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Research on Development of Phtovoltaic Generating System without Using the Phase Information of Power Network

不利用电网相位信息的光伏发电系统开发研究

基本信息

批准号：
06650329
负责人：
YAMADA Eiji
金额：
$ 1.34万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Inverters which are connected to electrical power network operate according to informations of it like as voltages, phases and so on. Photovoltaic power system needs same informations when it is interconnecte d to electrical power network. If exact informations can not be received, large current may flow and transmission power loss may increase. But it is very difficult to detect exact informations because of inductances of electrical power network, distortion of voltage waveform and phase delay due to electrical machines connected to it. These unexpected informations sometimes make the total system unstable.Therefore, using inpedances of the photovoltaic system and the power electrical network, and output current from photovoltaic system, we estimated the power source by minimal order observer. Then we developed novel photovoltaic system. From simulation results of noval system, we recognized that phase of electrical power network could be estimated rapidly even if phases were differe … More nt from detected values and estimated one. Also if source phases change like step function, novel system can follow it. We concluded that novel system could operate stable in case where impedances of transmission line were long as photovoltaic system was apert from electrical power network and distortion of power waveform as large capacity converters exist near it.Until now maximum power following control of photovoltaic generator has been attended by purturbating small value of photovoltaic voltage, and comparating its value to before and after ones. Because system is operated by purturvation of voltage all times, generating power pulsates. Besides, this method has defect that response is slow when illuminance changes widely, though maximum power point can be found.In this paper we have developed novel method that maximum power can be gotten using three points of it ; actuating point, before ones and after. This metho d is one that power characteristic is approximated by second order function and maximum power point can be gotten by only one calculation. So pulsating number of terminal voltage can be decreased.From the results of simulatior which are composed of above mentioned method and source voltage phase estimation one by minimal order observer, it became evident that novel system can follow to maximum power point rapidly and has small pulsation in comparison with normal system. Less

与电网相连的逆变器根据电网的电压、相位等信息进行工作。光伏发电系统在接入电网时需要相同的信息。如果不能接收到准确的信息，可能会产生较大的电流，增加传输功率损耗。但是由于电网的电感、电压波形的畸变以及与之相连的电机的相位延迟等因素，使得准确的信息检测非常困难。这些意想不到的信息有时会使整个系统不稳定。因此，利用光伏系统与电网的独立性以及光伏系统的输出电流，采用最小阶观测器对电源进行估计。然后我们开发了新型光伏系统。从系统的仿真结果中，我们认识到即使相位不同，也可以快速估计出电网的相位。如果源相位像阶跃函数一样变化，新系统也可以跟随它。认为在输电线路阻抗较长的情况下，光伏系统远离电网，在输电线路附近存在大容量变流器造成电力波形畸变的情况下，新型系统可以稳定运行。到目前为止，光伏发电机组的最大功率跟随控制一直是通过获取光伏电压的小值，并将其与前后电压进行比较。由于系统一直在电压变化的作用下运行，产生功率脉动。此外，该方法的缺点是当照度变化较大时，虽然可以找到最大功率点，但响应速度较慢。本文提出了一种新颖的方法，利用它的三个点来获得最大功率；致动点，1之前和1之后。该方法是一种用二阶函数逼近功率特性，一次计算即可得到最大功率点的方法。这样可以减小端电压的脉动数。由上述方法和最小阶观测器的源电压相位估计组成的仿真结果表明，与普通系统相比，新系统可以快速跟踪到最大功率点，并且脉动较小。少