【作者】 钟诚；

【导师】 杨明皓；

【作者基本信息】 中国农业大学 ， 农业电气化与自动化， 2013， 博士

【摘要】 随着一次能源的枯竭和环境污染日益严重,以可再生能源发电技术为基础的分布式发电系统得到迅速发展。分布式发电系统中,逆变器是其核心部件。本文围绕着分布式发电系统逆变器中的实时相位测量、孤岛检测和离/并网无缝切换控制三个关键技术展开研究,主要工作和成果如下：1)提出了一种基于自适应记忆长度最小二乘法参数估计的实时相位测量方法。该方法在极坐标下建立观测方程,以电压初相角和频率作为估计参数,以整基波周期相位误差平方和最小为目标函数,并采用提出的自适应记忆长度最小二乘法计算方法,求得电网电压基波相位。仿真实验和物理实验结果表明,该方法在电网电压不对称跌落、相位突变、谐波污染和频率波动等扰动下,都能快速准确估算出电网相位,最长检测时间不超过2个工频周期。2)提出了一种基于非特征频率周期性扰动的孤岛检测方法。该方法通过注入周期性无功电流扰动,迫使公共耦合点电压频率出现相对应周期性波动,采用滑模离散傅里叶变换提取频率波动特征分量,根据该特征分量的大小进行孤岛判别。在IEEE std1547规定最恶劣负载和电网频率扰动情况的仿真实验验证了该方法的有效性。3)针对分布式发电系统的离/并网无缝切换控制策略中,状态切换过程中平滑过渡的难点问题,①提出一种基于虚拟发电机PQ外环+电容电压内环的间接控制策略,并在虚拟发电机PQ外环增加PQ功率解耦环节,使得该控制策略不仅可以实现并网到离网状态切换过程中负载电压的平滑过渡,而且对低压电网中线路阻/抗比变化具有鲁棒性；②提出了一种基于虚拟电抗的预同步方法,与常规预同步方法相比,该方法不需要增加额外的控制器,且有利于减小并网瞬间的电流暂态过程。4)在国家“十二五”863课题的支持下,参与研制了100kVA双向逆变器,主要包括了样机的功率回路设计、控制回路设计和软件系统设计,并给出了在实验室现有条件下典型运行工况的电流电压波形。更多还原

【Abstract】 On account of the problems of environmental pollution and exhaustion of energy resources, the distributed generation system based renewable energy has been developed rapidly. Converter is the key component of the distributed generation system. Real-time phasor measurement, island detection and control strategy of seamless transfer between stand-alone and grid-connected modes,are three key techniques in converter of the distributed generation system, and they are developed in this paper. The main results are as follows:1) A new real-time phase measurement method with adaptive memory length recursive least square parameter estimation is proposed in the paper.it establishes observation equation in polar coordinates, introduces initial phase and frequency as estimate parameter, takes the minimum sum of the whole period squared phase angel errors as target function, uses adaptive memory length recursive least squares method to real-time estimate parameters. The results of simulation and physical experiments show that this method can accurately and fatly estimate phasor of Grid even under the perturbation of asymmetric voltage dropping, phase mutation, phase mutation and harmonic pollution,etc. The longest tracking time is not more than2power frequency cycles.2) A new island detection method based on non-characteristic frequency disturbance is proposed in the paper. Periodic reactive current disturbance is injected to force voltage frequency of PCC (point of common coupling) to occur cyclical fluctuation, sliding discrete Fourier transform method is used to extract the non-characteristic value in the frequency fluctuation, and the characteristic value is used to distinguish island. The results of simulation show that this method can accurately distinguish island under the worst case of IEEE Std1547and frequency disturbance.3) For Realizing the smooth transition between stand-alone and grid-connected, this paper puts forward two improvements. First, an indirect control strategy of virtual synchronous generator PQ outer loop with PQ power decoupled+capacitance voltage inner loop is proposed. It not only realizes load voltage smooth transition between stand-alone and grid-connected, enhance robustness against line impedance variation in low voltage system; Second, a new prep-synchronization control method based virtual reactance is proposed. It does not need any additional synchronization controller, and is helpful to reduce current transient process at the moment of connecting grid.4) With the support of the national "twelfth five-year"863project, the author has participated in developing100kVA bidirectional energy storage converters. The mein wrok include the power circuit design, control circuit design and software system design. And, under the current conditions of the laboratory, it presents voltage and current waveforms of typical working condition.更多还原