CN205389177U - Novel many level of modularization type solid -state transformer - Google Patents

Abstract

The utility model provides a novel many level of modularization type solid -state transformer, solid -state transformer includes modularization multi -level converter, DC -DC isolator and DC -AC dc -to -ac converter, the high voltage alternating current net is connected to modularization multi -level converter 's interchange side, and the direct current side is connected the input of DC -DC isolator, the direct current side of DC -AC dc -to -ac converter is connected the output of DC -DC isolator exchanges the side and connects low pressure AC electric network or load, through the quantity that changes the power submodule piece that every bridge arm of modularization multi -level converter establishes ties, transfer solid -state transformer's voltage application scope in a flexible way, effectual solution solid -state transformer is at the application problem of middle and high voltage occasion.

Description

A kind of novel modular multilevel type solid-state transformer

Technical field

This utility model relates to a kind of solid-state transformer (SolidStateTransformer, SST), is specifically related to a kind of novel modular multilevel type solid-state transformer (MMC-SST).

Background technology

Solid-state transformer be a kind of based on high-power electric and electronic converter technique realize voltage transformation and energy transmission novel intelligent power transformer.Along with proposition and the development of energy interacted system, solid-state transformer, as its key equipment electric energy router, receives more and more many concerns.

Up to now, on the topological structure implementation and control method of SST, certain achievement in research is had been achieved for both at home and abroad.At present, solid-state transformer mainly has traditional two level or three level VSC (VoltageSourceConverter) type solid-state transformers and H bridge cascading multiple electrical level solid-state transformer.But, two level SST are applied to mesohigh occasion, it usually needs by input stage all-controlling power electronics device string (and) connection use, this be accomplished by solve all pressure (current-sharing) problem, just at present, this or a very big challenge.H bridge cascade connection multi-level current transformer is applied to the needs that can meet mesohigh application scenario in solid-state transformer, but it needs substantial amounts of full-controlled switch device and high frequency transformer, and high frequency transformer accounts for the passive device of very big proportion as volume and weight in SST, it uses the power density being unfavorable for improving solid-state transformer in a large number.Additionally, control the system another core technology as solid-state transformer, its quality will directly affect the service behaviour of whole system.The mathematical model that the design of current solid-state transformer controller is all based on greatly under dq rotating coordinate system setting up, adopts based on the double circle controling mode of PI controller, and the independence being realized active power and reactive power by dq uneoupled control is controlled.Although system has good response performance, but due to needs cross decoupling, and feedback decoupling effect is sensitive to Parameters variation, so being difficult to full decoupled control, the quality controlling effect is overly dependent upon the mathematical model of controlled device, and controls relative complex.

Utility model content

In view of this, for the deficiency of existing solid-state transformer topological structure implementation, the purpose of this utility model is in that to provide a kind of novel modular multilevel type solid-state transformer (MMC-SST).

For achieving the above object, the technical scheme that this utility model provides is as follows:

A kind of novel modular multilevel type solid-state transformer, including modular multi-level converter, DC-DC isolator and DC-AC inverter；

The AC of described modular multi-level converter connects High-voltage AC Network, DC side connects the input of described DC-DC isolator, the DC side of described DC-AC inverter connects the outfan of described DC-DC isolator, and AC connects low-voltage alternating-current electrical network or load.

nullFurther，Described modular multi-level converter includes the first unsteady flow bridge、Second unsteady flow bridge and the 3rd unsteady flow bridge，The input of described unsteady flow bridge is as a phase of three-phase alternating current input，Described unsteady flow bridge includes positive convertor arm、Negative convertor arm、First filter reactor and the second filter reactor，The anode of described positive convertor arm is connected to the direct current anode of described modular multi-level converter，And then it is connected to the anode of described DC-DC isolator，The negative terminal of described positive convertor arm is connected with a phase of electrical network by described first filter reactor，The negative terminal of described negative convertor arm is connected to the direct current negative terminal of described modular multi-level converter，And then it is connected to the negative terminal of described DC-DC isolator，The anode of described negative convertor arm is connected with a phase of electrical network by described second filter reactor，Described positive convertor arm/negative convertor arm includes the power modules of multiple positive-negative series successively，The DC side of described power modules is positive and negative to be connected with the positive and negative of high-voltage direct current power grid respectively.

Further, described power modules includes direct current capacitors, the first switching device, second switch device, the first fly-wheel diode and the second fly-wheel diode, and described first switching device and second switch device are full-control type semiconductor switch device；

The colelctor electrode of described first switching device is connected with the negative electrode of described first fly-wheel diode, and the emitter stage of described first switching device is connected with the anode of described first fly-wheel diode；The colelctor electrode of described second switch device is connected with the negative electrode of described second fly-wheel diode, and the emitter stage of described second switch device is connected with the anode of described second fly-wheel diode；The anode of described direct current capacitors is connected with the colelctor electrode of described first switching device, and the negative terminal of described direct current capacitors is connected with the emitter stage of described second switch device；The emitter stage of described first switching device is as the anode of described power modules, and the emitter stage of described second switch device is as the negative terminal of described power modules.

Further, described DC-DC isolator includes the first electric capacity, single-phase full-bridge inverter, high frequency transformer, single-phase full bridge commutator and the second electric capacity, in parallel described first electric capacity of the direct current input side of described DC-DC isolator forms direct-flow input end mouth, described first DC capacitor is connected with described single-phase full-bridge inverter, described single-phase full-bridge inverter and the series connection of described high frequency transformer, described high frequency transformer is connected with described single-phase full bridge commutator, described single-phase full bridge commutator forms DC output end mouth with described second Capacitance parallel connection, described DC output end mouth is connected with low-voltage direct electrical network, described direct-flow input end mouth is connected with the DC output end of described power modules.

Further, described DC-AC inverter is three-phase voltage source type inverter (VSI), is directly connected with low-voltage alternating-current electrical network or load by LC filter branch.

A kind of internal model control method to above-mentioned novel modularized many level-types solid-state transformer, comprises the following steps:

S1, modular multi-level converter control:

MMC outer shroud adopts PI controller to control DC voltage, internal ring adopts internal mode controller to realize alternating current DAZ gene is controlled, and adopt the capacitor voltage balance control strategy based on phase-shifting carrier wave technology, to realize the alternate Pressure and Control of MMC and submodule Pressure and Control.

The control of S2, DC-DC isolator:

DC-DC isolator adopts the DC-DC converter unit that N number of structure is identical to be formed by connecting by the mode of ISOP, the single-phase full-bridge inverter that the high direct voltage of MMC output first passes through the N number of structure controlled by same synchronizing signal identical is modulated into high frequency square wave, being coupled to assistant formula again through high frequency transformer, the single-phase full bridge commutator that N number of structure of finally being controlled by same synchronizing signal is identical is also made into low-voltage direct.

S3, DC-AC inverter control:

Inverter outer shroud adopts PI controller to control the power frequency ac voltage that output is stable, internal ring adopts internal mode controller that feedback current and the load-current feedforward of filter inductance are compensated electric current and carry out DAZ gene control, and adopts space voltage vector modulation technology (SVPWM).

Further, in step S1, when model mates with control object MMC, input can be carried out DAZ gene, order

$C_M\left(s\right)=G^{-1}\left(s\right)=\left(\begin{array}{cc}{R}^{\′}+sL& -{\mathrm{\ωL}}^{\′}\\ {\mathrm{\ωL}}^{\′}& R+{\mathrm{sL}}^{\′}\end{array}\right)$

In formula, C_MS () is internal mode controller, G^-1S () is the inverse matrix of control object model, the estimated value of R ', L ' respectively input side resistance and inductance, ω is system angle frequency, and s is regarded as j ω by equivalence；

C_MS the form of () cannot realize in practice, it is necessary to add low pass filter, introduce a low-pass first order filter

$L\left(s\right)=\frac{\mathrm{\λ}}{s+\mathrm{\λ}}I$

In formula, L (s) is low-pass first order filter, and λ is closed-loop bandwidth, and I is unit matrix；

After introducing low pass filter, inner membrance controller becomes:

$C_M\left(s\right)=G^{-1}\left(s\right)L\left(s\right)=\left(\begin{array}{cc}{R}^{\′}+sL& -{\mathrm{\ωL}}^{\′}\\ {\mathrm{\ωL}}^{\′}& R+{\mathrm{sL}}^{\′}\end{array}\right)L\left(s\right)$

Equivalent block diagram is controlled, in conjunction with C by inner membrance_MS () can obtain:

$F\left(s\right)==\mathrm{\λ}\left(\begin{array}{cc}L+R^{\′}/s& -{\mathrm{\ωL}}^{\′}/s\\ {\mathrm{\ωL}}^{\′}/s& L+R^{\′}/s\end{array}\right)$

In formula, F (s) is inner membrance decoupling equivalence matrix, and on leading diagonal, element is current controller transmission function expression, and on back-diagonal, element is then the transmission function of Internal Model Decoupling network；

Decoupling based on internal model control realizes method particularly as follows: AC network is surveyed voltage U_sabcThrough a phase-locked loop pll, obtain its system angle frequencies omega_s, converted by abc-dq simultaneously, obtain dq component: U_dAnd U_q；AC network surveys electric current I_sabcConverted by abc-dq, obtain dq component: i_dAnd i_q；DC bus-bar voltage U_DCWith voltage reference value U^* _DCAfter subtracting each other, obtain instruction current i through PI controller^* _d；AC network surveys idle Q and reactive power reference qref Q^*Equally through PI controller after subtracting each other, obtain instruction current i^* _q, these signals realize the input of figure as the decoupling shown in Fig. 8 in the present embodiment, can obtain command signal u^* _dAnd u^* _q；U_d、U_qRespectively with u^* _d、u^* _qSubtract each other, obtain U_rd、U_rq, abc three-phase command voltage can be obtained through dq-abc inverse transformation, as the input signal of phase-shifting carrier wave modulation, above-mentioned middle U_d、U_qAnd I_d、I_qRespectively line voltage and electric current component on d axle and q axle.

Further, in step S2, wherein N number of inverter and commutator all adopt PWM control, and the complementation driving signal to be 50% dutycycle triggers pulse, and adopt active power balance control method, make full-controlled switch device be in Zero Current Switch state by rationally arranging series resonant circuit.

Further, in step S3, concrete control process is as follows:

Load side voltage U_lkLoad voltage angular frequency is obtained through a phase-locked loop pll_l, it is as the input of abc-dq and dq-abc conversion module, obtains dq axle component U through abc-dq conversion simultaneously_ld、U_lq, load-side electric current I_lkDq axle component I is obtained through abc-dq conversion_ld、I_lq, inverter output current I_ikDq axle component I is obtained through abc-dq conversion_id、I_iq, above-mentioned middle I_id、I_iq, U_id、U_iqFor d axle component under dq rotating coordinate system of three-phase DC/AC inverter output current, voltage and q axle component, U_ld、U_lq, I_ld、I_lqFor d axle component under dq rotating coordinate system of load voltage, electric current and q axle component.

Compared with prior art, the beneficial effects of the utility model are in that:

(1) in topological structure, the input stage of this solid-state transformer adopts modular multi-level converter, by increasing and decreasing the number of each brachium pontis sub-series module, adjust the voltage scope of application of current transformer neatly, solid-state transformer can be made to apply to high voltage, high-power field according to application needs.Modular multi-level converter, compared with other type of Multilevel Inverters, has main circuit simple, and device loss is little, and floor space is little, and cost is low, it is simple to modularized design, all brings facility for the design of solid-state transformer device, production, maintenance；

(2) in control method, it is proposed that a kind of novel double-closed-loop control method that internal mold current inner loop is combined with PI outer voltage.This control mode can make electric current have response speed and higher Ability of Resisting Disturbance faster.Meanwhile, this control method avoids the cross decoupling problem under biphase rotating coordinate system, reduces the complexity of Control System Design to a certain extent.

Accompanying drawing explanation

Fig. 1 is the structural framing figure of a kind of modular multilevel type solid-state transformer that the utility model proposes；

Fig. 2 is the topological structure schematic diagram of a kind of modular multilevel type solid-state transformer that the utility model proposes；

Fig. 3 is the structural representation of the modular multi-level converter (MMC) in this utility model；

Fig. 4 is the electrical block diagram of the power modules in this utility model；

Fig. 5 is the electrical block diagram of the DC-DC isolator that this utility model uses；

Fig. 6 is the electrical block diagram of the voltage source inverter that this utility model uses；

Fig. 7 is the internal model control block diagram that this utility model provides；

Fig. 8 is the internal model control block diagram isoboles that this utility model provides；

Fig. 9 is that this utility model provides internal model control method to realize the theory diagram of decoupling；

Figure 10 is the high-pressure side MMC control principle drawing that this utility model provides；

Figure 11 is the low-pressure side inverter control schematic diagram that this utility model provides；

Figure 12 is IMC and the PI that this utility model the realizes current vs figure controlling MMC.

Detailed description of the invention

Below in conjunction with drawings and Examples, a kind of novel modular multilevel type solid-state transformer described in the utility model and internal model control method thereof are described further.

Refer to Fig. 1 and Fig. 2, Fig. 1 is the structural framing figure of a kind of modular multilevel type solid-state transformer that the utility model proposes, Fig. 2 is the topological structure schematic diagram of a kind of modular multilevel type solid-state transformer that the utility model proposes, specifically, described novel modular multilevel type solid-state transformer, including modular multi-level converter, DC-DC isolator and DC-AC inverter；The AC of described modular multi-level converter connects High-voltage AC Network, DC side connects the input of described DC-DC isolator, the DC side of described DC-AC inverter connects the outfan of described DC-DC isolator, and AC connects low-voltage alternating-current electrical network or load；Described modular multi-level converter has direct current anode, direct current negative terminal and three-phase alternating current input.

In the present embodiment, described electrical network is High-Voltage Network, and described modular multi-level converter can be joined directly together with electrical network, by changing the number energy flexible adaptation electric pressure of submodule, and can effectively reduce harmonic wave, improve the quality of power supply.

Fig. 3 has illustrated the structured flowchart of modular multi-level converter in this utility model, specifically, described modular multi-level converter includes A phase unsteady flow bridge, B phase unsteady flow bridge and C phase unsteady flow bridge, one phase of the input of each unsteady flow bridge respectively three-phase alternating current input, wherein, each unsteady flow bridge includes a positive convertor arm, a negative convertor arm and two filter reactors；Each convertor arm includes the power modules of multiple positive-negative series successively, namely the anode of a power modules is connected to the negative terminal of another power modules, multiple power modules are sequentially connected with, and the power modules being positioned at two ends forms anode and the negative terminal of convertor arm respectively.Positive convertor arm includes the multiple power modules being numbered SM1 to SMN, and negative convertor arm also includes the multiple power modules being numbered SM1 to SMN, and the quantity namely comprising power modules in positive convertor arm and negative convertor arm is equal.

In each unsteady flow bridge, the anode of positive convertor arm is connected to the direct current anode of modular multi-level converter, and then is connected to the anode of DC-DC isolator, and the negative terminal of positive convertor arm is connected with a phase of electrical network by a filter reactor；The negative terminal of negative convertor arm is connected to the direct current negative terminal of modular multi-level converter, and then is connected to the negative terminal of DC-DC isolator, and the anode of negative convertor arm is connected with a phase of electrical network by another filter reactor.

Fig. 4 is the electrical block diagram of the power modules in this utility model, and each power modules includes direct current capacitors Cd, the first switching device S1, second switch device S2, the first fly-wheel diode VD1 and the second fly-wheel diode VD2；Wherein, described first switching device S1 and second switch device S2 is full-control type semiconductor switch device.The colelctor electrode of the first switching device S1 and the negative electrode of the first fly-wheel diode VD1 are connected, and the emitter stage of the first switching device S1 and the anode of the first fly-wheel diode VD1 are connected；The colelctor electrode of second switch device S2 and the negative electrode of the second fly-wheel diode VD2 are connected, and the emitter stage of second switch device S2 and the anode of the second fly-wheel diode VD2 are connected；The anode of direct current capacitors C and the colelctor electrode of the first switching device S1 are connected, and the negative terminal of direct current capacitors C is connected with the emitter stage of second switch device S2；The emitter stage of the first switching device S1 is as the anode of power modules, and the emitter stage of second switch device S2 is as the negative terminal of power modules.

Fig. 5 illustrates the structure chart of described DC-DC isolator, described DC-DC isolator has the DC-DC converter unit that each structure of N is identical, and each DC-DC converter unit is composed in series by a single-phase full-bridge inverter, a high frequency transformer and a single-phase full bridge commutator；High frequency transformer in DC-DC isolator realizes electric pressure conversion and electrical isolation, single-phase full bridge commutator in described DC-DC isolator adopts the form of Parallel opertation, its input is connected with described high frequency transformer, the anode of output is connected with the anode of described DC-AC inverter, and the negative terminal of output is connected with the negative terminal of described DC-AC inverter.

Fig. 6 gives the structure chart of described DC-AC inverter, and described DC-AC inverter is the three-phase full-bridge inverter of voltage-source type, and its input is connected with the output of above-mentioned DC-DC isolator, and output is directly connected with low-voltage alternating-current electrical network or load by LC filter branch.

A kind of modular multilevel type solid-state transformer that the present embodiment provides adopts modular multi-level converter, by increasing and decreasing the number of each brachium pontis sub-series module, it is possible to make solid-state transformer apply to different voltage domain.Compared with conventional solid-state transformator, this novel solid-state transformer advantage in High-Voltage Network is fairly obvious.

For solving the problem of dq cross decoupling in conventional solid-state transformator control method, simplify the design of controller, reduce and calculate.The present embodiment provides the control method of the solid-state transformer of a kind of modularity level current transformer described above, the novel double-closed-loop control method being combined by internal mold current inner loop with PI outer voltage.

Internal model control (IMC) is the novel control mode that a kind of Kernel-based methods mathematical model is controlled device design, has simple in construction, follows the tracks of the advantages such as good, the strong robustness of performance of control, is widely used in Control of Nonlinear Systems field.

Fig. 7 show internal model control structure block diagram, wherein, R (s), Y (s) respectively system input and output signal, C_MS () is internal mode controller, G (s) is control object, the internal mold that M (s) is control object, and D (s) is disturbance, and d (s) exports Y (s) and internal mold output Y for system_mThe difference of (s).

Control method in the present embodiment includes following step:

S1, modular multi-level converter control；

The control of S2, DC-DC isolator；

S3, DC-AC inverter control.

Concrete, in step S1, modular multi-level converter outer shroud adopts PI controller to control DC voltage, and internal ring adopts internal mode controller to realize alternating current DAZ gene is controlled.The present embodiment also adopts the capacitor voltage balance control strategy based on phase-shifting carrier wave technology, to realize the alternate Pressure and Control of MMC and submodule Pressure and Control.

By the feature of internal model control, when model mates with control object (MMC), input can be carried out DAZ gene, order

$C_M\left(s\right)=G^{-1}\left(s\right)=\left(\begin{array}{cc}{R}^{\′}+sL& -{\mathrm{\ωL}}^{\′}\\ {\mathrm{\ωL}}^{\′}& R+{\mathrm{sL}}^{\′}\end{array}\right)$

In formula, G^-1S () is the inverse matrix of control object model, the estimated value of R ', L ' respectively input side resistance and inductance, ω is system angle frequency, and s is regarded as j ω by equivalence；

C_MS the form of () cannot realize in practice, it is necessary to add low pass filter, makes system stability by regulating the structure and parameter of low pass filter.In the present embodiment, introduce a low-pass first order filter

$L\left(s\right)=\frac{\mathrm{\λ}}{s+\mathrm{\λ}}I$

In formula, L (s) is low-pass first order filter, and λ is closed-loop bandwidth, and I is unit matrix.

After introducing low pass filter, inner membrance controller becomes:

$C_M\left(s\right)=G^{-1}\left(s\right)L\left(s\right)=\left(\begin{array}{cc}{R}^{\′}+sL& -{\mathrm{\ωL}}^{\′}\\ {\mathrm{\ωL}}^{\′}& R+{\mathrm{sL}}^{\′}\end{array}\right)L\left(s\right)$

Fig. 8 show the equivalent control block diagram of internal mode controller, inner membrance control equivalent block diagram, in conjunction with C_MS () can obtain:

$F\left(s\right)==\mathrm{\λ}\left(\begin{array}{cc}L+R^{\′}/s& -{\mathrm{\ωL}}^{\′}/s\\ {\mathrm{\ωL}}^{\′}/s& L+R^{\′}/s\end{array}\right)$

In formula, F (s) is inner membrance decoupling equivalence matrix, and on leading diagonal, element is current controller transmission function expression, and on back-diagonal, element is then the transmission function of Internal Model Decoupling network, internal model control method the Internal Model Decoupling figure realized is as shown in Figure 9.

As shown in Figure 10, in procedures described above S1, the decoupling based on internal model control realizes method particularly as follows: AC network is surveyed voltage U_sabcThrough a phase-locked loop pll, obtain its system angle frequencies omega_s, converted by abc-dq simultaneously, obtain dq component: U_dAnd U_q.AC network surveys electric current I_sabcConverted by abc-dq, obtain dq component: i_dAnd i_q；DC bus-bar voltage U_DCWith voltage reference value U^* _DCAfter subtracting each other, obtain instruction current i through PI controller^* _d；AC network surveys idle Q and reactive power reference qref Q^*Equally through PI controller after subtracting each other, obtain instruction current i^* _q, these signals realize the input of figure as the decoupling shown in Fig. 9 in the present embodiment, can obtain command signal u^* _dAnd u^* _q。U_d、U_qRespectively with u^* _d、u^* _qSubtract each other, obtain U_rd、U_rq, abc three-phase command voltage can be obtained through dq-abc inverse transformation, as the input signal of phase-shifting carrier wave modulation, above-mentioned middle U_d、U_qAnd I_d、I_qRespectively line voltage and electric current component on d axle and q axle.

In step S2, the control of DC-DC isolator is included: DC-DC isolator adopts the DC-DC converter unit that N number of structure is identical to be formed by connecting by the mode of ISOP.The single-phase full-bridge inverter that the high direct voltage of MMC output first passes through the N number of structure controlled by same synchronizing signal identical is modulated into high frequency square wave, it is coupled to assistant formula again through high frequency transformer, the single-phase full bridge commutator that the last N number of structure controlled by same synchronizing signal is identical is also made into low-voltage direct, N number of inverter therein and commutator all adopt PWM control, and the complementation driving signal to be 50% dutycycle triggers pulse.The high frequency transformer parameter caused for solving ISOP connected mode does not mate problem unequal with DC voltage, the present embodiment have employed a kind of active power Balance route strategy, additionally, in order to reduce system loss, by rationally arranging series resonant circuit (L_rAnd C_r) make full-controlled switch device be in Zero Current Switch state (ZCS).

As shown in figure 11, in step S3, the control of DC-AC inverter includes: outer shroud adopts PI controller to control the power frequency ac voltage that output is stable, internal ring adopts internal mode controller that feedback current and the load-current feedforward of filter inductance are compensated electric current and carry out DAZ gene control so that it is have bigger current limiting capacity, good dynamic response performance and stronger anti-disturbance ability concurrently.It is essentially identical that inner membrance control method described herein and inner membrance control decoupling principle figure and MMC.Concrete control method and inner membrance control decoupling principle figure such as shown in Figure 11 and Fig. 9.Meanwhile, in order to improve inverter direct-current voltage utilization rate, reducing switching loss, the present embodiment adopts space voltage vector modulation technology (SVPWM).

Load side voltage U_lkLoad voltage phase place ω is obtained through a phase-locked loop pll_l, it is as the input of abc-dq and dq-abc conversion module, obtains dq axle component U through abc-dq conversion simultaneously_ld、U_lq.Load-side electric current I_lkDq axle component I is obtained through abc-dq conversion_ld、I_lq.Inverter output current I_ikDq axle component I is obtained through abc-dq conversion_id、I_iq, above-mentioned middle I_id、I_iq, U_id、U_iqFor d axle component under dq rotating coordinate system of three-phase DC/AC inverter output current, voltage and q axle component, U_ld、U_lq, I_ld、I_lqFor d axle component under dq rotating coordinate system of load voltage, electric current and q axle component.In Figure 11, ω is power angle frequency, C_fFor filtering capacitance.

For control method set forth above, it is controlled effect and has verified by the present embodiment, and the working condition of concrete consideration is: grid side power factor change.Figure 12 show, the comparison of wave shape figure of the dq current component of modular multi-level converter when adopting IMC to control to control with PI.

Concrete has, and the DC voltage set-point of modular multi-level converter 1 is always 18kV, output stage band three-phase balancing load.During original state, the idle set-point of input stage is 0.625Mvar, and namely net side power factor is 0.95 (absorbing idle)；During 0.3s, reactive power set-point becomes-0.65Mvar, and namely net side power factor is 0.95 (sending idle)；During 0.4s, idle set-point is 0, and namely net side unity power factor runs.When modular multi-level converter 1 described in this utility model is adopted IMC control and adopts PI to control by Figure 12, dq current component tracking effect under above-mentioned operating mode has contrasted: can be seen that from the dq shaft current waveform provided,, reactive power meritorious in increase and decrease gives timing, adopts IMC control mode ratio to adopt PI control mode current inner loop response speed faster.During 0.3s, rectification side reactive power is given there is step sudden change, it can be seen that the d shaft current that PI controls fluctuates substantially, and the electric current under IMC control mode is very steady.Can to realize dq current decoupled control and performance of noiseproof stronger than PI control mode for IMC control mode as can be seen here, it is possible to is apparent from this utility model and adopts the MMC-SST controller of IMC internal ring control method to have response speed and higher capacity of resisting disturbance faster compared with ring controller in traditional PI.

In this utility model, the input stage of solid-state transformer adopts modular multi-level converter (Modularmultilevelconverter, MMC), by increasing and decreasing the number of each brachium pontis sub-series module, makes solid-state transformer apply to different voltage domain.In order to enable MMC-SST to run according to given power factor, and there is the advantages such as voltage, electric current dynamic response is fast, anti-disturbance ability is strong, characteristic according to internal model control, it is proposed that a kind of novel double-closed-loop control method that internal mold current inner loop is combined with PI outer voltage.This control mode can make electric current have response speed and higher Ability of Resisting Disturbance faster.Meanwhile, this control method avoids the cross decoupling problem under biphase rotating coordinate system, reduces the complexity of Control System Design to a certain extent.

Embodiment described above only have expressed several embodiments of the present utility model, and it describes comparatively concrete and detailed, but therefore can not be interpreted as the restriction to this utility model the scope of the claims.It should be pointed out that, for the person of ordinary skill of the art, without departing from the concept of the premise utility, it is also possible to make some deformation and improvement, these broadly fall into protection domain of the present utility model.Therefore, the protection domain of this utility model patent should be as the criterion with claims.

Claims (5)

1. modular multilevel type solid-state transformer one kind novel, it is characterised in that include modular multi-level converter, DC-DC isolator and DC-AC inverter；

The AC of described modular multi-level converter connects High-voltage AC Network, DC side connects the input of described DC-DC isolator, the DC side of described DC-AC inverter connects the outfan of described DC-DC isolator, and AC connects low-voltage alternating-current electrical network or load.

null2. modular multilevel type solid-state transformer as claimed in claim 1，It is characterized in that，Described modular multi-level converter includes the first unsteady flow bridge、Second unsteady flow bridge and the 3rd unsteady flow bridge，The input of described unsteady flow bridge is as a phase of three-phase alternating current input，Described unsteady flow bridge includes positive convertor arm、Negative convertor arm、First filter reactor and the second filter reactor，The anode of described positive convertor arm is connected to the direct current anode of described modular multi-level converter，And then it is connected to the anode of described DC-DC isolator，The negative terminal of described positive convertor arm is connected with a phase of electrical network by described first filter reactor，The negative terminal of described negative convertor arm is connected to the direct current negative terminal of described modular multi-level converter，And then it is connected to the negative terminal of described DC-DC isolator，The anode of described negative convertor arm is connected with a phase of electrical network by described second filter reactor，Described positive convertor arm/negative convertor arm includes the power modules of multiple positive-negative series successively，The DC side of described power modules is positive and negative to be connected with the positive and negative of high-voltage direct current power grid respectively.

3. modular multilevel type solid-state transformer as claimed in claim 2, it is characterized in that, described power modules includes direct current capacitors, the first switching device, second switch device, the first fly-wheel diode and the second fly-wheel diode, and described first switching device and second switch device are full-control type semiconductor switch device；

The colelctor electrode of described first switching device is connected with the negative electrode of described first fly-wheel diode, and the emitter stage of described first switching device is connected with the anode of described first fly-wheel diode；The colelctor electrode of described second switch device is connected with the negative electrode of described second fly-wheel diode, and the emitter stage of described second switch device is connected with the anode of described second fly-wheel diode；The anode of described direct current capacitors is connected with the colelctor electrode of described first switching device, and the negative terminal of described direct current capacitors is connected with the emitter stage of described second switch device；The emitter stage of described first switching device is as the anode of described power modules, and the emitter stage of described second switch device is as the negative terminal of described power modules.

4. modular multilevel type solid-state transformer as claimed in claim 2, it is characterized in that, described DC-DC isolator includes the first electric capacity, single-phase full-bridge inverter, high frequency transformer, single-phase full bridge commutator and the second electric capacity, in parallel described first electric capacity of the direct current input side of described DC-DC isolator forms direct-flow input end mouth, described first electric capacity is connected with described single-phase full-bridge inverter, described single-phase full-bridge inverter and the series connection of described high frequency transformer, described high frequency transformer is connected with described single-phase full bridge commutator, described single-phase full bridge commutator forms DC output end mouth with described second Capacitance parallel connection, described DC output end mouth is connected with low-voltage direct electrical network, described direct-flow input end mouth is connected with the DC output end of described power modules.

5. modular multilevel type solid-state transformer as claimed in claim 1, it is characterised in that described DC-AC inverter is three-phase voltage source type inverter, is directly connected with low-voltage alternating-current electrical network or load by LC filter branch.