CN104393777B - Half-bridge module multi-level converter submodule voltage control method - Google Patents

Abstract

A kind of half-bridge MMC submodule voltage control method, including step: A. presets half-bridge MMC DC voltage set-pointWith reactive power set-pointB. DC voltage u is measured_dcWith each cross streams voltage u_aWith electric current i_a, from described u_aMiddle acquisition voltage magnitude u_sAnd phase place；To i_aCarry out Park Transformation with phase place and obtain i_dgAnd i_qg；C., weight coefficient a is set_ij, by Σ a_ij(u_dci‑u_dcj) value withU is deducted after addition_dc, the output after outer shroud proportional integral link deducts i_dg, its difference after internal ring proportional integral link with u_s/ n is added and obtains u_dgi, wherein u_dciAnd u_dcjIt is respectively in n submodule i-th and the DC capacitor voltage of jth submodule；D. the reactive power measured, withDifference output after outer shroud proportional integral link and i_qgComparing, its difference, through internal ring proportional integral link, obtains u_qgi；E. to u_dgiAnd u_qgiCarry out Parker inverse transformation and obtain controlled quentity controlled variable u of the i-th submodule_agi, and control the switch of this submodule according to this.

Description

Half-bridge module multi-level converter submodule voltage control method

Technical field

The present invention relates to power electronic equipment field, particularly to each power switch in a kind of power electronic equipment The control technology of device.

Background technology

Along with developing rapidly of Power Electronic Technique, the pressure and power grade of single device for power switching all obtains To being greatly improved, the application of various high-power switch devices is the most increasingly extensive.But at many high-powers Application, traditional two level, three-level voltage source code converter topology cannot meet higher voltage and The requirement of power grade.On the premise of device for power switching does not has essence to break through, multi-level converter is undoubtedly It is to solve being preferably selected of high-power conversion.In order to improve while promoting power electronic equipment capacity Its performance, circuit topology and the control technology of high-power multi-level converter are studied by people.

Modular multilevel converter (Modular Multilevel Converter, MMC), public owing to having Dc bus, MMC may be implemented under inversion or rectification operating mode run, application is the widest.MMC Module topology structure has multiple, and most common of which is full bridge unit and half-bridge cells parallel connection direct capacitance structure. When group module topology structure is half-bridge cells parallel connection direct capacitance structure, each submodule is output as 0 and just Level.Half-bridge MMC is often made up of upper and lower 2 brachium pontis, and every brachium pontis contains n submodule, i.e. every phase By 2n sub-module composition, MMC output phase voltage is 2n-1 level.The submodule of each brachium pontis is permissible Carry out independently controlled, thus each brachium pontis can be equivalent to a controllable voltage source, by regulating each bridge The rate of change of arm voltage, it is possible to obtain required sinusoidal voltage at outfan, waveform is preferable, submodule quantity The most, output voltage waveforms is the best, but cost also increases.

Owing to each brachium pontis submodule of phase every in half-bridge MMC is numerous, and each submodule switch motion may Inconsistent, cause submodule DC capacitor voltage unbalanced, so cause half-bridge MMC output voltage waveforms Amount of distortion increases, and affects the quality of half-bridge MMC output voltage waveforms, will damage submodule if deviation is serious Block.

Additionally, during electrical network generation unbalanced fault, more cause DC capacitor voltage to distort, affect whole dress The safety operation level put.

Summary of the invention

In consideration of it, it is an object of the invention to avoid time in half-bridge MMC, each submodule switch motion is inconsistent The problem that the half-bridge MMC output voltage waveforms amount of distortion caused increases, improves half-bridge MMC output voltage ripple The quality of shape.

In order to realize this purpose, the technical scheme that the present invention takes is as follows.

A kind of half-bridge module multi-level converter submodule voltage control method, comprises the following steps: A. is pre- If DC voltage set-pointWith reactive power set-pointB. DC voltage u is measured_dcWith every cross streams electricity Pressure u_aWith alternating current i_a, from described u_aMiddle acquisition voltage magnitude u_sAnd phase place；To i_aParker is carried out with phase place Conversion obtains i_dgAnd i_qg；C., weight coefficient a is set_ij, by Σ a_ij(u_dci-u_dcj) value withU is deducted after addition_dc, It is then passed through the output after outer shroud proportional integral link and deducts i_dg, its difference after internal ring proportional integral link with u_s/ n is added and obtains u_dgi, wherein u_dciAnd u_dcjIt is respectively in n submodule i-th and the direct current of jth submodule Capacitance voltage；D. reactive power is measured,With the difference of described reactive power after outer shroud proportional integral link Output deduct i_qg, its difference, through internal ring proportional integral link, obtains u_qgi；E. to u_dgiAnd u_qgiSend Gram inverse transformation obtains controlled quentity controlled variable u of the i-th submodule_agi, control two switches of described submodule.

Wherein, described weight coefficient a_ij=(u_dci-u_dcj)/Σ(u_dci-u_dcj)。

Or, with each submodule DC capacitor voltage minimum target of capacity volume variance sum:

Σ_mina_ij(u_dci-u_dcj)²,

Constraints is: $(u_{\mathrm{dci}}-u_{\mathrm{dcj}})\≤{0.1u}_{\mathrm{dc}}^{*},$

u_a+u_b+u_c=0,

Determine a that optimal value is corresponding_ijFor weight coefficient.

It addition, the parameter of described internal ring proportional integral link is: 1 < proportionality coefficient < 10,0.1 < integral coefficient < 1.

The parameter of described outer shroud proportional integral link is: 0.2 < proportionality coefficient < 1,0.01 < integral coefficient < 0.1.

On the other hand, when electrical network generation unbalanced fault, farther include:

The alternating voltage of every phase is carried out α β coordinate transform, obtains the α β component of correspondence, passing ratio integration Feedback control and the feedback control of dual-integration, obtain the first group component；Simultaneously by this component and coefficient q phase Take advantage of, obtain second component amount；Calculated the positive-negative sequence component of α β by this 2 group component, submodule is just being carried out Negative sequence component controls respectively；

Wherein q expression formula is as follows:

Q=Q₀+Q_c2cos(2ωt)+Q_s2Sin (2 ω t),

Q₀For the fundamental reactive component of electrical network, Q_c2、Q_s2For idle quadratic component, ω is angular frequency.

By using the half-bridge MMC submodule voltage control method of the present invention, it is possible to make each submodule open Keeping strokes in pass, which thereby enhances the quality of half-bridge MMC output voltage waveforms.Meanwhile, half-bridge MMC The balance of submodule DC capacitor voltage, extends the service life of submodule.Therefore, not only increase whole The performance of body half-bridge MMC device, and improve the safety operation level of overall half-bridge MMC device.

On the other hand, by using the half-bridge MMC submodule voltage control method of the present invention, it is possible at electricity When there is unbalanced fault in net, it is to avoid cause the distortion of DC capacitor voltage, and then improve the peace of whole device Full operation level.

Accompanying drawing explanation

Fig. 1 is the circuit diagram of embodiment of the present invention half-bridge MMC device.

Fig. 2 is the embodiment of the present invention half-bridge voltage-controlled schematic diagram of MMC submodule.

Fig. 3 is another embodiment half-bridge voltage-controlled schematic diagram of MMC submodule of the present invention.

Fig. 4 is the output voltage waveform of the half-bridge MMC device of embodiment of the present invention.

Detailed description of the invention

Below in conjunction with the accompanying drawings, the present invention is elaborated.

The example embodiment that following discloses are detailed.But, concrete structure disclosed herein and function detail are only It is in order at the purpose describing example embodiment.

It should be appreciated, however, that the present invention is not limited to disclosed particular exemplary embodiment, but covers and fall into All modifications, equivalent and alternative in the range of the disclosure.In the description to whole accompanying drawings, identical Reference represents identical element.

It will also be appreciated that term "and/or" includes one or more relevant listing as used in this Any and all combination of item.It will further be appreciated that when parts or unit are referred to as " connection " or " coupling " During to another parts or unit, it can be directly connected or coupled to miscellaneous part or unit, or can also There is intermediate member or unit.Should be by additionally, be used for describing between parts or unit other words of relation Photograph with mode understand (such as, " and between " to " directly between ", " adjacent " to " direct neighbor " Deng).

As it is shown in figure 1, half-bridge MMC of the present invention is by 3 phase compositions, comprise upper and lower 2 bridges mutually Arm, each brachium pontis is made up of n submodule and a controller, and each submodule is by 2 full control derailing switches The half-bridge composition that part and anti-paralleled diode are constituted；The dc bus positive pole of described submodule and corresponding submodule The positive pole of block DC capacitor is connected, the dc bus negative pole of described submodule and corresponding submodule DC capacitor Negative pole be connected, the biphase series winding of outfan two of described submodule, the superiors' submodule of the upper brachium pontis of MMC Overlying one end is connected with MMC dc bus, one end and filter below the orlop submodule of the upper brachium pontis of MMC Ripple inductance is connected, and this cross streams outfan of the other end of filter inductance and MMC is connected；Described submodule The signal control end controlling end corresponding with controller is connected, the ac output end of described MMC and described control The ac voltage signal input that device processed is corresponding is connected.

Therefore, the half-bridge MMC submodule voltage control method of the present invention comprises the following steps:

A. predetermined DC voltage set-pointWith reactive power set-pointDescribed set-point is according to system requirements Determine；

B. DC voltage u is measured_dcWith every cross streams voltage u_aWith electric current i_a, from described u_aMiddle acquisition voltage amplitude Value u_sAnd phase place；To i_aCarry out Park Transformation with phase place and obtain i_dgAnd i_qg；

C., weight coefficient a is set_ij, described weight coefficient 0 < a_ij< 1, by Σ a_ij(u_dci-u_dcj) value withAfter addition Deduct u_dc, it is then passed through the output after outer shroud proportional integral link and deducts i_dg, its difference is through internal ring proportional integral With u after link_s/ n is added and obtains u_dgi, wherein u_dciAnd u_dcjIt is respectively in n submodule i-th and jth submodule The DC capacitor voltage of block；

D. reactive power is measured,With the output after outer shroud proportional integral link of the difference of described reactive power Deduct i_qg, its difference, through internal ring proportional integral link, obtains u_qgi；

E. to u_dgiAnd u_qgiCarry out Parker inverse transformation and obtain controlled quentity controlled variable u of the i-th submodule_agi, and control according to this The switch of this submodule.Specifically, each submodule is by 2 switch T_i1、T_i2Composition, T_i1With T_i2Open Pass control signal interlocking, T_i1Conducting and during Ti2 locking, submodule output positive level, otherwise, output zero electricity Flat；Therefore, 1 submodule controlled quentity controlled variable u_agi2 switches can be controlled.

By each submodule DC capacitor voltage difference is carried out dynamic sensing, effectively inhibit submodule unidirectional current Hold the dynamic differential of voltage.Hence in so that each submodule switch motion is consistent, which thereby enhance half-bridge MMC The quality of output voltage waveforms.

As one embodiment of the present of invention, determine that weight coefficient is a_ij=(u_dci-u_dcj)/Σ(u_dci-u_dcj), so The difference of each submodule can be embodied, therefore further increase the quality of output voltage waveforms.

As an alternative embodiment of the invention, determine that the method for weight coefficient is:

With each submodule DC capacitor voltage minimum target of capacity volume variance sum:

Σ_mina_ij(u_dci-u_dcj)²,

Constraints is: $(u_{\mathrm{dci}}-u_{\mathrm{dcj}})\&le;{0.1u}_{\mathrm{dc}}^{*},$

u_a+u_b+u_c=0,

Determine a that optimal value is corresponding_ijFor weight coefficient.

The method determining optimal value can be conventional various optimization methods, and those skilled in that art are The optimal way after target determines can be known.

In this embodiment, take the submodule DC capacitor voltage minimum target of capacity volume variance sum, it is possible to Switching device is made to operate in optimum state.

As an embodiment of the invention, the parameter of described internal ring proportional integral link is: 1 < ratio system Number < 10,0.1 < integral coefficient < 1；And the parameter of described outer shroud proportional integral link is: 0.2 < proportionality coefficient < 1, 0.01 < integral coefficient < 0.1.

It addition, in order to when electrical network generation unbalanced fault, it is to avoid cause the distortion of DC capacitor voltage, enter And improve the safety operation level of whole device, in another embodiment of the present invention, when electrical network generation is the most right When claiming fault, farther include:

The alternating voltage of every phase is carried out α β coordinate transform, obtains the α β component of correspondence, passing ratio integration Feedback control and the feedback control of dual-integration, obtain the first group component；Simultaneously by this component and coefficient q phase Take advantage of, obtain second component amount；Calculated the positive-negative sequence component of α β by this 2 group component, submodule is just being carried out Negative sequence component controls respectively；

Wherein q expression formula is as follows:

Q=Q₀+Q_c2cos(2ωt)+Q_s2sin(2ωt)

P₀、Q₀For fundamental active, the idle component of respectively electrical network, Q_c2、Q_s2For idle quadratic component. It is embodied as:

$Q_{c2}=\frac{{2P}_0}{(v_d^{+2}+v_q^{+2}-v_d^{-2}-v_q^{-2})}(v_q^{-}{v}_d^{+}-v_d^{-}{v}_q^{+})$

$Q_{s2}=\frac{-2P_0}{(v_d^{+2}+v_q^{+2}-v_d^{-2}-v_q^{-2})}(v_d^{+}{v}_d^{-}+v_q^{+}{v}_q^{-})$

WhereinWithIt is respectively the positive-negative sequence component of d, q axle component of voltage.

By using the half-bridge MMC submodule voltage control method of the present invention, it is possible to make each submodule open Keeping strokes in pass, which thereby enhances the quality of half-bridge MMC output voltage waveforms.Half-bridge MMC of the present invention The voltage waveform of device output as shown in Figure 4, figure 4, it is seen that voltage waveform is mild, it is little to distort, The quality of power supply is high.

It should be noted that above-mentioned embodiment is only the present invention preferably embodiment, it is impossible to understood For limiting the scope of the invention, without departing under present inventive concept premise, that is the present invention appoints What minor variations and modification belong to protection scope of the present invention.

Claims (6)

1. a half-bridge module multi-level converter submodule voltage control method, comprises the following steps:

A. predetermined DC voltage set-pointWith reactive power set-point

B. DC voltage u is measured_dcWith every cross streams voltage and alternating current, obtain from described every cross streams voltage Take voltage magnitude u_sAnd phase place；Alternating current and phase place are carried out Park Transformation and obtains i_dgAnd i_qg；

C., weight coefficient a is set_ij, by ∑ a_ij(u_dci-u_dcj) value withU is deducted after addition_dc, it is then passed through outer shroud Output after proportional integral link deducts i_dg, its difference after internal ring proportional integral link with u_s/ n is added and obtains u_dgi, wherein u_dciAnd u_dcjIt is respectively in n submodule i-th and the DC capacitor voltage of jth submodule；

D. reactive power is measured,With the output after outer shroud proportional integral link of the difference of described reactive power Deduct i_qg, its difference, through internal ring proportional integral link, obtains u_qgi；

E. to u_dgiAnd u_qgiCarry out Parker inverse transformation and obtain controlled quentity controlled variable u of the i-th submodule_agi, control the i-th son Two switches of module.

2. the half-bridge module multi-level converter submodule voltage control method described in claim 1, its feature It is, described weight coefficient a_ij=(u_dci-u_dcj)/∑(u_dci-u_dcj)。

3. the half-bridge module multi-level converter submodule voltage control method described in claim 1, its feature It is, with each submodule DC capacitor voltage minimum target of capacity volume variance sum:

∑_mina_ij(u_dci-u_dcj)²,

Constraints is:

u_a+u_b+u_c=0,

Determine a that optimal value is corresponding_ijFor weight coefficient.

4. the half-bridge module multi-level converter submodule voltage control method described in claim 1, its feature Being, the parameter of described internal ring proportional integral link is: 1 < proportionality coefficient < 10,0.1 < integral coefficient < 1.

5. the half-bridge module multi-level converter submodule voltage control method described in claim 1, its feature Being, the parameter of described outer shroud proportional integral link is: 0.2 < proportionality coefficient < 1,0.01 < integral coefficient < 0.1.

6. the half-bridge module multi-level converter submodule voltage control method described in claim 1, its feature It is, when electrical network generation unbalanced fault, farther includes:

The alternating voltage of every phase is carried out α β coordinate transform, obtains the α β component of correspondence, passing ratio Integral feedback controls and the feedback control of dual-integration, obtains the first group component；Simultaneously by this component and coefficient q It is multiplied, obtains second component amount；Calculated the positive-negative sequence component of α β by this 2 group component, submodule is entered Row positive-negative sequence component controls respectively；

Wherein q expression formula is as follows:

Q=Q₀+Q_c2cos(2ωt)+Q_s2Sin (2 ω t),

Q₀For the fundamental reactive component of electrical network, Q_c2、Q_s2For idle quadratic component, ω is angular frequency.