The Research On The High Power Modular Waveform Generator

Nowadays the power quality problems and distributed power generation technology have been attracting more and more attention.When we research on these technologies,high power waveform generator which could produce varieties of power waveform is an indispensable device.Waveform generator can produce three-phase adjustable sine wave,the harmonic,square wave,triangular wave,voltage drop,voltage surge and other types of power signals.It has abundant functions such as being a grid simulator,being a shore-to-ship power supply,being used as an impedance measurement device to measure the impedance of new energy resources micro-network or being applications in other field.Depending on the research foundation of our laboratory,this paper developed a modular high power waveform generator with low-harmonic,wide-band and high-precision for the shortcomings of the traditional waveform generator and studied intensively from the following aspects:(1)First of all,this paper introduced the application area,research status,development trend of the waveform generator in domestic and overseas.According to the circuit structure,waveform generator is divided into rectifier,inverter and filter.This article analyzed these three parts respectively.Compared with the three-phase rectifier circuit in different topologies,the traditional waveform generator with uncontrollable rectifier topology has the disadvantages of low power factor,high current distortion factor and high impulse to the power grid.Therefore,this paper designed a high power modular waveform generator device with the PWM converter structure.Then,we studied the topology,working principle and characteristics of the circuit with this structure.The mathematical model of the three-phase PWM rectifier circuit and the three-phase PWM inverter circuit are established.What's more,this paper designed the specific circuit parameters such as the capacitor of the DC side and the inductance of the LC output filter.(2)The control strategy of the waveform generator system is studied.The rectifier uses the proportional integral controller in voltage outer loop and deadbeat control method in current inner loop.The inverter adopts the quasi-proportional resonant control method in voltage outer loop and PI controller in current inner loop.The specific principle of the control strategy of the waveform generator is analyzed.And the transfer function of the control system is deduced.Then,the stability of the system is deeply studied and the control parameters of this system are designed by the bode diagram and the root trajectory diagram.The rationality of this control method is verified by the circuit simulation.(3)The device of 40kW modular waveform generator is developed and debugged in this article.The hardware and software design and implementation process of the waveform generator are introduced in detail.The design of the hardware circuit mainly includes the switching device and the driving module,the power supply and the heat dissipation module,the signal acquisition module,the fault detection and protection module,the human-computer interaction system and so on.The design of main program,interrupt service routine and RS-485 communication program in the software control system are given detailedly.The parameter design and component selection of each module unit are introduced.Finally,the validity of the control method and the equipment development are verified by experiments.