【作者】 张胜高；

【导师】 张庆范；

【作者基本信息】 山东大学 ， 电力电子与电力传动， 2013， 硕士

【摘要】 随着全球能源危机的加重,资源问题成为制约我国经济发展的首要因素,发掘新能源,实现资源的再生利用是解决这一问题的当务之急。馈能式直流电子负载是一种能够替代传统能耗型负载的新型电力电子设备,因其具有轻便灵活、高效节能、易于安装、测试性能优良等诸多特点,广泛应用于各类直流电源产品的出厂检测和老化,它将直流电能逆变成交流电能并入电网,实现电能的回馈,达到节约资源的目的。论文主要对系统拓扑结构、工作原理和控制技术进行了分析研究,给出了一种基于移相全桥的馈能式直流电子负载的设计方案。本文首先分析了馈能式直流电子负载的工作原理,然后通过比较现有的设计方案,给出本文的系统设计思路。系统拓扑主要由DC/DC变换器和DC/AC变换器两级构成,两级均采用单相全桥变换电路。由于硬开关开关损耗大,EMI(电磁干扰)较严重,不利于实现高频化,因此,DC/DC变换器选用一种原边带箝位二极管的移相全桥ZVS(零电压开关)控制方式实现。DC/AC变换器采用单极性SPWM调制方式,在传统电压外环,电流内环的双闭环控制基本上,采用电网电压前馈与零电流跟踪控制技术结合的控制策略,使系统具有快速的瞬态响应和较高的稳定性。然后,详细介绍了馈能式直流电子负载的硬件电路及软件设计。系统的硬件电路设计主要包含主拓扑参数的设计和器件选型、驱动电路、采样检测电路、保护电路、控制及显示电路等。控制系统采用TI公司的主流DSP芯片TMS320F28335作为控制核心,Altera公司的CPLD芯片EPM3604A作为辅助逻辑控制单元。因TMS320F28335具有强大的EPWM(增强型脉宽调制器)模块、ECAP(增强型捕获)模块以及高速浮点运算功能,给软件程序的编译带来了方便,可大大缩减开发周期。软件设计部分给出整个系统控制流程,重点介绍了移相PWM的数字实现、单极性SPWM调制技术以及数字锁相并网控制技术。最后通过Matlab的Simulink模块进行建模仿真,并结合本文研制的3.5KW馈能式直流电子负载实验样机的实验结果进行分析,论证了本课题设计方案的可行性,即能较好的模拟真实负载,逆变侧输出电流近似正弦,能可靠并网,具有很小的i皆波含量,功率因数接近1.0,基本满足设计要求,系统可稳定、可靠运更多还原

【Abstract】 With the current global energy crisis, shortage of energy resources is the primary factor that hampers the development of Chinese economy. The only way to solve this problem is to explore and recycle new energy source. With the advantages like small volume, light weight, energy saving, less installation space and high test performance, DC energy-feedback electric load is widely used in testing and aging of DC power supply products. It can save and recycle electric energy by converting DC electric power into AC electric power which can be sent back to the grid. This paper mainly analyses the structure of system topology, the working principle and the controlling strategy. It also explains the design of DC feedback electric load based on the phase-shifted full bridge.Firstly, this paper analyses the working principle of DC feedback electric load and gives the method of this system by comparing various design proposals. The system topology is mainly composed of a DC/DC converter and DC/AC converter. Both the converters adopt single phase full bridge. Because hard switch has the disadvantages like huge switching loss, serious EMI and weakness in realizing high frequency DC/DC converter adopts a Zero voltage switch control method of phase-shifted full bridge with a clamp diode in the primary side. DC/AC converter adopts a method of single polarity SPWM modulation. Based on the traditional double closed-loop control method, which means that the variable of outer loop is voltage and that of inner loop is current, DC/AC converter adopts a new control technology that combines grid voltage as the feed-forward method and zero current tracking control method. By this control strategy, the system has quick transient response and is more stable.Secondly, this paper introduces the hardware circuit and software design of DC feedback electric load in detail. The hardware concludes the design process of main power circuit and the types of selection parameters, the diver circuit, the detection circuit, the control and displayer circuit. The core chip of control system is TMS320F28335which is the mainstream DSP of TI. Auxiliary logic control unit uses EPM3604A which is the CPLD chip of Altera. TMS320F28335has a strong enhanced PWM, enhanced CAP module and high-speed floating-point arithmetic functions, with that, we can compile software program more convinces and reduce the development cycle. The design of software gives the whole system control process, it focus on the digital implementation of phase-shifted PWM, single polarity SPWM and PLL technology of grid-connected.Finally, it gives the result of simulation model by the Simulink module of Matlab. Then it analyses the experimental waveforms based on the experimental prototype of a3.5KW DC feedback electric load. It demonstrates the efficiency of design. The DC feedback electric load can simulate the real load. Its output current is approximately sinusoidal, has small harmonic content and can connect to the grid reliably. The power factor is close to1.0that basically meets the requirement of design and the system can operate stably and reliably.更多还原