## 1 _Editorial_
### 1.1 _Applied_  
_sciences_  
_The continuing trend toward greater electrification in consumer, commercial, industrial, and transportation applications promises a dynamic and increasingly important role for power electronics. The term 'power electronics' refers to electric and electronic circuits whose primary function is to process energy. The growing penetration of power electronics in energy systems requires attention, with its principal challenges being cost reduction and reliability. Power electronic systems are indispensable parts of modern engineering applications, covering a wide range of engineering branches._  
_This Special Issue of_ Applied Sciences _entitled \"Electric Power Applications\" includes 16 published papers, confirming the scientific community's interest in this area. The topics of interest for the call included modern applications of electricity, power electronics converters, electric motor drives, renewable energy systems, power filters, distributed power, and power grid equipment. A summary of the contributions in this Special Issue can be found below._  
_In_ _[_1_]__, a current closed-loop control strategy based on an improved QPIR (quasi-proportional integral resonant) controller is presented for a three-phase LCL grid-connected inverter. The proposed controller enables the independent control of active power and reactive power without coupling between the_ \(\alpha\) _axis and_ \(\beta\) _axis in a two-phase static coordinate system. Compared with traditional controllers, the improved QPIR control strategy has higher grid-connected current control accuracy under the condition of stable and fluctuating grid frequencies while also showing a good dynamic response._  
_Since the number of distribution terminal units (DTUs) integrated in power systems is gradually increasing, it is necessary to reduce the fault incidence of DTU devices and improve the efficiency of fault elimination. This was the aim in_ _[_2_]__, where the authors propose a DTU fault analysis method using an association-rule-mining algorithm. The practicality of the method is demonstrated by experiments using a realistic DTU fault database, allowing for the conclusion that DTU fault incidence can be reduced, and fault elimination ability can be enhanced._  
_The authors of_ _[_3_]_ _explored the simultaneous operation of the imbalance-netting process (INP) and the cross-border activation of regulating reserves (CBRR), proposing a function for correction power adjustment to prevent undesirable simultaneous activation. Extensive dynamic simulations were carried out in a testing system with three control areas to evaluate the impact on the frequency quality, load-frequency control, and performance. The results confirm that the simultaneous operation of the INP and CBRR reduces the balancing energy and decreases the unintended exchange of energy, thereby improving load frequency and performance._  
_The authors of_ _[_4_]_ _developed an adaptive and scalable protection coordination (ASPC) system for overcurrent relays (OCRs) in distributed-generator-integrated distribution networks consisting of two performance stages. The first stage determines the min-max confidence interval of the fault current for different fault types, while in the second stage, three common algorithms (Particle Swarm Optimization, the Gravitational Search Algorithm, and a genetic algorithm) are used to find the optimal setting parameters of the OCRsthat satisfy all the coordination constraint conditions. A real 22 kV distributed-generator-integrated distribution network was used as a testbed to validate the relay coordination results obtained by the ASPC system. The influence of an inverter-interfaced distributed generation (IIDG) unit's response during transmission network faults is analyzed in [5]. An improved power-based fast fault current (FFC) concept is proposed to adjust fault current injection according to the required active and reactive power.