## 2 The MC and Supraharmonics  
Several research works [1; 3; 6; 18] have identified the sources of these supraharmonics as power electronic converters with higher switching frequencies. The authors in [1] \begin{table}
\begin{tabular}{c c} \hline \hline
**Load** & **Switching Frequency (kHz)** \\ \hline Electric vehicle chargers & 15–100 \\ Solar PV inverters & 4–20 \\ Power communication lines (PCLs) & 9–95 \\ Communication notch oscillations & Up to 10 \\ Industrial size converters & 9–150 \\ Street lighting systems & Up to 20 \\ Household electronic devices (LEDs and CFLs) & 2–150 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Operating frequency ranges of electronic converters for selected loads. presented supraharmonics propagation from electric vehicles with respect to small and low-voltage grids. They concluded that supraharmonic frequencies may result in the tripping of residual current devices and \"frequency beating\". The authors in [3; 6] seek to establish standardization and measurements for supraharmonic applications. They concluded that the emissions from supraharmonic frequencies reduce the efficiency and life expectancy of electrical equipment. Power electronic converters are also the primary victim of supraharmonic frequencies, as their dynamic performance are crippled, as the authors in [4; 5; 19; 20] explored. The authors in [4; 5] explored the power electronic converters and supraharmonics and [17] confirmed the effect of higher harmonic frequencies as the reduction in lifespan of power system devices. The authors in [8] successfully modeled the emissions from supraharmonic devices from the parallel operation of two converters and confirmed that it can be predicted by linear models. The advantages of the use of MCs supersedes that of the traditional back-to-back converters [21; 22]. Paramount is its bi-directional operation and the absence of energy storage elements. Irrespectively, the MC's voltage transfer ratio of 0.867 and supraharmonic input and output frequencies discourages its use. The authors in [23; 24; 25] explored power quality issues with the matrix converter and proposed possible active power filters (APF) as a solution. The large switching states of the MC produces discontinuous input currents and voltage spikes in the supply grid. Figure 1 shows the power system connected to an MC interfaced load with the hybrid active power filter between the supply and the load. From Figure 1, the input current is composed of active and reactive powers and the harmonics, as shown in Equation (2). These supraharmonics are propagated into the power system due to the discontinuous currents of the MC [26; 27; 28; 29]. Table 2 shows the reviewed literature on the topic. Figure 1: Power system with MC interfaced load and hybrid active power filter in between. If the supply voltage and current are considered as Equation (1) and Equation (2), respectively, then the instantaneous power at the input side of the MC can be expressed as Equation (3). Passive filters are the most recommended solution for MC harmonic attenuation. But resent load dynamics has made passive filter solutions not a feasible option due to compact size and light weight converters being the most required attributes in today's load applications. Active harmonic power filters are economically not recommended for higher frequency compensation. With this, researchers are now focusing on hybrid active power filter solutions consisting of passive R-L-C and shunt active power filters.