Power Losses In Inverter Research Articles

Deep reinforcement learning assisted co-optimization of Volt-VAR grid service in distribution networks

With the increasing penetration of distributed energy resources in distribution networks, Volt-VAR control and optimization (VVC/VVO) have become very important to ensure an acceptable quality of service to all customers. System operators can rely on slow-responding utility devices, including capacitor banks and on-load tap changing transformers, along with fast-responding battery and photovoltaic (PV) inverters for the VVC/VVO implementation. Because of variations in response time of these two classes of devices, and different control actions (discrete versus continuous), coordinated and optimal scheduling and operation have become of utmost importance. This paper develops a look-ahead deep reinforcement learning (DRL)-based multi-objective VVO technique to improve the voltage profile of active distribution networks, decrease network and inverter power loss, and save the operational cost of the grid. It proposes a deep deterministic policy gradient (DDPG)-based approach to schedule the optimal reactive and/or active power set-points of fast-responding inverters, and a deep Q-network (DQN)-based DRL agent to schedule the discrete decisions variables of slow-responding assets. The reactive power output of PV and battery smart inverters are scheduled at 30-minute intervals and the capacitors’ commitment status is scheduled with several hour intervals. The proposed framework is validated on the modified IEEE 34-bus and 123-bus test cases with embedded PV and PV-plus-storage. To validate the efficacy of the proposed VVO, it is compared with several scenarios, including the base case without VVO, localized droop control of DERs, DDPG-only, and twin delayed DDPG (TD3) agent-based DRL techniques. The results justify the superior performance of the proposed method to improve the voltage profile, reduce network power loss, and minimize the look-ahead grid operational cost while minimizing the undesirable power losses in inverters as a result of power factor adjustments.

Development and Performance Evaluation of Integrated Hybrid Power Module for Three-Phase Servo Motor Applications.

This study aims to develop a 30 kHz/12 kW silicon carbide (SiC)/Si integrated hybrid power module (iHPM) for variable frequency drive applications, particularly industrial servo motor control, and, additionally, to theoretically and experimentally assess its dynamic characteristics and efficiency during operation. This iHPM integrates a brake circuit, a three-phase Si rectifier, and a three-phase SiC inverter within a single package to achieve a minimal current path. A space-vector pulse width modulation (SVPWM) scheme is used to control the inverter power switches. In order to reduce parasitic inductance and power loss, an inductance cancellation design is implemented in the Si rectifier and SiC inverter. The switching transients and their parasitic effects during a three-phase operation are assessed through an electromagnetic-circuit co-simulation model, by which the power loss and efficiency of the iHPM are estimated. The modeled parasitic inductance of the inverter is validated through inductance measurement, and the effectiveness of the simulated results in terms of switching transients and efficiency is verified using the experimental results of the double pulse test and open-loop inverter operation, respectively. In addition, the power loss and efficiency of the SiC MOSFET inverter are experimentally compared against those of a commercial Si IGBT inverter.

Testing of Variable-Speed Scroll Compressors and their inverters for the evaluation of compact energy consumption models

Prediction models for energy consumption in heat pumps are critical for design, selection, control and fault detection. However, nowadays, the methodology for characterizing variable-speed compressors has not been standardized, and typically the pair compressor-inverter is studied as a whole. In this study, disaggregated energy consumption results of compressor and inverter are provided by using a double-wattmeter scheme. These results are used to compare the performance of existing models and to establish guidelines to define testsmatrixes as compact as possible to characterize this type of compressors. The widely used 20-coefficient correlation can overfit the compressor behaviour when fitted with an small dataset, introducing significant deviations when extrapolating. Optimal Design methodologies to create rating test matrixes gave excellent results compared with classical clustering techniques. Regarding inverter results, a compact empirical model was proposed to model inverter power losses depending on total consumption and compressor speed. The proposed model used only five fitting coefficients, and most predictions are inside a 5% error band for all tested inverters. Finally, the tested compressors and inverters suffered a significant efficiency loss at very low speeds, which could make cycling more profitable under certain circumstances.

Clamping Modulation Technique for Balancing Power Losses of Dual Inverter With Isolated DC Bus

This paper proposes a clamping modulation technique to reduce and balance power losses in a dual inverter with an isolated DC bus. To drive an open-end winding permanent magnet synchronous motor (OEW-PMSM), dual inverter consisting of six legs has twelve switching actions, twice as many as a two-level voltage source inverter (VSI) per switching period. However, many switching actions cause power losses in switching devices, reducing the efficiency of the system. In this paper, a four-leg clamping modulation technique is presented to reduce the switching actions by analyzing the relationship between two reference voltage vectors of primary and secondary inverters on a space vector plane. To clamp four of the six legs overall, the switching states are determined by combining active and zero vectors during the switching period. The selected vector combinations differ according to 18 sectors divided by the magnitude and angle of the reference voltage vector. The zero vectors required for 18 sectors are then distributed to balance the power losses in upper and lower switching devices of each leg. This technique is implemented with carrier-based pulse width modulation (PWM) by calculating each three-phase reference voltage from two reference voltage vectors composed of the vector combinations. Balancing of the power loss between the upper and lower switching devices is achieved by adding offset voltages corresponding to the zero vector of each sector. The validity of the proposed technique is verified experimentally.

Integral backstepping-ILC controller for suppressing circulating currents in parallel-connected photovoltaic inverters

In big solar plants where the use of a single inverter is neither economically or technically feasible, parallel linked photovoltaic inverters are necessary. For parallel-connected operation, the most significant issue is that even a slight variation in the output voltages of particular inverters results flow of circulating currents. A high level of circulation current causes inverter power losses to increase, which lowers the system's overall performance by decreasing its efficiency. In this paper, a novel simple and effective controller for parallel-connected inverters is proposed to ovoid the circulating currents among the inverters. Convergence efficiency and low computational cost of the suggested controller based on integral backstepping method are the primary motivations of this work. The simulation and experimental findings show that the suggested control system achieves the required power quality and reduces circulation current under various loading situations.

유효 무효전력 분리 제어기반의 DPWM을 이용한 플라잉 커패시터 듀얼 인버터 전력 손실 저감 방법

Output voltages of dual inverter are generated by the output voltage difference between the primary inverter and the secondary inverter in a dual-inverter. Thus, the dual-inverter has an advantage that produces the higher output voltages than the single inverter. However, the loss of dual-inverter increases because its topology consists of 12 switching devices. Besides, the flying capacitor dual-inverter requires not only a control for motor but also a control that balances the voltage of flying capacitor in secondary inverter. In this paper, a DPWM method for reducing the power loss in both inverters is proposed under the separation control which outputs the active power in the primary inverter and the reactive power in the secondary inverter. In the proposed DPWM method, the primary inverter with an unity PF minimizes the power loss and the secondary inverter with a zero PF also minimizes the power loss considering the magnitude and phase of a current. An effectiveness of the proposed method is verified with simulations and experiments.

Analysis of power losses in multilevel pulse-width modulation inverters

The paper describes the types of multilevel pulse-width modulation, as well as methods for obtaining control signals for the inverter power switches for each of the types. The dependence of the harmonic composition of the output voltage of the inverter on the number of levels and the switching frequency of the keys of each level is analyzed. By modeling, the dependences of the transistor junction temperature on the number of voltage levels, switching frequency and load power are determined. The power switching system of an inverter with phase-shifted pulse-width modulation in high-frequency mode is analyzed, the dependence of switching losses on inductance is investigated. The ways of solving or improving the control systems of the conductivity losses of the converter flowing through the primary winding of a high-frequency transformer during the free-running period are formulated. The importance of this direction for the technological development of the economy, where efficiency improvements can lower individual utility bills, create jobs, and help stabilize electricity prices and volatility is shown. The most important stage of inverter design is called structural synthesis stage – the choice of topology and modulation algorithm that will ensure the greatest efficiency of the device. In addition, since the efficiency and reliability of inverters depend on the efficiency and reliability of secondary electricity consumers, the task of optimizing inverter circuits is a cornerstone for the effective development of technology and economy. The maximum dynamic power loss at a PWM frequency of 1 kHz reaches only 80 watts compared to the static power loss value of 800 watts

An Optimization Method of a Digital Active Gate Driver Under Continuous Switching Operation Being Capable of Suppressing Surge Voltage and Power Loss in PWM Inverters

This paper proposes a new optimization method and its platform for automatically adjusting the control parameters of a digital active gate driver using a PWM inverter. The proposed optimization method applies the searching parameters for only any duration in an ac current cycle and fixed parameters for the other duration. This enables us to find the optimal operating points of power devices so as to reduce the surge voltage and switching loss with the consideration of their dependency on the load current. Additionally, the proposed optimization method also can find the operating points while the inverter performs a continuous switching operation. For this reason, the proposed optimization method can be applied to a continuous running test of PWM inverters, for example, in a manufacturing process. The validity of the proposed method and platform was evaluated by using a 10-kW three-phase PWM inverter with digital gate drives. The experimental results confirmed that the proposed optimization method makes it possible to find the optimal operating points for reducing the surge voltage and/or the power loss.

Electrothermal-Control Co-Design of an All Silicon Carbide 2×250 kW Dual Inverter for Heavy-Duty Traction Applications

This article presents the design and demonstration of an all silicon carbide (SiC) 2×250 kW dual inverter for heavy-duty traction applications. Through the use of a formal electrothermal-control co-design approach, the maximum power density of the proposed inverter system is 60 kW/L, which is accomplished by. More specifically, to analyze the thermal performance of the inverter, a lumped thermal model is developed based on the characteristics of the power modules and the cold plate. To analyze the complicated interaction between the power losses and module junction temperatures, a closed-loop iterative estimation scheme is proposed to estimate the inverter power loss and module junction temperature. Based on the proposed thermal model and estimation scheme, a detailed optimization procedure on the selection of switching frequency and dc-link capacitor is presented to maximize power density. Furthermore, design optimization of the busbar was conducted to minimize the stray inductance, thus reducing the voltage overshoot during switching transients. Comprehensive experimental studies were performed on a physical converter prototype built based on the optimization results, which validate both the effectiveness of the presented design approach.

Моделирование потерь мощности в преобразователе частоты

Моделирование потерь мощности в преобразователе частоты

Method for estimation of power losses and thermal distribution in power converters

The power loss estimation is a crucial step for power electronics design, especially for high-power-density systems. Many mathematical approaches are known for power loss estimation, but the system design time can be lowered significantly if a simulation approach is used. This paper discusses the MATLAB-based simulation method for estimating power losses in the three-phase VSI. This simulation is using a real characteristic of the used IGBT transistors for power loss estimation. Next, the model uses the simulated power losses and calculates temperatures at different points in the simulated model. For the visualization, Fusion360 was used to simulate the thermal spreading at the heatsink. Finally, the inverter power losses are measured at the different loads to confirm the accuracy of the model. The temperature of the heatsink is measured with a thermal imaging camera and surface mounted probes.

Implementation of an FPGA-Based Current Control and SVPWM ASIC with Asymmetric Five-Segment Switching Scheme for AC Motor Drives

This paper presents the design and implementation of an application-specific integrated circuit (ASIC) for a discrete-time current control and space-vector pulse-width modulation (SVPWM) with asymmetric five-segment switching scheme for AC motor drives. As compared to a conventional three-phase symmetric seven-segment switching SVPWM scheme, the proposed method involves five-segment two-phase switching in each switching period, so the inverter switching times and power loss can be reduced by 33%. In addition, the produced PWM signal is asymmetric with respect to the center-symmetric triangular carrier wave, and the voltage command signal from the discrete-time current control output can be given in each half period of the PWM switching time interval, hence increasing the system bandwidth and allowing the motor drive system with better dynamic response. For the verification of the proposed SVPWM modulation scheme, the current control function in the stationary reference frame is also included in the design of the ASIC. The design is firstly verified by using PSIM simulation tool. Then, a DE0-nano field programmable gate array (FPGA) control board is employed to drive a 300W permanent-magnet synchronous motor (PMSM) for the experimental verification of the ASIC.

A Modular Multilevel Converter with an Advanced PWM Control Technique for Grid-Tied Photovoltaic System

Due to global warming and shortage of fossil fuels, the grid-connected solar photovoltaic (PV) system has gained significant popularity all over the world. The modular multilevel cascaded (MMC) inverter is the natural choice for step-up transformer and line filter less direct medium voltage grid integration of solar PV systems. However, power quality and loss are the important issues while connecting the PV system to the medium voltage grid through MMC inverter. Modulation technique is the key to maintain output power quality, e.g., total harmonic distortion (THD) and to ensure low switching and conduction losses. In this paper, an advanced modulation technique named “triangle saturated common mode pulse width modulation (TSCMPWM)” control is proposed for a 3-phase 5-level MMC inverter-based grid-tied PV system. Compared to traditional modulation techniques, the proposed TSCMPWM control offers the lowest voltage THD as well as lower inverter power losses. Performance of the proposed modulation technique is evaluated in MATLAB/Simulink environment and tested with a reduced scale prototype test platform. Both simulation and experimental results show the effectiveness of the proposed modulation technique.

The Loss Analysis and Efficiency Optimization of Power Inverter Based on SiC mosfets Under the High-Switching Frequency

Due to its low loss and high switching frequency, the silicon carbide metal oxide field effect transistors (SiC mosfet s) are more suitable as switching devices in power inverter for electric vehicles. However, the power losses of power inverter would be dramatically increased with the rise of switching frequency, which would result in the limitation of using the high switching frequency performance of SiC mosfet . In view of this case, this article would systematically analyze the power losses distribution of power inverter and further optimize its efficiency under the high switching frequency. It is demonstrated that the power losses of power inverter are linearly increased with the rise of switching frequency, which is mainly caused by the switching losses of mosfet chips increment. Based on this situation, an adaptive discontinuous pulsewidth modulation (ADPWM) is proposed to optimize the power inverter efficiency under the high switching frequency, which can effectively reduce the total power losses of power inverter and improve its efficiency compared with that of the conventional PWM strategies. Finally, the power losses and efficiency of power inverter with the proposed ADPWM strategy is verified by the experimental results.

Energy reduction by power loss minimisation through wheel torque allocation in electric vehicles: a simulation-based approach

ABSTRACT As vehicles become increasingly electrified, electrical machines for propulsion can be divided into many sources making the vehicle highly over-actuated. For over-actuated vehicles, the allocation of a propulsive force is an underdetermined process with respect to both the number of wheels and electrical machines. Hence, the allocation can be made to favour particular attributes such as energy consumption. In this study, a vehicle equipped with four identical electric motors with a fixed transmission ratio connected through a half-shaft and a coupling to one wheel respectively is driven a 2-h-long city cycle in the vicinity of Göteborg. Two different control allocation methods are presented to distribute torque momentaneously based on driver request while minimising power losses in electric motor and inverter as well as tyres. One method is a quadratic programming optimisation and the other is an offline exhaustive search method resulting in a look-up table based on requested torque and actual speed. The two methods are compared to other torque distribution strategies based on fixed distribution ratio and equal tyre-to-road friction utilisation. It was found that using the developed optimisation algorithms, a reduction of up to 3.9 in energy consumption can be obtained.

Optimal design of a single-phase APF based on PQ theory

The instantaneous active and reactive power (PQ) theory is one of the most widely used control theory for shunt active power filter (SAPF), which can be implemented in single-phase and three-phase systems. However, the SAPF with PQ theory still had ability to improve to become more efficient. This paper presents the optimal design of a single-phase SAPF in terms of reducing the current harmonic distortion and power loss in voltage source inverter (VSI) controlled with the semiconductor switching devices IGBT, MOSFET and Hybrid (combination of IGBT and MOSFET). In order to reduce the switching frequency and power loss of VSI, instead of using single-band hysteresis current controller (HCC), double-band HCC (DHCC) and triple-band HCC (THCC) is used in the SAPF. The designed SAPF is tested with different non-linear loads to verify the results by using MATLAB Simulink.

The Study of Comparative Characterization between SiC MOSFET and Si- IGBT for Power Module and Three-Phase SPWM Inverter

This paper focuses on how to define and integrate the system level and power module level with optimal conditions in SiC and Si-IGBT. To investigate the above situation, we compare the performance of SiC and Si-IGBT in power module and system level at different ambient temperatures. At the same maximum junction temperature 150°C and ambient temperature at 25°C and 80°C, it found that SiC type electrical resistance, maximum endurable current, and voltage could be better than the IGBT type power module above 20%. On the other hand, the simulation of three-phase inverter at different switching frequency such as 10kHz, 15kHz, 20kHz, 30kHz and it had been observed that the power loss of SiC inverter are 78% less for 10kHz switching frequency; 82% less for switching frequency at 15kHz; 85% less for 20kHz of switching frequency; 89% less for switching frequency at 30kHz in the Si-IGBT three-phase SPWM inverter at ambient temperature 80°C.

Measuring the power conversion losses in voltage source inverters

The power losses in a voltage source inverter (VSI) are the sum of the additional constant power losses of the local power supply, the inverter circuits as well as the main power conversion losses. Power conversion losses consist of the power losses on switches (e.g. static power losses on the resistances of the switches in the “on state” and the dynamic switching power losses), the power losses on the serial resistances of the filter inductor winding together with the resistances of all of the serial inverter connections and the power losses of the filter coil, which are dependent on the material of the filter coil core. All of these power conversion losses can be presented as losses on the one equivalent serial resistance that is connected serially with the filter coil. This nonlinear (depending on the load and the switching frequency) serial equivalent resistance Rse can be calculated from the parameters of the maximum point of the measured magnitude Bode plot of the control transfer function of the inverter. The paper presents the concept of measuring the Bode plots of the control transfer function in order to get the serial equivalent resistance and to calculate the power conversion losses of an experimental model and discusses the accuracy of the results.

A Framework for Optimum Determination of LCL-Filter Parameters for N-Level Voltage Source Inverters Using Heuristic Approach

The use of voltage source multilevel inverters (VS-MLIs) has grown enormously over the last decade, and it is expected that these inverters will be deployed in future power grids (smart grids), especially for medium voltage–high power applications. This paper investigates the application of passive power filters (PPFs) for harmonic mitigation at the output of VS-MLIs for more efficient grid integration of renewable energy sources. It proposes a generic model, using a heuristic approach, for the optimum design of an LCL power filter at the output of VS-MLIs. The proposed model transforms the LCL filter design problem into an optimization problem and applies a genetic algorithm (GA) to solve it. The objective function to be optimized is a multi-objective function based on inverters’ total harmonic distortion and energy losses. The optimization problem is subject to applied design constraints. As a main optimization objective, a precise evaluation methodology for the inverter power losses is presented, which was built according to a practical switching device datasheet. The method is applicable to any VS-MLI topology and any number of levels (N). As a case study, the proposed design optimization approach was implemented to optimally design the LCL filter at the output of a grid connected 11 KV, 5 MVA 7-level cascaded H-bridge multilevel invert (CHB-MLI). The IGBT module Device IGBT of type FZ400R65KE3 by Infineon was used for simulation. MATLAB-SIMULINK is used for the modelling and simulation. We found that the proposed design approach is more generic, efficient, and simple to apply than conventional design approaches which requires more system detail, relies more on the designer’s experience, and normally does not results in optimum design. The proposed approach is generic and can be applied for different VS-MLIs topologies and for any number of levels (N).

The Implementation of Effective Modulation Schemes to Improve the Power and Harmonic Losses in Grid-Tied Solar NPC Inverter

The growing energy demand, rising fossil fuel prices, and exceeding greenhouse gas emissions require large-scale integration of clean and renewable energy resources. Solar Photovoltaic (PV) system is the potential prospective energy resource to overcome the challenges of conventional grid. Effective power conversion topologies are the prominent need of the PV system to optimize the power and harmonic contents. Three level neutral point clamped (NPC) inverter comparatively produces less harmonics and increases the power delivery compared to the conventional and two-level inverters. Therefore, this research presents the deployment of three level NPC inverter to optimize the switching and power losses in grid connected 250 kW solar PV array. Moreover, power generation, current and voltage characteristics, and fast Fourier transform analysis is performed in MATLAB / Simulink directory with the help of Simpowersystem and Simelectronics toolboxes. To optimize the switching and power losses, sinusoidal PWM and space vector PWM are used to control the duty cycle of IGBT power switches in the proposed NPC inverter. The grid side 3 phase AC output voltage of the proposed inverter is connected to 15 kV grid with the help of 3 phase step up transformer. For 3 phase grid-tied system, the performance evaluation section of the proposed research shows the effectiveness of space vector PWM over sinusoidal PWM.