In a multi-regional interconnected power system, load fluctuations are prone to cause active power imbalances, which require dynamic adjustment of generator output through dispatch commands (e.g., units entering or exiting frequency regulation queues). During this process, the switching of operation modes among different generation portfolios can be modeled as a multi-mode switched system. Since dispatch commands are usually transmitted via communication networks, the process is vulnerable to deception attacks, which can result in frequency excursions and even unit malfunctions. To address this issue, this paper proposes an event-triggered quantized load frequency control strategy resilient to deception attacks. First, a sparse matrix reconstruction method is used to reduce the dimensionality of sub-system models while preserving the controllability and observability of the distributed system, thereby establishing a switched multi-area power system model. Second, an event-triggered transmission mechanism is designed by considering the coupled effects of deception attacks and generation mode switching. Meanwhile, it is proven that there exists a continuous time window during which no attacks or mode switching occur, and this interval is utilized for state reconstruction. By introducing auxiliary sequences to construct iterative quantization rules, quantizer non-saturation is guaranteed at all times. Finally, from the perspective of optimal attack, sufficient conditions are derived to ensure exponential stability and practical stability of the load frequency control system (LFCS) in a switched multi-area interconnected power grid. Simulation results show that the proposed scheme can maintain reliable LFCS operation under deception attacks.