Low-cost DSP Research Articles

IMC based robust and innovative control strategies for higher-order DC-DC converter in DC microgrid applications

The extensive practice of DC-DC converter interfacing circuits to maintain DC link voltage in DC microgrid applications introduces unavoidable voltage regulation problems due to its nonlinearity. These unregulated voltages demean the performance and result in an unstable system. This brief proposes an internal model control (IMC) non-linear approach based robust proportional-integral-lead (PI-Lead) controller design for regulating a practical fifth-order DC-DC boost converter. The main innovation of this paper is the developed procedure for designing controller. The prominent feature of IMC filter coefficient is to fulfil the desired level of gain margin and phase margin to show the trade-off between performance and robustness. The proposed controller's performance is evaluated in the presence of uncertain disruptions and its effectiveness is verified by comparing it with the some conventional proportional-integral (PI) as well as with recently published IMC-proportional-integral-derivative (IMC-PID) and IMC-proportional integral derivative double derivative (IMC-PIDD2) controllers. The applicability of the proposed control methodology has been validated under varying supply and load current levels in presence of parametric uncertainty using a MATLAB/Simulink tool along with a low-cost microcontroller DSP F280379D based laboratory prototype.

Practical Implementation of the Indirect Control to the Direct 3 × 5 Matrix Converter Using DSP and Low-Cost FPGA

The popularity of multiphase drives is increasing due to the growing interest in drives with more than three phases. One promising topology is the multiphase matrix converters, which enable the implementation of a single-stage AC/AC power conversion system with bidirectional power flow capability. In this paper, we present the implementation of indirect control for a practical sample of the direct matrix converter. To reduce the overall cost of the control solution for these types of converters, we utilized low-cost FPGA and DSP. The usage of only DSP itself was not possible due to low number of available PWM output needed for 3 × 5 MxC driving. Another reason is commutation, which must be precise and fast to avoid any hazardous states in the converter. Due to these problems, the authors decided to implement an algorithm of a combination of DSP and FPGA, where FPGA is used for time critical operations. The indirect algorithm treats the converter as two separate parts, the rectifier and the inverter, with the DC-LINK being fictitious. The matrix converter is composed of compact modules, and the entire system is verified. The practical verification demonstrates that matrix converters can produce a wide range of output frequencies and achieve input power factor control. Finally, we compare and review the practical model with the simulation model, examining efficiency and other parameters.

Optimization-Based Estimation and Model Predictive Control for High Performance, Low Cost Software-Defined Power Electronics

A combined optimization-based estimation (OBE)-model predictive control (MPC) technique is developed to improve the dynamic performance of a reconfigurable LC-based power module with lower cost and less noise/oscillation. The developed OBE-MPC technique and the corresponding power module are based on a software-defined power electronics concept that can be reconstructed as different topologies and applied to various load/source applications, e.g., dc/dc converters, dc/ac single/three-phase grid-connected inverters, and ac/ac motor traction inverter to improve the energy conversion performance. The software-defined power electronics are designed in a generalized way by manipulating a different number of OBE-MPC power modules with holistic high-level control functions for wide applications. Symmetrically mirrored to the MPC, the OBE is configured as a constrained finite time optimal estimation (CFTOE) problem to solve the quadratic cost function based on the past sampling information. With the designed OBE, the sensor count is reduced with less noise/oscillation. And the highly accurate OBE contributes to the correction of possible modeling parametric or sampling errors. The integration of OBE-MPC algorithms improves both the steady-state and dynamic performances with less noise/oscillation, more robust transient behavior, and higher control bandwidth. The explicit design of OBE-MPC algorithms makes it possible to implement the functions on a low-cost DSP. Also, the state-space modeling of OBE-MPC for the LC-based power module is immune to the output side unknown inductance, which further improves the parametric accuracy. The proposed methods have been validated experimentally.

Model predictive current control for dual-active-bridge dc-dc converter with single-phase shift modulation

This paper proposes a model predictive current control for the dual-active bridge (DAB) dc-dc converter with single-phase shift modulation. The DAB dc-dc converter model is established using the averaging method. To eliminate the steady-state error caused by model uncertainties, the integral of feedback error is combined with the state error to form the augmented system for the control design. Moreover, the controller gain can be systematically tuned by only one tuning scalar variable, making the proposed controller easy to implement. Furthermore, an offline optimization problem is used for computing the controller gain, so real-time computation burden is significantly reduced, enabling the use of low-cost DSP controller. Overshoot-free and fast convergence performance of output current can be achieved using the proposed method in simulations and Typhoon HIL emulator.

A new inductance estimator based on Lagrange Form polynomials for real-time switched reluctance machine control

This paper presents a new methodology for modeling the inductance curves of switched-reluctance machines using cubic splines based on Lagrange form polynomials. The proposed methodology allows for the estimation of the instantaneous inductance and derivative of the inductance in each phase of the machine. All steps of the proposed methodology are presented and discussed, detailing the information necessary for its use. The results of an experimental and computational simulation, both as a motor and a generator, are presented and discussed, and the estimated curves are compared with the design curves of each result. The inductance estimator was embedded in a low-cost DSP, and the machine was driven using an experimental bench. The experimental results are presented and compared with the simulation results, allowing for the evaluation of the accuracy level obtained by the proposed estimator. The estimator combines precision with low computational cost, which makes this method a strong candidate for systems that require estimation of machine parameters in real time, such as torque and flux, permitting the implementation of new control techniques.

Tuning and experimental assessment of second-order generalized integrator –frequency locked loop grid synchronization for single-phase grid assisted system

The phase-locked loop (PLL) is an essential part of the grid-tied system to synchronize control of converter with grid voltage, particularly affects the converter stability as well as performance under weak grid conditions. During abnormality in a grid, its bandwidth ought to be a11dequately brought down to achieve appropriate disturbance rejection capability with a compromise to slower detection speed. The researchers have done intended work in advanced PLLs to improve phase-angle detection speed by modifying the pre/in-loop filtering stage. A most concerning challenge with the PLLs is the means by which to additionally provide superior dynamic performance and reduced settling time without bargaining stability of system along with the capability of disturbance elimination To overcome this challenge, this paper describes the second-order generalized integrator (SOGI-Frequency Look loop (FLL) which offers filtering capability like band-pass filter, low-pass filter, and notch filter for adaptive frequency tuning as well as an orthogonal signal generation for the grid-tied photovoltaic inverter. The impact of control parameters on their dynamic performance in SOGI-FLL is tabulated from a step response of frequency estimation by taking a frequncy shift. Furthermore, Low-cost DSP based STM32F407VGT the microcontroller is employed to implement a SOGI-FLL to test under adverse grid conditions using Waijung Block-set of SIMULINK/MATLAB. The experimental results of SOGI-FLL have proven superior dynamic performance over type-2 PLLs by choosing the appropriate value of the control parameter of SOGI-FLL.

Low Cost Simple Look-Up Table-Based PMSM Drive Considering DC-Link Voltage Variation

This paper proposes a permanent magnet synchronous machine (PMSM) table-based torque control method considering a variable DC-link voltage that can be used in a low cost DSP. The current reference generation based on two-dimensional look-up table (2D-LUT) is widely used for PMSM drives used in industrial applications because of its torque control performance and operation stability. In general, a 2D-LUT is established based on the flux and torque to overcome the variation in DC-link voltage. However, this method requires a flux estimator for estimating the instantaneous flux, which is defined as a division of the operating speed used to obtain the flux data. Therefore, to obtain the operating flux, a variable division calculation or complex controller is used, which can be difficult to process through a low cost digital signal processor. In this paper, a novel look-up table-based control method that uses the newly established speed-torque 2D-LUT is proposed. This 2D-LUT inherently implements data on the d-/q-axis currents throughout the operating regions, not only the speed and torque, but also the DC-link voltage variation. The proposed method was verified through an experiment on the torque control a variation in the DC-link voltage.

Optimized OpenCL™ kernels for frequency domain image high-boost filters using image vectorization technique

Image high boost filtering uses high-boost filters to enhance the quality of an image, which has also seen in remote sensing, satellite broadcasting, classroom monitoring, and many more real-time video processing applications and requires its faster implementation. OpenCL is a widely adapted parallel programming framework that provides core level data parallelism, and dedicated for heterogeneous parallel devices like from low cost DSP to high-end CPU, GPU and FPGA. In this article, we have considered mostly used Ideal, Gaussian, Butterworth, and Laplacian of Gaussian frequency domain high-boost filters and implemented channelized OpenCL kernels for their rapid execution. In addition to that, these kernels are modified using image vectorization technique to optimize their time utilization by reducing the execution time of these OpenCL kernels to half. At last, performance analysis is carried out for these two types of OpenCL kernel implementations to determine their effectiveness with regard to time consumption and accuracy. Here, different image performance evaluation metrics like entropy, standard deviation, mean absolute error, percentage fit error, SSIM, correlation, and peak signal to noise ratio are applied to measure rightness of the above high-boost filters. From the results, we have concluded that a vectorized Butterworth high-boost filter kernel is the suitable one to provide better results among those filters, which might be highly adaptable in time bound real-time applications using various embedded devices.

Switching-Sequence Control of a Higher Order Power-Electronic System Driving a Pulsating Load

In a conventional linear-control design of a higher order power-electronic system (PES), the gains of the control laws are typically determined by small-signal analysis of the averaged model of the PES. The closed-loop control of such a PES (driving a pulsating load that periodically shifts the equilibrium) using its small-signal model is often found to be unsatisfactory with regard to the overall stability and performance. To address the challenges in control design for a PES driving such a nonlinear time-varying pulsating load, this paper delineates an optimal switching-sequence-based control (SBC) scheme, which applies stability-bound switching sequence(s) to the PES. A novel method has been formulated to ensure the reachability of the PES dynamics based on its switching sequence in terms of the time horizon of the switching sequence and the allocation of this time among the switching states of the same switching sequence. This is ascertained by modeling the PES and the pulsating load as a nonlinear map and then using this map and multiple Lyapunov functions determined by solving a set of linear-matrix inequalities corresponding to each of the switching states of a given switching sequence. It has been further shown that the knowledge of the stability bounds of a reachable switching sequence helps in reducing the online computation time for optimal SBC associated with solving the optimization problem by reducing the overall search space. Finally, to validate the optimal SBC, an experimental GaN-FET-based 100-kHz Cuk-PES has been fabricated and tested on a pulsating load. The overall SBC is implemented on a low-cost TMS320F28335 DSP, which also implements an observer to preclude the need for plurality of sensors for the higher order Cuk-PES. The overall performance of the SBC is found to be satisfactory under varied dynamical conditions.

Robust Position Sensorless Technique for a PMBLDC Motor

The main objective of this paper is to present a new mechanical sensorless control technique of a permanent magnet brushless dc (PMBLDC) motor, which relies on the speed independent H functions. Two major challenges in the sensorless operation of PMBLDC motor drive are the starting the motor and driving it from a low speed to the rated speed. A speed independent H function is used to decide the commutation instant. Due to speed independence, the commutation instant is predicted even at low speed. The H function depends only on line voltages, which makes the overall system simple and cost effective. The proposed technique does not require any analog filter circuit or any phase compensation circuit. To eliminate the commutation ripple from the line voltages, digital low-pass filters and digital phase compensators are used. This makes the system compact, simple, and cost effective. This cost-effective solution proves perfect for low-cost appliances such as fan, air-conditioner, refrigerator, vacuum cleaner, and other home appliances. The proposed algorithm is implemented on a low-cost DSP (TMS320F28377S) to justify the effectiveness of the proposed sensorless technique for wide speed variation.

In Situ Condition Monitoring of High-Voltage Discrete Power MOSFET in Boost Converter Through Software Frequency Response Analysis

The efforts for more reliable power conversion systems have been gaining momentum in recent years. The majority of the studies concerning reliability of power switches focus on the package-related failures, mainly caused by the cyclic thermal stress. The basic failure precursor for this type of stress has been identified as increased on-state resistance for power MOSFETs in the recent literature. On-state resistance monitoring during converter operation is a challenging and costly task as it requires current and voltage sensing circuits, which can block the high voltage across the switch during off-state to protect the measurement or control unit. This paper proposes a software frequency response analysis method to determine the health status of high-voltage power MOSFETs with high on-state resistance. This is achieved by analyzing and evaluating the variation in the plant model at double pole frequency using the same DSP that is used for control purposes. The proposed concept is analyzed for boost converter; however, it can be used to detect the on-state resistance variation in other types of converters operating in continuous condition mode (CCM). The proposed algorithm is embedded in a low cost DSP and experimentally verified on a dc/dc boost converter.

Simulation and Implementation of a Domestic Wind Power Generation Scheme with Improved Power Quality

An isolated wind power generation scheme with battery storage system is proposed in this work. The objective of the design is to provide a simple and robust power factor correction for domestic power generation. The unity power factor creates a resistive load across the generator terminal. A low cost DSP based single chip design is suggested for the AC-DC-AC wind energy storage system. The scheme is illustrated through simulation studies using MATLAB and a prototype of 1.8 kW permanent magnet synchronous generator, controlled by TMS320F2407 DSP. The results shows that the system provides continuous charging even at low operating speeds, with power quality improvement. A battery equalisation algorithm is added to enhance the life of acid batteries.

Enhanced software defined meter for smart utility networks

Smart metering is considered as the enabling technology for improving efficiency and resource utilization, not only in electricity, but also in gas and water distribution. A multi-utility company could exploit wired and wireless communications to make homogenous access to smart metering even in hard-to-reach locations. For this reason, several standard solutions have been proposed in the recent past, all having a common approach based on the use of narrowband and robust modulation schemes. This paper suggests the adoption of a reconfigurable and multi-core approach for implementing a smart meter capable to easily switch among different standards and various application scenarios. The basic idea is to exploit the “software defined” paradigm for the realization of the three main units of a smart meter, i.e., the communication, the time synchronization and the measurement subsystems. A prototypal platform has been developed around low-cost GPP and DSP cores, using an FPGA for the implementation of reconfigurable peripherals, without losing in generality. Some experimental results have been carried out to verify the affordability and feasibility of the proposed approach, highlighting requirements in terms of computational and memory resource needs.

Editorial Special Issue on Green Power Supplies

A traditional field for power Electronics, Power supply technology is still the key application area that covers computing, telecommunication, server, data center, industry, automobile, electric vehicles (EVs), medical, appliance, solar inverters, and so on. Recent advances have made power supplies greener than before, as they become more energy efficient, cost effective, and environment friendly. Recent development in silicon power device and in wide bandgap devices has improved power density and conversion efficiency. These emerging devices, together with improvements in topologies, cooling, and passive components, are shrinking the size. Magnetic material, passive component design, and integration have contributed to miniaturization with improved manufacturability. Digital control, with low-cost DSP and other control ICs, has advanced the overall performance significantly.

저가형 DSP를 사용하는 FMCW 레이더 신호처리부의 효율적 구현 방안

Active driving safety systems for vehicle, such as the front collision avoidance, lane departure warning, and lane change assistance, have been popular to be adopted to the compact car. For improving performance and competitive cost, FMCW radar has been researched to adopt a phased array or a multi-beam antenna, and to integrate the front and the side radar. In this paper we propose several efficient methods to implement the signal processing module of FMCW radar system using low cost DSP. The pulse width modulation (PWM) based analog conversion, the approximation of time-eating functions, and the adoption of vector-based computation, etc, are proposed and implemented. The implemented signal processing board shows the real-time performance of 1.4ms pulse repetition interval (PRI) with 1024pt-FFT. In real road we verify the radar performance under real-time constraints of 10Hz update time 키워드 : FMCW 레이더, 능동차량안전, 저가형 신호처리기, 펄스폭변조 필터 Key word : FMCW radar, Active safety system, Low cost DSP, PWM filter Received 07 March 2016, Revised 09 March 2016, Accepted 23 March 2016 * Corresponding Author Woojin Oh(E-mail:wjoh@kumoh.ac.kr, Tel:+82-54-478-7485) Department of Electronic Engineering, Kumoh National Institute of Technology, Kumi 39177, Korea Open Access http://dx.doi.org/10.6109/jkiice.2016.20.4.707 print ISSN: 2234-4772 online ISSN: 2288-4165 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/li-censes/ by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright C The Korea Institute of Information and Communication Engineering. Journal of the Korea Institute of Information and Communication Engineering 한국정보통신학회논문지(J. Korea Inst. Inf. Commun. Eng.) Vol. 20, No. 4 : 707~714 Apr. 2016

Fast Model Predictive Control for Multilevel Cascaded H-Bridge STATCOM with Polynomial Computation Time

To solve the issue of exponentially increasing computational burden of finite control set model predictive control (FCS-MPC) for multilevel converters, a fast MPC scheme for multilevel cascaded H-bridge STATCOM is presented. The proposed approach consists of three steps. First, with the partially stratified optimization approach, the multiobjective programming of MPC is divided into two suboptimization problems, i.e., current-control MPC and voltage-balancing MPC. Second, a dynamic programming algorithm is proposed for the optimization of current-control MPC. Third, a mixed algorithm, which combines dynamic programming and greedy algorithm (0-1 programing), is proposed to select the optimal switching combination from all the redundant switching combinations for the voltage balancing MPC achieving a global optimization. Through the analysis of the time complexity, with the proposed scheme, the total computation of FCS-MPC can be reduced to polynomial time from exponential time. The proposed approaches will not deteriorate the control performance. The control performance is validated by simulation results and the effectiveness is further demonstrated by implementing the algorithm on a low-cost DSP (TMS320F28335) in real time.

Coherent Nyquist UDWDM-PON With Digital Signal Processing in Real Time

Nyquist shaping UDWDM-PON combined with digital coherent optical systems has been recently proposed as a promising technology for future optical access networks. In this paper, we report real-time transmitter and receiver for a future coherent PON with high spectral efficiency and low-cost DSP implementation. Using field-programmable gate array (FPGA)-based 8-bit DSP, we experimentally demonstrate a high performance system based on 16 × 2.5 Gb/s QPSK signals in terms of receiver sensitivity and fiber transmission. An optimal transmitted power of –7 dBm per channel is achieved for 50-km standard single-mode fiber in a 2.5-GHz grid. The experimental results show the feasibility of coherent PON scenarios based on DSP supported by FPGAs.

Versatile UPQC Control System with a Modified Repetitive Controller under Nonlinear and Unbalanced Loads

A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (T_p/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Padé's approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.

Detection and suppression of parasitic DC voltages in 400V AC grids

Grid connected static power converters inject parasitic DC currents due to the offset in current sensing, control imperfections, assymetries in power switches and other secondary effects. Ever growing number of grid connected converters contributes to an increase of DC bias in AC grids, and this brings the cores of distribution transformers closer to saturation and increases their power losses. This paper provides sensitivity analysis of distribution transformers to the DC bias, and considers solutions for detecting and compensating the parasitic DC components in AC grids. Active compensation methods can be advantageously used in suppressing the DC bias at grid connection point of the power converter. The sensing approach proposed in this paper makes use of saturable ferromagnetic cores and a low cost DSP for signal analysis and processing. Proposed algorithm uses distortion of the magnetizing current of a parallel connected saturable core due to the bias. Experimental results demonstrate the capability for detecting and compensating the bias voltages far below 1 mV in 0.4 kV grids. The paper describes the principles of DC bias detection and it provides the guidelines for the proper design of magnetic components. High precision of the proposed DC bias sensing is thoroughly verified on the experimental setup connected to a 0.4 kV grid.

Robust PCA micro-doppler classification using SVM on embedded systems

In this paper a novel feature extraction technique for micro-Doppler classification and its real time implementation using SVM on an embedded low-cost DSP are presented. The effectiveness of the proposed technique is improved through the exploitation of the outlier rejection capabilities of the Robust PCA in place of the classic PCA.