Ensuring Accurate Frequency in the Hardware Design of Grid-Forming (GFM) Inverter

Accurate frequency generation is crucial for the hardware implementation of a grid-forming inverter (GFM). Unlike grid-following inverters (GFL), the phase angle and frequency generation in GFMs rely entirely on on-device computation and the crystal oscillator. Due to inaccuracies in the crystal oscillator and floating point quantization errors, the frequency of GFM inverters can drift. This drift can cause power sharing inequalities and interactions in multi-loop GFM control, leading to instability during operation. This issue applies to all microcontrollers and simulations that use 32-bit floating-point arithmetic for control algorithms. In this paper, we demonstrate a case study of frequency drifting in GFM inverters caused by floating point computation errors. We propose two solutions to solve the frequency drift issue in GFM. Finally, we present how the proposed GFM clock generators improve droop control power sharing and solve multi-loop GFM control interactions due to frequency drifting. Hardware and simulation results are provided to demonstrate the effectiveness of the proposed solutions.