This paper provides a control methodology for a single-phase synchronous inverter which enables the inverter to implement dynamic characteristic of synchronous machines directly. As one of solutions for the power system instability due to penetration of renewable energy sources, a concept of virtual inertia has been proposed. Many previous researches on this field employed the voltage and current feedback controller to realize ideal behavior based on theoretical mass model of synchronous machines. However, a controller including the multiple feedback loops has difficulty in optimizing control parameters. The non-optimized controller with lead or lag at frequency of the rotational mass cannot achieve the designed dynamic characteristic. We develop a controller that realizes direct implementation of a swing equation as well as protection of the inverter from the overcurrent. The numerical simulation demonstrates that the proposed controller does not disturb the dynamic characteristic of the synchronous inverter and enhances the grid stability.

In order to constitute the resilient power system against disturbances including natural disaster, various new technologies for microgrid operations have been proposed recently. Although major Renewable Energy Sources (RESs) are usually connected to single-phase feeders, there exist few research works on single-phase microgrid operations. This paper investigates the realization of the single-phase microgrid by using Voltage Source Converters (VSCs) which are widely used to connect DC-base RES systems to conventional distribution feeders. We first study effective virtual inertia design in three-phase VSC in order to realize strong synchronizing operation as well as the enhancement of transient stability. Then, we propose a control framework for single-phase VSC, in which a new synchronizing mechanism that we call DC side measurement is developed. A governor and an Automatic Voltage Regulator (AVR) are also implemented into the controller to contribute to stable and reliable operation of the microgrid. It is shown that the independent use of the proposed VSC in each phase can also work successfully in a three-phase feeder. The effectiveness of the proposed method is verified in numerical simulations in single-phase and three-phase distribution systems where multiple VSCs are successfully operated in normal and islanding modes.

This paper provides a convincing argument for assessing effectiveness of a pseudo-synchronizing power inverter by experimental study using a real inverter and real multiple synchronous machines. Since the renewable energy sources are being rapidly introduced to the power system, synchronous machines will be forced to stop in order to balance the supply and demand. The implementation of virtual inertia into power electronics devices are well known as one of effective ways to stabilize the power system with few synchronous machines. In previous researches including some studies by authors, the theoretical and simple experimental studies for pseudo-synchronizing power inverter have been already examined. To realize stable power system by introducing the pseudo-synchronizing power inverter, however, further realistic experimental analysis seems to be necessary. In the context of the realistic experimental study, we construct a small scale and realistic power system with multiple synchronous machines, two-line transmission lines with a fault simulation system, and a real inverter. The inverter is controlled by gate signals from a digital signal processing board (PE-Expert 4) which generates the signals so that the inverter has the synchronizing power virtually. It can be seen from the experimental results that the proposed pseudo-synchronizing power inverter can successfully work even in the realistic experimental power system.

SUMMARY: The liberalization movement in Japan will be expanded to the residential sector and full liberalization of the retail market will be achieved in the near future. Against this background, it is expected that transactions in a distribution network (DN), which has many consumers of the residential sector, will be activated. Furthermore, consumers can control their loads depending on the selling prices offered by retailers with the introduction of demand response (DR) technologies such as home energy management systems (HEMS). Due to the variation of load by DR, however, the voltage profile in DN may be changed compared to the present situation. This may make voltage management difficult and cause problems such as voltage deviation from an adequate range. In this paper, the impact of DR in a liberalized electricity market on DN is evaluated for efficient voltage management. In order to evaluate the behavior of the retailer and consumers, this paper proposes a bi‐level programming approach based on the Stackelberg game model. Solving the bi‐level programming problem including the power flow equation for a DN model based on the IEEE 13‐bus test feeder, we analyze the impact of the retailer and consumers on the voltage in the DN in order to account for transactions between these market players.