We present power quality enhancement methods for smart microgrids that employ the con-cept of decentralized control based on state feedback and droop control. Existing power systems suffer from many problems. For example, large-scale power plants are located far away from con-sumers. The increasing usage of renewable energy sources leads to severe voltage distortion and voltage fluctuation. Hence, power conditioning equipment such as power filters and static syn-chronous compensators (STATCOMs) are needed to assure power quality and generate electricity from renewable energy sources efficiently. However, when power electronic converters are used in parallel in microgrids, circulating currents can flow across the converters, leading to bad effects in power systems or microgrids. We propose two methods for power quality enhancement by reduc-ing circulating currents. One is to design DC-DC converter voltage regulation by using state feed-back control. Another method is to reduce circulating current generated along buses by using an advanced Phase Shift Pulse Width Modulation (PSPWM) DC-DC converter between High Voltage DC Bus (HVDC) and Low Voltage DC Bus (LVDC). To validate the proposed methods, we de-velop a microgrid simulator using MATLAB/Simulink and evaluate the benefits of our scheme using this simulator. As a result, we demonstrate, through the two simulation results, the power quality in DC microgrids is improved when the power is transferred. ⓒ 2014 DGIST
Table Of Contents
Ⅰ. INTRODUCTION 1 -- Ⅱ. BACKGROUND 5 -- 2.1 Smart microgrids – decentralized control on DC microgrids 5 -- 2.1.1 Microgrid simulator - decentralized control on DC microgrids 5 -- 2.1.2 Power converter – PSPWM DC-DC converter 5 -- 2.2 State feedback and droop control 6 -- 2.2.1 State feedback 6 -- 2.2.2 Droop control method 6 -- 2.3 Circulation current 6 -- 2.4 Related work 7 -- Ⅲ. SYSTEM CONFIGURATION 8 - 14 -- 3.1 DC microgrids with HVDC bus and LVDC bus 9 -- 3.2 DC-DC boost 10 -- 3.3 Isolated bidirectional DC-DC converter for galvanic isolation 14 -- IV. PROPOSED METHODS 15 -- 4.1 State feedback control for voltage regulation 15 -- 4.2 Exploiting advanced PSPWM DC-DC converter in a DC microgrid 19 -- V. PERFORMANCE EVALUATION 22 -- 5.1 Converters output voltage regulation with state feedback control 22 -- 5.2 Reducing circulating current and voltage stress 25 -- VI. CONCLUSION AND FUTURE WORK 28 -- REFERENCES 30
