CN104052076B - A kind of method estimating direct current sending end islanded system parallel resonance frequency - Google Patents

Abstract

The present invention is a kind of method estimating direct current sending end islanded system parallel resonance frequency.Comprise the following steps: 1) set up AC network calculation of short-circuit current data in islanded system；2) capacity of short circuit of change of current bus is calculated；3) current conversion station reactive compensation capacity, line charging reactive capability are calculated；4) according to fundamental frequency, AC system capacity of short circuit, current conversion station reactive compensation capacity, line charging reactive power estimation parallel resonance frequency numerical value.The method of the present invention considers the charging capacitor of circuit when resonant frequency is estimated, is more nearly practical situation, therefore assesses the resonant frequency obtained more accurate.

Description

A kind of method estimating direct current sending end islanded system parallel resonance frequency

Technical field

The invention belongs to power system computation analysis field, relate to a kind of electrical network parallel resonance frequency evaluation method, more Body relates to a kind of method considering line charging idle estimation direct current sending end islanded system parallel resonance frequency, belongs to estimation straight The innovative technology of the method for streaming end islanded system parallel resonance frequency.

Background technology

High pressure and extra-high voltage direct-current transmission technology are due to its technology and economic traits, in remote, the large capacity transmission To extensively application.The capacity of DC transmission engineering is generally large, and direct current locking fault occurs in networking operation, and dc power will turn Move on to the communication channel of parallel running, cause the risk of system unstability, need safety stabilization control system to take to cut machine cutting load Measure guarantees stable so that safety stabilization control system degree of dependence is increased by operation of power networks day by day.Additionally, DC online fortune OK, for ensureing that direct current one pole locking post-fault system is stable, the communication channel trend of parallel running needs reserved bigger nargin, uses In the power accepting direct current one pole locking transfer.

Direct current islet operation is possible not only to dissolve DC bipolar block and surely controls tripping or the multiple-circuit line event of one pole locking simultaneously Barrier causes the risk of system unstability, and can discharge the nargin of parallel running communication channel, improves AC-HVDC passage total Ability to transmit electricity.Therefore, increasing DC transmission engineering all using sending end islet operation as one of its normal operating mode, To reduce system safety hazards.

But, under DC transmission system sending end decoupled mode, AC system is the most weak, capacity of short circuit and short-circuit ratio Low, current conversion station is configured with substantial amounts of reactive-load compensation equipment simultaneously, there is inductive element and capacitive element under certain condition and send out The risk of raw parallel resonance.Directive/guide " the IEEEguide forplanningDClinksterminatingatAClocati of IEEE Onshavinglow short-circuitcapacities " propose resonant frequency evaluation method as follows:

$f_{\mathrm{res}}=f_1\×\sqrt{\frac{S_{\mathrm{AD}}}{Q_{\mathrm{Filter}}}}$

Wherein, f₁For fundamental frequency, S_ACFor the capacity of short circuit of AC system, Q at change of current bus_FilterNothing for current conversion station Merit compensation capacity.

Its theoretical foundation is when frequency reachesTime, the impedance phase of impedance and the capacitive of perception in system Deng, reach parallel resonance condition.

But it practice, the circuit in islanded system is constantly present certain ground connection susceptance, sends capacitive reactive power, therefore examine Should take into account idle for the charging of circuit during the capacitive reactances of worry system；When AC system capacity of short circuit calculates simultaneously, meter The charging that the capacity of short circuit of the capacity of short circuit obtained perception system often deducts circuit is idle, the therefore perception of real system Capacity should be calculated capacity of short circuit and the idle sum of line charging.

In sum, when estimating direct current sending end islanded system resonant frequency, it should consider the effect that line charging is idle.

Summary of the invention

The purpose of the present invention is to propose to a kind of method estimating direct current sending end islanded system parallel resonance frequency.The present invention is A kind of method considering line charging idle estimation direct current sending end islanded system parallel resonance frequency, at direct current sending end islanded system During resonant frequency estimation, it is considered to the impact that line charging is idle, thus it is actual to be more nearly system, improves the accurate of computational analysis Property.

To achieve these goals, the present invention adopts the following technical scheme that

The present invention estimates the method for direct current sending end islanded system parallel resonance frequency, at estimation direct current sending end islanded system also During connection resonant frequency, it is contemplated that the impact that line charging is idle.

The present invention estimates the method for direct current sending end islanded system parallel resonance frequency, comprises the following steps:

1) set up AC network calculation of short-circuit current data in islanded system, wherein count line charging idle, but Do not include current conversion station reactive-load compensation；

2) capacity of short circuit S of change of current bus is calculated_AC；

3) current conversion station reactive compensation capacity Q is calculated according to current conversion station reactive-load compensation equipment parameter_Filter, each according to current conversion station Return back out idle total capacity Q of charging of the route parameter calculation circuit of line_Line；

4) according to fundamental frequency, AC system capacity of short circuit, current conversion station reactive compensation capacity, line charging reactive power, Estimation parallel resonance frequency numerical value as follows:

$f_{\mathrm{res}}=f_1\×\sqrt{\frac{S_{\mathrm{AD}}+K\×Q_{\mathrm{Line}}}{Q_{\mathrm{Filter}}+K+Q_{\mathrm{Line}}}}$

Wherein f_resFor resonant frequency, f₁For fundamental frequency, K is proportionality coefficient.

Above-mentioned steps 1) in AC network calculation of short-circuit current data include electromotor, transformator, track data.

Above-mentioned steps 4) in Proportional coefficient K take 0～1.

The present invention is a kind of method considering line charging idle estimation direct current sending end islanded system parallel resonance frequency, During the estimation of direct current sending end islanded system resonant frequency, it is considered to the impact that line charging is idle, thus it is actual to be more nearly system, carries The accuracy of high computational analysis.The present invention is the side of a kind of convenient and practical estimation direct current sending end islanded system parallel resonance frequency Method.

Accompanying drawing explanation

Fig. 1 is the implementing procedure figure of the inventive method.

Tu2Shi south electric network Chu Sui direct current sending end islanded system mode schematic diagram.

Fig. 3 is the harmonic impedance-frequency curve of system shown in Figure 2.

Detailed description of the invention

The method considering line charging idle estimation direct current sending end islanded system parallel resonance frequency that the present invention proposes, tool Below the embodiment of body:

1) in the Power System Analysis programs such as BPA or PSS/E, AC network calculation of short-circuit current in islanded system is set up By data, the data such as including electromotor, transformator, circuit, wherein count line charging idle, but do not included that current conversion station is idle Compensate；

2) the Power System Analysis programs such as BPA or PSS/E are used to calculate capacity of short circuit S of change of current bus_AC；

3) current conversion station reactive compensation capacity Q is calculated according to current conversion station reactive-load compensation equipment parameter_Filter, each according to current conversion station Return back out idle total capacity Q of charging of the route parameter calculation circuit of line_Line；

4) according to fundamental frequency, AC system capacity of short circuit, current conversion station reactive compensation capacity, line charging reactive power, Estimation parallel resonance frequency numerical value as follows:

$f_{\mathrm{res}}=f_1\×\sqrt{\frac{S_{\mathrm{AD}}+K\×Q_{\mathrm{Line}}}{Q_{\mathrm{Filter}}+K+Q_{\mathrm{Line}}}}$

Wherein f_resFor resonant frequency, f₁For fundamental frequency, K is proportionality coefficient, desirable 0～1.

Evaluation method provided by the present invention has obtained effectively under south electric network Chu Sui direct current sending end decoupled mode Checking.

As a example by the Chu Sui direct current sending end islanded system method of operation shown in Fig. 2, it is considered to f₁=50Hz, is calculated S_AC =5805MVA, Q_Line=911MVA, when current conversion station puts into 14 groups of idle groups, Q_Filter=2618MVA, takes K=1, by upper State step and be calculated resonant frequency and be:

$f_{\mathrm{res}}=f_1\×\sqrt{\frac{S_{\mathrm{AD}}+K\×Q_{\mathrm{Line}}}{Q_{\mathrm{Filter}}+K+Q_{\mathrm{Line}}}}=50\×\sqrt{\frac{5805+911}{2618+911}}=68.98\mathrm{Hz}$

Which is carried out harmonic impedance scanning, and the harmonic impedance-frequency curve obtained is as shown in Figure 3, it is seen that resonance frequency Rate about 69Hz, basically identical with estimation result.

Claims (3)

1. the method estimating direct current sending end islanded system parallel resonance frequency, humorous in estimation direct current sending end islanded system parallel connection During vibration frequency, it is contemplated that the impact that line charging is idle, it is characterised in that estimation direct current sending end islanded system parallel resonance frequency Method comprise the following steps:

1) set up AC network calculation of short-circuit current data in islanded system, wherein counted line charging idle, but do not wrapped Include current conversion station reactive-load compensation；

2) capacity of short circuit S of change of current bus is calculated_AC；

3) current conversion station reactive compensation capacity Q is calculated according to current conversion station reactive-load compensation equipment parameter_Filter, respectively return back out according to current conversion station Idle total capacity Q of charging of the route parameter calculation circuit of line_Line；

4) according to fundamental frequency, AC system capacity of short circuit, current conversion station reactive compensation capacity, line charging reactive power, by with Lower formula estimation parallel resonance frequency numerical value

Wherein f_resFor resonant frequency, f₁For fundamental frequency, K is proportionality coefficient.

2. according to the method for the estimation direct current sending end islanded system parallel resonance frequency described in claim 1, it is characterised in that Above-mentioned steps 1) in AC network calculation of short-circuit current data include electromotor, transformator, track data.

3. according to the method for the estimation direct current sending end islanded system parallel resonance frequency described in claim 1, it is characterised in that Above-mentioned steps 4) in Proportional coefficient K take 0～1.