【作者】 贺毅；

【导师】 郭育华；

【作者基本信息】 西南交通大学 ， 电气工程（专业学位）， 2021， 硕士

【摘要】 城市轨道交通通常采用12或24脉波二极管整流供电,二极管整流结构简单、安全可靠且效率高,但能量只能单向流动,因此车辆频繁制动过程中产生的能量需要额外增加电阻、储能、能馈变流器等装置吸收。双向变流器实现了能量的双向流动,成为了取代城轨二极管整流牵引供电的方向之一。本文依托企业委托项目“地铁双向变流器”,提出一种新型的PWM双向变流器,并从调制算法和控制算法两方面展开研究。其一、数学模型分析。针对双向变流器三相两电平主电路拓扑结构,建立了abc、αβ、dq三种坐标系下的时域和s域数学模型,并对应建立了三种坐标系下的瞬时功率模型。明确了变流器各物理量间的关系,同时看到dq坐标系下可以将工频交流量转化为直流量,便于采用经典控制理论对控制器进行设计,也是后续控制器选用的坐标系。其二、调制策略研究。双向变流器容量通常都是兆瓦级的,开关频率有限,因此选用SHEPWM和CHMWPM调制算法。从两种调制算法的原理出发并借助Matlab进行低开关频率下(<1kHz)开关角的求解和谐波分析。利用三绕组移相变压器副边绕组可以抵消6k±1(k∈奇数)次谐波的特点,提出了间隔消除谐波的SHEPWM。分析对比了SHEPWM、SVPWM和SPWM的电压利用率和开关损耗,定量计算出在550Hz开关频率下SHEPWM大约可以减少17%的开关损耗。其三、控制策略研究。选用经典的电压电流双闭环及交流电网电压前馈、电感交叉解耦等控制方法,对电压环和电流环PI参数进行整定,在电流内环加入了功率前馈控制,提高了系统的动态响应速度。针对两台双向变流器并联运行,采用负载平均电流前馈控制,使得直流侧电流不均衡度仅为0.42%。最后,在7.5MW地铁双向变流器互馈实验平台上,对调制算法和控制算法进行了验证,750Hz的开关频率下,额定电流运行时,35kV侧电流谐波为4.6%<5%,变流器效率为98.7%>98%,均满足了设计要求。更多还原

【Abstract】 Urban rail transit usually uses 12 or 24 pulse diode rectification for power supply.The diode rectification structure is simple,safe,reliable and efficient,but energy can only flow in one direction.The energy generated during the frequent braking of the vehicle requires additional resistance 、energy storage device,Energy feedback device or other devices.The bidirectional converter realizes the bidirectional flow of energy and has become one of the directions to replace the diode rectifier of the urban rail traction power supply.Relying on the project "The Metro Bidirectional converter" commissioned by the enterprise,this paper conducts research on a new type of PWM bidirectional converter from two aspects:modulation algorithm and control algorithm.First,mathematical model analysis.Aiming at the three-phase two-level main circuit topology of the bidirectional converter,the time domain and s domain mathematical models under the abc,αβ,dq three coordinate systems are established,and the instantaneous power models under the abc,αβ,dq three coordinate systems are established correspondingly.The relationship between the physical quantities of the converter is clarified,and it can be seen that the power frequency AC quantity can be converted into a DC quantity under the coordinate system,which is convenient for the design of the controller using classic control theory,and it is also the coordinate system selected by the subsequent controller.Second,the modulation strategy research.The capacity of the bidirectional converter is usually megawatt power level and the switching frequency is limited,so SHEPWM and CHMWPM modulation algorithms are selected.Starting from the principles of the two modulation algorithms and using Matlab to solve the switching angle and harmonic analysis at low switching frequencies(<1kHz).The secondary winding of the three-winding phaseshifting transformer can be used to cancel the 6k±1(k is odd number)harmonic characteristics,and the SHEPWM which eliminates the harmonics at intervals is proposed.Analyzed and compared the voltage utilization and switching loss of SHEPWM,SVPWM and SPWM,and quantitatively calculated that SHEPWM can reduce the switching loss by approximately 17%at a switching frequency of 550 Hz.Third,control strategy research.The classic voltage and current double closed loop and AC grid voltage feedforward,inductance cross decoupling and other control methods are selected to adjust the voltage loop and current loop PI parameters,and power feedforward control is added to the current inner loop to improve the system’s dynamic response speed.For the parallel operation of two bidirectional converters,the load average current feedforward control is adopted,and the current imbalance on the DC side is only 0.42%.Finally,the modulation algorithm and control algorithm were verified on the 7.5MW subway bidirectional converters mutual experiment platform.Under the switching frequency of 750 Hz,the rated current is running,and the current harmonic of the 35 kV side is 4.6%<5%.The efficiency of the converter is 98.7%>98%,which meets the design requirements.更多还原