CN107994565B - A simulation method and system of unified power flow controller - Google Patents

Abstract

The invention provides a simulation method for a unified power flow controller, comprising: obtaining steady-state operation parameters required for power flow calculation of a power system; The series-side converter model obtains the control signals of the parallel-side and series-side of the unified power flow controller; the parallel-side converter model and the series-side converter model both include dual-loop control and mode selection. The invention can accurately simulate the power transmission characteristics of the UPFC, can simulate the situation of excessive current caused by the short circuit of the UPFC during operation, and can conveniently control the currents of the d-axis and the q-axis.

Description

A simulation method and system of unified power flow controller

technical field

The invention relates to the field of control simulation in the field of power systems, in particular to a simulation method and system of a unified power flow controller.

Background technique

With the expansion of the scale of the power grid, the problems of uneven distribution of power generation and load in the region, and uneven distribution of power flow of power transmission and transformation equipment have become increasingly prominent. The problems of heavy and light load of equipment coexist, and are subject to the bearing capacity of heavy-load equipment and the power supply capacity of the power grid. Hard to take full advantage of. In addition, due to the limitation of urban planning, it is increasingly difficult to reconstruct the line and expand the power grid. Therefore, on the basis of the existing grid, how to improve the power transmission capacity of the power grid, improve the power flow distribution of the power grid, and ensure the safe operation of the power grid is an urgent problem to be solved at present.

It is a realistic and ideal choice to increase the transmission capacity of the power grid by adopting the new FACTS device to improve the operating conditions of the system. The typical representative of the third-generation FACTS equipment, the Unified Power Flow Controller (UPFC), is the flexible AC transmission device with the most comprehensive functions, the widest control range and the most superior characteristics so far. UPFC can quickly control the voltage amplitude of the controlled bus and the active and reactive power of the controlled line independently or simultaneously by adjusting the amplitude and phase angle of the output voltage of the series-side and parallel-side converters. The distribution of power flow and the improvement of power transmission capacity of the line provide new ideas and new technologies. Therefore, the application of UPFC in practical engineering has obvious technical advantages and broad application prospects.

The rapid development and application of UPFC have put forward higher requirements for power system simulation. The existing UPFC control models are mostly suitable for electromechanical transients or electromagnetic transients, and the simulation speed obviously cannot meet the actual needs of the power system.

SUMMARY OF THE INVENTION

In order to solve the problem in the prior art that the simulation speed of the existing UPFC control model obviously cannot meet the actual needs of the power system, the present invention provides a simulation method and system for a unified power flow controller.

The technical scheme provided by the present invention is: a simulation method of a unified power flow controller, the method comprises:

Obtain steady-state operating parameters required for power system power flow calculation;

Based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller, the control signals of the parallel-side and series-side converters of the unified power flow controller are obtained;

Both the parallel-side inverter model and the series-side inverter model include dual-loop control and mode selection.

Preferably, the obtaining steady-state operating parameters required for power flow calculation of the power system includes:

The voltage and current values of the series/parallel side measured by the measurement system are calculated to obtain the actual value of the parallel side reactive power, the actual value of the series side active power and the actual value of the series side reactive power. The actual values of side DC voltage and series/parallel side reactive power are converted into corresponding per-unit values.

Preferably, the active power per unit value is calculated as follows:

P=Vd*Id+Vq*Iq

In the formula, P: per-unit value of active power; Vd: the component of the measured voltage on the d-axis; Id: the component of the measured current on the d-axis; Vq: the component of the measured voltage on the q-axis, Iq: Component of the measured current on the q-axis.

Preferably, the reactive power per unit value is calculated as follows:

Q=Vq*Id-Vd*Iq

In the formula, Q: per unit value of reactive power; Vd: measured voltage d-axis component; Id: measured current d-axis component; Vq: measured voltage q-axis component, Iq: measured current q-axis weight.

Preferably, the measured voltage d-axis component Vd is calculated as follows:

In the formula, Va: a-phase line voltage on the series/parallel side; Vb: b-phase line voltage on the series/parallel side: Vc: c-phase line voltage on the series/parallel side; ω: phase angle; t: time;

The measured voltage q-axis component Vq is calculated as follows:

Preferably, the control signals for the parallel side and the series side of the unified power flow controller are obtained based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller, including: :

Based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller, the AC voltage dq-axis reference value is obtained;

The control signals of the parallel side and the series side of the unified power flow controller are calculated from the dq axis reference value of the AC voltage, the modulation depth and the phase shift angle.

Preferably, the parallel-side converter model of the unified power flow controller includes:

Based on the voltage, current, reactive power per unit value and DC voltage per unit value of the parallel side as the input of the outer loop reactive power control, outer loop AC voltage control and outer loop DC voltage control, the dq axis reference of the parallel side AC current is obtained value;

The reference value of the AC current q-axis of the parallel side is processed by active power priority and the reference value of the AC current d-axis output by the DC voltage control of the outer loop is used as the input of the current control of the inner loop, and the reference value of the AC voltage dq-axis after the processing of the inner loop is output. value.

Preferably, the inner loop current control of the parallel side is calculated as follows:

U _cd =U _sd -(K _P1 (i _sdref -i _sd )+K _I1 ∫(i _sdref -i _sd )dt)+ωLi _sq

In the formula, U _cd : the d-axis component of the voltage fundamental wave on the AC side of the converter; U _sd : the d-axis component of the grid voltage; K _P1 : gain coefficient; K _I1 : gain coefficient; _isdref : reference value of active current ; i _sd : the d-axis component of the grid current; ω: the phase angle; L: the equivalent inductance of the transformer plus phase reactor on the parallel side; i _sq : the q-axis component of the grid current;

U _cq =-(K _P2 (i _sqref -i _sq )+K _I2 ∫(i _sqref -i _sq )dt)-ωLi _sd

In the formula, U _cq : the q-axis component of the voltage fundamental wave on the AC side of the converter; ω represents the power frequency angular frequency; i _sqref : the reference value of the reactive current; K _P2 : gain coefficient; K _I2 : gain coefficient.

Preferably, it also includes: setting mode selection between the outer loop reactive power control, outer loop AC voltage control, outer loop DC voltage control and the inner loop current control on the parallel side;

The mode selection includes: UPFC power control mode and parallel side STATCOM reactive power control mode.

Preferably, the series-side converter model of the unified power flow controller includes:

Based on the voltage, current, per-unit value of reactive power and per-unit value of active power on the series side as the input of the outer-loop reactive power controller and the outer-loop active power controller, the reference value of the series-side AC current dq axis is obtained; and The series-side AC current dq-axis reference value is used as the input of the inner loop current controller, and the dq-axis reference value of the AC voltage controlled by the inner and outer loops is output.

Preferably, the inner loop current control on the series side is calculated as follows:

U _cd =U _sd +(K _P1 (i _sdref -i _sd )+K _I1 ∫(i _sdref -i _sd )dt)-ωLi _sq

In the formula, U _cd : the d-axis component of the fundamental wave of the AC side voltage of the converter; U _sd : the d-axis component of the grid voltage; K _P1 : gain coefficient; K _I1 : gain coefficient; i _sdref : the reference representing the active current value; i _sd : the d-axis component of the grid current; ω: phase angle; L: the equivalent inductance of the transformer plus phase reactor on the parallel side; i _sq : the q-axis component of the grid current;

U _cq =U _sq +(K _P2 (i _sqref -i _sq )+K _I2 ∫(i _sqref -i _sq )dt)+ωLi _sd

In the formula, U _cd : the d-axis component of the voltage fundamental wave on the AC side of the converter; U _cq : the q-axis component of the voltage fundamental wave on the AC side of the converter; U _sq : the q-axis component of the grid voltage; K _P2 : gain coefficient; K _I2 : gain coefficient; i _sqref represents the reference value of reactive current.

Preferably, it also includes: setting mode selection after the series-side inner loop current control;

The mode selection includes: UPFC power control mode and series side manual voltage injection mode.

A simulation system for a unified power flow controller, the system includes:

The parameter acquisition module is used to acquire the steady-state operating parameters required for the power flow calculation of the power system;

A signal generation module for obtaining control signals for the parallel side and the series side of the unified power flow controller based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller ;

Model building block for building parallel-side converter models and series-side converter models with dual-loop control and mode selection.

Preferably, the model building module includes: a parallel-side converter model building sub-module and a series-side converter model building sub-module;

The parallel-side converter model building sub-module includes: after the outer loop AC voltage controller, the outer loop reactive power controller and the outer DC voltage controller are connected in parallel, the inner loop current controller and the modulation depth and phase shift angle are connected in series in sequence. calculation module;

The series-side converter model building sub-module includes: the outer-loop active power controller and the outer-loop reactive power controller are connected in parallel with the inner-loop current controller and the modulation depth and phase-shift angle calculation modules in sequence.

Preferably, the parallel-side converter model building sub-module further includes: a series mode selection module after the outer-loop AC voltage controller and the outer-loop reactive power controller are connected in parallel, and then connected with the outer-loop DC voltage controller in parallel.

Preferably, the series-side converter model building sub-module further includes: a mode selection module is arranged between the series-side inner loop current controller and the modulation depth and phase shift angle calculation module.

Compared with the prior art, the beneficial effects of the present invention are:

The technical solution provided by the present invention is based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller including dual-loop control and mode selection, to obtain the unified power flow controller model. The control signals of the parallel side and the series side take into account the influence of the series-parallel side converters, transformers and other parameters on the dynamic performance of the UPFC, which can accurately and quickly simulate the power transmission characteristics of the UPFC.

The technical scheme provided by the present invention adds mode selection to make the control modes more diverse and meet actual needs.

The technical solution provided by the present invention considers the influence of excessive active current and reactive current, and adds a current limiter that prioritizes active power, which can simulate the situation of excessive current caused by a short circuit in the UPFC during operation.

In the control system of the series-parallel side converter, the technical solution provided by the present invention obtains mutually independent inner loop current controllers through decoupling, which can conveniently control the currents of the d-axis and the q-axis.

Description of drawings

Fig. 1 is the flow chart of the simulation method of the unified power flow controller of the present invention;

Fig. 2 is the overall structure diagram of unified power flow controller control logic simulation provided by the present invention;

FIG. 3 is a control diagram of the parallel side outer loop AC voltage provided by the present invention;

Fig. 4 is the reactive power control diagram of the parallel side outer loop provided by the present invention;

5 is a control diagram of a parallel-side outer loop DC voltage provided by the present invention;

Fig. 6 is the control diagram of the inner loop current of the parallel side through decoupling provided by the present invention;

Fig. 7 is the active power control diagram of the series side outer loop provided by the present invention;

Fig. 8 is the reactive power control diagram of the series side outer loop provided by the present invention;

Fig. 9 is the decoupling inner loop current control diagram of the series side provided by the present invention;

FIG. 10 is a schematic diagram of current output limiting provided by the present invention.

Detailed ways

In order to better understand the present invention, the content of the present invention will be further described below with reference to the accompanying drawings and examples.

The present invention proposes a simulation method suitable for UPFC control logic. As shown in Figure 1, the simulation method of the unified power flow controller includes:

Obtain steady-state operating parameters required for power system power flow calculation;

Based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller, the control signals of the parallel side and the series side of the unified power flow controller are obtained;

Both the parallel-side converter model and the series-side converter model include dual-loop control and mode selection.

The functional structure of the UPFC control logic is shown in Figure 2. The model has a reasonable structure, good operability and adaptability, and can correctly simulate the dynamic characteristics of the UPFC under normal and short-circuit conditions.

The UPFC control structure diagram includes: processing on the parallel side and processing on the series side.

Processing on the parallel side: The data measured by the UPFC measurement system is processed as the input for the parallel side outer loop AC voltage control, the parallel side outer loop reactive power control and the parallel side outer loop DC voltage control, and the parallel side outer loop AC voltage control and The output of the parallel-side outer-loop reactive power control is used as the input of the parallel-side mode selection, and its output value is processed by active power priority and the output of the parallel-side outer-loop DC voltage control is used as the parallel-side inner-loop current control input. The output of the inner loop current control is used as the input of the modulation depth and phase shift angle calculation, and the parallel side control signal is obtained through the modulation depth and phase shift angle calculation.

Processing on the series side: The data measured by the UPFC measurement system is processed as the input of the series side outer loop active power control and the series side outer loop reactive power control, the series side outer loop active power control and the series side outer loop reactive power control. The output is used as the input of the inner loop current control on the series side, its output and the manual injection value of the AC voltage dq axis component on the series side are used as the input of mode selection, and the value after mode selection is used as the input for the calculation of modulation depth and phase shift angle. The depth and phase shift angle are calculated to obtain the series side control signal.

(1) Obtain the steady-state operating parameters required for power flow calculation of the power system

Establish a UPFC measurement system, obtain the d-axis and q-axis components of the voltage and current on the series side and parallel side of the primary system, and obtain the actual value of the reactive power on the parallel side through calculation, and the actual value of the active power and reactive power on the series side. The power and voltage reference value of the UPFC measurement system is converted into per-unit value; the analytical expression of the dq-axis transformation of the UPFC measurement system is as follows:

Where Va, Vb, Vc represent the three-phase line voltage or three-phase line current on the series/parallel side, respectively.

Active power and reactive power can be calculated from the voltage dq axis component and the current dq axis component. After averaging and filtering, the per-unit values of active power and reactive power for control can be obtained, and the expressions are as follows:

P=Vd*Id+Vq*Iq <3>

Q=Vq*Id-Vd*Iq<4>;

Among them: Vd and Vq are the dq-axis components of the voltage, and Id and Iq are the dq-axis components of the current.

(2) Use the parallel side voltage, current d-axis, q-axis components, parallel side reactive power per unit value and DC voltage per unit value obtained in step (1) as the outer loop AC voltage control, outer loop reactive power control, The input of the outer-loop DC voltage control is used to obtain the reference values of the d-axis and q-axis of the parallel side AC current; the outer-loop AC voltage controller, the outer-loop reactive power controller, and the outer-loop DC voltage controller all use limited amplitude PI controllers , as shown in Figure 3, Figure 4, Figure 5;

(3) Using the voltage and current dq-axis components on the series side and the per-unit values of the active power and reactive power on the series side obtained in step (1) as the input of the outer-loop active power control and the outer-loop reactive power control to obtain the series-side AC The current d-axis and q-axis reference values; the outer-loop active power controller and the outer-loop reactive power controller all use limited-amplitude PI controllers, as shown in Figures 7 and 8.

(4) Input the reference value of the parallel-side AC current q-axis obtained in step (2) into the mode selection, and obtain the selected parallel-side AC current q-axis reference value according to the set mode;

Parallel side mode selection includes UPFC power control mode and parallel side STATCOM reactive power control mode.

Parallel-side STATCOM reactive power control mode: stabilize the AC voltage of the parallel-side busbar and stabilize the DC-side voltage;

UPFC power control mode: control line active power and reactive power.

(5) Input the reference value of the series side AC current dq axis obtained in step (3) into the series side inner loop current control module to obtain the parallel side AC voltage dq axis reference value; Fig. 9 is a block diagram of the series side inner loop current control, The decoupling control method is used in the inner loop current control:

Orienting the d-axis of the synchronous rotating coordinate system on the series side to the voltage vector of the AC grid on the parallel side, in the same way, the expression of the inner loop current controller on the series side can be obtained as:

U _cd =U _sd +(K _P1 (i _sdref -i _sd )+K _I1 ∫(i _sdref -i _sd )dt)-ωLi _sq <5>

U _cq =U _sq +(K _P2 (i _sqref -i _sq )+K _I2 ∫(i _sqref -i _sq )dt)+ωLi _sd <6>;

(6) Input the dq-axis reference value of the series-side AC voltage and the dq-axis component manual injection value of the series-side AC voltage obtained in step (5) into the mode selection module, and obtain the selected series-side AC voltage according to the set mode dq axis reference value;

The series measurement mode selection includes: UPFC power control mode and series side manual voltage injection mode.

UPFC power control mode: control line active power and reactive power;

Series side manual voltage injection mode: Compared with the power control mode, the control effect is to inject a certain voltage on the series side, which can increase the voltage at the end of the line to a specific value.

不能超过限幅；优先保证I_d的大小，对I_q进行限幅，即限幅后的并联侧交流电流q轴参考值为：(7) Input the q-axis reference value of the parallel side AC current obtained in step (4) into the current limiting module, and the output limits the current according to the active power priority principle to obtain the parallel side AC current q-axis reference value; Figure 10 shows the current limit Schematic diagram, in which the active power priority principle is: after obtaining I _d and I _q , consider the total current

The limit cannot be exceeded; the priority is to ensure the size of I _d , and the limit of I _q is performed, that is, the reference value of the q-axis of the parallel side AC current after the limit is:

(8) Input the parallel-side AC current d-axis reference value obtained in step (2) and the series-side AC current q-axis reference value obtained in step (7) into the parallel-side inner loop current control, and output the parallel-side AC voltage dq-axis Reference value; Figure 6 is a block diagram of the inner loop current control on the parallel side, and the decoupling control method is used in the inner loop current control:

Combined with the structural parameters of the UPFC series-parallel side converter and transformer, the inner loop current controller of the series-parallel side converter using the decoupling control method in the dq-axis coordinate system is obtained:

The mathematical expression of the inner loop current controller on the parallel side is as follows:

ΔU_d＝ωLi_sd；ΔU_q＝ωLi_sq；U_cd和U_cq为换流器交流侧电压基波的d轴、q轴分量；U_sd、U_sq分别为电网电压的d、q轴分量；i_sd、i_sq分别为电网电流的d、q轴分量；

和

采用下式的比例积分环节来实现：in,

ΔU _d =ωLi _sd ; ΔU _q =ωLi _sq ; U _cd and U _cq are the d-axis and q-axis components of the AC side voltage fundamental wave of the converter; U _sd and U _sq are the d- and q-axis components of the grid voltage, respectively; i _sd and i _sq are the d and q axis components of the grid current, respectively;

and

The proportional integral link of the following formula is used to achieve:

In the inner loop current controller, there are cross-coupling terms ωLi _d and ωLi _q , namely the ΔU _d and ΔU _q terms in the formula, and the current state feedback quantities ωLi _d and ωLi _q are introduced to decouple; The axis is oriented to the voltage vector of the AC grid on the parallel side, we can get:

U _sd =U _s <12>

U _sq = 0 <13>

Among them, U _s is the phase voltage peak value of the AC power grid on the parallel side.

Combining the above formulas, the expression of the parallel side inner loop current controller is:

U _cd =U _sd -(K _P1 (i _sdref -i _sd )+K _I1 ∫(i _sdref -i _sd )dt)+ωLi _sq <14>

U _cq =-(K _P2 (i _sqref -i _sq )+K _I2 ∫(i _sqref -i _sq )dt)-ωLi _sd <15>

<8>;

The d-axis and q-axis controlled by the inner loop form two completely independent control loops, which control the current of the d-axis and the q-axis respectively;

Among them: L is the equivalent inductance of the transformer phase reactor on the parallel side, ω is the power frequency angular frequency, i _sdref , i _sqref are the reference values of active current and reactive current respectively, K _P1 , K _P2 , K _I1 , K _I2 is the gain coefficient.

(9) Input the dq-axis reference value of the series-side AC voltage obtained in step (6) and the dq-axis reference value of the parallel-side AC voltage obtained in step (8) into the modulation depth and phase-shift angle calculation module to obtain the control signal;

(10) The modulation depth and phase shift angle obtained in step (9) are input into the series-parallel side converter model, so as to realize the voltage and current control of the inner and outer loops.

The simulation method of UPFC control logic according to the present invention has good operability and adaptability, can correctly simulate the dynamic characteristics of UPFC under normal working conditions and short-circuit conditions, and can be applied to the simulation of UPFC electromagnetic transient.

A simulation system for a unified power flow controller, characterized in that the system includes:

The parameter acquisition module is used to acquire the steady-state operating parameters required for the power flow calculation of the power system;

A signal generation module for obtaining control signals for the parallel side and the series side of the unified power flow controller based on the steady-state operating parameters and the pre-established parallel-side converter model and series-side converter model of the unified power flow controller ;

Model building block for building parallel-side converter models and series-side converter models with dual-loop control and mode selection.

The model building module includes: a parallel-side converter model building sub-module and a series-side converter model building sub-module;

The parallel-side converter model building sub-module includes: after the outer loop AC voltage controller, the outer loop reactive power controller and the outer DC voltage controller are connected in parallel, the inner loop current controller and the modulation depth and phase shift angle calculation modules are connected in series in sequence. ;

The sub-module of the series-side converter model construction includes: the outer-loop active power controller and the outer-loop reactive power controller are connected in parallel with the inner-loop current controller and the modulation depth and phase-shift angle calculation modules in series.

The parallel-side converter model building sub-module further includes: a series mode selection module after the outer-loop AC voltage controller and the outer-loop reactive power controller are connected in parallel, and then connected in parallel with the outer-loop DC voltage controller.

The series-side converter model building sub-module further includes: a mode selection module is arranged between the series-side inner loop current controller and the modulation depth and phase-shift angle calculation module.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

The above are only examples of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the application for pending approval of the present invention. within the scope of the claims.

Claims (13)

1. A simulation method of a unified power flow controller is characterized by comprising the following steps:

acquiring steady-state operation parameters required by power flow calculation of the power system;

obtaining control signals of the parallel side and the series side of the unified power flow controller based on the steady-state operation parameters and a pre-established parallel side converter model and a pre-established series side converter model of the unified power flow controller;

the parallel side converter model and the series side converter model both comprise double-loop control and mode selection;

the step of obtaining control signals of the parallel side and the series side of the unified power flow controller based on the steady-state operation parameters and a pre-established parallel side converter model and a pre-established series side converter model of the unified power flow controller comprises the following steps:

obtaining an alternating-current voltage dq axis reference value based on the steady-state operation parameters and a pre-established parallel side converter model and a pre-established series side converter model of the unified power flow controller;

calculating to obtain control signals of the parallel side and the series side of the unified power flow controller according to the alternating voltage dq axis reference value, the modulation depth and the phase shift angle;

the parallel side converter model of the unified power flow controller comprises:

obtaining a parallel side alternating current dq axis reference value based on the voltage, current, reactive power per unit value and direct current voltage per unit value of the parallel side as the input of outer ring reactive power control, outer ring alternating current voltage control and outer ring direct current voltage control;

and the parallel side alternating current q-axis reference value is used as the input of the inner ring current control after limiting the current according to the active power priority principle and the alternating current d-axis reference value output by the outer ring direct current voltage control, and the alternating voltage dq-axis reference value processed by the inner ring is output.

2. The simulation method of claim 1, wherein the obtaining steady-state operating parameters required for power system load flow calculation comprises:

and calculating the voltage and current values of the series/parallel sides measured by the measuring system to obtain an actual reactive power value of the parallel side, an actual active power value of the series side and an actual reactive power value of the series side, and converting the actual active power value of the series side, the actual direct-current voltage of the parallel side and the actual reactive power value of the series/parallel sides into corresponding per unit values.

3. The simulation method according to claim 2, wherein the active power per unit value is calculated according to the following formula:

P＝Vd*Id+Vq*Iq

in the formula, P: an active power per unit value; vd: the component of the measured voltage on the d-axis; id: the component of the measured current on the d-axis; and Vq: component of the measured voltage on the q-axis, Iq: the component of the measured current on the q-axis.

4. The simulation method according to claim 2, wherein the per-unit value of reactive power is calculated as follows:

Q＝Vq*Id-Vd*Iq

in the formula, Q: a reactive power per unit value; vd: a measured d-axis component of the voltage; id: a measured d-axis component of the current; and Vq: measured voltage q-axis component, Iq: the measured q-axis component of the current.

5. A simulation method according to claim 3 or 4, wherein the measured voltage d-axis component Vd is calculated as:

in the formula, Va: a phase line voltage of the serial/parallel side; vb: b-phase line voltage on the series/parallel side: vc: c-phase line voltage of the serial/parallel side; ω: a phase angle; t: time;

the measured voltage q-axis component Vq is calculated as:

6. the simulation method of claim 1, wherein the inner loop current control of the parallel side is calculated as:

U_cd＝U_sd-(K_P1(i_sdref-i_sd)+K_I1∫(i_sdref-i_sd)dt)+ωLi_sq

in the formula of U_cd: d-axis component of voltage fundamental wave at AC side of the converter; u shape_sd: is the d-axis component of the grid voltage; k_P1: a gain factor; k_I1: a gain factor; i.e. i_sdref: a reference value of active current; i.e. i_sd: is the d-axis component of the grid current; ω: a phase angle; l: equivalent inductance of the parallel side transformer plus phase reactor; i.e. i_sq: is the q-axis component of the grid current;

U_cq＝-(K_P2(i_sqref-i_sq)+K_I2∫(i_sqref-i_sq)dt)-ωLi_sd

in the formula of U_cq: a q-axis component of a fundamental wave of the AC side voltage of the converter; omega represents the power frequency angular frequency; i.e. i_sqref: a reference value of reactive current; k_P2: a gain factor; k_I2: a gain factor.

7. The simulation method of claim 1, further comprising: setting mode selection among outer ring reactive power control, outer ring alternating current voltage control, outer ring direct current voltage control and inner ring current control on the parallel side;

the mode selection includes: a UPFC power control mode and a parallel side STATCOM reactive power control mode.

8. The simulation method of claim 1, wherein the series side converter model of the unified power flow controller comprises:

obtaining a series side alternating current dq axis reference value based on the voltage, current, reactive power per unit value and active power per unit value of the series side as the input of an outer ring reactive power controller and an outer ring active power controller; and the series side alternating current dq axis reference value is used as the input of the inner loop current controller, and the alternating voltage dq axis reference value controlled by the inner loop is output.

9. The simulation method of claim 8, wherein the alternating voltage dq-axis reference value of the inner loop control is calculated as:

U_cd＝U_sd+(K_P1(i_sdref-i_sd)+K_I1∫(i_sdref-i_sd)dt)-ωLi_sq

in the formula of U_cd: d-axis component of voltage fundamental wave at AC side of the converter; u shape_sd: is the d-axis component of the grid voltage; k_P1: a gain factor; k_I1: a gain factor; i.e. i_sdref: a reference value representing an active current; i.e. i_sd: is the d-axis component of the grid current; ω: a phase angle; l: equivalent inductance of parallel side transformer plus phase reactor；i_sq: is the q-axis component of the grid current;

U_cq＝U_sq+(K_P2(i_sqref-i_sq)+K_I2∫(i_sqref-i_sq)dt)+ωLi_sd

in the formula of U_cd: d-axis component of voltage fundamental wave at AC side of the converter; u shape_cq: a q-axis component of a fundamental wave of the AC side voltage of the converter; u shape_sq: is the q-axis component of the grid voltage; k_P2: a gain factor; k_I2: a gain factor; i.e. i_sqrefRepresenting a reference value of reactive current.

10. The simulation method of claim 8, further comprising: obtaining a series side alternating current dq axis reference value by taking the voltage, current, reactive power per unit value and active power per unit value on the basis of the series side as the input of an outer ring reactive power controller and an outer ring active power controller; the series side alternating current dq axis reference value is used as the input of an inner loop current controller, and mode selection is set after the alternating voltage dq axis reference value controlled by an inner loop is output;

the mode selection includes: a UPFC power control mode and a series side manual voltage injection mode.

11. A simulation system for a unified power flow controller, the system comprising:

the parameter acquisition module is used for acquiring steady-state operation parameters required by power flow calculation of the power system;

the signal generation module is used for obtaining control signals of the parallel side and the series side of the unified power flow controller based on the steady-state operation parameters and a pre-established parallel side converter model and a pre-established series side converter model of the unified power flow controller;

the model building module is used for building a parallel side converter model and a series side converter model containing double-loop control and mode selection;

the model building module comprises: a parallel side converter model construction submodule and a series side converter model construction submodule;

the parallel side converter model construction submodule comprises: after the outer ring alternating current voltage controller, the outer ring reactive power controller and the outer ring direct current voltage controller are connected in parallel, the inner ring current controller and the modulation depth and phase shift angle calculation module are sequentially connected in series;

the series side converter model building submodule comprises: the outer ring active power controller and the outer ring reactive power controller are connected in parallel and then are sequentially connected in series with the inner ring current controller and the modulation depth and phase shift angle calculation module.

12. The simulation system of claim 11, wherein the parallel side converter model building submodule further comprises: the outer ring alternating current voltage controller and the outer ring reactive power controller are connected in parallel, then are connected in series with the mode selection module, and then are connected in parallel with the outer ring direct current voltage controller.

13. The simulation system of claim 11, wherein the series side converter model building submodule further comprises: and a mode selection module is arranged between the inner loop current controller and the modulation depth and phase shift angle calculation module.

Images