This paper presents a fast selective harmonic current mitigation strategy for inverters with active power filter capabilities based on synchronous reference frames and two degrees-of-freedom internal model controllers. The advantage of this control strategy over the conventional proportional integral (PI) control solution is a significant increase in the speed of harmonic detection and mitigation. Furthermore, this control strategy reduces the computational burden when applied in a digital controller. These characteristics make this strategy desirable for applications, where fast/harmonic detection and mitigation are needed. Mathematical analysis and simulations are presented to corroborate the performance of the proposed controller strategy. Finally, the results of this proposal are verified in a 1 kW three-phase multifunctional inverter with harmonic compensation capabilities up to the 17th harmonic.

Active Power Filters (APFs) have been used for reducing waveform distortion and improving power quality. However, this function can be improved by means of a selective harmonic compensation. Since an APF has rating restrictions, it is convenient to have the option of selecting an individual or a set of particular harmonics in order to compensate and apply the total APF capabilities to eliminate these harmonics, in particular those with a greater impact on the Total Harmonic Distortion (THD). This paper presents the development of a new APF prototype based on a three-phase three-level Neutral Point Clamped (NPC) inverter with selective harmonic compensation capabilities and reactive power compensation. The selective harmonic compensation approach uses several Synchronous Rotating Frames (SRF), to detect and control individual or a set of harmonics using d and q variables. The APF includes a Three-Dimensional Space Vector Modulator (3D-SVPWM) in order to generate the compensation currents. Because of its multilevel topology, the proposed active power filter can be used in diverse power quality applications at sub-transmission and distribution voltage levels. Simulation and experimental results are shown to validate the proposed solution and assess the prototype performance in different scenarios.

Hydrogen production is an interesting alternative of storing energy. Electrolyzers produce hydrogen through water electrolysis; the resulting hydrogen is later used to generate electricity by using fuel cells, that reverse the process. Electrolyzers use rectifiers to convert the grid ac voltage into dc voltage for supplying the electrolyzer cells. Previous research used a rectification process based on conventional rectifiers (diode- or thyristor-based) which draw non-sinusoidal current from the main grid. This requires increased filtering to prevent power quality problems and equipment malfunctioning/failure. In addition, previous literature assumed simplified models for the power electronics converters and lacked a detailed control system. The Vienna rectifier is a non-regenerative converter that produces sinusoidal currents with low losses due to the reduced number of active switches. This manuscript proposes using the Vienna rectifier as an interface to connect electrolyzers to the ac grid. The dc voltage applied to the electrolyzer is regulated by using another dc-dc converter, which is selected to be a synchronous buck converter for simplicity and maximum efficiency. In this paper, the models of the Vienna rectifier, synchronous buck converter, and the electrolyzer are developed along with their respective controls. The control system has the ability to function in two operation modes for the overall reference: hydrogen production and power demand. The first one is adequate for grid-connected operation and the later for off-grid operation. Simulation results are given to show the validity of the proposed procedures.

This paper describes a methodology for the design of AC and DC filters of a VSC-HVDC system, based on mathematical calculations and simulations in Matlab Simulink ^® . The methodology is implemented in a ± 125kV and 200MW VSC-HVDC system. The 3D-SVPWM modulation technique is used to control the VSC converters of the system as a method to reduce high frequency harmonics and size reduction of the AC and DC filters.

The precise calculation of phase angle, voltage magnitude and frequency is crucial for the effective control of power electronic inverters connected to an electrical power system. The phase-locked loop (PLL) is a commonly employed method for measuring these variables. Nevertheless, the reliability of this measurement is influenced by transient events in the electrical power system and varies depending on the nature of the event and the specific design of the PLL. Notably, PLLs utilizing the double second-order generalized integrator are widely adopted for power converter synchronization purposes. This article proposes a three-phase PLL, which is based on the single-phase version previously reported by the authors. The proposed PLL, based on an alternative integrator approach, allows a fine adjustment of the tolerance to disturbances in the input voltage thanks to a second feedback gain in its pre-filter. It is reasonable to anticipate that the three-phase PLL will exhibit similar strengths to the single-phase version; however, in the three-phase case, an additional integrator is involved in pre-filtering the quadrature signals, and the double integrator is not employed as the quadrature signal generator. The performance of the proposed PLL is assessed by comparing it to other PLLs based on the second-order integrator, using a processor-in-the-loop approach.