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This paper presents a new current mode control using charge control concept to improve the performances of the constant on time control. These days, constant on time control is widely used in VR applications for its higher light load efficiency and higher bandwidth design capability. In this constant on time configuration, inductor current ripple based current mode control is very popular in today's...
The dual-mode photovoltaic inverter is capable of operating either in grid-connected mode or island mode, acting as a current source for the ac grid in the former and a voltage source for the load in the latter. Transitioning from one mode to the next is non-trivial and can cause large deviations in voltage, current, and frequency because a mismatch in frequency, phase, and amplitude between the inverter...
It is mandatory for grid-connected power converters to synchronize the feed-in currents with the grid. Moreover, the power converters should produce feed-in currents with low total harmonic distortions according to the demands, by employing advanced current controllers, e.g., Proportional Resonant (PR) and Repetitive Controllers (RC). The synchronization is actually to detect the instantaneous grid...
This paper presents a current dependent droop control method for equal load sharing of parallel connected inverters without any communication between them. Voltage droop in d and q axis voltage is achieved by using d and q axis currents. Each inverter works on voltage controlled mode where it controls the filter capacitor voltage. The outer voltage control loop generates current reference for filter...
The current trend in isolated microgrids is oriented to distributed renewable energy generators, such as photovoltaic (PV) generators and their corresponding distributed energy storage systems (ESS) as an unit denoted as active generator (PV+ESS). In an isolated microgrid, every distributed generator (ESS or PV) may operate in two operation modes (grid-forming or grid-following) in accordance to specific...
Power converter operation on high-impedance grids can result in oscillatory behavior as a result of “self-synchronization” of an inverter's phase detection unit (PDU). This phenomenon is particularly of concern in renewable energy applications and it occurs when the converter's injected current changes the voltage angle at the point-of-common coupling (PCC) and synchronizes to itself through its PDU...
With the more substantial large-scale wind integration projects implemented in the province of Alberta, wind power has been growing steadily in the province to meet the increasing consumer demands. Meanwhile the transmission and distribution networks are being updated to satisfy the transmission capacity. Under the transmission line and substation construction with planned transmission line outages,...
Small-signal state-space analysis of power system stability relies on linearized models where steady state operation corresponds to constant values of all state variables. Such models are available and commonly used for analysis of configurations with three-phase 2- or 3-level Voltage Source Converters (VSC). However, the Modular Multilevel Converter (MMC), which is emerging as a preferred topology...
This paper proposes to apply an instantaneous sequence estimation technique to enhance the control systems applied in distributed generation. It relies on a recursive least-square estimation of the αβ voltage components which are directly linked to the sequence components. The method was originally proposed to serve a dynamic voltage restorer controller. Here, this technique has been expanded to improve...
The Microgrid voltage may deviate from the grid voltage when it operates in islanded mode, which will result in unexpected large inrush currents during the re-connection process. This paper proposed a new self-synchronization control strategy for synchronverter with local loads which utilizes the reference phase angle of synchronverter as the reference angle in the rotating frame. A compensation quantity...
During a fault on the power grid, earthing systems operate to contain the energy keeping people and equipment safe. Unfortunately, these systems can fail and create hazards when the resistance is too high, as a result of improper design, installation or maintenance. Regular on-site testing of earthing grids is essential to prevent these situations. The most commonly used method to test earthing grids...
This paper proposes an individual-phase reactive power control strategy for an active load balancer (ALB) in three-phase four-wire distribution systems. The authors offer the simplest method to control different amounts of individual-phase reactive power for each phase on three-phase four-wire distribution feeders. The basic principle of the proposed power factor adjustable reactive power control...
A controlled power inverter can cause instability at its point of common coupling (PCC) with its input filter and the grid. Small-signal stability of such systems can be determined by applying the impedance-based stability criterion. The influence of the Phase-Locked Loop (PLL) on the output admittance of single-phase current-controlled inverters with different grid stiffness is analyzed in this paper...
Reliable rotor position/speed estimation is one of the key issues in the position/speed sensorless control of permanent-magnet synchronous machines (PMSM). In this paper, a quasi-sliding-mode observer (QSMO) with an online observer parameter adaption scheme is employed to estimate the extended electromotive force of a salient-pole PMSM. Due to machine parameter variations, inverter nonlinearities...
Fast and accurate synchronization of power electronics interfaced distributed generation to the grid or a microgrid is an important step in the management and utilization of the distributed energy resources. Several synchronization algorithms have been proposed to improve the phase tracking of the grid voltage. However, when the grid is weak or distorted, the synchronization process may suffer from...
Distributed Generation in Low Voltage grids has raised the concern of unintentional islanding and its probability has increased due to the newly introduced standards for generators, which in particular impose wider frequency and voltage ranges and active and reactive power support capabilities using of P/f and Q/V droop characteristics. Anti-islanding protections that each inverter is equipped with,...
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