【作者】 白建国；

【导师】 白志范；

【作者基本信息】 吉林大学 ， 材料加工工程， 2004， 硕士

【摘要】 逆变焊接电源具有体积小，、重量轻、高效节能、动态响应快等许多优点，被焊接界公认为最有发展前途的焊接电源。随着电力电子技术和各种先进控制方法的发展，和功率器件IGBT的出现及其性能的不断完善，逆变弧焊电源的前景将更加光明。为了减小弧焊电源的体积，可以通过提高其频率的方法来实现。同时弧焊电源频率的进一步提高会带来很多的优良特性。但是传统的PWM控制的弧焊电源中，开关器件均是强迫开关过程，因而存在开通和关断损耗大、感性关断、容性开通、二极管方向恢复等一系列问题。开关损耗随逆变频率的提高而增加，很难进一步高频化。软开关PWM技术能较好地解决传统PWM技术中的问题，越来越成为焊接界所关注的焦点之一。同时传统的焊接逆变电源均为二极管整流、大电容滤波，从而造成输入电流和电压相位相差很大，并且电流畸变很大。这样不仅功率因数很低，而且输入电流中谐波的含量相当高，从而严重污染了电网。现在人们以来时意识到这一点，并开始制定一系列规定来限制接入电网的设备的谐波含量。为了抑制谐波、提高功率因数，人们引入了功率因数校正技术。同时为了减小体积，大多采用有源功率因数校正技术。三相有源功率因数校正技术大多采用boost变换器作为主电路，其输出电压一般为760-800V DC，有时甚至高达1000V，这就要求后级开关管的耐压要高，从而导致电源成本的大幅度提高。而三电平变换器中，管子承受的电压为输入电压的一半，因此非常合适作为三相功率因数校正的后级电路。同时为了减小开关损耗，将软开关技术引入到三电平变换器，从而产生了一种新颖的软开关PWM变换器——三电平软开关变换器。三电平软开关变换器分为ZVS-PWM三电平变换器和ZVZCS-PWM三电平变换器。考虑到ZVS-PWM三电平存在以下缺点：①超前臂是利用输出滤波电感和漏感的能量实现ZVS，比较容易；但后桥只能利用漏感的能量来实现ZVS，由于漏感一般较小，在负载较轻时其能量不足以实现滞后管的ZVS，如够将漏感做得很大，将会带来较大的占空比丢失；②在零状态时，一次侧不给负载提供能量，但一次侧有环流存在，在开关管和变压器一次绕组中产生通态损耗，影响了变换效率的提高。本文采用ZVZCS-PWM三电平变换器作为弧焊电源的主电路。本文详细介绍了ZVZCS-PWM三电平变换器的工作原理，给出了其实现软开关的条件及其参数设计的理论依据。在设计电路前用电路仿真软件Pspice 9.2对主电路进行了仿真，在理论上验证了方案的可行性。同时利用控制理论对系统进行分析，推导出该电源系统的传递函数模型。为了使电压、<WP=68>电流扰动对系统输出影响减小，合理选择了调节器及校正环节，通过选择合适的参数，得到了一个具有较高稳定性、很好动态性能和较高稳定精度的控制系统。并用MATLAB对控制系统进行了仿真，验证了设计的正确性。最后根据参数计算和理论分析，设计了一台最大输出电流为120A的逆变弧焊电源模拟机，其输出电流范围在20A-120A之间，空载电压载65V-70V之间.。实验证明对ZVZCS-PWM三电平变换器的原理分析、参数计算和仿真模拟是完全正确的。该变换器的前桥实现了零电压开关、后桥实现了零电流开关，同时管子承受的压降值为为输入电压值的一半。本论文采用EXB841设计了开关管IGBT的驱动电路，开关管开通时的正相驱动电压为15V，反向截止电压为-5V，同时采用外围电路设计了过流时的保护电路，当IGBT过流时，EXB841将输出低电平，从而关断开关管。同时为了避免电网对控制电路的的干扰，采用双管正激变换器设计了一辅助开关电源，为电路中的各种芯片供电，从而很好的实现了电网和控制电路的严格隔离。避免了电网对控制电路的干扰，实验证明效果很好。本文对整个系统的可靠性和抗干扰能力进行了理论分析和实践，采取减小干扰源，切断传播途径，屏蔽被干扰源的方法增强系统的可靠性。在整个系统的布局上，使强干扰源远离对干扰敏感的器件，器件之间的连线用屏蔽线，IGBT的驱动线用绞合线并且尽可能的短等，在设计PCB时，全方位考虑了EMI问题，采取措施使控制板中的各种信号线尽可能的互不干扰，使整个系统的驱动脉冲和工作时序按计划进行。总之，ZVZCS-PWM三电平变换器不仅有软开关PWM的各种优点，而且开关管承受的电压值为输入电压的一半，特别适用于采用了有源功率因数校正技术或者输入电压很高的场合。三电平技术的发展，必将促进绿色环保电源的飞速发展。更多还原

【Abstract】 Arc welding inverters have many good qualities, such as small volume、lightness、 high efficiency and rapid dynamic response and are recognized as the most prospective welding power supply in the welding field . With the improvement of power electronics technology, especially the emergence of the power element IGBT and the consummation in its consummation, in its performance, the arc welding inverter’s future will be more beautiful. In order to decrease volume of Arc welding power supply, we can fulfill it through increasing frequency of it. And the further improvement in arc welding power supply’s inverter frequency can bring more good qualities, But in conventional PWM control arc welding power supply, switching elements are forced to be on or off, so there exit many problems, such as great loss, inductive switch-off, capacitive switch-on and diode’s reverse current. The switch loss increases with the improvement of inverter’s frequency, so it is hard to improve inverter frequency further. Soft switching PWM technique can resolve this problem existing in conventional PWM technique, so it becomes one focus of welding field more and more. Conventional input current of Arc-welding is rectified by diodes, and smoothed by big capacitors. So this causes the differences between input voltage and input current to be very large, and the distortion of the current is large too .The results of which are as follows: first, power factor is low; second, harmonic current of input current is so high; at last it pollutes electrified wire netting. Now people begin to realize this point, and start to make some rules to limit the harmonic current of the equipment connected to electrified wire netting .In order to restrain harmonic current and enhance power factor, power factor correction is introduced. At the same time, in order to lighten volume, active power factor correction is the first choice. Most of three phase active power correction utilizes “boost” converter to be its main circuit, and its output voltage is 760-800V, sometimes even to 1000V, which requires the rear switch to have high endure voltage, the result of which is the costing of the equipment becomes so high .In three-level converter, endure voltage of the switch is half of input voltage, so it fits to be the rear circuit of the three phase power factor correction. And in order to lighten switching loss, soft switching is introduced to <WP=70>thee level converter. So a novel soft-switching PWM converter emerges. Soft switching PWM three level converters can be classified as ZVS three level converter and ZVZCS three level converter. ZVS three level converter has following drawbacks:①forelegs can fulfill its ZVS very easy by the energy in the filter and leakage inductor , but the lag legs can only fulfill its ZVS by the energy in the leakage inductor , when the load current is not enough ,the energy is too small to fulfill ZVS of lag legs , if we make the leakage inductor too large , big loss of duty cycle will emerge . ②When it is at the state of zero , primary don’t conduct energy to load , but there exits loop current ,which cause conduct loss in switch and primary of transformer , so limits the efficiency. For this reason, I choose ZVZCS-PWM three level converter to be Arc-welding’ main circuit. This paper analyze the principle of ZVZCS-PWM three level converters in detail, gives out the condition of soft switching and solution to design the parameter. Before designing circuit, I simulate it by use of software Pspice9.2, and demonstrate the feasibility in theory. At the same time, this paper uses control theory to analyze the system and gets the system transfer function model. To reduce the influence of voltage and current disturbance on the output, the regulator and corrector are reasonably selected, By selecting suitable parameters, a control system with high stability, good dynamic characteristic and high static accuracy is got. Following this, this paper simulates the control system by use of MATLAB, and demonstrates the correctness of the de更多还原