对双主动全桥DAB(dual active bridge)双向DC/DC变换器的调制方案进行了研究,DAB变换器的主要优势在于具有对称结构、双向潮流能力、宽软开关区域和灵活的控制能力等特点。控制这种拓扑结构最简单的方法是通过控制变换器原副边全桥之间...对双主动全桥DAB(dual active bridge)双向DC/DC变换器的调制方案进行了研究,DAB变换器的主要优势在于具有对称结构、双向潮流能力、宽软开关区域和灵活的控制能力等特点。控制这种拓扑结构最简单的方法是通过控制变换器原副边全桥之间的移相角来控制功率传输的方向和大小。然而在轻载条件下,当变换器的输入或输出电压变化较大时,会产生大量的无功功率,同时部分开关管的零电压开关ZVS(zero voltage switching)操作会丢失而直接导致转换效率变低。因此,为了提高DAB变换器的效率,提出了一种混合单移相调制PSM(phase shift modulation)方案,在保持控制简单的基础上,通过减小电感电流有效值,扩大软开关的范围,提高了变换器的效率。首先,通过让拓展移相EPS(extended phase shift)、双移相DPS(dual phase shift)以及三移相TPS(triple phase shift)调制方案中的可控变量相等,从而形成了4种不同的PSM方案。接着,对这些调制方案进行了稳态特征的比较分析,包括传输功率容量、电感电流水平以及软开关性能等。在此基础上,提出了一种混合PSM方案。最后,通过搭建实验平台验证了所提出调制方案的有效性和正确性。展开更多
The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five importa...The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.展开更多
针对不对称半桥(asymmetric half bridge,AHB)变换器占空比变化范围宽而带来输出二极管电压应力高、且存在电压增益曲线呈非线性特性的问题,研究了AHB副边谐振(secondary side resonant,SSR)PWM开关变换器。AHB-SSR-PWM变换器原边采用...针对不对称半桥(asymmetric half bridge,AHB)变换器占空比变化范围宽而带来输出二极管电压应力高、且存在电压增益曲线呈非线性特性的问题,研究了AHB副边谐振(secondary side resonant,SSR)PWM开关变换器。AHB-SSR-PWM变换器原边采用不对称脉冲宽度调制,实现了开关管的零电压开通(zero voltage switching,ZVS),且原边开关管的电压应力箝位在输入电压;AHB-SSR-PWM变换器副边用带滤波电感的谐振支路代替传统的半波整流支路,实现了输出二极管的零电流关断(zero current switching,ZCS)。此外,AHB-SSR PWM开关变换器的输出端存在滤波电感,减小了输出电压的纹波。分析结果表明,输出二极管的电压应力几乎与占空比无关;电压增益与隔离Buck类变换器类似,呈现线性增益特性。通过一台200 V输入,24V/2A输出的实验模型验证了理论分析的正确性。展开更多
基金supported by the Chinese Important National Science and Technology Specific Project(2010ZX03002-003-01)
文摘The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.
文摘针对不对称半桥(asymmetric half bridge,AHB)变换器占空比变化范围宽而带来输出二极管电压应力高、且存在电压增益曲线呈非线性特性的问题,研究了AHB副边谐振(secondary side resonant,SSR)PWM开关变换器。AHB-SSR-PWM变换器原边采用不对称脉冲宽度调制,实现了开关管的零电压开通(zero voltage switching,ZVS),且原边开关管的电压应力箝位在输入电压;AHB-SSR-PWM变换器副边用带滤波电感的谐振支路代替传统的半波整流支路,实现了输出二极管的零电流关断(zero current switching,ZCS)。此外,AHB-SSR PWM开关变换器的输出端存在滤波电感,减小了输出电压的纹波。分析结果表明,输出二极管的电压应力几乎与占空比无关;电压增益与隔离Buck类变换器类似,呈现线性增益特性。通过一台200 V输入,24V/2A输出的实验模型验证了理论分析的正确性。
