CN103606935B - A kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator - Google Patents

Abstract

The invention provides a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, comprise the following steps: calculate line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load ; Calculate output current i (t) of static state synchronization reactive compensator after exporting idle given sudden change; Select the best switching point holding perception.The invention provides a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, owing to ensure that the outputting current steadily problem in handoff procedure, the symmetry of static state synchronization reactive compensator output current, harmonic content have larger improvement, improve static state synchronization reactive compensator and dynamically show.Holding the normal output that ensure that static state synchronization reactive compensator electric current in perceptual handoff procedure, there will not be over-current phenomenon avoidance in short-term, static state synchronization reactive compensator performance gets a promotion.

Description

A kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator

Technical field

The invention belongs to electric and electronic technical field, be specifically related to a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator.

Background technology

The DC voltage-stabilizing problem of cascaded H-bridges inverter type STATCOM is the important subject in this field always.The quality of DC voltage-stabilizing effect directly has influence on the stability of STATCOM device self work, can produce a lot of impact to device output characteristic simultaneously.Because the cascaded H-bridges unit of device is independent separately, therefore need to carry out voltage stabilizing control by different means for different operating states.In voltage stabilizing Study on Problems before, stable state voltage stabilizing obtains a lot of concern.And for dynamic voltage stabilizing, because its process is complicated rapidly, and problem can obtain alleviation to a certain extent when having larger allowance when apparatus design, so there is no receive too large concern.

Capacitive is there is at the offset current of static state synchronization reactive compensator (STATCOM)---when perception switches, due to the operating characteristic of STATCOM, can there is the phasing back of 180 ° in its output current, and voltage-phase then changes very little.When STATCOM normally works, device output voltage and electric current mutual deviation 90 °, therefore in half power frequency period 0.01s, half the time is to capacitor charging, and half the time is to capacitor discharge, and DC capacitor voltage is stablized and be there is certain ripple.If but output current generation phasing back, then in ensuing half power frequency period, the DC bus capacitor of STATCOM device can by trickle charge or electric discharge, this instability that will STATCOM brought to run.Band is served concrete threat by this phenomenon, is embodied in:

1, DC bus capacitor there will be overvoltage or under-voltage phenomenon, especially overvoltage phenomenon.If the d that this due to voltage spikes and the action of switching tube bring merges, will bring the overvoltage having more threat, switch tube, DC bus capacitor cause damage.

2, shown by emulation, hold the concussion of DC capacitor voltage after perception switches relevant with concussion initial value with recovery time, initial value is less, and the concussion amplitude of capacitance voltage and recovery time are also all less, and vice versa.The harmonic content of this direct voltage concussion meeting to output current, symmetry all affects.

3, for some switching points, likely there is over-current phenomenon avoidance, the connection inductive discharge of this mainly meritorious between three-phase transmission and STATCOM and electrical network causes, although be overcurrent in short-term, choose reasonable switching point also can guarantee the current stabilization in handoff procedure.

4, the rising of DC capacitor voltage, the direct current of STATCOM controller is got and can be brought certain influence, be particularly the mode that controller is powered with single step-down switching power supply, this overvoltage likely damages controller power source, the voltage power supply scope of simple raising Switching Power Supply also can cause the increase of cost, and the selection of non-economy.

Summary of the invention

In order to overcome the deficiencies in the prior art, the invention provides a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, owing to ensure that the outputting current steadily problem in handoff procedure, the symmetry of static state synchronization reactive compensator output current, harmonic content have larger improvement, improve static state synchronization reactive compensator and dynamically show.Holding the normal output that ensure that static state synchronization reactive compensator electric current in perceptual handoff procedure, there will not be over-current phenomenon avoidance in short-term, static state synchronization reactive compensator performance gets a promotion

In order to realize foregoing invention object, the present invention takes following technical scheme:

The invention provides a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, said method comprising the steps of:

Step 1: calculate line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load

Step 2: calculate output current i (t) of static state synchronization reactive compensator after exporting idle given sudden change;

Step 3: select the best switching point holding perception.

In described step 1, line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load be expressed as:

Wherein, U _mfor grid voltage amplitude, U _m2for the amplitude of static state synchronization reactive compensator output voltage, for the phase angle of static state synchronization reactive compensator output voltage, ω is angular frequency;

Kirchhoff's second law expression formula under the complex frequency equivalent electric circuit obtained after laplace transform is:

$-{\stackrel{\→}{U}}_s\left(s\right)+\mathrm{SL}\stackrel{\→}{I}\left(s\right)+R\stackrel{\→}{I}\left(s\right)+\mathrm{Li}(0\_)+{\stackrel{\→}{U}}_c\left(s\right)=0---\left(2\right)$

Wherein, s is complex variable, and L is equivalent inductance, and R is equivalent resistance, and i (0_) is electric current initial value;

So, with can be expressed as again:

In step 2, obtain the electric current of equivalent electric circuit after zero moment under complex frequency domain by formula (3) have:

To what try to achieve carry out inverse Laplace transform, obtain the output current time-domain value of static state synchronization reactive compensator have:

Owing to existing r=0;

Simplify thus and obtain output current i (t) expression formula of static state synchronization reactive compensator after the idle sign mutation of load and be:

$i\left(t\right)=-e^{-\frac{\mathrm{Rt}}{L}}i(0\_)+\frac{(U_m+U_{m2})(-\cos \mathrm{\ωt}+e^{-\frac{\mathrm{Rt}}{L}})\mathrm{\ωL}+R(U_m-U_{m2})\sin \mathrm{\ωt}}{R^2+{\mathrm{\ω}}^2{L}^2}---\left(6\right).$

In described step 3, select after the idle Setting signal of load is stable, static state synchronization reactive compensator output current maximum point is that the best switching point holding perception switches output voltage; Every two-phase output current phase 30 °.

Compared with prior art, beneficial effect of the present invention is:

1., compared to prior art, the stability of DC capacitor voltage in handoff procedure, resume speed are all significantly improved;

2. the meritorious transmission between three-phase is stablized, and to there will not be between two-phase meritoriously to pass mutually, causes that a phase capacitance voltage obviously raises and another phase capacitance voltage is obviously on the low side;

3., by reducing the undulate quantity of DC capacitor, correspondingly reduce the cost requirement in static state synchronization reactive compensator design process;

4., owing to ensure that the outputting current steadily problem in handoff procedure, the symmetry of static state synchronization reactive compensator output current, harmonic content have larger improvement, improve static state synchronization reactive compensator and dynamically show;

5. holding the normal output that ensure that static state synchronization reactive compensator electric current in perceptual handoff procedure, there will not be over-current phenomenon avoidance in short-term, static state synchronization reactive compensator performance gets a promotion.

Accompanying drawing explanation

Fig. 1 is the dynamic DC voltage-stabilizing method flow diagram of static state synchronization reactive compensator;

Fig. 2 is that static state synchronization reactive compensator is incorporated into the power networks equivalent circuit diagram;

Equivalence Laplace's operation circuit diagram when Fig. 3 is static state synchronization reactive compensator load switching.

Embodiment

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

Capacitive is at STATCOM---in the process that perception switches, by the action time of the idle Setting signal of choose reasonable STATCOM controller, thus make the phase overturn of STATCOM output current occur in desirable position, and then make the meritorious transmission in handoff procedure comparatively stable, ensure that the voltage stabilization of STATCOM DC capacitor.

The invention provides a kind of dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, said method comprising the steps of:

Step 1: calculate line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load

Step 2: calculate output current i (t) of static state synchronization reactive compensator after exporting idle given sudden change;

Step 3: select the best switching point holding perception.

In described step 1, the equivalent electric circuit of STATCOM when grid-connected work and equivalent Laplace's operation circuit as shown in Figures 2 and 3, line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load be expressed as:

Wherein, U _mfor grid voltage amplitude, U _m2for the amplitude of static state synchronization reactive compensator output voltage, for the phase angle of static state synchronization reactive compensator output voltage, ω is angular frequency;

Kirchhoff's second law expression formula under the complex frequency equivalent electric circuit obtained after laplace transform is:

$-{\stackrel{\→}{U}}_s\left(s\right)+\mathrm{SL}\stackrel{\→}{I}\left(s\right)+R\stackrel{\→}{I}\left(s\right)+\mathrm{Li}(0\_)+{\stackrel{\→}{U}}_c\left(s\right)=0---\left(2\right)$

Wherein, s is complex variable, and L is equivalent inductance, and R is equivalent resistance, and i (0_) is electric current initial value;

So, with can be expressed as again:

In step 2, obtain the electric current of equivalent electric circuit after zero moment under complex frequency domain by formula (3) have:

To what try to achieve carry out inverse Laplace transform, obtain the output current time-domain value of static state synchronization reactive compensator have:

Owing to existing r=0;

Simplify thus and obtain output current i (t) expression formula of static state synchronization reactive compensator after the idle sign mutation of load and be:

$i\left(t\right)=-e^{-\frac{\mathrm{Rt}}{L}}i(0\_)+\frac{(U_m+U_{m2})(-\cos \mathrm{\ωt}+e^{-\frac{\mathrm{Rt}}{L}})\mathrm{\ωL}+R(U_m-U_{m2})\sin \mathrm{\ωt}}{R^2+{\mathrm{\ω}}^2{L}^2}---\left(6\right).$

In described step 3, select after the idle Setting signal of load is stable, static state synchronization reactive compensator output current maximum point is that the best switching point holding perception switches output voltage; Every two-phase output current phase 30 °.

Meanwhile, although its size of current is identical when STATCOM output capacitive or perceptual rated current, because the size of STATCOM output voltage is distinguished, the instantaneous active component size of STATCOM is had any different, and consequent DC side ripple varies in size.It is large that correspondence shows as capacitive state DC ripple, and perceptual operating state DC ripple is little.Also just therefore, when STATCOM is switched to perception by capacitive, instantaneous active component reduces, and the capacitance voltage spike in handoff procedure is less, is not easy the operation stability affecting STATCOM device.Carrying out process to switching point when being switched to perception by capacitive may cause DC capacitor voltage unstable on the contrary, therefore switches to perception by capacitive, can process.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.

Claims (3)

1. the dynamic DC voltage-stabilizing method of static state synchronization reactive compensator, is characterized in that: said method comprising the steps of:

Step 1: calculate line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load

Step 2: calculate output current i (t) of static state synchronization reactive compensator after exporting idle given sudden change;

Step 3: select the best switching point holding perception;

In described step 1, line voltage with the output voltage of static state synchronization reactive compensator after the idle sign mutation of load be expressed as:

Wherein, U _mfor grid voltage amplitude, U _m2for the amplitude of static state synchronization reactive compensator output voltage, for the phase angle of static state synchronization reactive compensator output voltage, ω is angular frequency;

Kirchhoff's second law expression formula under the complex frequency equivalent electric circuit obtained after laplace transform is:

$-{\stackrel{\→}{U}}_s\left(s\right)+SL\stackrel{\→}{I}\left(s\right)+R\stackrel{\→}{I}\left(s\right)+Li(0\_)+{\stackrel{\→}{U}}_c\left(s\right)=0---\left(2\right)$

Wherein, s is complex variable, for the electric current of equivalent electric circuit under complex frequency domain after zero moment, L is equivalent inductance, and R is equivalent resistance, and i (0_) is electric current initial value;

So, with can be expressed as again:

2. the dynamic DC voltage-stabilizing method of static state synchronization reactive compensator according to claim 1, is characterized in that: in described step 2, obtains the electric current of equivalent electric circuit after zero moment under complex frequency domain by formula (3) have:

To what try to achieve carry out inverse Laplace transform, obtain the output current time-domain value of static state synchronization reactive compensator have:

Owing to existing r=0;

Simplify thus and obtain output current i (t) expression formula of static state synchronization reactive compensator after the idle sign mutation of load and be:

$i\left(t\right)=-e^{-\frac{Rt}{L}}i(0\_)+\frac{(U_m+U_{m2})(-\cos \mathrm{\ω}t+e^{-\frac{Rt}{L}})\mathrm{\ω}L+R(U_m-U_{m2})\sin \mathrm{\ω}t}{R^2+{\mathrm{\ω}}^2{L}_2}---\left(6\right).$

3. the dynamic DC voltage-stabilizing method of static state synchronization reactive compensator according to claim 1, it is characterized in that: in described step 3, select after the idle Setting signal of load is stable, static state synchronization reactive compensator output current maximum point is that the best switching point holding perception switches output voltage; Every two-phase output current phase 30 °.