CN106356854A - UPFC (unified power flow controller) voltage stabilization control strategy based on control mode switching - Google Patents

Abstract

The invention discloses a UPFC (unified power flow controller) voltage stabilization control strategy based on control mode switching, comprising: using fixed power control in UPFC initial control mode; in case of high-disturbance failure, switching the fixed power control to impedance compensation control, and compensating according to a preset compensation impedance value; after impedance compensation control is over, switching back to the fixed power control by means of slope control; in case of low-disturbance failure, not switching the control mode. In connection with the characteristic that UPFC power flow control allows for adjustment of strong power flows and the advantage that impedance compensation control facilitates voltage stabilization, it is possible to improve system voltage stability at the premise of providing UPFC power flow adjusting function.

Description

A kind of upfc Voltage Stability Control strategy based on control mode switch

Technical field

The present invention relates to a kind of upfc Voltage Stability Control strategy, power system stability and control based on control mode switch Field processed.

Background technology

Power system is a complicated large-scale nonlinear dynamical system, and its stability analysis is always power system rule The important subject drawn and run.For a long time, angle stability problem has obtained the common concern of people, and establishes a set of Relatively more complete angle stability analysis theories and method, but meanwhile, voltage stabilization is another as power system stability problem One importance, progress is but relatively slow.

With the development of social progress and science and technology, entire society is growing for electrical energy demands, modern electric System enters high voltage, large-sized unit, bulk power grid epoch.The Relatively centralized of load capacity simultaneously；Power plant away from load center Emerge in multitude；Remote DC transmission system and the application of a large amount of power electronic equipment；These new changes are for raising warp Ji benefit, rationally utilizing of the energy is all significant with the protection of environment, but asks to Power System Voltage Stability simultaneously again Topic brings new test.At present China's electric network composition is relatively weak, and generating equipment storage levels are less, in addition with power system from Generate electricity, a system of transmission of electricity develops into nowadays open, competition market environment, Power System Planning and the uncertainty run and Unsafe factor increases, and voltage is dangerous to have become as one of restriction power transmission principal element.

Improving voltage stability most common method is to compensate to system injection reactive power.Traditional mechanical type control Method processed has obvious limitation, and more topmost is that speed is slow.Due to special by the physical characteristics of mechanical switch and shutoff Property etc. limit, its operating time be generally 20～80ms.Institute substantially can only control system in the conventional way under quiescent conditions System trend, the control to dynamic stability lacks enough abilities.And FACTS (flexible alternating Current transmission system, facts), equipped with power electronics or other static type controllers, can quickly may be used That leans on carries out Dynamic Stability Control to system, the ability having stronger controllability and increasing power transmission.

With the fast development of the constantly progressive of technology and China's power system, the complexity of electric network composition and the method for operation Degree gradually steps up.Meanwhile, electrical network intellectuality makes facts device obtain in systems being increasingly widely applied, and Play increasingly stronger effect.THE UPFC (unified power flow controller, upfc) combines Various facts device control devices, are function elements the most powerful in facts component arrangement.It being capable of dynamic control power train Active, the idle, voltage of system, impedance and generator rotor angle, are easy to optimize the system operation, improve power system transient stability can damping system Vibration, can be increasingly becoming the focus of current research to carrying out AC transmission system real-time control and dynamic compensation.In view of upfc Comprehensive and superior performance, it plays the role of very positive for improving Power System Voltage Stability, and research is equiped with The voltage stability of the power system of upfc, more comprehensively, quickly with power system merges for power electronic equipment and opens Open up the Power System Voltage Stability Study on Problems new situation to be all of great practical significance.

The main purpose that upfc applies in systems is regulating system trend, so that system load flow is distributed more reasonable, so Upfc control mode typically adopts the strong constant dc power control of power flow regulating characteristic.But in transient process, upfc adopts and determines power The ability maintaining system voltage stability during control is not so good as impedance-compensated control, but impedance-compensated control does not determine power control again The power flow regulating characteristic of system.

Content of the invention

In order to solve above-mentioned technical problem, the invention provides a kind of upfc voltage stabilization control based on control mode switch System strategy.

In order to achieve the above object, the technical solution adopted in the present invention is:

A kind of upfc Voltage Stability Control strategy based on control mode switch, comprises the following steps,

Upfc initial control mode uses constant dc power control, controls the effective power flow p of upfc place circuit_lWith reactive power flow q_l, will p_l+jq_lControl in p_ref+jq_ref；

p_ref、q_refIt is respectively upfc place circuit power flow control desired value and line reactive power control targe value；

When there is large disturbances fault, constant dc power control is switched to impedance-compensated control, by predesigned compensation resistance value x_upfcIt is controlled, the impedance-compensated control persistent period is t；

After impedance-compensated control terminates, by the way of slope controls, switch back into constant dc power control；

When there is microvariations fault, do not do the switching of control model.

The mathematic(al) representation of constant dc power control is,

$\left\{\begin{array}{c}{v}_{seq}=(k_{pp}+\frac{k_{pi}}{s})(p_{ref}-p_l)\\ v_{sep}=(k_{qp}+\frac{k_{qi}}{s})(q_{ref}-q_l)\end{array}\right.$

Wherein, v_seqFor the component that upfc series side output voltage is perpendicular with sending end voltage, v_sepDefeated for upfc series side Go out voltage and sending end voltage component in the same direction, k_pp、k_pi、k_qp、k_qiIt is the parameter of pi controller,Represent the integration that pi controls Link.

The mathematic(al) representation of impedance-compensated control is,

$\left\{\begin{array}{c}{v}_{seq}=-i_{linep}(x_{upfc}-x_{se})\\ v_{sep}=i_{lineq}(x_{upfc}-x_{se})\end{array}\right.$

Wherein, i_linepFor upfc place line current and sending end voltage component in the same direction, i_lineqFor upfc place line electricity Stream and the component of sending end voltage vertical, x_seFor upfc series side transformer reactance.

Slope control process be,

When the impedance-compensated control of upfc was exited through the t time, when being switched to constant dc power control, by the control of constant dc power control Desired value p_ref、q_refIt is set as the current effective power flow of upfc place circuitWith reactive power flow valueWherein t_tFor resistance The moment is exited in anti-compensation control；

During the control of slope, control targe value p of constant dc power control_ref、q_refBy following rule linear change:

$\left\{\begin{array}{c}{p}_{ref}=\frac{(p_{ref0}-p_{t=t_t})}{t_r}(t-t_t)+p_{t=t_t}\\ q_{ref}=\frac{(q_{ref0}-q_{t=t_t})}{t_r}(t-t_t)+q_{t=t_t}\end{array}\right.$

Wherein, t_rThe persistent period controlling for slope, p_ref0、q_ref0For the control targe value before large disturbances fault, t represents Time, t_t≤t≤t_t+t_r；

At the end of slope controls, control targe value p of constant dc power control_ref、q_refBy linear change, it is changed into large disturbances event Control targe value p before barrier_ref0、q_ref0.

The beneficial effect that the present invention is reached: the present invention is combined upfc power flowcontrol powerful power flow regulating characteristic and mended with impedance Repay the advantage controlling beneficial to voltage stabilization, while realizing upfc power flow regulating function, system voltage stability can be improved.

Brief description

Fig. 1 is the flow chart of the present invention.

Fig. 2 is upfc mounting means schematic diagram in systems.

Fig. 3 is upfc series side constant dc power control block diagram.

Fig. 4 is the impedance-compensated control block diagram of upfc series side.

Fig. 5 is slope control schematic diagram.

Fig. 6 is wscc tri- machine Psychotria rubra (Lour.) Poir. dot system wiring diagram.

Fig. 7 is b5 node voltage curve comparison diagram under two kinds of control modes during large disturbances.

Fig. 8 is circuit active power comparison diagram under two kinds of control modes during large disturbances.

Fig. 9 is circuit reactive power comparison diagram under two kinds of control modes during large disturbances.

Specific embodiment

The invention will be further described below in conjunction with the accompanying drawings.Following examples are only used for clearly illustrating the present invention Technical scheme, and can not be limited the scope of the invention with this.

As shown in figure 1, a kind of upfc Voltage Stability Control strategy based on control mode switch, comprise the following steps:

1) upfc initial control mode uses constant dc power control, controls the effective power flow p of upfc place circuit_lWith idle tide Stream q_l, will p_l+jq_lControl in p_ref+jq_ref；p_ref、q_refIt is respectively upfc place circuit power flow control desired value and line Road reactive power flow control targe value.

As shown in Fig. 2 for upfc mounting means schematic diagram in systems, (this is connected as existing structure, does not retouch in detail State).Wherein, r_l、x_lFor the line parameter circuit value of circuit ij, represent resistance, the reactance of circuit ij respectively；v_i、v_jIt is respectively node i, j Voltage magnitude；θ_j、θ_jIt is respectively node i, the voltage phase angle of j；t_seAnd t_shIt is respectively the series transformer of upfc and change in parallel Depressor；v_se∠θ_seThe voltage exporting for upfc series transformer,For upfc series side place line current；v_sh∠θ_shFor The voltage of upfc shunt transformer output,Electric current for collateral road in parallel.

As shown in figure 3, being upfc series side constant dc power control block diagram.Wherein, t_se1And t_se2Time constant for inverter； k_pp、k_pi、k_qp、k_qiIt is the parameter of pi controller；v_seqFor the component that upfc series side output voltage is perpendicular with sending end voltage； v_sepFor upfc series side output voltage and sending end voltage component in the same direction；v_serefFor v_seqAnd v_sepThe amplitude of resultant voltage, θ_serefFor v_seqAnd v_sepThe phase angle of resultant voltage.

The mathematic(al) representation of constant dc power control is:

$\left\{\begin{array}{c}{v}_{seq}=(k_{pp}+\frac{k_{pi}}{s})(p_{ref}-p_l)\\ v_{sep}=(k_{qp}+\frac{k_{qi}}{s})(q_{ref}-q_l)\end{array}\right.$

Wherein,Represent the integral element that pi controls.

2) when there is large disturbances fault, constant dc power control is switched to impedance-compensated control, by predesigned compensation resistance value x_upfcIt is controlled, the impedance-compensated control persistent period is t.

Voltage stability criterion in " power system safety and stability computing technique specification " according to version in 2013: in electricity Force system be disturbed after transient process in, load busbar voltage can return to more than 0.8p.u. in 10s；Medium-term and long-term During load busbar voltage can keep or return to more than 0.9p.u..

Judge to occur the mathematic(al) representation of large disturbances fault to be represented by:

v_ref-v_t≥0.2p.u.

δt≤0.1s

Wherein, v_refRepresent the reference value of monitoring point voltage, v_tRepresent the actual value of monitoring point voltage, δ t express time becomes Change amount.Above-mentioned expression formula is expressed as, when monitoring the deviation that point voltage occurs more than 0.2p.u. in 0.1s, judging to occur to disturb greatly Dynamic fault, need to be controlled pattern switching.

As shown in figure 4, being the impedance-compensated control block diagram of upfc series side.Wherein, i_linepFor upfc place line current with Sending end voltage component in the same direction, i_lineqFor the component of upfc place line current and sending end voltage vertical, x_seFor upfc series side Transformer reactance.

The mathematic(al) representation of impedance-compensated control is:

$\left\{\begin{array}{c}{v}_{seq}=-i_{linep}(x_{upfc}-x_{se})\\ v_{sep}=i_{lineq}(x_{upfc}-x_{se})\end{array}\right.$

3), after impedance-compensated control terminates, by the way of slope controls, switch back into constant dc power control.

As shown in figure 5, being slope control schematic diagram, wherein, x_refRepresent control targe, can be circuit power or The voltage of node, x represents that slope controls control targe value when starting, x₀Represent that slope controls the control targe value after terminating；t_t Represent that slope controls the moment starting, i.e. impedance-compensated control is exited the moment, t_rRepresent that slope controls duration.

The process that slope controls is:

A) when the impedance-compensated control of upfc was exited through the t time, when being switched to constant dc power control, by the control of constant dc power control Desired value p processed_ref、q_refIt is set as the current effective power flow of upfc place circuitWith reactive power flow value

B) during the control of slope, control targe value p of constant dc power control_ref、q_refBy following rule linear change:

$\left\{\begin{array}{c}{p}_{ref}=\frac{(p_{ref0}-p_{t=t_t})}{t_r}(t-t_t)+p_{t=t_t}\\ q_{ref}=\frac{(q_{ref0}-q_{t=t_t})}{t_r}(t-t_t)+q_{t=t_t}\end{array}\right.$

Wherein, t_rThe persistent period controlling for slope, p_ref0、q_ref0For the control targe value before large disturbances fault, t represents Time, t_t≤t≤t_t+t_r.

C) at the end of slope controls, control targe value p of constant dc power control_ref、q_refBy linear change, it is changed into large disturbances Control targe value p before fault_ref0、q_ref0.

4) when there is microvariations fault, do not do the switching of control model.

In order to further illustrate above-mentioned control strategy, using psasp software in wscc tri- machine Psychotria rubra (Lour.) Poir. point mark as shown in Figure 6 Tested in Barebone, wherein l1, l2, l3 are induction machine load, system b5 node voltage level is low.Upfc is connected Side is installed at the b1 of circuit b1-b5, and side joint in parallel is in b1 node.

Upfc basic parameter is: upfc series side transformator injection voltage max v_semax=0.115p.u., series side becomes Depressor internal reactance x_se=0.02p.u..

When upfc adopts constant dc power control, by charged line power flowcontrol in 0.97+j0.10, node b1 voltage controls 1.01p.u., each controller parameter is: k_pp=0.9, k_pi=4, k_qp=0.7, k_qi=6；Using voltage stabilization control set forth above When processed, control targe is consistent with using target during constant dc power control, and sets upfc compensating impedance value x_upfc= 0.075p.u., the impedance-compensated control persistent period is t=3s, slope control time t_r=3s, emulates duration 20s.

Large disturbances fault is arranged: the three phase short circuit fault at b5, and the time started is 2s, failure removal after 0.18s.

Respectively upfc is emulated using the situation of constant dc power control and Voltage Stability Control, in the case of large disturbances, section The voltage curve of point b5 is as shown in Figure 7.As shown in Figure 7, after failure removal, the upfc Voltage Drop using constant dc power control arrives 0.6p.u. about, and big ups and downs occur, and adopt the upfc of Voltage Stability Control, after failure removal, at b5, voltage is extensive Arrive original level again.Illustrate preferably to carry than having using the upfc of constant dc power control using the upfc of Voltage Stability Control Rise the ability of system voltage stability.

Under two kinds of control modes, the circuit active power of upfc place circuit b1-b5 and reactive power contrast are respectively as Fig. 8 With shown in Fig. 9.Understand, Line Flow can be adjusted to original water after failure removal by the upfc using Voltage Stability Control Flat, and do not affect the realization of the power flow regulating function of upfc.Wherein 5s～8s for slope control switching process it can be seen that Circuit is active idle with circuit smooth to be transitioned into original value.And lost after failure removal using the upfc of constant dc power control The ability of adjusting circuit trend.

In sum, the present invention is combined upfc power flowcontrol powerful power flow regulating characteristic and is controlled beneficial to voltage with impedance-compensated Stable advantage, while realizing upfc power flow regulating function, can improve system voltage stability.

The above is only the preferred embodiment of the present invention it is noted that ordinary skill people for the art For member, on the premise of without departing from the technology of the present invention principle, some improvement can also be made and deform, these improve and deform Also should be regarded as protection scope of the present invention.

Claims (4)

1. a kind of upfc Voltage Stability Control strategy based on control mode switch it is characterised in that: comprise the following steps,

Upfc initial control mode uses constant dc power control, controls the effective power flow p of upfc place circuit_lWith reactive power flow q_l, that is, By p_l+jq_lControl in p_ref+jq_ref；

p_ref、q_refIt is respectively upfc place circuit power flow control desired value and line reactive power control targe value；

When there is large disturbances fault, constant dc power control is switched to impedance-compensated control, by predesigned compensation resistance value x_upfcCarry out Control, the impedance-compensated control persistent period is t；

After impedance-compensated control terminates, by the way of slope controls, switch back into constant dc power control；

When there is microvariations fault, do not do the switching of control model.

2. a kind of upfc Voltage Stability Control strategy based on control mode switch according to claim 1, its feature exists In: the mathematic(al) representation of constant dc power control it is,

$\left\{\begin{array}{c}{v}_{seq}=(k_{pp}+\frac{k_{pi}}{s})(p_{ref}-p_l)\\ v_{sep}=(k_{qp}+\frac{k_{qi}}{s})(q_{ref}-q_l)\end{array}\right.$

Wherein, v_seqFor the component that upfc series side output voltage is perpendicular with sending end voltage, v_sepExport electricity for upfc series side Pressure and sending end voltage component in the same direction, k_pp、k_pi、k_qp、k_qiIt is the parameter of pi controller,Represent the integral element that pi controls.

3. a kind of upfc Voltage Stability Control strategy based on control mode switch according to claim 1, its feature exists In: the mathematic(al) representation of impedance-compensated control it is,

$\left\{\begin{array}{c}{v}_{seq}=-i_{linep}(x_{upfc}-x_{se})\\ v_{sep}=i_{lineq}(x_{upfc}-x_{se})\end{array}\right.$

Wherein, i_linepFor upfc place line current and sending end voltage component in the same direction, i_lineqFor upfc place line current with The component of sending end voltage vertical, x_seFor upfc series side transformer reactance.

4. a kind of upfc Voltage Stability Control strategy based on control mode switch according to claim 1, its feature exists In the process that: slope controls it is,

When the impedance-compensated control of upfc was exited through the t time, when being switched to constant dc power control, by the control targe of constant dc power control Value p_ref、q_refIt is set as the current effective power flow of upfc place circuitWith reactive power flow valueWherein t_tMend for impedance Repay control and exit the moment；

During the control of slope, control targe value p of constant dc power control_ref、q_refBy following rule linear change:

$\left\{\begin{array}{c}{p}_{ref}=\frac{(p_{ref0}-p_{t=t_t})}{t_r}(t-t_t)+p_{t=t_t}\\ q_{ref}=\frac{(q_{ref0}-q_{t=t_t})}{t_r}(t-t_t)+q_{t=t_t}\end{array}\right.$

Wherein, t_rThe persistent period controlling for slope, p_ref0、q_ref0For the control targe value before large disturbances fault, t express time, t_t≤t≤t_t+t_r；

At the end of slope controls, control targe value p of constant dc power control_ref、q_refBy linear change, before being changed into large disturbances fault Control targe value p_ref0、q_ref0.