Power Source Side Research Articles

Control Optimization Method for Ship Direct Current Microgrid Based on Impedance Reshaping

In response to the constant power negative impedance characteristics on the load side of a ship DC microgrid, leading to voltage oscillation issues in the DC bus, this paper proposes a control optimization method based on impedance reshaping using bus voltage feedback. First, a simplified small-signal diagram of a lithium battery energy storage system converter is analyzed. Combining active damping control technology, an impedance regulator is introduced, and its parameters are optimized to effectively reduce the output impedance magnitude on the power source side. Subsequently, a ship DC microgrid simulation model is constructed using MATLAB R2022a/Simulink for validation, and comparative analysis is conducted on the anti-interference ability of the DC bus voltage before and after impedance reshaping. Finally, a model is built on a semi-physical simulation platform to experimentally verify the proposed method. The research results indicate that the proposed control optimization method can effectively increase the system’s stability margin, suppress DC bus oscillations, and enhance the anti-interference ability of the ship DC microgrid’s bus voltage when facing significant power load variations.

Voltage/Current Doubler Converter for Electric Vehicle Wireless Charging Employing Bipolar Pads

Light-duty electric vehicles (EVs) typically have a rated voltage of either 400V or 800V. Especially when considering public parking infrastructures or owners with multiple EVs, e.g., car rental companies, EV wireless chargers must efficiently deliver electric power to both battery options. For this purpose, this paper proposes an advanced and compact version of the previously defined voltage/current doubler (V/I-D) converter, here comprising two coupled series-compensated bipolar pads (BPPs). The presented system can efficiently charge EVs with both battery voltage classes at the same power level without affecting the current rating of the converter’s circuit components. The control scheme is implemented at the power source side in terms of switching frequency and input voltage, and only passive semiconductor devices are employed on board the EV. The equivalent circuit is analyzed, focusing on the BPPs’ undesired cross-coupling and its effect on the power transfer. Methods to compensate for the cross-coupling are proposed regarding the BPP design and operating strategy. At 7.2kW and aligned BPPs, the DC-to-DC efficiency of 96.34% and 96.53% have been measured at 400V and 800V, respectively. The proposed method has been experimentally validated at different misalignment profiles while considering battery voltages 300V-400V and 600V-800V, which proves that the V/I-D converter is a universal charging solution for EV batteries.

A novel solar photovoltaic powered grid interactive battery charging system for electric vehicle applications

ABSTRACT In this work, a novel Solar Photo Voltaic (SPV) powered grid interactive Electric Vehicle (EV) battery charging system has been proposed and validated. The objective of the proposed system is to provide seamless battery charging facility that includes a high capacity station battery system. The grid interactions like integration of SPV energy, station battery charging and reactive power support are included through the DC link of aShunt Active Power Filter (SAPF). The SAPF maintains unity power factor on the source side grid current. The objectives of the proposed system are ensuring the source side power factor nearly unity with minimal THD of source current, an SPV grid integration system with Maximum Power Point Tracking (MPPT), a comfortable charging point for EVs with a reliable charging station supported by a back up station battery. The novelty of the proposed work is that the common DC bus bar maintains a high DC link voltage when the utility source is available and the SAPF is active. The regulation of the DC link voltage is achieved by a PI controller tuned by the Gravitational Search Algorithm. The proposed system has been validated using simulations in the MATLAB SIMULINK environment as well using an experimental prototype. The proposed GSA controller outperforms in terms of THD (%) of source and load currents are 2.4 and 17.87, respectively.

Research on the deep peak-shaving cost allocation mechanism considering the responsibility of the load side

With the goal of carbon reduction, China has carried out a series of institutional reforms and innovations in renewable energy consumption. However, the existing allocation rules for peak-shaving costs concentrate on the power side only. In the context of high energy penetration rates, peak-shaving cost significantly increases, and the economic pressure on the power side sharply increases. As the beneficiaries of peak shaving, the load side, while enjoying clean energy, also needs to bear the responsibility of peak shaving and share part of the peak-shaving cost. In this regard, this paper proposes a peak-shaving cost allocation mechanism considering load-side participation. First, it uses the marginal contribution theory to establish the peak-shaving value evaluation model of the power and load. Then, based on the waveform similarity theory, it sets two indicators “Fluctuation Trend Similarity” and “Waveform Amplitude Difference” to evaluate each load’s renewable energy consumption responsibility. Finally, the peak-shaving cost allocation rules on the power source side and the load side are obtained. An example shows that the proposed allocation mechanism can initially realize the uniform distribution of power and load in peak-shaving cost. Furthermore, the method can promote the fairness of the peak-shaving market and guide users to reasonably participate in the peak-shaving market.

유도전동기에서 부하 변동시 역률 보상 장치 적용 여부에 따른 특성 해석

Induction motors are most widely used for driving rotating loads in the industrial applications. This induction motor may be operated at the rated output load in some cases, but it is often operated at lower load than the rated load. Induction motor has a low power factor due to its inductive load. A device such as a capacitor is used to compensate for a low power factor, but it is difficult to maintain a constant power factor in response to load fluctuations. Therefore, reactive power compensators such as Statcom are also used to keep constant the power factor that varies depending on load fluctuations.BRIn this study, when the load of the induction motor changes, the changes in active power, reactive power, and apparent power were confirmed for cases where no capacitor was installed, only capacitors installed, and only Statcom installed. In addition, based on this, the efficiency and power factor fluctuations at the power source side were also analyzed.

Optimal schedule of 100% renewable energy microgrid considering demand response of EVs

With the breakthrough of key technologies of renewable energy, microgrid is gradually developing towards 100% renewable energy. However, aiming at the characteristics of renewable energy power such as randomness and intermittency, the microgrid needs to cope with the “double” fluctuations from the power source side and the load side, which will pay more costs for absorbing renewable energy. To implement “source-grid-load-storage” integration, this research establishes a hierarchical scheduling model for microgrid, which considers the demand response (DR) characteristics of electric vehicle (EV) users and is 100% powered by renewable energy. The model includes two layers, EV layer and renewable energy microgrid (REMG) layer. The first layer is EV layer. This layer formulates an appropriate charging price according to the user’s price response characteristics, and initially regulates the fluctuation of the original load while taking into account the customer satisfaction. The second layer is REMG layer. Based on the preliminarily optimized load, this layer adjusts the renewable energy rejection, the interactive power of main grid, and the output of pumped storage and battery storage under grid connection mode and island mode. The REMG layer can reduce system operating costs, while suppressing interactive power fluctuations and increasing the utilization rate of renewable energy. Simulation shows that the proposed optimal scheduling model can achieve win-win between EV and users.

3상 PWM 컨버터의 계통 리액터 위치에 무관한 상전압 측정 PLL 제어 알고리즘

This paper presents various control methods to improve the quality of recently developed power conversion equipment. Compared to diode rectifier, voltage-source PWM converter controls input current in an actively manner and is widely used as a stable power conversion device. A control operation characteristic of a conventional PWM converter is identified. The conventional voltage sensing position to derive the control angle of the PWM converter required for system control is complexly installed in the hardware and the weight increases as the capacity increases because the system includes the L filter. In order to compensate for these drawbacks, the proposed system is configured to have the flexibility of the system by changing the voltage sensing position to the input terminal of the converter. At this time, since the existing control angle and phase voltage must be estimated, the phase voltage at the changed position was followed by the power source side using LPF and DSOGI-PLL, and this was compared and confirmed through a simulation.

Research on improvement of regulation ability of new power system in Guizhou province

Guizhou Province is an important energy base for the "west-to-east power transmission" in China. Beneficial from the strategic goal of "carbon peaking and carbon neutrality" proposed by the Chinese government, the new energy such as wind and photovoltaic power in Guizhou is stepping to an expressway gradually. The equipped capacitor of renewable generation is aim to add 23.3 GW during the period of "Fourteenth Five-Year Plan" and expand to 40.0 GW by 2025, accounting for about 36.2% of the total equipped capacity of renewable generation. For the characteristic such as intermittent, fluctuating and random, etc. of the output of new energy, the large-scale grid connection will introduce new challenges to the safe and continuous operation of power system. In order to meet the needs of multi-scenario applications such as peak regulation and frequency modulation of new power system in Guizhou Province, this paper proposed a scheme of improvement of regulation ability through researching regulation ability improving methods, such as flexible transformation of coalfired power, hydro-power expansion, pumped storage and new energy storage system (ESS) construction, etc. The results show that by 2025, in Guizhou Province, about 10% of the new ESS capacity will be installed on the power source side. Independent ESS projects will be built according to the peak shaving needs of the power system on the grid side, and several new ESS projects are advised for demonstration purposes on the load side due to it is difficult to recover the cost of ESS by relying only peak-valley price difference. This research results can work as a decision-making reference for the improvement of regulation capacity of new power system and the planning t of new energy storage in Guizhou Province.

Fault phase selection method for high voltage transmission line of high proportion renewable energy system

In the high-proportion renewable energy source grid (HP-RES grid), the nonlinear controlled characteristics of renewable energy sources, make the fault characteristics of power grid more complex, which deteriorates the performance of traditional phase selection components of high-voltage transmission lines. Based on the engineering practice of typical HP-RES grid, this paper analyzes the adaptability of traditional phase selection methods under different operation modes of the system. On this basis, a fault phase selection method adapted for high voltage transmission line of HP-RES grid is proposed. The method combines the voltage amplitude and variation comparison to identify single-phase fault and multi-phase fault based on the instantaneous value integral algorithm. The single-phase fault identification and faulty phase selection are carried out by using the proportional relationship between the intermediate value and the minimum value of the measurement phase voltage, and the multi-phase fault phase identification and faulty phase selection is carried out by using the amplitude of the measurement line voltage. Considering the large short-circuit current in large operation mode as the factor, the fault phase voltage value will be increased to a great extent in the case of fault resistance. In order to prevent the phase selection error, the single-phase fault selection is carried out by using the phase type and proportional relationship between the maximum value of phase compensation voltage variation and the minimum value of phase-phase compensation voltage variation when the above single-phase selection criterion fails. The simulation results show that the proposed fault phase selection method is not affected by the power source type, suitable for weak power source side and can correctly select faulty phase under different operation modes of HP-RES grid, which has high reliability and sensitivity.

A BL-CC Converter-Based BLDC Motor Drive for Marine Electric Vehicle Applications

This article presents a BLDC (permanent magnet brushless DC) motor drive for marine electric vehicle (MEV) application. The presented scheme uses bridgeless canonical cell (BL-CC) converter with center-tapped inductor (shown as two separate inductors for analysis purpose) for source-side power factor correction (PFC); however, the BL-CC converter requires two inductors. In the presented scheme use of one center-tapped inductor eliminates the requirement of one extra inductor. Thus, center-tapped inductor usage in BLDC motor drive results in decrement in components count. The BL-CC converter-based BLDC motor drive scheme do not require extra back-feeding diodes like other bridgeless (BL) schemes, but it uses inbuilt antiparallel diodes of insulated gate bipolar transistor (IGBT) switches for the same purpose this again leads to decrement in required component count. In this work, PFC BL-CC converter is operated in discontinuous inductor current (DIC) mode to attain better power quality. The DIC mode operation requires only one voltage sensor to sense DC-link voltage, whereas in continuous conduction mode (CCM), the sensor requirement increases to three (two voltage sensors and one current sensor). The PFC BL-CC converter also eliminates the diode bridge rectifier stage. The elimination of one extra inductor, two extra back-feeding diodes, DBR stage and also requirement of only one voltage sensor in DIC mode operation instead of three sensors for CCM implies reduction in components count which implies the reduction in cost and also the volume and weight of the BLDC motor drive. The weight reduction for marine (on-board) electric vehicle is very important as this enhances the vehicle performance. This paper also presents the detailed mathematical modeling and stability analysis of presented BL-CC converter using pole zero map and Bode plot. The BL-CC converter-based BLDC motor driving system for MEV application for DIC mode operation has been developed in the laboratory as well as on MATLAB/Simulink platform and simulated MATLAB and real-time experimental results have been presented to validate the presented BLDC motor drive under steady-state and dynamic operating conditions.

A PFC Scheme for the Inverse Watkins Johnson Converter for Polarity Reversible Buck Boost DC Output Voltage

A power factor correction (PFC) scheme for the Inverse Watkins Johnson Converter (IWJC) drawing power from a single-phase AC source, delivering polarity reversible DC voltage output is presented in this paper. The IWJC is basically a DC-to-DC converter which can deliver a boosted positive output voltage or a negative output voltage with buck or boost feature. It is suitable for driving DC loads, typically, DC motors in forward or reverse direction. Unlike the conventional four quadrant DC chopper, the IWJC can boost the input voltage and deliver a voltage higher than the source voltage with duty cycle controlled polarity reversible feature. This paper presents the methodology of including a PFC strategy for the IWJC, when fed from a single-phase AC supply. The proposed methodology has established that the AC source side power factor is unity and that the source current is maintained sinusoidal. Simulations and experimental verifications validate the proposed idea.

Effect of extended grading capacitor on the interrupting performance of multi-break circuit breaker during out-of-step faults

The extended grading capacitor (EGC) installed in parallel to multi-break circuit breaker (CB) chamber is a promising technique to suppress secondary arc. The effect of EGC on the interrupting performance of CB during is investigated in this paper. As CBs are subject to various operating burdens in practice, this paper is mainly devoted to the out-of-step fault. Considering the most severe condition, an equivalent circuit model for UHV line is established; the voltages on power source side and line side are derived based on Laplace transform and travelling wave theory, respectively; the expressions of transient recovery voltage (TRV) across CB contact are obtained, and hence the rate of rise of recovery voltage (RRRV). Since the CBs of two power source sides are often cleared asynchronous with a very small-time deviation, the characteristics of TRV waveform for them are separately computed and analysed. Furthermore, a series of sensitivity analysis have been performed. The influences of phase angle, parallel line, shunt reactor as well as reclosure on the interrupting performance are discussed. The results suggest that performance of CB during out-of-step fault is jointly determined by phase angle, parallel line, and especially the reclosure strategy. The EGC can smooth the TRV significantly especially during the first few microseconds of out-of-step fault, the breaking capability would be enhanced.

Interaction of Energy-Grid-Load Based on Demand Side Response of Full-cost Electricity Price

In the research of intelligent grids, people usually pay attention to the interaction between power source and load to absorb more new energy. In contrast, the utilization of power source and load on grid resources is less considered, and energy-grid-load is not fully explored. The profound benefits and value of the three interactions. To this end, the paper proposes the interactive mode and method of power supply, power grid, and load based on full-cost electricity price. The power source side needs to consider the impact of transmission costs when optimizing economic dispatch; the load side needs to calculate the full-cost electricity price based on the power flow tracking method, clarify the load’s use of power and grid resources, and reflect the “who benefits, who bears the cost” Principles and introduce demand-side response to reflect the meaning and value of full-cost electricity prices. The research found that the calculation example analysis based on the IEEE30-node system verifies that the method in this paper can reasonably allocate the cost of the power grid according to the user’s utilization of power grid resources, thereby improving the efficiency, fairness, orderliness and safety of power grid investment and operation.

A novel source side power quality improved soft starting of three-phase induction motor using a symmetrical angle controller through pic microcontroller

A novel source side power quality improved soft starting of three-phase induction motor using a symmetrical angle controller through pic microcontroller

Оценка влияния несимметричных режимов на показатели надежности распределительных систем

The power electric distribution systems (PEDS) possess a great dynamics of development. Thanks to this phenomenon in the power electric distribution systems (PEDS) the probability of apparatus of asymmetrical regimes increase monotonously. As a result of this reliability of the functioning of the power electric equipment installed in the electric knots changes. The asymmetrical regimes in the power electric distribution systems (PEDS) accompanied by the short circuit current are a function of a row determinate is a vague factor of probabilistic nature. Coming from it follows that the investigation of the influence of the asymmetrical regimes accompanied by the current of the short circuit on the reliability of the Power Electric Distribution Systems (PEDS) is one of the most important problems of the development the Power Electric Distribution Systems. The short circuit currents influence the structural and functional reliability of distribution networks and at the reliability of electrical equipment installation. The dynamics of changes in the levels of short circuit currents in electrical networks depends on the rate of change of the re-recovering voltage at the short circuit point on the power supply side and on the load side, as well as on the magnitude and rate of power change at the short circuit point on the power source side and on the load side.

3상 유도전동기 운전중 한상의 결상에 따른 운전 특성 해석

Induction motors are failing due to various causes. The biggest factor in electrical failure is due to overheating. Single phase loss in which one phase of the three phases is suddenly opened is included in the occurrence of a major failure in an electrical failure. The generation of a single phase loss can overheat the stator winding due to an increase in current, which can lead to burnout. It also affects torque, so it can deliver large torque ripple to the shaft. Therefore, it is very important to clarify what kind of problem exists when a single phase loss of the induction motor occurs. In order to compare the change of operation of induction motor during normal operation and single-phase loss operation, the rotational coordinate system theory was introduced. In this paper, changes in current, electric power, and torque were analyzed when single phase loss occurred due to the power source side of the induction motor being operated normally. It was found that the existence or absence of current and the pulsation of the magnetic flux at any phase specified during one-phase loss operation greatly affects the torque and affects the electric power.

A Novel Control Strategy for Shunt Active Power Filter Based on Gray Prediction and Optimal Voltage Vector

To enhance furtherly the current of compensation performance, a novel strategy of gray prediction and voltage vector controlling APF is proposed. This method produce leading current instruction based on gray predicting of nonlinear load current, moreover, this instruction implementated the optimal voltage vector controlling of double hysteresis-current control for APF. As far as voltage vector controlling is concerned, including the concept of target region, weak controlling region and strong controlling region, clearly and compactly describing voltage vector controlling basing on current error; As for gray prediction of load current and formation of APF leading current instruction, determining gray forecast parameters for APF experimental system. The contrast and analysis of simulation of pure dynamic resistance and unbalanced load show that gray forecast and voltage vector controlling can improve furtherly compensation precision and decrease THD of current in power source side, besides the advantage of maintaining conventional voltage vector controlling APF.

Investigation of undesired ripple voltage across power source side and solutions in military low-frequency immunity tests

The MIL-STD-461 CS101 test is one of the essential low-frequency conducted immunity tests for military and aerospace equipment, however it includes some challenges in application. The major challenge is the necessity for the measurement of injected CS101 ripples under the power frequency of the EUT. The measurement of CS101 ripples on the power frequency is almost impossible without taking some extra precautions. In addition to the hard necessity of measuring the CS101 ripple voltage induced across the EUT power input, the other challenge of measuring the ripple voltage that drops across the power source side under the AC power frequency of the EUT is now required by MIL-STD-461G, which aggravates the severe CS101 test conditions of AC devices. In this paper, we propose a FFT-based time domain solution and a method to instantly check the ripple voltage that drops across the power source side, in other words across the 10 μF test capacitor, during the test under the AC EUT power frequency and to verify that it is low enough and not affecting the reliability of the test. The method proposed in this paper significantly overcomes the CS101 test challenges and makes CS101 test results more accurate. In this paper, we also extensively focused on effective solutions to reduce the ripple voltage induced across the power source side along with measurement uncertainty analysis.

Speed-Sensorless DTC of a Matrix Converter Fed Induction Motor Using an Adaptive Flux Observer

ABSTRACT This paper aims at combining some of the best features of an available induction motor (IM) drive system while introducing a simplified adaptive flux estimation algorithm for sensorless operation. The use of a matrix converter (MC) is proposed to achieve improved source side power quality and input power factor correction of an IM drive. Direct torque control (DTC) of an IM is realized through appropriate switching of the MC and the control strategy is implemented with speed-sensorless operation by using a relatively simplified adaptive flux observer. DTC through speed and flux estimation is realized in the stationary reference frame. Primarily, three objectives are achieved, viz. speed regulation while directly controlling the motor torque (and flux), improved source side power quality owing to the use of MC, and substantially simplified sensorless estimation strategy. Additionally, economic benefits are also achieved owing to negligible energy storage requirements of the drive and sensorless operation.

Direct Electronic Load Control for Demand Response in a DC Microgrid Using a Virtual Internal Impedance Screening Model and PID Controller

To reduce peak loads, direct and indirect load control are common strategies used to change demand during peak hours. Voltage dependent demand response (DR) is a direct load control for changing loads in a DC mircogrid. The characteristics of electronic loads can be controlled with a switch-mode DC boost or buck converter. They have faster response to maintain stable output voltage under the fluctuating load condition and heavy load condition. Applying a fast load step to voltage regulator can maintain a well regulated voltages and load currents. The increased load resistance will cause voltage drop when load current is increased during heavy loads. Thus, their adjustable internal load impedances can change the absorbed currents by regulating the duty ratio. In this study, a screening model is employed to estimate the virtual internal impedances of power electronic loads. Then, the desired duty ratio can be determined to perform the DR program, while the boost converter acts to step-up or step-down the load voltages using the PID (proportional-integral-derivative) controller. For a DC microgrid, simulation results show the feasibility of the proposed methods: (1) exact control of load voltage at both the power source side and load sides and (2) regulation of absorbed currents to modify load voltages and reduce line voltage drops and line losses during heavy loads.