CN113783447A - SVPWM modulation-based SNOP double closed-loop control system and method - Google Patents
SVPWM modulation-based SNOP double closed-loop control system and method Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Abstract
The invention relates to an SNOP (single-input-single-output) double-closed-loop control system and method based on SVPWM (space vector pulse width modulation), wherein the SNOP comprises a converter VSC1 and a VSC2, the double-closed-loop control system comprises a VSC1 double-closed-loop control part, a VSC2 double-closed-loop control part and an SVPWM modulation part, and the SVPWM modulation part comprises: the coordinate conversion unit is used for carrying out coordinate conversion on the output quantities of the VSC1 double closed-loop control part and the VSC2 double closed-loop control part to obtain a reference voltage vector after coordinate conversion; the sector selection unit determines a sector according to the reference voltage vector after the coordinate transformation and determines the action time of each space vector; and the signal generating unit generates a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2. Compared with the prior art, the invention has the advantages of improving the economy of SNOP, controlling the stability and the like.
Description
Technical Field
The invention relates to an SNOP control modulation system, in particular to an SNOP double closed-loop control system and method based on SVPWM modulation.
Background
The intelligent Soft-Open Point (SNOP) generally adopts the traditional carrier PWM modulation technology at present, obtains a switch pulse width control signal by comparing a carrier with a modulated wave, has the advantages of high precision, fast response, high precision and the like, and is widely applied in recent years. When applied to SNOP, the input signal of the PWM modulation system, i.e. the modulation ratio, is greatly affected by the reactive component of the system voltage, and the situation that the reactive component of the system voltage is positive and negative occurs due to the existence of the capacitance and the reactive element in the system, which causes instability of the control system based on the PWM modulation technology.
In the control system of the converter, the traditional control method also comprises a direct current control method based on hysteresis loop. However, the conventional hysteresis-based direct current control method has the defect of unstable switching frequency, and the direct current control method is difficult to be applied to SNOP to achieve the purpose of simultaneously controlling a plurality of electrical variables.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide an SNOP double closed-loop control system and method based on SVPWM (space vector pulse width modulation), so that the adjustment of the SNOP is more accurate, quicker and more stable, and the electric energy quality of a feeder line of a power distribution network can be more effectively improved.
The purpose of the invention can be realized by the following technical scheme:
an SNOP (single-loop-locked loop) double-closed-loop control system based on SVPWM (space vector pulse width modulation), wherein the SNOP comprises converters VSC1 and VSC2, the double-closed-loop control system comprises a VSC1 double-closed-loop control part, a VSC2 double-closed-loop control part and an SVPWM (space vector pulse width modulation) part, and the SVPWM part comprises:
the coordinate conversion unit is used for carrying out coordinate conversion on the output quantities of the VSC1 double closed-loop control part and the VSC2 double closed-loop control part to obtain a reference voltage vector after coordinate conversion;
the sector selection unit determines a sector according to the reference voltage vector after the coordinate transformation and determines the action time of each space vector;
and the signal generating unit generates a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2.
Further, the VSC1 double-closed-loop control part comprises an inner loop current PI controller and an outer loop voltage power controller, and the outer loop voltage power controller is designed according to the relation among direct current side voltage, reactive power on the VSC1 side and current on the VSC1 side, so that outer loop direct current side voltage control and outer loop reactive power control are achieved.
Further, the VSC2 double-closed-loop control part comprises an inner loop current PI controller and an outer loop power controller, and the outer loop power controller is designed according to the relation among the active power flowing through the SNOP, the reactive power of the VSC2 side and the current of the VSC2 side, so that the outer loop active power control and the outer loop reactive power control are realized.
Further, the coordinate transformation specifically includes: converting the output quantity, namely d and q axis components of the reference voltage, into a quantity V under a three-phase static abc coordinate system through dq/abc transformationaref、Vbref、VcrefAnd then converted into a quantity V under a two-phase stationary reference frame (alpha, beta)α、Vβ。
Further, the action time of the space vector is determined according to the sine theorem and the optimal switch switching sequence.
The invention also provides an SNOP double closed-loop control method based on SVPWM modulation, wherein the SNOP comprises converters VSC1 and VSC2, and the control method comprises the following steps:
performing double closed-loop control on the VSC1 and the VSC2 respectively to obtain output quantities;
obtaining switching signals of each bridge arm IGBT of the converters VSC1 and VSC2 by adopting an SVPWM (space vector pulse width modulation) technology based on the output quantity, and specifically:
carrying out coordinate conversion on output quantities of the VSC1 double-closed-loop control part and the VSC2 double-closed-loop control part to obtain a reference voltage vector after coordinate conversion;
determining a sector according to the reference voltage vector after coordinate transformation, and determining the action time of each space vector;
and generating a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2.
Further, when the VSC1 is subjected to double closed-loop control, on the basis of inner-loop current PI control, outer-loop voltage power control is designed according to the relation among direct-current side voltage, reactive power of the VSC1 side and current of the VSC1 side, and outer-loop direct-current side voltage control and outer-loop reactive power control are achieved.
Further, when the double closed-loop control is performed on the VSC2, on the basis of the inner-loop current PI control, the outer-loop power control is designed according to the relationship between the active power flowing through the SNOP, the reactive power on the VSC2 side, and the current on the VSC2 side, so that the outer-loop active power control and the outer-loop reactive power control are realized.
Further, the coordinate transformation specifically includes: converting the output quantity, namely d and q axis components of the reference voltage, into a quantity V under a three-phase static abc coordinate system through dq/abc transformationaref、Vbref、VcrefAnd then converted into a quantity V under a two-phase stationary reference frame (alpha, beta)α、Vβ。
Further, the action time of the space vector is determined according to the sine theorem and the optimal switch switching sequence.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention finds out the root of the problem of poor stability of the control of the traditional carrier PWM modulation technology when applied to the SNOP, designs an SVPWM modulation system suitable for the SNOP, overcomes the defect of the control stability of the traditional modulation technology through the coordinate system transformation of the electric quantity, avoids the fluctuation problem in the control and ensures that the whole SNOP control system has better stability and accuracy. And finally, the target effects of accuracy, rapidity and stability of control are achieved by matching the double closed-loop control system and the SVPWM modulation system.
2. In the design of a control system, aiming at the characteristic that the converters on two sides of the SNOP can control two electric quantities respectively, a double closed-loop control system is designed, a current inner loop PI controller is designed by introducing PI control, on the basis, a direct-current voltage outer loop PI controller is designed, and a power outer loop controller is designed by utilizing electrical connection obtained by formula derivation, so that the power outer loop controller is suitable for the operation of the SNOP, and the rapidity and the accuracy of the control are realized.
3. One reason why the SNOP cannot be applied to the power grid in a large scale at present is the cost problem, but the invention utilizes the characteristic of high utilization rate of the SVPWM technology to the direct current side voltage, can improve the utilization rate of the SNOP direct current side voltage, namely, can reduce the cost of the direct current side capacitor under the condition of the same external conditions, and has certain improvement in the aspect of economy.
4. The invention designs double closed-loop control and SVPWM modulation which are suitable for SNOP and can be connected with each other through coordinate system transformation, and realizes optimization of SNOP control on a generalized level.
Drawings
FIG. 1 is an SNOP structure topology;
FIG. 2 is a schematic structural diagram of a control part of the VSC 1;
FIG. 3 is a schematic structural diagram of a control part of the VSC 2;
FIG. 4 is a flow chart of SVPWM modulation implementation;
FIG. 5 is a schematic diagram of a Simulink simulation model of SVPWM modulation;
FIG. 6 is a voltage waveform on the direct current side of SNOP modulated by conventional carrier PWM;
fig. 7 is a waveform of the SNOP dc side voltage modulated using SVPWM.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
The structural topology of SNOP is shown in fig. 1, and it functions to realize the transmission of active power between feeders and respectively provide reactive power to feeders on both sides, because SNOP works based on fully-controlled power electronic devices, so it has flexibility and continuity in controlling both active and reactive power. Under the condition that the SNOP is in steady-state operation, power loss in the SNOP is ignored, active power flowing into one end of the SNOP is equal to active power flowing out of the other end of the SNOP, and the purpose of controlling the active power on two feeders connected with the SNOP can be achieved only by adopting the VSC at one end of the SNOP to control the size and the direction of the active power; and the VSCs at the two ends can each provide reactive power to the two-end feeders and are not constrained to each other. The converters VSC1 and VSC2 can each control two state quantities, and therefore, the dc side capacitor voltage can be controlled by VSC1, the magnitude and direction of active power can be controlled by VSC2, and the two VSCs each control the magnitude of the reactive power provided to the feeders on both sides.
According to the working principle of the SNOP, the invention designs a double closed-loop control system suitable for the SNOP, wherein the converters of the SNOP comprise a VSC1 and a VSC2, and the two converters have different functions and corresponding double closed-loop control structures, but both comprise an inner-loop current PI controller and an outer-loop voltage/power controller.
Under normal operating condition, converter VSC 1's function is for maintaining SNOP direct current side capacitor voltage's stability and for VSC1 side feeder provide reactive power, consequently, under the prerequisite that adopts inner loop current PI control, according to the direct current side voltage respectively, the relation between VSC1 side reactive power and the VSC1 side electric current, outer loop direct current side voltage control and outer loop reactive power control have been designed, double closed-loop control based on the negative feedback has been realized.
Converter VSC 2's function provides reactive power for the size and the direction of control active power and for VSC2 side feeder, consequently, under the prerequisite that adopts inner loop current PI control, according to the active power of flowing through SNOP, the relation between VSC2 side reactive power and the VSC2 side electric current respectively, outer loop active power control and outer loop reactive power control have been designed, realize the double-closed-loop control based on the negative feedback.
The structure of the VSC1 and the structure of the VSC2 double closed-loop control part are respectively shown in the figures 2 and 3. V in FIGS. 2 and 3sd1、Vsq1、Vsd2、Vsq2D-axis components and q-axis components of voltages of the alternating current systems 1 and 2 connected to two ends of the SNOP, respectively; vd1、Vq1、Vd2、Vq2The converter comprises d-axis components and q-axis components of alternating voltage at the sides of a converter VSC1 and a converter VSC2 on both sides of an SNOP; the subscript bears a reference value for ref referring to the electrical quantity.
Taking a VSC1 side current inner loop PI controller as an example, the PI parameters are adjusted to satisfy:
in the formula id1、iq1、id1ref、iq1refThe d-axis component and the q-axis component of the alternating current on the VSC1 side of the converter and the reference value of the alternating current are respectively.
The negative feedback control current and the direct current voltage of the current and the voltage can keep stable values, and the double closed loop PI control of the voltage outer loop and the current inner loop is realized; on the basis of the PI control of the inner loop current, an outer loop controller of active power and reactive power is designed according to the electrical connection between the active power and the reactive power and the current. The double-closed-loop control enables the inner loop current to be in a controllable state all the time, achieves the purpose of controlling the outer loop electric quantity such as direct current side voltage, active power and reactive power, enables the SNOP to achieve stable direct current side voltage, can accurately control transmitted active power and provided reactive power, and overcomes the defect that the switching frequency of a traditional direct current control method based on hysteresis loop is unstable.
In addition, the control system has the advantages of proportional regulation and integral regulation due to the introduction of the PI controller, and has rapidity and capability of eliminating static errors by reasonably regulating PI parameters.
The double-closed-loop control part adopts a double-closed-loop control system of direct-current side voltage, reactive power, an active power outer loop and a current inner loop to enable the inner loop current to be in a controllable state all the time, and meanwhile, the purpose of controlling the outer loop electric quantity such as the direct-current side voltage, the active power and the reactive power is achieved, the SNOP can achieve the purposes of stabilizing the direct-current side voltage and accurately controlling the transmitted active power and the provided reactive power, and the defect that the switching frequency is unstable in the traditional direct current control method based on hysteresis loop is overcome.
D-and q-axis components V of reference voltages on VSC1 and VSC2 sides output by a VSC1 and VSC2 double-closed-loop control part according to SNOPd1ref、Vq1ref、Vd2ref、Vq2refThe corresponding modulated parts are constructed. Different from the traditional carrier PWM, Space Vector Pulse Width Modulation (SVPWM) technology is adopted here, and the output quantity of the double closed-loop control system of the VSC1 and the VSC2, namely the reference voltage is usedd. The q-axis component is converted into a quantity V under a three-phase static abc coordinate system through dq/abc conversionaref、Vbref、VcrefAnd then converted into a quantity V under a two-phase stationary reference frame (alpha, beta)α、Vβ. In the signal transmission part of control and modulation, the connection of control and modulation is realized through the two coordinate transformations.
Under the premise of the conversion, the space vector of the reference voltage can enter a sector selection module of the SVPWM, and can be represented according to two adjacent voltage space vectors of the sector where the space vector of the reference voltage is located. Because the pulse width modulation wave needs to be generated finally, the action time of each space vector can be determined according to the sine theorem and the optimal switching sequence, and the switching signals of the IGBT of each bridge arm are generated finally. The specific implementation steps of SVPWM are shown in fig. 4.
In addition, a simulation model is built in Matlab/Simulink, and the application of SVPWM modulation technology is verified through simulation, so that the stability of the SNOP control electric quantity is greatly improved, and the method has practicability. An SVPWM modulation simulation model suitable for SNOP control is built in Matlab/Simulink and is shown in FIG. 5.
The SVPWM technology is different from the traditional carrier PWM technology, although the calculated amount is increased, the increased third harmonic wave is offset in a symmetrical three-phase system, the harmonic wave content of the current in the power system where the SNOP is located is finally smaller, the utilization rate of the voltage on the direct current side is improved, namely the requirement on the voltage on the direct current side is reduced on the premise that the voltages on two ends of the SNOP are the same, and the cost is saved. Further, considering that the frequency of an actual power system is 50Hz, in this case, SVPWM modulation is more suitable for the power system than conventional PWM modulation.
The traditional carrier PWM modulation has high requirement on the modulation ratio, the q-axis component of the system voltage in an actual power system is influenced by a capacitor and a reactance element and fluctuates around a value of 0, and the modulation ratio of the carrier PWM modulation system applied to the SNOP is obtained by changing the ratio of the d-axis component and the q-axis component of the voltage to the direct-current side voltage through a coordinate system, so that the traditional PWM modulation system has certain error when applied to the control system of the SNOP. The input quantity of the SVPWM modulation system is a component of the system voltage under an (alpha, beta) two-phase static coordinate system, so that the SVPWM modulation system does not have the problems and is relatively stable in control system. The direct-current side voltage waveforms of the SNOP adopting the conventional carrier PWM modulation system and the SNOP adopting the SVPWM modulation system are respectively shown in fig. 6 and fig. 7, and it can be seen that the control performance of the SNOP adopting the SVPWM modulation system is better.
The initial values of the SNOP dc-side voltage corresponding to fig. 6 and 7 are both 550V, the straight line in the figure is the target value 700V of the SNOP-controlled dc-side voltage, 50V is represented by one grid in the ordinate of fig. 6, and 20V is represented by one grid in the ordinate of fig. 7. Therefore, under the condition that the overshoot is almost equal, the SNOP control system adopting SVPWM modulation is better in rapidity, can eliminate static errors, and is greatly improved in control stability compared with the result of fluctuation of the traditional carrier PWM control means.
In another embodiment, an SNOP dual closed loop control method based on SVPWM modulation is provided, where the SNOP includes converters VSC1 and VSC2, and the control method includes the following steps: performing double closed-loop control on the VSC1 and the VSC2 respectively to obtain output quantities; and obtaining switching signals of each bridge arm IGBT of the converters VSC1 and VSC2 by adopting an SVPWM (space vector pulse width modulation) technology based on the output quantity. The specific acquisition process of the switching signal comprises the following steps: carrying out coordinate conversion on output quantities of the VSC1 double-closed-loop control part and the VSC2 double-closed-loop control part to obtain a reference voltage vector after coordinate conversion; determining a sector according to the reference voltage vector after coordinate transformation, and determining the action time of each space vector; and generating a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (10)
1. An SNOP (single-loop-locked loop) double-closed-loop control system based on SVPWM (space vector pulse width modulation), wherein the SNOP comprises converters VSC1 and VSC2, and is characterized in that the double-closed-loop control system comprises a VSC1 double-closed-loop control part, a VSC2 double-closed-loop control part and an SVPWM modulation part, and the SVPWM modulation part comprises:
the coordinate conversion unit is used for carrying out coordinate conversion on the output quantities of the VSC1 double closed-loop control part and the VSC2 double closed-loop control part to obtain a reference voltage vector after coordinate conversion;
the sector selection unit determines a sector according to the reference voltage vector after the coordinate transformation and determines the action time of each space vector;
and the signal generating unit generates a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2.
2. The SVPWM modulation-based SNOP double closed-loop control system according to claim 1, characterized in that the VSC1 double closed-loop control part comprises an inner loop current PI controller and an outer loop voltage power controller, the outer loop voltage power controller is designed according to the relation between the DC side voltage, the reactive power of VSC1 side and the current of VSC1 side, and realizes the outer loop DC side voltage control and the outer loop reactive power control.
3. The SVPWM modulation-based SNOP double closed-loop control system according to claim 1, characterized in that the VSC2 double closed-loop control part comprises an inner loop current PI controller and an outer loop power controller, the outer loop power controller is designed according to the relation between the active power flowing through SNOP, reactive power on VSC2 side and current on VSC2 side, and realizes outer loop active power control and outer loop reactive power control.
4. The SVPWM modulation-based SNOP dual closed-loop control system according to claim 1, wherein the coordinate transformation specifically is: converting the output quantity, namely d and q axis components of the reference voltage, into a quantity V under a three-phase static abc coordinate system through dq/abc transformationaref、Vbref、VcrefThen convert it into twoQuantity V in a stationary reference frame (α, β)α、Vβ。
5. An SNOP double closed loop control system based on SVPWM modulation according to claim 1, wherein the action time of the space vector is determined according to sine theorem and optimal switching sequence.
6. An SNOP double closed loop control method based on SVPWM modulation, the SNOP comprises converters VSC1 and VSC2, characterized in that the control method comprises the following steps:
performing double closed-loop control on the VSC1 and the VSC2 respectively to obtain output quantities;
obtaining switching signals of each bridge arm IGBT of the converters VSC1 and VSC2 by adopting an SVPWM (space vector pulse width modulation) technology based on the output quantity, and specifically:
carrying out coordinate conversion on output quantities of the VSC1 double-closed-loop control part and the VSC2 double-closed-loop control part to obtain a reference voltage vector after coordinate conversion;
determining a sector according to the reference voltage vector after coordinate transformation, and determining the action time of each space vector;
and generating a modulation wave of a space vector to control the switching state of each arm IGBT of the converters VSC1 and VSC 2.
7. An SNOP (single-phase double-closed-loop control) method based on SVPWM (space vector pulse width modulation) according to claim 6, wherein when performing double-closed-loop control on the VSC1, based on the PI (proportional integral) control of the inner-loop current, the outer-loop voltage power control is designed according to the relation among the voltage on the DC side, the reactive power on the VSC1 side and the current on the VSC1 side, so as to realize the outer-loop DC side voltage control and the outer-loop reactive power control.
8. The SVPWM modulation-based SNOP double closed-loop control method of claim 6, wherein when performing double closed-loop control on the VSC2, based on the PI control of the inner-loop current, the outer-loop power control is designed according to the relation among the active power flowing through the SNOP, the reactive power of VSC2 side and the current of VSC2 side, so as to realize the outer-loop active power control and the outer-loop reactive power control.
9. The SNOP double closed-loop control method based on SVPWM (space vector pulse width modulation) according to claim 6, wherein the coordinate transformation specifically is: converting the output quantity, namely d and q axis components of the reference voltage, into a quantity V under a three-phase static abc coordinate system through dq/abc transformationaref、Vbref、VcrefAnd then converted into a quantity V under a two-phase stationary reference frame (alpha, beta)α、Vβ。
10. The SVPWM-based SNOP dual closed-loop control method of claim 6, wherein the action time of the space vector is determined according to sine theorem and optimal switching sequence.
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