Instantaneous Voltage Control Research Articles

A Generalized Multilevel Inverter With Extended Linear Modulation Range and Instantaneously Balanced DC-Link Series Capacitors for an Induction Motor Drive

The voltage drift control of series-connected capacitors across a single dc-link is the major challenge for a multineutral point-clamped (NPC) converter. This drifting is caused due to uneven currents drawn from the neutral points (NPs) during the PWM operation. This work presents the working principle of instantaneous voltage control of “ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> ” dc-link series-connected capacitors for an induction machine load. The mechanism of instantaneous voltage balancing is realized by ensuring zero instantaneous currents at each dc-link NP. To get zero instant currents at a dc-link NP branch, the phase terminals tapping on the dc-link are manipulated with the help of cascaded hybrid bridges (CHBs). Charge balancing of CHB capacitors is also taken care of by proper utilization of pole voltage redundancies. The detailed results are presented for a small-scaled inverter (nine-level) with three NPs (four dc-link capacitors). The simulation and experimental results reflect the capability and limitations of such inverters. The results are presented at all modulation indexes operated under low-power-factor (LPF) and high-power-factor (HPF) load conditions. It is found that the linear modulation range (LMR) can be increased to full base speed even for an HPF load.

Single‐phase small capacitor motor drive system with high‐efficiency buck active power decoupling converter

This paper proposes a novel active power decoupling circuit (APDC) based on modified Buck converter to reduce the DC-link voltage ripple of small capacitor motor drive systems. The APDC is placed between the Boost PFC circuit and the DC-link, and has two energy flow paths, and the sum of the power decoupling capacitor and the DC-link capacitor voltage equals to the output voltage of the Boost converter. With these configurations, the voltage of the decoupling capacitor can be precisely controlled to be the same as the AC component of the output voltage of the Boost converter, thereby effectively reducing the DC-link voltage ripple. Another unique feature of the proposed APDC is that the inductor works in discontinuous current mode and only work for half of the time, which not only reduces the current stress of power switches, but also further improves the efficiency of the proposed APDC. Then, an instantaneous voltage control method is investigated to reduce the DC-link voltage drop, which significantly improve the dynamic performance of the motor. The design guideline of key components is given in detail. The feasibility of the small capacitor motor drive system based on the proposed APDC is verified by experimental results.

Improving voltage of remote connection using wind‐solar farms equipped with new voltage control strategy based on virtual impedance monitoring enabled by IEC 61850 communication

This study explores how the voltage control of a remote part of the utility gird can be improved using more sophisticated voltage control on wind-solar farms equipped with fast communication platforms. The idea is to make renewable plant the master voltage controller during large disturbance events in the grid. This is done by proposing an enhanced voltage droop control strategy based on instantaneous reactive power consumption by monitoring the virtual impedance of the point of connection using a new customised data class model of IEC 61850 communication protocol. The conventional centralised voltage droop control strategy and the proposed instantaneous direct voltage control method are both implemented on the White Rock Solar Wind Farm in NSW, Australia and their performances are compared using both MATLAB Simulink simulations under 5% voltage step disturbances, single-phase-to-ground and three-phase-to-ground faults as well as some tests conducted in the field.

Instantaneous direct voltage and frequency control in DC grid tied DFIG based wind energy system

The paper presents a new configuration of DFIG based wind energy system which belongs to the connection with the DC grid/bus. The presented configuration of DFIG based wind energy systems is kind of stand-alone DC-DFIG based system where: (i) The load replaces the utility grid; (ii) the rotor is connected to the DC grid/bus/micro-grid via rotor side converter. Being a stand-alone DC-DFIG based system, only voltage and frequency regulation is considered here in this research. The rotor side converter provides the controlled amplitude & frequency of the rotor current for regulating the stator side voltage magnitude and frequency. Also, a simple and easy to implement in hardware as well as in software control technique for the rotor side converter, based on root mean square detection of stator/load voltage, is proposed in this study. The proposed configuration is found suitable in the areas having low-to-medium wind speed. The MATLAB Simulink model of 2 MVA DFIG has been considered to evaluate the performance of the system. Also, hardware set-ups comprise with (i) 3.2 kW DFIG (ii) DC shunt motor, and (iii) FPGA Altium NanoBoard3000 controller, are considered to reveal the effectiveness of the proposed configuration and controller in real time environment.

Control Strategy Design of Grid-Connected and Stand-Alone Single-Phase Inverter for Distributed Generation

Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 ㎸A prototype demonstrate the effectiveness of the proposed control strategy.

Cascaded Bidirectional Converter Topology for 700 W Transformerless High Frequency Inverter

Home inverter is an important system which provides uninterrupted power supply for domestic requirements. Most of the existing systems use line frequency transformers to generate the desired sinusoidal voltage and exhibit poor load regulation and efficiency. Under spurious conditions, reliable and stable operation of the inverter is a primary requirement. In this paper, 3-stage bidirectional (boost and buck) cascaded converter topology is proposed to boost an input battery voltage from 12 to 375 V and vice-versa. DC link is connected to H-bridge converter to obtain a desired sinusoidal output voltage. In the topology, first and third stages are non-isolated boost converters and second stage is a buck derived push–pull converter. Push–pull configuration of the 2nd stage provides electrical isolation to source from high voltage DC bus. Cascaded DC–DC converter outputs are regulated by designing an average current mode control and instantaneous voltage control is designed for H-bridge inverter. Hardware is designed and developed using digital signal controllers to supply 700 W domestic load. Experiments are conducted for different linear, nonlinear and dynamic load variations.

Implementation of modified current synchronous detection method for voltage control of self‐excited induction generator

This study presents a modified current synchronous detection method for voltage control of self-excited induction generator (SEIG)-based standalone power generating system using a static reactive power compensator (STATCOM). The proposed STATCOM is a three-leg insulated gate bipolar transistor-based voltage source inverter with self-sustaining DC-bus capacitor. The STATCOM offers instantaneous voltage control of SEIG through reactive power compensation. In addition to voltage control, the STATCOM also provides load balancing under unbalanced loadings and harmonics compensation while feeding non-linear loads. The control of STATCOM is implemented using a modified current synchronous detection algorithm that uses a second-order generalised integrator (SOGI) to filter the sensed SEIG voltages and for estimating the amplitudes of individual phase voltages. The performance of the proposed SOGI-CSD-based control of STATCOM is simulated in MATLAB/Simulink and verified experimentally on a developed SEIG-STATCOM system. Test results exhibit effective harmonics suppression and load balancing capabilities of the STATCOM along with instantaneous voltage control.

A Simple Control Scheme for the High Performance Z-Source Inverter

In the past decade, the Z-source inverter (ZSI) is successfully developed for many applications. This paper proposes a simple integrated control scheme for the high performance ZSI. A proportional-integral PI controller is used to regulate the voltage of the Z-network capacitor. Moreover, the peak value of the DC-link voltage is controlled by limiting the shoot-through duty ratio. Furthermore, the instantaneous voltage control technique is utilized to retain the sinusoidal shape of the output voltage. A feed-forward signal of the AC voltage is employed to smooth the output voltage. To generate the PWM signals for the ZSI switches, the simple boost control method is utilized which coordinates the operation of different controllers. Extensive digital simulations are conducted to evaluate the dynamic behavior of the proposed control scheme. Moreover, an experimental setup is built to verify the performance of the proposed control scheme for the high performance ZSI.

簡易型予測瞬時値制御を適用した自立電源システム向け三相電流形インバータの定常特性

簡易型予測瞬時値制御を適用した自立電源システム向け三相電流形インバータの定常特性

A current ripple reduction of a high-speed miniature brushless direct current motor using instantaneous voltage control

High-speed miniature brushless direct current motor (BLDCM) is used in robots and medical applications because of its high-torque and high-speed characteristics. When compared with the general BLDCM, a high-speed miniature BLDCM has a low electrical time-constant. The current and torque ripple are very high when compared with the conventional pulse-width modulation (PWM) control scheme in the conduction period because of the inherent electrical characteristics. The authors propose a simple instantaneous source voltage and phase current control for torque ripple reduction of a high-speed miniature BLDCM. To reduce the switching current ripple, instantaneously controlled source voltage is supplied to the inverter system according to the motor speed and the load torque. In addition, a fast hysteresis current controller can keep the phase current within a limited band. Computer simulations and experimental results up to 40 000 rpm show the effectiveness and verification of the proposed control scheme.

직접 순시전압 제어기법에 의한 동기발전기의 고성능 여자 제어시스템

This paper presents a simple, robust excitation control system for synchronous generator using direct instantaneous voltage control(DIVC) method DIVC method can operate as maximum dynamics of power conversion system without any control gains such as PID controller. And the transient overshoot of generator voltage can be suppressed with a simple time constant. The proposed control scheme is verified by the computer simulation and experimental results in prototype generation system.

Study on Instantaneous Voltage Control Method for Auxiliary Power Supply Systems Used in Rolling Stocks.

Study on Instantaneous Voltage Control Method for Auxiliary Power Supply Systems Used in Rolling Stocks.

Small battery energy storage system

A small battery energy storage (BES) system is proposed. The power circuit of this BES system is simple, since only one current-forced subharmonic PWM switching converter is used. The precise current control is achieved by applying feedforward control. If the utility power is off, the BES system operates in the inverter mode to supply power to the load. A sinusoidal output voltage with low distortion and good regulation is obtained by using instantaneous voltage control and average voltage control techniques. When the utility power recovers, the BES system minimises the power from the utility to the load in the peak load period. Conversely, the power from the BES system is minimised in the medium load period. During the off-peak load period, the utility supplies power to the load and also charges the battery bank. In addition to real power conditioning, the BES system can also compensate the load reactive and harmonic powers. Thus the current waveform and the power factor on the utility grid are much improved. The modelling, design and implementation of the proposed controllers are described and some experimental results are given to show the performance of this BES system.

An AC voltage switching regulator with instantaneous output voltage control

This is the first attempt to control the instantaneous output of an ac/ac direct power converter. The ac chopper-type regulator has the potential ability of quick response to the control command. However, detecting the mean or effective value of the ac output voltage, as is commonly done in the conventional closed-loop ac regulators, greatly degrades the inherent fast response capability of the chopper circuit. The proposed ac switching regulator adopts the Cuk converter for the main circuit and an instantaneous voltage control technique. A practical state feedback scheme together with the integral control was devised to stabilize the system and also minimize the steady-state error. The response speed is so fast (about 300 μs with resistive load) that the converter can produce a sinusoidal output voltage even from a distorted source voltage. The four-quadrant operation can handle any kind of ac load. A complete analytical description and relevant design data of this new regulator are provided with some experimental results.

Parallel processing inverter system

A novel method of instantaneous voltage and power balance control of a parallel processing inverter system is proposed. It consists of a high-speed switching PWM (pulsewidth modulated) inverter with an instantaneous current minor loop controller, a voltage major loop controller, and a power balance controller. This system realizes the following functions with only one inverter: constant AC output voltage control with reactive power control, active filtering to absorb load current harmonics, DC voltage and current control as AC-to-DC converter, and uninterruptible power supply (UPS) for stand-alone operation. This system covers a wide application range, including UPS systems, new energy systems, and active filters with voltage control functions. >

Design and implementation of a single phase current-forced switching mode bilateral convertor

A single-phase switching mode bilateral convertor using current-forced hysteresis switching control is designed and successfully implemented. The power circuit configuration is simple, since only one full-bridge convertor is required, and the lock-out circuits are not necessary. Based on the proposed current-forced switching scheme, the bidirectional power flow is very easy to control and the switching voltage jumps and losses can be reduced. Moreover, the line current can be sinusoidally regulated with unity power factor in the rectifier mode, and the voltage waveform distortion can be kept small in the inverter mode by instantaneous voltage control. To perform the control system design, the transfer function models of the proposed convertor system in two operation modes are built up, and then a generalised systematic design method is proposed to find the parameters of the controllers according to the prescribed specifications. Some experimental results are provided to demonstrate the effectiveness of the proposed convertor.

An AC voltage switching regulator with instantaneous output voltage control.

This is the first attempt of controlling the instantaneous output voltage of an AC/AC direct power converter. The AC chopper-type regulator has the potential ability of quick response to the control command. However, detecting the mean or effective value of the AC output voltage, as is commonly done in the conventional closed-loop AC regulators, greatly ruins the inherent fast response capability of the chopper circuit.The proposed AC switching regulator adopts the _??_uk converter for the main circuit and an instantaneous voltage control technique. A practical state feedback scheme together with the integral control was devised to stabilize the system and also minimize the steady state error. The response speed is so fast (about 300μs with resistive load) that the converter can produce a sinusoidal output voltage even from a distorted source voltage. The four quadrant operation can handle any kind of AC load. A complete analytical description and relevant design data of this new regulator are provided with some experimental results.