CN112531764A - Alternating current excitation system and PWM control method of grid-side converter thereof - Google Patents
Alternating current excitation system and PWM control method of grid-side converter thereof Download PDFInfo
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- CN112531764A CN112531764A CN201910883443.2A CN201910883443A CN112531764A CN 112531764 A CN112531764 A CN 112531764A CN 201910883443 A CN201910883443 A CN 201910883443A CN 112531764 A CN112531764 A CN 112531764A
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- 230000005284 excitation Effects 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000002955 isolation Methods 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000005540 biological transmission Effects 0.000 abstract description 2
- 230000010363 phase shift Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000033228 biological regulation Effects 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241001672018 Cercomela melanura Species 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention relates to the field of power electronics and power transmission control, in particular to a PWM (pulse-width modulation) control method of an alternating current excitation system and a grid-side converter thereof. Because the excitation transformer on the network side does not shift the phase, after the triangular carrier wave is compared with the modulation wave, the driving pulse of each network side module only misplaces the phase-shifting angle of the triangular carrier wave, so that the output harmonic waves are phase-shifted and superposed, and the harmonic amplitude of the total current after parallel connection is reduced; the non-phase-shifting isolation transformer is used, the non-phase-shifting design reduces the design and production cost of the transformer, the precision requirement is reduced, and the isolated design blocks a path of parallel circulating current, so that the circulating current problem is avoided.
Description
Technical Field
The invention relates to the field of power electronics and power transmission control, in particular to an alternating current excitation system and a PWM control method of a grid-side converter of the alternating current excitation system.
Background
In recent years, the grid-connected capacity of a new energy grid-connected generator set is continuously increased, higher requirements are provided for the peak load regulation and frequency regulation capacity of a power grid due to the randomness of wind power and photovoltaic power generation, and the new energy grid-connected generator set is used as a pumped storage power station of a best tool for peak load shifting and valley filling. The pumped storage power station is used as a comprehensive auxiliary management tool of a power grid, can convert water energy into a carrier, provides energy storage service and multi-working-condition scheduling operation for the system, undertakes tasks of peak regulation, valley filling, frequency modulation, phase modulation, accident standby, black start and the like in the power grid, and is a voltage stabilizer, a regulator and a memory of a modern power system. The variable speed pumped storage power station has the following advantages: 1. the rotating speed of the motor is adjustable, the running efficiency of the water pump turbine is improved, and the abrasion is reduced; 2. the active power is adjustable under the working conditions of electromotion and power generation, the power adjusting speed is high, and the adjusting precision of the power grid frequency is high; 3. the unit has small amplitude and high running stability; 4. can be automatically started without a starting device. For a variable-speed unit with hundred MW-level capacity, the capacity of the alternating-current excitation system used as excitation and active and reactive control of the variable-speed double-fed motor is proportional to the capacity of the whole machine and is about dozens of MVA. Due to the voltage and current limitation of power electronic devices, the capacity of equipment is improved in a multi-module parallel connection mode.
Due to the limitation of the switching frequency of a large-capacity power electronic device, the harmonic content of the grid-side converter is high, and due to the high capacity, the total harmonic input into a power grid at the grid side is high. In order to reduce harmonic waves, a mode of phase-shifting transformers is generally adopted for the parallel connection of multiple modules, but for a topology with a large number of modules, the transformers sequentially shift the phase, N kinds of transformers (N is the number of the parallel modules) are required to be used, the design is complex, the precision requirement is high, the production cost is high, and the realization is difficult.
Disclosure of Invention
The invention aims to provide an alternating current excitation system and a PWM control method of a grid-side converter of the alternating current excitation system, which are used for solving the problem that the conventional mode for reducing grid-side harmonic waves is difficult to realize.
In order to achieve the above object, the present invention provides a PWM control method for a grid-side converter of an ac excitation system, comprising the steps of:
1) the network side converter comprises a plurality of network side modules which are connected in parallel, each network side module is connected with a corresponding excitation transformer, the phase of each excitation transformer is not shifted, and the triangular carrier waves of each network side module are sequentially shifted by a set angle to obtain the phase-shifted carrier waves of each network side module;
2) and comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate the driving pulse of the corresponding network side module.
The method has the advantages that because the excitation transformer on the network side does not shift the phase, after the triangular carrier wave is compared with the modulation wave, the driving pulse of each network side module only misplaces the phase shift angle of the triangular carrier wave, so that the output harmonic waves are overlapped in a phase shift manner, and the harmonic amplitude of the total current after parallel connection is reduced; if the non-phase-shifting excitation transformer is used, the design and production cost of the transformer is reduced, the precision requirement is reduced, and therefore the realization and implementation are easy.
Further, in order to obtain a better harmonic reduction effect, the set angle is
Wherein N is the number of the network side modules connected in parallel, and 2 pi is the period of the triangular carrier wave.
Further, each excitation transformer is an isolation type excitation transformer. The isolated design blocks the path of the parallel circulating current, thereby avoiding the problem of circulating current.
The invention provides an alternating current excitation system, which comprises a machine side converter, a network side converter, an excitation transformer set and a control module, wherein the machine side converter is connected with the machine side converter; the direct current side of the machine side converter is connected with the direct current side of the grid side converter, the grid side converter comprises a plurality of grid side modules which are connected in parallel, each grid side module is connected with one exciting transformer in an exciting transformer bank, and non-phase shifting is performed among the exciting transformers; the control module controls and connects each network side module to realize the following steps:
1) sequentially shifting the phase of the triangular carrier wave of each network side module by a set angle to obtain the phase-shifted carrier wave of each network side module;
2) and comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate the driving pulse of the corresponding network side module.
The method has the advantages that because the excitation transformer on the network side does not shift the phase, after the triangular carrier wave is compared with the modulation wave, the driving pulse of each network side module only misplaces the phase shifting angle of the triangular carrier wave, thereby realizing the carrier phase shifting and reducing the harmonic amplitude of the total current after parallel connection; if the non-phase-shifting excitation transformer is used, the design and production cost of the transformer is reduced, the precision requirement is reduced, and therefore the realization and implementation are easy.
Further, each excitation transformer is an isolation type excitation transformer. The isolated design blocks the path of the parallel circulating current, thereby avoiding the problem of circulating current.
Drawings
FIG. 1 is a hardware topology of an AC excitation system of the present invention;
FIG. 2 is a close-up view of the hardware topology of an AC excitation system of the present invention;
fig. 3 is a control block diagram of a PWM control method of a grid-side converter of an ac excitation system according to the present invention;
FIG. 4 is a schematic carrier phase shift diagram of a PWM control method for a grid-side converter of an AC excitation system according to the present invention;
in the figure, 1 is a machine side converter, 2 is a direct current Crowbar, 3 is a grid side converter, 4 is a grid-connected/soft-start circuit breaker, and 5 is an excitation transformer bank.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the system is as follows:
the invention provides an alternating current excitation system, as shown in figure 1, comprising a machine side converter 1, a network side converter 3, an excitation transformer bank 5 and a control module; the grid-side converter 3 comprises 7 grid-side modules which are connected in parallel, the alternating current side of the machine-side converter 1 is used for connecting power generation equipment, the direct current side of the machine-side converter 1 is connected with the direct current side of each grid-side module through an independent direct current bus, and a direct current Crowbar 2 is arranged in the independent direct current bus; the excitation transformer set 5 comprises 7 excitation transformers, each network side module is connected with one excitation transformer through a grid-connected/soft-on circuit breaker 4, and the excitation transformers are used for being connected with a power grid; the control module controls and is connected with the machine side converter 1, the grid side converter 3 and the grid-connected/soft-on circuit breaker 4. The specific circuit of dc Crowbar 2 is shown in fig. 2.
The excitation transformer is an isolation transformer, also called isolation excitation transformer, which changes the voltage of the power grid to the voltage grade suitable for the grid-side converter and isolates the parallel points of each module.
The control module controls and connects each network side module, and the following steps are realized:
1) and sequentially shifting the phase of the triangular carrier wave of each network side module by a set angle to obtain the phase-shifted carrier wave of each network side module.
Set an angle of
Wherein, N is the number of the network side modules connected in parallel, 2 pi is the period of the triangular carrier wave, and N of the invention is 7. In other embodiments, the set angle may be set according to actual requirements.
The control block diagram of each network side module is shown in fig. 3 (a common direct-current voltage outer ring and current inner ring dq decoupling control method), the control of the network side module uses grid voltage directional vector control, and the outer ring is a direct-current voltage outer ring, namely UdcAnd Udc *And the inner ring is a current inner ring. The phase-locked loop PLL of the control loop of each network side module is used for phase-locking the secondary side voltage of the isolated excitation transformer, and because the structural parameters of the isolated excitation transformer of each network side module are the same, the wiring mode is the same, the secondary side voltage is basically the same, and the phase-locked loop angle of each network side module is also the same. Since the electrical and control parameters of each grid-side module are substantially the same, and the target setting of the dc voltage is set to the same value in the control, and the reactive current setting is set to the same value, the amplitude and phase of the output modulated wave are also substantially the same. Each network side module is provided with a respective control loop, network side control aims at stabilizing direct current voltage, and the isolated excitation variable secondary side phase locking of each module is carried out by using a control mode of network voltage orientation, so that N-path modulation waves are finally generated.
In the SVPWM link, the modulated waves of the net side module No. 1, i.e., GM1, to the net side module No. 7, i.e., GM7, are carrier-phase-shifted. The phase of the triangular carrier of the No. 1 network side module is taken as the reference of phase shift 0, and the triangular carrier of the No. 2 network side module is moved
No. 3 net side module moves
No. 4 net side module moves
No. 7 net side module moves
Forming a symmetrical phase-shifted carrier. The phase-shifted carrier diagram of the 7 net-side modules is shown in fig. 4.
2) And comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate the driving pulse of the corresponding network side module.
For the alternating current excitation system topology with the module outlet parallel points directly connected or connected through the circulating current suppression inductor, carrier phase shift can occur, and zero-sequence circulating current and non-zero-sequence circulating current flow between the modules can occur.
Because carrier phase shifting is used, the harmonic waves of the total current of the parallel point network side are superposed after the phase shifting of the harmonic waves of each network side module, the carrier phase shifting is not carried out, and the harmonic waves are directly superposed in the same phase, so the harmonic amplitude of the total current after the parallel connection can be reduced by using the carrier phase shifting.
In the invention, the steps realized by the control module can be realized in a software mode, if the carrier is subjected to phase shifting in the software, the realization is simple and convenient, and the hardware is not increased; or may be implemented by hardware such as corresponding actual circuit, and therefore, the present invention is not limited.
The method comprises the following steps:
the invention provides a PWM control method of a network side converter of an alternating current excitation system, which sequentially shifts the phase of a triangular carrier of each network side module by a set angle to obtain the phase-shifted carrier of each network side module; comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate a driving pulse of the corresponding network side module; the specific content is the same as the process in the system embodiment, and is not described herein again.
The present invention has been described in relation to particular embodiments thereof, but the invention is not limited to the described embodiments. In the thought given by the present invention, the technical means in the above embodiments are changed, replaced, modified in a manner that is easily imaginable to those skilled in the art, and the functions are basically the same as the corresponding technical means in the present invention, and the purpose of the invention is basically the same, so that the technical scheme formed by fine tuning the above embodiments still falls into the protection scope of the present invention.
Claims (5)
1. A PWM control method of a grid-side converter of an AC excitation system is characterized by comprising the following steps:
1) the network side converter comprises a plurality of network side modules which are connected in parallel, each network side module is connected with a corresponding excitation transformer, the phase of each excitation transformer is not shifted, and the triangular carrier waves of each network side module are sequentially shifted by a set angle to obtain the phase-shifted carrier waves of each network side module;
2) and comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate the driving pulse of the corresponding network side module.
2. The method of claim 1, wherein the set angle is set to be the PWM control of the ac excitation system grid-side converter
Wherein N is the number of the network side modules connected in parallel, and 2 pi is the period of the triangular carrier wave.
3. The PWM control method of an ac excitation system grid-side converter according to claim 1 or 2, wherein each excitation transformer is an isolated excitation transformer.
4. An alternating current excitation system comprises a machine side converter, a network side converter, an excitation transformer set and a control module; the direct current side of the machine side converter is connected with the direct current side of the grid side converter, and the machine side converter is characterized by comprising a plurality of grid side modules which are connected in parallel, each grid side module is connected with an excitation transformer in an excitation transformer bank, and the phase of each excitation transformer is not shifted; the control module controls and connects each network side module to realize the following steps:
1) sequentially shifting the phase of the triangular carrier wave of each network side module by a set angle to obtain the phase-shifted carrier wave of each network side module;
2) and comparing the modulated wave of each network side module with the phase-shifted carrier wave of the corresponding network side module respectively to generate the driving pulse of the corresponding network side module.
5. An alternating current excitation system according to claim 4 wherein each excitation transformer is an isolated excitation transformer.
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| CN201910883443.2A CN112531764A (en) | 2019-09-18 | 2019-09-18 | Alternating current excitation system and PWM control method of grid-side converter thereof |
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| CN201910883443.2A CN112531764A (en) | 2019-09-18 | 2019-09-18 | Alternating current excitation system and PWM control method of grid-side converter thereof |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102122596A (en) * | 2010-01-08 | 2011-07-13 | 马志刚 | Direct current smart power grid |
| WO2015079540A1 (en) * | 2013-11-28 | 2015-06-04 | 三菱電機株式会社 | Power conversion device |
| CN104852557A (en) * | 2015-06-12 | 2015-08-19 | 扬州大学 | Digital-analog hybrid phase-shift frequency-multiplication modulation method for power converter |
| WO2016086456A1 (en) * | 2014-12-02 | 2016-06-09 | 永济新时速电机电器有限责任公司 | Traction converter main circuit in high-speed motor train unit bogie power supply mode |
| CN107425545A (en) * | 2017-07-31 | 2017-12-01 | 上海交通大学 | The optimization modulator approach of volage current transformer in cascaded H-bridges |
-
2019
- 2019-09-18 CN CN201910883443.2A patent/CN112531764A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102122596A (en) * | 2010-01-08 | 2011-07-13 | 马志刚 | Direct current smart power grid |
| WO2015079540A1 (en) * | 2013-11-28 | 2015-06-04 | 三菱電機株式会社 | Power conversion device |
| WO2016086456A1 (en) * | 2014-12-02 | 2016-06-09 | 永济新时速电机电器有限责任公司 | Traction converter main circuit in high-speed motor train unit bogie power supply mode |
| CN104852557A (en) * | 2015-06-12 | 2015-08-19 | 扬州大学 | Digital-analog hybrid phase-shift frequency-multiplication modulation method for power converter |
| CN107425545A (en) * | 2017-07-31 | 2017-12-01 | 上海交通大学 | The optimization modulator approach of volage current transformer in cascaded H-bridges |
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