AC-AC Based Active Electric Spring（AC-AES） And Demand Side Voltage Control

To deal with the voltage fluctuation of distribution network caused by a large number of distributed energy access,Electric Spring（ES）,as a power quality optimization device,adaptively adjusts the power consumption of load,so as to realize the demand side voltage stablity control.However,the traditional ES is connected in series with the non-critical load to form a smart load（SL）,and then connected in parallel with the Critical Load（CL）,realizing the protection of critical load while Non-Critical Load（NCL）operates at abnormal voltage.With the higher and higher requirements of power quality and the greater demand for custom power technology,it is more difficult to divide critical loads and non-critical loads,or it is impossible to divide them.Considering the above characteristics,the existing ES regulates the load voltage in a passive way under the practical condition.Firstly,in order to solve the shortcomings of traditional Electric Spring,this paper proposes a concept of "Active Electric Spring".Different from the traditional Electric Spring,the Active Electric Spring does not need to divide the Critical Load and Non-Critical Load.Active Electric Spring changes the way of accessing the demand side,which improves the initiative of load regulation and enhances the voltage regulation ability of the device.Secondly,an Active Electric Spring based on direct AC-AC convertion（AC-AES）is proposed in this paper.The closed-loop control strategy of AC-AES does not need to adopt PLL phase-locked loop,so the device is very easy to implement in engineering.AC-AES can also output bipolar type voltage.The modulation principle and working principle of AC-AES topology are analyzed,and the filter capacitor and filter inductance parameters of AC-AES topology are optimized.Finally,On the basis of above analysis,two regulation modes of AC-AES are proposed,which are load power regulation mode and stable load voltage mode.Through these two working modes,AC-AES realizes the demand side response,which improves the power quality on the demand side and reduces the construction investment of energy storage system.The load power regulation mode uses the characteristics of the Voltage dependent load,and change the voltage across the load to realize the Energy Management on the demand side.Using Matlab / Simulink simulation platform,the ability of AC-AES to regulate load power is verified by building AC-AES simulation model in load power regulation mode;Stable load voltage mode ensures the stability of load voltage when the voltage of electrical network is fluctuated by providing timely voltage compensation for load voltage.The Closed-loop Control System matching the function of stable load voltage mode is designed.The AC-AES prototype and experimental platform with rated power of 1k W are built by using FPGA controller and IGBT power switch IKW75N60 T,which verifies the ability of AC-AES to stabilize load voltage.