为实现多变风况下直驱永磁风力发电系统的稳定、高效运行,提出一种模型预测电流控制MPCC(model predictive current control)与分数阶比例-积分-微分PIγDμ(fractional-order proportional-integral-derivative)相结合的策略。首先,利...为实现多变风况下直驱永磁风力发电系统的稳定、高效运行,提出一种模型预测电流控制MPCC(model predictive current control)与分数阶比例-积分-微分PIγDμ(fractional-order proportional-integral-derivative)相结合的策略。首先,利用MPCC两步预测法建立风力发电机组的电流预测模型,得到不同控制集下的电流预测值,评估确定出满足代价函数最小所对应的最优电流预测值。然后,设计PIγDμ控制器,将最优电流预测值和参考电流作为输入参数,经PIγDμ控制器输出得到最优控制电压矢量,实现对系统进行控制。最后,建立仿真模型,与双闭环PI和传统MPCC控制策略进行对比,验证所提控制策略的有效性和优越性。展开更多
永磁同步电机的模型预测控制是目前电机控制技术的研究热点之一,传统的单矢量模型预测电流控制(Model Predictive Current Control,MPCC)方法每个周期只有1个电压矢量作用,因此稳态性能较差,而且MPCC的控制性能受电机参数的影响较大。...永磁同步电机的模型预测控制是目前电机控制技术的研究热点之一,传统的单矢量模型预测电流控制(Model Predictive Current Control,MPCC)方法每个周期只有1个电压矢量作用,因此稳态性能较差,而且MPCC的控制性能受电机参数的影响较大。针对上述问题,提出了一种改进方法,即通过改进扩张状态观测器增加MPCC对电机参数的鲁棒性,结合一种新的三矢量模型预测控制方法来改善MPCC特性。仿真结果验证了本文所提方法的有效性。展开更多
针对Vienna整流器固有的中点电位波动问题,提出了一种基于冗余短矢量预判的模型预测电流控制MPCC(model predictive current control)方法。该方法可有效消除权重系数,进而解决MPCC权重系数调节困难的问题。首先,分析了Vienna整流器的...针对Vienna整流器固有的中点电位波动问题,提出了一种基于冗余短矢量预判的模型预测电流控制MPCC(model predictive current control)方法。该方法可有效消除权重系数,进而解决MPCC权重系数调节困难的问题。首先,分析了Vienna整流器的运行机理,并构建了其在稳态条件下基于同步旋转坐标系的数学模型。其次,详细分析了Vienna整流器直流侧电容中点电位波动的原因,并提出了抑制中点电位波动的方案。进一步,为了减小控制器计算负担,研究了MPCC的优化方案。最后,仿真及实验结果证明了所提控制方法的有效性与可行性。展开更多
AIM: To investigate the clinical features, diagnosis,treatment and prognosis of multiple primary colorectal carcinomas (MPCC). METHODS: A retrospective analysis of 37 patients with MPCC from 1974 to 1998 was carried o...AIM: To investigate the clinical features, diagnosis,treatment and prognosis of multiple primary colorectal carcinomas (MPCC). METHODS: A retrospective analysis of 37 patients with MPCC from 1974 to 1998 was carried out.RESULTS: The incidence of MPCC was 2.74%(37/1 348) in patients with primary colorectal carcinomas, 15 cases of them were patients with synchronous carcinomas (SC) and 22 cases were diagnosed as metachronous carcinomas (MC). Most tumors were located in the right colon and rectum. Fifty-five percent (12/22) of MC were diagnosed within 3 years after tumor resection and 41%(9/22) of MC occurred after 8 years. Radical resections were performed in all patients except for 1 case. The 5-year survival rate of SC was 72.7%(8/11) and that of MC after the first cancer and second cancer was 71.4%(15/21) and 38.9%(7/18), respectively. CONCLUSION: The results indicate the importance of complete preoperative examination, careful intraoperative exploration and periodic postoperative surveillance. Early diagnosis and radical resection can increase survival rate of MPCC.展开更多
针对无轴承异步电机传统矢量控制中存在电流畸变的问题,提出一种基于电流误差限定的模型预测电流控制(model predictive current control,MPCC)策略。在建立无轴承异步电机离散数学模型的基础上,根据定子电流和定子磁链观测值,预测下一...针对无轴承异步电机传统矢量控制中存在电流畸变的问题,提出一种基于电流误差限定的模型预测电流控制(model predictive current control,MPCC)策略。在建立无轴承异步电机离散数学模型的基础上,根据定子电流和定子磁链观测值,预测下一时刻的定子磁链和定子电流。运用电流误差限定策略对每个电压矢量下的电流进行筛选,选取最优电压矢量对应的开关状态作为逆变器的输出状态,从而有效降低开关频率。同时,引入全阶观测器,提高参数观测值的精确度,加快电机的收敛速度。由于系统存在滞后性,对系统进行延时补偿,进一步提高了电机的控制性能。仿真和实验结果均表明,采用所提MPCC策略的无轴承异步电机控制系统,电流畸变有效改善,能实现稳定悬浮,具有良好的静态特性和动态响应特性。展开更多
文摘为实现多变风况下直驱永磁风力发电系统的稳定、高效运行,提出一种模型预测电流控制MPCC(model predictive current control)与分数阶比例-积分-微分PIγDμ(fractional-order proportional-integral-derivative)相结合的策略。首先,利用MPCC两步预测法建立风力发电机组的电流预测模型,得到不同控制集下的电流预测值,评估确定出满足代价函数最小所对应的最优电流预测值。然后,设计PIγDμ控制器,将最优电流预测值和参考电流作为输入参数,经PIγDμ控制器输出得到最优控制电压矢量,实现对系统进行控制。最后,建立仿真模型,与双闭环PI和传统MPCC控制策略进行对比,验证所提控制策略的有效性和优越性。
文摘永磁同步电机的模型预测控制是目前电机控制技术的研究热点之一,传统的单矢量模型预测电流控制(Model Predictive Current Control,MPCC)方法每个周期只有1个电压矢量作用,因此稳态性能较差,而且MPCC的控制性能受电机参数的影响较大。针对上述问题,提出了一种改进方法,即通过改进扩张状态观测器增加MPCC对电机参数的鲁棒性,结合一种新的三矢量模型预测控制方法来改善MPCC特性。仿真结果验证了本文所提方法的有效性。
文摘针对Vienna整流器固有的中点电位波动问题,提出了一种基于冗余短矢量预判的模型预测电流控制MPCC(model predictive current control)方法。该方法可有效消除权重系数,进而解决MPCC权重系数调节困难的问题。首先,分析了Vienna整流器的运行机理,并构建了其在稳态条件下基于同步旋转坐标系的数学模型。其次,详细分析了Vienna整流器直流侧电容中点电位波动的原因,并提出了抑制中点电位波动的方案。进一步,为了减小控制器计算负担,研究了MPCC的优化方案。最后,仿真及实验结果证明了所提控制方法的有效性与可行性。
文摘AIM: To investigate the clinical features, diagnosis,treatment and prognosis of multiple primary colorectal carcinomas (MPCC). METHODS: A retrospective analysis of 37 patients with MPCC from 1974 to 1998 was carried out.RESULTS: The incidence of MPCC was 2.74%(37/1 348) in patients with primary colorectal carcinomas, 15 cases of them were patients with synchronous carcinomas (SC) and 22 cases were diagnosed as metachronous carcinomas (MC). Most tumors were located in the right colon and rectum. Fifty-five percent (12/22) of MC were diagnosed within 3 years after tumor resection and 41%(9/22) of MC occurred after 8 years. Radical resections were performed in all patients except for 1 case. The 5-year survival rate of SC was 72.7%(8/11) and that of MC after the first cancer and second cancer was 71.4%(15/21) and 38.9%(7/18), respectively. CONCLUSION: The results indicate the importance of complete preoperative examination, careful intraoperative exploration and periodic postoperative surveillance. Early diagnosis and radical resection can increase survival rate of MPCC.
文摘针对无轴承异步电机传统矢量控制中存在电流畸变的问题,提出一种基于电流误差限定的模型预测电流控制(model predictive current control,MPCC)策略。在建立无轴承异步电机离散数学模型的基础上,根据定子电流和定子磁链观测值,预测下一时刻的定子磁链和定子电流。运用电流误差限定策略对每个电压矢量下的电流进行筛选,选取最优电压矢量对应的开关状态作为逆变器的输出状态,从而有效降低开关频率。同时,引入全阶观测器,提高参数观测值的精确度,加快电机的收敛速度。由于系统存在滞后性,对系统进行延时补偿,进一步提高了电机的控制性能。仿真和实验结果均表明,采用所提MPCC策略的无轴承异步电机控制系统,电流畸变有效改善,能实现稳定悬浮,具有良好的静态特性和动态响应特性。
