This paper explores the next-generation photovoltaic (PV) system integration issues considering a high penetration level, where the grid is becoming more decentralized and vulnerable. In that case, the PV systems are expected to be more controllable with both higher efficiency and higher reliability. Provision of ancillary and intelligent services, like Low Voltage Ride-Through (LVRT), flexible active power control (i.e., outside the maximum power point tracking), reactive power compensation (e.g., reactive power at nights), and reliability-oriented thermal management/control by PV systems are key methods to attain higher utilization of solar PV energy in the power electricity generation. Those essential functionalities for the future PV inverters can contribute to reduced cost of energy, and thus enable more cost-effective PV installations. In order to implement the advanced features, a flexible power controller is developed in this paper, which can be configured in the PV inverter and flexibly change from one to another mode during operation. This power control strategy is based on the single-phase PQ theory, and it offers the possibilities to generate appropriate references for the inner current control loop. The references depend on the system conditions and also specific demands from both system operators and prosumers. Besides, this power control strategy can be implemented in a commercial PV inverter as standardized function, and also the operation modes can be achieved online in a predesigned PV inverter. Case studies with simulations and experiments in this paper have verified the effectiveness and flexibilities of the power control strategy to realize the advanced features.