A Novel AC/AC Direct Frequency Converter With12Switches And Its Control Method

With the development of global economy and the improvement of human life, theconsumption of electricity is also rise rapidly, and the energy has become a big problem thatpeople all over the world have to face. According to statistics, at present about50%~60%produce in our country are used to drive ac motor to do work, and most of them ared constantspeed drived directly, and causes a great waste of electricity, forever, ac frequency conversionspeed regulating technology is one of the most important way to realize electrificationconservation. AC/AC direct frequency convert is a hot spot of the AC frequency conversionfield in recent years. Simple topology, less power transformed series, bi-directional powerflow, high input power factor, high quality output, high reliability method of direct frequencyconversion is recognized as an ideal means of frequency conversion by many people in theindustry, and therefore received more and more attention. This paper proposes a new12-switch direct frequency converter topology, and also presents a suitable control strategybased on the toplpogy.First, this paper proposes a new12-switch direct frequency converter topology, and thenexplans the operating principle of this new converter: arbitrary polarity level constructionmethod, that is, the relevance between the output line voltage status and the switching deviceof the circuit topology, and makes the form of output level circuit and switch relationship, andderives the relationship between the output line voltage and input line-voltage; thenintroduces the operating principle of energy feedback switch based on input voltage polaritydetection.Second, having research on the SPWM control strategy on traditional three-phaseinverter and combining with the characteristics of the topology this paper proposed, this paperproposes a new control strategy, that is, the SPWM with input voltage polarity detectioncontrol strategy. This paper sets up a simulation model in Simulink environment, and analysesthe simulation current and voltage outputs based on the the SPWM control strategy with inputvoltage polarity detection, and analyses the feasibility of the control strategy. Then analysesthe simulation current and voltage outputs whose frequency are in a wide range so as toanalyses whether this control strategy is feasible when outputs could be changed smoothly ina lager range used.Third, based on the simulation analysis, this paper establishes a SPWM with inputvoltage polarity detection control stragegy hardware system. The system chooses MOSFETthe switch devices and chooses IR2110and IR2117as the the MOSFET driver IC which areused to trigger the MOSFET. And compile C language promgram of the SPWM with the input voltage polarity detection control strategy, and then do a further research on the controlstrategy proposed in this paper, in order to verify the feasibility of the control strategy byways of hardware experiment.Simulation results and experimental results show that the SPWM with voltage polaritydetection control strategy for the new12-switch direct frequency converter is feasible in theend.