Abstract
A predictive control method using injected offset voltage to achieve neutral point (NP) voltage balance of three-phase three-level neutral point clamped (NP) rectifiers, without employing a weighting factor, is proposed in this study. One of the biggest problems with the three-level NP rectifiers is the dc link capacitor voltage imbalance. Therefore, it is necessary to maintain the balance of the NP voltage in addition to synthesize the three-phase sinusoidal input current by control methods. Conventional predictive control methods for the NP rectifiers have used a weighting factor in a cost function that determines the control ratio of the input currents and the capacitor voltage balance. As a result, it is burdensome to empirically redesign the weighting factor when the rectifiers’ parameter values and control conditions change. Unlike the conventional methods, the proposed approach without the weighting factor can significantly eliminate differences between two DC capacitor voltages by utilizing an offset voltage, which is generated by using the difference between the upper and lower capacitor voltages. Consequently, the proposed approach using the offset voltage injection can control the input currents and retain the balance of NP voltage. Simulation and experiments are presented to verify the correctness of the NP voltage balancing of the proposed control method.
Highlights
A recent increase in applications of high voltage systems and equipment in industrial fields has revealed limitations of two-level rectifiers [1,2,3,4]
Rectifiers for consists of two neutral terms for the input current and the capacitor voltage, which are adjusted by a weighting factor point (NP) voltage balance of three-phase three-level neutral point clamped (NP) that rectifiers is determines a control ratio between two terms
In addition to the reference voltage v∗x for the reference current tracking in (22), a new reference voltage proposed in this paper is defined with an offset voltage injection as vx.re f = v∗x + vo f f set (x = a, b, c) where vx,re f and vo f f set are a new reference voltage proposed in this paper and an offset voltage to be injected to maintain the capacitor voltage balance, respectively
Summary
A recent increase in applications of high voltage systems and equipment in industrial fields has revealed limitations of two-level rectifiers [1,2,3,4]. Select an optimal switching state minimizing a cost function to satisfy rectifier performance, have this paper addresses a to predictive method eliminate this been investigated control thecontrol. A predictive method with offset voltage injection achieving current generation and the NPcontrol voltage balancing, a cost function for the NP rectifiers for consists of two neutral terms for the input current and the capacitor voltage, which are adjusted by a weighting factor point (NP) voltage balance of three-phase three-level neutral point clamped (NP) that rectifiers is determines a control ratio between two terms. The by the difference between the upper capacitor voltage and lower capacitor voltage, in addition to proposed algorithm using the offset voltage injection can control the input currents and retain the produce a reference voltage which is used to control the three-phase sinusoidal input currents. Validity of the proposed Control method isMethod verified through simulations and experiments
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