Constant power generation of photovoltaic systems considering the distributed grid capacity

Abstract

Abstract-With an imperative demand of clean and reliable electricity generation in some countries, the increasing adoption of new photovoltaic (PV) systems pushes the Distribution System Operators (DSOs) to expand the transmission/distributed lines. However, the potential cost brought by such extensions and increased maintenances introduce new obstacles. In view of this concern, the DSOs starts to reduce PV installations in order to avoid an extension of the power infrastructure. Besides, another alternative solution is to limit the maximum feed-in power of the existing PV systems to a certain level. It can contribute to a weakened requirement of grid expansion and at the same time an increased penetration level. Therefore, to meet the need of this emerging ancillary service provided by future PV systems, a Constant Power Generation (CPG) control concept of PV inverters is proposed in this paper. Accordingly, it is worth investigating into two main issues: a) analyzing the reduction of the energy yield due to CPG control to study its feasibility from an economic point of view and b) developing robust CPG control methods, otherwise, it may introduce instabilities. Thereby, the implementation possibilities for PV systems in CPG operation mode are also discussed in this paper. Additionally, the loss of energy is calculated to reveal the viability of the proposed CPG control method. Operation examples of a PV system are presented to show the effectiveness of the CPG control method to unload the distributed grid.

Improved reliability of single-phase PV inverters by limiting the maximum feed-in power

“…The boost converter offers the flexibilities of MPPT and active power control (e.g. CPG control) [9], and extends the operational time of the PV inverter when the solar irradiance level is very low. The PV inverter can be transformerless to maintain a high efficiency.…”

“…A hybrid control scheme of MPPT and CPG control allows further to increase the penetration level. The CPG control can be implemented by a) integrating energy storage systems like a battery, b) managing the power at the secondary control level, and c) modifying the conventional MPPT algorithms [4], [8], [9].…”

“…Seen from this point, it is interesting to justify the long-term performance of PV inverters from both reliability and economic viability (i.e. a trade-off between the lifetime extension and the overall energy yield reduction), and thus find the optimal power limitation level in terms of cost-of-energy [4], [9], [11].…”

“…required for wind power systems in Denmark, should also be transitioned and strengthened into the nextgeneration PV systems [1], [4]- [9]. As a power limiting control, a Constant Power Generation (CPG) control by limiting maximum feed-in power has been proposed in [9], and witnessed as an effective way to eliminate overloading. When it is compared to the solutions of expanding the power grid infrastructure or integrating energy storage systems to tolerate the peak power [4]- [11], the CPG control might be a more economically viable strategy, since it only contributes to a limited energy yield reduction in a real case, where typically the peak power generation is very rare.…”

“…In the case of a very largescale adoption of PV systems, advanced control strategies like power-ramp limitation and absolute power control, which are currently e.g. required for wind power systems in Denmark, should also be transitioned and strengthened into the nextgeneration PV systems [1], [4]- [9]. As a power limiting control, a Constant Power Generation (CPG) control by limiting maximum feed-in power has been proposed in [9], and witnessed as an effective way to eliminate overloading.…”