The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-...The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-wire system.However,as the zero-sequence voltage is expressed in trigonometric form,traditional control methods involve many complicated operations,such as the square-root,trigonometric operations,and inverse tangent operations.To simplify cluster voltage balancing control,this paper converts the zero-sequence voltage to the dq frame in a DC representation by introducing a virtually orthogonal variable,and the DC components of the zero-sequence voltage in the dq frame are regulated linearly by proportional integral regulators,rather than being calculated from uneven active powers in traditional controls.This removes all complicated operations.Finally,this paper presents simulation and experimental results for a 400 V±7.5 kvar star-connected STATCOM,in balanced and unbalanced scenarios,thereby verifying the effectiveness of the proposed control.展开更多
Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(...Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(SVPWM)is a more popular scheme,but conventional 4L SVPWM cannot achieve the voltage balancing control of DC-link capacitors,is complex to implement,and requires costly computation.A hybrid modulation method with capacitor voltage-balancing control for 4L NPC converters is proposed.The proposed method is achieved using three-level(3L)SVPWM and two-level(2L)carrier-based pulse-width modulation(CPWM)based on the concept of"4L=3L+2L".Thus,it can be easily implemented on a digital chip because the modulation process is nearly identical to that of 3L SVPWM without the more cumbersome 4L SVPWM algorithm.Meanwhile,any proven optimization scheme of 3L SVPWM can be directly applied to the proposed method to further improve performance.Simulation and experimental results for a 4L active NPC converter demonstrate the effectiveness of the proposed method.展开更多
In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalab...In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalability;MMCs are extensively used in high-voltage and high-power applications.Based on their unique advantages,MMCs have attracted increasing attention from academic circles over the past years.Several studies have focused on different aspects of MMCs,including submodule topologies,modeling schemes,modulation strategies,control schemes for voltage balancing and circulating currents,fault diagnoses,and fault-tolerant control strategies.To summarize the current research status of MMCs,all the aforementioned research issues with representative research approaches,results and characteristics are systematically overviewed.In the final section,the current research status of MMCs and their future trends are emphasized.展开更多
基金supported by National Key R&D Program of China(No.2021YFB2401100)the Science and Technology Project of State Grid Corporation of China(No.5211DS22002C).
文摘The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-wire system.However,as the zero-sequence voltage is expressed in trigonometric form,traditional control methods involve many complicated operations,such as the square-root,trigonometric operations,and inverse tangent operations.To simplify cluster voltage balancing control,this paper converts the zero-sequence voltage to the dq frame in a DC representation by introducing a virtually orthogonal variable,and the DC components of the zero-sequence voltage in the dq frame are regulated linearly by proportional integral regulators,rather than being calculated from uneven active powers in traditional controls.This removes all complicated operations.Finally,this paper presents simulation and experimental results for a 400 V±7.5 kvar star-connected STATCOM,in balanced and unbalanced scenarios,thereby verifying the effectiveness of the proposed control.
基金Supported in part by the Guangdong Innovative Program on New Power System Technology under Grant 1688483408285in part by the National Natural Science Foundation of China under Grant 52207221in part by Wuhan Science and Technology Project under Grant 2023010201010071.
文摘Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(SVPWM)is a more popular scheme,but conventional 4L SVPWM cannot achieve the voltage balancing control of DC-link capacitors,is complex to implement,and requires costly computation.A hybrid modulation method with capacitor voltage-balancing control for 4L NPC converters is proposed.The proposed method is achieved using three-level(3L)SVPWM and two-level(2L)carrier-based pulse-width modulation(CPWM)based on the concept of"4L=3L+2L".Thus,it can be easily implemented on a digital chip because the modulation process is nearly identical to that of 3L SVPWM without the more cumbersome 4L SVPWM algorithm.Meanwhile,any proven optimization scheme of 3L SVPWM can be directly applied to the proposed method to further improve performance.Simulation and experimental results for a 4L active NPC converter demonstrate the effectiveness of the proposed method.
基金Supported by the Science and Technology Program of State Grid Corporation of China(5100-201999330A-0-0-00)。
文摘In the present scenario,modular multilevel converters(MMCs)are considered to be one of the most promising and effective topologies in the family of high-power converters because of their modular design and good scalability;MMCs are extensively used in high-voltage and high-power applications.Based on their unique advantages,MMCs have attracted increasing attention from academic circles over the past years.Several studies have focused on different aspects of MMCs,including submodule topologies,modeling schemes,modulation strategies,control schemes for voltage balancing and circulating currents,fault diagnoses,and fault-tolerant control strategies.To summarize the current research status of MMCs,all the aforementioned research issues with representative research approaches,results and characteristics are systematically overviewed.In the final section,the current research status of MMCs and their future trends are emphasized.
