A kind of UPFC connection in series-parallel transverter for improving ac bus voltage support intensity coordinates control
System strategy
Technical field
The invention belongs to Power System Flexible transmission & distribution electro-technical field, and in particular to one kind improves ac bus voltage support
The UPFC connection in series-parallel transverter coordination control strategies of intensity.
Background technology
China's energy resources and the contrary distribution characteristic of load determine the basic configuration of " transferring electricity from the west to the east, NORTEL south are sent ";
Suitable for remote, large capacity transmission UHV transmission technology, for realize the reasonable development of china natural resources, distribute rationally, it is high
Effect is using there is provided a kind of effective solution.However, UHV Transmission Engineering is realizing the same of remote, large capacity transmission
When, new challenge is also brought to the safe and stable operation of power network;Build quasi- east-East China extra-high voltage direct-current voltage class ±
1100KV, the single specified feed-in power of direct current reaches 12000MW, the concentration feed-in of extensive power to the control of receiving end electric network swim and
Voltage support ability brings huge challenge.
THE UPFC (Unified PowerFlow Controller, UPFC) is handed over as the flexibility of latest generation
Transmission system (FlexibleAC Transmission System, FACTS) device is flowed, the accurate control of trend can either be realized
System, has voltage regulation capability again, to solve the problems, such as that electric network swim control and voltage support are provided after extra-high voltage access system
A kind of comprehensive solution.UPFC is made up of two back-to-back voltage source converters, and two back-to-back transverters are total to
With dc bus and DC capacitor, the two is all by converter power transformer access system, and wherein parallel inverter passes through change of current transformation
Device is accessed with parallel form, and series connection transverter is accessed by converter power transformer with cascade, as shown in figure 1, UPFC generally has 3
Individual system-level control dimension, i.e. transmission line of electricity be active/Reactive Power Control of reactive power flow control and parallel inverter.
In the research of line voltage enabling capabilities is improved using FACTS devices, the FACTS dresses of parallel connection type are generally only considered
Put, the research for tandem type FACTS device Reactive-power control abilities is less;To ensure the safe and stable operation of power system, remove
Need dynamic reactive support outer, in addition it is also necessary to configure a large amount of capacitor banks and carry out static reactive power compensations.Nothing in traditional operation of power networks
The uncontrollability of work(trend, idle configuration and the unbalanced of demand will cause electric network reactive-load skewness to weigh, and cause static reactive
Compensation device can not be fully utilized;UPFC reactive power flow control ability can accurate control circuit reactive power flow, it is right
Improve System Reactive Power skewness weighing apparatus, solve the problem of regional area reactive power support is not enough after N-1 failures there is provided a kind of means.
In order to make full use of UPFC voltage regulation capability, system voltage support strength is improved to greatest extent, it should utilized simultaneously
The reactive voltage regulating power of UPFC series and parallel transverters, but simultaneously using UPFC series and parallels transverter to ac bus voltage
The coordination being controlled without considering the two, will cause UPFC series and parallels transverter mutually to fight for idle controlled quentity controlled variable, it is impossible to it is determined that
Steady-state operation point.
As seen from the above analysis, how to make full use of the idle control ability of UPFC series and parallel transverters, coordinate UPFC strings
Relation between connection and the idle controlled quentity controlled variable of parallel inverter, the voltage support intensity to improving ac bus to greatest extent is protected
Demonstrate,proving the safe and stable operation of power system has very positive effect.
The content of the invention
In view of above-mentioned, the present invention proposes a kind of UPFC connection in series-parallel transverter association for improving ac bus voltage support intensity
Control strategy is adjusted, UPFC series connection transverter reactive power flow command values and parallel connection can be automatically adjusted when ac bus voltage out-of-limit
Transverter reactive power command value, by alternating voltage control in the range of safe and stable operation, improves exchange female to greatest extent
The voltage support intensity of line.
A kind of UPFC connection in series-parallel transverter coordination control strategies for improving ac bus voltage support intensity, including following step
Suddenly:
(1) the voltage magnitude V of controlled ac bus node is calculatedacWith respect to UPFC series side transverter reactive power flow command values
QL *The susceptibility A of changeacAnd relative UPFC parallel connections side transverter reactive power command value Qsh *The susceptibility B of changeac;
(2) according to the susceptibility AacAnd BacThe voltage out-of-limit for calculating correspondence UPFC series sides and side in parallel transverter is inclined
Difference signal Δ RseWith Δ Rsh;
(3) when detecting Δ Rse≠ 0 or Δ Rsh≠ 0 i.e. controlled ac bus node voltage is out-of-limit, then passes through ac bus
Voltage traffic signal coordination generates the reactive power flow Regulate signal Δ Q of UPFC series side transvertersLAnd the UPFC side changes of current in parallel
The reactive power Regulate signal Δ Q of devicesh;
(4) the given UPFC series side transverter reactive power flow command values Q of control centre under nominal situation is madeL0And UPFC
Side transverter reactive power command value Q in parallelsh0Respectively with reactive power flow Regulate signal Δ QLWith reactive power Regulate signal Δ Qsh
It is superimposed, obtain final reactive power flow command value QL *With reactive power command value Qsh *;And then by QL *And Qsh *It is separately input into
The Reactive Power Control module of the reactive power flow control module and UPFC of UPFC series side transverters side transverter in parallel, as
UPFC control instruction is to be controlled.
Further, susceptibility A is calculated by below equation in the step (1)acAnd Bac:
Aac=-j (Zmy-Zmx)
Bac=-jZmx
Wherein:ZmxFor m row xth column elements, Z in matrix ZmyFor m row y column elements in matrix Z, x and y are respectively
The numbering and electric current positive direction that circuit two ends bus nodes are installed where UPFC flow to y from x, and m is controlled ac bus node
Numbering, Z is the inverse matrix of network system bus admittance matrix, and j is imaginary unit.
Further, voltage out-of-limit deviation signal Δ R is calculated by below equation in the step (2)seWith Δ Rsh:
ΔRse=-Δ VacSgn(Aac)
ΔRsh=Δ VacSgn(Bac)
ΔVac=max (Vac-Vac,max,0)+min(Vac-Vac,min,0)
Wherein:Vac,maxAnd Vac,minRespectively it is controlled the operational voltage upper limit value and lower limit of ac bus node, Sgn ()
It is sign function i.e. when the independent variable in () >=0, functional value is 1;As the independent variable < 0 in (), functional value is -1.
Further, generation reactive power flow Regulate signal Δ Q is calculated by below equation in the step (3)LWith it is idle
Power regulating signals Δ Qsh:
Wherein:KseAnd KshIt is the gain amplifier coefficient of setting, DseAnd DshIt is the droop control coefficient of setting, s is drawing
General Laplacian operater.
Further, the droop control coefficient DseWith DshRatio be equal to | Bac| with | Aac| ratio.
UPFC connection in series-parallel transverter coordination control strategy of the present invention is female by monitoring controlled exchange during operation of power networks
The amplitude of line voltage, reflection ac bus voltage is calculated when ac bus voltage out-of-limit and gets over the characteristic signal of thread degree, and is led to
Cross ac bus voltage traffic signal coordination automatically adjust UPFC series connection transverter reactive power flow command value and parallel inverter without
Work(power command value, to greatest extent using the system-level regulating powers of UPFC, by alternating voltage control in safe and stable operation model
In enclosing.As can be seen here, the present invention supports problem to solve line voltage after extra-high voltage access system, improves system to greatest extent
Dynamic/quiescent voltage enabling capabilities provide a kind of effective means.
Brief description of the drawings
Fig. 1 is THE UPFC UPFC structural representation.
Fig. 2 is the NETWORK STRUCTURE PRESERVING POWER SYSTEM schematic diagram containing UPFC.
Fig. 3 is the control block diagram of ac bus voltage tuning controller of the present invention.
Fig. 4 is the rough schematic view of a certain actual electric network system.
Fig. 5 is the voltage response curves figure that nature trend is distributed lower and control strategy Down Highway 3 of the present invention.
Fig. 6 is that nature trend is distributed 2-1 line reactive powers and UPFC parallel inverters under control strategy lower and of the present invention
The response curve that output is idle.
Embodiment
In order to more specifically describe the present invention, below in conjunction with the accompanying drawings and embodiment is to technical scheme
It is described in detail.
The present invention is used for the UPFC connection in series-parallel transverter coordination control strategies for improving ac bus voltage support intensity, including
Following steps:
(1) controlled ac bus voltage magnitude V is calculatedacTo UPFC series side transverter reactive power flow command values QL *And
Side transverter reactive power command value Q in parallelsh *The susceptibility of change, specific method is as follows:
For a power system containing a ac bus, it is assumed that the numbering of controlled ac bus in systems is m,
UPFC parallel connection side joints enter bus 1, and UPFC series sides are arranged between bus 1 and 2, as shown in Figure 2.Matrix Z is radio network node
The inverse matrix of admittance matrix, its i-th row jth column element is Zij(i, j=1,2 ..., a);It can be obtained according to electric network theory, the quilt
Control busbar voltage amplitude VacTo UPFC series side transverter reactive power flow command values QL *And side in parallel transverter reactive power refers to
Make value Qsh *The susceptibility A of changeacAnd BacCalculation formula it is as follows:
Aac=-j (Zm2-Zm1)
Bac=-jZm1
The value of overhead transmission line resistance is much smaller than its reactance value in actual power transmission network, compared to imaginary part, ZijReal part can be with
Ignore.Meanwhile, UPFC installs the voltage phasor phase angle of ac bus near circuit relatively, and amplitude is all near 1.0pu.
On this condition, the controlled busbar voltage amplitude VacWith UPFC series side transverter reactive power flow command values QL *Variable quantity and
Side transverter reactive power command value Q in parallelsh *The relation of variable quantity is:
It can be seen that AacAnd BacReflect controlled busbar voltage amplitude VacTo UPFC series side transverter reactive power flow command values QL *
And parallel connection side transverter reactive power command value Qsh *The susceptibility of change.
(2) controlled ac bus voltage magnitude V is monitored on-lineacAnd calculate to generate UPFC series and parallels side transverter without
The voltage out-of-limit deviation signal Δ R of work(command valuese、ΔRsh;When detecting Δ Rse≠ 0 or Δ Rsh≠ 0, that is, it is controlled ac bus
During voltage out-of-limit, UPFC series side transverter reactive power flow command values Q is generated by ac bus voltage tuning controllerL *Tune
Save signal delta QLAnd parallel connection side transverter reactive power command value Qsh *Regulate signal Δ Qsh。
Ac bus voltage tuning controller is as shown in figure 3, wherein Kse、KshRespectively UPFC series and parallels transverter is exchanged
The amplifier gain of busbar voltage controller, Dse、DshThe respectively voltage-controlled sagging control of series and parallel transverter ac bus
Coefficient processed, s is Laplace operator.Error signal Δ RseWith output signal Δ QLFeedback signal DseΔQLBy product after superposition
The Regulate signal Δ Q of UPFC series side reactive power flow command values is obtained after point linkL;Error signal Δ RshWith output signal Δ
Qsh feedback signal DshΔQshThe regulation letter of UPFC side reactive power command values in parallel is obtained after superposition after integral element
Number Δ Qsh, i.e.,:
Distribution of the reactive power/voltage control amount between series and parallel transverter can be exchanged by changing series and parallel transverter
The droop control coefficient D of busbar voltage controlseAnd Dsh, it is allocated according to previously given distribution principle.Present embodiment is pressed
UPFC series sides transverter reactive power flow command value and side in parallel transverter reactive power are referred to according to controlled busbar voltage amplitude
The susceptibility of value changes is made to be allocated, i.e. Dse:Dsh=| Bac|:|Aac|。
Error signal Δ R in ac bus voltage tuning controllerse、ΔRshCalculated and obtained by following formula:
ΔRse=-Δ VacSgn(Aac)
ΔRsh=Δ VacSgn(Bac)
Wherein:ΔVac=max (Vac-Vac,max,0)+min(Vac-Vac,min, 0), Vac,maxAnd Vac,minExchange is controlled respectively
The higher limit and lower limit of bus run voltage, Sgn (x) are sign function, and its value is with independent variable x rule of conversion:
(3) by Regulate signal Δ QLWith reactive power flow setting value Q under nominal situationL0The UPFC series side changes of current are obtained after addition
The final reactive power flow command value Q of deviceL *;By Regulate signal Δ QshWith reactive power setting value Q under nominal situationsh0After addition
To the reactive power command value Q that UPFC series side transverters are finalsh *;Command value is separately input to UPFC series side transverters
Reactive power flow control module and side transverter Reactive Power Control module in parallel, as UPFC control reference value and carry out
Control, to realize that the idle control abilities of UPFC are utilized to greatest extent.
Fig. 4 is a certain actual electric network system rough schematic view, and UPFC is arranged on one close to ac bus 1 on circuit 1-2
Side, ac bus voltage magnitude is to UPFC series side transverter reactive power flow command values QL *And side in parallel transverter reactive power
Command value Qsh *The simulation value of change sensitivity and the contrast of analytic value are as shown in table 1.Simulation value is in table 1Respectively
The change (unit pu) of each busbar voltage amplitude when individually changing 1pu, analytic value is the formula meter provided using present embodiment
Obtained result;ΔV1、ΔV3、ΔV4The respectively variable quantity of the voltage magnitude of ac bus 1,3,4.
Table 1
Ac bus voltage magnitude is to UPFC series side transverter reactive power flow command values it can be seen from data in table 1
QL *And parallel connection side transverter reactive power command value Qsh *The simulation value of change sensitivity differs smaller with analytic value, Ke Yili
The computational methods provided with present embodiment judge that ac bus voltage magnitude is instructed to UPFC series side transverters reactive power flow
Value QL *And parallel connection side transverter reactive power command value Qsh *Change the size of sensitivity.Meanwhile, what present embodiment was provided
During UPFC control strategies are to getting over line voltage progress feedback control, A has only been usedacAnd BacSymbol, and do not need numerical value
It is upper identical.The control effect to present embodiment coordination control strategy is verified below, and DC converter station exchange is female
The steady state voltage level and transient voltage support strength of line to extra-high voltage direct-current dissolve with the safe and stable operation of system be to
Close important, therefore selection DC converter station ac bus (bus 3) is used as controlled ac bus.
As shown in Figure 5 and Figure 6, dynamic is imitative for the response process of present embodiment UPFC connection in series-parallel transverter coordination control strategies
Really process is:Non-metal earthing failure occurs for the side of 1~2 double loop 1 during 1.0s, and UPFC protection acts, series connection transverter is moved back
Go out operation, 1.1s cuts off fault loop, UPFC series connection transverters during 3.1s on non-faulting loop put into operation again.Dynamic
In emulation, when installing present embodiment UPFC connection in series-parallel transverter tuning controllers additional in UPFC, parameter used is as follows:Vac,min
=0.96pu, Vac,max=1.04pu, Kse=1000, Dse=0.00062, Ksh=1000, Dsh=0.00056, QL0=
5.94pu, Qsh0=0.
Using DC converter station ac bus (bus 3) after present embodiment control strategy it can be seen from Fig. 5 and Fig. 6
Transient voltage support strength and stable state pressure regulation ability be improved.If simultaneously it can be seen from enlarged fragmentary portion in Fig. 6
Reactive power flow regulation without series connection transverter, parallel inverter it is idle exert oneself increase when, the distribution of natural trend is lower to pass through 2-1 lines
The reactive power of road direction direct current drop point region conveying can be reduced on the contrary after accident, be unfavorable for after DC converter station bus accident electric
The recovery of pressure.After series connection transverter puts into operation, adjust idle on 2~1 circuits by changing UPFC reactive power flows command value
Trend, further improves the reactive power flow distribution for recovering system after voltage, improvement accident after DC converter station bus-bar fault, reduces
To the capacity requirement of direct current capacitors.As can be seen here, UPFC connection in series-parallel transverter coordination control strategy of the present invention has preferable
Dynamic characteristic, above-mentioned analysis also demonstrates the validity of UPFC connection in series-parallel transverter coordination control strategy of the present invention.
The above-mentioned description to embodiment is understood that for ease of those skilled in the art and using the present invention.
Person skilled in the art obviously can easily make various modifications to above-described embodiment, and described herein general
Principle is applied in other embodiment without passing through performing creative labour.Therefore, the invention is not restricted to above-described embodiment, ability
Field technique personnel are according to the announcement of the present invention, and the improvement made for the present invention and modification all should be in protection scope of the present invention
Within.