DC bus bipolarity Power supply；Such construction method usually also needs the power for solving bipolar carry using dedicated voltage equalizer is unbalanced to ask Topic；Using Industrial Frequency Transformer realize bipolarity direct-current micro-grid with exchange distribution be isolated and the matching problem of voltage, power.By This is as it can be seen that the constructing plan of current bipolarity direct-current micro-grid has following deficiency: (1) two level or three-level rectifier do not have The balanced capacity or balanced capacity of standby neutral voltage are weaker；(2) need to be arranged independent neutral voltage balancer；(3) power frequency becomes Depressor land occupation is larger, quality is heavy, loss is big and noise is big, this, which has become, realizes high power density and high efficiency power conversion One major obstacle of system.
Summary of the invention
Problem to be solved:
In order to overcome the difficulty of above-mentioned existing building bipolarity direct-current micro-grid with it is insufficient, the present invention proposes a kind of to become power frequency The novel converter topology and control method that depressor, rectifier, balance of voltage device combine, as middle pressure exchange distribution with The interconnecting interface core current transformer of low voltage dipole direct-current micro-grid improves to optimize the building mode of bipolarity direct-current micro-grid The power density of equipment.
Technical solution:
It is a kind of construct bipolarity direct-current micro-grid core current transformer, it is characterised in that: 1. its topology include input filter, Rectification stage and isolation level three parts structure；2. modularized design；
The input filter uses inductance mode filter.Input filter input terminal exchanges distribution with middle pressure and is connected, defeated Outlet exchanges side with rectification stage and is connected；
Rectification stage exchange side is connected with input filter output end；The rectification stage DC side and isolation level primary side It is connected；The isolation level secondary side is connected with low voltage dipole direct-current micro-grid；
The rectification stage includes rectifier and output filter, and the every phase of rectifier is all made of N number of H bridge cascade structure, N For natural number.The output filter uses capacitor mode filter, is connected in parallel on the DC side of each H bridge；
The isolation level is made of 3N mutually isostructural unit, and N is identical as rectification stage H bridge number.Each unit includes Primary structure, high-frequency isolation transformer, secondary structure three parts composition, the isolation level unit are once three with secondary structure Three port organizations that H bridge topology is formed；
The isolation level primary side refers to the primary structure of all isolation level units；What the secondary side of the isolation level referred to It is the secondary structure of all isolation level units；
The H bridge DC side of the isolation level unit primary structure and the DC side parallel of rectification stage H bridge, exchange side and high frequency Isolating transformer primary side is connected；
The H bridge 1 of the isolation level unit secondary structure exchanges side and is connected with high-frequency isolation transformer vice-side winding 1, H bridge 1 Just extremely the anode of bipolarity DC bus, cathode are the middle line of bipolarity DC bus to DC side；The isolation level unit two The H bridge 2 of secondary structure exchanges side and is connected with high-frequency isolation transformer vice-side winding 2, and just extremely bipolarity direct current is female for 2 DC side of H bridge The middle line of line, cathode are the cathode of bipolarity DC bus.The H bridge 1 and 2 DC side of H bridge of isolation level unit secondary structure are simultaneously Join DC voltage-stabilizing capacitor, to form bipolarity DC bus structure；
The high-frequency isolation transformer is single primary side winding, two-pack side winding construction；
The modularized design refers to and constitutes a module by a unit of a H bridge of rectification stage and isolation level.Mould The exchange side of block is the exchange side of rectification stage H bridge, and the DC side of module is that the bipolarity that isolation level unit secondary structure is formed is straight Flow anode, middle line and the cathode of bus；
N number of module exchange side series connection, N is natural number, constitutes exchange side phase structure, and three phase structures are connected into star, To constitute three-phase structure, the exchange side of current transformer is formed；The DC side of all modules corresponds to pole according to anode, middle line, cathode Property be connected in parallel, formed the bipolar bus structure of current transformer DC side.To ultimately form core unsteady flow proposed by the present invention Device structure；
The exchange side of the core current transformer exchanges distribution with middle pressure and is connected, the DC side and low pressure of the core current transformer Bipolarity direct-current micro-grid is connected；
Semiconductor switch in the rectification stage and isolation level circuit is all made of the wholly-controled devices such as IGBT or MOSFET.
Compared with prior art, a kind of core current transformer constructing bipolarity direct-current micro-grid provided by the invention has following Beneficial technical effect:
(1) the new topological realization rectifier and the balance of voltage of Industrial Frequency Transformer, two level or three Level Full Bridges topology The function of device is integrated, so that the number of devices of building bipolarity direct-current micro-grid is reduced, system building is simplified；
(2) Industrial Frequency Transformer being substituted using high frequency transformer, realization exchange distribution is isolated with bipolarity direct-current micro-grid, Transformer high frequency reduces the equipment volume of building bipolarity direct-current micro-grid simultaneously；
(3) the isolation level module of new topology uses three port organizations, logical providing energy exchange for current transformer two sides power grid While road, the access of energy exchange is also provided between the two poles of the earth bus in direct-current micro-grid；
(4) modularized design is convenient for system maintenance and extension.
Detailed description of the invention
Fig. 1 is current transformer three-phase topological diagram proposed by the present invention.
Fig. 2 is converter module topological diagram proposed by the present invention.
Fig. 3 is module isolation level topological diagram.
Fig. 4 is H bridge topological diagram.
Fig. 5 is module isolation level high frequency transformer original secondary voltage waveform diagram.
Fig. 6 is current transformer rectification stage control block diagram of the present invention.
Fig. 7 is module isolation level control block diagram.
Specific embodiment
A kind of current transformer of the bright offer of this law, for constructing bipolarity direct-current micro-grid, as high-voltage alternating distribution and low pressure The interface current transformer of bipolarity direct-current micro-grid.Using the rectification level structure of cascaded H-bridges, the high pressure of matching exchange distribution；Using 3N The high-frequency isolation grade of a three port organization realizes the isolation of current transformer two sides power grid；By the 3N of isolation level three port secondary structures Corresponding output is in parallel, and realizes the building of bipolarity direct-current micro-grid and voltage, the power match of bipolarity direct-current micro-grid.Under In conjunction with attached drawing and concrete mode, present invention will be explained in further detail in face.
Fig. 1 show the current transformer three-phase topology of the bright proposition of this law, comprising: input filter 2 and current transformer 3.Input filter The input side of wave device 2 is connected to middle pressure exchange distribution 1, and the outlet side of input filter 2 is connected to the input port of current transformer 3. The output end of current transformer 3 constitutes bipolarity direct-current micro-grid, is connected with bipolarity direct-current micro-grid 7.
Input filter 2 uses inductance mode filter, and three single-phase inductance can be used or use a three pole reactor, therefore There are three input port and three output ports for the tool of input filter 2.
Current transformer 3 includes three identical phase structures: A phase structure 4, B phase structure 5, C phase structure 6.Every phase input Port includes two input lines, and output port includes three output lines.The input line 8 of A phase structure 4 is defeated with input filter 2 Side corresponding ports are connected out, and the input line 9 of B phase structure 5 is connected with the outlet side corresponding ports of input filter 2, C phase structure 6 Input line 10 be connected with the outlet side corresponding ports of input filter 2.The input line 11 and B phase structure 5 of A phase structure 4 it is defeated The input line 13 for entering line 12 and C phase structure 6 links together.To constitute the star-star connection that current transformer 3 exchanges side.A phase is tied Structure 4, B phase structure 5, three output lines correspondence of C phase structure 6 are in parallel together, form bipolarity direct-current micro-grid positive electrode bus 14, bipolarity direct-current micro-grid middle line 15, bipolarity direct-current micro-grid negative electrode bus 16.
The phase structure of current transformer 3 is by the identical module composition of N number of structure, as shown in Figure 2.Module is by module rectification stage 17 It is formed with module isolation level 18.Module rectification stage 17 uses single-phase H bridge structure, DC side parallel filter capacitor 24.Module rectification Grade 17 exchanges side and other module composition cascaded H-bridges structures, the rectification stage as current transformer 3.
By taking a certain module in A phase structure 4 as an example, if the module is first module in A phase structure 4, module is handed over The input line 8 that side input line 19 is A phase structure 4 is flowed, which exchanges second module in side input line 20 and A phase structure 4 Side input line 19 is exchanged to be connected；If the module is the n-th module in A phase structure 4, which exchanges side input line 19 and A The exchange side input line 20 of the N-1 module in phase structure 4 is connected, the exchange side input line of n-th module in A phase structure 4 20 be the input line 11 of A phase structure 4；If the module is k-th of module in A phase structure 4, k is integer, value range [2, N-1], then the exchange side input line 19 of kth module is connected with the side input line 20 that exchanges of -1 module of kth in A phase structure 4, kth mould The exchange side input line 20 of block is connected with the side input line 19 that exchanges of+1 module of kth in A phase structure 4, and current transformer is consequently formed Exchange side structure.
It includes three output lines that module, which exports direct current side ports, is positive 21, middle line 22, cathode 23 respectively.In current transformer 3 The anode 21 of the output line of all modules, which is connected in parallel, constitutes bipolarity direct-current micro-grid positive electrode bus 14；Own in current transformer 3 The middle line 22 of the output line of module, which is connected in parallel, constitutes bipolarity direct-current micro-grid middle line 15；All modules is defeated in current transformer 3 The cathode 23 of outlet, which is connected in parallel, constitutes bipolarity direct-current micro-grid negative electrode bus 16.
18 structure of module isolation level is as shown in figure 3, by 18 primary structure 25 of module isolation level, high frequency transformer 26, module 18 secondary structure 27 of isolation level and output filter 30 form.18 primary structure 25 of module isolation level uses H bridge structure, input End is connected with 17 output end of module rectification stage, the primary side of 18 primary structure of module isolation level, 25 output end and high frequency transformer 26 around Group is connected；High frequency transformer 26 is three-winding transformer, a primary side winding, two vice-side windings.Module isolation level 18 2 Secondary structure 27 is made of H bridge 28 and H bridge 29.The exchange side of H bridge 28 is connected with 26 vice-side winding 1 of high frequency transformer, the friendship of H bridge 29 Stream side is connected with 26 vice-side winding 2 of high frequency transformer.28 DC side anode of H bridge is the anode of module output direct current side ports 21；The DC side cathode of H bridge 28 is connected with the DC side anode of H bridge 29, constitutes module middle line 22；The DC side cathode of H bridge 29 The as cathode 23 of module output direct current side ports.Output filter 30 is by being connected in parallel on the anode 21 of module output DC side in Capacitor between line 22, and be connected in parallel on capacitor between the cathode 23 and middle line 22 of module output DC side and constitute.
H bridge structure is as shown in figure 4, constitute S1, S2, S3, S4, full-control type power by four full-control type power semiconductors IGBT, which can be used, in semiconductor devices can also be used MOSFET, by taking IGBT as an example.The collector of S1 and S3 links together, S2 and S4 Emitter link together, constitute H bridge DC side；The emitter of S1 and the collector of S2 link together, the emitter of S3 It links together with the collector of S4, constitutes H bridge and exchange side.
Current transformer stable operation of the present invention and function realize that control needs to realize:
(1) the rectification stage unit power factor rectifier of current transformer completes the transformation of high-voltage alternating to direct current.Simultaneously, it is desirable that 24 voltage of parallel filtering capacitor of all 17 DC sides of module rectification stage is equal after rectification, and is equal to 17 direct current of module rectification stage The setting value of pressure, i.e.,U dc_ref , such as formula (1-1):
(1-1)
WhereinU dc_a_1...,U dc_a_NFor the 1st module ... of current transformer A phase, each 17 DC side of module rectification stage in Nth module Parallel filtering capacitor 24 voltage；WhereinU dc_b_1...,U dc_b_NFor the 1st module ... of current transformer B phase, each mould in Nth module The voltage of the parallel filtering capacitor 24 of 17 DC side of block rectification stage；WhereinU dc_c_1...,U dc_c_NFor the 1st mould of current transformer C phase Block ..., the voltage of the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth module.
The 1st module ... of A phase is defined, the voltage of the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth module The sum of beU dc_a_sum ；The 1st module ... of B phase, the electricity of the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth module Pressure the sum of beU dc_b_sum ；The 1st module ... of C phase, the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth module The sum of voltage isU dc_c_sum , relationship meets formula (1-2):
(1-2)
The control of current transformer rectification stage uses vector controlled, and control block diagram is as shown in fig. 6, control method is as follows:
The first step, in acquisition in pressure exchange distribution 1 A phase voltage angleθ
Three-phase voltage in pressure exchange distribution 1 in Sample ACu a 、u b 、u c , become by the coordinate that three phase static to two-phase rotates It changes, obtains the voltage power-less component under two-phase rotating coordinate systemu q , transformation for mula is such as shown in (1-3):
(1-3)
It is calculatedu q By PI controller, rate correction amount Δ is obtainedω,The correction amount is added with 100 π, is obtained Current angular velocityω s ,ω s (when the angle is greater than 2 π, it is allowed to be 0, to guarantee the angle obtained with 2 π modulus values after integral Information is in the range of 0 ~ 2 π), then by the angleθThe coordinate transform for feeding back to formula (1-3) calculates in angle used, shape At control closed loop.The angleθThe angle of A phase voltage in as current middle pressure exchange distribution 1.
Second step, the electric current of decoupling AC side of converter input
Sample the electric current of current transformer input line 8i as , input line 9 electric currenti bs , input line 10 electric currenti cs .Pass through three-phase Three-phase current, is become the watt current under rotating coordinate system by the static coordinate transform (3S/2R decoupling transformation) to two-phase rotationi d And reactive currenti q .Shown in transformation for mula such as formula (1-4), what the angle in formula was obtained using the first stepθValue,
(1-4)。
Third step, the electric current of control AC side of converter input
The 1st module ... of A, B, C three-phase is calculated, the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth module The sum of voltageU dc_a_sum 、U dc_b_sum 、U dc_c_sum Average valueU dc_ave_sum , N*U dc_ref It subtractsU dc_ave_sum It is controlled by PI After device, the given value of current transformer rectification stage input current active component is obtainedi d_ref .It willi d_ref Subtract the change obtained by second step It flows device and inputs watt currenti d , the active component of current transformer ac output voltage is obtained after PI controllerv d ；" 0 " is subtracted by The current transformer that two steps obtain inputs reactive currenti q , the reactive component of current transformer ac output voltage is obtained after PI controllerv q 。 The coordinate transform (3S/2R decouples inverse transformation) that three phase static is rotated to by two-phase, shown in transformation for mula such as formula (1-5).To Obtain the three-phase voltage modulating wave synthesized needed for AC side of converteru as 、u bs 、u cs
(1-5) 。
4th step, modulating wave injected zero-sequence voltage, the total voltage of each phase DC side of balancing curent transformer A, B, C
By N*U dc_ref The 1st module ... of A phase is subtracted, the parallel filtering electricity of each 17 DC side of module rectification stage in Nth module Hold 24 the sum of voltageU dc_a_sum , after PI controller, obtain A phase power compensation amountP ao；N*U dc_ref Subtract the 1st mould of B phase Block ..., the sum of the voltage of the parallel filtering capacitor 24 of each 17 DC side of module rectification stage in Nth moduleU dc_b_sum , controlled by PI After device processed, B phase power compensation amount is obtainedP bo.Utilize formula (1-6), formula (1-7) and formula (1-8):
(1-6)
(1-7)
(1-8)
The residual voltage amplitude that modulating wave needs to inject can be acquiredU 0And angleθ 0: thus the residual voltage injectedu 0 。 It willu 0 With former modulating waveu as 、u bs 、u cs It is separately summed the three-phase voltage modulating wave synthesized needed for obtaining current transformer rectification stage exchange side Correction waveformu as_c 、u bs_c 、u cs_c , current transformer rectification stage exchange side exports such voltage waveform, unit power can be realized Factor rectification, can also each phase DC side of balancing curent transformer A, B, C total voltage, realize formula (1-2).
5th step, the control of 17 dc-voltage balance of module rectification stage
In current transformer A phase of the present invention, by the voltage setting value of 17 parallel filtering capacitor 24 of module rectification stageU dc_ref Subtract The voltage of the parallel filtering capacitor 24 of k (k is integer, value range [1, N-1]) a module rectification stage 17u a _ dc_k , controlled by PI The coefficient ε that k-th of module rectification stage 17 exchanges side output current-modulation wave is obtained after device processed a_k , by the coefficient multiplied byu as_c / N is obtained The modulating wave of side output is exchanged to k-th of module rectification stage 17 of final current transformer A phaseu a_k_m ；It can be obtained finally using formula (1-9) Current transformer A phase n-th module rectification stage 17 exchanges the modulating wave of side outputu a_N_m .Later, by the way of SPWM, by modulating wave It is converted into the H bridge semiconductor devices of pwm signal control module rectification stage 17, wherein triangular carrier angle mutual deviation π/N of SPWM,
(1-9)
Similarly, the modulating wave that current transformer B phase exchanges side output with each module rectification stage 17 of C phase can be obtainedu b_x_m 、u c_x_m (x is integer, value range [1, N] here).It is equal that achievable 17 DC voltage of module rectification stage is controlled by this, and is equal to and is set Definite valueU dc_ref , that is, meet the control requirement of formula (1-1).
The control of current transformer rectification stage can be finally realized by above five steps.
2) isolation level of current transformer is required to realize by control: first, energy 18 primary structure 25 of module isolation level with The isolation of 18 secondary structure 27 of module isolation level is transmitted；Second, energy passes between two H bridges of 18 secondary structure of module isolation level It passs；Third, the voltage between bipolarity direct-current micro-grid positive electrode bus 14 and bipolarity direct-current micro-grid middle line 15U po , bipolarity direct current Voltage between microgrid anode middle line 15 and bipolarity direct-current micro-grid negative electrode bus 16U on It is equal, and be equal to setting value, i.e.,U po =U on =U line _ ref .WhereinU line _ ref For the setting value of bipolarity direct-current micro-grid busbar voltage.Make unsteady flow utensil of the present invention as a result, The function of standby Industrial Frequency Transformer and balance of voltage device.
As shown in figure 5,18 primary structure H bridge of module isolation level exchange side, secondary structure H bridge 28 and H bridge 29 friendship Stream side output waveform is the symmetrical alternating current square-wave voltage that positive-negative half-cycle respectively accounts for 50%.δ1For 18 primary structure H bridge of module isolation level Exchange side voltageu 1Side voltage is exchanged with 18 secondary structure H bridge 28 of module isolation levelu 2Between angle.δ2For module isolation level 18 Primary structure H bridge exchanges side voltageu 1Side is exchanged with 18 secondary structure H bridge 29 of module isolation levelu 3Between angle.Wherein δ1, δ2 ∈[-π/2,π/2]；18 high frequency transformer pair side 1 of module isolation level is to the turn ratio of primary side windingn 2, 18 high frequency of module isolation level Transformer secondary 2 is respectively to the turn ratio of primary side windingn 3；u 2、u 3It is 1 voltage of high frequency transformer pair sideu 2' and high frequency transformer The voltage on secondary side 2u 3' conversion is to the voltage after primary side, shown in convert formula such as formula (1-10):
(1-10)
The control of current transformer isolation level uses phase shifting control, voltage, current double closed-loop, the triggering arteries and veins of all isolation level modules It rushes identical.
Control block diagram is as shown in fig. 7, control method is as follows:
The first step, Voltage loop control
Bipolarity direct-current micro-grid busbar voltage setting valueU line _ ref Subtract the DC side of the secondary side H bridge 28 of module isolation level 18 VoltageU po Afterwards, after PI controller, the given value of 28 DC side of H bridge output electric current is obtainedi dc_28_ref ；Bipolarity direct current is micro- Net busbar voltage setting valueU line _ ref Subtract the DC voltage of the secondary side H bridge 29 of module isolation level 18UonAfterwards, it is controlled by PI Device obtains the given value of 29 DC side of H bridge output electric currenti dc_29_ref 。
Second step, current loop control
i dc_28_ref Subtract 28 DC side of H bridge output electric currenti dc_28, the coupling phase shifting angle of H bridge 28 is obtained by PI controller Δδ1；i dc_29_ref Subtract 29 DC side of H bridge output electric currenti dc_29, the coupling phase shifting angle Δ of H bridge 29 is obtained by PI controller δ2。
Third step, decoupling control and phase shifting angle obtain
Δδ1With Δ δ2It is decoupled by formula (1-11), obtains the secondary side H bridge 28 of module isolation level 18 and module isolation level 18 Secondary side H bridge 29 exchanges the phase shifting angle δ of side voltage waveform1、δ2, in decoupling matricesG 11、G 12、G 21、G 22It can be by formula (1-12), (1- 13), (1-14), (1-15) are acquired.Whereinf s For the working frequency of 18 high frequency transformer of module isolation level；L 1For high frequency transformer Primary side winding leakage inductance,L 2For 1 winding leakage inductance of high frequency transformer pair side,L 3For 2 winding leakage inductance of high frequency transformer pair side.L 12For high frequency Equivalent conversion inductance between 1 winding of transformer primary winding and secondary side,L 13For 2 winding of high frequency transformer primary side winding and secondary side Between equivalent conversion inductance,L 23For equivalent conversion inductance of the high frequency transformer pair in 1 winding and pair between 2 windings, conversion Shown in formula such as formula (1-16),
(1-11)
(1-12)
(1-13)
(1-14)
(1-15)
(1-16)
According to phase shifting angle δ1、δ2Adjustment isolation level module secondary side H bridge 28 exchanges the voltage of side with H bridge 29, thus realization every The stabilization of transmitting and bipolarity direct-current micro-grid busbar voltage from grade energy.

Claims (3)

1. a kind of core current transformer for constructing bipolarity direct-current micro-grid, for the exchange distribution of middle pressure and low voltage dipole direct-current micro-grid The two-way interconnection of energy, it is characterised in that:
The current transformer includes input filter, rectification stage and isolation level three parts；Using Modular Structure Design；
The input filter input terminal exchanges distribution with middle pressure and is connected, and output end is connected with the side that exchanges of rectification stage；Rectification stage DC side is connected with isolation level primary side；The isolation level secondary side is connected with low voltage dipole direct-current micro-grid；
The input filter uses inductance mode filter；
Three single-phase inductance can be used in the inductance mode filter, and a three pole reactor can also be used；
The rectification stage is three-phase structure, including rectifier and output filter；
The exchange side of the rectifier is the exchange side of the rectification stage, and using star-like connection, every phase is all made of N number of H bridge Cascade structure, N are natural number；The output filter uses capacitor mode filter, is connected in parallel on the direct current of each H bridge of rectifier Side；
The isolation level is made of 3N mutually isostructural unit, and N is identical as the H bridge number of rectification stage；
Each unit includes primary structure, high-frequency isolation transformer, secondary structure three parts composition, and the isolation level unit is primary It is three port organizations that three H bridge topologys are formed with secondary structure；
The isolation level primary side refers to the primary structure of all isolation level units；The secondary side of the isolation level refers to institute There is the secondary structure of isolation level unit；
The H bridge DC side of the isolation level unit primary structure and the DC side parallel of rectification stage H bridge, exchange side and high-frequency isolation Transformer primary side is connected；
The H bridge 1 of the isolation level unit secondary structure exchanges side and is connected with high-frequency isolation transformer vice-side winding 1, the isolation Just extremely the anode of bipolarity DC bus, cathode are in bipolarity DC bus to 1 DC side of H bridge of grade unit secondary structure Line；The H bridge 2 of the isolation level unit secondary structure exchanges side and is connected with high-frequency isolation transformer vice-side winding 2, the isolation level Just extremely the middle line of bipolarity DC bus, cathode are the negative of bipolarity DC bus to 2 DC side of H bridge of unit secondary structure Pole；
The equal parallel connection direct electric capacity of voltage regulation of H bridge 1 and 2 DC side of H bridge of isolation level unit secondary structure, to form bipolarity direct current Bus structure；
The high-frequency isolation transformer is single primary side winding, two-pack side winding construction；
The modularized design refers to and constitutes a module by a unit of a H bridge of rectification stage and isolation level；
The exchange side of module is the exchange side of rectification stage H bridge, and the DC side of module is pair that isolation level unit secondary structure is formed Anode, middle line and the cathode of polarity DC bus；
The DC side of all modules is connected in parallel according to anode, middle line, cathode correspondence, forms the bipolar bus knot of core current transformer The DC side of structure；
To ultimately form the core converter structure.
2. the control method of current transformer according to claim 1, it is characterised in that: the control of the rectification stage uses following five A step:
(1) pressure exchanges the angle of A phase voltage in distribution in obtaining
Three-phase voltage in pressure exchange distribution in Sample ACu a 、u b 、u c , the coordinate transform rotated by three phase static to two-phase obtains Voltage power-less component under two-phase rotating coordinate system outu q , transformation for mula is such as shown in (1-3):
(1-3)
It is calculatedu q By PI controller, rate correction amount Δ is obtainedω,The correction amount is added with 100 π, is obtained current Angular speedω s ,ω s It is allowed to be 0, to guarantee the angle information obtained when the angle is greater than 2 π with 2 π modulus values after integral In the range of 0 ~ 2 π, then by the angleθThe coordinate transform for feeding back to formula (1-3) calculates in angle used, forms control Closed loop processed；
The angleθThe angle of A phase voltage in as current middle pressure exchange distribution 1；
(2) AC side of converter input current is decoupled
Sample the electric current of the current transformer input linei as 、i bs 、i cs ；
By transformation for mula (1-4), three-phase current is become to the watt current under rotating coordinate systemi d And reactive currenti q ；
Angle in formula is using acquisition in step (1)θValue；
(1-4)
(3) electric current of control AC side of converter input
Calculate separately the parallel filtering of each the 1st module of phase each module rectification stage H bridge DC side into Nth module of current transformer A, B, C The sum of voltage of capacitorU dc_a_sum 、U dc_b_sum 、U dc_c_sum , three's average value is sought later to be obtainedU dc_ave_sum , N*U dc_ref It subtractsU dc_ave_sum After PI controller, the given value of current transformer rectification stage input current active component is obtainedi d_ref ；
It willi d_ref It subtracts and watt current is inputted by the current transformer that step (2) obtaini d , current transformer exchange is obtained after PI controller The active component of output voltagev d ；" 0 ", which is subtracted, inputs reactive current by the current transformer that step (2) obtaini q , after PI controller To the reactive component of current transformer ac output voltagev q ；
By transformation for mula (1-5), the three-phase voltage modulating wave synthesized needed for AC side of converter is obtainedu as 、u bs 、u cs ；
(1-5)
(4) each phase DC side total voltage of A, B, C in the current transformer rectification stage is balanced, realizes the AC side of converter specific work The rectification of rate factor
By N*U dc_ref Subtract the electricity of the 1st module of A phase parallel filtering capacitor of each module rectification stage H bridge DC side into Nth module The sum of pressureU dc_a_sum , after PI controller, obtain A phase power compensation amountP ao；N*U dc_ref The 1st module of B phase is subtracted to N mould The sum of the voltage of the parallel filtering capacitor of each module rectification stage H bridge DC side in blockU dc_b_sum , after PI controller, obtain B Phase power compensation amountP bo；
Utilize formula (1-6), formula (1-7) and formula (1-8):
(1-6)
(1-7)
(1-8)
Acquire the residual voltage amplitude that modulating wave needs to injectU 0And angleθ 0, thus the residual voltage injectedu 0 ；
It willu 0 The modulating wave obtained with (3) stepu as 、u bs 、u cs It is separately summed, synthesis needed for obtaining current transformer rectification stage exchange side Three-phase voltage modulating wave correction waveformu as_c 、u bs_c 、u cs_c ；
Current transformer rectification stage output A, B, C three-phase exports respectivelyu as_c 、u bs_c 、u cs_c Voltage waveform, unit power can be realized Factor rectification；
(5) module rectification stage dc-voltage balance controls
In the current transformer A phase, by the voltage setting value of module rectification stage parallel filtering capacitorU dc_ref It is whole to subtract k-th of module Flow the voltage of the parallel filtering capacitor of gradeu a _ dc_k , k-th of module rectification stage exchange side output electric current is obtained after PI controller The coefficient ε of modulating wave a_k , by the coefficient multiplied byu as_c / N obtains k-th of the module rectification stage exchange side output of final current transformer A phase Modulating waveu a_k_m ,u as_c It is obtained by step (4)；Final current transformer A phase n-th module rectification stage can be obtained using formula (1-9) Exchange the modulating wave of side outputu a_N_m ；Wherein k is integer, value range [1, N-1]
Later, by the way of SPWM, modulating wave is converted to the H bridge semiconductor devices of pwm signal control module rectification stage, In act on triangular carrier angle mutual deviation π/N of each H bridge of A phase module rectification stage；
(1-9)
Similarly, the modulating wave that current transformer B phase exchanges side output with each module rectification stage of C phase can be obtainedu b_x_m 、u c_x_m , x is whole here Number, value range [1, N]；
It is equal to be achieved in module rectification stage DC voltage, and is equal to setting valueU dc_ref , that is, meet the capacitor of each H bridge DC side Voltage is equal to setting value, achievees the purpose that exchange side unit power factor rectifier.
3. the control method of current transformer according to claim 1, it is characterised in that:
Module isolation level primary structure H bridge exchange side, the H bridge 1 of secondary structure and the exchange side output waveform of H bridge 2 are positive Negative half period respectively accounts for 50% symmetrical alternating current square-wave voltage；
δ1Side voltage is exchanged for module isolation level primary structure H bridgeu 1Side voltage is exchanged with module isolation level secondary structure H bridge 1u 2 Between angle；
δ2Side voltage is exchanged for module isolation level primary structure H bridgeu 1Side is exchanged with module isolation level secondary structure H bridge 2u 3Between Angle；
Wherein δ1, δ2∈[-π/2,π/2]；Module isolation level high frequency transformer pair side 1 is to the turn ratio of primary side windingn 2, module every It is respectively to the turn ratio of primary side winding from grade high frequency transformer pair side 2n 3；u 2、u 3It is 1 voltage of high frequency transformer pair sideu 2' and it is high The voltage on frequency power transformer pair side 2u 3' conversion is to the voltage after primary side, shown in convert formula such as formula (1-10):
(1-10)
The control of the current transformer isolation level uses phase shifting control, voltage, current double closed-loop；
The trigger pulse of all isolation level modules is identical；
The isolation level control uses following five steps:
(1) Voltage loop controls
Bipolarity direct-current micro-grid busbar voltage setting valueU line _ ref Subtract the DC voltage of module isolation level pair side H bridge 1U po Afterwards, after PI controller, the given value of 1 DC side of H bridge output electric current is obtainedi dc_28_ref ；Bipolarity direct-current micro-grid bus electricity Press setting valueU line _ ref Subtract the DC voltage of module isolation level pair side H bridge 2U on Afterwards, H bridge 2 is obtained directly by PI controller Flow the given value of side output electric currenti dc_29_ref ；
(2) current loop control
i dc_28_ref Subtract 1 DC side of H bridge output electric currenti dc_28, the coupling phase shifting angle Δ δ of H bridge 1 is obtained by PI controller1；i dc_29_ref Subtract 2 DC side of H bridge output electric currenti dc_29, the coupling phase shifting angle Δ δ of H bridge 1 is obtained by PI controller2；
(3) decoupling control and phase shifting angle obtain
Δδ1With Δ δ2It is decoupled by formula (1-11), obtains module isolation level pair H bridge 2 in H bridge 1 and module isolation level pair Exchange the phase shifting angle δ of side voltage waveform1、δ2, in decoupling matricesG 11、G 12、G 21、G 22Can by formula (1-12), (1-13), (1-14), (1-15) is acquired；
Whereinf s For the working frequency of module isolation level high frequency transformer；L 1For high frequency transformer primary side winding leakage inductance,L 2For high frequency 1 winding leakage inductance of transformer secondary,L 3For 2 winding leakage inductance of high frequency transformer pair side；
L 12For the equivalent conversion inductance between high frequency transformer primary side winding and secondary 1 winding of side,L 13For high frequency transformer primary side around Equivalent conversion inductance between 2 winding of group and secondary side,L 23It is equivalent between 2 windings in 1 winding and pair for high frequency transformer pair Inductance is converted, shown in convert formula such as formula (1-16)；
(1-11)
(1-12)
(1-13)
(1-14)
(1-15)
(1-16)
According to phase shifting angle δ1、δ2Adjustment isolation level module secondary side H bridge 1 exchanges the voltage of side with H bridge 2, realizes isolation level energy The stabilization of transmitting and bipolarity direct-current micro-grid busbar voltage；
To which the isolation level of the current transformer realizes energy in module isolation level primary structure and module isolation level secondary structure Isolation transmitting；Realize that energy transmits between two H bridges of module isolation level secondary structure；Bipolarity direct-current micro-grid positive electrode bus with Voltage between bipolarity direct-current micro-grid middle lineU po , between bipolarity direct-current micro-grid middle line and bipolarity direct-current micro-grid negative electrode bus VoltageU on It is equal, and be equal to setting value, i.e.,U po =U on =U line_ref , whereinU line_ref For bipolarity direct-current micro-grid busbar voltage Setting value.
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