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In this paper, an extensive analysis on the influence of DC side voltage to the performance of PAPF is carried out, and a specification of the DC side voltage rated value is presented. First, through equivalent circuit analysis and Fourier Transform analytical expressions, a required lowest value of DC side voltage for full compensation (a zero source current THD) is obtained for six-pulse converter harmonic current, where PAPF is providing six-pulse converter harmonic current. For the situation, of which the DC voltage is smaller than the above-obtained lowest value, the quantitative relationship between the DC voltage and the total harmonic distortion after compensation is also elaborated in the paper by using the diagram of curve relationship. Based on these analysis, the specification of DC voltage rated value for PAPF is quite straight forward. Simulation investigation results are finally provided to verify the analysis and specification.

In this paper, based on two cascaded bidirectional Buck/Boost Dc-Dc converters, stability issue in the bidirectional converter cascaded system is revealed. With Middlebrook impedance criterion, two minor loop gain, each for one power flow direction and which is defined as the ratio of the upstream converter output impedance to the downstream converter input impedance, are introduced for the system stability analysis. Time-domain simulation and mathematic calculation are done for the verification. Based on the analysis results, two conflicts in the bidirectional converter cascaded system are proposed. One is that with the shared common part in the power stage, it cannot easily optimize the system stability in both power flow directions. The other conflict is that in many cases with the shared common compensator in control stage, it cannot optimize the system stability in both power flow directions at the same time. By revealing these two conflicts, this paper proposes that the corresponding consideration and tradeoff should be done during the design stage.

Suitable model for the analysis and control of the shunt active power filter (APF) was quite difficult to obtain, which prohibited not only the industrial applications, as no generalized method to design the control loop, also the analysis and comparison between existing control methods. In this paper, a simplified shunt APF model, including the steady state model and small signal model, based on the instantaneous energy equilibrium is proposed. Subsequently, the newly built model is used to analyze two popular control methods in detail, as the shunt APF control with or without the reactive and harmonic current detection, in the DC voltage control loop responses to different load current disturbances. The obtained results are compared with the time domain simulation results for the control method with the reactive and harmonic current detection, the differences for them are found as the time delay caused by the low path filter (LPF) in the detection, the control and the whole system model is improved by considering this effect, and the comparisons on the responses to different current disturbances are evaluated for these two control methods accordingly. Finally, an example of the shunt APF control loop design is done based on the new model in the control method without reactive and harmonic current detection, the computer simulation and the prototype experiment are done to verify the validity of this newly designed compensator accordingly.

Three-level NPC inverter has been put into practical use for years especially in high voltage high power grid. This paper researches three-level active power filters(APF). In this paper the mathematical model in d-q coordinates is presented for 3-phase 3-wire APFs. The dead-beat control scheme is obtained by using the state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state predictor. The delay of one sampling period is remedied in this digital control system by the state predictor. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve better prediction of the harmonic current with same sampling frequency, thus improves the overall performance of the system. The experiment results indicate that the steady-state accuracy and dynamic response are both satisfying when the proposed control scheme is implemented.

This paper extends the efforts on behaviorally modeling dc-dc power stages to modeling three-phase converters. By equating both the Y- and delta-connection of three-phase sources/loads to a new connection mode, which is suitable for calculating the generated/consumed power, this paper proposes the power transfer model respectively for three-phase boost rectifiers and three-phase voltage source inverters (VSI). The consistency between the proposed models and those previously published for dc-dc converters is discussed. The proposed models can find their applications in simulating multiple-module interconnected power supply systems.