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Abstract This paper presents a novel filtering algorithm for the resolver position signal based on recursive least squares (RLS) and phase‐locked loop (PLL). The proposed RLS‐PLL‐based algorithm designs a harmonic iterative estimation and elimination mechanism, which can accurately estimate and eliminate the specified harmonic contained in the resolver online and obtain an ideal reconstructed position signal. The convergence analysis, parameter design and pseudo code of the proposed algorithm are all provided. The advantage of the presented method mainly lies in that it has excellent position signal filtering performance in the entire operating condition, including low speed, high speed, steady state, and dynamic. Experimental results demonstrate that compared to the results achieved with the conventional look‐up table (LUT) method and the advanced type‐III angle tracking observe (ATO), the proposed RLS‐PLL‐based algorithm has improved filtering performance. Under some typical operating conditions, the harmonic content of the position signal reconstructed by the new method is reduced by an order of magnitude.

Abstract This paper introduces a novel cascading frequency regulation scheme (CFRS) for VSC‐HVDC to provide strong support for the connected weak AC grid without phase‐locked loop and remote‐communication considering the cost‐effective property. The proposed CFRS utilises a DC voltage synchronisation control to enable the self‐synchronisation of VSC‐HVDC without phase‐locked loop, while the corresponding inertia response can be exerted via utilising the stored HVDC capacitor energy. Meanwhile, the DC voltage acts as the reflection of system frequency, enabling the coordination between two‐end VSC stations without communication. More importantly, to fully utilise the VSC‐HVDC potentials, the CFRS that sequentially activates HVDC capacitor and primary frequency control is implemented so that the energy loss and the detrimental control impacts on the sending‐end systems can be minimised while making sure the requirement of system frequency support. Analytical derivations have been done to evaluate the contribution of the proposed CFRS to system frequency regulation. Furthermore, the effectiveness of the proposed scheme has been well validated in PSCAD/EMTDC under several power system contingencies by fully comparing with existing control schemes. The proposed CFRS stands out by the reduced complexity of the control structure, the robustness for connecting the very weak AC grid and the fast frequency regulation ability with consideration of cost‐effective property.

Abstract Having a robust and accurate grid synchronization unit for distributed generators (DGs) has been accentuated due to rapidly growing integration of inverter‐based DGs to the autonomous microgrids. Although most of the synchronization methods are based on the phased locked loops (PLL) technique, digital filters could result in more salient dynamic performance in non‐ideal sinusoidal situations. This paper presents a novel digital filter as a grid synchronization method that overcomes the flaws of conventional PLLs under harmonic distorted and unbalanced cases as well as large delay of window‐based digital filters. For the sake of computational advantages, the proposed method is executed in two distinct offline and online stages. In the offline stage, the second‐order Taylor series expansion approximation of the bandpass oscillatory signal calculates the state‐transition matrices and state vectors. Then, by applying the concept of Kalman filter, the state vectors are updated in the online calculation section much easier and faster compared to all‐online approach. Compared to the existing methods, the proposed method generates a dynamic response with less settling time, more accuracy, and immunity against harmonic distortion, imbalances, and noise.

Abstract Design of a low cost Schottky diode based single‐balanced mixer (SBM) in full V‐band with an ultra‐wide intermediate frequency (IF) bandwidth is presented here. By loading multiple quarter‐wavelength short‐ended stubs at both radio frequency (RF) and local oscillator (LO) frequency on the multistage stepped impedance matching networks, a broadband grounding circuit is provided for IF signal and thus output power nulls are eliminated over an ultra‐wide IF band. The hybrid network is constructed by a 3 dB branch coupler and a 90‐degree delay line, which enables the required balanced outputs with equal amplitude and 180‐degree phase difference. A prototype of the SBM is designed, fabricated and tested. Measured results demonstrate that, for RF and LO frequency over entire V‐band, the mixer has a conversion loss from 6.8 to 11.4 dB with an ultra‐wide IF range of 0.01–22 GHz.