This paper proposes a control strategy of a three-phase five-level double converter for induction motor drives. The converter consists of the five-level rectifier, the dc link, and the five-level inverter. In this control strategy, the five-level rectifier fixes the DC link voltage at low value in the low-speed area and increases it in proportion to the motor speed in the high-speed area. The method will redress the imbalance of the generated losses at switching devices in the five-level inverter and reduce the generated losses. The performance of the control strategy is verified by experiment.

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The two-dimensional (2D) communication is a novel physical form of communication that utilizes the surface as a communication medium to provide both data and power transmission services. To efficiently transmit a relatively-large amount of electric power (several watts), we have developed a 2D communication system that concentrates the electric power on a specific spot by using phase control of multiple inputs. However, to find the optimal phases of the multiple inputs making the microwave converge on a specific spot in the 2D sheet, the prior knowledge of the device's position, and/or the pre-experiment measuring the output power, are needed. In wireless communication area, it is know that the retrodirective array scheme can efficiently transmit the power in a self-phasing manner, which uses the pilot signals sent by the devices. In this paper, we apply the retrodirective array scheme to the 2D communication system, and propose a power transmission scheme using the phaseconjugation of multiple inputs. To confirm the effectiveness of the proposal scheme, we evaluate its performance by computer simulation and realistic measurement. Both results show that the proposal scheme can achieve the retrodirectivity over the 2D communication system.