# A Two-Grid Interline Dynamic Voltage Restorer Based on Two Three-Phase Input Matrix Converters
###### Abstract  
Energy quality problems can cause diverse failures of sensitive equipment. Dynamic voltage restoreers (DVRs) are devices that have been proposed to protect sensitive loads from voltage sag effects. However, the compensation capacity of DVRs is limited by the amount of energy stored in the restorer. One way to overcome this limitation is to use the interline DVR (IDVR) structure in which two or more DVRs connected to different feeders share a common DC-link. This paper proposes a new IDVR topology based on two three-phase input matrix converters (TTI-MC) without a capacitor in the dc-link. The TTI-MC integrates the power from two feeders and synthesizes the dc-link voltage. The inverters take the dc-link voltage and generate the appropriate compensation voltages to keep the load voltages stable. Each one of the inverters has its own modulation algorithm which are synchronized with the TTI-MC control. Inverter control is carried out in the reference frame \(dq\) and a modified space vector pulse width modulation (MSV-PWM) technique is used. TTI-MC control is performed in the \(dq\) reference frame with proportional-integral controllers and the modulation is based on the carrier-based pulse width modulation (MCB-PWM) technique. The proposed Two Input Interline DVR (TI-IDVR) extends its compensation range and has multifunctional capabilities. The efficiency of the proposed TI-IDVR is corroborated by simulations on MATLAB/Simulink. carrier-based pulse width modulation (MCB-PWM); interline dynamic voltage restoreer (IDVR); matrix converters (MC); power quality (PQ); space vector modulation (SVM) +
Footnote †: journal: Applied Sciences  
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Due to the importance of DVRs in the mitigation of disturbances in electrical grids, different topologies and control strategies have been developed to improve their performance [7; 8; 9; 10]. The compensation range of DVRs has also been extended to provide multi-functional capabilities [11; 12]. Other studies include the use of Matrix Converter (MC) in the topology of DVR [12; 13; 14]. While DVRs are widely used in mitigating voltage disturbances, their ability to compensate for long-term and deep voltage sags is limited due to the amount of energy stored in the same DVR structure. To overcome this limitation, a type of DVR called an interline DVR (IDVR) [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25] has been developed. The IDVR is a system that consists of several DVRs that protect sensitive loads on different feeders in the distribution grid and share a common dc-link (Figure 1). When one of the DVRs of the IDVR system compensates for a voltage sag, it takes energy from the dc-link. At the same time, the other DVRs fill the energy dc-link to keep its voltage at a specific level. An example of a potential application of this scheme is in a custom power park (CPP) [26; 27; 28; 29; 30] where power is provided by multi-feeders (i.e., different power supplies connected to different network transformers); in this way, they are electrically separated. Sensitive loads in these parks can be protected by DVRs connected respectively to their load. The dc-links of these DVRs can be connected to a common terminal, thus forming the IDVR system. This can reduce the cost of the energy storage system. Sharing a common dc-link substantially reduces the size energy storage device of the dc-link compared to a system in which loads are protected by independent DVRs with separate energy storage systems. The IDVR provides a way to dynamically replenish the energy available in the energy storage device of the dc-link. However, the compensation capacity of the IDVR depends largely on the load power factor [17; 18; 19; 20].