Research On Y-source Two-stage Matrix Converter And Its Modulation Strategy

As an important AC-AC power converter,the two-stage matrix converter can not only make the input and output of a good sinusoidal waveform,but also does not need to add energy storage components on the dc-link,bidirectional energy transfer,and power factor of approximately 1.Although the TSMC has many advantages,its voltage transmission capability is very low,which seriously limits its application and popularization.Therefore,this paper proposes the Y-source two-stage matrix converter(Y-source two-stage matrix converter,YSTSMC)and its modulation strategy to increase the range of voltage that the converter can output.Taking YSTSMC as the research object,the Y-source network is embedded in the middle of the rectifier stage and the inverter stage of the TSMC to obtain high voltage gain.Since the input voltage of the Y-source network is not a constant dc voltage,in order to analyze the impact of the fluctuation of dc-link voltage on the operated characteristics of the Y-source network,the state space average equation is written according to the two working states of system.By establishing a small signal model,the dynamic response characteristics of the system are analyzed under both steady-state and a small disturbance condition.And the relationship between the output voltage of rectifier stage and the input voltage of inverter stage is established,which provides a theoretical basis for the research on modulation strategy.To reduce commutation time and improve voltage utilization,the rectifier stage uses the space vector pulse width modulation strategy(SVPWM)strategy that does not contain zero vectors to calculate the duty ratios of the switching states.The inverter stage uses the traditional SVPWM strategy for modulation.Due to the influence of the fluctuation of dc-link voltage,the modulation ratio needs to be corrected when calculating the duty ratios.Then the introduction of the shoot-through state could improve the voltage transfer ratio of the matrix converter and limit the variation range of the modulation ratio of the inverter stage,so that the maximum voltage transfer ratio can be calculated.Finally,the duty ratios of rectifier stage and inverter stage are effectively combined to draw the sequence diagram of each voltage vector action,and the driving signals of each power switch are obtainedIn addition,the SVPWM strategy involves a large number of trigonometric function calculations,it is not convenient to achieve.Therefore,it proposes a carrier PWM strategy suitable for YSTSMC in this paper.Firstly,the duty ratios of the front stage and the latter stage can be calculated from the theory of SVPWM strategy and combined reasonably within a switching period.According to the relationship between the output average voltage of rectifier stage and the input voltage of inverter stage,the modulation ratio is corrected in real time to ensure the quality of the output voltage.Then the duty ratios of the rectifier stage and the inverter stage are respectively combined with the same carrier and obtained simple and regular modulation waves.Moreover,the shoot-through state vectors are distributed reasonably in the switch state sequence.Finally,the obtained modulation waves are compared with the same carrier to generate pulse signals which are used to produce driving signals through logic operation.The YSTSMC is controlled by this strategy to obtain a three-phase symmetrical sinusoidal input and output waveform.The YSTSMC was simulated and verified by writing the S function in MATLAB,and the three-phase symmetrical input and output sine waveforms were obtained.In this paper,the proposed SVPWM strategy and Carrier PWM strategy for YSTSMC are verified respectively by building an experimental platform in laboratory.The experimental results show that the proposed topology of YSTSMC and its two modulation strategies are scientific and reasonable,which provides a new method for improving the voltage transmission capability of TSMC.