时间：2022-07-07 04:44:33
1. Grid Tied PWM Converter
2. The controller of voltage/current of grid tied convertor
The commonly used control structure of PWM converter has series structure with DC link voltage control on the top and current control on the bottom.
2.1 The voltage controller of grid tied converter
Compared to current controller， voltage controller has bigger control cycle， since the speed of response of voltage controller is slower than that of current controller.
If the input power from power supply is bigger than the output power that is consumed， DC link voltage is increased， In the opposite case， as the DC link voltage is decreased， DC link voltage can be controlled by controlling input power.
Thus， this can be seen as controlling DC link voltage by controlling valid power current（q axid current）. The figure below 2 indicates diagram of current controller with IP controller.
Fig. 1. Diagram of voltage controller
2.2 The current controller of grid tied converter
The Current controller to control q-axid （active component current）current that controls fixed power of DC link voltage and d-axid（reactive component current）current that maintains power factor as 1 is improved by applying IP current controller.
Fig. 2. Diagram of Current controller
The gain of IP current controller can be induced like below.
（14）
（15）
（16）
3. Simulation of 3 phase PWM converter
Fig. 3. 3 phase AC/DC PWM converter simulation circuit
Before producing 3phase AC/DC PWM converter， it has been simulated like fig. 3.
The simulation is composed by using PSIM， simulation code has formed with DLL block in order to be directly recognized by hardware controller.
Also in order to check the characteristics of load ， the response property is checked by changing the size of load every 0.3second.
Fig. 4.The simulated wave form of Va phase and Theta
Fig. 5.The wave form for real of Va phase and reference of Va phase
The calculated temperature increase of inductor with average current and average loss under different elevater load of 100%，87.5%，75%，62.5%，50% is compared with actually measured temperature increase of inductor.
Table. 1. Comparison of slope between measured value and calculated value by each average power loss
Table. 2. Comparison of slope between measured value and calculated value by each average current
Table. 3. Condition of operation
4. Conclusion
The thermal resistance from the rated load is confirmed by actually measuring the prototype.
By inducing the confirmed inductor’s thermal resistance as loss， it is possible to develop a small inductor， optimized for grid tied convertor. Also the on-time observation of inductor’s temperature rise enables tracking the differences of the inductor thermal resistance. By utilizing this， inductor’s lifetime， failure and the system failure of renewable energy grid tied convertor can be checked.
A exceed current and exceed voltage has been used to check grid tied convertor’s failure until inductor temperature function can also determine the failure of system， which can enhance the reliability of grid tied converter.
Acknowledgement
The present research has been conducted by the Research Grant of Seoil University in 2013.
References
[1] ] Su-bin Han， “Status and Using of CAD program for Transformer / Inductor Design”， KIPE
Magazine， pp.31-35， 2006. April.
[2] Marlin O. Thurston， “Transformer and Inductor Design Handbook“， Marcel Dekker， Inc.
[3] Ansoft Korea Homepage，
"http：//www.ansoft.co.kr/html/pro/pe.php"