Table of contents monday, September 9, 1: 30pm-4: 00pm modular Multi-Level Converters, hvdc, and dc grids I 3
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- Bu səhifədəki naviqasiya:
- Modeling and Control of DC-DC Converters I
- Modulation Techniques I
- Model Predictive Control of Power Converters
- Reluctance Machines
| 10:35AM Control of Neutral-Point Voltage in Three-Phase Four-Wire Three-Level NPC Inverter Based on the Disassembly of Zero Level [#717]
Chenchen Wang, Xiahe Si and Hongliang Xin, Beijing Jiaotong University, China The neutral-point voltage balancing problem is a key issue for three-level three-leg neutral-point clamped (NPC) inverter used in three-phase four-wire system. In this paper, a detailed discussion on this issue and a mathematical model for the neutral-point voltage fluctuation are given. Then a novel neutral- point voltage control strategy based on the disassembly of zero level is proposed. To balance the neutral-point voltage, a variable which can depict the disassembly margin of each phase, named neutral point control margin (NPCM) is defined. The duty ratio of zero level in the phase selected on the basis of NPCM is decomposed to positive and negative level equivalently in order to balance the neutral-point voltage while the average value of the output voltage is preserved unchanged. Furthermore, the relationship between the proposed control strategy and the existing method based on 3-D space vector modulation (3DSVM) in a-b-c coordinates is analyzed. It is showed that the proposed control strategy is superior in simplifying the algorithm and improving the control performance compared with the 3DSVM method. The proposed control strategy is verified by simulation and experiment. Modeling and Control of DC-DC Converters I Tuesday, September 20, 8:30AM-11:00AM, Room: 102C, Chair: Johann Walter Kolar, Juan Rivas-Davila 8:30AM Observer-based Nonlinear Control for Frequency Modulated Dual-Active-Bridge Converter [#1231] Duy-Dinh Nguyen, Manh-Linh Nguyen, Tuyen Nguyen-Duc and Goro Fujita, Shibaura Institute of Technology, Japan; Tokyo University of Sience, Japan This paper proposes a nonlinear control system based on a nonlinear observer to manage the active and reactive power within a single-phase-frequency- modulated Dual-Active-Bridge DC/DC converter directly. It is accomplished by employing a nonlinear controller to regulate the direct and quadrature current, id(t) and iq(t), as they are directly proportional to two power components, respectively. A nonlinear observer is designed to detach two current components from the average absolute value irec,avg of the transferred current. Since irec,avg is a DC quantity, very high sampling frequency is not required allowing to use the popular DSP, such as TMS320F28335, for processing. Experiment results show that the performance of the observer is fine when the converter operates under soft-switching condition which is achieved by assigning a positive value for the quadrature current iq(t). Under such condition, the amplitude error is in the range of 1% while the absolute load angle error is less than 2 degrees in the scale of 360 degrees for one switching cycle . In term of control stability, id(t) and iq(t) are well regulated by the nonlinear controller at any desired values. 8:55AM Novel Control Architecture for Dual Output DC-DC Converter Driving DC-AC Inversion System [#140]
To interface low-voltage dc-output power sources to ac grid, the split dc-bus dc-ac inverters driven by step-up isolated dual-output dc-dc converters can be a solution. When the split dc-bus dc-ac inverter is loaded with single-phase ac or unbalanced three-phase ac, current ripples will propagate through the dc-dc converters at frequencies that are related to the ac side fundamental. For the dc-dc converter close-loop voltage regulation to be robust against the disturbance introduced by those low frequency current ripples, a novel control architecture is proposed. In this paper, a combined control structure for dual-output dc-dc converters with common mode (CM) and differential mode (DM) compensation loops are presented. Simulation and experimental results have been provided for validation. 9:20AM Dynamic Bus Voltage Control for Light Load Efficiency Improvement of Two-stage Voltage Regulator [#794]
The two-stage 48V-12V-1.8V Voltage Regulator Module (VRM) structure is gaining more and more attention in high-end server applications. The LLC converter is the preferred choice for the first conversion stage because it provides the isolated 12V output efficiently, which is then converted to 1.8V by the multi-phase Buck converter. Since the CPU works in sleep-mode most of the time, the light load efficiency is very important for energy saving. This paper proposes to change the primary side of the LLC converter from the full-bridge configuration into the half-bridge configuration dynamically in the light load condition, so that the output of the LLC DC Transformer (DCX) can be changed from 12V to 6V. This will increase the overall light load efficiency significantly due to the reduced core loss of the LLC DCX and the reduced switching loss of the multi-phase Buck converter. To achieve a fast transition of the bus voltage between 12V and 6V, the capacitance for the intermediate bus is properly selected and the Optimal Trajectory Control (OTC) for transition between the full-bridge and half-bridge is proposed. A high-efficiency, high-density 48V-12V/6V LLC DCX is designed, and experimental results on the two-stage VRM demonstrate that there is a fast transient response and a more than 10% light load efficiency improvement. 9:45AM A Novel Large-Signal Stability Analysis Approach Based on Semi-Tensor Product of Matrices With Lyapunov Stability Theorem Using for DC-DC Converters [#1245]
Due to the nonlinearity of DC-DC converters,small-signal methods do not guarantee the stability of DC-DC converters under any large-signal disturbances. In this paper,semi-tensor product of matrices with Lyapunov stability theorem is firstly adopted for analyzing the large-signal stability of DC-DC converters. A buck converter with proportional-integral (PI) controller is used as an example. Based on the Lyapunov stability theorem and the state equation of the buck converter, a positive definite Lyapunov function including a nonlinear integral of type Lurie is adopted in this paper. Moreover, the large-signal stability criteria of the buck converter, namely, the condition for ensuring the negative definiteness of the derivative of the Lyapunov function is obtained based on semi-tensor product of matrices. Finally, simulation and experimental results are given to verify the correctness of the large-signal stability analysis approach based on semi-tensor product of matrices with Lyapunov stability theorem. 10:10AM A Study on the Control Loop Design of Non-Isolated Configurations for Hybrid Storage Systems [#1159]
This work focuses on the control strategies for different configurations of Non-Isolated Hybrid Energy Storage Systems. Basic strategies are proposed, studied and compared. Parting from the standard parallel connection of bidirectional boost converter in hybrid storage systems, a comparison with alternate topologies is presented. These alternative schemes overcome the problems that arise in the original configuration due the high mismatch in voltage ratings of the individual storage systems. A strategy to design the control loops of the resulting Hybrid Energy Storage System is proposed, studied, simulated and experimentally implemented on a 1.5 kW demonstrator. The control strategy is implemented in the standard bidirectional boost converter approach and also in the series-parallel connection of the storage units. The reported results show how the proposed control strategy applied to the series parallel connection presents a good performance in terms of dynamic and steady state operation. 10:35AM Effects of Non-Ideal Compensators for the High-Bandwidth Low-Standby-Power Computer V-Core Converter Applications [#576]
The stringent requirements on both the control bandwidth and the supply standby current make it tough to design the IC controllers for the v-core converters in future computer applications. The effects of the non-ideal characteristics of the finite gain-bandwidth product and non-zero output impedance of an operational amplifier (OP) are investigated for such a purpose. The results show surprising behavior, including the possibility of generating new complex poles and a positive zero in the compensator gain transfer function. That may affect the converter feedback stability margin. Increasing the OP bandwidth performance may alleviate this problem but that is usually achieved at the expense of supply standby power which is increasingly a critical consideration. The results developed in this paper allow better optimization of the OP used in a controller IC. Several commonly-used compensator types are analyzed. Simulations and experimental results are used for verification. Two practical DC converter examples are used for illustration. Modulation Techniques I Tuesday, September 20, 8:30AM-11:00AM, Room: 102E, Chair: Suman Debnath, Liliana de Lillo 8:30AM A Unified SVM Algorithm for Lifetime Prolongation of Thermally-Overheated Power Devices in Multi-Level Inverters [#1687] Mokhtar Aly, Gamal M. Dousoky, Emad M. Ahmed and Masahito Shoyama, Kyushu University, Japan; Minia University, Egypt; Aswan University, Egypt This paper presents a unified space vector modulation (SVM) algorithm for lifetime prolongation of thermally-overheated power semiconductor devices in multilevel inverters. Thermal overheating is the main cause of shortenedlifetime and open-circuit faults of the devices. Power semiconductor devices are subjected to thermal overheating due to their ageing that results from continuous overloading and power cycling. Moreover, thermal overheating in high power devices may result from its degradation and faults in the cooling system. When a thermal overheating is detected in one of the power devices, the proposed algorithm is applied to relieve the overheated device and dangerous circumstances are avoided as a result. The proposed algorithm relies on using the redundancy property between switching states in multilevel inverters to continuously evaluate a cost function of the junction temperature of thermally-overheated device for all possible switching sequences set, then it identifies the optimal relieving switching sequence. The proposed unified SVM is general that can be applied to any multilevel inverter, and also is valid for switching devices, as well as DC-link capacitors. The proposed algorithm has been designed and validated by simulation and experimental prototypes of three-level T-type inverter. 8:55AM Pulse-Width Modulation Strategy in Double-Delta Sourced Windings [#410]
A topology, so called, Double-Delta Sourced Winding(DDSW) has been proposed to improve harmonic properties in highpowerconversion systems. In this paper, a pulse-width modulationmethod is proposed to further optimize the harmonic properties inDDSW-based systems. Specifically, it is described throughmathematical analyses how to modify voltage references forreducing harmonics in combination with DDSW. The effectivenessof the proposed method is assessed with experimental results. As aresult, the proposed method revealed 40% further reduction ofharmonic current. 9:20AM A Quasi-Periodic Modulation Strategy to Mitigate EMI for a GaN-based Quasi-Z-Source DC-DC Converter [#13]
Wide-bandgap (WBG) switching devices, such as gallium nitride (GaN), enable switching at high frequencies with low rise and fall times. This provides advantages such as high power density and compact size, however a potential unwanted side-effect is increased electromagnetic interference (EMI) because of large transient currents. A novel quasi-periodic modulation scheme is described for voltage-fed quasi-Z-source (qZS) DC-DC converters which substantially reduces the peak EMI. The driver logic required is simple and generic, and therefore adaptable to all modulation schemes proposed to date for isolated qZS DC-DC converters. Various experimental results verify the effectiveness of the proposed strategy in terms of voltage gain, efficiency and EMI suppression. 9:45AM A General Space Vector PWM Scheme for Multilevel Inverters [#1214]
This paper proposes a new general space vector pulse-width modulation (SVPWM) scheme for multilevel inverters with any voltage levels. The proposed SVPWM scheme calculates the duty cycles and switching states based on the modulation triangle quickly identified through a simple coordinate transformation; no prestored memory-consuming lookup table or time-consuming iterative calculation is required. Therefore, the proposed general SVPWM is computational efficient. Simulation and experimental results are provided to validate the proposed SVPWM scheme. 10:10AM Suppression of Common Mode Circulating Current for Modular Paralleled Three-phase Converters based on Interleaved Carrier Phase-shift PWM [#619]
Circulating current has been the major concern for the implementing of paralleled converters. Extensive studies have been conducted in reducing the circulating current with different modulation strategies. However existing methods are either suffering from poor performances or too complicated for implementation. This paper proposes an interleaved carrier phase-shift (ICPS) PWM to reduce the peak value of the high frequency common mode circulating current (HF- CMCC). The proposed method can be used in the system with arbitrary number of VSCs, which makes the method very suitable for modular design. In addition, the ICPS PWM is very simple for implementation. Theoretical analysis is presented in this paper to explain the effectiveness of ICPS PWM on CMCC peak value reduction. The proposed method has been verified and compared with the interleaved SPWM (ISPWM) in simulation and experiment. 10:35AM Modulation Strategies for Three-Phase AC-DC Matrix Converters: a Comparison [#1199]
The matrix converter rectifier is an AC-to-DC converter that can be considered for emerging applications, related to smart grids and renewable energy production. The most attractive characteristics of this converter are the simultaneous control of the input power factor and the output voltage, and the small volume of the input capacitors. In this paper, after a small review of the modulation techniques, several modulation strategies are experimentally compared in terms of power losses and THD of input and output currents. Model Predictive Control of Power Converters Tuesday, September 20, 8:30AM-11:00AM, Room: 202D, Chair: Po-Tai Cheng, Petros Karamanakos 8:30AM Constrained Long-Horizon Direct Model Predictive Control for Power Electronics [#787] Petros Karamanakos, Tobias Geyer and Ralph Kennel, Technical University of Munich, Germany; ABB Switzerland LTD., Corporate Research, Switzerland The direct model predictive control (MPC) problem for linear systems with integer inputs, such as many power electronic systems, can be formulated as an integer least-squares (ILS) optimization problem. However, solving this problem when state and/or output constraints are explicitly included is challenging. In this paper, a method that allows to effectively use the sphere decoder---even in the presence of the aforementioned constraints---is proposed. This is done by computing a new hypersphere based on the feasible control input set, as defined by the imposed state/output constraints. A variable speed drive system with a three-level voltage source inverter serves as an illustrative example to demonstrate the performance of the proposed algorithm. 8:55AM Thermal-based Finite Control Set Model Predictive Control for IGBT Power Electronic Converters [#1086]
Thermal cycling is one of the main sources of aging and failure in power electronics. A possibility to reduce the thermal stress of semiconductors is to control the losses occurring in the semiconductor devices with the target to reduce the thermal cycles. This approach is known as active thermal control. The hardest limit of the existing active thermal control approaches is that they do not offer a general framework where the optimal switching sequence is selected in order to fulfill the applications demand and reduce the thermal stress in specific semiconductors. The goal is to achieve the minimum thermal stress for the best possible overall performance. For this purpose finite control-set model predictive control (FCS-MPC) seems the optimal approach because it allows including of non-linear thermal and lifetime related models into the control law. A precise control of the thermal stress in the semiconductors can be achieved as the optimal switching vector is directly applied to the physical system. This allows to avoid overrating of the used module or to increase its lifetime. In the paper the approach is proven using simulation and experimental results. 9:20AM Modulated Model Predictive Control for Active Split DC-bus 4-leg Inverters [#1697]
This paper proposes a Predictive Control, formally Dead-Beat (DBC), for a four-leg inverter having an Active Split DC-bus on the fourth leg and LC filters on phase-to-neutral outputs. Such a configuration permits to reduce the voltage ripple on the neutral point connected to inverter grounding. As only few control techniques have been investigated for Active Split DC-bus, the paper proposes to investigate the performance of DBC, which has been widely used for other power electronics applications. The main advantage of DBC over the classical PI or Resonant controller is that no tuning is required for control loop, while obtaining very fast transient response as well it can handle general constrained nonlinear systems with multiple inputs and outputs in a unified and clear manner. These features are highly valuable in power electronic converters used to supply the electrical utility loads in micro-grids. However, one of the main drawback of the DBC is the limited capabilities on harmonics compensations required when supplying unbalanced and non-linear loads. The paper presents continuous-time and discrete-time models of DBC applied to a four-leg VSI with Active Split DC-bus, highlighting the performance through simulation results as well as experimental tests. 9:45AM Computationally Efficient Sphere Decoding for Long-Horizon Direct Model Predictive Control [#785]
In this paper we present a computationally efficient implementation of the sphere decoder, which is employed to solve the integer least-squares (ILS) problem underlying direct model predictive control (MPC) for power electronic applications. The introduced modifications take advantage of the structure of the problem and, as a result, the required real-time operations can be reduced to a minimum. The efficacy of the developed algorithm is demonstrated with a variable speed drive system with a three-level voltage source inverter. 10:10AM Fixed Frequency Finite-State Model Predictive Control for Indirect Matrix Converters with Optimal Switching Pattern [#1170]
Finite States Model Predictive Control (MPC) has been recently applied to several converters topologies for the many advantages it can provide such as fast dynamics, multi-target control capabilities, easy implementation on digital control board and capability of including constraints in the control law. However, its variable switching frequency and lower steady state waveform quality, with respect to standard control plus modulator systems, represents a limitation to its applicability. Modulated Model Predictive Control (M2PC) combines all the advantages of the simple concept of MPC together with the fixed switching frequency characteristic of PWM algorithms. In particular this work focuses on the Indirect Matrix Converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M2PC design. This paper proposes an M2PC solution, suitable for IMC, with an optimal switching pattern to emulate the desired waveform quality features of Space Vector Modulation (SVM). In the optimal pattern, the switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying its commutation strategy. In addition, the optimal pattern enables M2PC to produce sinusoidal source current, sinusoidal output current and maintain all desirable characteristics of MPC. 10:35AM Improved Steady State Behavior of Finite Control Set Model Predictive Control applied to a Flying Capacitor Converter [#227]
Finite Control Set Model Predictive Control (FCS-MPC) allows to deal with non- linearities of the system and obtain a fast dynamic response. Therefore FCS- MPC is a good alternative to govern complex power converters or when fast transient operation is required. The main drawback of FCS-MPC is the performance obtained during the steady state, the main reason resides in the poor temporal resolution of FCS-MPC and the mismatch of the model parameters. This paper presents a new way to implement FCS-MPC to correct the mismatch in the model parameters and achieve a better performance in steady state. This is achieved through the incorporation of the past error in the action of the control, adding an additional term in the cost function with a variable weighting factor. Reluctance Machines Tuesday, September 20, 8:30AM-11:00AM, Room: 102B, Chair: Akira Chiba, Yun Wei Li 8:30AM A new application and experimental validation of moulding technology for Ferrite Magnet Assisted Synchronous Reluctance Machine [#872] Qian Wu, Kaiyuan Lu, Keld Folsach Rasmussen and Peter Omand Rasmussen, Aalborg University, Denmark; Grundfos A/S, Denmark This paper introduces a new application of moulding technology to the installation of ferrite magnet material into the rotor flux barriers of Ferrite Magnet Assisted Synchronous Reluctance Machine (FASynRM). The feasibility of this application with respect to manufacturing process and motor performance has been demonstrated. In comparison to the conventional ferrite magnet installation approach, moulding technology has obvious advantages of improved mechanical strength of the multi-flux-barrier rotor structure, simplified installation process, reduced processing cost and in the same time, allowing a high degree of flexibility in the rotor flux barrier shape design. A prototype is manufactured using the moulding technology, and the attractive features are verified by detailed experimental results.
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