CN104078985B - A kind of static reacance generator connects the computational methods of inductance - Google Patents

Abstract

A kind of static reacance generator of disclosure connects the computational methods of inductance, described static reacance generator comprises three and connects inductance, a DC capacitor and six valve cells, wherein, six valve cell one group of series connection between two, three series arms of formation are in parallel again; Three one end connecting inductance are connected with a phase of system busbar respectively, and the other end is connected with the junction point of two valve cells in aforementioned three series arms respectively; And DC capacitor is in parallel with aforementioned three series arms; Described computational methods include the steps of determining that modulation ratio during static reacance generator zero load; Determine static reacance generator output maximum idle time modulation ratio; Calculate and meet the inductance value connecting inductance that idle output requires. The method connects inductance parameters for current high-voltage large-capacity static reacance generator and selects the deficiency of dependence experience value, it is provided that practical Theoretical Calculation foundation, has significantly high design guidance meaning.

Description

A kind of static reacance generator connects the computational methods of inductance

Technical field

The invention belongs to high-power electric and electronic field, connect the computational methods of inductance particularly to a kind of static reacance generator in high-voltage large-capacity static reacance generator field.

Background technology

Static reacance generator (SVG, StaticVarGenerator) technology is as a developing direction of Technology of Dynamic Reactive Power Compensation, because having, volume is little, volumetric ratio is big, output characteristics is desirable, continuously adjustable, fast response time, compensation capacity are affected the advantages such as little by system voltage, becomes the focus of domestic and international associated mechanisms research.

Fig. 1 is high-voltage large-capacity static reacance generator schematic diagram, static reacance generator comprises three and connects inductance, DC capacitor and six valve cells, wherein, each valve cell is directly composed in series by a number of power device, can coordinate shown in Fig. 2, after six valve cell one group of series connection between two, three series arms formed are in parallel again; Three one end connecting inductance are connected with a phase of system busbar respectively, and the other end is connected with the junction point of two valve cells in aforementioned three series arms respectively; And DC capacitor is in parallel with aforementioned three series arms. The ultimate principle of SVG is exactly will from commutation bridge circuit by connecting inductance in parallel on electrical network, suitably regulate the phase and amplitude (current indirect control of bridge circuit AC output voltage, SVG is equivalent to controllable voltage source), or directly control its ac-side current (Direct Current Control, SVG is equivalent to controllable current source), this circuit just can be made to absorb or send the reactive current meeting requirement, reaching the purpose of dynamic passive compensation.

Connect the inductance key equipment as static reacance generator, there is the effect such as storage energy two-way feeding, adjustment output current phase, suppression higher harmonic current, it not only has influence on the dynamic and static response of SVG device, but also governs the output of SVG, power factor and DC voltage. Current SVG connects the parameter of inductance and selects to be the angle from harmonic characterisitic and economy, and taking its inductance perunit value is 0.2-0.5, it does not have actual Theoretical Calculation foundation.

This case proposes for current technology blank just.

Summary of the invention

The purpose of the present invention, it is in that the computational methods providing a kind of static reacance generator to connect inductance, it connects inductance parameters for current high-voltage large-capacity static reacance generator and selects the deficiency of dependence experience value, it is provided that practical Theoretical Calculation foundation, has significantly high design guidance meaning.

In order to reach above-mentioned purpose, the solution of the present invention is:

A kind of static reacance generator connects the computational methods of inductance, and described static reacance generator comprises three and connects inductance, a DC capacitor and six valve cells, wherein, six valve cell one group of series connection between two, three series arms of formation are in parallel again; Three one end connecting inductance are connected with a phase of system busbar respectively, and the other end is connected with the junction point of two valve cells in aforementioned three series arms respectively; And DC capacitor is in parallel with aforementioned three series arms; Described computational methods comprise the steps:

(1) according to formulaM is compared in modulation when determining static reacance generator zero load₀, wherein, U_dcFor static reacance generator DC voltage time properly functioning, U_sFor system busbar voltage;

(2) determine static reacance generator output maximum idle time modulation ratio for m_max;

(3) according to formulaCalculate and meet the inductance value connecting inductance L that idle output requires, wherein, Q_nFor SVG device rated capacity, ��=2 �� f, f are system frequency.

Above-mentioned computational methods also include step (4) after step (3), and whether the connection inductance value that verification step (3) calculates meets harmonics restraint and transient current tracer request, and checking formula is:

$\frac{(1-0.75m_0)U_s^2}{\mathrm{\&Delta;}{I}_p\%f_s{Q}_n}<L<\frac{4U_s^2}{3m_0\mathrm{\&omega;}{Q}_n}$

Wherein, �� I_p% is the percentage ratio that static reacance generator electric current allows fluctuation, f_sFor static reacance generator switching frequency.

After adopting such scheme, the present invention is applicable to high-voltage large-capacity static reacance generator and connects inductance parameters selection, practical Theoretical Calculation foundation is provided, there is significantly high design guidance meaning, it is to avoid cause the appearance of SVG output current harmonics situation bigger than normal because inductance parameters that empirically method obtains is less than normal; Prevent from causing owing to inductance parameters that empirically method obtains is bigger than normal SVG cannot amount of exports constant volume idle; For the condition running offer necessity that high-voltage large-capacity stillness wattless occurrence apparatus is reliable and stable at the scene.

Accompanying drawing explanation

Fig. 1 is the connection diagram of high-voltage large-capacity static reacance generator;

Fig. 2 is the built-up circuit figure of any valve unit in Fig. 1;

Fig. 3 is the one phase equivalent figure that static reacance generator accesses system.

Detailed description of the invention

Below with reference to accompanying drawing, technical scheme is described in detail.

The present invention provides a kind of static reacance generator to connect the computational methods of inductance, shown in Fig. 3, is the SVG one phase equivalent figure accessing system, wherein, and U_sFor system busbar voltage, U_rExporting fundamental voltage for SVG, L is for connecting inductance, and Q is SVG output, it is assumed that U_sAnd U_rBetween phase contrast be ��, 3 �� are usually no more than for SVG, ��, i.e. cos �� �� 1, are carried out below analytical calculation:

(1) SVG exports fundamental voltage U_r:

$U_r=m\frac{U_{\mathrm{dc}}}{2\sqrt{2}}$

Wherein, m is modulation ratio, U_dcFor static reacance generator DC voltage time properly functioning;

(2) SVG output Q:

$Q=\frac{U_s(U_r\cos \mathrm{\&delta;}-U_s)}{X_L}\&ap;\frac{U_s(U_r-U_s)}{X_L}$

Wherein, X_LRepresent the power frequency reactance connecting inductance, X_L=�� L, �� represent angular frequency.

(3) according to SVG DC voltage U time properly functioning_dcWith system busbar voltage U_sM is compared in modulation when determining SVG zero load₀:

$m_0=\frac{2\sqrt{2}\&times;U_s}{\sqrt{3}\&times;U_{\mathrm{dc}}}$

(4) assume that SVG can export maximum idle be the nominal reactive of 1.2 times, export maximum idle time modulation than for m_max, then have:

$Q_{\max }=1.2Q_n=\frac{U_s(m_{\max }\frac{\sqrt{3}{U}_{\mathrm{dc}}}{2\sqrt{2}}-U_s)}{\mathrm{\&omega;L}}$

Wherein, Q_nFor SVG device rated capacity, ��=2 �� f, f are system frequency, value 50Hz; During SPWM, m_max=1, during SVPWM, m_max=1.15;

(5) by m₀Substitute into Q_max:

$1.2Q_n=(\frac{m_{\max }}{m_0}-1)\frac{U_s^2}{\mathrm{\&omega;L}}$

(6) therefore, the final inductance value connecting inductance L is:

$L=(\frac{m_{\max }}{m_0}-1)\&times;\frac{U_s^2}{1.2\mathrm{\&omega;}{Q}_n}$

(7) checking: the connection inductance numeric area meeting harmonics restraint and transient current tracer request provided in many documents is:

$\frac{(1-0.75m_0)U_s^2}{\mathrm{\&Delta;}{I}_p\%f_s{Q}_n}<L<\frac{4U_s^2}{3m_0\mathrm{\&omega;}{Q}_n}$

Wherein, �� I_p% is the percentage ratio that SVG electric current allows fluctuation, f_sFor static reacance generator switching frequency.

For 10kV high-voltage large-capacity SVG, DC voltage takes 18kV, obtains m₀=0.9, m_max=1.15, switching frequency 1950, �� I_p%=0.2, so:

The ratio of L and the upper limit:

$L/\frac{4U_s^2}{3m_0\mathrm{\&omega;}{Q}_n}=\frac{m_{\max }-m_0}{1.6}=0.156<1$

The ratio of L and lower limit:

$L/\frac{(1-0.75m_0)U_s^2}{\mathrm{\&Delta;}{I}_p\%f_s{Q}_n}=\frac{(m_{\max }-m_0)\mathrm{\&Delta;}{I}_p\%f_s}{2.4\mathrm{\&pi;}{m}_0(1-0.75m_0)f}=1.77>1$

Therefore, it was demonstrated that the inductance value calculated meets harmonics restraint and transient current tracer request.

Above example is only the technological thought that the present invention is described, it is impossible to limits protection scope of the present invention, every technological thought proposed according to the present invention, any change done on technical scheme basis with this, each falls within scope.

Claims (1)

1. static reacance generator connects computational methods for inductance, and described static reacance generator comprises three and connects inductance, a DC capacitor and six valve cells, wherein, six valve cell one group of series connection between two, three series arms of formation are in parallel again; Three one end connecting inductance are connected with a phase of system busbar respectively, and the other end is connected with the junction point of two valve cells in aforementioned three series arms respectively; And DC capacitor is in parallel with aforementioned three series arms; It is characterized in that described computational methods comprise the steps:

(1) according to formulaM is compared in modulation when determining static reacance generator zero load₀, wherein, U_dcFor static reacance generator DC voltage time properly functioning, U_sFor system busbar voltage;

(2) determine static reacance generator output maximum idle time modulation ratio for m_max;

(3) according to formulaCalculate and meet the inductance value connecting inductance L that idle output requires, wherein, Q_nFor SVG device rated capacity, ��=2 �� f, f are system frequency;

(4) whether the connection inductance value that verification step (3) calculates meets harmonics restraint and transient current tracer request, and checking formula is:

$\frac{(1-0.75m_0)U_s^2}{{\mathrm{\&Delta;I}}_p{\mathrm{\%f}}_s{Q}_n}<L<\frac{4U_s^2}{3m_0{\mathrm{\&omega;Q}}_n}$

Wherein, �� I_p% is the percentage ratio that static reacance generator electric current allows fluctuation, f_sFor static reacance generator switching frequency.