Series Inverter Research Articles

Voltage Compensation Method for Multi-feeder Distribution Networks Based on a UPQC with PV Injection

Abstract In response to the problem of prolonged low voltage at the end of distribution grids, a voltage compensation method for multi-feeder distribution networks based on a unified power quality controller (UPQC) with PV injection is proposed in this paper. In the proposed scheme, two series inverters, a single parallel rectifier and photovoltaic (PV) system are flexibly interconnected via DC bus. The voltage attenuation can be compensated by the two series inverter, and the parallel rectifier is capable of supplying energy to the DC side of the two series inverters on adjacent AC feeders. Meanwhile, active power can also be supplied by the PV panel through a DC/DC converter. The operation modes and control strategies of the proposed method are analyzed in-depth. Finally, a MATLAB/Simulink model is shown to verify the effectiveness of the method proposed in this paper.

Low-voltage Compensation of Distribution Networks Based on A Hybrid UPQC with Single and Three-phase Converters

Abstract For remote distribution networks, low voltage is prevalent, which seriously affects the normal use of electricity. Aiming at solving the voltage sag/dip problems in 10.5 kV distribution networks, a hybrid UPQC with a shunt single-phase rectifier and a series three-phase inverter is proposed in this paper. The shunt single-phase rectifier is connected to the feeder lines with the highest and lowest voltage phases to supply enough energy to the series inverter, and the three-phase inverter compensates the voltage deviation by injecting active power through a series transformer, such that the voltage sag/dip problems can be mitigated. The control strategies of the two converters are designed in detail in this paper. Compared with the traditional UPQC with two three-phase converters, the proposed method has the advantage of simpler control methods and lower cost. Finally, the proposed method is verified through MATLAB/Simulink model.

Analysis the islanding mode of combined operation of DG and UPQC in unbalanced distribution system

The proposed system consists of a series inverter, a shunt inverter, and a Distributed Generation (DG) connected in the dc link. It focuses on improving the power quality and ensuring the continuity of the electric power supply. The function of the scheme has been investigated in islanding mode which is a challenging mode of UPQC. The formulation of the proposed control scheme which is based on the instantaneous power theory is described. The proposed system can improve the power quality at the point of installation on power distribution systems or industrial power systems. Compensation of reactive power at the Point of Common Coupling (PCC) is examined. The effectiveness of the proposed scheme has been verified by simulation.

Booster Circuit for Harvesting Renewable Energy Based on Bioelectric Microbial Fuel Cells Whose Power Can Be Adjusted

Microbial fuel cells (MFCs) represent a promising technology that converts organic waste into electrical energy through bacterial activity. The process involves capturing a low voltage of approximately 0.4 V generated by the MFC using a small capacitor, which is then stored and transferred to a larger capacitor to increase the capacity. In order for this energy to be used for general AC-powered devices, an inverter is essential to convert the DC output to AC. This system, consisting of a series of capacitors and inverters, along with voltage dampers and rectifiers, forms a circuit that can potentially function as an efficient low-power generator. The effectiveness of this arrangement remains to be tested, which will determine its viability as a renewable energy storage solution.

A Decentralized Control Strategy for Series-Connected Single-Phase Two-Stage Photovoltaic Grid-Connected Inverters

Currently, most of the series inverter control methods rely on communication, which greatly reduces the reliability of the system and increases the cost. To address the above problems, this paper proposes a decentralized control strategy for series-connected single-phase two-stage grid-connected photovoltaic (PV) inverters. By improving the traditional droop control, the frequency and phase of the output voltage of each inverter unit are consistent and self-synchronized with the power grid while relying only on local independent control, and each unit realizes maximum power point tracking (MPPT). At different light intensities, each series-connected unit can quickly track the new maximum power point while still maintaining self-synchronization between the units. The system stability is analyzed via the small signal method, and sufficient conditions for system stability are obtained. Finally, the simulation results verify the correctness and effectiveness of the proposed control strategy.

On load voltage regulating device of long-distance mine low-voltage power supply system based on solid-state voltage regulator

In order to solve the problem of voltage loss caused by long-distance power supply system, considering the solid state power boost (SSPB) of solid-state voltage regulator, this paper proposes an on load voltage regulating device for long-distance mine low-voltage power supply system based on solid-state voltage regulator, which aims to solve the problem of voltage loss and fluctuation caused by line voltage drop and coal mining equipment startup and shutdown. Firstly, the terminal voltage of the line is deduced through the mathematical model of the motor under different working conditions, and a terminal voltage prediction algorithm is proposed, which calculates the terminal voltage state according to the electrical parameters at the head side of the substation; Then, an on load voltage regulation technology based on solid-state voltage regulator is designed and implemented, which compensates by controlling the output voltage of the inverter in series into the first end of the line. When the motor is in rated operation and start-up and stop stages, the motor voltage operates within a reasonable range; Finally, the simulation model of on load voltage regulation technology is built by using MATLAB/SIMULINK software, and the feasibility of this technology is verified by different experimental settings.

A dynamically reconfigurable entropy source circuit for high-throughput true random number generator

—True random number generator is an important hardware security primitive. Entropy source is the key to the design of a high-throughput true random number generator. To improve the throughput of a true random number generator while maintaining low hardware overhead, a novel entropy source circuit using ring oscillator with dynamically reconfigurable delay chain is proposed in this paper. The proposed entropy source exploits both signal jitter and circuit metastability. It consists of a seventh-order cycle shift register, seven 2-1MUXs and a core loop delay chain that is composed of inverters in series. Under the control of a high-frequency clock, the cycle shift register generates state transitions to control the output of MUXs, which in turn changes the number of inverters connected in the delay chain, switching the operation of the ring between steady and oscillating states. The outputs of five entropy sources are sampled and further XOR-ed with D flip-flops at a sampling clock of 400 MHz to obtain true random numbers. The proposed TRNG is implemented on the Xilinx Virtex-6 FPGA. The random numbers are captured in real-time using the Xilinx ChipScope and the TRNG is tested using the standard test specifications. The experimental results show that when working under a throughput of 400 Mbps, the proposed TRNG passes the NIST SP800-22 and the NIST SP800–90 B tests with a passing rate greater than 98% and a minimum entropy index per bit greater than 0.99. It also passes the relevant performance tests including autocorrelation test, restart test, deviation test, and temperature and voltage fluctuation test, and it has low hardware overhead.

Analysis and Power Quality Improvement in Hybrid Distributed Generation System with Utilization of Unified Power Quality Conditioner

This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system (DGs) that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner (UPQC). In addition to supplying active power to the utility grid, the system of hybrid wind photovoltaic functions as a UPQC, compensating reactive power and suppressing the harmonic load currents. Additionally, the load is supplied with harmonic-free, balanced and regulated output voltages. Since PVWind-UPQC is established on a dual compensation scheme, the series inverter works like a sinusoidal current source, while the parallel inverter works like a sinusoidal voltage source. Consequently, a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients. Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load, the converters should be sized cautiously. A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters. Thus, curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed. Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC. This investigation is verified by simulating and analyzing the results with Matlab/Simulink.

Periodic multivariate formal power series

A system of multivariate formal power series φ with a homogeneous decomposition φ=∑k=0∞φk is invertible under composition if φ0=0 and det(φ1)≠0. All invertible series over a field K form a formal transformation group G∞(n,K). We prove that every periodic series φ∈G∞(n,K) with φ1 diagonalizable is conjugate to φ1. This classifies all periodic series in G∞(n,C). A constraint for a periodic series is obtained when its first term is a multiple of identity.

Design of ring oscillator with temperature compensation effect

In this article, a ring oscillator with Temperature Compensation Effect is proposed in 0.18 μm CMOS. The ring oscillator is composed of 31 stages of inverters in series. The change in ambient temperature will cause the oscillator frequency to deviate. Therefore, this research uses a voltage circuit with a positive temperature coefficient as the power supply for the oscillator circuit, so that the ring oscillator can output stable oscillation center frequency regardless of ambient temperature. The ring oscillator has been verified by simulation and experimental testing. The ambient temperature is within the range of −40°C to 80°C. The output frequency of the ring oscillator is stable at 33 kHz ± 0.50 kHz. The frequency error is within 1.6%. Temperature stability was 120 ppm/°C. At 1 MHz off the carrier, the phase noise is as low as −151.2 dBc/Hz and the total power dissipation is 210 μW. Compared with the previous scheme, the chip area and power consumption are lower. This circuit module can provide a clock signal for the timer when the UWB chip sleeps.

Solar Interfaced Series Inverter With Provision of Common DC Bus Grounding

In this work, a new series solar inverter configuration is proposed to share the power in terms of voltage, unlike parallel inverter configurations. In a single-stage parallel inverter, elevated dc potential and circulating current due to common mode voltage (CMV) would degrade the solar inverter’s life. The proposed topology eases the stress on the dc bus and protects the solar inverter from the issues associated with elevated dc potential (potential induced degradation effect, switch operating voltage stress, etc.). The inherent boosting capability of the proposed series inverter with two modular inverters is demonstrated through two switching algorithms. In the first switching algorithm, the switching combinations are devised to yield the maximum voltage across the load. The second switching algorithm demonstrates the method of eliminating CMV by choosing the appropriate switching combination of two inverters. The eliminated instantaneous CMV would give the provision of operating proposed topology with common dc bus along with the flexibility of dc bus grounding. For the proposed configuration with devised switching techniques, the closed-loop controller is designed by computing the plant’s equivalent characteristic impedance using a state-space model. The effectiveness of the proposed configuration, along with the closed-loop control, is validated through hardware.

Impact of Improved Unified Power Quality Conditioner Allocation in Radial Distribution Network

This paper presents the investigative study on the Unified Power Quality Conditioner (UPQC) impact on Radial Distribution System (RDS). The architecture of Power Angle Controlled UPQC named Improved Unified Power Quality Conditioner (I-UPQC) was implemented in RDS. The problem of power loss, under-voltage, and reactive power burden on shunt inverters are the significant issues addressed in this study. The allocation of I-UPQC by placing it at each bus of the RDS one node at each iteration, excluding the swing bus, is studied by considering its impact on each bus of the radial network. The Power Loss Index (PLI) and Degree of Under Voltage Mitigation Node (DUVMN) values of all the buses are calculated analytically using distribution framework expressions of I-UPQC. Hence, the bus having the highest PLI value, and the minimum permissible node voltage is the most favourable. The determination of the candidate bus for I-UPQC was achieved by the load flow algorithm. The results obtained in this study on IEEE 33 and 69 bus system shows 3.9% and 4.2% power loss reduction respectively for both networks. Also, the minimum bus voltage was improved to 0.954 p.u. and 0.955 p.u. in each case for both networks, after the allocation of I-UPQC in RDS, compared to the base case. Consequently, the VA burden on shunt inverter was reduced by reactive power compensation of the series inverter. The results and simulation obtained in MATLAB / SIMULINK environment and discussion to support the concept developed are also presented. The results from the study confirmed that the concept of I-UPQC placement impacted the operation of RDS compared to the other connected UPQC model.

Seamless Switching Technology of UPQC Based on Improved Power Angle Control

This paper presents a novel seamless switching technology between different operating conditions of the Unified Power Quality Conditioner (UPQC) with the energy storage system. Frequent start and stop of the series inverter will cause shock and loss under the conventional control method. Moreover, it is a key issue to achieve seamless switching when the UPQC operating condition changes. This paper proposes an improved power angle control (PAC) method to solve these problems. An agile power angle is calculated by this method under stable operating conditions. This feature enables the series inverter to share the load reactive power with the shunt inverter. On the other hand, both the series and shunt inverters are in an easy-to-switch operating state which can help achieve better seamless switching between different operating conditions. Simulation results show the shunt inverter capacity can be reduced up to 47% due to the reactive power sharing by both the inverters which means the reactive power burden of the shunt inverter is great lightened. It is also found that the switching time is about 300μs faster and the maximum voltage fluctuation amplitude is about 90V smaller under improved PAC than the conventional control method.

Effect of unified power flow controller installation in dual feed induction generator (DFIG) wind turbines

Abstract In recent years, the use of wind energy to generate electricity in the world has been accelerating and growing. Wind farms are unstable when dynamic voltage fluctuations occur, especially sudden and sudden changes in load, and show oscillating performance at their output. In this paper, the Unified Power Flow Controller (UPFC) has been simulated and studied by Matlab software to improve the dynamic stability and transient behavior of the wind power plant in the event of sudden load changes. The simulation results show that by controlling the UPFC series inverter, voltage fluctuations in the PCC bus are prevented and the UPFC parallel inverter injects power after changing the load for faster recovery and stability of the PCC bus voltage and thus the stability of the wind farm. The UPFC can control the active and reactive power at the transmission line, and in fact, controls the output of the wind turbine with the generator from both sides to the fluctuations caused by sudden load changes that play a role such as sudden disturbances and oscillating errors. Also, the presence of UPFC in the system reduces power fluctuations.

Ternary Devices Based on Partially Aligned MoS2/h‐BN/Graphene Heterostructures

AbstractThe development of multi‐valued logic devices, which involve switching between more than two states, is one of the promising approaches for overcoming the issues caused by the further scaling down of the current complementary metal‐oxide semiconductor devices. This paper presents ternary devices based on MoS2/h‐BN/graphene heterostructures, in which an active channel of MoS2 is partially aligned with a floating gate of graphene, unlike in the case of typical flash memory devices; thus, they can be regarded as a circuit consisting of a memory device and field‐effect transistor internally connected in parallel. The transfer curves of these devices exhibit two different threshold voltages (Vth) with ternary states (“0,” “1,” and “2”). Furthermore, the intermediate state can be controlled by oxygen plasma treatment, resulting in a ratio >102 for “1”/“0” states and “2”/“1” states. Thus, these devices can be used to implement a resistive‐load standard ternary inverter, whose output voltage is close to 1, 0.5, and 0 V under the supply voltage of 1 V. In addition, ternary NMIN and NMAX circuits with resistive loads are demonstrated by connecting two ternary inverters in series and parallel, respectively.

Inverator Starting Energy Saver Design For Electric Power Efficiency In Water Pumps

The use of a Water Pump at the initial start is the use of electricity with a large capacity which sometimes faces various kinds of efficiency problems. These problems include an increase in current that occurs in the channel by improving the quality of electric power, especially in the electrical system in the area of the use of the Water Pump, which is expected to be able to improve the quality of electric power. The purpose of the research was to design an inverter starting energy saver as an effort to improve power quality for electricity savings, electric power efficiency in water pumps. This improvement is also expected to be able to reduce the cost of using electricity bills, especially in the use of water pumps. To be able to carry out the improvement of the quality of the electric power, it is necessary to calculate the active power and apparent power when the water pump is used. After performing these calculations, the installation of the inverter starting circuit saver electricity will be used. By carrying out these steps by installing a series of inverters that can improve the quality of electrical power. And by using the inverter circuit starting Energy saver, it is clear that it produces an active power efficiency value of 82% of the active power before using the 272 Watt inverter circuit and active power after using the 223.9 Watt inverter circuit, and also produces an apparent power efficiency value of 83% before using the circuit. inverter 275.18 VA and apparent power after using the inverter circuit 227.94 VA

A transformerless active voltage quality regulator with the novel three‐leg circuit

AbstractVoltage sags and momentary interruptions of power are the most severe voltage disturbances. Here, a tansformerless active voltage quality regulator with the novel three‐leg circuit is proposed to mitigate long duration and deep voltage sags. The shunt rectifier and series inverter of this novel three‐leg circuit are all full‐bridge structures, so it has lower DC bus voltage and smaller filter parameters than the conventional half‐bridge topologies. The totem‐pole bridgeless boost circuit is formed among the three bridge arms and the DC bus voltage will be charged to exceed the peak value of the supply voltage. It can compensate for deep voltage sags (that may be more than 50% of the nominal voltage). Compared to the conventional transformerless series‐connected topology, the proposed topology has the merits of higher efficiency, smaller volume and lower cost. The validity and feasibility of the proposed topology are verified by theoretical analysis, simulation and experiment.

A new optimal design of ACD-based UPFC supplementary controller for interconnected power systems

This study presents a new optimal supplementary neuro-controller design for unified power flow controllers (UPFCs) using wide-area signals. The new design is oriented by the dual heuristic programming (DHP) method, which is a powerful adaptive critic procedure. The proposed controller injects additional signals to the UPFC series inverter to enhance power system stability. A model, action and critic neural networks are also designed for optimizing the neuro-controller. To have an accurate dynamic response of multi-machine power systems, the concepts of two-machine equivalent model (TMEM) and center of inertia (COI) are used to train the adaptive critic design (ACD) neural networks. The ANFIS structure is applied to the suggested DHP technique based on the selected input signals to improve the dynamic performance of the applied DHP controller. The designed optimal controller is applied on a real interconnected power system between Tehran and Khuzestan regions in Iran power grid. The proposed ANFIS-DHP controller performance is compared with various controllers, such as PI-Genetic, PI-Lyapunov and other intelligent approaches. The dynamic responses of the proposed controller are found to be the most effective in increasing system stability and damping out system inter-area oscillations.

Analyzing the Effects of Micro‐Source Disconnection on Interactive Stability of Grid and Micro‐Grid with Series Inverters

Owing to a lack of systematic mathematical models to represent the parameters related to micro‐source disconnection, the stability of interaction between a grid and a micro‐grid with series micro‐source inverters (SMSI‐MG) is difficult to analyze. In this study, the average ratio and the degree of imbalance of three‐phase micro‐source disconnection, denoted respectively by δ and ϵ, are defined, and the positive‐ and negative‐sequence impedances of the SMSI‐MG containing the two parameters are established using a combination of the harmonic linearization and the symmetrical component methods. Moreover, rules of the behavior of the SMSI‐MG after micro‐source disconnection as well as its mechanism of interaction with the grid are revealed by the impedance models. The results of analysis show that high‐frequency harmonic resonance was generated around the carrier frequency when δ ≠ 0, and both high‐ and low‐frequency harmonic resonances were generated when both δ and ϵ increased in the interactive system. Furthermore, three SMSI‐MGs containing five, 10, and 20 micro‐sources in a single phase were simulated, and the results verified the correctness, feasibility, and advantages of the simplified analysis of the impedance models. These insights can be used to apply the corresponding control strategies in a timely manner according to the given conditions of micro‐source disconnection to reduce the harmonic resonance and increase the stability of the SMSI‐MG and the grid. The results of simulations verified the effectiveness of such a control strategy. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A Shunt Capacitor Equipped with a Series Inverter for Compensating Harmonics along with Existing Equipment

A Shunt Capacitor Equipped with a Series Inverter for Compensating Harmonics along with Existing Equipment