Pursuing Photovoltaic Cost-Effectiveness: Absolute Active Power Control Offers Hope in Single-Phase PV Systems

Abstract

Abstract-Countries with considerable PhotoVoltaic (PV) installations are facing a challenge of overloading their power grid during peak-power production hours if the power infrastructure remains the same. To address this, regulations have been imposed on PV systems, where more active power control should be flexibly performed. As an advanced control strategy, the Absolute Active Power Control (AAPC) can effectively solve the overloading issues by limiting the maximum possible PV power to a certain level (i.e., the power limitation), and also benefit the inverter reliability due to the reduction in the thermal loading of the power devices. However, its feasibility is challenged by the associated energy losses. An increase of the inverter lifetime and a reduction of the energy yield can alter the cost of energy, demanding an optimization of the power limitation. Therefore, aiming at minimizing the Levelized Cost Of Energy (LCOE), the power limit is optimized for the AAPC strategy in this paper. The optimization method is demonstrated on a 3-kW singlephase PV system considering a real-field mission profile (i.e., solar irradiance and ambient temperature). The optimization results have revealed that superior performance in terms of LCOE and energy production can be obtained by enabling the AAPC strategy, compared to the conventional PV inverter operating only in the maximum power point tracking mode. In the presented case study, the minimum of the LCOE is achieved for the PV system when the power limit is optimized to a certain level of the designed maximum feed-in power (i.e., 3-kW). In addition, the LCOE-based analysis method can be used in the design of PV inverters considering long-term mission profiles.

Grid Friendly Operation of a PV-Storage System with Profit Maximization and Reliability Enhancement

“…As an outcome of this investigation, the inverter lifetime is shown to decrease by up to 70% when the inverter is operating with unfavorable thermal-power loading. Investigation studies in [4] and [5] show that by using a constant power mode or limiting the maximum output power of the inverter to a lower value (i.e., at 80% of the rated power) can reduce the thermal loading of the inverter and double or even triple its lifetime. However, such a power limitation reduces the generated energy from PVs (significant losses due to energy shedding at the peak power) and as a result the profit from selling the energy to the grid is reduced.…”

“…Therefore, extending the lifetime of the grid tied inverter is essential to enhance the reliability of the entire hybrid DC coupled system and minimize the levelized cost of electricity in such a novel configuration. To extend the inverter's lifetime, the optimization method considers a limit for the maximum power output of the inverter to 80% of its rated power (thus, the inverter lifetime can be extended by 200-300% according to [4] and [5]). Therefore, the proposed method can close the gap between the expected lifetime of existing inverters and the lifetime of the KSS reducing the maintenance cost of such configuration.…”

Mission Profile-Oriented Control for Reliability and Lifetime of Photovoltaic Inverters

“…For instance, PV power variations (reflecting mission profile characteristics) induce thermal fluctuations on the inverters. Hence, limiting the maximum feed-in power can smooth the temperature variations and lower the thermal loading to some extent [19]- [21]. This contributes to improved lifetime, which can also be seen in smart de-rating control strategies [22].…”

A Novel Digital Control Method of a Single-Phase Grid-Connected Inverter Based on a Virtual Closed-Loop Circuit and Complex Vector Representation

“…Among various connecting methods, the single-phase grid-connected inverter is one of the commonly used interfaces for DGs [8,9]. Due to the continuously-changing power output of the renewable resources, a better control performance is expected for the single-phase grid-connected inverter [10,11].…”