Proportional-integral and proportional-resonant based control strategy for PUC inverters

In this paper, a proportional-integral (PI) and proportional-resonant (PR) based control strategy is proposed for packed-U-cell (PUC) inverters. In the conventional PI-PI based control strategy, while the first PI regulates the DC capacitor voltage, the second PI regulates the AC load current. However, it is shown that the second PI cannot guarantee zero tracking error in the load current. The main reason of this comes from the fact that PI controllers are not able to achieve zero tracking error for the AC signals. Also, in an attempt to reduce the tracking error by tuning PI gains distorts the load current. In this study, a PI-PR based control strategy is obtained by replacing the second PI by a PR controller. The performances of both PI-PI and PI-PR control methods have been compared. It is shown that the load current to tracks its reference in all circumstances provided that the inverter current reference is generated accurately. Computer simulations are conducted to show the steady-state and dynamic performances of both control methods

Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator

This paper presents a super twisting sliding mode control (ST-SMC) for single-phase dynamic voltage restorers (DVRs). Unlike the conventional first-order sliding mode controller, the proposed ST-SMC technique eliminates the need for differentiating the compensation voltage in the sliding surface function while keeping the merits of first-order SMC. As a consequence of employing ST-SMC, a continuous control signal is achieved from which the pulse width modulation (PWM) signals can be generated. In this case, the inverter operates at constant switching frequency. The stability analysis of ST-SMC is also presented. The reference compensation voltage needed in ST-SMC is estimated by using Brockett oscillator based frequency-locked loop. Theoretical considerations are verified through experimental results under ideal and distorted grid voltage conditions. The obtained results show that the ST-SMC has good dynamic performance and can maintain the load voltage at desired level under voltage sag, swell and harmonically distorted grid voltages

Enhanced Quasi Type-1 PLL-Based Multi-Functional Control of Single-Phase Dynamic Voltage Restorer

This paper considers the reference signal generation problem for the multi-functional operation of single-phase dynamic voltage restorers. For this purpose, a single-phase quasi type-1 phase-locked loop (QT1-PLL) is proposed. The pre-loop filter part of this PLL is composed of a frequency-fixed delayed signal cancellation method and a two-stage all-pass filter. Thanks to the frequency-fixed nature, the pre-loop filter is easy to implement and can provide rejection of any measurement offset. Moreover, this PLL benefits from the excellent harmonic robustness property of the conventional QT1-PLL. Small-signal modeling and gain tuning procedures are detailed in this paper. In order to track the reference voltage signals generated by the proposed PLL, a super-twisting sliding mode controller is also presented, which helps to achieve fast dynamic responses. Laboratory-scale prototype-based experimental studies were conducted to validate the developed reference generator and the controller. Experimental results show that the proposed method is fast in detecting and compensating any grid voltage anomalies to maintain constant load voltage despite voltage sag, swell, and harmonic distortions

An effective control algorithm for dynamic voltage restorer under symmetrical and asymmetrical grid voltage conditions

Introduction. Voltage sag, which is associated to a transitory drop in the root mean square voltage characterizing an electrical source network. During these perturbations, the corresponding electronic customers and devices will suffer from serious operating troubles causing dangerous damages. Purpose. In order to attenuate this disturbance effects, the Controlled Dynamic Voltage Restorer constitutes a very interesting solution among many others that have been proposed. The novelty of the proposed work consists in presenting an enhanced algorithm to control efficiently the dynamic voltage restorer when voltage sag is suddenly occurred. Methods. The proposed algorithm is based on an instantaneous phase locked loop using a multi variable filter to synthesize unitary signals involved in compensation voltages computation relative to the sag apparition. Practical value. A detailed study concerning typical voltage sag, which is consolidated by simulation and experimental results, is conducted to show the used algorithm’s effectiveness to cancel the corresponding voltage sag.Вступ. Провал напруги, який пов’язаний із тимчасовим падінням середньоквадратичної напруги, характеризує мережу джерел електричної енергії. Під час цих збурень відповідні споживачі (електронні прилади та інші пристрої) будуть страждати від серйозних проблем у їхній експлуатації, що спричиняють небезпечні пошкодження. Призначення. Для того, щоб послабити вплив цих збурень, контрольований динамічний відновник напруги видається дуже цікавим рішенням серед багатьох інших, які були запропоновані. Новизна запропонованої роботи полягає у представленні вдосконаленого алгоритму ефективного управління динамічним відновником напруги, коли раптово відбувається провал напруги. Методи. Запропонований алгоритм базується на миттєвому фазовому замкненому контурі з використанням багатоваріантного фільтра для синтезу унітарних сигналів, що беруть участь у обчисленні напруги компенсації стосовно прояву провалу. Практичне значення. Детальне дослідження стосовно типового провалу напруги, яке узагальнено за допомогою моделювання та експериментальних результатів, проведено, щоб показати ефективність використовуваного алгоритму для ліквідації відповідного провалу напруги

Microgrids/Nanogrids Implementation, Planning, and Operation

Today’s power system is facing the challenges of increasing global demand for electricity, high-reliability requirements, the need for clean energy and environmental protection, and planning restrictions. To move towards a green and smart electric power system, centralized generation facilities are being transformed into smaller and more distributed ones. As a result, the microgrid concept is emerging, where a microgrid can operate as a single controllable system and can be viewed as a group of distributed energy loads and resources, which can include many renewable energy sources and energy storage systems. The energy management of a large number of distributed energy resources is required for the reliable operation of the microgrid. Microgrids and nanogrids can allow for better integration of distributed energy storage capacity and renewable energy sources into the power grid, therefore increasing its efficiency and resilience to natural and technical disruptive events. Microgrid networking with optimal energy management will lead to a sort of smart grid with numerous benefits such as reduced cost and enhanced reliability and resiliency. They include small-scale renewable energy harvesters and fixed energy storage units typically installed in commercial and residential buildings. In this challenging context, the objective of this book is to address and disseminate state-of-the-art research and development results on the implementation, planning, and operation of microgrids/nanogrids, where energy management is one of the core issues