## 2 Power Quality in DC Microgrids  
It is important to emphasize that the phenomena related to PQ for DC distribution systems share certain issues in common with AC distribution systems, but they also have some particularities. In the case of AC systems, PQ considerations are well studied and standardized, but on the other hand, some phenomena in DC systems have not yet been fully evaluated [16]. Converters have other requirements. The PQ phenomena in Low Voltage Direct Current (LVDC) distributed systems can arise due to the system's topology, as well as the operating states of its sources and loads. Additionally, the performance of the DC output of individual converters and the coordination among several converters may contribute to various PQ issues and grid stability challenges. The main PQ phenomena, along with their associations with AC and DC systems, are summarized in Table 1.  
However, since there is no fundamental frequency in a DC system, the concepts of harmonic distortion and oscillation and frequency variation cannot be applied. On the other hand, power conversion devices (such as DC-DC converters) can introduce noise and ripple voltages and currents [17; 18]. Any non-DC component of the load current flowing over the LVDC bus will result in a ripple voltage that will appear at all points along the bus. Non-DC components in the load current, such as harmonics or pulsating currents, create ripple voltage in an LVDC system. This ripple voltage appears at all points along the bus because it is caused by ripple currents that flow between the connected loads and the  
Figure 1: Control strategies in DCMG. DC power supply. These ripple currents arise due to the interaction between fluctuating load currents and the bus's electrical impedance, leading to unwanted voltage variations throughout the system. If an inverter with PWM modulation is used to produce the DC voltage, a high-frequency waveform resulting from pulse-width modulation switching is superimposed on the DC and AC side, which is often referred to as noise. Noise can also come from the inverter-based loads connected to the DC bus. When using a PWM-based inverter to generate DC voltage, high-frequency switching introduces noise on both the DC and AC sides. This noise, caused by pulse-width modulation, appears as a high-frequency waveform superimposed on the desired output. Additionally, inverter-based loads connected to the DC bus can contribute further noise, leading to potential interference and performance issues. PWM can impact the sensitivity of connected loads in an LVDC system by introducing electromagnetic interference (EMI), ripple voltage, thermal stress, and communication disruptions. The establishment of standards and norms plays a crucial role in ensuring high PQ [19], especially in the context of MG, where decentralized production and distribution challenge traditional paradigms. Standardization in the context of MG not only ensures PQ, but also facilitates the widespread acceptance and implementation of these decentralized systems. The increasing implementation of MG highlights the need to establish rigorous standards to ensure effective and safe operations. In this scenario, international organizations such as the International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronics Engineers (IEEE) play a crucial and significant role in formulating and updating standards. In the current DCMG scenario, various approaches and voltage levels are