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The transition from centralized grid control towards distributed and cellular control requires new methods and intelligent solutions for power generation, storage and transmission. Due to temporary occurrence of reversed power flow during low load conditions in distribution grids, the grid voltage may reach or may exceed voltage limits. Data centers and telecom facilities, which are equipped with...
In this paper, a new distributed cooperative control for voltage unbalance compensation in an islanded microgrid is proposed. In order to decrease the negative impacts of impedance of distributed lines upon conventional negative-sequence reactive power-conductance droop control, a cooperative control component is added to accomplish the trade-off between the accuracy of negative-sequence reactive...
The paper presents an overview about operation and control of the inverter-interface generation units (IGUs) when connected to a microgrid either alone or together with other generation units. The following key connection paradigms are considered: i) one IGU and a grid, ii) one IGU and one machine-interface generation unit, iii) a single IGU, and iv) two IGUs. After illustrating how the IGUs operate...
Recent design trends for induction heating appliances are leading to higher power burners that offer unprecedented performance levels to the user. However, this evolution is usually constrained by the maximum power that can be drained from the mains, which is usually limited by the maximum current per phase. To overcome this limitation, the design of multi-phase converters is tackled to increase the...
Using the conventional look-up table-direct power control (LUT-DPC) strategy with its two-level hysteresis comparators and conventional switching table, poor regulation of active power (abnormal fluctuations appeared in reactive power waveform), non-sinusoidal input currents with a little high THD and depressed power factor are obtained. This study therefore set out to solve these problems; the conventional...
In distributed generation and modern smart grids, the voltage source inverter (VSI) is commonly used as a basic interface between the different power sources and devices. The control capabilities of the VSI are very essential in transforming the passive distribution network into an active one. In this frame, the modeling, control and stability analysis of a VSI, standing as an interface between a...
Micro-grid systems are based on distributed energy resources (DERs) for example wind, solar etc., energy storage devices and scattered loads that can perform islanded as well as grid-connected operation. The concept of micro-grid has brought a paradigm shift from large scale centralized power generation to Distributed Generation (DG). It has reduced the dependence on main electricity grid and enables...
Voltage magnitudes in transmission power systems must be kept within the limits defined by regulatory agencies for safe operations. Thus, this paper proposes an approach to determine and apply a sequence of adjustments to control the voltage magnitude in such systems. The adjustments follow two methodologies based on a reduced Jacobian matrix (Jqv) of the system power balance equations. Computational...
This paper is focused on the performance and limits of the boost rectifiers with unity power factor, in terms of the total harmonic distortion factor of the current drawn from the power supply. Different values of the prescribed output voltage are taken into consideration. The direct current control based on the output of voltage controller is proposed. The case study of a battery charging station,...
Energy balancing of the alternate arm converter (AAC) takes place during the overlap period, when a circulating current flows through both arms of the converter. In this paper, the limitations of the commonly used energy balancing methods of the AAC under grid imbalances are demonstrated. It is shown that the overlap control can only provide sufficient energy balancing for a relatively limited voltage...
Distributed generation (DG) is connected through three-phase inverter to the microgrid. The virtual power based droop control can guarantee the pure decoupling between active and reactive power irrespective of low-voltage or high-voltage microgrid application if the line-impedance information is known in advance. However, unbalances are commonly existent in practice so that this conventional control...
The three-phase direct matrix converter has been researched exclusively as a direct AC/AC converter, being a competitive alternative to the conventional AC/DC/AC converter. Other possibilities of the matrix converter such as AC/DC, DC/AC and DC/DC conversion still remain unexplored. This paper firstly explores these possibilities and puts forward a concept of the versatile converter. With one matrix...
A novel virtual voltage control strategy is proposed for modular multilevel converter in order to reduce the quantity of voltage sensors at the terminal. The output voltage of the inverter is obtained through the upper and lower arm currents of the converter and used to trace the reference active and reactive power, respectively. According to the Routh-Hurwitz criterion, the root trajectory of the...
It is well-know that in systems composed of several digital processors, clock signals of individual units differ from each other due to clock drifts. This paper investigates the effect of clock drifts from voltage source inverters (VSI) in industrial microgrids. Particularly, a primary/secondary droop-free distributed control scheme is considered in order to evaluate its robustness against clock drifts...
Cascaded H-bridge converters based islanded microgrids are applied to integrate the distributed generators (DGs). The accurate load sharing is an important task for the research of microgrids. Due to the characteristics of series connection, all DGs share a single common current. In this paper, the power factor of each DG is assigned to be consistent via regulating both the frequency and voltage....
Microgrid cluster as an interconnected system of multiple AC subgrids and DC subgrids, its complex structure increases the difficulty of power coordination control for it. To address this issue, a microgrid cluster structure and its autonomous coordination control strategy are proposed in this paper. The proposed microgrid cluster structure is composed of AC subgrids, DC subgrids, power exchange unit...
Modular multilevel converter (MMC) is one of the recent developed converter for high power applications. However, the major drawback of this converter in variable speed drives is that the capacitor ripple voltage increases at lower speed, when the load torque remains constant. This ripple voltage can be reduced by reducing the dc-bus voltage at lower speeds, while the capacitor voltages are maintained...
Distributed diode rectifier units have been proposed as a robust and cost efficient solution for the connection of large off-shore wind farms to HVDC links. However, since the diode rectifier platforms are connected in series with cables of varying distances, their dc-side voltage might not be the same in all diode rectifier platforms. This paper introduces a diode rectifier platform dc-voltage balancing...
In this work, three-phase single stage grid-connected photovoltaic system using current control inverter is simulated using Matlab/Simulink. To deal with varying irradiance conditions, the incremental conductance MPPT has been used, however in order to improve the power quality a three-level (NPC) inverter based SVM control together with LCL filter has been used. The main result of the project is...
In this paper, a predictive direct power control (P-DPC) strategy for a three level NPC rectifier under ideal grid voltage is proposed, discussed and applied. With the proposed P-DPC strategy, the control targets are the active power, the reactive power and the neutral potential voltage; neither hysteresis comparators nor switching table are needed; sinusoidal input current with low total harmonic...
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