功率因数校正在能量收集系统中最大化功率效率和质量
在任何配电系统中,非电阻性负载会使电流和电压发生相位偏移,导致无功功率损失。当电流和电压在纯电阻性负载的情况下保持相位时,感性负载存储无功功率并导致电流滞后电压,而容性负载导致电流导通电压。当电流波形不跟随电压波形时,不仅失去功率,而且产生的谐波可以通过配电系统传播,破坏其他连接的设备。
当电流和电压波形靠近时,所有的功率都包含在基波频率中,谐波降到零。功率因数校正(PFC)的工作,以控制电流,以配合电压的形状和相位,最大限度地提高实际电源可从源有效地转换负载到一个纯粹的电阻之一。
在微观层面上,功率因数校正为能量收集电路的设计者提供了直接的好处。用于从环境中获取能量的功率调节电路通常会产生电流输出中的谐波,从而导致功率损耗。在这种情况下,线性稳压器的使用会导致在最佳操作包络外工作时的效率降低,而开关稳压器的使用可能会带来额外的设计挑战,以解决可能限制最佳功率输出的稳定性问题。PFC电路是为应对这些挑战而设计的。
As a result, power factor correction (PFC) plays a critical role in maximizing real power and maintaining its quality. The simplest way to control the harmonic current is to use a filter that passes current only at line frequency. This filter reduces the harmonic current, which means that the nonlinear device now looks like a linear load. At this point, the power factor can be brought to near unity using capacitors or inductors as required. This filter requires large-value, high-current inductors, which are bulky and can be expensive.
Unlike passive PFC methods, active methods achieve PFC with minimal component count and cost. Drawing on a wide selection of integrated devices, designers can easily implement PFC in energy-harvesting applications using ICs from manufacturers including Cirrus Logic,Freescale Semiconductor, Fremont Micro Devices, Linear Technology, ON Semiconductor, Renesas, STMicroelectronics, Texas Instruments, and Toshiba, among others.
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