CN102170243B - Negative-sequence-current-based control method of conversion chain average direct voltage - Google Patents

Abstract

The invention particularly relates to a negative-sequence-current-based control method of conversion chain average direct voltage. The method comprises the following steps: comparing the average direct voltage of any two phases of three phases of conversion chain with the average value of direct current of all chain nodes to obtain average direct voltage deviation of the two phases of conversion chain, and processing by a PI (Proportional Integral) controller to obtain the active power deviation of the corresponding phase of conversion chain; combining the active power deviation and the effective value of alternating current side system voltage to obtain the negative-sequence current component instruction of the three phases of conversion chain through the negative-sequence current instruction calculation; transforming the of three-phase negative-sequence current component instruction into dq axis component of negative-sequence current instruction through Park Transform; obtaining the dq axis component of negative-sequence modulation wave voltage through negative-sequence current decoupling control; then carrying out inverse Park Transformation to obtain the reference value of the three-phase negative-sequence modulation wave voltage; and controlling the output of a converter to form a closed-loop control. The method can effectively solve the problem of conversion chain average direct voltage unbalance and has the characteristics of excellent control performance and wide application range.

Description

A kind of control method of the change of current chain mean direct voltage based on negative-sequence current

Technical field

The invention belongs to power electronic equipment control technology field, be specifically related to a kind of control method of the change of current chain mean direct voltage based on negative-sequence current, can be applicable to the control to the direct voltage of chain-type inverter.

Background technology

Chain-type inverter is widely used in engineering, it consists of a plurality of single-phase change of current chains, each single-phase change of current chain consists of at least one single-phase module (being the cascade module 1......n in Fig. 1), each single-phase module comprises at least one chain link, between chain link and chain link, can be connected by serial or parallel connection, each chain link comprises H bridge type voltage source converter.

Chain-type inverter has plurality of advantages, can realize independent minute phase control, is conducive to the alternate equilibrium problem of resolution system.The basic cell structure of its all-links is identical, can realize modularized design, is convenient to dilatation and maintenance, and has avoided using because of the direct connection in series-parallel of switching device the problem producing.Chain-type inverter adopts common transformer connecting system, and the problem of having avoided multiplex transformer to bring, has reduced floor space, has reduced installation cost.In addition, the harmonic wave of the output of many level chain-type inverter can be ignored, and does not need filter.

Yet the problem that chain structure causes is that DC capacitor voltage fluctuates acutely and DC capacitor voltage unbalance, coordinates to control difficulty larger.Voltage balance control is set about from energy point of view conventionally, controls the energy balance between change of current interchain and chain link, and control capacittance shunt loss and to straighten stream voltage control method transient response slower, limited adjustment range and loss are larger.For the dc-voltage balance problem of chain-type inverter, in engineering, conventionally adopt three grades of DC voltage controls, the first order is that overall mean direct voltage is controlled, the stable problem of the whole DC voltage of solving device; The second level is controlled as change of current chain mean direct voltage and is controlled, and realizes alternate dc-voltage balance; The third level is controlled as chain link DC voltage control, realizes chain link balance.Above-mentioned DC voltage balance control method can consist of the current closed-loop of id and iq pi regulator, make it on d axle and q direction of principal axis, keep constant, by controlling the meritorious and reactive power of chain-type inverter exchange, reaches balancing capacitance voltage object.If but controlled quentity controlled variable or feedback quantity select improper speed and the precision controlled of causing cannot meet actual requirement while realizing three grades of DC control.Wherein can second level change of current chain mean direct voltage be controlled decision converter and be realized three-phase equilibrium, and affect effect and speed that the third level is controlled.Adopt reactive current feedback quantity to carry out three-phase equilibrium control, control principle is indefinite, controls DeGrain.Described content proposes the change of current chain mean direct voltage control strategy based on negative-sequence current, has control with clearly defined objective, and fast response time, controls the advantages such as respond well.

Summary of the invention

In order to overcome the above-mentioned defect of prior art, the control method of a kind of change of current chain mean direct voltage based on negative-sequence current of proposition of the present invention, this control method is by regulating the power deviation of any two-phase to reach the unbalanced object of each phase change of current chain mean direct voltage of compensation.

The control method of the change of current chain mean direct voltage based on negative-sequence current of the present invention is achieved through the following technical solutions:

A kind of control method of the change of current chain mean direct voltage based on negative-sequence current, it is characterized in that: this control method is that the mean direct voltage of any two-phase change of current chain in three-phase change of current chain is compared with the DC voltage average value of all chain links and obtained the mean direct voltage deviation of two-phase change of current chain, through proportional and integral controller, the mean direct voltage deviation of two-phase change of current chain is obtained to the active power deviation of corresponding phase change of current chain; Active power deviation through negative current instructions operation link, obtains the negative-sequence current component instruction of three-phase change of current chain in conjunction with the AC system voltage effective value of measuring gained; Through Park Transformation link, the dq axle component that is negative current instructions by the instruction map of three-phase negative/positive current component; Then by negative-sequence current decoupling zero controlling unit, obtain the dq axle component of negative phase-sequence modulating wave voltage, carry out subsequently Parker inverse transformation and obtain three-phase negative/positive modulating wave voltage reference value, control current transformer output and form closed-loop control.

Control method of the present invention has the following advantages:

1) according to any two-phase DC voltage average value bias adjustment negative-sequence current, can guarantee that three phase power meets the demands;

2) adopt the chain type STATCOM control principle of this kind of control method simply clear and definite, control performance is good;

3) described control method is applicable to adopt other FACTS devices of chain type H bridge converter, and the scope of application is broad;

4) described control method has solved the unbalanced problem of change of current chain mean direct voltage effectively, has very strong engineering practical value.

Accompanying drawing explanation

Fig. 1 is Cascade H bridge chain type STATCOM main circuit topological structure figure;

Fig. 2 is chain-type inverter mean direct voltage control block diagram of the present invention;

Fig. 3 is the block diagram of realizing of chain-type inverter negative current instructions computing;

Fig. 4 is abc-dq Park Transformation schematic diagram;

Fig. 5 is the block diagram of realizing of chain-type inverter negative-sequence current decoupling zero control.

Embodiment

Below in conjunction with accompanying drawing, control method of the present invention is described in further detail.

System voltage in described content, link direct voltage, converter output current obtains by measurement links.When electric parameters signal is used for realizing control target, filtering processing and reduction have been carried out.

For the operation principle of the control method of the clearer elaboration change of current chain mean direct voltage based on negative-sequence current of the present invention, now take Cascade H bridge type STATCOM inverter system and carry out analytic explanation as example, this STATCOM structure is as shown in Figure 1.Every cascade connection type single-phase inverter that has independent direct current electric capacity by N is in series, and three-phase change of current chain adopts wye connection, and whether current transformer neutral point n ground connection does not impact control method of the present invention.

Accompanying drawing 2 is the chain-type inverter mean direct voltage control method overall schematic based on negative-sequence current of the present invention.The control method that the present invention is based on the change of current chain mean direct voltage of negative-sequence current is: by the mean direct voltage V of A, B two-phase change of current chain in three-phase change of current chain _{dc_ave_a}, V _{dc_ave_b}dC voltage average value V with all chain links _{dc_ave}subtract each other the departure obtaining, passing ratio-integral controller, can obtain the active power deviation of A, B two-phase change of current chain active power deviation with AC system voltage effective value U _rMSthrough negative current instructions operation link, obtain the negative current instructions of ABC three-phase change of current chain three-phase negative/positive current-order is carried out to the dq axle component that Park Transformation is converted into three-phase negative/positive current-order by negative-sequence current decoupling zero controlling unit, obtain subsequently the dq axle component of negative phase-sequence modulating wave voltage the dq axle component of negative phase-sequence modulating wave voltage through Parker inverse transformation, obtain three-phase negative/positive modulating wave voltage reference value control converter and export to realize closed-loop control.In figure, i _nd, i _nq, e _nd, e _nqbe respectively output current of converter and the AC system voltage dq component value after Parker inverse transformation, be respectively the value of negative phase-sequence modulating wave voltage under dq coordinate system, be respectively the value of negative phase-sequence modulating wave voltage under α β rest frame.

Fig. 3 has provided the block diagram of realizing of negative current instructions operation link in Fig. 2, negative current instructions computing block diagram when Fig. 3 (a) is sinusoidal expression for system voltage, negative current instructions computing block diagram when Fig. 3 (b) is cosine expression formula for system voltage, negative current instructions computing can be as required according to sinusoidal expression or in advance expression formula carry out, concrete methods of realizing is as follows:

With reference to the accompanying drawings 1, set the voltage U of H bridge type STATCOM converter place system _sA, U _sB, U _sCfor:

$\left\{\begin{array}{c}{U}_{\mathrm{sA}}=\sqrt{2}{U}_{\mathrm{RMS}}\sin \left(\mathrm{\ωt}\right)\\ U_{\mathrm{sB}}=\sqrt{2}{U}_{\mathrm{RMS}}\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})\\ U_{\mathrm{sC}}=\sqrt{2}{U}_{\mathrm{RMS}}\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\end{array}\right.---(1-1)$

Wherein ω is first-harmonic angular frequency, and t is the time, U _rMSfor AC system voltage effective value.Suppose neutral point voltage u _n=0, the not impact of method considering zero sequence voltage, the electric current of inflow device consists of forward-order current and negative-sequence current, supposes the current i of inflow device (being the H bridge type STATCOM converter in this example) _a, i _b, i _cfor:

$\left\{\begin{array}{c}{i}_A=\sqrt{2}{I}_p\sin (\mathrm{\ωt}+{\mathrm{\φ}}_p)+\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n)\\ i_B=\sqrt{2}{I}_p\sin (\mathrm{\ωt}+{\mathrm{\φ}}_p-\frac{2\mathrm{\π}}{3})+\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3})\\ i_C=\sqrt{2}{I}_p\sin (\mathrm{\ωt}+{\mathrm{\φ}}_p+\frac{2\mathrm{\π}}{3})+\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3})\end{array}\right.---(1-2)$

In formula, I _p, I _nbe respectively the effective value of electric current positive sequence component and negative sequence component, φ _pfor forward-order current power-factor angle, φ _nfor negative-sequence current power-factor angle.The active power of input unit is:

$P_A=\frac{1}{T}{\∫}_0^T{U}_{\mathrm{sA}}\·i_A\mathrm{dt}---(1-3)$

The reactive power of input unit is:

$Q_A=\frac{1}{T}{\∫}_0^T(U_{\mathrm{sA}}-U_n)i_A{e}^{-j\frac{\mathrm{\π}}{2}}\mathrm{dt}---(1-4)$

Formula (1-1) and formula (1-2) substitution formula (1-3) are also in like manner obtained to the active-power P of A, B, C three-phase change of current chain _a, P _b, P _cfor:

$\left\{\begin{array}{c}{P}_A=U_{\mathrm{RMS}}(I_p\cos \left({\mathrm{\φ}}_p\right)+I_n\cos \left({\mathrm{\φ}}_n\right))\\ P_B=U_{\mathrm{RMS}}(I_p\cos \left({\mathrm{\φ}}_p\right)+I_n\cos ({\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3}))\\ P_C=U_{\mathrm{RMS}}(I_p\cos \left({\mathrm{\φ}}_p\right)+I_n\cos ({\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3}))\end{array}\right.---(1-5)$

By formula (1-5), can be found out, by regulating size and the phase place of negative-sequence current can change the power division between three-phase.

Formula (1-1) and formula (1-2) substitution formula (1-4) are also in like manner obtained to the reactive power Q of A, B, C three-phase change of current chain _a, Q _b, Q _cfor:

$\left\{\begin{array}{c}{Q}_A=U(I_p\sin \left({\mathrm{\φ}}_p\right)+I_n\sin \left({\mathrm{\φ}}_n\right))\\ Q_B=U(I_p\sin \left({\mathrm{\φ}}_p\right)+I_n\sin ({\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3}))\\ Q_C=U(I_p\sin \left({\mathrm{\φ}}_p\right)+I_n\sin ({\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3}))\end{array}\right.---(1-6)$

Suppose to maintain the three-phase dc balance of voltage, the power of the required absorption of three-phase converter is respectively further be expressed as:

$\left\{\begin{array}{c}{P}_A^{*}=P^{*}-\mathrm{\Δ}{P}_A^{*}\\ P_B^{*}=P^{*}-\mathrm{\Δ}{P}_B^{*}\\ P_C^{*}=P^{*}-\mathrm{\Δ}{P}_C^{*}\\ Q^{*}=(Q_A^{*}+Q_B^{*}+Q_C^{*})/3\\ P^{*}=(P_A^{*}+P_B^{*}+P_C^{*})/3\end{array}\right.---(1-7)$

In formula, for the active power deviation of three-phase change of current chain,

In order to guarantee to export converter input and output power-balance, simultaneous formula (1-5)～formula (1-7) obtains:

$\left\{\begin{array}{c}{P}^{*}=U_{\mathrm{RMS}}{I}_p^{*}\cos \left({\mathrm{\φ}}_p^{*}\right)\\ Q^{*}=U_{\mathrm{RMS}}{I}_p^{*}\sin \left({\mathrm{\φ}}_p^{*}\right)\end{array}\right.---(1-8)$

$\left\{\begin{array}{c}{\mathrm{\ΔP}}_A^{*}=U_{\mathrm{RMS}}{I}_n\cos \left({\mathrm{\φ}}_n\right)\\ \mathrm{\Δ}{P}_B^{*}=U_{\mathrm{RMS}}{I}_n\cos ({\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3})\\ {\mathrm{\ΔP}}_C^{*}=U_{\mathrm{RMS}}{I}_n\cos ({\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3})\end{array}\right.---(1-9)$

Through type (1-8) can be determined by meritorious, idle instruction P ^*, Q ^*can determine effective value and the phase bit instruction of forward-order current

Through type (1-9) can obtain, as long as regulate amplitude and the phase place of negative-sequence current according to any two voltage deviations, just can guarantee that third phase power also meets the demands, and this process and forward-order current are irrelevant, also irrelevant with third phase power.Therefore this controls principle for controlling negative-sequence current, and can only regulate two-phase, below with AB two-phase, is adjusted to example.

A, B two-phase power deviation in formula (1-9) are launched to obtain:

$\left\{\begin{array}{c}{\mathrm{\ΔP}}_A^{*}=U_{\mathrm{RMS}}{I}_n\cos \left({\mathrm{\φ}}_n\right)\\ {\mathrm{\ΔP}}_B^{*}=\frac{\sqrt{3}{U}_{\mathrm{RMS}}{I}_n\sin \left({\mathrm{\φ}}_n\right)}{2}-\frac{U_{\mathrm{RMS}}{I}_n\cos \left({\mathrm{\φ}}_n\right)}{2}\end{array}\right.---(1-10)$

By formula (1-10), obtained:

$\left\{\begin{array}{c}{I}_n\cos \left({\mathrm{\φ}}_n\right)=\frac{\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\\ I_n\sin \left({\mathrm{\φ}}_n\right)=\frac{2\mathrm{\Δ}{P}_B^{*}+{\mathrm{\ΔP}}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\end{array}\right.---(1-11)$

Therefore:

$\left\{\begin{array}{c}{I}_n\cos (\mathrm{\ωt}+{\mathrm{\φ}}_n)=\cos \left(\mathrm{\ωt}\right)\frac{{\mathrm{\ΔP}}_A^{*}}{U_{\mathrm{RMS}}}-\sin \left(\mathrm{\ωt}\right)\frac{2\mathrm{\Δ}{P}_B^{*}+\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\\ I_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n)=\frac{2\mathrm{\Δ}{P}_B^{*}+{\mathrm{\ΔP}}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{{\mathrm{\ΔP}}_A^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\end{array}\right.---(1-12)$

From formula (1-2), in device output current, the expression formula of negative sequence component is:

$\left\{\begin{array}{c}{i}_A=\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n)\\ i_B=\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3})\\ i_C=\sqrt{2}{I}_n\sin (\mathrm{\ωt}+{\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3})\end{array}\right.---(1-13)$

The three-phase negative/positive current-order that change of current chain mean direct voltage is controlled will can be obtained in formula (1-12) substitution formula (1-13) carrying out for:

$\left\{\begin{array}{c}{i}_{\mathrm{An}}^{*}=\frac{2\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Bn}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}-\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)-\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Cn}}^{*}=-\frac{2\sqrt{2}\mathrm{\Δ}{P}_A^{*}+\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\end{array}\right.---(1-14)$

In like manner, as the system voltage U of converter _sA, U _sB, U _sCwith the current i that flows into converter _a, i _b, i _cwhile being cosine function, the expression formula obtain active power through deriving is identical during with SIN function.While adopting negative-sequence current to control, in like manner can obtain formula (1-12).Voltage, electric current adopt the negative sequence component expression formula of cosine form timer output current to be:

$\left\{\begin{array}{c}{i}_A=\sqrt{2}{I}_n\cos (\mathrm{\ωt}+{\mathrm{\φ}}_n)\\ i_B=\sqrt{2}{I}_n\cos (\mathrm{\ωt}+{\mathrm{\φ}}_n+\frac{2\mathrm{\π}}{3})\\ i_C=\sqrt{2}{I}_n\cos (\mathrm{\ωt}+{\mathrm{\φ}}_n-\frac{2\mathrm{\π}}{3})\end{array}\right.---(1-15)$

Formula (1-12) substitution formula (1-15) is obtained to voltage, electric current and while being cosine form, carries out the three-phase negative/positive current-order that change of current chain mean direct voltage is controlled:

$\left\{\begin{array}{c}{i}_{\mathrm{An}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)-\frac{2\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Bn}}^{*}=-\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}-\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Cn}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+2\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\end{array}\right.---(1-16)$

Therefore, the negative-sequence current obtaining according to formula (1-14) and formula (1-16), as output current instruction, can be controlled change of current chain mean direct voltage and reach balance.

The three-phase negative/positive current-order of the output of link shown in Fig. 3 is converted to dq axle component by abc-dq coordinate transform, adopts classical park transformation matrix, as shown in (1-17), coordinate transform schematic diagram as shown in Figure 4.

$P=\frac{2}{3}\left[\begin{array}{ccc}\cos \mathrm{\θ}& \cos (\mathrm{\θ}-2\mathrm{\π}/3)& \cos (\mathrm{\θ}+2\mathrm{\π}/3)\\ -\sin \mathrm{\θ}& -\sin (\mathrm{\θ}-2\mathrm{\π}/3)& -\sin (\mathrm{\θ}+2\mathrm{\π}/3)\\ \frac{1}{2}& \frac{1}{2}& \frac{1}{2}\end{array}\right]---(1-17)$

Fig. 5 has provided the block diagram of realizing of negative-sequence current decoupling zero controlling unit in Fig. 2, and its satisfied control law is shown below, wherein K _p1, K _p2, T _i1, T _i2coefficient for corresponding proportion-integrator.

$\left[\begin{array}{c}{U}_{\mathrm{nd}}^{*}\\ U_{\mathrm{nq}}^{*}\end{array}\right]=\left[\begin{array}{cc}{e}_{\mathrm{nd}}-\mathrm{\ω}{\mathrm{Li}}_{\mathrm{nq}}+K_{p1}({i_{\mathrm{nd}}}^{*}-i_{\mathrm{nd}})+\frac{1}{T_{i1}}\∫({i_{\mathrm{nd}}}^{*}-i_{\mathrm{nd}})& \mathrm{dt}\\ e_{\mathrm{nq}}+\mathrm{\ω}{\mathrm{Li}}_{\mathrm{nd}}+K_{p2}({i_{\mathrm{nq}}}^{*}-i_{\mathrm{nq}})+\frac{1}{T_{i2}}\∫({i_{\mathrm{nq}}}^{*}-i_{\mathrm{nq}})& \mathrm{dt}\end{array}\right]---(1-18)$

By the dq axle component of three-phase negative/positive current-order dq axle component i with converter output negative-sequence current _nd, i _nqsubtract each other the deviation of gained after proportional and integral controller, with dq shaft current coupling amount ω L _fci _nq, ω L _fci _ndand the dq axle component e of system voltage _nd, e _nqcarry out obtaining suc as formula the mathematical operation of rule described in 1-16 the dq axle component of negative phase-sequence modulating wave voltage carry out can obtaining three-phase negative/positive modulating wave voltage reference value after Parker inverse transformation control converter output and realize closed-loop control.

According to specific exemplary embodiment, invention has been described herein.It will be apparent under not departing from the scope of the present invention, carrying out to one skilled in the art suitable replacement or revise.Exemplary embodiment is only illustrative, rather than the restriction to scope of the present invention, and scope of the present invention is defined by appended claim.

Claims (2)

1. the control method of the change of current chain mean direct voltage based on negative-sequence current, it is characterized in that: this control method is that the mean direct voltage of any two-phase change of current chain in three-phase change of current chain is compared with the DC voltage average value of all chain links and obtained the mean direct voltage deviation of two-phase change of current chain, through proportional and integral controller, the mean direct voltage deviation of two-phase change of current chain is obtained to the active power deviation of corresponding phase change of current chain; Active power deviation through negative current instructions operation link, obtains the negative-sequence current component instruction of three-phase change of current chain in conjunction with the AC system voltage effective value of measuring gained; Through Park Transformation link, it by the negative-sequence current component instruction map of three-phase change of current chain, is the dq axle component of three-phase negative/positive current-order; Then by negative-sequence current decoupling zero controlling unit, obtain the dq axle component of negative phase-sequence modulating wave voltage, carry out subsequently Parker inverse transformation and obtain three-phase negative/positive modulating wave voltage reference value, control converter output and form closed-loop control;

Described negative current instructions operation link is that active power deviation and AC system voltage effective value are obtained to the negative-sequence current component instruction of three-phase change of current chain by mathematical operation:

Voltage U when converter place system _sA, U _sB, U _sCwith the current i that flows into converter _a, i _b, i _cwhile being SIN function, the negative-sequence current component instruction expression formula of all change of current chains is:

$\left\{\begin{array}{c}{i}_{\mathrm{An}}^{*}=\frac{2\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Bn}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}-\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)-\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Cn}}^{*}=-\frac{2\sqrt{2}\mathrm{\Δ}{P}_A^{*}+\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{U_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\end{array}\right.---(1-14)$

Voltage U when converter place system _sA, U _sB, U _sCwith the current i that flows into converter _a, i _b, i _cwhile being cosine function, the negative-sequence current component instruction expression formula of all change of current chains is:

$\left\{\begin{array}{c}{i}_{\mathrm{An}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)-\frac{2\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Bn}}^{*}=-\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}-\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\\ i_{\mathrm{Cn}}^{*}=\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}}{U_{\mathrm{RMS}}}\cos \left(\mathrm{\ωt}\right)+\frac{\sqrt{2}\mathrm{\Δ}{P}_B^{*}+2\sqrt{2}\mathrm{\Δ}{P}_A^{*}}{\sqrt{3}{U}_{\mathrm{RMS}}}\sin \left(\mathrm{\ωt}\right)\end{array}\right.---(1-16)$

In formula, for the active power deviation of A, B two-phase change of current chain, U _rMSfor AC system voltage effective value, ω is first-harmonic angular frequency, and t is the time;

Described negative-sequence current decoupling zero controlling unit is: by the dq axle component of three-phase negative/positive current-order with the dq axle component i that measures the converter output negative-sequence current of gained _nd, i _nqsubtract each other the deviation of gained after proportional and integral controller, with dq shaft current coupling amount ω L _fci _nq, ω L _fci _ndand the dq axle component e of system voltage _nd, e _nqafter performing mathematical calculations, obtain the dq axle component of negative phase-sequence modulating wave voltage carry out can obtaining three-phase negative/positive modulating wave voltage reference value after Parker inverse transformation control converter output and realize closed-loop control.

2. the control method of the change of current chain mean direct voltage based on negative-sequence current as claimed in claim 1, is characterized in that: in described negative-sequence current decoupling zero controlling unit the control law of mathematical operation as shown in the formula:

$\left[\begin{array}{c}{U}_{\mathrm{nd}}^{*}\\ U_{\mathrm{nq}}^{*}\end{array}\right]=\left[\begin{array}{c}{e}_{\mathrm{nd}}-{\mathrm{\ωL}}_{\mathrm{fc}}{i}_{\mathrm{nq}}+K_{p1}({i_{\mathrm{nd}}}^{*}-i_{\mathrm{nd}})+\frac{1}{T_{i1}}\∫({i_{\mathrm{nd}}}^{*}-i_{\mathrm{nd}})\mathrm{dt}\\ e_{\mathrm{nq}}+{\mathrm{\ωL}}_{\mathrm{fc}}{i}_{\mathrm{nd}}+K_{p2}({i_{\mathrm{nq}}}^{*}-i_{\mathrm{nq}})+\frac{1}{T_{i2}}\∫({i_{\mathrm{nq}}}^{*}-i_{\mathrm{nq}})\mathrm{dt}\end{array}\right]---(1-18)$

In formula, K _p1, K _p2, T _i1, T _i2coefficient for corresponding proportion-integrator.