CN104022665A - Bridge arm instantaneous current direct control method of modular multilevel converter - Google Patents

Abstract

The invention relates to a bridge arm instantaneous current direct control method of a modular multilevel converter and belongs to the field of a power electronic equipment control technology. The method comprises the following steps: data required by control is acquired and obtained; a bridge arm current reference value is calculated by the use of each obtained current reference value; a bridge arm induction voltage reference value is calculated by the use of a bridge arm inductance value, a control cycle, the calculated bridge arm current reference value and a measured bridge arm current value; a bridge arm output voltage reference value is calculated by the use of an obtained AC port voltage reference value, a DC port voltage reference value and the obtained bridge arm induction voltage reference value; each bridge arm modulation reference wave is calculated by the use of the calculated bridge arm output voltage reference value and measured bridge arm total capacitor voltage; and the generated modulation reference wave is sent to a valve trigger pulse modulator so as to directly control bridge arm instantaneous current. The method has fast control response speed and is not influenced by the transient process. By the method, it is guaranteed that bridge arm overcurrent will not happen to a converter and capacitor overvoltage also will not happen.

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 control technology field, particularly a kind of brachium pontis transient current direct control method of modularization multi-level converter.

Background technology

Modularization multi-level converter (Modular Multilevel Converter, MMC) have easy expansion, meritorious idle can decoupling zero control, outstanding, the switching device small loss and other features of harmonic characterisitic, be a kind of voltage source converter topological structure that has application potential quality most in flexible DC power transmission field.

The main circuit of modularization multi-level converter as shown in Figure 1.This converter 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..In each submodule in brachium pontis, have an electric capacity and several electronic power switch, this electric capacity keeps one to press compared with galvanic current by control in converter running; The type of attachment of electric capacity be can change simultaneously by electronic power switch, thereby 0 voltage or capacitance voltage on submodule port, exported; By the combination of multiple submodules in a brachium pontis, can synthesize required output voltage again.The instantaneous voltage of note converter 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, A phase, the B phase component instantaneous value of inverter inside circulation are respectively i _acir, i _bcir(inner circulation sum is 0, therefore C phase component is-i _acir-i _bcir, not independent, do not list separately), the instantaneous value of six brachium pontis electric currents 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 made up of outer ring controller, interior circular current controller and valve trigger impulse modulator conventionally.The outer ring controller of modularization multi-level converter control system requires (as power output, voltage etc.) to generate port voltage/current reference value and the circulation reference value of converter according to the mode of operation of converter and port identity, conventionally according to the difference of mode of operation, may require control port voltage or port current for exchanging port, can produce respectively and exchange port voltage reference value and exchange port current reference value; Also control port voltage or port current be may require according to mode of operation difference for DC port, DC port voltage reference value and DC port current reference value also produced respectively; In addition outer ring controller all can produce circulation reference value according to current working under each mode of operation, or simple generation perseverance is 0 circulation reference value.It should be noted that, the form of outer ring controller needs and the control ability of interior circular current controller is mated, the ability that for example if interior circular current controller does not have DC port independently to control, outer ring controller just can not be controlled DC port, also just should not generate the coherent reference value of DC port.The current measured value of the reference value that interior circular current controller generates according to outer ring controller and associated electrical tolerance produces the modulation wave signal of six brachium pontis of converter.Valve trigger impulse modulator produces the trigger impulse of each switching device in brachium pontis, the operation of working control 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 interior circular current controller wherein.

The control method of the interior circular current controller of the control system of the existing modularization multi-level converter normally interchange port current to converter and inner loop stream adopts respectively the vector control method under dq rotating coordinate system to control.Amount when stable state under dq coordinate system is all DC quantity, is easily controlled preferably effect; But transient process or three-phase when asymmetric the amount under dq coordinate system also there will be alternating current component, cause controlling effect and decline.Inner circulation adopts dq decoupling zero control conventionally only can realize the inhibition (conventionally selecting to suppress two frequency multiplication negative sequence components) of the specific order component circulation to characteristic frequency in addition, and can not realize the control completely to loop current, make the dynamic process of each brachium pontis total capacitance voltage under transient state or asymmetrical in not controlling state, easily cause the power output capacity of converter limited even because overvoltage/overcurrent is out of service.

Summary of the invention

The object of the invention is the weak point for overcoming existing interior circular current control method, propose a kind of brachium pontis transient current direct control method of modularization multi-level converter.This control method can be in a control cycle by the Current Control of each brachium pontis to reference value, its control response speed is subject to Effect of Transient Component soon and not; Simultaneously this control method is by internal dynamic process that can complete control converter to the control of inner circulation, ensure that converter there will not be brachium pontis overcurrent, and can coordinate suitable capacitance voltage control algolithm to ensure that converter also there will not be electric capacity overvoltage 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, is characterized in that, the method comprises the following steps:

With T _ssecond for control cycle, the brachium pontis transient current of multilevel converter is directly controlled, while control, is carried out 1 at every turn)～5) step;

1) gather and obtain the needed data of control, comprising:

1-1) the current i of six brachium pontis of measurement converter _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; Obtain inner circulation reference value i from outer ring controller _{acir_r}, i _{bcir_r};

1-2), when the interchange port controlling of converter is during in current control mode, measure and exchange port voltage v _a, v _b, v _cas exchanging port voltage reference value v _{a_r}, v _{b_r}, v _{c_r}, obtain and exchange port current reference value i from outer ring controller _{a_r}, i _{b_r}, i _{c_r}; In the time exchanging port controlling in voltage mode control, obtain and exchange port voltage reference value v from outer ring controller _{a_r}, v _{b_r}, v _{c_r}, calculate and exchange port current reference value according to formula (1);

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

The control reference value of this electric parameters of add _ r postfix notation after each electric parameters symbol, suc as formula middle i _arepresent to exchange port A phase current instantaneous value, i _{a_r}represent to exchange port A phase current reference value, the rest may be inferred;

1-3), when the DC port control of converter is during in current control mode, measure 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 control is during 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 each current reference value of obtaining calculate brachium pontis 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) the brachium pontis current reference value and the step 1 that calculate) the brachium pontis 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 interchange 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) the brachium pontis output voltage reference value and the step 1 that calculate) the brachium pontis total capacitance voltage that records calculates each brachium pontis modulation reference ripple according to formula (6):

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

The modulation reference ripple of generation is delivered to valve trigger impulse modulator, so that brachium pontis transient current is directly controlled.

Useful result of the present invention is: the brachium pontis transient current direct control method of the modularization multi-level converter that the present invention proposes, can be in a control cycle by the Current Control of each brachium pontis to reference value, its control response speed is subject to Effect of Transient Component soon and not, the internal dynamic process of the complete control converter of energy, has therefore improved the Performance And Reliability of converter under transient process and asymmetric operating mode simultaneously.

Brief description of the drawings

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

Fig. 2 is that the brachium pontis transient current direct control method of the modularization multi-level converter that proposes of the present invention is in the time that AC network occurs single phase ground fault near converter place and the simulation comparison figure of conventional control method.

Embodiment

The present invention propose a kind of modularization multi-level converter brachium pontis transient current direct control method by reference to the accompanying drawings and embodiment be described in detail as follows:

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

With T _ssecond for control cycle, the brachium pontis transient current of multilevel converter is directly controlled, while control, is carried out 1 at every turn)～5) step;

1) gather and obtain the needed data of control, comprising:

1-1) the current i of six brachium pontis of measurement converter _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; Obtain inner circulation reference value i from outer ring controller _{acir_r}, i _{bcir_r};

1-2), when the interchange port controlling of converter is during in current control mode, measure and exchange port voltage v _a, v _b, v _cas exchanging port voltage reference value v _{a_r}, v _{b_r}, v _{c_r}, obtain and exchange port current reference value i from outer ring controller _{a_r}, i _{b_r}, i _{c_r}; In the time exchanging port controlling in voltage mode control, obtain and exchange port voltage reference value v from outer ring controller _{a_r}, v _{b_r}, v _{c_r}, calculate and exchange port current reference value according to formula (1);

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

The control reference value of this electric parameters of add _ r postfix notation after each electric parameters symbol, suc as formula middle i _arepresent to exchange port A phase current instantaneous value, i _{a_r}represent to exchange port A phase current reference value, the rest may be inferred;

1-3), when the DC port control of converter is during in current control mode, measure 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 control is during 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 each current reference value of obtaining calculate brachium pontis 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) the brachium pontis current reference value and the step 1 that calculate) the brachium pontis 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 interchange 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) the brachium pontis output voltage reference value and the step 1 that calculate) the brachium pontis total capacitance voltage that records calculates each brachium pontis modulation reference ripple according to formula (6):

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

The modulation reference ripple of generation is delivered to valve trigger impulse 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 of determining alternating current and determine direct voltage pattern as example, illustrates the directly actuated process of brachium pontis transient current.

In the present embodiment, the brachium pontis inductance of converter is 3.98mH, with T _s=50 microseconds are that control cycle is directly controlled (T to the brachium pontis transient current of multilevel converter _stypical value in 200 microsecond to 20 microseconds), while control, carry out 1 at every turn)～5) step;

1) gather and obtain the needed data of control, comprising:

1-1) the current i of six brachium pontis of measurement converter _au, i _al, i _bu, i _bl, i _cu, i _cl, record electric current in the once control of the present embodiment be 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, in the once control of the present embodiment, record respectively 9715V, 9494V, 10515V, 9247V, 9295V, 10684V; Obtain inner circulation reference value i from outer ring controller _{acir_r}, i _{bcir_r}, in the once control of the present embodiment, be respectively 7.9A ,-1.0A;

1-2), when the interchange port controlling of converter is during in current control mode (exchanging port controlling in the present embodiment in this pattern), measure and exchange port voltage v _a, v _b, v _cas exchanging port voltage reference value v _{a_r}, v _{b_r}, v _{c_r}, be respectively-440V ,-3395V, 3835V in the once control of the present embodiment; Obtain and exchange port current reference value i from outer ring controller _{a_r}, i _{b_r}, i _{c_r}, in the once control of the present embodiment, be respectively 324.7A ,-193.2A ,-131.5A;

1-3), when the DC port control of converter is during in voltage mode control (in the present embodiment, DC port control is in this pattern), obtain DC port voltage reference value v from outer ring controller _{dc_r}, in the once control of the present embodiment, be 10.00kV, calculate 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 each current reference value of obtaining calculate brachium pontis 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) the brachium pontis current reference value and the step 1 that calculate) the brachium pontis 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 interchange 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) the brachium pontis output voltage reference value and the step 1 that calculate) the brachium pontis total capacitance voltage that records calculates each brachium pontis modulation reference ripple according to formula (6):

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

The modulation reference ripple of generation is delivered to valve trigger impulse modulator, so that brachium pontis transient current is directly controlled.

The brachium pontis transient current direct control method of the modularization multi-level converter proposing by the present invention, can be in a control cycle by the Current Control of each brachium pontis to reference value, its control response speed is subject to Effect of Transient Component soon and not, the internal dynamic process of the complete control converter of energy, has therefore improved the Performance And Reliability of converter under transient process and asymmetric operating mode simultaneously.

Fig. 2 has shown brachium pontis transient current direct control method and the conventional DQ decoupling zero vector control+bis-frequency multiplication circulation inhibition method simulation result in the time that AC network occurs single phase ground fault near converter place of the modularization multi-level converter that the present invention proposes; Converter is in controlling DC port voltage and the control model that exchanges port reactive power, in emulation, DC port has the power of 2MW to inject, there is single phase ground fault in the 0.1s moment in electrical network, fault continues 0.1s, and failure process outer-loop controller requires the maximum positive sequence of output idle so that reactive power support to be provided.Fig. 2 A is wherein the grid voltage waveform using in fault simulation, Fig. 2 B is that the converter under the control of the control method of the present invention's proposition exchanges port current waveform, Fig. 2 C is that the converter under conventional method control exchanges port current waveform, Fig. 2 D is the converter DC port voltage waveform contrast under the present invention control method and the conventional method control that propose, and Fig. 2 E is the converter DC port current waveform contrast under the present invention control method and the conventional method control that propose.Can find out from simulation result, the method institute that the present invention proposes in electric network fault process is influenced less, and the waveform that exchanges port current is good compared with conventional method, can not cause the fluctuation of DC port voltage simultaneously, has better Performance And Reliability.

Claims (1)

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

With T _ssecond for control cycle, the brachium pontis transient current of multilevel converter is directly controlled, while control, is carried out 1 at every turn)～5) step;

1) gather and obtain the needed data of control, comprising:

1-1) the current i of six brachium pontis of measurement converter _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; Obtain inner circulation reference value i from outer ring controller _{acir_r}, i _{bcir_r};

1-2), when the interchange port controlling of converter is during in current control mode, measure and exchange port voltage v _a, v _b, v _cas exchanging port voltage reference value v _{a_r}, v _{b_r}, v _{c_r}, obtain and exchange port current reference value i from outer ring controller _{a_r}, i _{b_r}, i _{c_r}; In the time exchanging port controlling in voltage mode control, obtain and exchange port voltage reference value v from outer ring controller _{a_r}, v _{b_r}, v _{c_r}, calculate and exchange port current reference value according to formula (1);

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

The control reference value of this electric parameters of add _ r postfix notation after each electric parameters symbol, suc as formula middle i _arepresent to exchange port A phase current instantaneous value, i _{a_r}represent to exchange port A phase current reference value, the rest may be inferred;

1-3), when the DC port control of converter is during in current control mode, measure 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 control is during 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 each current reference value of obtaining calculate brachium pontis 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) the brachium pontis current reference value and the step 1 that calculate) the brachium pontis 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 interchange 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) the brachium pontis output voltage reference value and the step 1 that calculate) the brachium pontis total capacitance voltage that records calculates each brachium pontis modulation reference ripple according to formula (6):

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

The modulation reference ripple of generation is delivered to valve trigger impulse modulator, so that brachium pontis transient current is directly controlled.