DC Chopper Circuit Research Articles

Smart Sag Detection and Reactive Current Injection Control for a PV Microgrid under Voltage Faults

Low-power photovoltaic distributed generators are increasing rapidly in number by the grids of the modern era, but they also bring up the concern of grid stability. To maintain grid stability, it is essential for the network operators to update the grid codes at regular intervals due to the case of highly penetrated grid-connected photovoltaic systems (GCPVs). Integration of large-scale electrical grids with renewable energy sources, one being photovoltaic systems, faces the challenge of riding through low-voltage (LVRT) phases. As compared to the previous grid codes for power generation, recent advances require distributed generation resources to provide for such capabilities under grid faults. This work contributes to the ongoing investigation of this specified and destabilizing fault condition. Various simulations of a PV microgrid system are carried out with the ability to ride through low-voltage faults, with the help of a DC-chopper circuit to absorb DC-link over-voltage, and the current is also maintained within acceptable limits according to the required standards. The fundamental contribution of this research is a proposed neural network (NN) control framework. This framework effectively detects voltage sags, comprehends their characteristics, and provides support to the system by injecting reactive current in accordance with the demands imposed by designated grid codes. This NN control model has been systematically developed utilizing data gathered from a vast array of testing simulations conducted under different and dynamic conditions. The proposed strategy, on the other hand, is compared with the RMS fault detection method in combination with the conventional LVRT algorithm. The NN control approach showed better results as compared to the conventional methods in terms of accuracy and robustness, especially when confronted with difficult sag situations.

Analysis of fault ride through the improvement of PV power plant based on artificial neural network

The increasing adoption of renewable energy sources in industrial areas, driven by the need to both obtain a grid voltage from renewable energy sources and reduce high electricity bills, has led to an increased demand for solutions that can improve the power quality of these systems. A photovoltaic power plant (PVPP) based on a dc-chopper circuit protection system is proposed for the enhancement of the power quality of PVPP. The aim of the presented protection method is to protect the panels in the PVPP from the harmful effects of the high dc voltage that occurs during grid faults. The adaptive neural network control system is applied in both the T-type inverter and the dc-chopper circuit protection system. The proposed protection system is implemented with a 250 kW PVPP to verify its validity with simulation results during grid fault. This approach can potentially improve the reliability and stability of PVPP, and contribute to the maintain of PVPP into the grid.

Design and implementation of electrical engineering experiment based on the Arduino platform

Arduino platform is a new hardware and software combination platform that is widely used, flexible, easy to operate, and rapidly developing. In this paper, the design and implementation of the DC chopper circuit were conducted based on the Arduino platform. Firstly, the power signal and trigger signal are output in the form of programming on the Arduino platform, and the rest of the circuit is built on the breadboard in the form of hardware. Finally, the design waveform is obtained. This paper introduces the basic working principles of four power conversion circuits, conducts circuit simulation on MATLAB software and obtains the ideal output waveform, and uses C language programming to trigger control signal generation, generates corresponding electrical signals through compilation and USB wire transmission to Arduino controller, and builds relevant circuits. This paper makes use of the advantages of the breadboard, fully combines the theoretical knowledge and circuit connection, and finally observes the output waveform through an oscilloscope, and compares the waveform of the actual circuit with the simulation results of MATLAB.

Promoted supercapacitor control scheme based on robust fractional-order super-twisting sliding mode control for dynamic voltage restorer to enhance FRT and PQ capabilities of DFIG-based wind turbine

Aside from the importance of power quality issue, fault ride-through capability is also of greater importance which must be required for doubly-fed induction generator to meet the grid code requirements. Both of these issues can be relatively enhanced using a series-connected power electronic-based compensator styled dynamic voltage restorer. This compensator can present the best compensation performance in case that both the power supply and multilevel inverter parts to be upgraded. In this regard, this paper aims to suggest two novelties:1) New asymmetrical mutual E-type clamped X-type multilevel inverter to provide high-step staircase sinusoidal voltage containing low number of switches2) New robust fractional-order super-twisting sliding mode control for supercapacitor-based power supply to provide steady and smooth DC voltageAs for the creative structure of the proposed inverter, special geometric progression of DC voltage source and low switch count, high-step staircase sinusoidal voltage can be provided. It has been compared with the traditional and recently proposed inverters to validate its step-creation capability.As for the chattering free scheme of the proposed controller, increase of the system freedom degree and robustness against the uncertainties, nonlinearities and perturbations, steady and smooth DC voltage can be provided. It has been compared with PID, SMC and FLC controllers to validate its tracking capability.Both these suggestions have effectively enhanced the AC voltage synthesizer of DVR to accurately and promptly enhance both the FRT and PQ capabilities of DFIG-based wind turbine. The compensation capability of the proposed DVR has been evaluated under different voltage disturbances, and also compared with the conventional DVR and improved series resistive limiter along with superconducting based DC-chopper circuit. Finally, all the disturbance conditions have been perfectly compensated with trivial THD by proposed DVR, and also the DFIG-based wind turbine has been well stabilized.

Coordinated Optimization of DFIG Rotor Crowbar and DC-chopper Resistances Based on NSGA-II

Abstract Low voltage ride-through (LVRT) scheme of doubly-fed induction generator (DFIG) will affect the transient stability of power system since it will change the operation state of wind turbine. The LVRT scheme combining rotor crowbar circuit and Direct Current chopper (DC-chopper) circuit is effective, but the resistances of crowbar and DC-chopper are set separately and the impact on the system transient stability is usually ignored, which makes it difficult to gain optimum control effect. In this paper, the relation between rotor crowbar and DC-chopper in LVRT duration is analyzed in theory, which shows the effect of DC-chopper circuit can be considered as the variation of crowbar in equivalent circuit. Furthermore, by analyzing the effect of crowbar on the LVRT performance and power system transient stability, a coordinated resistance optimization method of crowbar and DC-chopper is proposed. Based on this method, a multi-objective optimization model for crowbar and DC-chopper resistance considering both LVRT performance and system transient stability is established, and the non-dominated sorting genetic algorithms-II (NSGA-II) is applied to solve this multi-objective optimization problem. The simulation results verify that the coordinated optimization scheme will not only achieve better LVRT characteristics, but also improve the transient stability of power system.

Analysis and Experimental Investigation of the Improved Distributed Electronic Load Controller

Stand-alone microhydro systems based on the self-exited induction generator (SEIG) are popular in developing countries. However, an electronic based controller is required to maintain the quality (voltage and frequency) of the generated power within an acceptable range. Conventionally, this controller is designed using a phase-controlled thyristor circuit (or more recently using a dc chopper circuit) and a fixed resistance dump load to receive the excess generated power. Generally, in small communities the total dissipated power in the dump load is greater than the consumed power by all the households. This problem of inefficient power usage can be solved by distributing the controller among households. The objective of this paper is to improve the distributed electronic load controller (DELC). As with the original DELC, the proposed improved DELC is used for two purposes: First, consuming the excess generated power individually by each household; and second, operating as a complementary device for voltage and frequency regulation of the SEIG. The detailed design and experimental verifications of the proposed improved DELC including the design of an appropriate input filter to minimize the network current distortion are presented here. Additionally, MATLAB simulations are used to study the interaction between the proposed improved DELC and the powerhouse controller (the ELC).

Simulation Analysis of DC-DC Circuit Based on Simulink in Intelligent Vehicle Terminal

With the popularization of intelligent transportation systems, intelligent vehicle terminal has emerged. As the most important part of the Intelligent Transportation System (ITS), the smart vehicle-mounted terminal integrates technologies such as the Internet of Things, satellite navigation technology, and even artificial intelligence, and is now widely used in various modes of transportation. The output voltage of automotive vehicle power supplies is generally 12 V, 24 V, 36 V, while the operating voltage of embedded chips inside vehicle-mounted terminals such as automobiles or buses generally needs to be depressurized before they can work normally. Therefore, this paper will analyze four basic DC chopper circuits, analyze its working principle, and build a DC-DC circuit model according to Matlab/Simulink software and finally analyze the waveform of the simulation output.

Enhancing DFIG wind turbine during three‐phase fault using parallel interleaved converters and dynamic resistor

Transient operations are very crucial for high power insulated-gate bipolar transistor modules, because high current and voltage are applied during this period for several microseconds. Therefore, the ability for doubly fed induction generator (DFIG) variable speed wind turbine power converters to withstand abnormal conditions is strictly imperative in order to achieve its lifetime specifications and also fulfil the grid codes. This study presents a new control scheme for DFIG wind turbine having parallel interleaved converters (PIC) configuration and a series dynamic braking resistor (SDBR) connected at its stator side. Interleaving the wind turbine converters in parallel configuration could help to increase the current capability, while the SDBR helps in post fault recovery of the wind turbine. The coordinated control analysis of the scheme was implemented in power system computer aided design and electromagnetic transient including DC simulation environment for a severe three-phase to ground fault. Results obtained were compared with the conventional DC chopper and crowbar rotor circuit protection scheme for the wind turbine. A better performance of the wind turbine variables were achieved using the proposed control scheme of the PIC and SDBR because the space vector modulation of the PIC results in maximum value of the change in common mode voltage, leading to improved switched output voltage of the voltage source converter leg.

Coordinated fault‐ride‐through strategy for doubly‐fed induction generators with enhanced reactive and active power support

With the fault ride through (FRT) requirement of grid codes, wind generators must stay connected and provide the reactive and active power support during and after the grid faults. The doubly fed induction generators (DFIGs) usually employ an active rotor crowbar to ride-through the faults. The solution works well to protect the DFIG itself, but it has shortcomings in the power support. In the paper, a coordinated FRT control strategy is investigated to improve the power support capability of the DFIGs under the fault conditions. In this strategy, a seamless switch is designed to resume the power control mode after the short-term crowbar interruption. Additional compensation terms are inserted into the converter’s control loops to relieve the side-effect of rotor transient current. The coordinated control of dc-chopper circuit and rotor-side converters is proposed to keep the dc-link voltage within its acceptable range. Moreover, a novel voltage limiter is designed with consideration of the conflicting effect of rotor transient current, converter’s rating constraints and desired power goals. Compared with the conventional crowbar-based strategies, the proposed strategy can fully utilise the DFIG’s potential to generate reactive and active power effectively. These performances have been demonstrated through the simulation and experimental tests.

Improved particle swarm optimization for photovoltaic system connected to the grid with low voltage ride through capability

Grid connected photovoltaic (PV) system encounters different types of abnormalities during grid faults; the grid side inverter is subjected to three serious problems which are excessive DC link voltage, high AC currents and loss of grid-voltage synchronization. This high DC link voltage may damage the inverter. Also, the voltage sags will force the PV system to be disconnected from the grid according to grid code. This paper presents a novel control strategy of the two-stage three-phase PV system to improve the Low-Voltage Ride-Through (LVRT) capability according to the grid connection requirement. The non-linear control technique using Improved Particle Swarm Optimization (IPSO) of a PV system connected to the grid through an isolated high frequency DC–DC full bridge converter and a three-phase three level neutral point clamped DC-AC converter (3LNPC2) with output power control under severe faults of grid voltage. The paper, also discusses the transient behavior and the performance limit for LVRT by using a DC-Chopper circuit. The model has been implemented in MATLAB/SIMULINK. The proposed control succeeded to track MPP, achieved LVRT requirements and improving the quality of DC link voltage. The paper shows superiority of IPSO than Incremental Conductance (IC) method during MPPT mode of PV system.

A Modified Switching Control Strategy for Low-Voltage Faults in a Permanent-Magnet Synchronous Generator Wind Turbine System

Grid-connected wind turbines are developing rapidly nowadays, and thus their interactions with the power grid are becoming increasingly important. Grid-friendly wind turbines should possess stable output power, fast dynamic responses, and perfect fault-ride-through capability. This paper focuses on the low-voltage ride-through (LVRT) of a permanent-magnet synchronous generator (PMSG) wind turbine system equipped with fully rated neutral-point-clamped (NPC) converters. We propose a modified control strategy based on rotor-energy storage and the coordinated control of active and reactive power to meet grid interconnection standards. In addition, a dc chopper circuit works as a coordinated protection device for avoiding overspeed. The correctness and feasibility of the proposed control strategy are demonstrated through simulations. The large inertia link of the drive chain could be used to stabilize turbine operation under conditions of power dynamic mutation by taking advantage of its suitability for energy storage, which avoids the wind energy loss.

Dual Analysis of DC Chopper Circuit with LC Input Filter

The Buck circuit has been widely used in DC drive, charging and storage circuit, switching power supply and other power electronic devices. There exists very strong duality in the Buck circuit with input LC filter, especially in the structure of circuit, the equivalent circuits and the waveforms of input and output parts. On the basis of a theoretical model established in our work, an experiment is conducted to validate the equivalent circuits of both input and output parts, as well as the waveforms of associated capacitors and inductors. By choosing appropriate component parameters, the experimental results confirm the predictions of the theoretical model proposed.

Series-Connected IGBTs Using Active Voltage Control Technique

With series insulated-gate bipolar transistor (IGBT) operation, well-matched gate drives will not ensure balanced dynamic voltage sharing between the switching devices. Rather, it is IGBT parasitic capacitances, mainly gate-to-collector capacitance Cgc, that dominate transient voltage sharing. As Cgc is collector voltage dependant and is significantly larger during the initial turn-off transition, it dominates IGBT dynamic voltage sharing. This paper presents an active control technique for series-connected IGBTs that allows their dynamic voltage transition dVce/dt to adaptively vary. Both switch ON and OFF transitions are controlled to follow a predefined dVce/dt. Switching losses associated with this technique are minimized by the adaptive dv/dt control technique incorporated into the design. A detailed description of the control circuits is presented in this paper. Experimental results with up to three series devices in a single-ended dc chopper circuit, operating at various low voltage and current levels, are used to illustrate the performance of the proposed technique.

The NC Power Supply Design of Large Current and Wide Frequency Pulse in SEAM

There are a lot of ways to achieve large current pulse power supply, and the more common way is to adopt the inverter switching circuit to achieve pulse power supply. The core of the NC power supply design of large current and wide frequency pulse in SEAM is using two-stage modulation. Combined with inverter technology, DC chopper technology and NC technology, it not only can achieve the adjustability of the output pulse amplitude, but also can realize continuous adjustment of the output pulses and the duty cycle. The front stage of power supply uses DC/DC transformation circuit with the UC3879 integrated control chip as the core. With the microcontroller as the control core, the backward stage uses DC chopper circuit to achieve the NC power supply of multi-parameter adjustable output large current pulse . DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2812 Full Text: PDF

The NC Power Supply Design of Large Current and Wide Frequency Pulse in Short Electric Arc Machining

There are a lot of ways to achieve large current pulse power supply, and the more common way is to adopt the inverter switching circuit to achieve pulse power supply. The core of the NC power supply design of large current and wide frequency pulse in SEAM is using two-stage modulation. Combined with inverter technology, DC chopper technology and NC technology, it not only can achieve the adjustability of the output pulse amplitude, but also can realize continuous adjustment of the output pulses and the duty cycle. The front stage of power supply uses DC/DC transformation circuit with the UC3879 integrated control chip as the core. With the microcontroller as the control core, the backward stage uses DC chopper circuit to achieve the NC power supply of multi-parameter adjustable output large current pulse.

The Simulation Research of New Induction Heating Power

Along with the maturity of power electronic technology continuously, induction heating technology with its many advantages has been widely used and developed rapidly. However, due to the disadvantages of series resonant induction heating power, such as low input power factor, great grid pollution, it will bring many hazards. This article will make induction heating power network-side input power factor approximate unit power factor with using Active power factor correction technique, and it makes the net side current and voltage be same phase standard sine wave , reduces the network pollution; and with using DC chopper circuit to complete the adjustment of DC voltage, it achieves induction heating power changes. At the same time, using Matlab software for modeling and simulation analysis on the main circuit and control circuit, the simulation results comply with the design requirements and verify the feasibility of the system design.

A Practical Iron Loss Calculation for AC Filter Inductors Used in PWM Inverters

A novel iron loss calculation method is proposed based on an iron loss map for an AC filter inductor used in a pulsewidth-modulation (PWM) inverter. The iron loss map, previously reported by the authors, is created by measuring the dynamic minor loop on the B-H plane, and this is used for the calculation of inductor iron loss in the dc chopper circuit. However, in the case of an AC filter inductor used in a PWM inverter, the iron loss map cannot be directory applied to the iron loss calculation. In this paper, an iron loss calculation for an ac filter inductor is presented by expanding the loss map method. We describe the principle of expansion and the practical procedure for the calculation, which utilizes the loss map and a conventional circuit simulator. Iron loss for the ac filter inductor under some typical modulation methods of the PWM inverter are calculated and discussed with regard to the relation between the modulation methods and iron loss. The calculated results are verified using experimental results from a 500-W inverter setup. The inductor loss and conversion efficiency of the PWM inverter are measured for each modulation method.

A Buck-Boost Type Grid-Connected Inverter

A novel type of inverter is proposed for grid-connection of new energy power generation. The proposed inverter is based on buck-boost operation well-known in DC chopper circuits. This inverter acts as an interface between the generator and the grid and has a distinctive feature of realizing the inverse load flow with a wide range of input DC voltage. A control scheme of DC reactor current is also introduced in order to reduce losses in the DC reactor. The performance and characteristics of the proposed inverter is discussed in computer simulation.

A novel DC chopper drive for a single-phase induction motor

The paper presents a new drive for single-phase induction motors. This drive employs a DC chopper circuit with a diode bridge rectifier connected with the stator in a nonconventional fashion. The speed of the single-phase induction motor is controlled by controlling the chopping frequency of the chopper switch. The attractive feature of the drive is that it effects both frequency and phase-angle control simultaneously. The drive performance has received both theoretical and experimental investigation. >

CHOPPEFtED DC MOTOR DRIVE USING MOS AND BIPOLAR POWER TRANSISTORS

A four quadrant DC chopper circuit is presented applying a combination of MOS and bipolar power transistors as the main power elements. This circuit uses two MOS switches to take all required high frequency (up to 100 KHz) switching in the four quadrant operation. Two bipolar transistors are used in the return path of current as fast contactors to select the required quadrant of operation. Using of this scheme greatly reduces cost than the case of using four MOS switches. Moreover separate fast recovery diodes can be used as freewheeling diodes instead of relatively slower integral body-drain diode of the power MOSFET which cause restrictions on ON state switching speed. In the following work, the detailes of design of power circuit to feed a 20 A- 18V separately excited DC motor is given. Analytical dependence of overall efficiency on operating frequency and battery voltage is discussed. Results show that frequency has a little effect so that a 100 kHz frequency seems to be practically possible with this configuration. Under such high frequency the armature leakage reactance alone is sufficient to draw smooth continuous current to give good motor operating characteristics.