Showing papers presented at "International Power Electronics and Motion Control Conference in 2009"

Model predictive control -- a simple and powerful method to control power converters

Abstract: This paper presents a detailed description of Finite Control Set Model Predictive Control (FCS-MPC) applied to power converters. Several key aspects related to this methodology are in depth presented and compared with traditional power converter control techniques, such as linear controllers with PWM based modulation methods. The basic concepts, operating principles, control diagrams and results are used to provide a comparison between the different control strategies. The analysis is performed on a traditional three-phase voltage source inverter, used as simple and comprehensive reference frame. However, additional topologies and power systems are addressed to highlight differences, potentialities and challenges of FCS-MPC. Among the conclusions are the feasibility and great potential of FCSMPC due to today's signal processing capability, specially for power systems with a reduced number of switching states and more complex operating principles, such as matrix converters. In addition, the possibility to address different or additional control objectives easily in a single cost function, enables a simple, flexible and improved performance controller for power conversion systems.

Exploring the pareto front of multi-objective single-phase PFC rectifier design optimization - 99.2% efficiency vs. 7kW/din 3 power density

Abstract: Up to now, in the development of power electronics systems, the reduction of the initial costs or the increase of the power density have been of primary concern. However, with increasing energy costs also the power conversion efficiency is gaining higher and higher importance. Accordingly, while maintaining high power density, an efficiency as high as possible must be obtained. In this paper the maximum attainable efficiency and the dependency of the efficiency limit on technological parameters is determined for single-phase PFC boost rectifiers. In a first step basic PFC boost rectifier topologies are briefly compared with regard to high efficiency and a dual-boost PFC rectifier with integral common-mode filtering is selected as basis for the investigations. Next, simple approximations of the technological limits of the system performance are calculated in the efficiencypower density plane. With this, the Feasible Performance Space and the reduction in power density which has to be accepted for increasing the efficiency are clarified, and the trade-off limit curve (Pareto Front) of a multi-objective, i.e. efficiency and power density design optimization is determined. Furthermore, a comprehensive numerical efficiency optimization is carried out which identifies an efficiency limit of 99.2% for a 3.2kW system. The theoretical considerations are verified by experimental results from a laboratory prototype of the ultra-high efficiency system achieving 99.1% efficiency at a power density of 1.1kW/din3, as well as those firom an ultra-compact dual-boost PFC rectifier (95.8%, 5.5kW/dn3) and a very low switching freluency (3kHz) conventional PFC boost rectifier (96.7%, 2kW/din3). Finally, the sensitivity of the efficiency optimum with regard to various technological parameters is analyzed and an outlook on the further course of the research is given.

Study on frequency-tracking wireless power transfer system by resonant coupling

Abstract: Detuning is the application barrier of resonant coupling wireless power transfer. This paper analyzes the effects about inductance variations of launch coil and receiving coil to wireless transmission efficiency from its transmission mechanism and model, and also analyzes detuning mechanism. And thus, it reveals that transmission efficiency has a great affection with inductance of launch coil changing. In order to make sure that wireless power transfer by resonant coupling operates without detuning, a new method of frequency tracking control is came up with, which is, making frequency of transmitting power source tracking with the nature frequency of launch resonant circuit automaticllly. Hence, it avoids detuning and improves transmission efficiency greatly. Finally, a prototype of 1 MHz wireless power transfer system by resonant coupling was made. Experimental results prove this method very well.

Recent developments in digital control strategies for DC/DC switching power converters

Abstract: In this paper, an overview of recent advances in digital control of low to medium power DC/DC switching converters is presented. Traditionally, such DC/DC converters have been almost exclusively controlled through analog electronics methods. However, with the steadily decreasing cost of integrated circuits, the feasibility of digitally controlled DC/DC switching converters has increased significantly. This paper outlines some of the existing design challenges related to digital control and reviews a sample of recently proposed solutions. In addition, present-day research pertaining to applications such as online efficiency optimization, controller auto-tuning and specialized non-linear control is presented. Such applications demonstrate the true advantages and potential of digital control as their complexity prevents practical implementation in the analog domain.

A novel stand-alone PV generation system based on variable step size INC MPPT and SVPWM control

Abstract: The power available at the output of photovoltaic (PV) cells keeps changing with solar irradiation and ambient temperature because PV cells exhibit a nonlinear current-voltage characteristic. So its maximum power point of photovoltaic cells varies with solar irradiation and ambient temperature. Maximum power point tracking (MPPT) techniques are used in PV systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. Compared with the conventional fixed step size the incremental conductance (INC) method, this paper proposes a variable step size INC MPPT algorithm which can effectively improve the MPPT speed and accuracy simultaneously. Inverter control is another key aspect in PV generation system. This paper proposes Space Vector Pulse Width Modulation (SVPWM) control scheme for three-phase PWM inverter is used in PV generation system. A novel stand-alone PV generation system based on a variable step size INC MPPT method and SVPWM control scheme for three-phase voltage source PWM inverter is built in Matlab/Simulink software in this paper. Results of simulation show that the novel stand-alone PV generation system can have good performance of MPPT and the high quality of output voltage.

Design and research on parameter of LCL filter in three-phase grid-connected inverter

Abstract: Since LCL filter has smaller inductance value comparing to L type filter with the same performance in harmonic suppression. it is gradually used in high-power and low-frequency current-source-controlled grid-connected converters. However design of LCL filter's parameter not only relates switch frequency ripple attenuation, but also impacts on performance of grid-connected current controller. This paper firstly introduced a harmonic model of LCL filter in grid-connected operation, then researched the variable relationship among LCL filter's parameter and resonance frequency and high-frequency ripple attenuation. Based on above analysis a reasonable design method was brought out in order to achieve optimal effect under the precondition of saving inductance magnetic core of LCL filter, at the same time guaranteeing the resonance frequency of LCL filter was not too small lest restrict current controller resign. Finally this design method was verified by the experimental results.

Comparison of Particle Swarm Optimization and Genetic Algorithm in the design of permanent magnet motors

Abstract: The complexity of the electric machine structure makes an optimal design a difficult and challenging task. Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) are two popular methods for their advantages such as gradient-free and ability to find global optima. Due to the fact that the machine design models are sometimes computationally intense, it is important for the optimization algorithms used in the design practice to have high computational efficiency. This paper uses the design of a Surface Mount Permanent Magnet (SMPM) machine with an analytical model as a benchmark and compares the performance of PSO and GA in terms of their accuracy, the robustness to population size and algorithm coefficients. The results show that PSO has advantages over GA on those aspects and is preferred over GA when time is a limiting factor. Similarities in the machine design problems make the comparison result also applicable to the design of other types of machines and with other modeling methods

Optimal operating ranges of three modulation methods in dual active bridge converters

Abstract: The dual active bridge (DAB) converter attracts more and more attentions thanks to its advantages over the other isolated dc-dc converters, such as soft-switching, immunity to parasitic inductance, less circuit components and less component stress. Rectangular (also named as phase-shifted) modulation method on DAB has been widely studied and but other two proposed modulations (trapezoidal and triangular methods) have much less applications. Due to the characteristics of the modulation principles, one of these three methods outperforms the other two in certain operating ranges from system efficiency point of view. This paper summarizes the properties of three modulation methods and optimizes the combined use of three modulations on a DAB converter (12V/360V, 1 kW and 25 kHz) in order to obtain the best system efficiencies over full converter operating range. A validated loss model is utilized as the analyzing platform, based on which the optimal operating ranges of three modulations are determined.

Decoupled power control for an inverter based low voltage microgrid in autonomous operation

Abstract: With the increasing concerns for the traditional energy shortage and environment issues, distributed generation (DG) systems based on renewable energy sources (RES) have experienced a fast development in recent years. With more DG units being integrated into the power system, a more recent concept, called microgrid, is developed by grouping a cluster of loads and parallel DG units in a local area. This paper addresses the issue of real and reactive power control for DG units in a low voltage (LV) microgrid during the autonomous islanding operation. The traditional method for power control in parallel DG systems is the frequency and voltage magnitude droop method, which is based on the assumption of a mainly inductive line impedance, and is subject to power control couplings when implemented in a LV microgrid, where the line resistance to reactance ratio (R/X) is high. It is also revealed in this paper that the traditional droop control can lead to stability concerns in a LV microgrid. To achieve accurate and decoupled real and reactive power control and at the same time, to improve the system stability, a virtual frequency-voltage frame control is proposed, where the original voltage and frequency frame is transformed to a virtual frame to realize a completely decoupled relationship between real and reactive power. Details of frame transformation control and small signal stability analysis are presented. Both simulation and experimental results are provided in this paper.

Three-phase grid-connected photovoltaic system with SVPWM current controller

Abstract: Effective control strategies for reliable photovoltaic (PV) grid-connected systems are needed to efficiently use solar energy, an abundant and clean renewable energy source. A space vector pulse width modulation (SVPWM) has been widely applied in the current control of three-phase voltage source inverters (VSIs). The control strategy combines a constant voltage tracking method for the variable photovoltaic power with SVPWM-based proptional-intergral (PI) current controller in a single stage three-phase PV grid-connected system. The controller mimics deadbeat control in the synchronous d-q reference frame, and is very simple and robust to implement. With the necessary grid voltage detection in Photovoltaic systems for protection, grid harmonics disturbance is effectively suppressed through feed-forward compensation. The simulation results show that the current controller makes the PV grid-connected VSI output current to be in phase with the grid voltage and has an excellent steady-state response as well as an extremely fast dynamic response.

A novel power management control strategy for stand-alone photovoltaic power system

Abstract: The solar photovoltaic power has received great attention and experienced impressive progress in the countries all over the world in recent years because of more and more serious energy crisis and environmental pollution. This paper proposes a novel power management control strategy for stand-alone photovoltaic power system, which consists of a solar cell array, a battery, a uni-directional DC-DC converter, and a bi-directional DC-DC converter. The solar cell array powers the steady state energy and the battery compensates the dynamic energy. The goal of the power management control strategy is to control the un-directional DC-DC converter and bi-direction DC-DC converter to operate in suitable modes according to the condition of solar cell and battery, so as to coordinate the two sources of solar cell and battery supplying power and ensure the system operates with high efficiency and behaviors with good dynamic performance. A 500W experimental prototype of stand-alone photovoltaic power system was built in the lab. Experimental results are shown to verify the effectiveness of the proposed power management strategy.

Design of Boost-Flyback Single-Stage PFC converter for LED power supply without electrolytic capacitor for energy-storage

Abstract: Light emitting diodes (LEDs) are likely to be used for general lighting applications due to their high efficiency and longer life. This paper presents the concept of applying large voltage ripple for energy storage into the Boost-Flyback Single -Stage PFC converter for the elimination of the electrical capacitor. Following proposed design procedure, the single stage PFC circuit with small energy storage capacitance can still achieve good output voltage regulation while preserving desired input power factor. The detailed theoretical analysis and design procedure of the Single-Stage PFC converter is presented. The experimental results obtained on a 60W prototype converter along with waveforms are presented.

Latest developments of high-frequency series load resonant inverter type built-in cooktops for induction heated all metallic appliances

Abstract: This paper deals with the 1st generation prototype of one-stage boost-half bridge (B-HB) series load resonant (SLR) soft-switching high-frequency (HF) inverter with a lossless snubbing capacitor for a variety of induction heating (IH) appliances. The B-HB SLR HF inverter treated here is based upon a simple dual SLR frequency selection strategy changed automatically in accordance with various metal materials of IH loads. In the first place, the triple SLR frequency (three times of switching frequency) operated B-HB inverter is demonstrated for IH of non-magnetic and low resistivity metallic pans/utensils fabricated by aluminum, copper and multi-layer of aluminum and stainless steel. In the second place, the fundamental resonant frequency (switching frequency) operated B-HB SLR HF inverter for IH is also demonstrated of magnetic and high resistivity metallic pans/utensils fabricated by iron, iron cast and stainless steel. Finally, the principle of operation control, implemental and inherent unique features of the B-HB SLR HF inverter employing automatically dual resonant frequency selection scheme for a variety of IH metallic pans/utensils is described from an experimental point of view, along with its operating performance. This 1st generation HF SLR inverter type built-in IH cooktop with two ranges/three ranges has been put into practice in home energy utilizations in all electricity residential systems.

Switching cells and their implications for power electronic circuits

Abstract: This paper will introduce two basic switching cells, P-cell and N-cell, along with their implications and applications in power electronic circuits. The concept of switching cells in power electronic circuits started in the late 1970's. The basic cells presented in this paper have one switching element (transistor) and one diode. The P-cell is the mirror circuit of the N-cell and vice-versa, and this paper suggests that (1) most power electronic circuits can be analyzed and re-constructed using these basic switching cells, (2) single, dual, and 6-pack switching modules should be configured and laid-out according to the basic switching cells and not necessarily the conventional way used by industry, and (3) many benefits such as minimal parasitic inductance and dead-time elimination or minimization may come about. The present paper will describe the construction and operation of these basic switching cells, and it will also show a sequential method to reconstruct several classical dc-dc converters, a voltage source inverter (VSI), and a current source inverter (CSI) using these basic switching cells. In addition, the use of basic switching cells introduces some new topologies of dc-dc converters that originate from the buck, boost, and Cuk converter for negative input voltages. This paper will also illustrate the experimental results of the new and existing topologies constructed from basic switching cells.

A novel control strategy of wind turbine MPPT implementation for direct-drive PMSG wind generation imitation platform

Abstract: The direct-drive Permanent Magnet Synchronous Generator (PMSG) wind power imitation platform is an essential requirement for its research, development and product test. It's more efficient and flexible to demonstrate control strategies including the wind turbine's Maximum Power Point Tracking (MPPT). Conventionally, many control strategies of the motor's speed or torque are used to implement the turbine MPPT imitation, which, however, much depend on the motor parameters and are only for the Double Feed Induction Generator (DFIG) system, but rarely for direct-drive PMSG one. Thus, a novel control strategy for the wind turbine MPPT implementation is proposed, which provides a direct power control method of DC motor together with decoupled vector control of PMSG without the speed sensor. Using this control strategy, the system less depends on either parameters of the DC motor or the PMSG, and has excellent dynamic performance and high steady-state precision. The analysis, simulation and experimental results have verified its feasibility and validity.

Speed control of a permanent magnet synchronous motor using predictive current control

Abstract: This paper presents the use of a predictive technique to control the currents in a PMSM, driven by a voltage source inverter. This method allows for a high quality current control without using linear controllers and modulators, resulting in a conceptually simple solution. Simulation an experimental results confirm the good performance of the drive controlled by this method.

A novel topology for solving the partial shading problem in photovoltaic power generation system

Abstract: In centralized or string photovoltaic (PV) systems, PV modules must be connected in series in order to generate a sufficiently high voltage to avoid further amplification and to efficiently drive further converters. This always requires dozens of PV modules, however some of them maybe suffer from partial shadow caused by trees, clouds or other things. In this case, power generated from each PV module becomes unbalanced so that total output powers greatly decrease. Furthermore, hot-spot effect caused by partial shadow is likely to damage the PV cells and affect the security of PV system. In order to solve these problems, a novel topology of PV system composed of many series-connected PV modules with corresponding energy feedback circuits is proposed in this paper, a feedback circuit is independently utilized to feed the output energy of PV system to the corresponding circuit including shadowed PV module. The simulation and experimental results verify that the proposed topology can make each PV module operate on the maximum power point individually regardless of partial shadow. The energy feedback circuits do not operate without partial shadow, they have no power loss under this condition, therefore the circuit efficiency is improved.

Intelligent optimize design of LCL filter for three-phase voltage-source PWM rectifier

Abstract: Compared to traditional L filter, a LCL filter is more effective on reducing harmonic distortion at switch frequency. So it is important to choose the LCL filter parameters to achieve good filtering effect. This paper introduces some traditional design methods. Design of a LCL filter by genetic algorithm (GA) and particle swam optimization (PSO) are presented in this paper and comparison of the two intelligent optimization. Simulation result and calculate data are provided to prove that intelligent optimization are more effective and simple than traditional methods.

A new coupled inductors design in 2-phase interleaving VRM

Abstract: In order to adapt the power delivery requirements of modern microprocessors of high current, low voltage and faster transient response, interleaving VRM with coupled inductors should be used At first, this paper presents a numerical analysis of benefits of 2-phase coupled inductors and gives out the region of coupling coefficient in which the transient response speed increases meanwhile the steady-state ripple current decreases, coupled inductors should be designed in this region Secondly, this paper proposes a novel magnetic coupling structure of 2-phase coupled inductors and sets up its magnetic model to simplify the coupling structure and reduce the winding length Its validity is verified with 3D FEA simulation

The cooling technology of solar cells under concentrated system

Abstract: Temperature control is very important to keep the efficiency of solar cells, because the open-circuit voltage of the system is obviously dropped, when the temperature is raised, so as to a decline in output power of solar cells. Especially in the concentrated system, solar cells worked several times even hundreds of times in the irradiation conditions, so the temperature will significantly increased. This not only reduces the efficiency of power generation, but also impacts the life-span of the photovoltaic cells. In this paper, we analyze different ways of using system's thermal energy, and introduce the major methods and work features for concentrated solar cells cooling system, research progress about concentrated PV system in the domestic and abroad are summarized, in order to provide the foundation of improving the efficiency of the concentrated photovoltaic systems.

Digital PWM controller for high-frequency low-power DC-DC switching mode power supply

Abstract: This paper presents a fully synthesizable digital controller for high-frequency low-power DC-DC switching mode power supply (SMPS). Key module of the digital controller is a Hybrid digital pulse-width modulator (DPWM), which takes advantage of Digital Clock Manager (DCM) phase-shift characteristics available in FPGA resource and combines a counter-comparator with multi-bit Delta-Sigma (Δ-Σ) Multi-stAge-noise-SHaping (MASH) modulator. A digital controller which includes the proposed Hybrid Δ-Σ DPWM and a digital PID algorithm is experimentally verified using an FPGA on a high-frequency low-power discrete synchronous buck converter. Experimental results with constant switching frequency up to 4MHz validate the functionality of the proposed digital controller. In addition, the digital controller is implemented in a 0.35 µm standard CMOS.

Efficiency optimization of an automotive multi-phase bi-directional DC-DC converter

Abstract: The paper proposes methods to improve the efficiency of a bi-directional, multi-phase buck+boost DC-DC converter for application in Hybrid Electrical Vehicles (HEV) or Fuel Cell Vehicles (FCV) Thereto, the modulation strategy for a highly-compact, 30kW/Liter, constant-frequency soft-switching converter is optimized based on a converter loss model that includes the losses in the power semiconductors and the buck+boost inductor An algorithm for numerical calculation of the optimum switching times is given, whereas the values for the loss-optimized operation of the converter are stored in a lookup-table that is accessed by the digital controller In addition, a novel method and control concept to ensure a Zero Voltage Switching (ZVS) of all semiconductor switches by determination of a zero voltage across the MOSFET switches with analog comparators is proposed that results in the lowest inductor RMS currents for ZVS operation at the same time Furthermore, at low output power an absolute efficiency gain of over 28% is achieved by partial operation of the six interleaved converter phases A detailed description on the control concept that determines the optimum number of activated phases for the current operating point of the converter is given and verified by experimental results The measurements prove the capability to instantaneously switch the number of active phases during operation without a overshoot or drop in the converter output voltage

Power electronics interfaces for hybrid DC and AC-linked microgrids

Abstract: This paper discusses the power electronics interfaces and controls for a microgrid paradigm with both DC and AC links. The microgrid is an integrated energy delivery system that consists of interconnected distributed energy resources and controllable loads and can operate in parallel with or isolated from the main power grid. The proposed approach provides a general framework to aggregate a wide range of distributed energy resources at several levels with DC, AC and synchronous links. The collection of the aggregated units at each level represents those distributed units themselves to the upper level as a single self-controlled entity (DC or AC, generator or load). As an integrated energy system, the microgrid appears to the utility grid as indistinguishable from other currently legitimate customers. Advanced power electronics interfaces and their controls make it possible to achieve a desirable coordination among distributed resources, DC links, AC links, and the surrounding power system. In the paper, the variety of power electronics interfaces and control schemes are discussed and their performances are evaluated in a typical DC-linked microgrid and a representative AC-linked microgrid respectively.

Energy trading model for optimal microgrid scheduling based on genetic algorithm

Abstract: In this paper, a novel microgrid energy trading model (METM) is proposed to determine an optimal schedule of all available units over a planning horizon so as to meet all system, plant and unit constraints, as well as meet the load and ancillary service demands. As the optimization greatly depends on the power generation and the power output from renewable sources strongly depends on the weather, the forecast of power generation is required for METM. A neural network power forecasting is used to predict hourly power outputs. Depending on the forecast module, the METM utilizing genetic algorithm was developed to assist the microgrid scheduling which manages the micro sources and make good operation and trading decisions while meeting the constraints.

Power flow control of a distributed generation unit in micro-grid

Abstract: Distributed generation units in micro-grid can be connected to utility grid as alternative energy sources besides providing power to their local loads. The distributed generation units are interfaced with utility grid using inverter. With inverter control, both active and reactive power pumped into the utility grid from the distributed generation units can be controlled. Reactive power flow control allows the distributed generation units to be used as static var compensation units besides energy sources. This paper has presented a power flow control approach for a DG unit in micro-grid. The proposed approach achieves decoupled P and Q control under grid-connected mode, an integral approach to conduct the power flow control has been developed to control P by adjusting the power angle and control Q by adjusting the filter capacitor voltage. This paper has described control system algorithm for the proposed power controller. Simulation and experiment results have demonstrated strong P and Q regulation capability, fast enough response, and purely sinusoidal line current.

A modified MPPT method with variable perturbation step for photovoltaic system

Abstract: A novel MPPT method, which adjusts the perturbation step according to the work point of photovoltaic (PV) module, is proposed to reduce the power oscillation around MPP. There is the nonlinear relation between the output power of photovoltaic module with temperature and load. The perturbation step is constant in traditional perturbation and observation (P&O) MPPT method. There is serious power oscillation around MPP under the control of P&O method. P&O with fuzzy control, which can implement variable perturb step control, has good control effect, however this method is too complex for practical use. The relation of the perturbation step and the output power of PV module is analyzed, which shows the step around maximum power point (MPP) should become small enough to eliminate power oscillation. This paper proposes a simple variable perturbation step P&O method according to this conclusion. This method utilizes the relation of the output power and voltage of PV module as the judge of step changing. Simulation and experimental results show the proposed method has good stable and dynamic characteristics, which is applied in PV power generation system.

Analysis on output LC filters for PWM inverters

Abstract: The cutoff frequency of output LC filters of PWM inverters limits the control bandwidth of the converter system while it attenuates voltage ripples caused from the inverter switching. For a selected cutoff frequency of an output LC filter, infinite number of L-C combinations is possible. This paper analyses the characteristics of output LC filters for PWM inverters in the view of L-C combinations. Practical circuit conditions such as no-loads, full resistive-loads, and inductive-loads are considered in the analysis. This paper proposes a design criterion and a design example for the L-C filter combination considering both the control performance and the size of PWM inverters. An experimental PWM inverter system based on the proposed output LC filter design guideline is built and tested.

Primary-side sensing error analysis for flyback converters

Abstract: Primary-side sensing (PSS) technique can be used for output voltage or current regulation by employing an auxiliary winding for the sensing of the output voltage without using an additional opto-coupler for output feedback isolation. However, the sensed voltage may be corrupted by switching noises due to leakage inductance, winding resistance, uncertainty of winding parameters, and nonlinearity of the magnetic core, therefore, the sensed voltage can only achieve limited accuracy. This paper makes an error analysis of the PSS technique due to the leakage inductance and other key parameters when applying to flyback converters. Computer simulation has been carried out to verify the proposed error analysis method. The developed error analysis method can be used to improve the design of the flyback transformer and PSS algorithm for the development of more advanced digital primary-side controller in applications to flyback converters.

A novel MPPT control algorithm based on numerical calculation for PV generation systems

Abstract: In the future solar energy will be very important energy source. It is noticeable that the output characteristics of a PV array are influenced by the environment factors, and the conversion efficiency of PV arrays is very low. Therefore a Maximum Power Point Tracking (MPPT) technique is needed to draw peak power from the solar array in order to maximize the produced energy. This paper introduces a novel MPPT control algorithm for photovoltaic (PV) power generation systems. The proposed algorithm based on numerical calculation is able to perform MPPT with only one step by quadratic interpolation. And a constant voltage tracking (CVT) startup is used in the MPPT method to enhance the accuracy and the speediness. The rationality and the feasibility of the algorithm developed in this paper are verified by building simulation model using MATLAB SIMULINK tool. The results indicate that the proposed approach can effectively improve the MPPT speed and accuracy simultaneously.

Comparison of Z-source inverter and traditional two-stage boost-buck inverter in grid-tied renewable energy generation

Abstract: Z-source inverter and traditional two-stage buck-boost inverter are compared with respect to the voltage stress and maximum current stress of semiconductor devices and the inverter efficiency in grid-tied renewable energy generation application. The operation principles of the two inverters are introduced firstly, considering the two different PWM strategies used in Z-source inverter. Based on the principles, voltage stress and maximum current stress of semiconductor devices in both topologies are derived and compared. Then the efficiency of two inverters are evaluated and compared. The analysis and comparison results show that the traditional two-stage buck-boost inverter bares smaller voltage and current stress of semiconductor device and has higher efficiency than Z-source inverter under the same input and output conditions.