N. Berbel

Decentralized control for parallel operation of distributed generation inverters using resistive output impedance

In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an ac-distributed system is proposed. This paper explores the resistive output impedance of the parallel-connected inverters in an island microgrid. The control loops are devised and analyzed, taking into account the special nature of a low-voltage microgrid, in which the line impedance is mainly resistive and the distance between the inverters makes the control intercommunication between them difficult. In contrast with the conventional droop-control method, the proposed controller uses resistive output impedance, and as a result, a different control law is obtained. The controller is implemented by using a digital signal processor board, which only uses local measurements of the unit, thus increasing the modularity, reliability, and flexibility of the distributed system. Experimental results are provided from two 6-kVA inverters connected in parallel, showing the features of the proposed wireless control

Simple Low-Cost Hysteretic Controller for Single-Phase Synchronous Buck Converters

This paper presents a simple low-cost control architecture for low-voltage hysteretic regulators supplying loads with low-to-medium current consumption. Only two sensed voltages, a passive filter network and a hysteretic comparator are required to implement the main control functions: the output voltage regulation and the adaptive voltage positioning. This paper also shows that other previously reported low-cost control solutions have an important design tradeoff between load transient response and efficiency. In the proposed controller, the closed-loop output impedance can be designed to be resistive and the switching frequency can be adjusted to be independent of the output impedance requirement so that the load transient response and the efficiency can be optimized separately. Experimental results validate the performance of the proposed controller (i.e., a load transient response with insignificant output voltage overshoot and selectable switching frequency independent of the output impedance requirement).

Droop Control Method with Virtual Output Impedance for Parallel Operation of Uninterruptible Power Supply Systems in a Microgrid

In this paper, a novel droop control scheme applied to distributed UPSs forming a microgrid is proposed. The control architecture consists of two levels of hierarchy: 1) the P/Q droop control method of every UPS unit and 2) the management of the microgrid through the control of the setpoints of the units and the intelligent switch connected to the strong grid. This second level of control let us to connect or disconnect the microgrid to the utility mains, resulting in two scenarios: grid-connected and islanding operation mode. Also, it is taken into account the seamlessly transition between both operation modes, the possibility to share power with the utility grid, and the energy management of the overall system.

Decentralized Control for Parallel Operation of Distributed Generation Inverters in Microgrids Using Resistive Output Impedance

In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an AC-distributed system is proposed. The paper explores the resistive output impedance of the parallel-connected inverters in an island microgrid. The control loops are devised and analyzed taking into account the special nature of a low voltage microgrid, in which the line impedance is mainly resistive and the distance between the inverters makes the control intercommunication between them difficult. In contrast with the conventional droop control method, the proposed controller uses resistive output impedance, and as a result a different control law is obtained. The controller is implemented by using a DSP board, which only uses local measurements of the unit, thus increasing the modularity, reliability, and flexibility of the distributed system. Experimental results are provided from two 6 kVA inverters connected in parallel, showing the features of the proposed wireless control

Droop control method for the parallel operation of online uninterruptible power systems using resistive output impedance

In this paper, a novel wireless load sharing controller for parallel connected online UPS inverters is proposed. As opposed to the conventional droop method, the proposed method achieves stable steady-state frequency and phase and an good dynamic response is obtained. A virtual output impedance is proposed in order to reduce its line impedance impact and to properly share nonlinear loads. Experimental results are presented from two 6-kVA UPS inverters controlled by DSP boards, showing the feasibility of the proposed approach

Control of Line-Interactive UPS Connected in Parallel Forming a Microgrid

In this paper, the control strategy for an overall microgrid is presented. The control has two main levels: (i) the droop control of the inverters, and (ii) the control of the static bypass switch, and the droop settings for the management of the power flow. Thus, a flexible microgrid is obtained to operate in either grid-connected or islanded mode. Results from line- interactive UPS inverters connected in parallel forming a microgrid are presented, showing the feasibility of the presented solution.

One-cycle control for the parallel operation of synchronous buck converters

This paper presents a novel control for a multiphase dc-dc converter, which provides tight output voltage regulation, fast transient response, and robustness against large-signal disturbances in the input-voltage and the load-current.

Analysis, design and practical evaluation of an input-output linearization controller for the CLL-T dc-dc resonant converter

This paper introduces a dynamic study for the DC/DC CLL-T resonant converter operating with self-sustained oscillating modulation. The study includes the development of a suitable averaged large-signal dynamic model and the design of a nonlinear feedback controller that uses the sliding motion principles and the input-output linearization approach. The combination of the proposed controller and modulation type provide zero-voltage-switch operation over a wide load range, narrowed regulating frequency range and fast transient response. Experimental results are reported to validate the theoretical statements

Feedback linearization control with average current sharing for multiphase synchronous buck converter

This paper presents a novel control for a multiphase dc-dc converter, which provides tight output voltage regulation, fast transient response, and robustness against large-signal disturbances in the input-voltage and the load-current

Simple feedback linearizing controller to reduce audiosusceptibility and load disturbance in the full-bridge current doubler synchronous rectifier

The full-bridge converter with current-doublet synchronous rectifier (FB-CDSR) is a promising topology to implement low-voltage high-current power supplies. This paper proposes a novel control for this converter, which provides the following features: fast transient response, fixed switching frequency, and high robustness against large-signal disturbances in the input-voltage and the load-current. Furthermore, this controller avoids the use of any current sensor and can be implemented by means of cheap analog circuits, which highlights its low-cost and simplicity. The parallel operation of several HB-CDSR is also discussed Finally, experimental results are provided in order to show the validity of the proposed control technique