LC Parallel Resonant Matrix Converter And Its PMSM Control System

In recent years,with the rapid development of power electronics technology,AC variable frequency drive has been widely applied.The voltage source converters based on dc-link are widely used in many fields,such as rail transportation,oil mining,industrial production and our daily life.It is almost the most common AC frequency conversion device.However,they also have problems of high harmonic current,short-life,low reliability,costly and so on.Among them,the most prominent is that there will be great harmonics in the working process,which pollute the environment of the electrical system and do harm to the electrical equipments.In order to reduce the harmonic pollution and improve the performance of the AC frequency conversion transmission system,a LC parallel resonant matrix converter is studied in this paper.The presented converter uses a small LC parallel resonant circuit to replace the short life large capacitance of dc-link converters,which improves converter's energy density and stability.In the working process,current of both the input and output are sinusoidal,the harmonic pollution is very small.Meanwhile,the switching voltage is close to zero,which greatly reduced the power loss caused by switches,therefore,the energy conversion efficiency is improved.In addition,due to the symmetrical topology and the use of bidirectional switches,the converter can achieve bidirectional energy transformation without changing the topology structure,and is suitable for four quadrant operation of AC motor.In this thesis,the development history,present situation,advantages and main problems of dc-link converters,matrix converters are summarized.Meanwhile,the research status of LC parallel resonant matrix converter is introduced.The advantages and research meaning are illustrated by comparing with the AC direct alternating converter and matrix converter.The permanent magnet synchronous motor(PMSM)is introduced.The topology and working principle of LC parallel resonant matrix converter are introduced in detail.Operation principle in each mode of one Control period is described in detail as example.The principle of current modulation is analyzed,and the calculation formula of switching time is given.The parameter selection principle of resonant capacitance and resonant inductor is introduced.The working principle of conduction voltage selection module,current control module and other modules are also given.A LC parallel resonant matrix converter energy conversion system under unity load is built and verified by simulation.A LC parallel resonant matrix converter energy conversion system under a low power factor load is analyzed,an improved control method is given and verified by simulation.Frequently used control strategy of PMSM control system is introduced.A PMSM speed regulating system based on LC parallel resonant matrix converter,PI controller and magnetic field oriented control is built and verified by simulation.