# A Multilevel Switched Capacitor Inverter with Reduced Components and Self-Balance
## 1 Introduction  
Multilevel inverters (MLIs) have emerged as an important tool for medium-voltage high-power applications like renewable energy system, electric vehicles (EVs), and flexible AC transmission systems [1; 2; 3]. MLIs possess many excellent features in contrast with the two-level inverter, such as a better performance in terms of total harmonic distortion (THD), reduced \(\mathrm{d}v/\mathrm{d}t\) stresses, a lower switching frequency, etc. [4]. Generally, conventional MLIs are divided into neutral-point clamped (NPC), flying capacitor (FC), and cascaded H-bridge (CHB) inverters [5]. However, NPC and FC inverters use numerous components with increasing voltage levels, and it is complicated to keep control of the balance of the capacitor voltage [6]. In addition, CHB inverters have drawbacks like a strong demand for isolated DC sources and a lack of boost capacity [7]. It is noteworthy that the MLIs based on the switched capacitor (SC) technique are capable of self-balancing the capacitor voltage as well as raising the input voltage [8; 9]. With these unique advantages, switched capacitor multilevel inverters (SCMLIs) have been widely studied and have produced various topologies. For instance, the inverters in [10; 11; 12; 13; 14] use several DC sources combined with switched capacitors to produce a multilevel output. The SCMLIs proposed in [10; 11] can achieve a double voltage gain with self-charging capacitors. To obtain a greater number of voltage levels, the 17-level switched capacitor inverter in [12] was developed using two SC cells. In [13; 14], the inverters achieved a higher boosting factor with a number of SC units. Nevertheless, the above topologies have a common defect, namely that of employing multiple DC sources, which results in the growth of application cost. In order to solve the aforesaid issue, several single-source SCMLIs were proposed in [15; 16; 17; 18]. The inverter in [15] achieved seven-level output with a single source, and morelevels were obtained in [16; 17; 18] using extended structures. However, these topologies all use the H-bridge to transform the direction of the output voltage, which can raise the total standing voltage (TSV) of switches. The H-bridge was removed in [19; 20; 21; 22] due to the intrinsic inversion ability. The multilevel inverter based on the K-type unit in [19] has a voltage gain of 1.5, while a triple boosting factor was obtained in [20; 21; 22]. The three MLIs include a T-type which maintains the capacitor voltage at half of the input voltage to produce more output levels. Nevertheless, the above topologies could be improved if they did not require abundant devices for a higher boosting factor, an issue identical to that found in [23]. The works [24; 25; 26; 27] developed 13-level switched capacitor inverters which achieve a voltage gain of six with fewer components. Through the regular charging-discharging of the capacitor, the inverter proposed in [24] can realize the self-balancing of capacitor voltages, but the voltage stress of the switches is high. The stress on the devices of the inverter in [25] decreased, which was restricted to half the maximum output voltage. The multilevel inverter proposed in [26] used fifteen transistors and three capacitors, and the output voltage polarity was changed with two half-bridge modules. Two switched capacitor inverters proposed in [27] only used twelve switches. The topologies contain a triple-mode SC unit and a simplified SC unit. The inverter proposed in [28] also uses a triple-mode SC, but employs four capacitors, which leads to an increase in volume. In addition, the abovementioned structures cannot be expanded and the application scenarios are restricted. Based on the previous analysis, a new 13-level SCMLI is proposed in this paper, and it has the following excellent features:  
1. The proposed multilevel inverter can acquire six-fold voltage gain with a reduced number of components;
2.