CN105119281A - UPFC control method with rapid terminal sliding mode variable structure - Google Patents

Abstract

The invention discloses a UPFC control method with a rapid terminal sliding mode variable structure. The UPFC control method comprises: decoupling is carried out on an established systematic mathematic model to obtain a system state equation that can be controlled by a sliding mode variable structure conveniently; according to the actual situation of the system, a terminal sliding mode variable structure is selected; a controller controlled by a parallel side terminal sliding mode variable structure and a controller controlled by a series side terminal sliding mode variable structure can be designed; a controller controlled by the terminal sliding mode variable structure at a direct-current capacitor link is designed; and according to a physical meaning of a target variable, selection quantity measurement and calculation are carried out and a target expectation control signal is outputted, and space vector control is carried out to obtain trigger signals of a series side converter and a parallel side converter. According to the invention, the active and reactive power of the controlled power transmission line can be controlled rapidly and effectively; the adaptability and robustness of the system after disturbance can be improved; and thus the safe and stable operation of the power grid can be guaranteed.

Description

The UPFC control method of quick Terminal sliding moding structure

Technical field

The present invention relates to a kind of UPFC control method of quick Terminal sliding moding structure, belong to power electronics automatic control technology field.

Background technology

THE UPFC (UPFC) is the commanding elevation of electric power application of electronic technology in the world today, as the representative of third generation FACTS equipment, is the most comprehensive FACTS device of function up to now.UPFC not only can solve power delivery imbalance problem, promote electric network swim conveying capacity, simultaneously for optimization system operation, improve the transient stability of system, the vibration of damping system has significant effect, have a extensive future.

The concept of UPFC, proposed in 1992 by people such as L.Gyugyi at first, abroad to UPFC research comparatively early, First device in the world in 1998, successful operation on the ultra-high-tension power transmission line of the 138kV of U.S. locations, the hardware implementing being enough to explanation UPFC is feasible, and current engineering operation is good.And China starts late, just begin one's study after nineteen ninety-five, paper about its control method is also more, the structure of its controller is also varied, and major control method comprises: the methods such as traditional PI control, neural net and fuzzy adaptivecontroller, nonlinear Control, decoupled control scheme, cooperation control.

UPFC can distribute the trend on controlled power transmission line as a kind of series and parallel mixed type FACTS element and node voltage controls flexibly, the DC capacitor of its basic composition module STATCOM (STATCOM) and Static Series Synchronous Compensator (SSSC) and centre.If lack effective control measure to UPFC system, AC system break down or disturbance time likely cause the commutation failure of converter.If commutation failure overlong time may cause converter blocking, a large amount of power cannot be transmitted by converter, very likely cause the unstability of both sides AC system.And if control measure are proper, after AC system breaks down, automatically the meritorious of UPFC system transfers and reactive power is regulated by set control strategy, the time reducing commutation failure even prevents commutation failure, just can make full use of the rapidity of UPFC system fading margin, emergency DC power support is carried out to AC system, or help the fast quick-recovery of AC system after a failure, weaken AC system vibration, ensure the operation of both sides electricity net safety stable.So the stable control method of research UPFC converter, the engineer applied controlling control system for Unified Power Flow provides technical support and favourable reference, has huge economic worth and application prospect.

The UPFC converter control method adopted at present is mainly based on classical PI control theory, very high to the requirement of systematic mathematical modeling, be difficult to obtain satisfied control effects, and robustness is not strong.

Summary of the invention

The object of the invention is to overcome deficiency of the prior art, a kind of UPFC control method of quick Terminal sliding moding structure is provided, solve in prior art and carry out UPFC converter control based on classical PI control theory, high to systematic mathematical modeling demand, control effects is bad, and the technical problem that robustness is not strong.

For solving the problems of the technologies described above, the technical solution adopted in the present invention is: the UPFC control method of Terminal sliding moding structure fast, comprises the steps:

Step one: utilize the method for vector control and the method for coordinate transform to carry out decoupling zero to the system mathematic model set up, thus obtain the system state equation being convenient to Sliding mode variable structure control;

Step 2: the actual conditions according to system select Terminal sliding moding structure, comprise the number of I/O variable, the parameter parity of sliding-mode surface, exponent number;

Step 3: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design side in parallel Terminal Sliding mode variable structure control;

Step 4: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design series side Terminal Sliding mode variable structure control;

Step 5: consider that load current changes the DC bus-bar voltage change caused, the controller of the Terminal Sliding mode variable structure control of design DC capacitor link;

Step 6: export target desired control signal according to the physical meaning selected amount survey calculation of target variable, and obtain the triggering signal of series side and side in parallel converter by Frequency conversion control.

System state equation described in step one is as follows:

Side in parallel converter is with the grid-connected point voltage of control system and idle for control objectives, and its state equation is:

$\left\{\begin{array}{c}{L}_E{\stackrel{\·}{i}}_{Ed}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d}\\ L_E{\stackrel{\·}{i}}_{Eq}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q}\end{array}\right.$

Series side converter is meritorious and idle for control objectives with control circuit, and its state equation is:

$\left\{\begin{array}{c}L{\stackrel{\·}{i}}_{Bd}=-{\mathrm{Ri}}_{Bd}+{\mathrm{\ωLi}}_{Bq}+u_{Bd}+u_{2d}\\ L{\stackrel{\·}{i}}_{Bq}=-{\mathrm{Ri}}_{Bq}-{\mathrm{\ωLi}}_{Bd}+u_{Bq}+u_{2q}\end{array}\right.$

Wherein: L _eand R _erepresent UPFC shunt transformer and connect equivalent inductance and the resistance of reactance; i _edand i _eqbe respectively UPFC side in parallel output current coordinate components, u _sdand u _sqbe respectively electrical network sending end busbar voltage, u _1dand u _1qfor the output voltage of UPFC parallel converters; ω is electrical network angular speed;

L=L _b+ L _n, R=R _b+ R _n, L _band R _brepresent respectively UPFC series transformer connect equivalent inductance and the resistance of reactance, L _nand R _nrepresent equivalent inductance and the resistance of circuit respectively, i _bdand i _bqrepresent the electric current coordinate components that circuit and UPFC series side flow through respectively, u _2dand u _2qfor the output voltage of UPFC series converter, u _bdand u _bqbe respectively the AC output voltage of series connection converter.

Terminal sliding moding structure described in step 2, meets:

$\begin{array}{c}s-\stackrel{\·}{x}+{\mathrm{\βx}}^{q/p}=0\\ \stackrel{\·}{s}=-\mathrm{\φ}s-\mathrm{\γ}{\left|s\right|}^{q/p}\end{array}$

Wherein: S represents switching function; X ∈ R is state variable; P, q are positive odd number, and p is greater than q, β >0; P, q are positive odd number, φ >0, γ >0.

The concrete steps designing the controller of side in parallel Terminal Sliding mode variable structure control described in step 3 are as follows:

Determine the structure of quick Terminal Sliding mode variable structure system, according to quick Terminal Sliding Mode Controller method for designing design parallel inverter control strategy, the state variable of selecting system

x ₁＝i _Ed

x ₂＝i _Eq

Get sliding mode variable s ₁and s ₂, and differentiate

$\begin{array}{c}{\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-{\stackrel{\·}{x}}_1\\ {\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-{\stackrel{\·}{x}}_2\end{array}$

According to parallel inverter state equation,

$\begin{array}{c}{\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-\frac{1}{L_E}(-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d})\\ {\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-\frac{1}{L_E}(-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q})\end{array}$

And get the quick Terminal sliding-mode surface of second order,

$\begin{array}{c}{\stackrel{\·}{s}}_1=-{\mathrm{\φs}}_1-\mathrm{\γ}{\left|s_1\right|}^{q/p}\\ {\stackrel{\·}{s}}_2=-{\mathrm{\φs}}_2-\mathrm{\γ}{\left|s_2\right|}^{q/p}\end{array}$

Obtain the parallel inverter control strategy of final Terminal Sliding mode variable structure control fast, be also

$\begin{array}{c}{u}_{1d}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L_E\\ u_{1q}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L_E\end{array}$

The step designing the controller of series side Terminal Sliding mode variable structure control described in step 4 is as follows:

Choose state variable u _2dand u _2q, the quick Terminal sliding-mode surface of second order, obtains the series connection converter control strategy of quick Terminal Sliding mode variable structure control:

$\begin{array}{c}{u}_{2d}={\mathrm{Ri}}_{Bd}-{\mathrm{\ωLi}}_{Bq}-u_{Bd}+({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L\\ u_{2q}={\mathrm{Ri}}_{Bq}+{\mathrm{\ωLi}}_{Bd}-u_{Bq}+({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L\end{array}$

The controller step designing the Terminal Sliding mode variable structure control of DC capacitor link described in step 5 is as follows:

The state variable x=u of selecting system _dc, get sliding mode variable get synovial membrane face

$S=i_d^{*}-i_d=k_1(s+k_2\stackrel{\·}{s})$

Consider the power relation of DC bus-bar voltage, obtain the control electric current of electric capacity C:

$i_{Ed}^{*}=(s+k\frac{{\mathrm{du}}_{dc}^{*}}{dt}+\frac{k}{C}{i}_{load})\frac{{\mathrm{Cu}}_{dc}}{k(u_{sd}-R_E{i}_{Ed})}.$

Wherein: k, k ₁, k ₂be controller parameter, be all greater than 0; u _dcrepresent DC tache voltage; i _loadrepresent load current.

Target desired value described in step 6 is calculated by following formula and tries to achieve:

$\begin{array}{c}{i}_{Bd}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2d}+Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}\\ i_{Bq}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2q}-Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}\end{array}$

In formula: P, Q represent that circuit is gained merit and reactive power desired value respectively.

Compared with prior art, the beneficial effect that the present invention reaches: the present invention by Terminal sliding mode variable structure control method (basic structure is variable structure control system) for side in parallel converter, during series side converter and intermediate DC link control, in conjunction with the advantage of Sliding mode variable structure control strong robustness and fast convergence rate, UPFC converter control method based on double T erminal sliding moding structure cooperation control is proposed, the present invention fast and effeciently can control the meritorious of controlled transmission line, reactive power, the adaptability of raising system after being disturbed and robustness, thus guarantee power network safety operation.

Accompanying drawing explanation

Fig. 1 is the side in parallel equivalent circuit of UPFC.

Fig. 2 is the series side equivalent circuit of UPFC.

Fig. 3 is the side in parallel control principle block diagram of UPFC.

Fig. 4 is the series side control principle block diagram of UPFC.

Fig. 5 is that two machine two-wires are containing UPFC transmission system topological structure.

Direct voltage response condition when Fig. 6 is control structure change.

Fig. 7 is system operating point response condition when changing.

UPFC response condition when Fig. 8 is the system failure.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

The UPFC control method of quick Terminal sliding moding structure, comprises the steps:

Step one: utilize the method for vector control and the method for coordinate transform to carry out decoupling zero to the system mathematic model set up, thus obtain the system state equation being convenient to Sliding mode variable structure control.

There is cross-couplings in side in parallel and series side converter, realizing vector control control and sliding formwork change Uncoupling Control Based, needing to adopt coordinate transform to set up system state equation under rotating coordinate system to coordinate under three-phase static coordinate system.

Side in parallel converter is with the grid-connected point voltage of control system and idle for control objectives, and its state equation is:

$\left\{\begin{array}{c}{L}_E{\stackrel{\·}{i}}_{Ed}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d}\\ L_E{\stackrel{\·}{i}}_{Eq}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q}\end{array}\right.$

Series side converter is meritorious and idle for control objectives with control circuit, and its state equation is:

$\left\{\begin{array}{c}L{\stackrel{\·}{i}}_{Bd}=-{\mathrm{Ri}}_{Bd}+{\mathrm{\ωLi}}_{Bq}+u_{Bd}+u_{2d}\\ L{\stackrel{\·}{i}}_{Bq}=-{\mathrm{Ri}}_{Bq}-{\mathrm{\ωLi}}_{Bd}+u_{Bq}+u_{2q}\end{array}\right.$

Wherein: L _eand R _erepresent UPFC shunt transformer and connect equivalent inductance and the resistance of reactance; i _edand i _eqbe respectively UPFC side in parallel output current coordinate components, u _sdand u _sqbe respectively electrical network sending end busbar voltage, u _1dand u _1qfor the output voltage of UPFC parallel converters; ω is electrical network angular speed;

L=L _b+ L _n, R=R _b+ R _n, L _band R _brepresent respectively UPFC series transformer connect equivalent inductance and the resistance of reactance, L _nand R _nrepresent equivalent inductance and the resistance of circuit respectively, i _bdand i _bqrepresent the electric current coordinate components that circuit and UPFC series side flow through respectively, u _2dand u _2qfor the output voltage of UPFC series converter, u _bdand u _bqbe respectively the AC output voltage of series connection converter.

Carry out equivalence according to above-mentioned state equation to the circuit structure of UPFC, side in parallel and series side equivalent circuit diagram are as depicted in figs. 1 and 2.

Step 2: the actual conditions according to system select Terminal sliding moding structure, comprise the number of I/O variable, the parameter parity of sliding-mode surface, exponent number.

Electric power system is the complication system of a nonlinear time-varying, one D controller (single input variable) is difficult to meet control overflow, and three-dimensional and above controller control law is complicated, in reality, be difficult to accurate acquisition, so suggestion application two dimension controller more widely.Find a suitable switching function S, meet

$s-\stackrel{\·}{x}+{\mathrm{\βx}}^{q/p}=0$

Wherein: x ∈ R is state variable, β >0, p, q (p>q) are positive odd number, controller parameter φ, γ >0.The system convergence speed when principle equilibrium state, when system is close to equilibrium state, Nonlinear Sliding mode convergence rate is comparatively slow, therefore, improve overall situation Terminal sliding mode fast, and parameter meets requirement above:

$\stackrel{\·}{s}=-\mathrm{\φ}s-\mathrm{\γ}{\left|s\right|}^{q/p}$

For above sliding mode function, need to adopt suitable parameter to reach the object of Fast Convergent.

Step 3: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design side in parallel Terminal Sliding mode variable structure control.

Determine the structure of quick Terminal Sliding mode variable structure system, according to quick Terminal Sliding Mode Controller method for designing design parallel inverter control strategy, the state variable of selecting system

x ₁＝i _Ed

x ₂＝i _Eq

Get sliding mode variable s ₁and s ₂, and differentiate

$\begin{array}{c}{\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-{\stackrel{\·}{x}}_1\\ {\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-{\stackrel{\·}{x}}_2\end{array}$

According to parallel inverter state equation,

$\begin{array}{c}{\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-\frac{1}{L_E}(-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d})\\ {\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-\frac{1}{L_E}(-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q})\end{array}$

And get the quick Terminal sliding-mode surface of second order,

$\begin{array}{c}{\stackrel{\·}{s}}_1=-{\mathrm{\φs}}_1-\mathrm{\γ}{\left|s_1\right|}^{q/p}\\ {\stackrel{\·}{s}}_2=-{\mathrm{\φs}}_2-\mathrm{\γ}{\left|s_2\right|}^{q/p}\end{array}$

Obtain the parallel inverter control strategy of final Terminal Sliding mode variable structure control fast, be also

$\begin{array}{c}{u}_{1d}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L_E\\ u_{1q}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L_E\end{array}$

Step 4: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design series side Terminal Sliding mode variable structure control.

With step 3 in like manner, choose state variable u _2dand u _2q, the quick Terminal sliding-mode surface of second order, can obtain the series connection converter control strategy of quick Terminal Sliding mode variable structure control

$\begin{array}{c}{u}_{2d}={\mathrm{Ri}}_{Bd}-{\mathrm{\ωLi}}_{Bq}-u_{Bd}+({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L\\ u_{2q}={\mathrm{Ri}}_{Bq}+{\mathrm{\ωLi}}_{Bd}-u_{Bq}+({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L\end{array}$

Step 5: consider that load current changes the DC bus-bar voltage change caused, the controller of the Terminal Sliding mode variable structure control of design DC capacitor link.

The state variable x=u of selecting system _dc, get sliding mode variable get synovial membrane face

$S=i_d^{*}-i_d=k_1(s+k_2\stackrel{\·}{s})$

Consider the power relation of DC bus-bar voltage, obtain the control electric current of electric capacity C:

$i_{Ed}^{*}=(s+k\frac{{\mathrm{du}}_{dc}^{*}}{dt}+\frac{k}{C}{i}_{load})\frac{{\mathrm{Cu}}_{dc}}{k(u_{sd}-R_E{i}_{Ed})}$

Wherein: k, k ₁, k ₂be controller parameter, be all greater than 0; u _dcrepresent DC tache voltage; i _loadrepresent load current.

Step 6: export target desired control signal according to the physical meaning selected amount survey calculation of target variable, and control by space vector (SVPWM) triggering signal obtaining series side and side in parallel converter.

Physical meaning according to target variable provides the desired value of system state variables, and computing formula is as follows:

$\begin{array}{c}{i}_{Bd}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2d}+Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}\\ i_{Bq}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2q}-Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}\end{array}$

In formula: P, Q represent that circuit is gained merit and reactive power desired value respectively.SVPWM technology is comparatively ripe, repeats no more herein.UPFC side in parallel and series side control principle block diagram are as shown in Figure 3 and Figure 4.

If Fig. 5 is that two machine two-wires are containing UPFC transmission system topological structure.In MATLAB, set up electromagnetic transient simulation model, build controller module and primary system simulation model according to above control method, different disturbances is set in emulation to verify the stability of controller.Select different running situation to carry out electromagnetic transient simulation, after disturbance, system responses situation and other control methods contrast as can be seen from figures 6 to 8.

Can be found out by the contrast of control effects: when System control structures and system operating point do not change, it is suitable that control method based on quick Terminal Sliding mode variable structure control compares traditional control method effect, larger damping can be provided to system, reach control objectives desired value fast, improve the safety and stability performance of system; When changing at System control structures or system operating point, due to the advantage of quick Terminal sliding moding structure strong robustness, so the successful of double quick speed Terminal Sliding mode variable structure control is better than additive method, illustrate that double quick speed Terminal sliding mode variable structure control method has better adaptability to system, robustness is better, even under system has delay and the uncertain situation of system model structure and parameter, also has good control effects.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (7)

1. the UPFC control method of quick Terminal sliding moding structure, is characterized in that, comprise the steps:

Step one: utilize the method for vector control and the method for coordinate transform to carry out decoupling zero to the system mathematic model set up, thus obtain the system state equation being convenient to Sliding mode variable structure control;

Step 2: the actual conditions according to system select Terminal sliding moding structure, comprise the number of I/O variable, the parameter parity of sliding-mode surface, exponent number;

Step 3: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design side in parallel Terminal Sliding mode variable structure control;

Step 4: according to the method for Terminal Sliding mode variable structure control, the controller of combining target Variational Design series side Terminal Sliding mode variable structure control;

Step 5: consider that load current changes the DC bus-bar voltage change caused, the controller of the Terminal Sliding mode variable structure control of design DC capacitor link;

Step 6: export target desired control signal according to the physical meaning selected amount survey calculation of target variable, and obtain the triggering signal of series side and side in parallel converter by Frequency conversion control.

2. the UPFC control method of quick Terminal sliding moding structure according to claim 1, is characterized in that: the system state equation described in step one is as follows:

Side in parallel converter is with the grid-connected point voltage of control system and idle for control objectives, and its state equation is:

$\left\{\begin{array}{c}{L}_E{\stackrel{\·}{i}}_{Ed}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d}\\ L_E{\stackrel{\·}{i}}_{Eq}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q}\end{array}\right.$

Series side converter is meritorious and idle for control objectives with control circuit, and its state equation is:

$\left\{\begin{array}{c}L{\stackrel{\·}{i}}_{Bd}=-{\mathrm{Ri}}_{Bd}+{\mathrm{\ωLi}}_{Bq}+u_{Bd}+u_{2d}\\ L{\stackrel{\·}{i}}_{Bq}=-{\mathrm{Ri}}_{Bq}-{\mathrm{\ωLi}}_{Bd}+u_{Bq}+u_{2q}\end{array}\right.$

Wherein: L _eand R _erepresent UPFC shunt transformer and connect equivalent inductance and the resistance of reactance; i _edand i _eqbe respectively UPFC side in parallel output current coordinate components, u _sdand u _sqbe respectively electrical network sending end busbar voltage, u _1dand u _1qfor the output voltage of UPFC parallel converters; ω is electrical network angular speed;

L=L _b+ L _n, R=R _b+ R _n, L _band R _brepresent respectively UPFC series transformer connect equivalent inductance and the resistance of reactance, L _nand R _nrepresent equivalent inductance and the resistance of circuit respectively, i _bdand i _bqrepresent the electric current coordinate components that circuit and UPFC series side flow through respectively, u _2dand u _2qfor the output voltage of UPFC series converter, u _bdand u _bqbe respectively the AC output voltage of series connection converter.

3. the UPFC control method of quick Terminal sliding moding structure according to claim 3, is characterized in that: the Terminal sliding moding structure described in step 2, meets:

$s-\stackrel{\·}{x}+{\mathrm{\βx}}^{q/p}=0$

$\stackrel{\·}{s}=-\mathrm{\φ}s-\mathrm{\γ}{\left|s\right|}^{q/p}$

Wherein: S represents switching function, represent the differential of S; X ∈ R is state variable, represent the differential of x; β >0; P, q are positive odd number, and p is greater than q, φ >0, γ >0.

4. the UPFC control method of quick Terminal sliding moding structure according to claim 3, is characterized in that: the concrete steps designing the controller of side in parallel Terminal Sliding mode variable structure control described in step 3 are as follows:

Determine the structure of quick Terminal Sliding mode variable structure system, according to quick Terminal Sliding Mode Controller method for designing design parallel inverter control strategy, the state variable of selecting system

x ₁＝i _Ed

x ₂＝i _Eq

Get sliding mode variable s ₁and s ₂, and differentiate

${\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-{\stackrel{\·}{x}}_1$

${\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-{\stackrel{\·}{x}}_2$

According to parallel inverter state equation,

${\stackrel{\·}{s}}_1={\stackrel{\·}{i}}_{Ed}^{*}-\frac{1}{L_E}(-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-u_{1d})$

${\stackrel{\·}{s}}_2={\stackrel{\·}{i}}_{Eq}^{*}-\frac{1}{L_E}(-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-u_{1q})$

And get the quick Terminal sliding-mode surface of second order,

${\stackrel{\·}{s}}_1=-{\mathrm{\φs}}_1-\mathrm{\γ}{\left|s_1\right|}^{q/p}$

${\stackrel{\·}{s}}_2=-{\mathrm{\φs}}_2-\mathrm{\γ}{\left|s_2\right|}^{q/p}$

Obtain the parallel inverter control strategy of final Terminal Sliding mode variable structure control fast, be also

$u_{1d}=-R_E{i}_{Ed}+{\mathrm{\ωL}}_E{i}_{Eq}+u_{sd}-({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L_E$

$u_{1q}=-R_E{i}_{Eq}-{\mathrm{\ωL}}_E{i}_{Ed}+u_{sq}-({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L_E.$

5. the UPFC control method of quick Terminal sliding moding structure according to claim 4, is characterized in that: the step designing the controller of series side Terminal Sliding mode variable structure control described in step 4 is as follows:

Choose state variable u _2dand u _2q, the quick Terminal sliding-mode surface of second order, obtains the series connection converter control strategy of quick Terminal Sliding mode variable structure control:

$u_{2d}={\mathrm{Ri}}_{Bd}-{\mathrm{\ωLi}}_{Bq}-u_{Bd}+({\stackrel{\·}{i}}_{Ed}^{*}+{\mathrm{\φs}}_1+\mathrm{\γ}{\left|s_1\right|}^{q/p})L$

$u_{2q}={\mathrm{Ri}}_{Bq}+{\mathrm{\ωLi}}_{Bd}-u_{Bq}+({\stackrel{\·}{i}}_{Eq}^{*}+{\mathrm{\φs}}_2+\mathrm{\γ}{\left|s_2\right|}^{q/p})L.$

6. the UPFC control method of quick Terminal sliding moding structure according to claim 5, is characterized in that: the controller step designing the Terminal Sliding mode variable structure control of DC capacitor link described in step 5 is as follows:

The state variable x=u of selecting system _dc, get sliding mode variable get synovial membrane face

$S=i_d^{*}-i_d=k_1(s+k_2\stackrel{\·}{s})$

Consider the power relation of DC bus-bar voltage, obtain the control electric current of electric capacity C:

$i_{Ed}^{*}=(s+k\frac{{\mathrm{du}}_{dc}^{*}}{dt}+\frac{k}{C}{i}_{load})\frac{{\mathrm{Cu}}_{dc}}{k(u_{sd}-R_E{i}_{Ed})}$

Wherein: k, k ₁, k ₂be controller parameter, be all greater than 0; u _dcrepresent DC tache voltage; i _loadrepresent load current.

7. the UPFC control method of quick Terminal sliding moding structure according to claim 6, is characterized in that: target desired value described in step 6 is calculated by following formula and tries to achieve:

$i_{Bd}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2d}+Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}$

$i_{Bq}^{*}=\frac{2}{3}\frac{P^{*}{u}_{2q}-Q^{*}{u}_{2q}}{{u_{2d}}^2+{u_{2q}}^2}$

In formula: P, Q represent that circuit is gained merit and reactive power desired value respectively.