###### Abstract  
In this study, a wind energy conversion system is designed using a three-phase permanent magnet synchronous generator, a six-diode bridge rectifier, a DC-DC boost converter, an inverter, and a load. The proposed inverter is a Packed U-Cell-based multilevel inverter having five or seven voltage levels at the output. It is also a topology that is not widely used in wind energy applications. Furthermore, a dual-mode PI-PI control technique is proposed to regulate the auxiliary capacitor voltage in the PUC MLl. The inverter is designed and simulated for a permanent magnet synchronous generator-based variable speed wind energy conversion system. Additionally, the design and experimental application of the proposed system is carried out in a laboratory environment. In the experimental application, the rated voltage of the Packed U-Cell multilevel inverter is chosen as 45 V. The switching frequency of the multilevel inverter is set to 4 kHz, and a generator with rated power of 700 W is selected. The output voltage of the generator is varied between 25 V and 35 V through an induction motor. This varying voltage is increased to 45 V using a DC-DC boost converter. Finally, it is observed that the power generated by the permanent magnet synchronous generator is successfully transferred to the load and the designed system operates with low harmonic content. P acked U-Cell; DC-DC boost converter; multilevel inverter; permanent magnet synchronous generator; wind energy conversion system +
Footnote †: journal: Applied  
837 GW by the end of 2021. The value of the total wind installed power is obtained as the sum of the total onshore power and total offshore power [9]. At the end of 2021, the total onshore value had increased by 72,499 MW compared to the previous year and reached 780,275 MW. Moreover, the total offshore value had increased by 21,106 MW compared to the previous year and reached 57,176 MW [10]. The wind power capacity had increased by approximately 78 GW in 2022 worldwide. Thus, the total installed capacity had reached 906 GW by 2022 [11]. The historical change in total installations is demonstrated in Figure 1.  
Generators are used to convert the mechanical energy obtained from wind turbines into electrical energy. The generators used in WECS are generally classified into two types, namely induction generators and permanent magnet synchronous generators (PMSGs) [12; 13; 14]. Originally, the use of PMSGs was limited to small wind power turbines. It was not extended to large-scale electrification because it required large and powerful permanent magnets and these magnets were very expensive. However, due to the gearless design, the complete controllability of the system, and the excellent efficiency of the PMSG, it is widely preferred in WECS [15; 16; 17]. The PMSG is widely utilized in variable speed operations, particularly at extremely low and medium power levels. PMSGs offer several advantages, including a decreased volume and weight, minimal maintenance, gearbox elimination, brushless operation, and not requiring any energy source for excitation. One of the most important advantages is that they can generate power at any speed. PMSGs are classified as radial, axial, and cross flux according to the direction of the produced flux in the machine. However, radial flux PMSGs are preferred for both motoring and generator actions, because they are simpler, more reliable, and more practical to manufacture than the other two types. PMSGs have surface-mounted and rotor-inserted magnet types, depending on the position of the magnet on the rotor surface. In addition, inner and outer rotor types are available for positioning the rotor inside or outside the stator [18; 19]. The proposed WECS in this study is composed of a three-phase PMSG, a six-diode bridge rectifier for the AC-DC conversion, a DC-DC boost converter, a Packed U-Cell (PUC) multilevel inverter (MLI) for the DC-AC conversion, and an adjustable RL load.