Running DFT-Based PLL Algorithm for Frequency, Phase, and Amplitude Tracking in Aircraft Electrical Systems

An Overview of Power Electronics Techniques in Electric Systems for Transport Applications

“…Owing to the harmonic contents and measurement noise in aircraft AC power systems, variable fundamental frequency can be observed which fluctuates between 360 and 900Hz. In order to provide higher quality for the phase and frequency estimations under this circumstance, a novel PLL scheme was proposed based on a real-time implementation of the discrete Fourier transform (DFT) in [44]. Compared with a standard PLL algorithm, the proposed DFT-PLL has better dynamic performance.…”

“…Meanwhile, it is less sensitive to harmonics, noise, and signal amplitude variations. Furthermore, a robust PLL algorithm was raised by using a predictioncorrection filter in [45], which was experimentally compared with the aforementioned DFT-PLL proposed in [44]. This PLL solution is based on a third-order linear and time-invariant observation model, which is obtained from a steady-state linear Kalman filter (SSLKF), and the computation burden was mitigated since the calculation of the correction gain vector can be done offline.…”

Comparison of Two Three-Phase PLL Systems for More Electric Aircraft Converters

“…The recursive Discrete Fourier Transform [4], [5], the least error square technique [6], [7], the Kalman filter [8]- [10] are some of the most commonly used techniques, along with the wavelet transform, the PQ theory, and the neural networks. Other solutions, characterized by a lesser computational complexity, are based on Phase-Locked Loop (PLL) systems, which have been widely proposed in the literature [11]- [35] in order to obtain a robust synchronization with the supply fundamental voltage. The most common approaches [12]- [19] employ a second-order closed-loop transfer function that presents difficulties in the parameters tuning due to the trade-off between noise rejection (narrow bandwidth) and fast response (high bandwidth).…”

“…Since the performances of the SSLKF-based PLL has been already proven for standard grid-connected systems in [33]- [34], in this paper the method is experimentally compared with the phase and frequency estimation technique proposed in [35] which adopts a real-time DFT technique as the PLL phase detector. Such choice for the comparison is justified since the DFT technique has been specifically designed for aircraft power systems providing, as shown in [35], superior performances in case of variable frequency power supplies amongst other conventional PLL solutions.…”

“…Such choice for the comparison is justified since the DFT technique has been specifically designed for aircraft power systems providing, as shown in [35], superior performances in case of variable frequency power supplies amongst other conventional PLL solutions. Moreover, it is important to highlight that the most common PLL structures are designed to operate only around a rated frequency that in conventional grid-connected applications is fixed [17], [22], [24], [28] and, thus, cannot be used in case of a variable frequency supply.…”