## 1 Introduction  
Through the Paris Climate Change Accord in 2015, it became mandatory to reduce the emission of carbon dioxide worldwide. The government of the Republic of Korea also announced a significant reduction in greenhouse gas emissions by 37% compared to business as usual (BAU) by 2030 [1]. As a result, the era of decarbonization, which resolves the emission of carbon dioxide, the main cause of environmental pollution, has begun, and interest in carbon-free, pollution-free renewable energy is increasing significantly. Energy decarbonization means that the amount of carbon per unit mass of the main energy source (coal, oil, natural gas, etc.) decreases. Energy decarbonization can be achieved if renewable energy becomes the main energy source. Among the various renewable energy sources, wave energy is one of the most popular sources of energy due to the geographical characteristics of Korea, which has three sides open to the sea. The amount of wave energy in Korea is about 5.5 million kW [2], and it is important to utilize it well. However, converting this energy into electricity is not easy. Although it has been attempted from the late 19 th century, it took a long time to commercialize it due to low power conversion efficiency, while compared to other renewable energy power generation devices that have already been formalized, various types of wave power generators are still being researched and developed. Wave power generators creating power by using the energy of waves produce energy through the process of primary energy conversion converting from the potential and kinetic energy of the waves to mechanical energy, secondary energy conversion converting energy for generator operation using a mechanical system or hydraulic system, and final energy conversion for power generation. The primary energy conversion is classified according to differences in the method of absorbing wave energy such as rotational displacement, horizontal or vertical displacement when absorbing energy from waves. Representatively, there are oscillating water column (OWC), overtopping, and movable object type wave power generators according to the primary energy conversion method as shown in Figure 1. Among them, the movable object type wave power generator is very advantageous in terms of energy-absorbing efficiency because wave energy directly affects the floating body. In addition, the point absorber wave power generator having a smaller floating body size than the wavelength is advantageous for applying to multiple generations using the same sized structures or installing in parallel with other energy sources. Therefore, many studies have been conducted recently. The whole process of energy conversion of primary energy conversion, secondary energy conversion, and final energy conversion through movable object type wave power generators can be expressed as shown in Figure 2. In the primary energy conversion, the vertical or horizontal reciprocating motion of the waves is transferred to the vertical or horizontal reciprocating motion of the floating body. In the second energy conversion, this motion is transmitted to a rotational motion using mechanical systems such as gears, pulleys, gearboxes, or hydraulic system elements such as hydraulic cylinders, hydraulic pumps, and hydraulic motors. This rotational motion is transmitted through the shaft to drive a generator. In the final energy conversion, this motion is converted into electrical energy through a generator. Figure 1: Classification of wave power generators. Until now, for the primary energy conversion system of the movable object type wave power generator, studies such as comparing and verifying the performance by changing the shape or angle of incidence of the floating body have been actively conducted [3; 4; 5; 6; 7; 8; 9]. In addition, many studies on efficiency analysis using experiments and simulation techniques have been performed on the movable object type wave power generator [10; 11; 12; 13; 14].