Abstract
This paper presents the design of a decoupled linear control strategy for a Dynamic Voltage Restorer (DVR) that utilizes a Matrix Converter (MC) as its core element and obtains the compensation energy directly from the power system. This DVR is intended to cope with power quality problems present in supply system voltages such as balanced and unbalanced variations (sags and swells), and harmonic distortion. The dynamic model of the complete system that includes the Matrix Converter, the input filters and the electrical grid, is performed in the synchronous reference frame (dq0), to have constant signals at the fundamental frequency, in order to design the proposed linear control strategy. The coupling in the dq components of the system output signals caused by the Park Transformation, is eliminated by a change of variable proposed for the controller design, giving rise to a decoupled linear control. In this way, the strategy developed makes it possible to establish an adequate transient response for the converter in terms of convergence speed and overshoot magnitude, in addition to ensuring closed-loop system stability under bounded operating conditions. Unlike other proposals that utilize complex modulation strategies to control the MC under adverse conditions at the input terminals, in this case, the ability to generate fully controllable output voltages, regardless of the condition of the input signals, is provided by the designed linear controller. This allows the development of a multifunctional compensator with a simple control that could be of easy implementation. In order to verify the performance of the control strategy developed, and the effectiveness of the proposed DVR to mitigate the power quality problems already mentioned, several case studies are presented. The operational capacity of the MC is demonstrated by the obtained simulation results, which clearly reveals the capability of the DVR to eliminate voltage swells up to 50% and sags less than 50%. The compensation limit reached for sags is 37%. In relation to compensation for unbalanced voltage variations, the DVR manages to reduce the voltage imbalance from 11.11% to 0.37%. Finally, with regard to the operation of the DVR as an active voltage filter, the compensator is capable of reducing a THD of 20% calculated on the supply voltage, to a value of 1.53% measured at the load terminals. In the last two cases, the DVR mitigates disturbances to a level below the criteria established in the IEEE standard for power quality. Results obtained from numerical simulations performed in MATLAB/Simulink serve to validate the proposal, given that for each condition analyzed, the MC had succesfully generated the adequate compensation voltages, thus corroborating the robustness and effectiveness of the control strategy developed in this proposal.
Highlights
Power quality is a concept that has acquired great relevance because it can be utilized to evaluate the adequate performance of current power systems
This paper proposes a Dynamic Voltage Restorer (DVR) based on a Direct Matrix Converter operated by a decoupled linear controller, the parameters of which are estimated based on the mathematical model
It should be considered that for this analysis, the compensation voltage is taken from the failed system, so if the system voltage drops to 50%, only that value is available to inject the missing voltage at load terminals, which limits the compensation level to sags less than 50%, since the Matrix Converter (MC) limited voltage ratio and the losses in the converter and filters must be considered
Summary
Power quality is a concept that has acquired great relevance because it can be utilized to evaluate the adequate performance of current power systems. In relation to research works involving the operation of a voltage compensator, in [21] applying this decoupling strategy in the conventional DVR, the design of a linear controller is achieved, which allows it to have an adequate dynamic response by mitigating the disturbances Considering these results, it is concluded that by modeling the converter in the dq0 reference frame, and using a decoupling strategy for the system components, it is possible to develop a linear control technique capable of controlling the operation of the MC under adverse operating conditions at its input terminals, without requiring the operation of a complex modulation algorithm. Component 0 is neglected because the MC mathematical model considers only line voltages
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