Cristian Garcia

Predictive Current Control With Instantaneous Reactive Power Minimization for a Four-Leg Indirect Matrix Converter

This paper presents the experimental validation of a predictive current control strategy with minimization of the instantaneous reactive input power for a Four-Leg Indirect Matrix Converter (4Leg-IMC). The topology includes an input matrix converter stage, which provides the dc voltage for a four-leg voltage source converter (VSC) output stage. The VSCs fourth leg provides a path for the zero sequence load current. The control technique is based on a finite control set model predictive control (FCS-MPC) strategy, whereby the switching states for the input and output converters are selected by evaluating a predictive cost function. This results in a simpler approach than that seen in other well-known modulation methods, such as three-dimensional space vector modulation (3D-SVM). Positive dc voltage, (a requirement for the safe operation of the IMC) and minimization of the instantaneous input reactive power are obtained, while maintaining good tracking of the load reference currents. Furthermore, soft switching is achieved by synchronizing the state changes in the input stage with the application of zero voltage space vectors in the inverter stage. The control strategy is experimentally verified using a laboratory prototype.

Predictive torque control of a multi-drive system fed by a six-leg indirect matrix converter

This paper proposes a predictive torque and flux control for a multi-motor drive system. The scheme is based on a six-leg indirect matrix converter used to drive two induction machines operating at the same speed under different load torque conditions. By using a mathematical model of the converter and machines, the proposed control scheme selects the switching state that minimizes error in the torque and flux predictions according to their reference values. Through simulation results it is shown that the predictive approach can be easily implemented with a good tracking of the controlled variables to their respective references, verifying the fast dynamic response with a good torque tracking conditions and flux regulation in both machines.

A simple predictive voltage control method with unity displacement power factor for four-leg indirect matrix converters

While the known modulation and control techniques for four-leg matrix converters are based on pulse width modulation or three-dimensional space vector modulation, this paper presents a finite control set model predictive control strategy with a prediction horizon of one sample time to control the four-leg indirect matrix converter. An LC output filter is connected between the converter and the load. The four-leg indirect matrix converter is developed to deliver power to the unbalanced/nonlinear three-phase loads and it can produce three output voltages independently with one additional leg. The proposed voltage control strategy is based on prediction calculation to select the switching states of the converter. By using a predictive cost function, the optimal switching state to be applied to the next sampling time is selected. This is done in order to obtain unity displacement power factor in the input side and a positive dc-link voltage at any time, while maintaining a good tracking of the load voltages to their respective references. The feasibility of the proposed strategy is verified by simulation results.

Full Predictive Cascaded Speed and Current Control of an Induction Machine

This paper presents and experimentally validates a new control scheme for electrical drive systems, named cascaded predictive speed and current control. This new strategy uses the model predictive control (MPC) concept. It has a cascaded structure like that found in field-oriented control or direct torque control. Therefore the control strategy has two loops, external and internal, both implemented with model predictive control. The external loop controls the speed, while the inner loop controls the stator currents. The inner control loop is based on Finite Control Set Model Predictive Control, and the external loop uses MPC deadbeat, making full use of the inner loops highly dynamic response. Experimental results show that the proposed strategy has a performance that is comparable to the classical control strategies but that it is overshoot-free and provides a better time response.

Predictive current control of a four-leg indirect matrix converter with imposed source currents and common-mode voltage reduction

This paper presents a new control strategy for a four-leg indirect matrix converter that effectively mitigates common-mode voltages and gives optimal control of source and load currents. This method uses the commutation state of the converter in the subsequent sampling time according to an optimization algorithm given by a simple cost function and a discrete system model. The control goals are the regulation of the output current according to an arbitrary reference and tracking of the source current reference, which is imposed in order to obtain sinusoidal waveforms with low distortion. The technique is enhanced by a reduction of the common-mode voltage using an extra term in the cost function to reduce early motor winding failure and bearing deterioration. Simulation results are presented to support the theoretical development.

Finite control set model predictive control of a Stacked Multicell Converter

Multilevel converters are an attractive alternative for medium voltage applications. The Stacked Multicell Converter (SMC), in particular, is a multilevel converter that allows to increase the output voltage level compared with the classical Flying Capacitor Converter, while decreasing the stored energy in the converter. This paper presents the application of Finite Control Set Model Predictive Control (FCS-MPC) in a three phase SMC with two cells and two stacks. The strategy controls simultaneously the load currents and capacitor voltages. simulation results show that the FCS-MPC strategy produces an effective control of the load current, while keeping balanced capacitor voltages. In addition, it is demonstrated that FCS-MPC outperforms Phase Shifted Pulse Width Modulation with linear controllers in transient and steady state operation.

The challenges of predictive control to reach acceptance in the power electronics industry

Model Predictive Control (MPC) has emerged as a very attractive alternative for the control of electrical energy. This paper discusses the challenges faced by (MPC) to reach industrial acceptance. Some of these issues are operation with fixed switching frequency and simple calculation of the weighting factors. The main conclusions are that the algorithm must remain simple and must demonstrate that it brings operating advantages in comparison to the classical linear control with Pulse Width Modulation. These problems have not been solved yet.

Cascaded predictive speed control

This work proposes a new control scheme for electrical drives system, named cascaded predictive speed control (PSC). The strategy seeks to maintain the simplicity of the classic predictive control while excluding linear or other controllers. The control strategy has a cascade architecture, similar to the techniques of classical control (FOC or DTC). The outer loop controls the speed of the machine, determining a reference torque through a mechanical dynamic model, which allows tracking the speed reference. The inner loop controls the stator current with a cost function that selects the state of the converter which generates the best tracking references for the stator current synchronous components. Preliminary simulation results confirm the effectiveness of this approach, which produces produces a high quality drive control.

A Very Simple Strategy for High Quality Performance of AC Machines Using Model Predictive Control

This paper presents a new and very simple strategy for torque and flux control of ac machines. The method is based on model predictive control and uses one cost function for the torque and a separate cost function for the flux. This strategy introduces a drastic simplification, achieving a very fast dynamic behavior in the controlled machines. Experimental results obtained with an induction machine confirm the drives very good performance.

Modulated model predictive control with optimized overmodulation

Finite-set model-predictive control (FS-MPC) has many advantages, such as a fast dynamic response and an intuitive implementation. For these reasons, it has been thoroughly researched during the last decade. However, the waveform produced by FS-MPC has a switching component whose spread spectrum remains a major disadvantage of the strategy. This paper discusses a modulated model-predictive control that guarantees a spectrum switching frequency in the linear modulation range and extends its optimized response to the overmodulation region. Due to the equivalent high gain of the predictive control and to the limit on the voltage actuation of the power converter, it is expected that the actuation voltage will enter the overmodulation region during the large reference changes or in response to load impacts. An optimized overmodulation strategy that converges toward the FS-MPC ’s response for large tracking errors is proposed for this situation. This technique seamlessly combines PWM’s good steady-state switching performance with FS-MPC ’s high dynamic response during large transients. The constant switching frequency is achieved by incorporating modulation of the predicted current vectors in the model-predictive control of the currents in a similar fashion as the conventional space-vector pulsewidth modulation is used to synthesize an arbitrary voltage reference. Experimental results showing the proposed strategy’s good steady-state switching performance, its FS-MPC -like transient response, and the seamless transition between modes of operation are presented for a permanent magnet synchronous machine drive.