This paper discusses a repetitive-based controller for an uninterruptible power supply (UPS) inverter. It is shown that a bank of resonant filters, used as a refinement term for harmonic compensation in earlier works, is equivalent to a repetitive scheme with a particular structure. The latter is implemented using a simple feedback array with a delay line, thus making the implementation relatively easy. More precisely, the repetitive scheme takes a negative feedback structure plus a feedforward path whenever the odd harmonics are considered for compensation only. The repetitive scheme, equivalent to the bank of resonant filters, acts as a refinement term to reject the harmonic distortion caused by the unbalanced and distorted load current, and thus, allowing the UPS inverter to deliver an almost pure sinusoidal balanced voltage. Experimental results in a 1.5 KVA three-phase inverter are included to show the performance of the proposed controller

In this paper, the authors present a controller that directly regulates the active and instantaneous reactive power in a synchronous three-phase boost-type rectifier. The controller ensures a good regulation of the output voltage, and guarantees the power factor close to one. The controller builds upon the ideas of the well known direct torque control (DTC) for induction motors. In their case, the active and reactive powers replace the torque and flux amplitude used as the controlled outputs in DTC, thus motivating the name DPC-control. They show that a simple modification to the original algorithm makes the selection of the control inputs more accurate. To formalize this technique, they utilize the concept of output regulation subspaces. A modification is added to the basic controller to deal with disturbances such as unbalance and distortion in the source voltage. Finally, the proposed controller was tested both in simulations and experimentally, and illustrative results are presented.

This paper presents a transformerless single-phase inverter topology based on a modified H-bridge based multilevel converter. The topology comprises two legs, namely, a usual twolevel leg, and a T-type leg. The latter is based on a usual two-level leg, which has been modified to gain access the mid-point of the split DC-link by means of a bidirectional switch. The topology is referred as asymmetrical T-type five-level (5L-T-AHB) inverter. An ad-hoc modulation strategy based on sinusoidal pulse width modulation (PWM) is also presented to control the 5L-T-AHB inverter, where the two-level leg is commuted at fundamental frequency. Numerical and experimental results show that the proposed 5L-T-AHB inverter achieves high efficiency, exhibits reduced leakage currents, and complies with the transformerless norms and regulations, which makes it suitable for the transformerless PV inverters market¹.

Linear proportional-integral (PI) controllers are widely used in power converter applications. In a recent paper, a methodology to design such controllers ensuring asymptotic stability was proposed. The technique relied on the basic fact that if an affine system can be rendered passive with a constant control, then it is stabilizable with a PI. A structural condition was imposed then on the power converter to satisfy the former property with a passive output generated as a linear combination of the states. This condition is technical and has no clear physical interpretation. In this brief this result is extended in three directions: first, the aforementioned condition is removed; second, a larger class of converters (with switching external sources) is considered; third, the load resistance is assumed unknown and an adaptive PI controller (with three different estimators) is proposed. Instrumental to establish the result is the proof that the nonlinear incremental model of power converters defines a passive map-a property first observed by Sanders and Verghese in the early 1990's. The methodology is applied to the problem of power factor compensation of a 3-phase voltage source rectifier, already considered in our previous paper, which is revisited from the incremental passivity perspective yielding simpler proofs. Also, a stable adaptive PI is designed for the output voltage regulation of a quadratic boost converter. Simulations complete the brief.