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Dual-frequency modulation method for quasi-Z source three-level direct current boost converter

A technology of boost converter and modulation method, which is applied in the direction of converting DC power input to DC power output, adjusting electrical variables, instruments, etc., and can solve the problems that cannot be truly applied to fuel cell voltage conversion occasions, lack of switch state, etc., and achieve Effect of high voltage gain, low device voltage stress, and small input current ripple

Inactive Publication Date: 2018-02-23
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Since the 180-degree phase-shift modulation strategy adopted by the converter only includes three switching states, that is, the lack of S 1 S 2 = 00 switch state, can not really apply to fuel cell voltage conversion occasions

Method used

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  • Dual-frequency modulation method for quasi-Z source three-level direct current boost converter
  • Dual-frequency modulation method for quasi-Z source three-level direct current boost converter
  • Dual-frequency modulation method for quasi-Z source three-level direct current boost converter

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Embodiment 1

[0033] In order to make the quasi-Z source three-level step-up DC converter topology with a wide input voltage range more suitable for the voltage conversion occasions of fuel cells, the embodiment of the present invention proposes a quasi-Z source three-level DC boost converter topology for this topology. The dual-frequency modulation method of the voltage converter, see figure 1 , the method includes the following steps:

[0034] 101: Obtain the expression of the time occupied by the four power switch states in one working cycle;

[0035] 102: Set the modulation degree of the drive signal of the power switch to 1 / 31 and L 2 Satisfied volt-second balance relation;

[0036] 103: Obtain the voltage stress expression of each capacitor through the expression of time and the volt-second balance relation, and then obtain the voltage gain;

[0037] 104: Obtain the voltage stress of the capacitor according to the voltage stress expression and the voltage gain; meanwhile obtain the...

Embodiment 2

[0040] Combine below figure 1 , figure 2 , and the specific calculation formula further introduces the scheme in embodiment 1, see the following description for details:

[0041] 201: Acquire 2 power switches (Q 1 and Q 2 ) The expressions of the time occupied by the four power switch states in one duty cycle;

[0042] (1) Wide voltage gain

[0043] figure 2 The capacitance value and the inductance value in the shown topology are infinite, that is, when the topology runs stably, the voltage value on the capacitor and the current value flowing through the inductor are approximately constant.

[0044] figure 2 All devices in the topology shown are ideal devices (power switch does not consider the conduction voltage drop and conduction internal resistance, and the passive device does not consider parasitic parameters).

[0045] 2 power switches (Q 1 and Q 2 ) of the four power switching states (11, 01, 00, 10) in one cycle take time respectively by t 1 , t 2 , t 3 ...

Embodiment 3

[0062] Combine below Figure 3-Figure 7 The scheme in embodiment 1 and 2 is further introduced, see the following description for details:

[0063] image 3 The main working waveforms of the quasi-Z source three-level step-up DC converter topology under the control of the dual-frequency 180-degree phase-shift modulation strategy are shown, and Figure 4 , Figure 5 , Figure 6 and Figure 7 The topological equivalent circuit diagram of the present invention is described. In one carrier cycle, the converter experiences four switching states, and the four switching states are described below:

[0064] (1) When the two switches are turned on at the same time, the equivalent circuit diagram of this state is as follows Figure 4 shown. according to image 3 Corresponding S 1 S 2 It can be seen from the waveform diagram during the switch state of =11 that, in this state, both power switches are turned on, and the diode D 1 -D 3 Both are off. Therefore, U in with capaci...

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Abstract

The invention discloses a dual-frequency modulation method for a quasi-Z source three-level direct current boost converter. The dual-frequency modulation method is applied to a fuel cell electric vehicle and comprises the steps that the expression of the time occupied by four power switch states in a duty cycle is acquired; the modulation degree of the drive signal of a power switch is set to 1 / 3<m<1, and a volt-second balance relation between inductor L1 and L2 in a continuous current mode is acquired; the voltage stress expression of each capacitor is acquired through the expression of timeand the volt-second balance relation, and then voltage gain is acquired; the voltage stress of each capacitor is acquired according to the voltage stress expression and the voltage gain; and the voltage stress withstood by all turned off power devices is acquired. According to the invention, the voltage gain of a topology is improved without changing the number of topological devices; the advantage of low voltage stress of original power devices is retained; and the topology is suitable for voltage conversion occasions of fuel cells.

Description

technical field [0001] The invention relates to the technical field of power electronic power conversion and modulation, in particular to a dual-frequency modulation method for a quasi-Z source three-level DC boost converter, and the dual-frequency modulation method can be applied to fuel cell electric vehicles. Background technique [0002] With the increase of the number of automobiles, people pay more and more attention to the environmental pollution caused by the exhaust emissions of automobiles worldwide. Governments of various countries are increasing the development and research of new energy vehicles. Because the fuel cell generates electricity through the chemical reaction of hydrogen and oxygen, the product of the reaction is water, which has no pollution to the environment, and the current fuel cell operation is relatively efficient and reliable. Therefore, fuel cell electric vehicles have become an important part of new energy electric vehicles. However, due to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/155
Inventor 王萍傅传智张云
Owner TIANJIN UNIV
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