Andrzej Sikorski

Current controller reduced switching frequency for VS-PWM inverter used with AC motor drive applications

The current control system of the three-phase voltage source inverter used in AC motor drive application is presented in the paper. This system, operating in the rotating reference frame fixed to the motor flux, minimizes the switching frequency inverter transistors. The optimal inverter output voltage vector positions, recorded in an electrically programmable read-only memory, ensure the longest path of moving the stator current vector inside the tolerance band which is square shaped. Theoretical bases for the choice of optimal inverter output voltage vector positions are discussed.

A new DTC control for PMSM with torque ripple minimization and constant switching frequency

Purpose – The aim of the paper is to conduct an analytical study of the two new methods of the permanent magnet synchronous motor torque and flux direct control with the predictive non‐linear torque and flux controller.Design/methodology/approach – The method is based on the prediction of the torque and flux error vector in order to minimize the torque ripple and ensure the constant switching frequency.Findings – The proposed methods ensure the torque and flux error vector minimization, reduction of the torque ripples, and constant switching frequency without deterioration of the dynamic properties of the standard direct torque control (DTC).Originality/value – An innovative predictive DTC method is presented. The correctness of the analysis and main assumptions, as well as the expected final results have been verified in simulation.

New DPC Look-Up Table Methods for Three-Level AC/DC Converter

This paper presents new look-up table methods for a three-level ac/dc converter supplied from the grid. The nonlinear direct power control (DPC) method, by reason of its drawbacks resulting from the omission of grid inductance voltage drop, has been improved in the DPC-δ 5 × 2 method by rotating the orientation of coordinates by angle δ, i.e., the angle between grid voltage vector and set converter voltage vector. The other proposed development involves further improvement of the DPC-δ 5 × 2, into which a new optimal division of the current error plane is introduced. The new optimal voltage vector assignment allows us to choose a converter voltage vector using the modified error current vector. The proposed look-up table methods have been tested and compared applying the following criteria: current error, total harmonic distortion (THD) of input current, average transistor switching frequency, and response time on step changes of set current. The experimental results validate the proposed control schemes and show good system performances that were verified according to above criteria.

Predictive control of the AC/DC converter

In this article a new, predictive control method of the AC/DC converter is presented. The method is based on the Direct Power Control algorithm and current error vector minimization criteria. Key assumptions of the predictive DPC-3V algorithms are presented. The correctness of the analysis has been confirmed by laboratory results.

Comparison of new DPC methods for two- and three-level AC/DC converters

The paper briefly describes and compares some new methods of Direct Power Control of a two- and three-level AC/DC converter. The basis for comparing the methods was the equality of switching energy losses in each of the methods.

Dead-time compensation in a new FCS-MPC of an AC/DC converter with a LCL filter

The article presents Finite Control Set Model Predictive Control for an AC/DC converter with a LCL filter. The extended cost function J is responsible for the adjustment of controlled values. An important issue raised in the article is the impact of dead time on the prediction of controlled values. The negative impact of dead time results in an increased THD of the grid current. The article proposes an algorithm correcting the impact of dead time which was confirmed by the results of Matlab-Simulink simulations and laboratory tests.

Improved Algorithms of Direct Torque Control Method

In the paper a new way of DTC control method analysis to explain flux and current distortion at a low speed of motor operation is discussed. As a result, a new DTC-δ algorithm is proposed. It is important that the DTC-δ algorithm uses the same switching table as the DTC method. The modified DTC algorithms are free from the disadvantages of the conventional DTC method i.e. hexagonal flux and strongly deformed current at a low speed range. The dynamical properties of the new algorithms are similar to the conventional DTC method. The correctness of the proposed methods has been confirmed by laboratory investigations.

Advanced Control Methods of DC/AC and AC/DC Power Converters—Look-Up Table and Predictive Algorithms

This chapter is devoted to a modern look-up table and predictive control methods of three phase power electronic converters. The authors consider voltage source converters in two and three level configurations as well as a two level current source rectifier. Some of the methods concern DC/AC inverter fed induction and PMSM motors. The other methods described in this chapter are dedicated to the control of the AC/DC rectifier working as an Active Front End of an AC/DC/AC converter. The authors focus on the methods with a non-linear look-up table and predictive control due to their excellent dynamic properties (limited only by the physical parameters of controlled systems such as the value of the DC voltage, grid inductance or AC motor leakage inductance). Moreover, non-linear methods, especially the predictive ones, provide very good quality of control in steady states, i.e. lack of active and reactive power steady-state error (AC/DC) or torque error (in the case of DC/AC converters). Look-up table methods have been taken into consideration as they also ensure the above advantages in a relatively short calculation time. The selected look-up table and predictive methods are proposed for both 2-level and 3-level converters. All the described control methods have been illustrated by simulation results and laboratory tests confirming their characteristics.

Finite Control Set Model Predictive Control for Grid-Connected AC–DC Converters With LCL Filter

This paper presents two new implementations of finite control set model predictive control (FCS-MPC) methods applied to ac–dc converters with an inductive.capacitive.inductive (LCL) filter. The LCL filter, despite its advantages, can cause a strong resonance in the grid current and also pose a substantially more complex control problem. The new solutions improve the FCS-MPC with an active damping algorithm by eliminating low-order grid current harmonics and decreasing sensitivity to grid voltage distortion. The new methods, i.e., PCi1i2uc and PCi1i2uc-2steps propose multivariable approaches using converter-side current, line-side current, and capacitor voltage. Another improvement involves extending the prediction horizon in PCi1 i2uc-2steps. Both methods have been tested and compared in steady and transient states as well as under grid voltage disturbances. The methods were also compared with a predictive control algorithm with active damping. The simulation results and experimental measurements validate the developed control schemes and show high quality of grid current (low THDi value), high dynamic performance, and immunity under distorted grid voltage conditions.

Predictive control of current source rectifier

The paper presents a new predictive control strategy of current source rectifier (CSR) supplied from the grid. The algorithm chooses proper space vector of CSR according to the predicted value of the grid current and predicted value of the capacitor voltage. Proposed method is analyzed for different L and C values and their influence on higher harmonics reduction has been discussed. Simulation results confirm good performance of the system.