CN103151792A - Harmonic current suppression device for ultrahigh-voltage direct current power transmission system - Google Patents

Abstract

The invention discloses a harmonic current suppression device for an ultrahigh-voltage direct current power transmission system. The device comprises alternating current systems. The power of the alternating current system on one side flows to the alternating current system on the other side. The alternating current system on one side is connected with a converter station working in a rectification state, and is connected with a converter after the step-up of a converter transformer to convert alternating current into direct current, and after the direct current is transmitted to the converter station by a direct current power transmission line, the converter station working in an inversion state inverts the direct current into the alternating current, and is connected with the alternating current system on the other side after the step-down of the converter transformer. Eleventh-order and thirteenth-order harmonics can be effectively eliminated, harmonic current THD on the alternating current side of the ultrahigh-voltage direct current power transmission system can be greatly reduced, and voltage and current harmonics on a direct current side can be suppressed to a certain extent.

Description

Harmonic current restraining device in extra-high voltage DC transmission system

Technical field

The invention belongs to the restraining device of extra-high voltage direct-current transmission field, especially phase shifting transformer harmonic current in extra-high voltage DC transmission system.

Background technology

But extra-high voltage DC transmission system with the fast and flexible of its power adjustments, the transient stability that does not increase the system short circuit capacity assistance system, loss is low and take up an area the characteristic such as province, obtain a wide range of applications at aspects such as long-distance and large-capacity power transmission, Asynchronous Interconnection, submarine cable transmissions of electricity in recent years.Due to the nonlinear characteristic of converter in DC transmission system, all inevitably produce a large amount of harmonic voltage and harmonic current in AC system and direct current system, user and electric power system itself are impacted and endanger.

Therefore, in extra-high voltage DC transmission system, alternating current filter and DC filter are indispensable elements.For the filtering of AC system, generally parallel filtering apparatus on converter transformer net side bus, double as reactive-load compensation equipment.Suppress and the reactive power compensation problem though this mode can solve the harmonic wave of AC system preferably, do not overcome the impact that the idle and harmonic wave by converter transformer brings transformer itself; And the phenomenon of alternating current-direct current side harmonic excess still appears in existing extra-high voltage direct-current transmission engineering operation in a large number.

At present extra-high voltage DC transmission system adopts the structure of two 12 arteries and veins of single-stage, bipolar 12 arteries and veins and bipolar two 12 arteries and veins more, and the harmonic wave of AC is mainly (12n ± 1 time) harmonic wave 11,13 times.Compared to 6 pulse wave circuit, the harmonic wave of 12 pulse wave circuit has obtained larger inhibition, but its harmonic content is still larger, and 11,13 subfrequencies are lower, and cost is higher for the design of filter.Therefore, need to further suppress the content of harmonic current in the situation that increase not significantly cost.

Summary of the invention

The technical problem to be solved in the present invention is to provide harmonic current restraining device in extra-high voltage DC transmission system, this device both had been applicable to the extra-high voltage DC transmission system of bipolar 12 kank structures, also be applicable to single-stage and bipolar two 12 arteries and veins extra-high voltage DC transmission systems, can effectively eliminate 11,13 subharmonic, greatly reduce the harmonic current THD of extra-high voltage DC transmission system AC, and can necessarily suppress dc voltage, current harmonics simultaneously.

For achieving the above object, technical scheme of the present invention is as follows:

Harmonic current restraining device in extra-high voltage DC transmission system comprises:

One AC system,

The power flow direction opposite side AC system of one top-cross streaming system,

A described top-cross streaming system connects the current conversion station that is operated in rectification state, is connected with converter after boosting by converter transformer, and alternating current is transformed to direct current,

Then after by DC power transmission line, direct current being transferred to current conversion station, the current conversion station that is operated in inverter mode is alternating current with dc inverter, and is connected with the opposite side AC system by after the converter transformer step-down.

In a preferred embodiment of the present invention, the converter in described current conversion station adopts 4 bridges connect and be divided into two groups, and the converter transformer of first group adopts common three-winding transformer, and the connection group number is YYD11; The converter transformer of second group adopts phase shifting transformer, and its phase shifting angle is respectively-15 ° ,-45 °.

In a preferred embodiment of the present invention, described three-winding transformer and phase shifting transformer, their equivalent impedance, voltage and power loss are identical.

In a preferred embodiment of the present invention, an AC system is also received in the former limit of two groups of converter transformers in described current conversion station, and secondary is received respectively on a converter bridge.

By technique scheme, the invention has the beneficial effects as follows:

1. the method for inhibiting harmonic current of this extra-high voltage DC transmission system on original bipolar 12 arteries and veins HVDC (High Voltage Direct Current) transmission system architecture basics, is replaced the wherein common three-winding transformer of a utmost point with phase shifting transformer.By introducing phase shifting transformer, secondary side winding output voltage and line voltage phase angle difference anodal and the negative pole transformer are respectively: 0 ° ,-30 ,-15 ° ,-45 °, in fact consisted of like this 24 pulse wave circuit between both positive and negative polarity.Due to secondary side output voltage mutual deviation certain angle, the input current of each convertor unit is converted after the transformer primary side 180 ° of 11,13 times and 35, the harmonic phase mutual deviation of 37 inferior specific times, they are eliminated when stack forms the total input current of AC mutually mutually, thereby have reduced total THD.

2. the phase shifting transformer in the method for inhibiting harmonic current of this extra-high voltage DC transmission system adopts the extend-triangle structure, although it is high that the more common three-winding transformer of its cost is wanted, but after the application phase shifting transformer, harmonic content significantly reduces, the expense of filter can significantly reduce, and the volume of filter also reduces greatly.

3. the present invention has characteristics reasonable in design, that circuit is simple, stable and reliable for performance, in the situation that increase not significantly the harmonic content that cost can effectively reduce input current, can be widely used in comprising the DC transmission system that surpasses two 12 arteries and veins cellular constructions.

Description of drawings

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or description of the Prior Art, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is for adopting the extra-high voltage DC transmission system of phase shifting transformer;

Fig. 2 is the wherein circuit theory diagrams of a side of DC transmission system;

Fig. 3 is for adopting the front AC input voltage circuit waveform of phase shifting transformer;

Fig. 4 is AC input voltage and input current waveform after the employing phase shifting transformer;

Fig. 5 is for adopting the spectrum analysis of the front AC input current of phase shifting transformer;

Fig. 6 is the spectrum analysis of AC input current after the employing phase shifting transformer.

Embodiment

For technological means, creation characteristic that the present invention is realized, reach purpose and effect is easy to understand, below in conjunction with concrete diagram, further set forth the present invention.

Bipolar 12 pulse wave extra-high voltage DC transmission systems as shown in Figure 1, mainly by converting plant, DC power transmission line and Inverter Station three parts consist of.

Suppose the power flow direction AC system 2 of AC system 1 in figure, the current conversion station of AC system 1 one sides is operated in rectification state, and the current conversion station of AC system 2 one sides is operated in inverter mode.

Converter in current conversion station adopts 4 bridges connect and be divided into two groups, and the converter transformer of first group adopts common three-winding transformer, and the connection group number is YYD ₁₁The converter transformer of second group adopts phase shifting transformer, and its phase shifting angle is respectively-15 ° ,-45 °;

Select suitable three-winding transformer and phase shifting transformer, make its equivalent impedance, voltage and power loss identical; With the former limit of two groups of converter transformers and receive AC system 1, secondary is received respectively on a converter bridge, and like this, four secondary winding voltage amplitudes are identical, phase angle is divided equally in 60 °, are respectively 0 ° ,-30 ,-15 ° ,-45 °.

AC system 1 is connected with converter after boosting by converter transformer, is direct current with exchange conversion, by remote DC power transmission line, power delivery is arrived a distant place.Power delivery is after Inverter Station, and converter is to exchange with dc inversion, by being connected with AC system 2 after the converter transformer step-down.

AC system 1 and 2 is bound up by current conversion station and DC power transmission line, and the electric energy support can be provided mutually, has improved the stability of AC system.

With reference to Fig. 2, first analyze the Harmonics of Input of anodal 12 arteries and veins circuit, for 6 pulse wave circuit, its harmonic wave is mainly 6n ± 1 time, order:

$\left\{\begin{array}{c}{i}_a=\underset{n=\mathrm{1,5,7,11,13}...}{\overset{\∞}{\mathrm{\Σ}}}{\hat{I}}_n\sin (\mathrm{n\ωt}+{\mathrm{\φ}}_n)\\ i_{\tilde{a}}=\underset{n=\mathrm{1,5,7,11,13}...}{\overset{\∞}{\mathrm{\Σ}}}{\hat{I}}_n\sin (n(\mathrm{\ωt}+\mathrm{\δ})+{\mathrm{\φ}}_n)\end{array}\right.$

Wherein δ=-30 ° are the angle of the leading winding of secondary winding.For convenience of calculating, establish three-phase transformer turn ratio N ₁/ N ₂=2,

Calculate each secondary winding electric current corresponding electric current in winding:

${i_a}^{\′}=\frac{1}{2}\underset{n=\mathrm{1,5,7,11,13}...}{\overset{\∞}{\mathrm{\Σ}}}{\hat{I}}_n\sin (\mathrm{n\ωt}+{\mathrm{\φ}}_n)$

${i_{\tilde{a}}}^{\′}=\frac{1}{2}(\underset{n=\mathrm{1,7,13}...}{\overset{\∞}{\mathrm{\Σ}}}{\hat{I}}_n\sin (\mathrm{n\ωt}+{\mathrm{\φ}}_n+\mathrm{n\δ}+\frac{\mathrm{\π}}{6})+\underset{n=\mathrm{5,11}...}{\overset{\∞}{\mathrm{\Σ}}}{\hat{I}}_n\sin (\mathrm{n\ωt}+{\mathrm{\φ}}_n+\mathrm{n\δ}-\frac{\mathrm{\π}}{6}))$

Again

During n=7, $\mathrm{n\δ}+\frac{\mathrm{\π}}{6}=-\mathrm{\π};$ During n=5, $\mathrm{n\δ}-\frac{\mathrm{\π}}{6}=-\mathrm{\π}.$

Such 5,7 times, the harmonic wave of 17,19 inferior number of times is eliminated, and obtains:

${\mathrm{<figure-callout\; id="1"\; label="i\; A"\; filenames="HDA00002923875400032.png"\; state="\{\{state\}\}">i</figure-callout>}}_A=\underset{n=\mathrm{1,11,13,23,25}...}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\hat{I}}_n\sin (\mathrm{n\&omega;t}+{\mathrm{\&phi;}}_n)$

For negative pole 12 arteries and veins circuit, set suitable no-load voltage ratio, two secondary windings are with respect to three phase mains, and phase difference of voltage is respectively 45 ° of 15 ° of ﹣ and ﹣, the i.e. difference of output voltage phase angle and input voltage phase angle.For ease of analytical calculation, can regard as and added one-level in the common three-winding transformer front of positive pole to connect group number be DZ ₁, phase shifting angle is that 15 ° of δ=﹣, loss are 0 desirable phase shifting transformer.According to the phase shifting transformer principle, can be calculated

${\mathrm{<figure-callout\; id="2"\; label="i\; A"\; filenames="HDA00002923875400012.png"\; state="\{\{state\}\}">i</figure-callout>}}_A=\underset{n=\mathrm{1,13,25,37}...}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\hat{I}}_n\sin (\mathrm{n\&omega;t}+{\mathrm{\&phi;}}_n-\frac{(n-1)\mathrm{\&pi;}}{12})+\underset{n=\mathrm{11,23,35}...}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\hat{I}}_n\sin (\mathrm{n\&omega;t}+{\mathrm{\&phi;}}_n-\frac{(n+1)\mathrm{\&pi;}}{12})$

During n=13, $\frac{(n-1)\mathrm{\&pi;}}{12}=\mathrm{\&pi;};$ During n=11, $\frac{(n+1)\mathrm{\&pi;}}{12}=\mathrm{\&pi;};$ N=23 and 25 o'clock, $\frac{(n\&PlusMinus;1)\mathrm{\&pi;}}{12}=2\mathrm{\&pi;}.$

Total current: $i_A={\mathrm{<figure-callout\; id="1"\; label="i\; A"\; filenames="HDA00002923875400032.png"\; state="\{\{state\}\}">i</figure-callout>}}_A+{\mathrm{<figure-callout\; id="2"\; label="i\; A"\; filenames="HDA00002923875400012.png"\; state="\{\{state\}\}">i</figure-callout>}}_A=2\underset{n=\mathrm{1,23,25,47,49}...}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\hat{I}}_n\sin (\mathrm{n\&omega;t}+{\mathrm{\&phi;}}_n)$

Can see, adopting alternating current harmonic frequency after phase shifting transformer is 24n ± 1 time, and 11,13 subharmonic have obtained elimination, thereby have further reduced the THD of input current.

Set up bipolar 12 arteries and veins HVDC (High Voltage Direct Current) transmission system simulation models on the Matlab/Simulink platform, and phase shifting transformer has been applied to substitute in simulation model the three-phase three-winding transformer of negative pole.Adopt the front AC input current waveform of phase shifting transformer as shown in Figure 3, after the employing phase shifting transformer, the AC input current waveform as shown in Figure 4, can see that current waveform improves significantly.Electric current before and after the application phase shifting transformer is carried out spectrum analysis, result respectively as shown in Figure 5 and Figure 6, as seen the THD of input current is significantly reduced, only be left 23,25 times and 47,49 times with interior harmonic wave for 50 times, the harmonic wave of these times is because frequency is higher, the filter filtering can be adopted comparatively easily, filtering cost and filter volume can be greatly reduced.

Above demonstration and described basic principle of the present invention and principal character and advantage of the present invention.The technical staff of the industry should understand; the present invention is not restricted to the described embodiments; that describes in above-described embodiment and specification just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (4)

1. harmonic current restraining device in extra-high voltage DC transmission system, is characterized in that, comprising:

One AC system,

The power flow direction opposite side AC system of one top-cross streaming system,

A described top-cross streaming system connects the current conversion station that is operated in rectification state, is connected with converter after boosting by converter transformer, and alternating current is transformed to direct current,

Then after by DC power transmission line, direct current being transferred to current conversion station, the current conversion station that is operated in inverter mode is alternating current with dc inverter, and is connected with the opposite side AC system by after the converter transformer step-down.

2. harmonic current restraining device in extra-high voltage DC transmission system according to claim 1, it is characterized in that: the converter in described current conversion station adopts 4 bridges connect and be divided into two groups, the converter transformer of first group adopts common three-winding transformer, and the connection group number is YYD ₁₁The converter transformer of second group adopts phase shifting transformer, and its phase shifting angle is respectively-15 ° ,-45 °.

3. harmonic current restraining device in extra-high voltage DC transmission system according to claim 2, it is characterized in that: described three-winding transformer and phase shifting transformer, their equivalent impedance, voltage and power loss are identical.

4. harmonic current restraining device in extra-high voltage DC transmission system according to claim 2, it is characterized in that: an AC system is also received in the former limit of two groups of converter transformers in described current conversion station, and secondary is received respectively on a converter bridge.

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