Model Predictive Control Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter

Eun-Su Jun,Sang-Shin Kwak,Minh Hoang Nguyen

doi:10.1109/access.2020.3024634

Eun-Su Jun, Sang-Shin Kwak + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.3024634

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Abstract

This paper proposes a predictive control method with offset voltage injection for achieving a neutral point (NP) voltage balance of three-phase three-level neutral point clamped (NPC) inverter, without employing a weighting factor. In order to ensure the proper and reliable operation of the NPC inverter, the NP voltage balance should be regulated in addition to the sinusoidal output current. The conventional predictive control methods for NPC has suffered from tedious weighting factor selection. Besides, when the converter’s parameters value and control condition changes, it is cumbersome to empirically redesign the weighting factor. Therefore, the proposed predictive control method without the weighting factor can successfully maintain the balance of NP voltage by utilizing an offset voltage, which is determined according to the difference between the upper and lower capacitor voltages. As a result, the proposed algorithm using the offset voltage injection can control the output currents and maintain the balance of NP voltage. Simulation and experiments are presented to prove the validity of the NP voltage balancing of the proposed control method.

Highlights

The recent increase in the application of high power systems and equipment in the industrial field reveals the limitations of two-level converters [1]–[3]
The offset voltage is determined by the difference of the DC capacitor voltage
The model predictive control (MPC) (Model Predictive Control) method is a control method of controlling the converter by predicting future values using the converter model based on the fact that only a finite number of possible switching states can be made by the converter

Summary

INTRODUCTION

The recent increase in the application of high power systems and equipment in the industrial field reveals the limitations of two-level converters [1]–[3]. Jun et al.: MPC Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter capacitor voltage of three-level NPC converters were studied [15]–[17]. In [37], the author proposes a predictive control method using injected offset voltage to achieve NP voltage balance in a three-phase three-level NPC rectifier, without employing the weighting factor in the cost function. A new MPC method to control the NP voltage balance of three-phase three-level NPC inverter by offset voltage injection is proposed. When the phase difference between the reference voltage and the output current occurs, the switching state candidates are excluded to maintain the capacitor voltage balance and selected according to the capacitor voltages. Jun et al.: MPC Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter TABLE 1. The current and the capacitor voltage change according to the voltage vector selected

CONVENTIONAL MODEL PREDICTIVE CONTROL METHOD

PROPOSED NP VOLTAGE CONTROL ALGORITHM

CURRENT CONTROL ALGORITHM USING REFERENCE VOLTAGE

Findings

CONCLUSION