###### Abstract  
With the increased grid-connected capacity of a single-phase distributed power supply, three-phase power unbalance is more likely to occur in a power grid. Three-phase power unbalance can further lead to three-phase voltage unbalance, which can have adverse effects on power quality and power supply reliability. Therefore, there is a need to build a three-phase power transmission channel to realize power exchanging among phases. In this paper, a novel grid-connected inverter control strategy for three-phase power exchanging is proposed based on constructed negative sequence current control. A completed negative sequence current control loop is added to a conventional three-bridge inverter to realize the decoupling control of three-phase grid current, and then three-phase power exchanging is realized. On this basis, this paper further puts forward a strategy for three-phase power exchanging aimed at three-phase voltage balance. Correspondingly, the three-phase grid current is controlled according to the feedback of the three-phase voltage. Then, three-phase voltage balance is achieved by three-phase power exchanging. The simulation and experimental results show that the proposed strategy is suitable for a three-phase unbalanced power grid, which can realize three-phase power exchanging, and further, can achieve three-phase voltage balance. The proposed strategy can help to improve power quality and supply reliability. g +
Footnote †: journal: Applied sciences  
bridge circuit to release or absorb reactive power. This method has a wide adjustment range and can realize a wide range of dynamic reactive power compensation, from inductive to capacitive. However, both of these static var compensation devices can only solve the unbalance problem of the low-voltage side of a three-phase distribution transformer, and are not applicable to the three-phase unbalance at the end of the line, so there are still some limitations. 3. Modify the topology structure, add extra power conversion equipment, and build an energy transmission channel among phases: The authors of [3; 4; 5; 6; 7] adopted a back-to-back (BTB) converter interconnection microgrid control, and [3; 4] further proposed a method to combine three BTB converters into a power sharing unit for power sharing and power flow control among phases of the microgrid. In addition, refs. [5; 6; 7] proposed cascaded double active bridge (DAB) converters. The transmission power of each DAB module in each phase is evenly distributed according to the three-phase unbalance of the three-phase AC power grid, so the three-phase unbalance can be alleviated. However, these methods need to add extra power conversion equipment in the microgrid, which increases the cost and reduces the reliability, and may also reduce the energy transmission efficiency due to the characteristics of the hardware equipment. 4. Decentralized control: The authors of [8; 9; 10] used decentralized control to solve this problem. For example, [8] proposed a decentralized power management and load-sharing method. This method enables the power flow between different phases to be automatically completed through the three-phase unit. In order to realize power decentralized management, the conventional active power-frequency droop is modified according to the operating states of the units, considering the available photovoltaic power and battery conditions of each unit to make each unit share the load reasonably. Other methods such as the small AC signal injection method [11] and the single-phase droop control method [12] are also typical decentralized control methods. These methods can independently and flexibly control the power and voltage regulation of each phase, and ensure the allowable output phase power, voltage distribution, and power quality. However, most of these methods rely on interlayer communication, and the communication delay may affect the system operation. 5.