【作者】 陈方亮；

【导师】 徐至新；

【作者基本信息】 华中科技大学 ， 电力电子与电力传动， 2005， 硕士

【摘要】 调频式串联谐振交流耐压试验系统采用变频变压电源实现试验回路的谐振升压,具有电源设备容量小、交流等效性好等优点,是目前对高电压等级电容性被试品进行耐压试验行之有效的方法。调频式串联谐振耐压试验系统的核心是自动调频PWM 逆变电源,本文对基于DSP 数字控制器的调频式串联谐振交流耐压试验系统自动调频PWM 逆变电源进行了研究。本文建立了串联谐振耐压试验系统的数学模型。通过分析谐振回路传递函数,指出系统是一个阻尼比很小的欠阻尼二阶振荡环节,其动态性能较差。通过变参数平均值数字PI 控制方法实现被试品电压的调节控制,保证了电压的无超调。系统的频率特性表明被试品电压相位是频率的非线性函数,采用小偏差法对相频特性进行线性化,得到了相频特性在谐振频率点的增量化线性模型。根据系统谐振工作时试验回路输入电压和被试品电压相位的关系,提出采用检测被试品电压与输入电压相位差的方法确定试验回路谐振状态。基于系统线性化相位模型,提出了一种利用DFT 运算求取相位及设计谐振频率跟踪控制器的方法,并通过仿真验证了控制器的控制效果。针对单相全桥PWM 逆变器电压波形的调制方式开展了研究,指出当前广为使用的单脉冲RPWM 调制方式稳态时在被试品上产生的电压波形满足试验规程要求,但低次谐波容易在试验回路上产生谐振导致波形畸变,不利于谐振频率的跟踪控制。提出采用分段同步单极性SPWM 方法进行调频电源的波形调制,保证了电源大范围变频调压过程中低次谐波少,波形质量高。对单极性调制的两种开关模式进行了分析,说明在稳态谐振工作时采用简化开关模式能避免死区效应,具有理想单极性SPWM 的效果,且开关损耗小。设计了一套基于TMS320F240 DSP 数字控制器的串联谐振耐压试验系统模型样机。样机实验结果表明,采用分段同步单极性SPWM 调制方式实现的试验系统自动调频电源输出电压正负半波对称性好,相位稳定,波形正弦度高; 验证了利用DFT 计算相位实现谐振频率自动跟踪控制的方法具有稳定性好、精度较高的特点。更多还原

【Abstract】 For high voltage(HV) on-site testing, the AC frequency-tuned series resonant test system(ACRF system) have been recognized to be the most cost-effective and only practicable solution because of the advantages of the ACRF system: a very good weight-to-test power ratio and very low power demands. The ACRF system is tuned into resonance with the test object by a voltage of variable frequency supplied by a variable frequency PWM inverter. Consequently, the variable frequency supply is the heart of a ACRF system. A variable frequency SPWM inverter for ACRF system is described in this dissertation. The analysis of the transfer function of the ACRF system indicates that this system is a typical second-order oscillation section with small damping ratio and the phase-frequency characteristic is non-linear function of frequency. By linearizing the phase-frequency characteristic around the operating point, the linearized characteristic of the system can be easily obtained. Based on the system modeling and simulation, two kinds of PWM modulation methods used in single-phase bridge are analyzed. As a result, a subsection synchronization unipolar SPWM modulation strategy and a average voltage PI control scheme is applied in DSP controller for achieving a wide frequency range of output voltage. Based on DFT algorithm, the phase of voltage in the test object is gained and the digital controller is presented for tracing the system resonant frequency. A prototype of the ACRF test system is developed, which uses DSP TMS320F240 as the core of control system. Experimental results demonstrate that the output voltage of the system based on subsection synchronization unipolar SPWM modulation and DFT algorithm have high steady-state precision and symmetrical waveform, furthermore, the phase and frequency of the voltage is both precise and stable.更多还原