Search

Advantages of microgrid integrated with a renewable energy system have been acknowledged in more and more applications. Operating steadily during different modes is of great significance, and different modes transferring must be transient, seamless, and reliable to maintain the continuous electricity supply for loads, especially sensitive ones. As a semicontrolled switch that is unable to shut instantly until the zero point of its current, thyristors should be forced to be turned off by certain strategies to minimise the influence brought by the delay of modes transferring. In this paper, a compulsory turn-off strategy based on fuzzy logic control of converter output voltage is proposed. With the strategy, an alterable reverse voltage is applied across the conducting thyristor by dynamically adjusting the output voltage reference instruction and closed-loop control parameters depending on the changing rate rather than detecting the polarity of voltage or current. Constraints from acquisition of analog data and error of digital calculation will be eliminated. Finally, simulation and experimental results verify the effectiveness of the proposed strategy.

The purpose of this paper is to propose and implement a novel rotor position detection method for permanent magnet synchronous machines (PMSMs) based on linear Halls, which are embedded inside of stator of PMSMs. A three-phase 9-slots/8-poles PMSM is exampled to verify the method. Firstly, a special point located in stator yoke (back-iron) is found by two-dimensional finite element analysis (2D-FEA), where the open-circuit flux-density due to permanent magnets versus rotor position (BPM) shows a high amplitude and good linearity, while the armature-reaction flux-density (Barmature) due to armature currents exhibits a low amplitude and good linearity versus armature currents. Then, an analytical model is built and the analytical relationship between armature currents and the Barmature is derived. Based on the analytical mode, BPM can be obtained by separating the Barmature from the synthetic magnetic field (BSynthetic). Thereafter, the resultant BPM can be used to detect the rotor position information with differential-type piecewise-linear analytical method. The feasibility of the proposed detection method is verified by co-simulations and experiments. The simulation results show that the novel linear Hall-based angle sensor can achieve the accuracy equivalent to 3000-line. The experimental results indicate that compared with an encoder, the maximum error of electric angle position at different speeds is less than 0.3%.

A static synchronous compensator (STATCOM) with a delta configuration is able to compensate for reactive currents, unbalanced currents and harmonic currents in a three-phase three-wire system. A method is proposed for balancing the harmonic currents among three phases of the STATCOM without affecting line harmonic currents injecting into the grid. The rating of the STATCOM can be lower because the maximum phase current is reduced. Simulation and experimental results are provided to show the effectiveness of the proposed method.

The paper analyzed the defects and causes of shunt APF and serial APF when they are used to suppress the distortion in load current or in source voltage separately. It also introduced the operation principle of unified power quality compensator (UPQC), which is able to compensate for both the source voltage and load current at the same time. The paper proposed the reference criteria comparison detection method for voltage distortion, dq0 detection method for current distortion and PI control strategy for stabilizing the voltage of DC capacitors. Simulation result verified the correctness of analysis and the effectiveness of UPQC design.

Filters are used to implement signal transforms, and filter design is a very important part of the signal processing field. There are currently 2 types of filters available: the finite impulse response (FIR) filter, and the infinite impulse response (IIR) filter. While FIR filters have desirable traits such as stability (an absence of poles), IIR filters are able to generate outputs more efficiently. This paper combines the two types of filters by introducing an output slope trigger, to make a hybrid impulse response (HIR) filter with desirable traits from both FIR and IIR filters

Filters are used to implement signal transforms, and filter design is a very important part of the signal processing field. There are currently 2 types of filters available: the finite impulse response (FIR) filter, and the infinite impulse response (IIR) filter. While FIR filters have desirable traits such as stability (an absence of poles), IIR filters are able to generate outputs more efficiently. This paper combines the two types of filters by introducing a zero-counter, to make a hybrid impulse response (HIR) filter with desirable traits from both FIR and IIR.