Abstract
Low-cost single-phase grid connected converters require synchronization with the grid voltage to obtain a better response and protection under diverse conditions, such as frequency perturbations and distortion. Phase-locked loops (PLLs) have been used in this scenario. This paper describes a set of quadrature signal generators for single-phase PLLs; compares the performances by means of simulation tests considering diverse operation conditions of the electrical grid; proposes strategies to reduce the computational burden, considering fixed-point digital implementations; and provides both descriptive and quantitative comparisons of the required mathematical operations and memory units for implementation of the analyzed single-phase PLLs.
Highlights
In recent years, there has been a considerable increase in the presence of power converters in the electrical grid due to the diversification of sources, storage systems and loads as well as the fulfilment of the applicable standards [1]
In [44,45], the Phase-locked loops (PLLs) based on the multiharmonic decoupling cell (MHDC PLL) is proposed, where the quadrature signal generation (QSG) used is a combination of the transport delay (TD) and the IPT
Three main approaches can be found in the literature [48,49]: complex filters, which require complex and computationally expensive hardware multipliers; the combination of two filters that form 90◦, which are commonly implemented as delayed band-pass infinite impulse response (IIR) filters variables, which deteriorate PLL performance; and finite impulse response (FIR) filters, which require the real part to be delayed to adjust the relative phases of in-phase and quadrature signals
Summary
There has been a considerable increase in the presence of power converters in the electrical grid due to the diversification of sources, storage systems and loads as well as the fulfilment of the applicable standards [1]. Even though the use of self-synchronized converters in certain applications, which eliminates the need for a dedicated synchronizer, results in a simpler and more robust controller [8], in most applications, the active synchronization enables complementary functions that go beyond the basic current control functions, e.g., providing a measure of grid frequency/voltage for anti-island methods [9,10]. This is where synchronization strategies, especially phase-locked loops (PLLs), can play a key role in improving the phase and, the current reference generation.
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