CN106953336A - A kind of ac bus voltage adjusting method based on UPFC - Google Patents

Abstract

The invention discloses a kind of ac bus voltage adjusting method based on UPFC, it, to the susceptibility of UPFC series side transverter reactive power flow set point changes, determines the bus set of monitored protection by calculating each ac bus voltage magnitude in power network first；Then the amplitude of alternating voltage in bus set is monitored during operation of power networks, when monitoring that alternating voltage more prescribes a time limit, UPFC series side reactive power flow setting values can be automatically adjusted by control strategy of the present invention, by alternating voltage control in the range of safe and stable operation.Voltage-regulation strategy of the present invention can solve the problems, such as to enhance the security of operation of power networks due to the voltage out-of-limit that failure or load fluctuation are brought automatically, significant for UPFC engineer applied and power network safety operation.

Description

A kind of ac bus voltage adjusting method based on UPFC

Technical field

The invention belongs to Power System Flexible transmission ＆ distribution electro-technical field, and in particular to a kind of ac bus electricity based on UPFC Press adjusting method.

Background technology

Voltage stabilization is an importance of power system safety and stability operation, busbar voltage amplitude and its nominal value it Between deviation be also reflect the quality of power supply an important indicator.With network load level persistently rise, new energy it is big Amount access, voltage out-of-limit problem turns into one of principal element of influence power network safety operation and load power supply quality.It is flexible The appearing as of ac transmission (Flexible AC Transmission System, FACTS) technology realizes that line voltage regulation is carried New means are supplied.

In existing document, voltage regulation problem is realized typically by parallel reactive power compensator or filter.Skill In art, as the FACTS devices of latest generation, THE UPFC (Unified Power Flow Controller, UPFC series side device) has the effect of adjusting circuit reactive power flow, therefore also has the ability of regulation line voltage.It is existing Document pointed out, being utilized respectively series compensation device (UPFC series sides transverter) and paralleling compensating device, (Static Synchronous is idle to be mended Repay device) identical voltage-regulation target is realized, the installed capacity needed for series compensation device will be much smaller than paralleling compensating device.

As shown in figure 1, UPFC is made up of two back-to-back voltage source converters, two back-to-back transverters share straight Bus and DC capacitor are flowed, the two is all by converter power transformer access system, and wherein the converter power transformer of current transformer 2 is with shape of connecting Formula is accessed.Active power can be flowed freely between two current transformers in either direction, the ac output end of each current transformer Also reactive power can be independently generated or absorbed by.The function of current transformer 2 is to inject width to circuit by series transformer in UPFC Value and phase angle controllable voltage vector；The major function of current transformer 1 is to provide or absorbed current transformer 2 on common DC bus Required active power, to maintain to connect, the active power between injecting voltage and circuit is exchanged.In power transmission network, UPFC leads to Often operate in active/reactive power flow control model, i.e., will by adjusting the amplitude and phase angle of series transformer injecting voltage vector Circuit is active/and reactive power flow control is in setting value.In normal operation, the precise control of active/reactive power flow can realize electricity The improvement of net trend distribution, the optimization of operating index.However, when Operating Voltage is out-of-limit, being particularly due to catastrophic failure and leading When causing voltage out-of-limit, if will active/reactive power flow control in setting value, UPFC will be caused to install between the system of circuit two ends Reactive power support limited ability, is unfavorable for the optimization of line voltage distribution.Therefore, a set of ac bus voltage based on UPFC is formulated Regulation strategy, the automatic idle setting value for changing UPFC series side transverters, strengthens UPFC and installs circuit two ends system when necessary The voltage support ability of system, is extremely necessary to power network safety operation.

The content of the invention

In view of above-mentioned, the invention provides a kind of ac bus voltage adjusting method based on UPFC, this method is only being handed over Flow busbar voltage more to act in limited time, the amplitude of alternating voltage is monitored during operation of power networks, when alternating voltage more in limited time can UPFC series side reactive power flow setting values are automatically adjusted, by alternating voltage control in the range of safe and stable operation, electricity are enhanced The security of network operation.

A kind of ac bus voltage adjusting method based on UPFC, comprises the following steps：

(1) UPFC series side transverters reactive power flow is set by calculating each bus nodes voltage magnitude in power system Value Q₀ ^*The susceptibility of change, it is determined that to be monitored the bus set Λ of protection；

(2) voltage out-of-limit deviation signal Δ R is determined according to the voltage magnitude of each bus nodes in bus set Λ；Work as detection It is that system has busbar voltage more to prescribe a time limit to Δ R ≠ 0, UPFC series side transverter reactive power flows is generated by voltage regulator controller Setting value Q₀ ^*Regulate signal Δ Q；

(3) Regulate signal Δ Q and reactive power flow setting value Q are made₀ ^*The final nothing of UPFC series side transverters is obtained after addition Work(trend setting value Q^*, idle reference value as UPFC series side transverter power flowcontrol modules is simultaneously controlled, with Realize and system busbar node voltage is adjusted.

For any bus nodes in system in the step (1), if the numbering of the bus nodes is m, the bus Node voltage amplitude is to UPFC series side transverter reactive power flow setting values Q₀ ^*The susceptibility of change is Z_mImaginary part, Z_m=Z_mx- Z_my, Z_mxFor m row xth column elements, Z in matrix Z_myFor m row y column elements in matrix Z, x and y are respectively that UPFC installs institute In the numbering of circuit two ends bus nodes, matrix Z is the inverse matrix of system node admittance matrix.

For any bus nodes in system in the step (1), if the bus nodes voltage magnitude is connected to UPFC Side transverter reactive power flow setting value Q₀ ^*The susceptibility of change is X_mAnd | X_m| ＞ X_set, then the bus nodes are selected into bus collection Close in Λ, X_setFor given threshold parameter.

Voltage out-of-limit deviation signal Δ R is determined by below equation in the step (2)：

ΔR_i=max (V_i-V_i,max,0)+min(V_i-V_i,min,0)

Wherein：I is any bus nodes in bus set Λ, V_iFor bus nodes i voltage magnitude, V_i,maxAnd V_i,min The respectively higher limit and lower limit of bus nodes i working voltages, X_iFor bus nodes i voltage magnitudes V_iUPFC series sides are changed Flow device reactive power flow setting value Q₀ ^*The susceptibility of change.

Voltage regulator controller in the step (2) is based on following transmission function：

Wherein：K_aFor given integral coefficient, D is given droop control coefficient, and s is Laplace operator.

The present invention is set by calculating each ac bus voltage magnitude in power network to UPFC series side transverters reactive power flow The susceptibility of value changes, determines the bus set of monitored protection；The ac bus in monitoring set during operation of power networks Voltage magnitude, when monitoring that alternating voltage more prescribes a time limit, the present invention can automatically adjust UPFC series side reactive power flow setting values, will Alternating voltage is controlled in the range of safe and stable operation.Meanwhile, the present invention can be solved due to failure or load fluctuation band automatically The voltage out-of-limit problem come, enhances the security of operation of power networks, engineer applied and electricity net safety stable fortune for UPFC Row is significant.

Brief description of the drawings

Fig. 1 is THE UPFC UPFC structural representation.

Fig. 2 is the structural representation of the power system containing UPFC.

Fig. 3 is the structural representation of voltage regulator controller.

Fig. 4 is the structural representation of the node systems of IEEE 39.

Fig. 5 is the waveform diagram of the voltage magnitude of bus 15.

Fig. 6 is the waveform diagram of UPFC series side transverter reactive power flow setting values.

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.

Ac bus voltage-regulation strategy of the invention based on UPFC, comprises the following steps：

(1) UPFC series side transverter reactive power flows setting value is become by calculating each ac bus voltage magnitude in power network The susceptibility of change, it is determined that by voltage-regulation policy monitor and the bus set Λ of protection.

Susceptibility computational methods of the ac bus voltage magnitude to UPFC series side transverter reactive power flow set point changes It is as follows：

For a power system containing a bar ac bus, it is circuit 1 that UPFC, which installs circuit number, and two ends connect mother Line numbering is bus 1 and 2, as shown in Figure 2.Matrix Z_nFor the inverse matrix of radio network node admittance matrix, its i-th row jth row member Element is Z_ij(i, j=1,2 ..., a).It can be obtained according to electric network theory, bus m voltage phasors install circuit curent change to UPFC Sensitivity level can use Z_mPortray, Z_mComputing formula be：

Z_m=Z_m2-Z_m1 A1

In actual power transmission network, the value of overhead transmission line resistance is much smaller than its reactance value, compared to imaginary part, Z_mReal 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, bus m (m=1,2 ..., a) voltage magnitude V_mVariable quantity and UPFC series side transverters idle setting value Q^*The relation of variable quantity is：

ΔV_m=X_mΔQ^*

Wherein, X_mFor Z_mImaginary part, take X_mIt is bus m voltage magnitudes to UPFC series side transverter reactive power flow setting values The sensitivity coefficient of change, X_mValue reflect ac bus voltage magnitude to UPFC series side transverter reactive power flows setting value become The susceptibility of change.

Set Λ determination method is as follows：

Sensitivity coefficient X_mIt is to determine voltage-regulation strategy to the key indexs of bus m voltage regulation capability sizes, therefore by X_m Elect the control sensitivity indexes of voltage-regulation strategy as.Due to set Λ be defined as by voltage-regulation policy monitor and protect The bus included in bus set, set should be that the exchange to the idle set point change more sensitivity of series side transverter is female Line.X_setFor given threshold parameter, set Λ determination principle is as follows：When | X_m| ＞ X_setWhen, bus m is selected into set Λ.

(2) voltage magnitude of ac bus in bus set Λ is monitored during operation of power networks, voltage out-of-limit is obtained inclined Difference signal Δ R, when monitoring alternating voltage out-of-limit (Δ R ≠ 0), generates UPFC series sides idle by voltage regulator controller The idle setting value Q that Regulate signal the Δ Y, Δ Y of trend setting value give with control centre₀ ^*Final UPFC series connection is obtained after superposition Side transverter is idle setting value Q^*。

Voltage regulator controller is as shown in figure 3, wherein K_AFor integrator gain, D is voltage droop control coefficient, and s is drawing General Laplacian operater.Error signal Δ R obtains UPFC after being superimposed with output signal Δ Y feedback signal D Δs Y after integral element The Regulate signal Δ Y of series side reactive power flow setting value.

Error signal Δ R in voltage regulator controller is calculated by formula A2 to be obtained：

For bus m (m=1,2 ..., a), Δ R_mAnd Sgn_mCalculated and obtained by formula A3 and A4 respectively：

ΔR_m=Max (V_m-V_m,max,0)+Min(V_m-V_m,min,0) A3

Wherein, V_mFor bus m voltage magnitudes；V_m,maxAnd V_m,minThe respectively upper and lower bound of bus m working voltages；Max It is respectively the function that takes maximum He take minimum value with Min.

Ensure system existence anduniquess stable operation by being introduced as voltage droop control coefficient D in voltage regulator controller Point, and can realize power network recover normal operating condition (also can guarantee that ac bus voltage not without voltage-regulation strategy It is out-of-limit) when, setting value that UPFC series side transverters are idle being capable of the given idle setting value Q of restoration control center automatically₀ ^*.Pass through Formula A2 can realize a plurality of ac bus and meanwhile occur voltage out-of-limit when processing, by formula A3 can realize overvoltage it is out-of-limit and The out-of-limit processing of low-voltage.

(3) by Q^*The power flowcontrol module of UPFC series side transverters is assigned to, the ac bus based on UPFC just can be realized Voltage-regulation.

Following example system uses the node systems of IEEE 39 (for 345kV, capacity base value is 100MVA to voltage base value), such as Shown in Fig. 4, region A electric power is sent out section and is made up of circuit 2-1,2-3 and 26-27, is that adjustment region A sends out section tidal current point Cloth, UPFC devices are installed additional in the circuit 2-3 side of bus 2.

First, calculate power network in each ac bus voltage magnitude to UPFC series side transverter reactive power flow set point changes Susceptibility X_m.Emulation of the ac bus voltage magnitude to the susceptibility of UPFC series side transverter reactive power flow set point changes Value X_sim(change the idle setting values of UPFC in simulated program, observe the variable quantity of ac bus voltage magnitude to obtain sensitive Degree) and calculated value X_m(being obtained using above-mentioned computational methods) is compared in table 1.

Table 1

Operating mode is also the operating mode used during subsequent dynamic is emulated based on operating mode I, and circuit 2-3 trend is controlled by UPFC System is in 3.6+j0.0pu, and UPFC parallel connections side transverter, which is operated in, determines AC voltage profile.Transmission line of alternation current 15-16 in operating mode II Disconnect, UPFC side transverters in parallel operate in surely idle pattern in operating mode III.The proposition of the present invention it can be seen from data in table 1 Ac bus voltage magnitude to being tied obtained by the computational methods of UPFC series side transverter reactive power flow set point change susceptibilitys Fruit and simulation value are close, can as voltage-regulation sensitivity index.

In dynamic simulation, UPFC series sides transverter uses voltage-regulation strategy of the present invention, and parameter used is as follows：X_set =0.01, K_a=100, D=0.001, V_m,min=0.95, V_m,max=1.05 (m ∈ Λ).As shown in figure 4, bus 15 and each power supply Between electrical distance farther out, voltage support intensity is relatively low, thus be easiest to occur voltage out-of-limit.Control strategy pair of the present invention The dynamic response situation of the voltage pulsation caused by load fluctuation is as shown in Figure 5 and Figure 6.Fig. 5 is the voltage magnitude of bus 15, figure 6 be the idle setting value of UPFC series side transverters.Simulation process is as follows：At 2.0 seconds, the neighbouring bus of bus 15 (bus 4,14, 15,16,17,18) load increase by 40% is connected；At 20.0 seconds, load restoration initial value.

As shown in Figure 5 and Figure 6, under the operating mode that load increases by 40%, when not using control strategy of the present invention, the electricity of bus 15 Pressure amplitude value will drop to below 0.95pu；Install additional after controller as shown in Figure 3, after the voltage out-of-limit of bus 15, controller is rapid The idle setting value of action regulation UPFC series side transverters (to obtain more reactive power supports from region A, the UPFC that increases sharply strings Join the idle setting value of side transverter), the voltage of bus 15 is controlled in 0.95pu, it is ensured that it is not out-of-limit.When load level recovers just Chang Hou, it is not necessary to which voltage stabilization can also be kept by continuing the idle setting valve system of regulation UPFC series side transverters.In sagging control In the presence of system, setting value that UPFC series side transverters are idle returns to the given Q of control centre₀ ^*。

Above-mentioned analysis demonstrates the ac bus voltage-regulation strategy validity of the invention based on UPFC.

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.

Claims (5)

1. a kind of ac bus voltage adjusting method based on UPFC, comprises the following steps：

(1) by calculating in power system each bus nodes voltage magnitude to UPFC series side transverter reactive power flow setting values Q₀ ^* The susceptibility of change, it is determined that to be monitored the bus set Λ of protection；

(2) voltage out-of-limit deviation signal Δ R is determined according to the voltage magnitude of each bus nodes in bus set Λ；When detecting Δ R ≠ 0 is that system has busbar voltage more to prescribe a time limit, and generating UPFC series side transverters reactive power flow by voltage regulator controller sets Value Q₀ ^*Regulate signal Δ Q；

(3) Regulate signal Δ Q and reactive power flow setting value Q are made₀ ^*The final idle tide of UPFC series sides transverter is obtained after addition Flow setting value Q^*, idle reference value as UPFC series side transverter power flowcontrol modules is simultaneously controlled, to realize System busbar node voltage is adjusted.

2. ac bus voltage adjusting method according to claim 1, it is characterised in that：For being in the step (1) Any bus nodes in system, if the numbering of the bus nodes is m, the bus nodes voltage magnitude is to the UPFC series side changes of current Device reactive power flow setting value Q₀ ^*The susceptibility of change is Z_mImaginary part, Z_m=Z_mx-Z_my, Z_mxFor m rows xth row member in matrix Z Element, Z_myFor m row y column elements in matrix Z, x and y are respectively the numbering of circuit two ends bus nodes where UPFC is installed, square Battle array Z is the inverse matrix of system node admittance matrix.

3. ac bus voltage adjusting method according to claim 1, it is characterised in that：For being in the step (1) Any bus nodes in system, if the bus nodes voltage magnitude is to UPFC series side transverter reactive power flow setting values Q₀ ^*Change Susceptibility be X_mAnd | X_m| ＞ X_set, then the bus nodes are selected into bus set Λ, X_setFor given threshold parameter.

4. ac bus voltage adjusting method according to claim 1, it is characterised in that：In the step (2) by with Lower formula determines voltage out-of-limit deviation signal Δ R：

$\mathrm{\Δ}R=\underset{i\∈\mathrm{\Λ}}{\Σ}{\mathrm{\ΔR}}_i{\mathrm{Sgn}}_i$

ΔR_i=max (V_i-V_i,max,0)+min(V_i-V_i,min,0)

$\left\{\begin{array}{cc}{\mathrm{Sgn}}_i=-1,& X_i\&GreaterEqual;0\\ {\mathrm{Sgn}}_i=1,& X_i<0\end{array}\right.$

Wherein：I is any bus nodes in bus set Λ, V_iFor bus nodes i voltage magnitude, V_i,maxAnd V_i,minRespectively For the higher limit and lower limit of bus nodes i working voltages, X_iFor bus nodes i voltage magnitudes V_iTo UPFC series side transverters Reactive power flow setting value Q₀ ^*The susceptibility of change.

5. ac bus voltage adjusting method according to claim 1, it is characterised in that：Voltage in the step (2) Adjust controller and be based on following transmission function：

$\mathrm{\&Delta;}Q=\frac{\mathrm{\&Delta;}R}{\frac{s}{K_a}+D}$

Wherein：K_aFor given integral coefficient, D is given droop control coefficient, and s is Laplace operator.