Ensuring deterministic control in local smart grid nodes based on real-time operating systems

Abstract

The evolution of modern Smart Grid intelligent power systems requires the delegation of control functions to the network edge, increasing the significance of local nodes in real-time data acquisition and processing. The stability of the power grid depends on the temporal predictability (determinism) of embedded controllers, as even minor delays can lead to instability in power system operating mo-des. This article addresses the problem of ensuring millisecond-scale response in
control systems under the constraints of limited microcontroller platform resources.
The study employs system analysis of cyber-physical system architectures and a comparative analysis of task scheduling mechanisms within the FreeRTOS environment. The experimental part is based on modeling a local node's operation on a microcontroller platform with hardware-based tracing of timing parameters (latency, response time, and jitter) across various load conditions.
The key factors affecting determinism were investigated: hardware limitations, the intensity of communication interfaces (I2C, UART, SPI), and power stability. The use of FreeRTOS as a tool to ensure predictable system behavior through preemptive scheduling, interrupt prioritization, and synchronization mechanisms (queues, semaphores, mutexes) is substantiated.
During the experiment, four operational modes were tested: basic, intensive data exchange, high computational load, and a combined mode. It was established that even in the most complex combined mode, the system response time remains within the sub-millisecond range (average response time of 420 μs), confirming the effectiveness of the chosen architecture. The study identified that the primary destructive factors are priority inversion and competition for hardware
resources during the simulta-neous operation of multiple interfaces.
It has been proven that stable timing behavior is achieved through rational software-hardware configuration: separating tasks by criticality, minimizing code in interrupt service routines (ISR),using mutexes with priority inheritance mechanisms, and employing supercapacitors for power redundancy. The proposed approaches guarantee compliance with timing deadlines in local Smart Grid nodes. Prospects for further research involve the development of adaptive priority management algorithms.

Keywords: embedded control systems, timing deadlines, system latency, signal jitter, task scheduler, process synchronization, cyber-physical energy systems, microcontroller platforms.