CN106484998A - Modularization multi-level converter parameter integral Calculation Method based on Non-Linear Programming - Google Patents

Abstract

The invention belongs to Power System Analysis and calculating field, more particularly, to a kind of modularization multi-level converter parameter integral Calculation Method based on Non-Linear Programming.Including：Obtain systematic parameter；Design variable；Determine object function；Determine constraints；Nonlinear planning solution.The method that the present invention adopts Non-Linear Programming, to MMC main equipment parameter tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀Fundamental component U with inverter ac output voltage_CCarry out integrated solution, make the parameter value tried to achieve more accurate, save system Construction investment, reduce system operation loss, improve the combination property of system.

Description

Modularization multi-level converter parameter integral Calculation Method based on Non-Linear Programming

Technical field

The invention belongs to Power System Analysis and calculating field, more particularly, to a kind of modularity based on Non-Linear Programming is many Level converter parameter integral Calculation Method.

Background technology

Modularization multi-level converter (Modular Multilevel Converter, MMC) is power electronics of new generation Technology is applied to the core component of power system, no matter being flexible AC transmission or flexible DC power transmission, MMC represents skill The direction of art development.The capital equipment of MMC includes tietransformer, brachium pontis reactor, submodule capacitor etc..Main equipment parameter Design is the important component part of whole system design, and rational main equipment parameter can be effectively improved the dynamic of system and stable state Performance, reduces initial outlay and the operating cost of system, improves the economic performance index of system.

Chinese scholars propose the individually designed principle with regard to MMC main equipment parameter according to the system features of MMC.As closed In the parameter designing of tietransformer, based on meeting inverter range of operation, provide tietransformer rated secondary voltage Value principle, based on meeting System Reactive Power range of accommodation, determines that the gear number of tietransformer tap is chosen；With regard to submodule electricity The parameter designing of container, according to the limit value of submodule capacitor voltage stability bandwidth, the capacitance of determination sub-module capacitor；With regard to bridge The design of arm reactor, chooses the size to suppress phase circulation for the rational brachium pontis reactance value, suppresses inverter inside fault simultaneously The fault current climbing of brachium pontis is flow through during with DC side fault.Existing MMC main equipment Parameters design, is all to each Parameter is individually calculated, due to main equipment parameter between be mutually related, independent calculating can lead to parameter setting inaccurate.

Content of the invention

In order to solve the above problems, the invention provides a kind of modularization multi-level converter ginseng based on Non-Linear Programming Number integral Calculation Method, the method comprising the steps of：

1) obtain systematic parameter

Including system frequency f, DC voltage U_dc, single-phase upper brachium pontis submodule number N, tietransformer rated capacity S_n, Brachium pontis transient current climbing α, voltage fluctuation of capacitor percentage ratio ε, ac grid voltage stability bandwidth η, tietransformer short circuit resistance Anti- percent minima k_d%, tietransformer short-circuit impedance percent maximum k_a%, voltage modulated is than maximum m_max, the change of current The range of operation of device requires；

2) design variable

Tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀Fundamental component U with inverter ac output voltage_CConstitute unknown phasor x, that is,：

X=[U_S,L_T,L_arm,C₀,U_C] (1)

3) determine object function

Minf=-U_S(2)

4) determine constraints

Wherein,

ω=2* π * f；

(P₀,Q₀) it is the maximum corresponding coordinate of apparent energy operating point, wherein P in inverter range of operation₀For abscissa, I.e. active power value, Q₀For vertical coordinate, i.e. reactive power value；S_cFor injecting the maximum apparent energy of inverter, cos φ is the change of current The power factor of device；I_kmFor two frequency multiplication circulation peak values；ω is the fundamental wave angular frequency of inverter alternating voltage；L is to connect reactance；m For voltage modulated ratio；

5) nonlinear planning solution

The nonlinear programming problem that formula (1)-(9) are constituted solves, and obtains tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀, the fundamental component of inverter ac output voltage U_C.

Beneficial effect

The present invention is according to the analytical mathematic model of MMC, electric in analysis tietransformer parameter, submodule capacitance, brachium pontis On the basis of the value principle of anti-value, according to the thought of modularization multi-level converter parameter overall calculation, using Non-Linear Programming Method come to modularization multi-level converter parameter (include tietransformer rated secondary voltage U_S, tietransformer leakage Anti- L_T, brachium pontis reactance L_arm, submodule electric capacity C₀) carry out overall calculation, make the parameter value tried to achieve more accurate, improve system Combination property, saves system Construction investment, reduces system operation loss.The present invention using the method for Non-Linear Programming come to this 4 Individual parameter carries out overall calculation (mean and disposably all calculate 4 parameters), and existing method is all that parameter is separately counted Calculate, individually calculate each parameter, have ignored the coupling restricting relation between parameter.

Specific embodiment

The present invention proposes a kind of modularization multi-level converter parameter integral Calculation Method based on Non-Linear Programming, bag Include following steps：

1) obtain systematic parameter

Including system frequency f, DC voltage U_dc, single-phase upper brachium pontis submodule number N, tietransformer rated capacity S_n, Brachium pontis transient current climbing α, voltage fluctuation of capacitor percentage ratio ε, ac grid voltage stability bandwidth η, tietransformer short circuit resistance Anti- percent minima k_d%, tietransformer short-circuit impedance percent maximum k_a%, voltage modulated is than maximum m_max, the change of current The range of operation of device requires；

2) design variable

Tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀Fundamental component U with inverter ac output voltage_CConstitute unknown phasor x, that is,：

X=[U_S,L_T,L_arm,C₀,U_C] (1)

3) determine object function

Minf=-U_S(2)

4) determine constraints

Wherein,

ω=2* π * f；

(P₀,Q₀) it is the maximum corresponding coordinate of apparent energy operating point, wherein P in inverter range of operation₀For abscissa, I.e. active power value, Q₀For vertical coordinate, i.e. reactive power value；S_cFor injecting the maximum apparent energy of inverter, cos φ is the change of current The power factor of device；I_kmFor two frequency multiplication circulation peak values；ω is the fundamental wave angular frequency of inverter alternating voltage；L is to connect reactance；m For voltage modulated ratio；

5) nonlinear planning solution

The nonlinear programming problem that formula (1)-(9) are constituted solves, and obtains tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀, the fundamental component of inverter ac output voltage U_C.

It is analyzed with 200MW/ ± 160kV MMC-HVDC system, systematic parameter is as shown in table 1.

Table 1 systematic parameter

If voltage fluctuation of capacitor percentage ratio ε=5%, voltage modulated is than maximum m_max=0.95, tietransformer short circuit Impedance percent minima k_d%=12%, tietransformer short-circuit impedance percent maximum k_a%=15%, AC network electricity Pressure stability bandwidth η=5%, brachium pontis transient current climbing requires α≤0.1kA/ μ s, and inverter range of operation requires solstics P₀= 183MW、Q₀=83MVar, then result of calculation is as shown in table 2 below.

Table 2 result of calculation

This embodiment is only the present invention preferably specific embodiment, but protection scope of the present invention is not limited thereto, Any those familiar with the art the invention discloses technical scope in, the change or replacement that can readily occur in, All should be included within the scope of the present invention.Therefore, protection scope of the present invention should be with scope of the claims It is defined.

Claims (1)

1. the modularization multi-level converter parameter integral Calculation Method based on Non-Linear Programming is it is characterised in that methods described Comprise the following steps：

1) obtain systematic parameter

Including system frequency f, DC voltage U_dc, single-phase upper brachium pontis submodule number N, tietransformer rated capacity S_n, brachium pontis Transient current climbing α, voltage fluctuation of capacitor percentage ratio ε, ac grid voltage stability bandwidth η, tietransformer short-circuit impedance hundred Fraction minima k_d%, tietransformer short-circuit impedance percent maximum k_a%, voltage modulated is than maximum m_max, inverter Range of operation requires；

2) design variable

Tietransformer rated secondary voltage U_S, tietransformer leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀With The fundamental component U of inverter ac output voltage_CConstitute unknown phasor x, that is,：

X=[U_S,L_T,L_arm,C₀,U_C] (1)

3) determine object function

Minf=-U_S(2)

4) determine constraints

$-{\left(\frac{U_S{U}_C}{\mathrm{\ω}(L_T+\frac{1}{2}{L}_{arm})}\right)}^2+P_0^2+{(Q_0+\frac{U_S^2}{\mathrm{\ω}(L_T+\frac{1}{2}{L}_{arm})})}^2\≤0---\left(3\right)$

$-L_{arm}+\frac{1}{8{\mathrm{\ω}}^2{C}_0\left(\frac{U_{dc}}{N}\right)}(\frac{S_C}{3I_{km}}+U_{dc})\≤0---\left(5\right)$

$-L_{arm}+\frac{U_{dc}}{2\mathrm{\α}}\≤0---\left(6\right)$

$-L_T+k_d\%\·\frac{U_S^2}{S_n}\≤0---\left(7\right)$

$L_T-k_a\%\·\frac{U_S^2}{S_n}\≤0---\left(8\right)$

$U_C-m_{max}\frac{U_{dc}}{2}\frac{\sqrt{3}}{\sqrt{2}}\≤0---\left(9\right)$

Wherein,

ω=2* π * f；

$S_C=\sqrt{P_0^2+{(Q_0-\frac{P_0^2+Q_0^2}{U_S^2}\mathrm{\ω}L)}^2};$

$I_{km}=\frac{\sqrt{P_0^2+Q_0^2}}{U_S}\·\frac{\sqrt{2}}{\sqrt{3}}\·\frac{1}{2}\·20\%;$

$m=\frac{\frac{\sqrt{2}}{\sqrt{3}}\sqrt{\frac{{\left(\mathrm{\ω}L\right)}^2}{U_S^2}\left(P_0^2+Q_0^2\right)+U_S^2-2{\mathrm{\ωLQ}}_0}}{\frac{U_{dc}}{2}};$

(P₀,Q₀) it is the maximum corresponding coordinate of apparent energy operating point, wherein P in inverter range of operation₀For abscissa, that is, have Work(performance number, Q₀For vertical coordinate, i.e. reactive power value；S_cFor injecting the maximum apparent energy of inverter, cos φ is inverter Power factor；I_kmFor two frequency multiplication circulation peak values；ω is the fundamental wave angular frequency of inverter alternating voltage；L is to connect reactance；M is electricity Pressure modulation ratio；

5) nonlinear planning solution

The nonlinear programming problem that formula (1)-(9) are constituted solves, and obtains tietransformer rated secondary voltage U_S, connection Connect transformator leakage reactance L_T, brachium pontis reactance value L_arm, submodule capacitance C₀, the fundamental component U of inverter ac output voltage_C.