CN115441750A - Mixed type AC-AC converter - Google Patents

Mixed type AC-AC converter Download PDF

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Publication number
CN115441750A
CN115441750A CN202211192385.7A CN202211192385A CN115441750A CN 115441750 A CN115441750 A CN 115441750A CN 202211192385 A CN202211192385 A CN 202211192385A CN 115441750 A CN115441750 A CN 115441750A
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China
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voltage
mmc
rectifier
control
axis
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CN202211192385.7A
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Chinese (zh)
Inventor
陈建福
唐捷
陈勇
裴星宇
吴宏远
李建标
杨锐雄
程旭
邹国惠
顾温国
廖鹏
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Guangdong Power Grid Co Ltd
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
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Guangdong Power Grid Co Ltd
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
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Priority to CN202211192385.7A priority Critical patent/CN115441750A/en
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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
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
    • 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
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The application discloses mixed type ac-ac converter includes: the rectifier comprises a rectifier side alternating current bus, a converter transformer, a rectifier, an inverter side alternating current bus, an alternating current filter and a direct current filter; the rectifier and the inverter consist of a high-voltage valve set LCC and a low-voltage valve set MMC; the LCC on the rectifying side adopts constant current control based on the direct current voltage of the MMC on the rectifying side, the MMC on the rectifying side adopts voltage amplitude-frequency control, the LCC on the inverting side adopts constant voltage control and constant turn-off angle control, and the MMC on the inverting side adopts constant direct current voltage control and constant reactive power control. The invention can realize the low-frequency sending of the pure new energy power generation base, well adapts to the power fluctuation of the new energy power generation base, fully utilizes the technical maturity of LCC and MMC, can reduce the construction cost and the power loss compared with the conventional AC-AC converter based on back-to-back MMC, and has great application value in the actual engineering.

Description

Mixed type AC-AC converter
Technical Field
The application relates to the technical field of converters, in particular to a hybrid AC-AC converter.
Background
The low-frequency alternating-current transmission technology can realize the transmission of a pure new energy power generation base, and the advantages are mainly shown in two aspects: (1) Compared with power frequency alternating current transmission, the power transmission frequency is reduced, and the distance of electric energy transmission can be enlarged; (2) Compared with direct-current power transmission, alternating-current power transmission does not have the problem of lack of a circuit breaker, and an alternating-current power grid can be conveniently formed between new energy power generation bases. Therefore, for the pure new energy power generation base, the low-frequency alternating current transmission technology is a competitive scheme.
The core device of the low-frequency alternating current transmission technology is an alternating current-alternating current converter. The existing documents mostly adopt a phase-control type AC/AC converter based on a thyristor, the device has simple structure and convenient control, but a large amount of reactive power needs to be consumed in the normal operation process, and low-order harmonic and inter-harmonic with considerable numerical values can be generated, thereby causing a series of electric energy quality problems. The harmonic characteristics of the device can be improved by adopting a fully-controlled device to replace a thyristor, but the effect is not obvious. In recent years, research has proposed an improved topology structure using a matrix converter as an ac converter, but the feasibility of the matrix converter in the field of high-voltage large-capacity power transmission is still to be verified. The other technical route is an alternating current converter based on a back-to-back Voltage Source Converter (VSC), the VSC is high in technical maturity, flexible in control mode and good in harmonic characteristics, but the defects of high device manufacturing cost and large power loss exist.
In addition, in order to realize large-scale pure new energy delivery, the problem of voltage support of a delivery-end alternating current system must be solved. The conventional method is to bundle and send out new energy, water and electricity, thermal power and the like, the proportion of the new energy has certain limitation, and the large-scale construction of matched thermal power deviates from the original intention of developing new energy. Theoretically, the new energy base can operate in a network-forming type control mode, but related engineering experience is less at present. Therefore, the existing and future new energy base of China still mainly adopts a network following type control mode in a short term, and the voltage support of a sending end alternating current system is provided by an alternating current-to-alternating current converter.
So far, few documents are made on the ac/ac converter suitable for the low-frequency transmission of the pure new energy power generation base, and in order to further improve the economy and reliability of the ac/ac converter, it is necessary to make research on the topology and the control strategy of the ac/ac converter suitable for the low-frequency transmission of the pure new energy power generation base.
Disclosure of Invention
The application provides a hybrid AC-AC converter which is used for solving the technical problems that an existing AC-AC converter cannot well adapt to power fluctuation of a new energy power generation base, engineering cost is high, and power loss is large.
In view of the above, a first aspect of the present application provides a hybrid ac/dc converter, including: a rectifier module composed of a positive rectifier and a negative rectifier, and an inverter module composed of a positive inverter and a negative inverter;
the high-voltage end of the positive pole rectifier is connected with the high-voltage end of the positive pole inverter, the high-voltage end of the negative pole rectifier is connected with the high-voltage end of the negative pole inverter, the low-voltage end of the positive pole rectifier and the low-voltage end of the negative pole rectifier are connected with each other and serve as a direct-current side neutral point of the rectifier module, the low-voltage end of the positive pole inverter and the low-voltage end of the negative pole inverter are connected with each other and serve as a direct-current side neutral point of the inverter module, and the direct-current side neutral points of the rectifier module and the inverter module are both connected to the ground electrode, so that a true bipolar structure is formed;
the alternating current side of the rectifier module is connected with one side of an alternating current bus of the rectifier side through a converter transformer, the direct current side of the rectifier module is connected with the direct current side of the inverter module, the alternating current side of the inverter module is connected with one side of an alternating current bus of the inverter side through the converter transformer, the other side of the alternating current bus of the rectifier side is connected with a pure new energy power generation base, and the other side of the alternating current bus of the inverter side is connected with a receiving-end power grid;
the rectification side alternating current bus and the inversion side alternating current bus are connected with alternating current filters, and the positive pole rectifier, the negative pole rectifier, the positive pole inverter and the negative pole inverter are connected with direct current filters.
Optionally, the positive rectifier, the negative rectifier, the positive inverter and the negative inverter are each: the high-pressure valve bank and the low-pressure valve bank are connected in series at a direct current side and connected in parallel at an alternating current side;
the high-voltage valve bank is a power grid commutation converter LCC, and the low-voltage valve bank is a modular multilevel converter MMC of a half-bridge submodule.
Optionally, the LCC comprises: two three-phase six-pulsation rectifier bridges, wherein the two three-phase six-pulsation rectifier bridges respectively adopt Y 0 Y and Y 0 A converter transformer in a delta connection mode is connected, and the phase difference between the valve sides of the two converter transformers is 30 degrees;
the MMC is a three-phase six-bridge-arm structure, and each bridge arm is cascaded by N half-bridge sub-modules and then connected with a bridge armIs resistant to series connection, MMC and Y are adopted 0 The converter transformers are connected in a/[ delta ] connection mode.
Optionally, the LCC on the rectifying side adopts a constant current control based on the MMC direct current voltage;
actual value U of direct-current voltage of MMC (modular multilevel converter) on rectifying side MMCrec After a first-order inertia link, the command value U of the direct current voltage of the MMC is compared with the command value U of the direct current voltage of the MMC MMCrecref Subtracting, and outputting DC current instruction value I under PI control dcref (ii) a The input of the constant current controller is I dcref And the actual value of the direct current I dc ，I dcref And I through a first-order inertia element dc Triggering an over-rake angle beta through PI control output after subtraction 1 Pi radian and beta 1 Subtracting to obtain a trigger lag angle alpha, and making the minimum trigger lag angle alpha min =5 °, take α and α min The middle maximum value being the trigger lag angle alpha R As a trigger signal for each switching device in the LCC.
Optionally, the MMC on the rectifying side adopts voltage amplitude-frequency control, and the control system comprises two control dimensions of a d axis and a q axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
phase voltage amplitude U of MMC alternating current outlet m Is a d-axis voltage command value u dref Let the q-axis voltage command value u qref =0, input of outer ring controller MMC AC outlet voltage d-axis component u d And q-axis component u q And u dref And u qref ，u dref And u qref Are respectively connected with u d And u q D-axis current reference value i is output through PI control after subtraction dref1 And q-axis current reference value i qref1 (ii) a The input of the inner ring controller is an MMC alternating outlet current d-axis component i d1 And q-axis component i q1 And i dref1 And i qref1 ，i dref1 And i qref1 Are respectively connected with i d1 And i q1 D-axis voltage modulation wave u is output through PI control after subtraction vdref1 And q-axis voltage modulation wave u vqref1 (ii) a The input of the trigger element is u vdref1 And u vqref1 And outputs each of the MMCs after dq/abc conversion and NLC modulationA trigger signal of the switching device.
Optionally, the LCC on the inverting side employs constant voltage control and constant turn-off angle control;
wherein, the input of the constant voltage control is an inversion side LCC direct current voltage instruction value U dcref Actual value U of LCC direct current voltage on sum inversion side dc ，U dc After a first-order inertia link, the signal is connected with U dcref Subtracting to obtain the DC voltage deviation U err ；
The input of the constant turn-off angle control is an inversion side LCC turn-off angle instruction value gamma ref And the actual value gamma of the LCC turn-off angle of the inversion side, let gamma ref ＝15°，γ ref Subtracting the minimum value of gamma in one period to obtain the turn-off angle deviation gamma err ；
Get U err And gamma err Triggering an over-rake angle beta through PI control output after the medium maximum value 2 Pi radians and beta 2 Subtracting to obtain the trigger lag angle alpha 2 And the trigger signal is used as a trigger signal of each switching device in the LCC on the inverting side.
Optionally, the MMC on the inversion side adopts constant direct-current voltage control and constant reactive power control, and the control system includes two control dimensions of d-axis and q-axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
MMC direct-current voltage instruction value U of order inversion side MMCinvref For the d-axis command value of the outer loop controller, the Q-axis command value Q of the outer loop controller is set sref ＝0；
Wherein, the input of the outer ring controller is an actual value U of the DC voltage of the MMC at the inversion side MMCinv MMC alternating current outlet reactive power Q of inversion side s And U MMCinvref And Q sref ，U MMCinv And Q s Are respectively connected with U MMCinvref And Q sref D-axis current reference value i is output through PI control after subtraction dref2 And q-axis current reference value i qref2 ；
The input of the inner ring controller is an inversion side MMC alternating outlet current d-axis component i d2 And q-axis component i q2 And i dref2 And i qref2 ，i dref2 And i qref2 Are respectively provided withAnd i d2 And i q2 D-axis voltage modulation wave u is output through PI control after subtraction vdref2 And q-axis voltage modulated wave u vqref2 (ii) a The input of the trigger element is u vdref2 And u vqref2 And the trigger signals of each switching device in the MMC at the inversion side are output through dq/abc conversion and NLC modulation.
Optionally, the net new energy power generation base comprises: wind power generation base and photovoltaic power generation base controlled by following net
According to the technical scheme, the method has the following advantages:
1. compared with the conventional AC-AC converter based on back-to-back VSC, the LCC-MMC hybrid AC-AC converter has the advantages that the construction cost and the power loss can be greatly reduced, and the LCC-MMC hybrid AC-AC converter has great application value in actual engineering.
2. The invention provides a control strategy of the LCC-MMC hybrid AC-AC converter, can realize the sending of a 100% pure new energy power generation base, well adapts to the power fluctuation of the new energy power generation base, fully utilizes the technical maturity of the LCC and the MMC, and plays a certain guiding role in future engineering design.
Drawings
Fig. 1 is a schematic diagram of a topology of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 2 is a schematic diagram of a topology of a three-phase six-pulse rectifier bridge in an LCC of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 3 is a schematic topology diagram of an MMC of a hybrid ac/ac converter provided in an embodiment of the present application;
fig. 4 is a schematic control structure diagram of a rectifying side LCC of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 5 is a schematic control structure diagram of a rectifying-side MMC of a hybrid ac/ac converter provided in an embodiment of the present application;
fig. 6 is a schematic control structure diagram of an inverter-side LCC of a hybrid ac/ac converter provided in an embodiment of the present application;
fig. 7 is a schematic control structure diagram of an inverter side MMC of a hybrid ac/ac converter provided in an embodiment of the present application;
fig. 8a is a schematic diagram illustrating an ac voltage simulation waveform of an ac bus on a rectifying side of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 8b is a schematic diagram illustrating an ac current simulation waveform of an ac bus on a rectifying side of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 8c is a schematic diagram of an active power simulation waveform of an ac bus on a rectifying side of a hybrid ac/dc converter provided in the embodiment of the present application;
fig. 9a is a schematic diagram of simulated waveforms of dc voltages of an LCC on a positive inversion side and an MMC on the positive inversion side of a hybrid ac/ac converter provided in an embodiment of the present application;
fig. 9b is a schematic diagram of a simulated waveform of the positive dc current of the hybrid ac/ac converter according to the embodiment of the present application;
fig. 10a is a schematic diagram illustrating an ac voltage simulation waveform of an ac bus on an inverter side of a hybrid ac/dc converter provided in an embodiment of the present application;
fig. 10b is a schematic diagram of an ac current simulation waveform of an inverter-side ac bus of a hybrid ac/ac converter according to an embodiment of the present application;
fig. 10c is a schematic diagram of an active power simulation waveform of an inverter-side ac bus of a hybrid ac/ac converter provided in this embodiment.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, a hybrid ac/dc converter provided in an embodiment of the present application includes: a rectifier module composed of a positive rectifier and a negative rectifier, and an inverter module composed of a positive inverter and a negative inverter;
the high-voltage end of the positive pole rectifier is connected with the high-voltage end of the positive pole inverter, the high-voltage end of the negative pole rectifier is connected with the high-voltage end of the negative pole inverter, the low-voltage end of the positive pole rectifier and the low-voltage end of the negative pole rectifier are connected with each other and serve as a direct-current side neutral point of the rectifier module, the low-voltage end of the positive pole inverter and the low-voltage end of the negative pole inverter are connected with each other and serve as a direct-current side neutral point of the inverter module, and the direct-current side neutral points of the rectifier module and the inverter module are connected to a ground electrode, so that a true bipolar structure is formed;
the alternating current side of the rectifier module is connected with one side of an alternating current bus of the rectifier side through a converter transformer, the direct current side of the rectifier module is connected with the direct current side of the inverter module, the alternating current side of the inverter module is connected with one side of the alternating current bus of the inversion side through the converter transformer, the other side of the alternating current bus of the rectifier side is connected with a pure new energy power generation base, and the other side of the alternating current bus of the inversion side is connected with a receiving end power grid; the rectification side alternating current bus and the inversion side alternating current bus are connected with alternating current filters, and the positive pole rectifier, the negative pole rectifier, the positive pole inverter and the negative pole inverter are connected with direct current filters.
It should be noted that the rated frequency of the pure new energy power generation base, the rectifier side converter transformer and the rectifier is 20Hz, and the pure new energy power generation base adopts a wind power generation base and a photovoltaic power generation base which are controlled by a grid-following type.
Further, the rectifier and the inverter in the embodiment are both composed of a high-voltage valve bank LCC and a low-voltage valve bank MMC, which are connected in series at the direct current side and in parallel at the alternating current side; the LCC comprises two three-phase six-pulse rectifier bridges which are respectively Y-shaped 0 Y and Y 0 A converter transformer in a delta connection mode is connected, and the phase difference of the valve sides of the two converter transformers is 30 degrees; MMC and Y adopted 0 A converter transformer connection in a delta connection mode; the structure of a three-phase six-pulse rectifier bridge in the LCC is shown in figure 2The structure of the MMC is shown in fig. 3.
In one embodiment, the rectifier LCC adopts constant current control based on the dc voltage of the rectifier MMC as shown in fig. 4, specifically:
actual value U of direct-current voltage of MMC at rectifying side MMCrec After a first-order inertia link, the command value U of the direct current voltage of the MMC is compared with the command value U of the direct current voltage of the MMC MMCrecref Subtracting, and outputting DC current instruction value I under PI control dcref (ii) a The input of the constant current controller is I dcref And the actual value of the direct current I dc ，I dcref And I through a first-order inertia element dc Triggering an over-rake angle beta through PI control output after subtraction 1 Pi radian and beta 1 Subtracting to obtain a trigger lag angle alpha, and making the minimum trigger lag angle alpha min =5 °, take α and α min The maximum value being the trigger lag angle alpha R As a trigger signal for each switching device in the LCC.
As shown in fig. 5, the flow side MMC adopts voltage amplitude-frequency control, specifically:
the control system comprises two control dimensions of d axis and q axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
phase voltage amplitude U of MMC alternating current outlet m Is a d-axis voltage command value u dref Let the q-axis voltage command value u qref =0, input of outer ring controller MMC AC outlet voltage d-axis component u d And q-axis component u q And u dref And u qref ，u dref And u qref Are respectively connected with u d And u q D-axis current reference value i is output through PI control after subtraction dref1 And q-axis current reference value i qref1 (ii) a The input of the inner ring controller is MMC alternating outlet current d-axis component i d1 And q-axis component i q1 And i dref1 And i qref1 ，i dref1 And i qref1 Are respectively connected with i d1 And i q1 D-axis voltage modulation wave u is output through PI control after subtraction vdref1 And q-axis voltage modulation wave u vqref1 (ii) a The input of the trigger element is u vdref1 And u vqref1 And outputs MMC after dq/abc conversion and NLC modulationThe trigger signal of each switching device.
As shown in fig. 6, the inverter-side LCC adopts constant-voltage control and constant-turn-off angle control, specifically:
the input of the constant voltage control is an inversion side LCC direct current voltage instruction value U dcref Actual value U of LCC direct current voltage on sum inversion side dc ，U dc After a first-order inertia link, the signal is connected with U dcref Subtracting to obtain the DC voltage deviation U err ；
The input of the constant turn-off angle control is an inversion side LCC turn-off angle instruction value gamma ref And the actual value gamma of the LCC turn-off angle of the inversion side, let gamma ref ＝15°，γ ref Subtracting the minimum value of gamma in one period to obtain the off-angle deviation gamma err ；
Get U err And gamma err Triggering an advance angle beta after the intermediate maximum value through PI control output 2 Pi radian and beta 2 Subtracting to obtain the trigger lag angle alpha 2 And the trigger signals are used as trigger signals of all the switching devices in the LCC on the inversion side.
The inverter side MMC adopts constant direct current voltage control and constant reactive power control as shown in fig. 7, and is specific:
the control system comprises two control dimensions of d axis and q axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
MMC direct-current voltage instruction value U of order inversion side MMCinvref For the d-axis command value of the outer loop controller, the Q-axis command value Q of the outer loop controller is set sref ＝0；
Wherein, the input of the outer ring controller is an inversion side MMC direct current voltage actual value U MMCinv MMC alternating current outlet reactive power Q of inversion side s And U MMCinvref And Q sref ，U MMCinv And Q s Are respectively connected with U MMCinvref And Q sref D-axis current reference value i is output through PI control after subtraction dref2 And q-axis current reference value i qref2 ；
The input of the inner ring controller is an inversion side MMC alternating outlet current d-axis component i d2 And q-axis component i q2 And i dref2 And i qref2 ，i dref2 And i qref2 Are respectively connected with i d2 And i q2 D-axis voltage modulation wave u is output through PI control after subtraction vdref2 And q-axis voltage modulated wave u vqref2 (ii) a The input of the trigger is u vdref2 And u vqref2 And after dq/abc conversion and NLC modulation, trigger signals of all switching devices in the MMC on the inversion side are output.
The system parameters in this embodiment are shown in table 1:
TABLE 1
Figure BDA0003869990090000081
Figure BDA0003869990090000091
And a corresponding simulation platform is built in the electromagnetic transient simulation software PSCAD/EMTDC to simulate the power fluctuation of the new energy power generation base. In the simulation, the step reduction of the output active power of the 3s new energy power generation base from 5000MW to 3000MW is assumed, fig. 8 (a) -8 (c) show the simulation results of the key electrical quantity of the alternating current bus at the rectification side, fig. 9 (a) -9 (b) show the simulation results of the direct current voltage and the direct current, fig. 10 (a) -10 (c) show the simulation results of the key electrical quantity of the alternating current bus at the inversion side, and the simulation results prove the effectiveness of the invention.
The terms "first," "second," "third," "fourth," and the like in the description and in the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (8)

1. A hybrid ac/dc converter, comprising: a rectifier module composed of a positive rectifier and a negative rectifier, and an inverter module composed of a positive inverter and a negative inverter;
the high-voltage end of the positive pole rectifier is connected with the high-voltage end of the positive pole inverter, the high-voltage end of the negative pole rectifier is connected with the high-voltage end of the negative pole inverter, the low-voltage end of the positive pole rectifier and the low-voltage end of the negative pole rectifier are connected with each other and serve as a direct-current side neutral point of the rectifier module, the low-voltage end of the positive pole inverter and the low-voltage end of the negative pole inverter are connected with each other and serve as a direct-current side neutral point of the inverter module, and the direct-current side neutral points of the rectifier module and the inverter module are both connected to the ground electrode, so that a true bipolar structure is formed;
the alternating current side of the rectifier module is connected with one side of an alternating current bus of the rectifier side through a converter transformer, the direct current side of the rectifier module is connected with the direct current side of the inverter module, the alternating current side of the inverter module is connected with one side of an alternating current bus of the inverter side through the converter transformer, the other side of the alternating current bus of the rectifier side is connected with a pure new energy power generation base, and the other side of the alternating current bus of the inverter side is connected with a receiving-end power grid;
the rectification side alternating current bus and the inversion side alternating current bus are connected with alternating current filters, and the positive pole rectifier, the negative pole rectifier, the positive pole inverter and the negative pole inverter are connected with direct current filters.
2. The hybrid ac/ac converter of claim 1, wherein the positive rectifier, the negative rectifier, the positive inverter, and the negative inverter are each: the high-pressure valve bank and the low-pressure valve bank are connected in series at a direct current side and connected in parallel at an alternating current side;
the high-voltage valve bank is a power grid commutation converter LCC, and the low-voltage valve bank is a modular multilevel converter MMC of a half-bridge submodule.
3. The hybrid ac/ac converter of claim 2, wherein the LCC comprises: two three-phase six-pulse rectifier bridges, wherein the two three-phase six-pulse rectifier bridges respectively adopt Y 0 Y and Y 0 a/Delta-mode converter transformer connected and two convertersThe valve side of the transformer is out of phase by 30 degrees;
the MMC is a three-phase six-bridge-arm structure, each bridge arm is formed by cascading N half-bridge submodules and then connecting the N half-bridge submodules in series with a bridge arm reactance, and the MMC and the Y are adopted 0 And/delta connection mode converter transformers.
4. The hybrid ac/ac converter according to claim 2, wherein the LCC at the rectifying side employs constant current control based on MMC dc voltage;
actual value U of direct-current voltage of MMC at rectifying side MMCrec After a first-order inertia link, the command value U of the direct current voltage is compared with the instruction value U of the MMC MMCrecref Subtracting, and outputting DC command value I under PI control dcref (ii) a The input of the constant current controller is I dcref And the actual value of the direct current I dc ，I dcref And I through a first-order inertia element dc Triggering an over-rake angle beta through PI control output after subtraction 1 Pi radian and beta 1 Subtracting to obtain a trigger lag angle alpha, and making the minimum trigger lag angle alpha min =5 °, take α and α min The middle maximum value being the trigger lag angle alpha R As a trigger signal for each switching device in the LCC.
5. The hybrid ac-ac converter according to claim 2, wherein the MMC on the rectifying side employs voltage amplitude-frequency control, and the control system comprises two control dimensions of d-axis and q-axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
phase voltage amplitude U of MMC alternating current outlet m Is a d-axis voltage command value u dref Let the q-axis voltage command value u qref =0, the input of the outer ring controller is MMC alternating current outlet voltage d-axis component u d And q-axis component u q And u dref And u qref ，u dref And u qref Are respectively connected with u d And u q D-axis current reference value i is output through PI control after subtraction dref1 And q-axis current reference value i qref1 (ii) a The input of the inner ring controller is MMC alternating outlet current d-axis component i d1 And q-axis component i q1 And i dref1 And i qref1 ，i dref1 And i qref1 Are respectively connected with i d1 And i q1 D-axis voltage modulation wave u is output through PI control after subtraction vdref1 And q-axis voltage modulated wave u vqref1 (ii) a The input of the trigger element is u vdref1 And u vqref1 And the trigger signals of each switching device in the MMC are output after dq/abc conversion and NLC modulation.
6. The hybrid ac/ac converter according to claim 2, wherein the LCC of the inverting side employs constant voltage control and constant turn-off angle control;
wherein, the input of the constant voltage control is an inversion side LCC direct current voltage instruction value U dcref Actual value U of LCC direct current voltage on sum inversion side dc ，U dc After a first-order inertia link, the signal is connected with U dcref Subtracting to obtain the DC voltage deviation U err ；
The input of the constant turn-off angle control is an inversion side LCC turn-off angle instruction value gamma ref And the actual value gamma of the LCC turn-off angle of the inversion side, let gamma ref ＝15°，γ ref Subtracting the minimum value of gamma in one period to obtain the off-angle deviation gamma err ；
Get U err And gamma err Triggering an over-rake angle beta through PI control output after the medium maximum value 2 Pi radian and beta 2 Subtracting to obtain the trigger lag angle alpha 2 And the trigger signal is used as a trigger signal of each switching device in the LCC on the inverting side.
7. The hybrid AC-AC converter according to claim 2, wherein the MMC on the inverting side adopts constant DC voltage control and constant reactive power control, and the control system comprises two control dimensions of d-axis and q-axis: the system comprises an outer ring controller, an inner ring controller and a triggering link;
MMC direct-current voltage instruction value U of order inversion side MMCinvref For the d-axis command value of the outer loop controller, the Q-axis command value Q of the outer loop controller is set sref ＝0；
Wherein, the outer ring controlThe input of the controller is an actual DC voltage value U of the MMC at the inversion side MMCinv MMC alternating current outlet reactive power Q of sum inversion side s And U MMCinvref And Q sref ，U MMCinv And Q s Are respectively connected with U MMCinvref And Q sref D-axis current reference value i is output through PI control after subtraction dref2 And q-axis current reference value i qref2 ；
The input of the inner ring controller is an inversion side MMC alternating outlet current d-axis component i d2 And q-axis component i q2 And i dref2 And i qref2 ，i dref2 And i qref2 Are respectively connected with i d2 And i q2 D-axis voltage modulation wave u is output through PI control after subtraction vdref2 And q-axis voltage modulation wave u vqref2 (ii) a The input of the trigger element is u vdref2 And u vqref2 And the trigger signals of each switching device in the MMC at the inversion side are output through dq/abc conversion and NLC modulation.
8. The hybrid ac/ac converter of claim 1, wherein the net energy power generation base comprises: and a wind power generation base and a photovoltaic power generation base which are controlled by a network following type are adopted.
CN202211192385.7A 2022-09-28 2022-09-28 Mixed type AC-AC converter Pending CN115441750A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117559518A (en) * 2023-10-16 2024-02-13 国家电网有限公司华东分部 Equivalent model construction method and device for wind power generation system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117559518A (en) * 2023-10-16 2024-02-13 国家电网有限公司华东分部 Equivalent model construction method and device for wind power generation system

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