The DC microgrid is connected to the AC utility by parallel bidirectional power converters （BPCs） to import/export large power, whose control directly affects the performance of the grid-connected DC microgrid. Much...The DC microgrid is connected to the AC utility by parallel bidirectional power converters （BPCs） to import/export large power, whose control directly affects the performance of the grid-connected DC microgrid. Much work has focused on the hierarchical control of the DC, AC, and hybrid microgrids, but little has considered the hierarchical control of multiple parallel BPCs that directly connect the DC microgrid to the AC utility. In this paper, we propose a hierarchical control for parallel BPCs of a grid-connected DC mierogrid. To suppress the potential zero-sequence circulating cm-cent in the AC side among the parallel BPCs and realize feedback linearization of the voltage control, a d-q-O control scheme instead of a conventional d-q control scheme is proposed in the inner current loop, and the square of the DC voltage is adopted in the inner voltage loop. DC side droop control is applied to realize DC current sharing among multiple BPCs at the primary control level, and this induces DC bus voltage deviation. The quantified relationship between the current sharing error and DC voltage deviation is derived, indicating that there is a trade-off between the DC voltage deviation and current sharing error. To eliminate the current sharing error and DC voltage deviation simultaneously, slope-adjusting and voltage-shifting approaches are adopted at the secondary control level. The pro- posed tertiary control realizes precise active and reactive power exchange through parallel BPCs for economical operation. The proposed hierarchical control is applied for parallel BPCs of a grid-connected DC microgrid and can operate coordinately with the control for controllable/uncontrollable distributional generation. The effectiveness of the proposed control method is verified by corresponding simulation tests based on Matlab/Simulink, and the performance of the hierarchical control is evaluated for prac- tical applications.展开更多
目的评估安陆德免荷一号矫形器对内侧膝骨关节炎患者活动、疼痛、膝关节功能、日常生活以及生活质量的影响。方法 36例骨关节炎患者。按平均、计算机随机、双盲方法将患者分为A、B、C三组。A组以安陆德免荷一号矫形器加非甾体抗炎药(non...目的评估安陆德免荷一号矫形器对内侧膝骨关节炎患者活动、疼痛、膝关节功能、日常生活以及生活质量的影响。方法 36例骨关节炎患者。按平均、计算机随机、双盲方法将患者分为A、B、C三组。A组以安陆德免荷一号矫形器加非甾体抗炎药(non-steroidal antiinflammatory drugs,NSAIDs)美洛昔康联合治疗,B组单用安陆德免荷一号矫形器治疗,C组单用美洛昔康治疗,每组12例。从入组起,每3周门诊随访,通过Lysholm膝关节评分表、KOOS评分表、SF-12生活质量评价量表、过去24 h VAS疼痛评分表以及Tegner活动积分表对患者进行评估,总疗程为12周。结果 (1)治疗后12周,A组患者Lysholm膝关节评分:85.64±4.74,KOOS评分症状:73.17±8.29、疼痛:70.33±5.96、日常生活:77.08±4.32、体育及娱乐:81.67±5.77、生活质量:80.58±5.76,SF-12生活质量评分:19.08±1.88,过去24 h VAS疼痛评分1.25±0.754,Tegner活动积分:7.45±1.08,各项评分较开始改善显著,差异有统计学意义(P<0.05)。B组患者Lysholm膝关节评分:85.33±4.68,KOOS评分症状:71.33±10.63、疼痛:68.83±5.01、日常生活:75.92±5.18、体育及娱乐:80.00±7.07、生活质量:78.17±6.63,SF-12生活质量评分:18.83±2.52,过去24 h VAS疼痛评分1.4±0.809,Tegner活动积分7.55±1.31,各项评分较开始改善显著,差异有统计学意义(P<0.05)。C组患者Lysholm膝关节评分:76.17±5.557,KOOS评分症状:60.92±7.75、疼痛:57.67±8.69、日常生活:68.17±4.61、体育及娱乐:70.00±8.53、生活质量:69.33±8.24,SF-12生活质量评分:14.18±1.81,过去24 h VAS疼痛评分2.2±0.669,Tegner活动积分:4.36±0.91,各项评分较开始改善显著,差异有统计学意义(P<0.05)。B组评分与A组差异无统计学意义(P≥0.05),疗效较C组显著,差异有统计学意义(P<0.05)。(2)从整体趋势而言:C组患者症状好转快,最终疗效不如A、B组。B组起效慢,最终疗效比C组好。A组起效快,最终疗效较C组好,但与B组差异展开更多
基金Project supported by the National Natural Science Foundation of China （No. 51377142）, the National High-Tech R＆D Program （863） of China （No. 2014AA052001）, the Zhejiang Provincial Natural Science Foundation of China （No. LY16E070002）, and the Zhejiang Province Key R＆D Project （No. 2017C01039）
文摘The DC microgrid is connected to the AC utility by parallel bidirectional power converters （BPCs） to import/export large power, whose control directly affects the performance of the grid-connected DC microgrid. Much work has focused on the hierarchical control of the DC, AC, and hybrid microgrids, but little has considered the hierarchical control of multiple parallel BPCs that directly connect the DC microgrid to the AC utility. In this paper, we propose a hierarchical control for parallel BPCs of a grid-connected DC mierogrid. To suppress the potential zero-sequence circulating cm-cent in the AC side among the parallel BPCs and realize feedback linearization of the voltage control, a d-q-O control scheme instead of a conventional d-q control scheme is proposed in the inner current loop, and the square of the DC voltage is adopted in the inner voltage loop. DC side droop control is applied to realize DC current sharing among multiple BPCs at the primary control level, and this induces DC bus voltage deviation. The quantified relationship between the current sharing error and DC voltage deviation is derived, indicating that there is a trade-off between the DC voltage deviation and current sharing error. To eliminate the current sharing error and DC voltage deviation simultaneously, slope-adjusting and voltage-shifting approaches are adopted at the secondary control level. The pro- posed tertiary control realizes precise active and reactive power exchange through parallel BPCs for economical operation. The proposed hierarchical control is applied for parallel BPCs of a grid-connected DC microgrid and can operate coordinately with the control for controllable/uncontrollable distributional generation. The effectiveness of the proposed control method is verified by corresponding simulation tests based on Matlab/Simulink, and the performance of the hierarchical control is evaluated for prac- tical applications.
文摘目的评估安陆德免荷一号矫形器对内侧膝骨关节炎患者活动、疼痛、膝关节功能、日常生活以及生活质量的影响。方法 36例骨关节炎患者。按平均、计算机随机、双盲方法将患者分为A、B、C三组。A组以安陆德免荷一号矫形器加非甾体抗炎药(non-steroidal antiinflammatory drugs,NSAIDs)美洛昔康联合治疗,B组单用安陆德免荷一号矫形器治疗,C组单用美洛昔康治疗,每组12例。从入组起,每3周门诊随访,通过Lysholm膝关节评分表、KOOS评分表、SF-12生活质量评价量表、过去24 h VAS疼痛评分表以及Tegner活动积分表对患者进行评估,总疗程为12周。结果 (1)治疗后12周,A组患者Lysholm膝关节评分:85.64±4.74,KOOS评分症状:73.17±8.29、疼痛:70.33±5.96、日常生活:77.08±4.32、体育及娱乐:81.67±5.77、生活质量:80.58±5.76,SF-12生活质量评分:19.08±1.88,过去24 h VAS疼痛评分1.25±0.754,Tegner活动积分:7.45±1.08,各项评分较开始改善显著,差异有统计学意义(P<0.05)。B组患者Lysholm膝关节评分:85.33±4.68,KOOS评分症状:71.33±10.63、疼痛:68.83±5.01、日常生活:75.92±5.18、体育及娱乐:80.00±7.07、生活质量:78.17±6.63,SF-12生活质量评分:18.83±2.52,过去24 h VAS疼痛评分1.4±0.809,Tegner活动积分7.55±1.31,各项评分较开始改善显著,差异有统计学意义(P<0.05)。C组患者Lysholm膝关节评分:76.17±5.557,KOOS评分症状:60.92±7.75、疼痛:57.67±8.69、日常生活:68.17±4.61、体育及娱乐:70.00±8.53、生活质量:69.33±8.24,SF-12生活质量评分:14.18±1.81,过去24 h VAS疼痛评分2.2±0.669,Tegner活动积分:4.36±0.91,各项评分较开始改善显著,差异有统计学意义(P<0.05)。B组评分与A组差异无统计学意义(P≥0.05),疗效较C组显著,差异有统计学意义(P<0.05)。(2)从整体趋势而言:C组患者症状好转快,最终疗效不如A、B组。B组起效慢,最终疗效比C组好。A组起效快,最终疗效较C组好,但与B组差异
