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

逆变器接入电网后，根据电网的电压、相位等信息运行。光伏发电系统接入电网需要同样的信息。如果不能接收到准确的信息，可能会产生大电流，增加输电功率损耗。但由于电网的电感、电压波形的失真以及与之相连的电机造成的相位延迟，使得准确的信息检测变得非常困难。这些意外的信息有时会使整个系统变得不稳定，因此，利用光伏系统和电网的阻抗，以及光伏系统的输出电流，利用最小二阶观测器估计电源。然后，我们开发了新型的光伏发电系统。从NOVAL系统的仿真结果可以看出，即使在不同的…情况下，也可以快速地估计电网的相位来自检测值和估计值的更多NT。如果源相位按阶跃函数变化，则新的系统可以跟随它。结果表明，在输电线路阻抗较大的情况下，由于光伏系统受到电网的干扰，且附近存在大容量变流器，系统能够稳定运行。在此之前，对光伏发电机的最大功率跟踪控制一直是通过扰动光伏电压的小值，并将其前后的值进行比较。因为系统在任何时候都是通过电压净化来运行的，所以发电是脉动的。此外，该方法还存在光照度变化较大时响应速度慢的缺点，虽然可以找到最大功率点，但本文提出了一种新的方法，即利用光照度变化较大的三个点，即执行点、前一点和后点来获得最大功率。该方法是用二次函数逼近功率特性，只需一次计算即可得到最大功率点。仿真结果表明，该方法能快速跟踪到最大功率点，且与常规系统相比，脉动小。较少

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