The quality of power is always a concern for the high penetration of a grid-connected solar photovoltaic (PV) system due to the variation in solar irradiation and the temperature change of solar output, which in turn varies the fundamental component of power delivered to the grid. A solar source requires an inverter interface to supply the AC load as well as for the grid interconnection. Any reduction in the fundamental component generated by solar PV at a lower irradiation level or at high- temperature results in increasing %THD at the output of inverter for a given fixed switching frequency since harmonics due to PWM technique is comparable with the fundamental component. The selection of high-fixed-switching-frequency PWM reduces harmonics but increases the stress on switches and switching losses. It also suffers from issues of harmonics at carrier frequency and its sideband at multiples of switching frequency that causes acoustic noise and EMI. The random frequency PWM (Random PWM) method overcomes these issues presented by the fixed-frequency PWM method. However, a wide band of Random PWM makes the inverter filter design difficult and causes resonance in the distribution system. In addition, asymmetry in the carrier wave introduces even-order harmonics in the line current. Hence, this paper proposes a narrowband random frequency PWM method to reduce sideband harmonics, lower-order harmonics, even-order harmonics and a total harmonic distortion (THD) for a solar-based grid-connected inverter. Simulation results present a satisfactory performance of the proposed control technique for a steady-state and transient results. Experimental validation of the same is carried out on the OPAL-RT OP4500-based laboratory prototype of a 2-kVA inverter which depicts reduction in harmonics and hence improvement in power quality.

中文翻译：

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一种用于并网太阳能逆变器的窄带随机载频PWM技术

由于太阳辐射的变化和太阳能输出的温度变化，电力质量始终是并网太阳能光伏 (PV) 系统的高渗透率的问题，这反过来又会改变输送到电网的电力的基本分量。网格。太阳能需要一个逆变器接口来为交流负载以及电网互连供电。对于给定的固定开关频率，太阳能 PV 在较低辐射水平或高温下产生的基波分量的任何减少都会导致逆变器输出的 %THD 增加，因为 PWM 技术产生的谐波与基波分量相当。选择高固定开关频率 PWM 会减少谐波，但会增加开关应力和开关损耗。它还存在载波频率上的谐波问题及其在开关频率倍数下的边带问题，这会导致声学噪声和 EMI。随机频率PWM（Random PWM）方法克服了固定频率PWM方法带来的这些问题。然而，宽带随机 PWM 使逆变器滤波器设计困难，并在配电系统中引起谐振。此外，载波的不对称性会在线路电流中引入偶次谐波。因此，本文提出了一种窄带随机频率 PWM 方法，以减少太阳能并网逆变器的边带谐波、低次谐波、偶次谐波和总谐波失真 (THD)。仿真结果显示了所提出的控制技术对于稳态和瞬态结果的令人满意的性能。