## 1 Introduction
The voltage control method of a cascaded step-up switched-capacitor converter (CSU-SCC) under a zero current switching (ZCS) operation and continuous conduction mode is proposed in [PERSON] et al. [25], to achieve high voltage gain and reduce the number of components. In the work by [PERSON] et al. [26], a switched inductor multilevel boost converter for higher DC voltage applications is proposed, the main advantage of which is that the voltage stress on the switch is smaller. In the aforementioned schemes, the main drawbacks are the complexity of the control structure, and the need for more components which will increase cost. The choice of the most suitable boost converter to be used in a PV system is difficult to determine due to the fact that each boost converter has its own advantages and disadvantages, and the choice is highly application-dependent. Typically, a conventional boost converter is used in grid-connected SPV systems due to it having a simple structure and being easy to implement in practical systems, leading to lower costs. For this reason, in this work a conventional boost converter is considered. In general, the maximum power point tracking (MPPT) technique is used in SPV systems to increase the power obtained under all environmental conditions. The MPPT control technique works well during normal conditions, but the MPPT controller affects the system under faulted conditions. Furthermore, when a grid fault occurs, the point of common coupling (PCC) voltage goes down, which leads to a power imbalance on the inverter's side, and this results in detachment of the inverter from the power grid according to the over voltage protection standard [27]. Thus, to protect the inverter while satisfying the GC, a novel control scheme must be developed with MPPT control for controlling DC-DC converters, and also to limit the output voltage to a safe value under both normal and fault conditions. Often, according to grid code requirements, the active and reactive power values are not appropriately satisfied by most of the existing LVRT schemes. This work attempts to enhance the LVRT capabilities of grid-connected SPV systems by controlling the DCL overvoltage, and realize reactive power and active power support based on GC requirements. In reference to the aforementioned background, this work proposes a novel control scheme that controls the DCL voltage rise within standard limits, without imposing extra system costs under normal and fault conditions, by using two controllers. The control mechanism consists of an \"MPPT\"scheme and a \"control without MPPT\" scheme. The developed algorithm properly operates these controllers in the normal and fault conditions. When a grid fault occurs, the \"control without MPPT\" controller minimizes the active power injected into the grid, which will ultimately trigger the inverter to inject the required amount of reactive current into the power grid; the system then provides grid support and voltage recovery, while not exceeding the specified safe current value of the inverter. Compared to the existing methods, the proposed method can not only effectively reduce the DC-link over voltage during a grid fault, but also provide reactive power support to the grid according to the German E.ON grid code requirements, without using any extra hardware. Simulation studies were conducted to validate the effectiveness of the proposed control strategy. This paper is organized as follows: Section 2 describes the grid-connected solar PV system. Section 3 explains the impacts of a fault on the grid-connected SPV system. Section 4 describes the proposed control strategies. Section 5 reports the simulation test findings and discussion. A comparison of the conventional and proposed strategies is given in Section 6. Finally, Section 7 presents our conclusions.