CN106159950A - A kind of HVDC system harmonics instability suppressing method with Reactive-power control function - Google Patents

Abstract

The present invention provides a kind of HVDC system harmonics instability suppressing method with Reactive-power control function, comprises the following steps: judge whether to meet harmonic instability condition, if meeting, shnt capacitor on change of current bus；Reactive-power control is carried out by SVC in parallel on the change of current bus of HVDC system.The present invention is from harmonic instability mechanism of production, inverter AC impedance is changed by changing HVDC system frequency impedance operator, the former resonance point of HVDC system is made to deviate, meanwhile, utilize the characteristic of static passive compensation device, avoid HVDC system AC impedance to change the HVDC system reactive power and the change of voltage brought.

Description

A kind of HVDC system harmonics instability suppressing method with Reactive-power control function

Technical field

The invention belongs to high-voltage dc transmission electrical domain, be specifically related to a kind of HVDC system harmonics shakiness with Reactive-power control function Determine suppressing method.

Background technology

D.C. high voltage transmission (High Voltage Direct Current, HVDC) system has that transmission capacity is big, it is low, damp to be lost Stream flexible adjustment, change and intelligence degree advantages of higher fast and automatically, be the particularly important component units of strong intelligent grid it One.The feature of China's economic development and territory resource distribution is, Large-scale Coal base, Hydropower Base concentrate on northwest, northeast, Remote districts, southwest, the energy lacks, supply of electric power deficiency then embodies a concentrated reflection of economically developed east, Southern Coast area. These factors determine China and necessarily implement the electrical network strategy of " transferring electricity from the west to the east, north and south supply mutually, on national network ".High-voltage dc transmission Electricity, with the advantage of its uniqueness, plays the most important effect in remote power transmission and large-scale power grid interconnect.

Harmonic instability problem is one of typical challenge of being faced of HVDC transmission system.Owing to converter power transformer is saturated or The reasons such as complementary resonance, it would be possible to harmonic instability can be caused.Occur harmonic instability time, harmonic current will put several times greater very To tens times, the elements such as converter power transformer, reactor, capacitor are caused the biggest threat.Harmonic current is excessive also can cause electricity Pressure distortion, in turn results in commutation failure, makes DC transmission system run difficulty even locking.Under serious conditions, DC power transmission system The collapse of system is likely to result in the collapse of whole system.Therefore, the suppression tool for harmonic instability is of great significance.

At present, document [1] proposes to use secondary filter suppression harmonic instability also to change while eliminating AC second harmonic The frequency impedance of AC, increases smoothing reactor and is actually the harmonic wave damping of DC side；Document [2] is although proposing additional DC control can improve harmonic wave damping, but realize HVDC supplementary control and coordinate to control to be relatively difficult；Document [3] discusses Active filter application in HVDC transmission system, proposition employing active filter suppression harmonic instability, but based on Under the conditions of current technology, the engineer applied technology of high-voltage large-capacity active filter breaks through the most completely, safe and stable operation Level need to improve further, and involves great expense.

Pertinent literature

[1] Yang little Bing, Li Xingyuan, gold Xiao Ming, etc. in the wide extra-high voltage DC transmission system of cloud, converter transformer iron core is saturated not Stable suppression；

[2] KAULN, MATHURRM.Solution to the problem of low order harmonic resonance from HVDC converters；

[3] JIANGX, GOLEAM.An energy recovery filter for HVDC systems.

Summary of the invention

For the deficiency of above-mentioned harmonic instability suppressing method, the present invention provides a kind of HVDC system with Reactive-power control function Harmonic instability suppressing method, from harmonic instability mechanism of production, changes by changing HVDC system frequency impedance operator Inverter AC impedance, makes the former resonance point of HVDC system deviate, meanwhile, utilizes static passive compensation device Characteristic, avoids HVDC system AC impedance to change the HVDC system reactive power and the change of voltage brought.

In order to realize foregoing invention purpose, the present invention adopts the following technical scheme that:

The present invention provides a kind of HVDC system harmonics instability suppressing method with Reactive-power control function, described method include with Lower step:

Step 1: judge whether to meet harmonic instability condition, if meeting, shnt capacitor on change of current bus；

Step 2: carry out Reactive-power control by SVC in parallel on the change of current bus of HVDC system.

In described step 1, impedance frequency scanning method is first used to obtain inverter alternating current-direct current impedance scan result；Then judge whether Meet harmonic instability condition, if meeting, shnt capacitor on change of current bus, to change the resistance of HVDC system AC harmonic wave Anti-, make HVDC system deviate former resonance point.

Use impedance frequency scanning method to obtain alternating current-direct current impedance scan result to specifically include:

By the frequency impedance scan module of electromagnetic transients program PSCAD/EMTDC, HVDC system is carried out frequency to sweep Retouching, arrange the frequency sweeping ranges of 0～5000Hz, scanning step is set to 1Hz, obtains alternating current-direct current impedance scan result.

Described alternating current-direct current impedance scan result includes the impedance of inverter AC (n+1) secondary positive sequence harmonicInverter exchanges The impedance of side (n-1) secondary Negative sequence harmonicAnd Converter DC-side nth harmonic impedance Z_dcn。

Judge whether to meet following harmonic instability condition:

$\left(\right|Z_{\mathrm{ac}(n+1)}^{+}|+|Z_{\mathrm{ac}(n-1)}^{-}\left|\right)\≥\frac{{\mathrm{\π}}^2}{9}\left|Z_{\mathrm{dcn}}\right|$

Wherein,Represent the impedance of inverter AC (n+1) secondary positive sequence harmonic,Represent inverter AC (n-1) Secondary Negative sequence harmonic impedance, Z_dcnRepresent Converter DC-side nth harmonic impedance.

Capacitor minimum capacitance C in parallel on change of current bus is determined by following formula:

$\left|Z_{\mathrm{ac}(n+1)}^{+}\right||\left(\frac{1}{j{\mathrm{\&omega;}}_{(n+1)}C}\right)+Z_{\mathrm{ac}(n-1)}^{-}|\left|\left(\frac{1}{j{\mathrm{\&omega;}}_{(n-1)}C}\right)\right|<\frac{{\mathrm{\&pi;}}^2}{9}\left|Z_{\mathrm{dcn}}\right|$

Wherein, ω_(n+1)Represent inverter AC (n+1) secondary positive sequence harmonic angular frequency, ω_(n-1)Represent that inverter AC (n-1) is secondary Negative sequence harmonic angular frequency, Z_dcnRepresent Converter DC-side nth harmonic impedance.

In described step 2, SVC suppression HVDC system harmonics instability while, reach two-ways regulation without The function of merit power, to meet the voltage request of HVDC system.

Described SVC includes thyristor-controlled reactor TCR and thyristor switchable capacitor TSC, thyristor control Reactor TCR and thyristor switchable capacitor TSC is all connected in parallel on the change of current bus of HVDC system.

When change of current busbar voltage is less than the working voltage set, the idle amount compensated as required puts into the IGCT of respective sets number Switched capacitor TSC, and realize overcompensation capacitive reactive power, the sense of now recycling thyristor-controlled reactor TCR regulation output Property reactive power offset overcompensation capacitive reactive power；When change of current busbar voltage is higher than the working voltage set, then excise all brilliant locks Pipe switched capacitor TSC, only leaves thyristor-controlled reactor TCR and runs.

The capacity of the thyristor switchable capacitor TSC and thyristor-controlled reactor TCR of configuration determines that process is as follows:

Current conversion station reactive requirement Q_convIt is expressed as:

$Q_{\mathrm{conv}}={\mathrm{NI}}_d\frac{3\sqrt{2}{U}_{\mathrm{VO}}}{\mathrm{\&pi;}}\&CenterDot;\frac{2\mathrm{\&theta;}+2\sin \mathrm{\&alpha;}-\sin 2(\mathrm{\&alpha;}+\mathrm{\&theta;})}{4(\cos \mathrm{\&alpha;}-\cos (\mathrm{\&alpha;}+\mathrm{\&theta;}))}$

Wherein, the quantity of inverter during N is current conversion station；I_dFor DC line electric current；U_VOFor inverter AC non-loaded line electricity Pressure；α is Trigger Angle；θ is commutation overlap angle, is expressed as:

$\mathrm{\&theta;}=\arccos (\cos \mathrm{\&alpha;}-\frac{2X_r{I}_d}{\sqrt{2}{U}_{\mathrm{VO}}})-\mathrm{\&alpha;}$

Wherein, X_rFor commutating reactance；

If it is idle for Q that current conversion station median filter provides_filter, the capacity of suppression harmonic instability shunt capacitance is Q_C, then configure The capacity Q of thyristor switchable capacitor TSC_TSCFor:

Q_TSC=Q_conv-Q_filter-Q_C

If thyristor switchable capacitor TSC is divided into M group, then the capacity of the thyristor-controlled reactor TCR configured represents For:

Q_TCR=Q_TSC/M

Wherein, Q_TCRCapacity for thyristor-controlled reactor TCR.

Described thyristor-controlled reactor TCR includes the first reactor L1 and the first IGCT assembly, described first thyristor groups Part includes antiparallel IGCT T1 and IGCT T2；Described first IGCT assembly one end is connected to by the first reactor L1 On change of current bus, other end ground connection.

Thyristor switchable capacitor TSC includes compensating electric capacity C1, the second reactor L2 and the second IGCT assembly, and described second IGCT assembly includes antiparallel IGCT T3 and IGCT T4；One end of described compensation electric capacity C1 is connected on change of current bus, The other end is crossed the second reactor L2 and is connected the second IGCT assembly, the second IGCT assembly other end ground connection.

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

The HVDC system harmonics instability suppressing method with Reactive-power control function that the present invention provides, from harmonic instability mechanism Set out, reach the purpose of harmonics restraint by changing HVDC system frequency impedance operator, give suppression harmonic instability also Connection capacitor minimum capacitance determines, avoids inverter change of current bus AC impedance by installing SVC additional simultaneously Change the HVDC system reactive power and the change of voltage brought, maintain balance and the bus of HVDC system reactive power Stablizing of voltage.

Accompanying drawing explanation

Fig. 1 is for suppressing the SVC structural representation of harmonic wave in the embodiment of the present invention；

Fig. 2 is HVDC system topology figure in the embodiment of the present invention；

Fig. 3 is DC voltage waveform figure after the HVDC system failure in the embodiment of the present invention；

Fig. 4 is change of current bus AC second harmonic oscillogram after the HVDC system failure in the embodiment of the present invention；

Fig. 5 is to add HVDC system frequency impedance scan figure after capacitor in the embodiment of the present invention；

Fig. 6 is the comparison of HVDC system change of current bus AC positive sequence harmonic impedance before and after addition capacitor in the embodiment of the present invention Figure；

Fig. 7 is to add HVDC system change of current bus DC voltage oscillogram after capacitor in the embodiment of the present invention；

Fig. 8 is to add HVDC system change of current bus AC second harmonic oscillogram after capacitor in the embodiment of the present invention；

HVDC System Reactive Power oscillogram when Fig. 9 is to be not powered on container in the embodiment of the present invention；

Figure 10 is to add HVDC System Reactive Power oscillogram after capacitor in the embodiment of the present invention；

Figure 11 is to add HVDC system change of current bus DC side electricity after capacitor and SVC in the embodiment of the present invention Corrugating figure；

Figure 12 is to add HVDC system change of current bus AC two after capacitor and SVC in the embodiment of the present invention Secondary impedance oscillogram；

Figure 13 is to add HVDC System Reactive Power oscillogram after capacitor and SVC in the embodiment of the present invention；

Figure 14 is that in the embodiment of the present invention, SVC absorbs idle oscillogram.

Detailed description of the invention

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

The HVDC system harmonics instability suppressing method with Reactive-power control function that the present invention provides, on the one hand by change be The mode of system AC network structure changes system frequency impedance operator, so that system deviates original resonance point, reaches harmonic wave not The purpose of stabilization checking；On the other hand, utilize reactive power compensator characteristic, it is to avoid system AC impedance change the system brought without Merit power and the change of voltage.

In order to verify that harmonic instability is suppressed and the effectiveness of idle dual regulation by the present invention, in electromagnetic transient simulation journey Sequence (PSCAD/EMTDC) carries out Harmonic simulation analysis to HVDC system.

Building the HVDC system containing only direct-flow inverter, replaced by rectification side current source, inverter side controls as CIGRE inverse Become side to control, as shown in Figure 2.Each parameter of HVDC system is as shown in table 1:

Table 1

Parameter	Numerical value
		Resistance R1 [ohm]	50
Resistance R2 [ohm]	100
		Resistance R3 [ohm]	1
Electric capacity C1 [μ F]	1000
		Electric capacity C2 [μ F]	397.49
Electric capacity C3 [μ F]	22.066
		Inductance L1 [mH]	6.347
Inductance L2 [mH]	600
		Inductance L3 [mH]	918
DC voltage [kV]	500
		AC voltage [kV]	230

Assume that being engraved in the change of current bus AC A point during 2s occurs three-phase shortcircuit, persistent period 0.1s, its DC voltage emulation ripple Shape as it is shown on figure 3, change of current bus AC voltage second harmonic oscillogram as shown in Figure 4.

As seen from Figure 3, after 2s fault, DC voltage amplifies, and Severe distortion occurs, and change of current bus AC secondary is humorous Wave voltage vibration cannot decay, and as shown in Figure 4, therefore judges HVDC system generation harmonic instability.

Capacitor minimum capacitance C in parallel on change of current bus is determined by following formula:

$\left|Z_{\mathrm{ac}(n+1)}^{+}\right||\left(\frac{1}{j{\mathrm{\&omega;}}_{(n+1)}C}\right)+Z_{\mathrm{ac}(n-1)}^{-}|\left|\left(\frac{1}{j{\mathrm{\&omega;}}_{(n-1)}C}\right)\right|<\frac{{\mathrm{\&pi;}}^2}{9}\left|Z_{\mathrm{dcn}}\right|$

Wherein, ω_(n+1)Represent inverter AC (n+1) secondary positive sequence harmonic angular frequency, ω_(n-1)Represent that inverter AC (n-1) is secondary Negative sequence harmonic angular frequency, Z_dcnRepresent Converter DC-side nth harmonic impedance；Solve C=34.43 μ F, system 34.43 μ F in parallel Capacitor after frequency impedance scanning figure as shown in Figure 5.

Consider economic factor and the principle on the impact of HVDC system reactive power, therefore for HVDC system 34.5 μ F's in parallel Capacitor, after adding the capacitor of 34.5 μ F, makes HVDC system resonance point offset, and HVDC system frequency impedance scan is such as Shown in Fig. 6.Fig. 6 is embodied as HVDC system frequency impedance scan value, it can be seen that its resonance point is about 100Hz；Dotted line For HVDC system frequency impedance scan value after shnt capacitor, it can be seen that its resonance point there occurs skew, and its frequency is hindered Anti-harmonic instability criterion of bringing into, now,Show that HVDC system will not occur Harmonic instability.Wherein,Represent change of current bus AC (n+1) secondary positive sequence harmonic impedance,Represent that the change of current is female The impedance of line AC (n-1) secondary Negative sequence harmonic, Z_dcnRepresent n the positive sequence harmonic impedance of change of current bus DC side.

After the capacitor of 34.5 μ F in parallel, there is not harmonic instability in HVDC system, its change of current bus AC secondary is humorous Wave voltage and change of current bus DC voltage waveform are the most as shown in Figure 7, Figure 8.

But, add 34.5 μ F shnt capacitors and change the reactive power that HVDC system is original, shown in Fig. 9 and Figure 10, Before the capacitor of 34.5 μ F in parallel, change of current bus AC reactive power is about 30MVar, after the capacitor of 34.5 μ F in parallel, Change of current bus AC reactive power is about 530MVar, before and after 34.5 μ F in parallel, and the reactive power that change of current bus AC flows through There occurs significantly change.

When only adding capacitor, change HVDC system AC equivalent impedance, can reach to suppress the effect of harmonic instability, But make that AC is idle to be significantly increased.To this end, SVC can be added to balance reactive power.Add static nothing Merit compensator maintains reactive balance.After adding TCR+TSC type SVC and the circuit of shunt capacitance, system does not occurs Harmonic instability, its change of current bus AC second harmonic and change of current bus DC voltage waveform are respectively such as Figure 11, Tu12Suo Show.

Now on change of current bus AC idle change as shown in figure 13, before not adding this circuit, HVDC system change of current bus The reactive power that AC flows through is about 530MVar, adds the electricity of TCR+TSC type SVC and shunt capacitance Lu Hou, the reactive power that its change of current bus AC flows through is about 370MVar, TCR+TSC type SVC with in parallel The circuit of electric capacity serves the effect of good absorption reactive power, and absorbs about 148MVar reactive power, as shown in figure 14.

From above-described embodiment it can be seen that the present invention can realize the suppression of harmonic instability with relatively low value capacitor, simultaneously can Carry out the two-ways regulation of reactive power, the requirement idle to meet HVDC system voltage.

Finally should be noted that: above example only in order to illustrate that technical scheme is not intended to limit, art Those of ordinary skill still the detailed description of the invention of the present invention can be modified or equivalent with reference to above-described embodiment, These are without departing from any amendment of spirit and scope of the invention or equivalent, the claim of the present invention all awaited the reply in application Within protection domain.

Claims (12)

1. a HVDC system harmonics instability suppressing method with Reactive-power control function, it is characterised in that: described method Comprise the following steps:

Step 1: judge whether to meet harmonic instability condition, if meeting, shnt capacitor on change of current bus；

Step 2: carry out Reactive-power control by SVC in parallel on the change of current bus of HVDC system.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 1, it is special Levy and be: in described step 1, first use impedance frequency scanning method to obtain inverter alternating current-direct current impedance scan result；Then judge Whether meet harmonic instability condition, if meeting, shnt capacitor on change of current bus, humorous to change HVDC system AC Natural impedance, makes HVDC system deviate former resonance point.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 2, it is special Levy and be: use impedance frequency scanning method to obtain alternating current-direct current impedance scan result and specifically include:

By the frequency impedance scan module of electromagnetic transients program PSCAD/EMTDC, HVDC system is carried out frequency to sweep Retouching, arrange the frequency sweeping ranges of 0～5000Hz, scanning step is set to 1Hz, obtains alternating current-direct current impedance scan result.

4. according to the HVDC system harmonics instability suppressing method with Reactive-power control function described in Claims 2 or 3, It is characterized in that: described alternating current-direct current impedance scan result includes the impedance of inverter AC (n+1) secondary positive sequence harmonicChange Stream device AC (n-1) secondary Negative sequence harmonic impedanceAnd Converter DC-side nth harmonic impedance Z_dcn。

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 1, it is special Levy and be: judge whether to meet following harmonic instability condition:

$\left(\right|Z_{\mathrm{ac}(n+1)}^{+}|+|Z_{\mathrm{ac}(n-1)}^{-}\left|\right)\&GreaterEqual;\frac{{\mathrm{\&pi;}}^2}{9}\left|Z_{\mathrm{dcn}}\right|$

Wherein,Represent the impedance of inverter AC (n+1) secondary positive sequence harmonic,Represent inverter AC (n-1) Secondary Negative sequence harmonic impedance, Z_dcnRepresent Converter DC-side nth harmonic impedance.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 1 and 2, It is characterized in that: capacitor minimum capacitance C in parallel on change of current bus is determined by following formula:

$\left|Z_{\mathrm{ac}(n+1)}^{+}\right||\left(\frac{1}{j{{\mathrm{\&omega;}}_{(n+1)}}^C}\right)+Z_{\mathrm{ac}(n-1)}^{-}|\left|\left(\frac{1}{j{{\mathrm{\&omega;}}_{(n-1)}}^C}\right)\right|<\frac{{\mathrm{\&pi;}}^2}{9}\left|Z_{\mathrm{dcn}}\right|$

Wherein, ω_(n+1)Represent inverter AC (n+1) secondary positive sequence harmonic angular frequency, ω_(n-1)Represent that inverter AC (n-1) is secondary Negative sequence harmonic angular frequency, Z_dcnRepresent Converter DC-side nth harmonic impedance.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 1, it is special Levying and be: in described step 2, SVC, while suppression HVDC system harmonics instability, reaches two-way tune The function of joint reactive power, to meet the voltage request of HVDC system.

8. according to the HVDC system harmonics instability suppressing method with Reactive-power control function described in claim 1 or 7, It is characterized in that: described SVC includes thyristor-controlled reactor TCR and thyristor switchable capacitor TSC, brilliant Brake tube controls reactor TCR and thyristor switchable capacitor TSC and is all connected in parallel on the change of current bus of HVDC system.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 8, it is special Levy and be: when change of current busbar voltage is less than the working voltage set, the idle amount compensated as required puts into the crystalline substance of respective sets number Brake tube switched capacitor TSC, and realize overcompensation capacitive reactive power, now recycling thyristor-controlled reactor TCR regulation output Lagging reactive power offset overcompensation capacitive reactive power；When change of current busbar voltage is higher than the working voltage set, then excision is all Thyristor switchable capacitor TSC, only leaves thyristor-controlled reactor TCR and runs.

The HVDC system harmonics instability suppressing method with Reactive-power control function the most according to claim 9, it is special Levy and be: the capacity of the thyristor switchable capacitor TSC and thyristor-controlled reactor TCR of configuration determines that process is as follows:

Current conversion station reactive requirement Q_convIt is expressed as:

$Q_{\mathrm{conv}}={\mathrm{NI}}_d\frac{3\sqrt{2}{U}_{\mathrm{VO}}}{\mathrm{\&pi;}}\&CenterDot;\frac{2\mathrm{\&theta;}+2\sin \mathrm{\&alpha;}-\sin 2(\mathrm{\&alpha;}+\mathrm{\&theta;})}{4(\cos \mathrm{\&alpha;}-\cos (\mathrm{\&alpha;}+\mathrm{\&theta;}))}$

Wherein, the quantity of inverter during N is current conversion station；I_dFor DC line electric current；U_VOFor inverter AC non-loaded line electricity Pressure；α is Trigger Angle；θ is commutation overlap angle, is expressed as:

$\mathrm{\&theta;}=\arccos (\cos \mathrm{\&alpha;}-\frac{2X_r{I}_d}{\sqrt{2}{U}_{\mathrm{VO}}})-\mathrm{\&alpha;}$

Wherein, X_rFor commutating reactance；

If it is idle for Q that current conversion station median filter provides_filter, the capacity of suppression harmonic instability shunt capacitance is Q_C, then configure The capacity Q of thyristor switchable capacitor TSC_TSCFor:

Q_TSC=Q_conv-Q_filter-Q_C

If thyristor switchable capacitor TSC is divided into M group, then the capacity of the thyristor-controlled reactor TCR configured represents For:

Q_TCR=Q_TSC/M

Wherein, Q_TCRCapacity for thyristor-controlled reactor TCR.

The 11. HVDC system harmonics instability suppressing method with Reactive-power control function according to claim 8, it is special Levy and be: described thyristor-controlled reactor TCR includes the first reactor L1 and the first IGCT assembly, the described first brilliant lock Pipe assembly includes antiparallel IGCT T1 and IGCT T2；The first reactor L1 is passed through in described first IGCT assembly one end It is connected on change of current bus, other end ground connection.

The 12. HVDC system harmonics instability suppressing method with Reactive-power control function according to claim 8, it is special Levy and be: thyristor switchable capacitor TSC includes compensating electric capacity C1, the second reactor L2 and the second IGCT assembly, described Second IGCT assembly includes antiparallel IGCT T3 and IGCT T4；It is female that one end of described compensation electric capacity C1 is connected to the change of current On line, the other end is crossed the second reactor L2 and is connected the second IGCT assembly, the second IGCT assembly other end ground connection.