CN107994565B - Simulation method and system of unified power flow controller - Google Patents
Simulation method and system of unified power flow controller Download PDFInfo
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Abstract
The invention provides a simulation method of a unified power flow controller, which comprises 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 include double loop control and mode selection. The invention can accurately simulate the power transmission characteristics of the UPFC, can simulate the condition of overlarge current caused by short circuit in the operation of the UPFC, and can conveniently control the current of the d axis and the q axis.
Description
Technical Field
The invention relates to the field of control simulation in the field of power systems, in particular to a simulation method and a simulation system for a unified power flow controller.
Background
Along with the enlargement of the scale of the power grid, the problems of unbalanced power generation and load distribution in the area, uneven power flow distribution of power transmission and transformation equipment are increasingly prominent, the problems of heavy load and light load of the equipment coexist, and the bearing capacity of the heavy load equipment and the power supply capacity of the power grid are difficult to be fully utilized. In addition, due to the limitation of urban planning, the difficulty of line reconstruction and power grid extension is increasing. Therefore, 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 on the basis of the existing grid frame is a problem to be solved urgently at present.
By adopting the novel FACTS device to improve the operation condition of the system, the improvement of the transmission capacity of the power grid is a realistic and ideal choice. A representative Unified Power Flow Controller (UPFC) of a third generation FACTS device is a flexible ac power transmission device that functions most comprehensively, has the widest control range, and has the best characteristics so far. The UPFC can independently or simultaneously control the voltage amplitude of the controlled bus and the active and reactive power of the controlled line by adjusting the amplitude and phase angle of the output voltage of the current converter on the serial side and the current converter on the parallel side, and provides a new idea and a new technology for improving the power flow distribution of a power grid and improving the transmission capacity of the line, so that the UPFC has obvious technical advantages in the application of actual engineering and wide application prospect.
The rapid development and application of the UPFC puts higher demands on the power system simulation. The existing UPFC control model is mostly suitable for electromechanical transient state or electromagnetic transient state, and the simulation speed obviously cannot meet the actual requirement of a power system.
Disclosure of Invention
In order to solve the defect that the simulation speed of the existing UPFC control model in the prior art obviously cannot meet the actual requirement of a power system, the invention provides a simulation method and a simulation system of a unified power flow controller.
The technical scheme provided by the invention is as follows: a method of simulating a unified power flow controller, the method comprising:
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 include double loop control and mode selection.
Preferably, the acquiring steady-state operation parameters required by power flow calculation of the power system includes:
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.
Preferably, 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.
Preferably, the per unit reactive power value is calculated according to the following formula:
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.
Preferably, the d-axis component Vd of the measured voltage is calculated as follows:
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:
preferably, the obtaining of the 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 includes:
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;
and 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.
Preferably, the parallel side converter model of the unified power flow controller includes:
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 taking the alternating current d-axis reference value output by the outer ring direct current voltage control and the parallel side alternating current q-axis reference value after active power priority processing as the input of the inner ring current control, and outputting the alternating voltage dq-axis reference value processed by the inner ring.
Preferably, the inner loop current control of the parallel side is calculated as follows:
Ucd＝Usd-(KP1(isdref-isd)+KI1∫(isdref-isd)dt)+ωLisq
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapesd: is the d-axis component of the grid voltage; kP1: a gain factor; kI1: a gain factor; i.e. isdref: a reference value of active current; i.e. isd: 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. isq: is the q-axis component of the grid current;
Ucq＝-(KP2(isqref-isq)+KI2∫(isqref-isq)dt)-ωLisd
in the formula of Ucq: 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. isqref: a reference value of reactive current; kP2: a gain factor; kI2: a gain factor.
Preferably, the method further comprises the following steps: 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.
Preferably, the series side converter model of the unified power flow controller includes:
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 and the outer loop is output.
Preferably, the series-side inner loop current control is calculated as follows:
Ucd＝Usd+(KP1(isdref-isd)+KI1∫(isdref-isd)dt)-ωLisq
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapesd: is the d-axis component of the grid voltage; kP1: a gain factor; kI1: a gain factor; i.e. isdref: a reference value representing an active current; i.e. isd: 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. isq: is the q-axis component of the grid current;
Ucq＝Usq+(KP2(isqref-isq)+KI2∫(isqref-isq)dt)+ωLisd
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapecq: a q-axis component of a fundamental wave of the AC side voltage of the converter; u shapesq: is the q-axis component of the grid voltage; kP2: a gain factor; kI2: a gain factor; i.e. isqrefRepresenting a reference value of reactive current.
Preferably, the method further comprises the following steps: setting a mode selection after the series side inner loop current control;
the mode selection includes: a UPFC power control mode and a series side manual voltage injection mode.
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;
and the model construction module is used for constructing a parallel side converter model and a series side converter model containing double-loop control and mode selection.
Preferably, the model building module includes: 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 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.
Preferably, the parallel side converter model building submodule further includes: 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.
Preferably, the series side converter model building submodule further includes: and a mode selection module is arranged between the inner ring current controller on the series side and the modulation depth and phase shift angle calculation module.
Compared with the prior art, the invention has the beneficial effects that:
according to the technical scheme provided by the invention, based on the steady-state operation parameters and the pre-established parallel side converter model and series side converter model of the unified power flow controller comprising double-loop control and mode selection, the control signals of the parallel side and the series side of the unified power flow controller are obtained, the influence of parameters such as a series-parallel side converter and a transformer on the dynamic performance of the UPFC is considered, and the power transmission characteristic of the UPFC can be accurately and quickly simulated.
The technical scheme provided by the invention adds mode selection, so that the control mode is more diversified and the actual requirement is met.
The technical scheme provided by the invention considers the influence of overlarge active current and reactive current, and the current limiter with priority on active power is added, so that the condition that the current is overlarge due to short circuit in the operation of the UPFC can be simulated.
According to the technical scheme provided by the invention, in the control system of the series-parallel side converter, the mutually independent inner ring current controllers are obtained through decoupling, and the currents of the d axis and the q axis can be conveniently controlled.
Drawings
Fig. 1 is a flow chart of a simulation method of a unified power flow controller according to the present invention;
fig. 2 is a general structure diagram of a control logic simulation of the unified power flow controller provided by the present invention;
FIG. 3 is a diagram of the voltage control of the outer loop AC voltage on the parallel side according to the present invention;
FIG. 4 is a diagram of the parallel side outer loop reactive power control scheme provided by the present invention;
FIG. 5 is a diagram illustrating the DC voltage control of the outer ring on the parallel side according to the present invention;
FIG. 6 is a decoupled parallel side inner loop current control diagram provided by the present invention;
FIG. 7 is a diagram illustrating the series-side outer loop active power control scheme provided by the present invention;
FIG. 8 is a diagram illustrating the series side outer loop reactive power control scheme provided by the present invention;
FIG. 9 is a decoupled series side inner loop current control diagram provided by the present invention;
fig. 10 is a schematic diagram of the current output clipping provided by the present invention.
Detailed Description
For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples.
The invention provides a simulation method suitable for a UPFC control logic, and as shown in FIG. 1, the simulation method of a unified power flow controller comprises 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 series side converter model of the unified power flow controller;
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 is reasonable in structure, has good operability and adaptability, and can correctly simulate the dynamic characteristics of the UPFC under a normal working condition and a short-circuit working condition.
The UPFC control structure diagram includes: processing on the parallel side and processing on the series side.
Processing on the parallel side: data measured by the UPFC measuring system are processed to be input into parallel side outer ring alternating current voltage control, parallel side outer ring reactive power control and parallel side outer ring direct current voltage control, output of the parallel side outer ring alternating current voltage control and the parallel side outer ring reactive power control is used as input of parallel side mode selection, output values of the output values are processed through active power priority and output of the parallel side outer ring direct current voltage control to be used as input of parallel side inner ring current control together, then output of the inner ring current control is used as input of modulation depth and phase shift angle calculation, and parallel side control signals are obtained through modulation depth and phase shift angle calculation.
Treatment of the tandem side: data measured by the UPFC measuring system are processed to be used as input of active power control and reactive power control of an outer ring of the series side, output of the active power control and reactive power control of the outer ring of the series side is used as input of current control of an inner ring of the series side, output of the current control and a manual injection value of dq axis component of alternating voltage of the series side are used as input of mode selection, a numerical value after the mode selection is used as input of modulation depth and phase shift angle calculation, and a series side control signal is obtained through the modulation depth and the phase shift angle calculation.
(1) Obtaining steady-state operation parameters required by power flow calculation of electric power system
Establishing a UPFC measuring system, obtaining d-axis and q-axis components of voltage and current of a primary system serial side and a primary system parallel side, obtaining a parallel side reactive power actual value through calculation, converting data obtained by the measuring system into per unit values according to a selected power voltage reference value, and obtaining a series side active power actual value and a series side reactive power actual value; the dq axis transformation analytic expression of the UPFC measurement system is as follows:
wherein Va, Vb, Vc represent the three-phase line voltage or three-phase line current of the series/parallel side, respectively.
The active power and the reactive power can be obtained by calculating a voltage dq axis component and a current dq axis component, and the active power and the reactive power per unit value for control can be obtained by averaging and filtering, wherein the expression is as follows:
P＝Vd*Id+Vq*Iq <3>
Q＝Vq*Id-Vd*Iq <4>；
wherein: vd and Vq are voltage dq axis components, and Id and Iq are current dq axis components.
(2) Using the voltage, current d-axis and q-axis components, the parallel side reactive power per unit value and the direct current voltage per unit value obtained in the step (1) as the input of outer ring alternating current voltage control, outer ring reactive power control and outer ring direct current voltage control to obtain the d-axis and q-axis reference values of the parallel side alternating current; the outer ring alternating current voltage controller, the outer ring reactive power controller and the outer ring direct current voltage controller all adopt PI controllers with amplitude limiting, as shown in figures 3, 4 and 5;
(3) using the voltage and current dq axis components of the series side and the per unit values of the active power and the reactive power of the series side obtained in the step (1) as the input of outer loop active power control and outer loop reactive power control to obtain d-axis and q-axis reference values of alternating current of the series side; the outer loop active power controller and the outer loop reactive power controller both use PI controllers with amplitude limiting, as shown in fig. 7 and 8.
(4) Inputting the parallel side alternating current q-axis reference value obtained in the step (2) into mode selection, and obtaining the selected parallel side alternating current q-axis reference value according to a set mode;
the parallel side mode selection includes a UPFC power control mode and a parallel side STATCOM reactive power control mode.
Parallel side STATCOM reactive power control mode: stabilizing the AC voltage of the parallel side bus to stabilize the DC side voltage;
UPFC power control mode: and controlling the active power and the reactive power of the line.
(5) Inputting the series side alternating current dq axis reference value obtained in the step (3) into a series side inner ring current control module to obtain a parallel side alternating voltage dq axis reference value; fig. 9 is a block diagram of inner loop current control on the series side, in which a decoupling control method is adopted:
the d axis of the synchronous rotating coordinate system at the series side is oriented to the voltage vector of the alternating current power grid at the parallel side, and the expression of the inner ring current controller at the series side is obtained by the same method as follows:
Ucd＝Usd+(KP1(isdref-isd)+KI1∫(isdref-isd)dt)-ωLisq <5>
Ucq＝Usq+(KP2(isqref-isq)+KI2∫(isqref-isq)dt)+ωLisd <6>；
(6) inputting the series side alternating voltage dq axis reference value and the series side alternating voltage dq axis component manual injection value obtained in the step (5) into a mode selection module, and obtaining a selected series side alternating voltage dq axis reference value according to a set mode;
the tandem test mode selection includes: a UPFC power control mode and a series side manual voltage injection mode.
UPFC power control mode: controlling the active power and the reactive power of the line;
series side manual voltage injection mode: compared with the power control mode, the control effect is that a certain voltage is injected into the series side, so that the voltage at the tail end of the line can be increased to a specific value.
(7) Inputting the q-axis reference value of the parallel side alternating current obtained in the step (4) into a current limitIn the module, the output limits the current according to an active power priority principle to obtain a q-axis reference value of the parallel-side alternating current; fig. 10 is a schematic diagram of current limiting, wherein the active power priority principle is: to obtain IdAnd IqConsidering the total current
Cannot exceed clipping; priority assurance IdSize of (1), pair IqAnd (3) carrying out amplitude limiting, namely the q-axis reference value of the parallel side alternating current after amplitude limiting is as follows:
(8) inputting the d-axis reference value of the parallel side alternating current obtained in the step (2) and the q-axis reference value of the series side alternating current obtained in the step (7) into the parallel side inner loop current control, and outputting a dq-axis reference value of the parallel side alternating voltage; fig. 6 is a block diagram of inner loop current control on the parallel side, in which a decoupling control method is adopted:
and obtaining an inner ring current controller of the series-parallel side converter by adopting a decoupling control method under a dq axis coordinate system by combining the structural parameters of the UPFC series-parallel side converter and the transformer:
the mathematical expression of the parallel side inner loop current controller is as follows:
wherein,
ΔUd＝ωLisd；ΔUq＝ωLisq；Ucdand UcqD-axis and q-axis components of voltage fundamental waves at the alternating current side of the converter; u shapesd、UsqAre respectively the electric networkD, q-axis components of the voltage; i.e. isd、isqD-axis components and q-axis components of the power grid current respectively;
and
the method is realized by adopting a proportional integral link as follows:
in the inner loop current controller, there is a cross-coupling term ω LidAnd ω LiqI.e. Δ U in the formuladAnd Δ UqTerm, introduction of current state feedback quantity ω LidAnd ω LiqTo decouple; orienting the d-axis of the synchronous rotating coordinate system to the voltage vector of the parallel-side alternating-current power grid can obtain:
Usd＝Us <12>
Usq＝0 <13>
wherein, UsThe peak value of the phase voltage of the parallel side alternating current network.
The expression of the parallel side inner ring current controller obtained by combining the formulas is as follows:
Ucd＝Usd-(KP1(isdref-isd)+KI1∫(isdref-isd)dt)+ωLisq <14>
Ucq＝-(KP2(isqref-isq)+KI2∫(isqref-isq)dt)-ωLisd <15>
<8>；
the d axis and the q axis controlled by the inner ring form two completely independent control rings for respectively controlling the current of the d axis and the current of the q axis;
wherein: l is the equivalent inductance of the parallel side transformer plus phase reactor, omega represents the power frequency angular frequency, isdref、isqrefReference values, K, representing active and reactive currents, respectivelyP1、KP2、KI1、KI2Is a gain factor.
(9) Inputting the series side alternating voltage dq axis reference value obtained in the step (6) and the parallel side alternating voltage dq axis reference value obtained in the step (8) into a modulation depth and phase shift angle calculation module to obtain a control signal of a converter module;
(10) and (4) inputting the modulation depth and the phase shift angle obtained in the step (9) into a series-parallel side converter model to realize the voltage and current control of the inner ring and the outer ring.
The UPFC control logic simulation method has better operability and adaptability, can correctly simulate the dynamic characteristics of the UPFC under normal working conditions and short-circuit working conditions, and can be applied to the UPFC electromagnetic transient simulation.
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;
and the model construction module is used for constructing 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 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 construction 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.
The parallel side converter model construction 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.
The series side converter model building submodule further comprises: and a mode selection module is arranged between the inner ring current controller on the series side and the modulation depth and phase shift angle calculation module.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or 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, and the like) 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 application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.
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:
Ucd＝Usd-(KP1(isdref-isd)+KI1∫(isdref-isd)dt)+ωLisq
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapesd: is the d-axis component of the grid voltage; kP1: a gain factor; kI1: a gain factor; i.e. isdref: a reference value of active current; i.e. isd: 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. isq: is the q-axis component of the grid current;
Ucq＝-(KP2(isqref-isq)+KI2∫(isqref-isq)dt)-ωLisd
in the formula of Ucq: 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. isqref: a reference value of reactive current; kP2: a gain factor; kI2: 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:
Ucd＝Usd+(KP1(isdref-isd)+KI1∫(isdref-isd)dt)-ωLisq
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapesd: is the d-axis component of the grid voltage; kP1: a gain factor; kI1: a gain factor; i.e. isdref: a reference value representing an active current; i.e. isd: is the d-axis component of the grid current; ω: a phase angle; l: equivalent inductance of parallel side transformer plus phase reactor；isq: is the q-axis component of the grid current;
Ucq＝Usq+(KP2(isqref-isq)+KI2∫(isqref-isq)dt)+ωLisd
in the formula of Ucd: d-axis component of voltage fundamental wave at AC side of the converter; u shapecq: a q-axis component of a fundamental wave of the AC side voltage of the converter; u shapesq: is the q-axis component of the grid voltage; kP2: a gain factor; kI2: a gain factor; i.e. isqrefRepresenting 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.
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