The principle of minimum dissipation rate is applied to tokamak plasmas with energy and helicity balances imposed as two constraints. The analytical solution on toroidal current distribution are derived from the resul...The principle of minimum dissipation rate is applied to tokamak plasmas with energy and helicity balances imposed as two constraints. The analytical solution on toroidal current distribution are derived from the resulting Euler-Lagrangian equation. Three typical forms of current profiles are found for low-aspect-ratio tokamaks like NSTX. One of them decreases with r on equatorial plane, the second peaks in the inner half part on equatorial plane and the third may have a hole or reverse in the central part.展开更多
1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedan...1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedance attract attention, for high input impedance has the advantage that the networksmay be used in cascade without requiring impedance matching device. In the Higashimura and展开更多
在设计和研发大功率宽输出电压范围的双有源桥(dual active bridge,DAB)变换器时,传统的电流应力优化策略往往只关注移相比优化,忽略了电感量变化对电流应力的影响,这可能导致在大功率应用中电流应力超出理论预期,从而降低开关管的可靠...在设计和研发大功率宽输出电压范围的双有源桥(dual active bridge,DAB)变换器时,传统的电流应力优化策略往往只关注移相比优化,忽略了电感量变化对电流应力的影响,这可能导致在大功率应用中电流应力超出理论预期,从而降低开关管的可靠性。因此,在大功率应用场景下,为使变换器在全功率范围内获得最小电流应力,首先提出了考虑电感量随电流应力变化的动态关系,并基于此关系选择在恰当电感量下的优化三移相控制方法;其次,通过分析三移相控制并建立相应的数学模型,利用KKT(Karush-Kuhn-Tucker)条件寻求最优移相比组合,以实现电流应力优化;最后,搭建额定功率为100 kW的DAB变换器仿真模型及样机实验平台进行验证。实验结果表明,与传统三移相控制方法相比,所提方法在仿真和实验中都表现出较高的有效性,确保了变换器在整个运行过程中电流应力始终保持在理论预期范围内,保证了变换器在稳定运行时开关管的可靠性。展开更多
文摘The principle of minimum dissipation rate is applied to tokamak plasmas with energy and helicity balances imposed as two constraints. The analytical solution on toroidal current distribution are derived from the resulting Euler-Lagrangian equation. Three typical forms of current profiles are found for low-aspect-ratio tokamaks like NSTX. One of them decreases with r on equatorial plane, the second peaks in the inner half part on equatorial plane and the third may have a hole or reverse in the central part.
文摘1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedance attract attention, for high input impedance has the advantage that the networksmay be used in cascade without requiring impedance matching device. In the Higashimura and
文摘在设计和研发大功率宽输出电压范围的双有源桥(dual active bridge,DAB)变换器时,传统的电流应力优化策略往往只关注移相比优化,忽略了电感量变化对电流应力的影响,这可能导致在大功率应用中电流应力超出理论预期,从而降低开关管的可靠性。因此,在大功率应用场景下,为使变换器在全功率范围内获得最小电流应力,首先提出了考虑电感量随电流应力变化的动态关系,并基于此关系选择在恰当电感量下的优化三移相控制方法;其次,通过分析三移相控制并建立相应的数学模型,利用KKT(Karush-Kuhn-Tucker)条件寻求最优移相比组合,以实现电流应力优化;最后,搭建额定功率为100 kW的DAB变换器仿真模型及样机实验平台进行验证。实验结果表明,与传统三移相控制方法相比,所提方法在仿真和实验中都表现出较高的有效性,确保了变换器在整个运行过程中电流应力始终保持在理论预期范围内,保证了变换器在稳定运行时开关管的可靠性。
