Power electronic transformer switch control system based on direct current side capacitance resonance
阅读说明：本技术 基于直流侧电容谐振的电力电子变压器开关控制系统 (Power electronic transformer switch control system based on direct current side capacitance resonance ) 是由 赵聪 李子欣 胡钰杰 李耀华 于 2021-01-07 设计创作，主要内容包括：本发明属于电力电子变压器控制策略领域,具体涉及了一种基于直流侧电容谐振的电力电子变压器开关控制系统,旨在解决现有技术无法在降低控制复杂度、保证可靠性的前提下,实现电力电子变压器功率密度的提升的问题。本发明包括：第一变流器、第二变流器和第三变流器构成；根据第一变流器交流输入侧电压极性控制第一变流器和第三变流器功率半导体导通与关断；根据第二变流器电路参数计算第二变流器功率半导体开关周期,控制第二变流器功率半导体导通与关断,从而实现电力电子变压器输入电压至输出电压变换。本发明在降低控制复杂度、保证可靠性的前提下,提高电力电子变压器的功率密度。(The invention belongs to the field of control strategies of power electronic transformers, particularly relates to a power electronic transformer switch control system based on direct-current side capacitance resonance, and aims to solve the problem that the power density of a power electronic transformer cannot be improved on the premise of reducing control complexity and ensuring reliability in the prior art. The invention comprises the following steps: the converter comprises a first converter, a second converter and a third converter; controlling the power semiconductors of the first converter and the third converter to be switched on and off according to the voltage polarity of the alternating current input side of the first converter; and calculating the switching period of the power semiconductor of the second converter according to the circuit parameters of the second converter, and controlling the power semiconductor of the second converter to be switched on and off, thereby realizing the conversion from the input voltage to the output voltage of the power electronic transformer. The invention improves the power density of the power electronic transformer on the premise of reducing the control complexity and ensuring the reliability.)
1. A power electronic transformer switch control system based on direct current side capacitance resonance is characterized by comprising a first converter, a second converter and a third converter;
the first converter comprises a power semiconductor S1, a power semiconductor S2, a power semiconductor S3 and a power semiconductor S4 and is used for converting an input-side alternating voltage UinConverted to a DC voltage Udc1；
The second converter comprises a power semiconductor Q1, a power semiconductor Q2, a power semiconductor Q3, a power semiconductor Q4, a power semiconductor Q5, a power semiconductor Q6, a power semiconductor Q7, a power semiconductor Q8, a capacitor C1, a capacitor C2 and a high-frequency transformer, and is used for converting the direct-current voltage U into the direct-current voltage Udc1Converted to a DC voltage Udc2(ii) a The leakage inductance of the high-frequency transformer is LδThe turn ratio of the primary side to the secondary side is n: 1;
the third converter comprises a power semiconductor R1, a power semiconductor R2, a power semiconductor R3 and a power semiconductor R4 and is used for converting the direct-current voltage U into the direct-current voltage Udc2Converted into an output-side alternating voltage Uout。
2. A power electronic transformer switch control system based on dc side capacitive resonance as claimed in claim 1, wherein said first converter is connected in the relationship:
the source electrode of the power semiconductor S1 and the drain electrode of the power semiconductor S2 are connected together to serve as a positive input end of the first current transformer;
the source electrode of the power semiconductor S3 and the drain electrode of the power semiconductor S4 are connected together to serve as a negative input end of the first converter;
the drain electrode of the power semiconductor S1 and the drain electrode of the power semiconductor S3 are connected together to serve as a positive output end of the first converter;
the source of the power semiconductor S2 and the source of the power semiconductor S4 are connected together as the negative output of the first current transformer.
3. A power electronic transformer switch control system based on dc side capacitive resonance as claimed in claim 2, characterized in that said second converter is connected in the relationship:
the source electrode of the power semiconductor Q1 and the drain electrode of the power semiconductor Q2 are connected to the positive input end of the high-frequency transformer together;
the source electrode of the power semiconductor Q3 and the drain electrode of the power semiconductor Q4 are connected to the negative input end of the high-frequency transformer together;
the drain electrode of the power semiconductor Q1 and the drain electrode of the power semiconductor Q3 are connected to the positive electrode of a capacitor C1 to serve as the positive input end of the second converter;
the source electrode of the power semiconductor Q2 and the source electrode of the power semiconductor Q4 are connected to the negative electrode of a capacitor C1 together to serve as the negative input end of the second converter;
the positive input end of the second converter is connected to the positive output end of the first converter; the negative input end of the second converter is connected to the negative output end of the first converter;
the source electrode of the power semiconductor Q5 and the drain electrode of the power semiconductor Q6 are connected to the positive output end of the high-frequency transformer together;
the source electrode of the power semiconductor Q7 and the drain electrode of the power semiconductor Q8 are connected to the negative output end of the high-frequency transformer together;
the drain electrode of the power semiconductor Q5 and the drain electrode of the power semiconductor Q7 are connected to the positive electrode of a capacitor C2 together to serve as the positive output end of the second converter;
the source of the power semiconductor Q6 and the source of the power semiconductor Q8 are connected together to the cathode of the capacitor C2 as the negative output terminal of the second converter.
4. A power electronic transformer switch control system based on dc side capacitive resonance according to claim 3, characterized in that the third converter has the connection relationship:
the source electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R2 are connected together to serve as a positive output end of the third converter;
the source electrode of the power semiconductor R3 and the drain electrode of the power semiconductor R4 are connected together to serve as the negative output end of the third converter;
the drain electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R3 are connected together to serve as a positive input end of a third converter;
the source electrode of the power semiconductor R2 and the source electrode of the power semiconductor R4 are connected together to serve as a negative input end of the third converter;
the positive input end of the third converter is connected to the positive output end of the second converter; and the negative input end of the third converter is connected to the negative output end of the second converter.
5. A power electronic transformer switch control system based on dc side capacitive resonance as claimed in claim 1, wherein said first converter operates as:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor S1 and the power semiconductor S4 of the first converter are conducted, and the power semiconductor S2 and the power semiconductor S3 are turned off;
when the voltage U of the AC input side of the first converterinWhen the amplitude is negative, the power semiconductor S2 and the power semiconductor S3 of the first converter are turned on, and the power semiconductor S1 and the power semiconductor S4 are turned off.
6. A power electronic transformer switch control system based on dc side capacitive resonance as claimed in claim 1, characterized in that said second converter has a resonance period of:
wherein T is the resonance period of the second converter, LδInductance value, C, being leakage inductance of high-frequency transformer1And C2The capacitance values of capacitor C1 and capacitor C2, respectively.
7. A power electronic transformer switch control system based on DC side capacitive resonance as claimed in claim 6 wherein the second converter, its power semiconductors have a period of:
Ts＝2T,s＝1,2,…,8
wherein, TsWhen s is 1,2, …,8 is the cycle of power semiconductor Q1, power semiconductor Q2, power semiconductor Q3, power semiconductor Q4, power semiconductor Q5, power semiconductor Q6, power semiconductor Q7, and power semiconductor Q8 in the second converter.
8. A power electronic transformer switch control system based on DC side capacitance resonance as claimed in claim 7, characterized in that said second converter operates as:
when the time is kTs～(k+1)TsWhen the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 of the second converter are on, the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 are off;
when the time is (k +1) Ts～(k+2)TsWhen the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 of the second converter are on, the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 are off;
wherein k is an integer greater than or equal to 0.
9. A power electronic transformer switch control system based on dc side capacitive resonance as claimed in claim 1, wherein said third converter operates as:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor R1 and the power semiconductor R4 of the third converter are conducted, and the power semiconductor R2 and the power semiconductor R3 are turned off;
when the voltage U of the AC input side of the first converterinThe amplitude is negativeAt this time, the power semiconductor R2 and the power semiconductor R3 of the third converter are turned on, and the power semiconductor R1 and the power semiconductor R4 are turned off.
Technical Field
The invention belongs to the field of control strategies of power electronic transformers, and particularly relates to a power electronic transformer switch control system based on direct-current side capacitance resonance.
Background
The proportion of renewable energy power generation systems such as wind energy and photovoltaic in the existing power grid is being increased year by year, the indirection and volatility of the renewable energy power generation systems also put higher requirements on the controllability of the connected power grid, and the improvement of the regulation capacity of the power grid system, the enhancement of the new energy consumption capacity and the development of high-efficiency energy-saving technology also become key points of strategic planning and research and development of the future power grid. The power electronic transformer generally refers to a novel multifunctional power electronic device realized by a power electronic conversion technology and a high-frequency isolation transformer. The power electronic transformer not only has the voltage transformation and isolation functions of the traditional power frequency transformer, but also can realize harmonic wave treatment, reactive compensation, renewable energy power generation system access, port fault isolation and intelligent equipment communication, and is one of key equipment for developing intelligent power grids and energy internet in the future.
The existing power electronic transformers which have been widely researched mainly have circuit topologies based on two types of cascaded H-bridges and modular multilevel converters. The cascade H-bridge type power electronic transformer is composed of a double-active-bridge converter and an H-bridge module, wherein the double-active-bridge converter is connected with the input in series and the output in parallel. The modular multilevel converter type power electronic transformer is formed by connecting a double-active-bridge converter with serial input and parallel output and a modular multilevel converter high-voltage direct current side. The power electronic transformers with two structures have the defects of large volume, heavy weight and the like of an energy storage capacitor, and the improvement of the power density of the power electronic transformers is seriously restricted. In addition, the existing power electronic transformer generally has the defect of low operation efficiency, so that the size of a heat dissipation system is large, and the power density of the power electronic transformer is further reduced.
In order to solve the problems, some documents propose a power electronic transformer [1] based on a full-bridge type modular multilevel converter, and although an isolation link is only provided with one high-frequency transformer, the volume of an energy storage capacitor of the full-bridge type modular multilevel converter is still larger, and the power density is lower. Some documents propose that a full-bridge modular multilevel converter is used for directly outputting high-frequency voltage and current to reduce the number of electric energy conversion stages [2], but the high-frequency voltage causes the full-bridge modular multilevel converter to have high switching frequency, low efficiency and difficult improvement of power density. Some documents propose a power electronic transformer circuit topology [3] capable of realizing redundant operation of input series and output parallel double-active-bridge converters, which can improve the operation reliability of the power electronic transformer, but the structure has more power semiconductor devices, a resonant circuit also needs a resonant capacitor, and the power density is lower. There are also some documents that propose a power electronic transformer circuit topology [4] based on matrix transformation, in which a high-frequency circuit does not need a resonance capacitor, but filter capacitors need to be arranged on both the input and output sides, and it is difficult to improve the power density. In addition, the matrix converter has the defects of complex control, difficult protection and the like, so that the reliability of the power electronic transformer is low.
Generally speaking, the power module of the existing power electronic transformer needs a direct current capacitor to bear direct current voltage, the direct current capacitor is large and can generally reach the mF level, and in addition, a high-frequency loop needs a resonant capacitor to complete resonant soft switching, so that the existing power electronic transformer has the disadvantages of large quantity of capacitors, large capacitance value and large occupied space, and the power density is low.
The following documents are background information related to the present invention:
[1] wangting, wangwogong column, zhang xun, wujui, power electronic transformer control strategy based on modular multilevel matrix converter, volume 31, 18 th of 2016 technical report of electricians.
[2] High strength, plum blossom, xufei, king hucho, Zhao cong, wangping and Li dazzling, a high frequency chain modular power electronic transformer, new technology of electrician and electric energy, 36 th volume in 2017 and 5 th period.
[3] Zhao smart, high fangqiang, plum blossom, king huo, plum blossom, power electronic transformer, bidirectional dc converter and its control method, CN109039081A, 20180620.
[4] Wuwar, Yangyu, Yangjimei, Jiyuu, Feiyi, Xuxiandao, Chenming, Yuanyuan and Liqiang, a power electronic transformer, CN110034687A, 20190418.
Disclosure of Invention
In order to solve the above problems in the prior art, that is, the prior art cannot realize the improvement of the power density of the power electronic transformer on the premise of reducing the control complexity and ensuring the reliability, the invention provides a power electronic transformer switch control system based on direct-current side capacitance resonance, a high-frequency loop of the power electronic transformer does not need a resonance capacitor, and a capacitor C1 and a capacitor C2 on the direct-current side of the power electronic transformer are both in the mu F level, so that the volume of the power electronic transformer is greatly reduced, and the power density of the power electronic transformer is improved, wherein the system comprises a first converter, a second converter and a third converter;
the first converter comprises a power semiconductor S1, a power semiconductor S2, a power semiconductor S3 and a power semiconductor S4 and is used for converting an input-side alternating voltage UinConverted to a DC voltage Udc1；
The second converter comprises a power semiconductor Q1, a power semiconductor Q2, a power semiconductor Q3, a power semiconductor Q4, a power semiconductor Q5, a power semiconductor Q6, a power semiconductor Q7, a power semiconductor Q8, a capacitor C1, a capacitor C2 and a high-frequency transformer, and is used for converting the direct-current voltage U into the direct-current voltage Udc1Converted to a DC voltage Udc2(ii) a The leakage inductance of the high-frequency transformer is LδThe turn ratio of the primary side to the secondary side is n: 1;
the third converter comprises a power semiconductor R1, a power semiconductor R2, a power semiconductor R3 and a power semiconductor R4 and is used for converting the direct-current voltage U into the direct-current voltage Udc2Converted into an output-side alternating voltage Uout。
In some preferred embodiments, the first converter has a connection relationship of:
the source electrode of the power semiconductor S1 and the drain electrode of the power semiconductor S2 are connected together to serve as a positive input end of the first current transformer;
the source electrode of the power semiconductor S3 and the drain electrode of the power semiconductor S4 are connected together to serve as a negative input end of the first converter;
the drain electrode of the power semiconductor S1 and the drain electrode of the power semiconductor S3 are connected together to serve as a positive output end of the first converter;
the source of the power semiconductor S2 and the source of the power semiconductor S4 are connected together as the negative output of the first current transformer.
In some preferred embodiments, the second converter has a connection relationship of:
the source electrode of the power semiconductor Q1 and the drain electrode of the power semiconductor Q2 are connected to the positive input end of the high-frequency transformer together;
the source electrode of the power semiconductor Q3 and the drain electrode of the power semiconductor Q4 are connected to the negative input end of the high-frequency transformer together;
the drain electrode of the power semiconductor Q1 and the drain electrode of the power semiconductor Q3 are connected to the positive electrode of a capacitor C1 to serve as the positive input end of the second converter;
the source electrode of the power semiconductor Q2 and the source electrode of the power semiconductor Q4 are connected to the negative electrode of a capacitor C1 together to serve as the negative input end of the second converter;
the positive input end of the second converter is connected to the positive output end of the first converter; the negative input end of the second converter is connected to the negative output end of the first converter;
the source electrode of the power semiconductor Q5 and the drain electrode of the power semiconductor Q6 are connected to the positive output end of the high-frequency transformer together;
the source electrode of the power semiconductor Q7 and the drain electrode of the power semiconductor Q8 are connected to the negative output end of the high-frequency transformer together;
the drain electrode of the power semiconductor Q5 and the drain electrode of the power semiconductor Q7 are connected to the positive electrode of a capacitor C2 together to serve as the positive output end of the second converter;
the source of the power semiconductor Q6 and the source of the power semiconductor Q8 are connected together to the cathode of the capacitor C2 as the negative output terminal of the second converter.
In some preferred embodiments, the third converter has a connection relationship of:
the source electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R2 are connected together to serve as a positive output end of the third converter;
the source electrode of the power semiconductor R3 and the drain electrode of the power semiconductor R4 are connected together to serve as the negative output end of the third converter;
the drain electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R3 are connected together to serve as a positive input end of a third converter;
the source electrode of the power semiconductor R2 and the source electrode of the power semiconductor R4 are connected together to serve as a negative input end of the third converter;
the positive input end of the third converter is connected to the positive output end of the second converter; and the negative input end of the third converter is connected to the negative output end of the second converter.
In some preferred embodiments, the first converter operates as follows:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor S1 and the power semiconductor S4 of the first converter are conducted, and the power semiconductor S2 and the power semiconductor S3 are turned off;
when the voltage U of the AC input side of the first converterinWhen the amplitude is negative, the power semiconductor S2 and the power semiconductor S3 of the first converter are turned on, and the power semiconductor S1 and the power semiconductor S4 are turned off.
In some preferred embodiments, the second current transformer has a resonant period of:
wherein T is the resonance period of the second converter, LδInductance value, C, being leakage inductance of high-frequency transformer1And C2The capacitance values of capacitor C1 and capacitor C2, respectively.
In some preferred embodiments, the second converter, the power semiconductor period of which is:
Ts＝2T,s＝1,2,…,8
wherein, TsWhen s is 1,2, …,8 is the cycle of power semiconductor Q1, power semiconductor Q2, power semiconductor Q3, power semiconductor Q4, power semiconductor Q5, power semiconductor Q6, power semiconductor Q7, and power semiconductor Q8 in the second converter.
In some preferred embodiments, the second converter operates as follows:
when the time is kTs～(k+1)TsWhen the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 of the second converter are on, the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 are off;
when the time is (k +1) Ts～(k+2)TsWhen the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 of the second converter are on, the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 are off;
wherein k is an integer greater than or equal to 0.
In some preferred embodiments, the third converter operates as follows:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor R1 and the power semiconductor R4 of the third converter are conducted, and the power semiconductor R2 and the power semiconductor R3 are turned off;
when the voltage U of the AC input side of the first converterinWhen the amplitude is negative, the power semiconductor R2 and the power semiconductor R3 of the third converter are turned on, and the power semiconductor R1 and the power semiconductor R4 are turned off.
The invention has the beneficial effects that:
(1) the power electronic transformer switch control system based on the direct-current side capacitor resonance can enable the capacitor on the direct-current side of the power electronic transformer to participate in resonance, not only can reduce the number of high-frequency loop resonance capacitors, but also can greatly reduce the energy storage capacitance value of the power electronic transformer, thereby improving the power density of the power electronic transformer on the premise of reducing the control complexity and ensuring the reliability.
(2) The power electronic transformer switch control system based on the direct-current side capacitor resonance is simple in structure, simplifies the control process, reduces the cost and improves the control efficiency while improving the power density of the power electronic transformer.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIG. 1 is a schematic topology diagram of a power electronic transformer switch control system based on DC side capacitance resonance according to the present invention;
fig. 2 is a simulation diagram of an embodiment of a power electronic transformer switch control system based on dc side capacitance resonance according to the present invention.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention relates to a power electronic transformer switch control system based on direct-current side capacitance resonance, which comprises a first converter, a second converter and a third converter;
the first converter comprises a power semiconductor S1, a power semiconductor S2, a power semiconductor S3 and a power semiconductor S4 and is used for converting an input-side alternating voltage UinConverted to a DC voltage Udc1；
The second converter comprises a power semiconductor Q1, a power semiconductor Q2, a power semiconductor Q3, a power semiconductor Q4 and a power semiconductorA conductor Q5, a power semiconductor Q6, a power semiconductor Q7, a power semiconductor Q8, a capacitor C1, a capacitor C2 and a high-frequency transformer for converting the DC voltage Udc1Converted to a DC voltage Udc2(ii) a The leakage inductance of the high-frequency transformer is LδThe turn ratio of the primary side to the secondary side is n: 1;
the third converter comprises a power semiconductor R1, a power semiconductor R2, a power semiconductor R3 and a power semiconductor R4 and is used for converting the direct-current voltage U into the direct-current voltage Udc2Converted into an output-side alternating voltage Uout。
In order to more clearly describe the power electronic transformer switch control system based on dc side capacitance resonance, the following describes each module in the embodiment of the present invention in detail with reference to fig. 1.
The power electronic transformer switch control system based on the direct current side capacitance resonance comprises a first converter, a second converter and a third converter, and the modules are described in detail as follows:
the first converter comprises a power semiconductor S1, a power semiconductor S2, a power semiconductor S3 and a power semiconductor S4 and is used for converting the input side alternating voltage UinConverted to a DC voltage Udc1The connection relationship is as follows:
the source electrode of the power semiconductor S1 and the drain electrode of the power semiconductor S2 are connected together to serve as a positive input end of the first current transformer;
the source of the power semiconductor S3 and the drain of the power semiconductor S4 are connected together as a negative input of the first inverter;
the drain of the power semiconductor S1 and the drain of the power semiconductor S3 are connected together as a positive output of the first current transformer;
the source of power semiconductor S2 and the source of power semiconductor S4 are connected together as the negative output of the first current transformer.
The working process of the first converter is as follows:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor S1 and the power semiconductor S4 of the first converter are conducted, and the power semiconductor S2 and the power semiconductorConductor S3 is off;
when the voltage U of the AC input side of the first converterinWhen the amplitude is negative, the power semiconductor S2 and the power semiconductor S3 of the first converter are turned on, and the power semiconductor S1 and the power semiconductor S4 are turned off.
The second converter comprises a power semiconductor Q1, a power semiconductor Q2, a power semiconductor Q3, a power semiconductor Q4, a power semiconductor Q5, a power semiconductor Q6, a power semiconductor Q7, a power semiconductor Q8, a capacitor C1, a capacitor C2 and a high-frequency transformer, and is used for converting the direct-current voltage U into the direct-current voltage Udc1Converted to a DC voltage Udc2(ii) a The leakage inductance of the high-frequency transformer is LδThe turn ratio of the primary side to the secondary side is n: 1; the connection relation of the second converter is as follows:
the source of the power semiconductor Q1 and the drain of the power semiconductor Q2 are connected together to the positive input terminal of the high-frequency transformer;
the source of the power semiconductor Q3 and the drain of the power semiconductor Q4 are connected together to the negative input of the high frequency transformer;
the drain of the power semiconductor Q1 and the drain of the power semiconductor Q3 are connected to the positive electrode of the capacitor C1 to serve as the positive input end of the second converter;
the source of the power semiconductor Q2 and the source of the power semiconductor Q4 are connected together to the negative pole of the capacitor C1 to serve as the negative input end of the second converter;
the positive input end of the second converter is connected to the positive output end of the first converter; the negative input end of the second converter is connected to the negative output end of the first converter;
the source of the power semiconductor Q5 and the drain of the power semiconductor Q6 are connected together to the positive output terminal of the high frequency transformer;
the source of the power semiconductor Q7 and the drain of the power semiconductor Q8 are connected together to the negative output terminal of the high frequency transformer;
the drain of the power semiconductor Q5 and the drain of the power semiconductor Q7 are connected together to the positive electrode of the capacitor C2 to serve as the positive output end of the second converter;
the source of the power semiconductor Q6 and the source of the power semiconductor Q8 together to the cathode of the capacitor C2 serve as the negative output of the second inverter.
A second current transformer having a resonant period represented by the formula (1):
wherein T is the resonance period of the second converter, LδInductance value, C, being leakage inductance of high-frequency transformer1And C2The capacitance values of capacitor C1 and capacitor C2, respectively.
The period of a power semiconductor of the second converter is shown as the formula (2):
Ts＝2T,s＝1,2,…,8 (2)
wherein, TsWhen s is 1,2, …,8 is the cycle of power semiconductor Q1, power semiconductor Q2, power semiconductor Q3, power semiconductor Q4, power semiconductor Q5, power semiconductor Q6, power semiconductor Q7, and power semiconductor Q8 in the second converter.
The working process of the second converter is as follows:
when the time is kTs～(k+1)TsWhen the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 of the second converter are on, the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 are off;
when the time is (k +1) Ts～(k+2)TsWhen the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 of the second converter are on, the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 are off;
wherein k is an integer greater than or equal to 0.
The third converter comprises a power semiconductor R1, a power semiconductor R2, a power semiconductor R3 and a power semiconductor R4 and is used for converting the direct-current voltage U into the direct-current voltage Udc2Converted into an output-side alternating voltage UoutThe connection relationship is as follows:
the source electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R2 are connected together to serve as a positive output end of the third converter;
the source electrode of the power semiconductor R3 and the drain electrode of the power semiconductor R4 are connected together to serve as the negative output end of the third converter;
the drain electrode of the power semiconductor R1 and the drain electrode of the power semiconductor R3 are connected together to serve as a positive input end of the third converter;
the source electrode of the power semiconductor R2 and the source electrode of the power semiconductor R4 are connected together to serve as the negative input end of the third converter;
the positive input end of the third converter is connected to the positive output end of the second converter; the negative input of the third converter is connected to the negative output of the second converter.
The working process of the third converter is as follows:
when the voltage U of the AC input side of the first converterinWhen the amplitude is positive, the power semiconductor R1 and the power semiconductor R4 of the third converter are conducted, and the power semiconductor R2 and the power semiconductor R3 are turned off;
when the voltage U of the AC input side of the first converterinWhen the amplitude is negative, the power semiconductor R2 and the power semiconductor R3 of the third converter are turned on, and the power semiconductor R1 and the power semiconductor R4 are turned off.
The performance of the system of the invention is verified through experiments, and the parameters of the system are shown in table 1:
TABLE 1
When the first converter AC input side voltage UinWhen the amplitude is positive, the power semiconductor S1 and the power semiconductor S4 of the first converter are conducted, and the power semiconductor S2 and the power semiconductor S3 are turned off; when the first converter AC input side voltage UinWhen the amplitude is negative, the power semiconductor S2 and the power semiconductor S3 of the first current transformer are conducted, and the power semiconductor S1 and the power semiconductorS4 is turned off.
According to the second current transformer, the capacitor C1, the capacitor C2 and the leakage inductance are LδCalculating the resonance period of the second converter, as shown in formula (3):
calculating the period of the power semiconductor of the second converter according to the resonance period of the second converter, as shown in formula (4):
Ts＝2T＝2×25μs＝50μs,s＝1,2,…,8 (4)
when the time is k50 mus to (k +1)50 mus, the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 of the second converter are turned on, and the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 are turned off;
when the time is (k +1)50 mus to (k +2)50 mus, the power semiconductor Q2, the power semiconductor Q3, the power semiconductor Q6 and the power semiconductor Q7 of the second converter are turned on, and the power semiconductor Q1, the power semiconductor Q4, the power semiconductor Q5 and the power semiconductor Q8 are turned off;
wherein k is an integer greater than or equal to 0.
When the first converter AC input side voltage UinWhen the amplitude is positive, the power semiconductor R1 and the power semiconductor R4 of the third converter are conducted, and the power semiconductor R2 and the power semiconductor R3 are turned off; when the first converter AC input side voltage UinWhen the amplitude is negative, the power semiconductor R2 and the power semiconductor R3 of the third converter are turned on, and the power semiconductor R1 and the power semiconductor R4 are turned off.
Fig. 2 is a simulation diagram of an embodiment of a power electronic transformer switch control system based on dc side capacitance resonance, where fig. 2 shows a voltage and a current at an ac input side of a first converter of a power electronic transformer in a first row, a voltage and a current at an ac output side of a third converter of the power electronic transformer in a second row, fig. 2 shows a voltage and a second capacitor of the second converter of the power electronic transformer in a third row, fig. 2 shows a voltage and a current at a primary side of a high frequency transformer of the second converter of the power electronic transformer in a fourth row, and fig. 2 shows a local voltage and a current waveform at a primary side of the high frequency transformer of the second converter of the power electronic transformer in a fifth row. According to the simulation result of the embodiment, the power electronic transformer can realize the electric energy conversion from the alternating current input voltage to the alternating current output voltage, a high-frequency link does not need a resonance capacitor, and the capacitance values of the first capacitor and the second capacitor of the second converter are smaller, so that the power electronic transformer has higher power density.
It should be noted that, the power electronic transformer switch control system based on dc side capacitance resonance provided in the foregoing embodiment is only illustrated by dividing the functional modules, and in practical applications, the functions may be distributed by different functional modules according to needs, that is, the modules or steps in the embodiments of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiments may be combined into one module, or may be further split into a plurality of sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not to be construed as unduly limiting the present invention.
The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing or implying a particular order or sequence.
The terms "comprises," "comprising," or any other similar term are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.