CN104022665B - A kind of brachium pontis transient current direct control method of modularization multi-level converter - Google Patents

Abstract

The present invention relates to the brachium pontis transient current direct control method of a kind of modularization multi-level converter, belong to power electronic equipment and control technical field, the method includes gathering and obtaining controlling required data, bridge arm current reference value is calculated by each current reference value obtained, by brachium pontis inductance value, control cycle, calculated bridge arm current reference value and the bridge arm current value that records, calculate brachium pontis inductive drop reference value；Brachium pontis output voltage reference value is calculated by the AC port voltage reference value obtained, DC port voltage reference value and the brachium pontis inductive drop reference value obtained；Each brachium pontis modulation reference ripple is obtained with calculated brachium pontis output voltage reference value and the brachium pontis total capacitance voltage calculating recorded；The modulation reference ripple of generation is delivered to valve and triggers pulse-modulator, so that brachium pontis transient current is directly controlled.The method controls fast response time and not by Effect of Transient Component；Ensure that inverter does not have brachium pontis and crosses stream, without electric capacity overvoltage occurs.

Description

A kind of brachium pontis transient current direct control method of modularization multi-level converter

Technical field

The invention belongs to power electronic equipment and control technical field, particularly to the brachium pontis transient current direct control method of a kind of modularization multi-level converter.

Background technology

Modularization multi-level converter (ModularMultilevelConverter, MMC) have easy expansion, active reactive can uneoupled control, harmonic characterisitic be outstanding, switching device small loss and other features, is a kind of voltage source converter topological structure having application potential quality most of flexible direct-current transmission field.

The main circuit of modularization multi-level converter is as shown in Figure 1.This inverter is made up of six brachium pontis, and each brachium pontis comprises a brachium pontis inductance L_armWith one group of submodule, as shown in dotted outline in FIG..Having an electric capacity and several electronic power switch in each submodule in brachium pontis, this electric capacity keeps a relatively galvanic current pressure by control in inverter running；The type of attachment of electric capacity can be changed by electronic power switch, thus exporting 0 voltage or capacitance voltage on submodule port simultaneously；Again through the combination of multiple submodules in a brachium pontis, required output voltage can be synthesized.The instantaneous voltage of note inverter three-phase alternating current port is v_a、v_b、v_c, the current instantaneous value of three-phase alternating current port is i_a、i_b、i_c, the instantaneous voltage of DC port is v_dc, the current instantaneous value of DC port is i_dc, the A phase of inverter inside circulation, B phase component instantaneous value respectively i_acir、i_bcir(internal circulation sum is 0, therefore C phase component is-i_acir-i_bcir, not independent, individually do not list), the instantaneous value of six bridge arm current is i_au、i_al、i_bu、i_bl、i_cu、i_cl, in six brachium pontis, the instantaneous value of each capacitance voltage sum is v_aucap、v_alcap、v_bucap、v_blcap、v_cucap、v_clcap。

The control system of modularization multi-level converter is generally triggered pulse-modulator by outer ring controller, internal ring current controller and valve and forms.Modularization multi-level converter controls the outer ring controller of system and requires that (such as output, voltage etc.) generate port voltage/current reference value and the circulation reference value of inverter according to mode of operation and the port identity of inverter, difference generally according to mode of operation, AC port be may call for controlling port voltage or port current, AC port voltage reference value and AC port current reference value can be produced respectively；DC port be may call for controlling port voltage or port current also according to mode of operation difference, also produce DC port voltage reference value and DC port current reference value respectively；In addition outer ring controller all can produce circulation reference value or the circulation reference value that simple generation perseverance is 0 according to current working under each mode of operation.It should be noted that, the form of outer ring controller needs the control ability with internal ring current controller to mate, if such as internal ring current controller does not have the ability that DC port independently controls, then DC port cannot be controlled by outer ring controller, also just should not generate the relevant reference value of DC port.Reference value that internal ring current controller then generates according to outer ring controller and the current measured value of related electric amount produce the modulation wave signal of six brachium pontis of inverter.Valve triggers pulse-modulator and then produces the triggering pulse of each switching device in brachium pontis, the actual operation controlling main circuit according to the modulation wave signal of each brachium pontis.The control method that the present invention proposes is a kind of control method for internal ring current controller therein.

The vector control method that AC port electric current and the inner loop stream of inverter are usually respectively adopted under dq rotating coordinate system by the control method of the internal ring current controller of the control system of existing modularization multi-level converter is controlled.During stable state, the amount under dq coordinate system is all DC quantity, it is easy to controlled effect preferably；But the amount under dq coordinate system also there will be AC compounent when transient process or asymmetrical three-phase, cause that controlling effect declines.Additionally internal circulation adopts dq uneoupled control to be generally only capable of realizing the suppression (being generally selected suppression two frequency multiplication negative sequence components) of the specific order components circulation to characteristic frequency, and the control completely to loop current can not be realized, the dynamic process of each brachium pontis total capacitance voltage under transient state or asymmetrical is made to be in state of not controlling, it is easy to cause that the power output capacity of inverter is limited even owing to overvoltage/mistake flows out of service.

Summary of the invention

It is an object of the invention to the weak point for overcoming existing internal ring current control method, it is proposed to the brachium pontis transient current direct control method of a kind of modularization multi-level converter.The electric current of each brachium pontis can be controlled to reference value by this control method within a control cycle, and it controls fast response time and not by Effect of Transient Component；This control method by can completely control the internal dynamic process of inverter to the control of internal circulation simultaneously, ensure that inverter does not have brachium pontis and crosses stream, it is possible to coordinate suitable capacitance voltage control algolithm guarantee inverter without electric capacity overvoltage occurs under transient process and asymmetric operating mode.

The brachium pontis transient current direct control method of a kind of modularization multi-level converter that the present invention proposes, it is characterised in that the method comprises the following steps:

With T_sSecond for the control cycle, the brachium pontis transient current of multilevel converter is directly controlled, execution 1 during every secondary control)～5) step；

1) gather and obtain the data required for controlling, including:

1-1) measure the electric current i of six brachium pontis of inverter_au、i_al、i_bu、i_bl、i_cu、i_clTotal capacitance voltage v with six brachium pontis_aucap、v_alcap、v_bucap、v_blcap、v_cucap、v_clcap；Internal circulation reference value i is obtained from outer ring controller_{acir_r}、i_{bcir_r}；

1-2) when the AC port of inverter controls to be in current control mode, measure and obtain AC port voltage v_a、v_b、v_cAs AC port voltage reference value v_{a_r}、v_{b_r}、v_{c_r}, obtain AC port current reference value i from outer ring controller_{a_r}、i_{b_r}、i_{c_r}；When AC port controls to be in voltage mode control, obtain AC port voltage reference value v from outer ring controller_{a_r}、v_{b_r}、v_{c_r}, calculate AC port current reference value according to formula (1)；

$\left.\begin{array}{c}{i}_{a\_r}=i_{\mathrm{al}}-i_{\mathrm{au}}\\ i_{b\_r}=i_{\mathrm{bl}}-i_{\mathrm{bu}}\\ i_{c\_r}=i_{\mathrm{cl}}-i_{\mathrm{cu}}\end{array}\right\}---\left(1\right)$

_ control the reference value of r this electric parameters of postfix notation, i in formula is added after each electric parameters symbol_aRepresent AC port A phase current instantaneous value, then i_{a_r}Representing AC port A phase-current reference value, the rest may be inferred；

1-3) when the DC port of inverter controls to be in current control mode, measure and obtain DC port voltage v_dcAs DC port voltage reference value v_{dc_r}, obtain DC port current reference value i from outer ring controller_{dc_r}；When DC port controls to be in voltage mode control, obtain DC port voltage reference value v from outer ring controller_{dc_r}, calculate DC port current reference value according to formula (2)；

i_{dc_r}=i_au+i_bu+i_cu(2)

2) by step 1) in obtain each current reference value calculate bridge arm current reference value i according to relational expression (3)_{au_r}、i_{al_r}、i_{bu_r}、i_{bl_r}、i_{cu_r}、i_{cl_r}:

$\left[\begin{array}{c}{i}_{\mathrm{au}\_r}\\ i_{\mathrm{al}\_r}\\ i_{\mathrm{bu}\_r}\\ i_{\mathrm{bl}\_r}\\ i_{\mathrm{cu}\_r}\\ i_{\mathrm{cl}\_r}\end{array}\right]=\left[\begin{array}{cccccc}-0.5& 0& 0& 1/3& 1& 0\\ 0.5& 0& 0& 1/3& 1& 0\\ 0& -0.5& 0& 1/3& 0& 1\\ 0& 0.5& 0& 1/3& 0& 1\\ 0& 0& -0.5& 1/3& -1& -1\\ 0& 0& 0.5& 1/3& -1& -1\end{array}\right]\left[\begin{array}{c}{i}_{a\_r}\\ i_{b\_r}\\ i_{c\_r}\\ i_{\mathrm{dc}\_r}\\ i_{\mathrm{acir}\_r}\\ i_{\mathrm{bcir}\_r}\end{array}\right]---\left(3\right)$

3) with brachium pontis inductance value L_arm, control cycle T_s, step 2) calculated bridge arm current reference value and step 1) the bridge arm current value that records, calculate brachium pontis inductive drop reference value according to formula (4):

$\left.\begin{array}{c}{v}_{\mathrm{aul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{au}\_r}-i_{\mathrm{au}})\\ v_{\mathrm{all}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{al}\_r}-i_{\mathrm{al}})\\ v_{\mathrm{bul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bu}\_r}-i_{\mathrm{bu}})\\ v_{\mathrm{bll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bl}\_r}-i_{\mathrm{bl}})\\ v_{\mathrm{cul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cu}\_r}-i_{\mathrm{cu}})\\ v_{\mathrm{cll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cl}\_r}-i_{\mathrm{cl}})\end{array}\right\}---\left(4\right)$

4) by step 1) the AC port voltage reference value, DC port voltage reference value and the step 3 that obtain) the brachium pontis inductive drop reference value that obtains calculates brachium pontis output voltage reference value according to formula (5):

$\left.\begin{array}{c}{v}_{\mathrm{au}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{aul}\_r}-v_{a\_r}\\ v_{\mathrm{al}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{all}\_r}+v_{a\_r}\\ v_{\mathrm{bu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bul}\_r}-v_{b\_r}\\ v_{\mathrm{bl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bll}\_r}+v_{b\_r}\\ v_{\mathrm{cu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cul}\_r}-v_{c\_r}\\ v_{\mathrm{cl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cll}\_r}+v_{c\_r}\end{array}\right\}---\left(5\right)$

5) by step 4) calculated brachium pontis output voltage reference value and step 1) the brachium pontis total capacitance voltage that records calculates according to formula (6) and obtains each brachium pontis modulation reference ripple:

$\left.\begin{array}{c}{d}_{\mathrm{au}}=v_{\mathrm{au}\_r}/v_{\mathrm{aucap}}\\ d_{\mathrm{al}}=v_{\mathrm{al}\_r}/v_{\mathrm{alcap}}\\ d_{\mathrm{bu}}=v_{\mathrm{bu}\_r}/v_{\mathrm{bucap}}\\ d_{\mathrm{bl}}=v_{\mathrm{bl}\_r}/v_{\mathrm{blcap}}\\ d_{\mathrm{cu}}=v_{\mathrm{cu}\_r}/v_{\mathrm{cucap}}\\ d_{\mathrm{cl}}=v_{\mathrm{cl}\_r}/v_{\mathrm{clcap}}\end{array}\right\}---\left(6\right)$

The modulation reference ripple of generation is delivered to valve and triggers pulse-modulator, so that brachium pontis transient current is directly controlled.

The beneficial outcomes of the present invention is: the brachium pontis transient current direct control method of the modularization multi-level converter that the present invention proposes, within a control cycle, the electric current of each brachium pontis can be controlled to reference value, it controls fast response time and not by Effect of Transient Component, can completely control the internal dynamic process of inverter simultaneously, therefore improve inverter Performance And Reliability under transient process and asymmetric operating mode.

Accompanying drawing explanation

Fig. 1 is the main circuit diagram of the modularization multi-level converter that the inventive method relates to.

Fig. 2 be the brachium pontis transient current direct control method of the modularization multi-level converter that the present invention proposes when there is singlephase earth fault near inverter place in AC network with the simulation comparison figure of conventional control methods.

Detailed description of the invention

The brachium pontis transient current direct control method of a kind of modularization multi-level converter that the present invention proposes describes in detail as follows in conjunction with drawings and Examples:

The present invention proposes the brachium pontis transient current direct control method of a kind of modularization multi-level converter, and the method comprises the following steps:

With T_sSecond for the control cycle, the brachium pontis transient current of multilevel converter is directly controlled, execution 1 during every secondary control)～5) step；

1) gather and obtain the data required for controlling, including:

1-1) measure the electric current i of six brachium pontis of inverter_au、i_al、i_bu、i_bl、i_cu、i_clTotal capacitance voltage v with six brachium pontis_aucap、v_alcap、v_bucap、v_blcap、v_cucap、v_clcap；Internal circulation reference value i is obtained from outer ring controller_{acir_r}、i_{bcir_r}；

1-2) when the AC port of inverter controls to be in current control mode, measure and obtain AC port voltage v_a、v_b、v_cAs AC port voltage reference value v_{a_r}、v_{b_r}、v_{c_r}, obtain AC port current reference value i from outer ring controller_{a_r}、i_{b_r}、i_{c_r}；When AC port controls to be in voltage mode control, obtain AC port voltage reference value v from outer ring controller_{a_r}、v_{b_r}、v_{c_r}, calculate AC port current reference value according to formula (1)；

$\left.\begin{array}{c}{i}_{a\_r}=i_{\mathrm{al}}-i_{\mathrm{au}}\\ i_{b\_r}=i_{\mathrm{bl}}-i_{\mathrm{bu}}\\ i_{c\_r}=i_{\mathrm{cl}}-i_{\mathrm{cu}}\end{array}\right\}---\left(1\right)$

_ control the reference value of r this electric parameters of postfix notation, i in formula is added after each electric parameters symbol_aRepresent AC port A phase current instantaneous value, then i_{a_r}Representing AC port A phase-current reference value, the rest may be inferred；

1-3) when the DC port of inverter controls to be in current control mode, measure and obtain DC port voltage v_dcAs DC port voltage reference value v_{dc_r}, obtain DC port current reference value i from outer ring controller_{dc_r}；When DC port controls to be in voltage mode control, obtain DC port voltage reference value v from outer ring controller_{dc_r}, calculate DC port current reference value according to formula (2)；

i_{dc_r}=i_au+i_bu+i_cu(2)

2) by step 1) in obtain each current reference value calculate bridge arm current reference value i according to relational expression (3)_{au_r}、i_{al_r}、i_{bu_r}、i_{bl_r}、i_{cu_r}、i_{cl_r}:

$\left[\begin{array}{c}{i}_{\mathrm{au}\_r}\\ i_{\mathrm{al}\_r}\\ i_{\mathrm{bu}\_r}\\ i_{\mathrm{bl}\_r}\\ i_{\mathrm{cu}\_r}\\ i_{\mathrm{cl}\_r}\end{array}\right]=\left[\begin{array}{cccccc}-0.5& 0& 0& 1/3& 1& 0\\ 0.5& 0& 0& 1/3& 1& 0\\ 0& -0.5& 0& 1/3& 0& 1\\ 0& 0.5& 0& 1/3& 0& 1\\ 0& 0& -0.5& 1/3& -1& -1\\ 0& 0& 0.5& 1/3& -1& -1\end{array}\right]\left[\begin{array}{c}{i}_{a\_r}\\ i_{b\_r}\\ i_{c\_r}\\ i_{\mathrm{dc}\_r}\\ i_{\mathrm{acir}\_r}\\ i_{\mathrm{bcir}\_r}\end{array}\right]---\left(3\right)$

3) with brachium pontis inductance value L_arm, control cycle T_s, step 2) calculated bridge arm current reference value and step 1) the bridge arm current value that records, calculate brachium pontis inductive drop reference value according to formula (4):

$\left.\begin{array}{c}{v}_{\mathrm{aul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{au}\_r}-i_{\mathrm{au}})\\ v_{\mathrm{all}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{al}\_r}-i_{\mathrm{al}})\\ v_{\mathrm{bul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bu}\_r}-i_{\mathrm{bu}})\\ v_{\mathrm{bll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bl}\_r}-i_{\mathrm{bl}})\\ v_{\mathrm{cul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cu}\_r}-i_{\mathrm{cu}})\\ v_{\mathrm{cll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cl}\_r}-i_{\mathrm{cl}})\end{array}\right\}---\left(4\right)$

4) by step 1) the AC port voltage reference value, DC port voltage reference value and the step 3 that obtain) the brachium pontis inductive drop reference value that obtains calculates brachium pontis output voltage reference value according to formula (5):

$\left.\begin{array}{c}{v}_{\mathrm{au}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{aul}\_r}-v_{a\_r}\\ v_{\mathrm{al}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{all}\_r}+v_{a\_r}\\ v_{\mathrm{bu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bul}\_r}-v_{b\_r}\\ v_{\mathrm{bl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bll}\_r}+v_{b\_r}\\ v_{\mathrm{cu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cul}\_r}-v_{c\_r}\\ v_{\mathrm{cl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cll}\_r}+v_{c\_r}\end{array}\right\}---\left(5\right)$

5) by step 4) calculated brachium pontis output voltage reference value and step 1) the brachium pontis total capacitance voltage that records calculates according to formula (6) and obtains each brachium pontis modulation reference ripple:

$\left.\begin{array}{c}{d}_{\mathrm{au}}=v_{\mathrm{au}\_r}/v_{\mathrm{aucap}}\\ d_{\mathrm{al}}=v_{\mathrm{al}\_r}/v_{\mathrm{alcap}}\\ d_{\mathrm{bu}}=v_{\mathrm{bu}\_r}/v_{\mathrm{bucap}}\\ d_{\mathrm{bl}}=v_{\mathrm{bl}\_r}/v_{\mathrm{blcap}}\\ d_{\mathrm{cu}}=v_{\mathrm{cu}\_r}/v_{\mathrm{cucap}}\\ d_{\mathrm{cl}}=v_{\mathrm{cl}\_r}/v_{\mathrm{clcap}}\end{array}\right\}---\left(6\right)$

The modulation reference ripple of generation is delivered to valve and triggers pulse-modulator, so that brachium pontis transient current is directly controlled.

The embodiment of the inventive method, to be operated in the modularization multi-level converter determined alternating current Yu determine DC voltage pattern, illustrates the directly actuated process of brachium pontis transient current.

In the present embodiment, the brachium pontis inductance of inverter is 3.98mH, with T_s=50 microseconds are that the control cycle brachium pontis transient current to multilevel converter carries out directly control (T_sTypical value in 200 microseconds to 20 microseconds), during every secondary control perform 1)～5) step；

1) gather and obtain the data required for controlling, including:

1-1) measure the electric current i of six brachium pontis of inverter_au、i_al、i_bu、i_bl、i_cu、i_cl, a secondary control of the present embodiment records electric current respectively-154.4A, 169.4A, 100.5A ,-101.5A, 54.5A ,-67.3A；Measure the total capacitance voltage v of six brachium pontis_aucap、v_alcap、v_bucap、v_blcap、v_cucap、v_clcap, a secondary control of the present embodiment records 9715V, 9494V, 10515V, 9247V, 9295V, 10684V respectively；Internal circulation reference value i is obtained from outer ring controller_{acir_r}、i_{bcir_r}, respectively 7.9A ,-1.0A in a secondary control of the present embodiment；

1-2) when the AC port of inverter controls to be in current control mode (in the present embodiment, AC port controls to be in this pattern), measure and obtain AC port voltage v_a、v_b、v_cAs AC port voltage reference value v_{a_r}、v_{b_r}、v_{c_r}, in a secondary control of the present embodiment respectively-440V ,-3395V, 3835V；AC port current reference value i is obtained from outer ring controller_{a_r}、i_{b_r}、i_{c_r}, in a secondary control of the present embodiment respectively 324.7A ,-193.2A ,-131.5A；

1-3) when the DC port of inverter controls to be in voltage mode control (in the present embodiment, DC port controls to be in this pattern), DC port voltage reference value v is obtained from outer ring controller_{dc_r}, a secondary control of the present embodiment is 10.00kV, calculates DC port current reference value i according to formula (2)_{dc_r}=-154.4+100.5+54.5=0.6A；

2) by step 1) in obtain each current reference value calculate bridge arm current reference value i according to relational expression (3)_{au_r}、i_{al_r}、i_{bu_r}、i_{bl_r}、i_{cu_r}、i_{cl_r}:

$\left[\begin{array}{c}{i}_{\mathrm{au}\_r}\\ i_{\mathrm{al}\_r}\\ i_{\mathrm{bu}\_r}\\ i_{\mathrm{bl}\_r}\\ i_{\mathrm{cu}\_r}\\ i_{\mathrm{cl}\_r}\end{array}\right]=\left[\begin{array}{cccccc}-0.5& 0& 0& 1/3& 1& 0\\ 0.5& 0& 0& 1/3& 1& 0\\ 0& -0.5& 0& 1/3& 0& 1\\ 0& 0.5& 0& 1/3& 0& 1\\ 0& 0& -0.5& 1/3& -1& -1\\ 0& 0& 0.5& 1/3& -1& -1\end{array}\right]\left[\begin{array}{c}324.7\\ -193.2\\ -131.5\\ 0.6\\ 7.9\\ -1.0\end{array}\right]=\left[\begin{array}{c}-154.3\\ 170.5\\ 95.8\\ -97.4\\ 59.0\\ -72.5\end{array}\right]$

3) with brachium pontis inductance value L_arm, control cycle T_s, step 2) calculated bridge arm current reference value and step 1) the bridge arm current value that records, calculate brachium pontis inductive drop reference value according to formula (4):

$\left.\begin{array}{c}{v}_{\mathrm{aul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{au}\_r}-i_{\mathrm{au}})=\frac{3.98E-3}{50E-6}(-154.3+154.4)=8V\\ v_{\mathrm{all}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{al}\_r}-i_{\mathrm{al}})=\frac{3.98E-3}{50E-6}(170.5-169.4)=87V\\ v_{\mathrm{bul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bu}\_r}-i_{\mathrm{bu}})=\frac{3.98E-3}{50E-6}(95.8-100.5)=-374V\\ v_{\mathrm{bll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{bl}\_r}-i_{\mathrm{bl}})=\frac{3.98E-3}{50E-6}=(-97.4+101.5)=326V\\ v_{\mathrm{cul}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cu}\_r}-i_{\mathrm{cu}})=\frac{3.98E-3}{50E-6}(59.0-54.5)=358V\\ v_{\mathrm{cll}\_r}=\frac{L_{\mathrm{arm}}}{T_s}(i_{\mathrm{cl}\_r}-i_{\mathrm{cl}})=\frac{3.98E-3}{50E-6}(-72.5+67.3)=-414V\end{array}\right\}$

4) by step 1) the AC port voltage reference value, DC port voltage reference value and the step 3 that obtain) the brachium pontis inductive drop reference value that obtains calculates brachium pontis output voltage reference value according to formula (5):

$\left.\begin{array}{c}{v}_{\mathrm{au}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{aul}\_r}-v_{a\_r}=0.5\×10000-8-(-440)=5432V\\ v_{\mathrm{al}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{all}\_r}+v_{a\_r}=0.5\×10000-87+(-440)=4473V\\ v_{\mathrm{bu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bul}\_r}-v_{b\_r}=0.5\×10000-(-374)-(-3395)=8769V\\ v_{\mathrm{bl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{bll}\_r}+v_{b\_r}=0.5\×10000-326+(-3395)=1279V\\ v_{\mathrm{cu}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cul}\_r}-v_{c\_r}=0.5\×10000-358-3835=807V\\ v_{\mathrm{cl}\_r}=0.5v_{\mathrm{dc}\_r}-v_{\mathrm{cll}\_r}+v_{c\_r}=0.5\×10000-(-414)+3835=9249V\end{array}\right\}$

5) by step 4) calculated brachium pontis output voltage reference value and step 1) the brachium pontis total capacitance voltage that records calculates according to formula (6) and obtains each brachium pontis modulation reference ripple:

$\left.\begin{array}{c}{d}_{\mathrm{au}}=v_{\mathrm{au}\_r}/v_{\mathrm{aucap}}=5432/9715=0.5591\\ d_{\mathrm{al}}=v_{\mathrm{al}\_r}/v_{\mathrm{alcap}}=4473/9494=0.4711\\ d_{\mathrm{bu}}=v_{\mathrm{bu}\_r}/v_{\mathrm{bucap}}=8769/10515=0.8339\\ d_{\mathrm{bl}}=v_{\mathrm{bl}\_r}/v_{\mathrm{blcap}}=1279/9247=0.1383\\ d_{\mathrm{cu}}=v_{\mathrm{cu}\_r}/v_{\mathrm{cucap}}=807/9295=0.0868\\ d_{\mathrm{cl}}=v_{\mathrm{cl}\_r}/v_{\mathrm{clcap}}=9249/10684=0.8657\end{array}\right\}$

The modulation reference ripple of generation is delivered to valve and triggers pulse-modulator, so that brachium pontis transient current is directly controlled.

By the brachium pontis transient current direct control method of the modularization multi-level converter that the present invention proposes, within a control cycle, the electric current of each brachium pontis can be controlled to reference value, it controls fast response time and not by Effect of Transient Component, can completely control the internal dynamic process of inverter simultaneously, therefore improve inverter Performance And Reliability under transient process and asymmetric operating mode.

Fig. 2 illustrates brachium pontis transient current direct control method and conventional DQ decoupling vector controlled+two frequency multiplication circulation inhibition method simulation result when singlephase earth fault occurs near inverter place in AC network of the modularization multi-level converter that the present invention proposes；Inverter is in the control model controlling DC port voltage and AC port reactive power, in emulation, DC port has the power of 2MW to inject, there is singlephase earth fault in the 0.1s moment in electrical network, fault continues 0.1s, and it is idle to provide reactive power support that failure process outer-loop controller requires to export maximum positive sequence.Fig. 2 A therein is the grid voltage waveform used in fault simulation, Fig. 2 B is the inverter AC port current waveform under the control of the control method of present invention proposition, Fig. 2 C is the inverter AC port current waveform under conventional method control, Fig. 2 D is the control method that proposes of the present invention and conventional method controls lower inverter DC port voltage waveform contrast, Fig. 2 E is the control method that proposes of the present invention and conventional method control under inverter DC port current waveform contrast.From simulation result it can be seen that the method institute that the present invention proposes electric network fault process is impacted less, the more conventional method of waveform of AC port electric current is good, is not result in the fluctuation of DC port voltage simultaneously, has better performance and reliability.

Claims (1)

1. the brachium pontis transient current direct control method of a modularization multi-level converter, it is characterised in that the method comprises the following steps:

With T_sSecond for the control cycle, the brachium pontis transient current of multilevel converter is directly controlled, execution 1 during every secondary control)～5) step；

1) gather and obtain the data required for controlling, including:

1-1) measure the electric current i of six brachium pontis of inverter_au、i_al、i_bu、i_bl、i_cu、i_clTotal capacitance voltage v with six brachium pontis_aucap、v_alcap、v_bucap、v_blcap、v_cucap、v_clcap；Internal circulation reference value i is obtained from outer ring controller_{acir_r}、i_{bcir_r}；

1-2) when the AC port of inverter controls to be in current control mode, measure and obtain AC port voltage v_a、v_b、v_cAs AC port voltage reference value v_{a_r}、v_{b_r}、v_{c_r}, obtain AC port current reference value i from outer ring controller_{a_r}、i_{b_r}、i_{c_r}；When AC port controls to be in voltage mode control, obtain AC port voltage reference value v from outer ring controller_{a_r}、v_{b_r}、v_{c_r}, calculate AC port current reference value according to formula (1)；

$\left.\begin{array}{c}{i}_{a\_r}=i_{al}-i_{au}\\ i_{b\_r}=i_{bl}-i_{bu}\\ i_{c\_r}=i_{cl}-i_{cu}\end{array}\right\}---\left(1\right)$

_ control the reference value of r this electric parameters of postfix notation, i in formula is added after each electric parameters symbol_{a_r}Representing AC port A phase-current reference value, the rest may be inferred；

1-3) when the DC port of inverter controls to be in current control mode, measure and obtain DC port voltage v_dcAs DC port voltage reference value v_{dc_r}, obtain DC port current reference value i from outer ring controller_{dc_r}；When DC port controls to be in voltage mode control, obtain DC port voltage reference value v from outer ring controller_{dc_r}, calculate DC port current reference value according to formula (2)；

i_{dc_r}=i_au+i_bu+i_cu(2)

2) by step 1) in obtain each current reference value calculate bridge arm current reference value i according to relational expression (3)_{au_r}、i_{al_r}、i_{bu_r}、i_{bl_r}、i_{cu_r}、i_{cl_r}:

$\left[\begin{array}{c}{i}_{au\_r}\\ i_{al\_r}\\ i_{bu\_r}\\ i_{bl\_r}\\ i_{cu\_r}\\ i_{cl\_r}\end{array}\right]=\left[\begin{array}{cccccc}-0.5& 0& 0& 1/3& 1& 0\\ 0.5& 0& 0& 1/3& 1& 0\\ 0& -0.5& 0& 1/3& 0& 1\\ 0& 0.5& 0& 1/3& 0& 1\\ 0& 0& -0.5& 1/3& -1& -1\\ 0& 0& 0.5& 1/3& -1& -1\end{array}\right]\left[\begin{array}{c}{i}_{a\_r}\\ i_{b\_r}\\ i_{c\_r}\\ i_{dc\_r}\\ i_{acir\_r}\\ i_{bcir\_r}\end{array}\right]---\left(3\right)$

3) with brachium pontis inductance value L_arm, control cycle T_s, step 2) calculated bridge arm current reference value and step 1) the bridge arm current value that records, calculate brachium pontis inductive drop reference value according to formula (4):

$\left.\begin{array}{c}{v}_{aul\_r}=\frac{L_{arm}}{T_s}\left(i_{au\_r}-i_{au}\right)\\ v_{all\_r}=\frac{L_{arm}}{T_s}\left(i_{al\_r}-i_{al}\right)\\ v_{bul\_r}=\frac{L_{arm}}{T_s}\left(i_{bu\_r}-i_{bu}\right)\\ v_{bll\_r}=\frac{L_{arm}}{T_s}\left(i_{bl\_r}-i_{bl}\right)\\ v_{cul\_r}=\frac{L_{arm}}{T_s}\left(i_{cu\_r}-i_{cu}\right)\\ v_{cll\_r}=\frac{L_{arm}}{T_s}\left(i_{cl\_r}-i_{cl}\right)\end{array}\right\}---\left(4\right)$

4) by step 1) the AC port voltage reference value, DC port voltage reference value and the step 3 that obtain) the brachium pontis inductive drop reference value that obtains calculates brachium pontis output voltage reference value according to formula (5):

$\left.\begin{array}{c}{v}_{au\_r}=0.5v_{dc\_r}-v_{aul\_r}-v_{a\_r}\\ v_{al\_r}=0.5v_{dc\_r}-v_{all\_r}+v_{a\_r}\\ v_{bu\_r}=0.5v_{dc\_r}-v_{bul\_r}-v_{b\_r}\\ v_{bl\_r}=0.5v_{dc\_r}-v_{bll\_r}+v_{b\_r}\\ v_{cu\_r}=0.5v_{dc\_r}-v_{cul\_r}-v_{c\_r}\\ v_{cl\_r}=0.5v_{dc\_r}-v_{cll\_r}+v_{c\_r}\end{array}\right\}---\left(5\right)$

5) by step 4) calculated brachium pontis output voltage reference value and step 1) the brachium pontis total capacitance voltage that records calculates according to formula (6) and obtains each brachium pontis modulation reference ripple:

$\left.\begin{array}{c}{d}_{au}=v_{au\_r}/v_{aucap}\\ d_{al}=v_{al\_r}/v_{alcap}\\ d_{bu}=v_{bu\_r}/v_{bucap}\\ d_{bl}=v_{bl\_r}/v_{blcap}\\ d_{cu}=v_{cu\_r}/v_{cucap}\\ d_{cl}=v_{cl\_r}/v_{clcap}\end{array}\right\}---\left(6\right)$

The modulation reference ripple of generation is delivered to valve and triggers pulse-modulator, so that brachium pontis transient current is directly controlled.