Abstract
Active and reactive power regulation, unbalanced current compensation, and harmonic current mitigation are the most significant functionalities typically embedded to a three-phase multifunctional grid-connected inverter. However, a vital control feature minimally addressed in the literature is the capability to adjust the grid power factor to the minimum value required by standards or grid codes. Hence, this paper presents an adaptive compensation approach to perform dynamic power factor regulation under varying power demand and unpredictable energy generation, also withstanding non-ideal voltage conditions. To demonstrate such an approach, a global power factor definition is first introduced, being validated upon bidirectional power flow conditions and under unbalanced and distorted voltages. Secondly, a simple algorithm is devised to attain scaling coefficients used on compensation purposes, allowing to instantaneously weigh up reference control signals to track a desired grid-side power factor value. As a result, the strategy can be used to retrofit the controllers of grid-connected inverters with little effort, limiting distribution losses and improving power quality. Simulations and analyses of a representative real study case are conducted to illustrate how the proposed approach copes with unpredictable distributed energy resources and variable load demands. Moreover, experimental results considering a grid-connected inverter prototype are shown to validate the feasibility of the control approach to real-life implementations.
Highlights
As the integration of distributed energy resources (DER)into power grids incessantly grows, it is highly important to understand the potential benefits of such perspective to both electricity suppliers and end-users [1]-[4]
A different approach of that used on conventional active power filters (APF) is needed for adaptive compensation, where the compensation task is performed based on ancillary actions of the multifunctional grid-connected inverter
A three-phase three-wire circuit was adopted for experiments, to the circuit presented in Fig. 3. considering a 22.5 kVA grid-connected inverter, line impedances, and a four-quadrant AC voltage source that emulates the grid
Summary
Into power grids incessantly grows, it is highly important to understand the potential benefits of such perspective to both electricity suppliers and end-users [1]-[4]. Facility operators have reported detrimental effects and recurrent failures of power factor correction passive solutions [18]-[21] These problems are caused by local or general resonance conditions excited by harmonics currents generated by time-varying nonlinear loads (modern facility loads) such as AC/DC static converters, adjustablespeed drives, frequency inverters, soft starters, arc and induction furnaces, welding machines, electric traction systems, static and rotary compensation and others. The compensation is adaptable according to changes in the level of PQ disturbances or according to the level of active power injection Such an approach allows concurrent analysis and design of partial compensation strategies to improve the grid-side power factor, allowing to meet whichever standard or utility criteria is established
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