Single-phase PWM Converter Research Articles

Active power decoupling method for single-phase PWM converters without LC branch sensors

Active power decoupling method for single-phase PWM converters without LC branch sensors

An Active Disturbance Rejection Control-Based Voltage Control Strategy of Single-Phase Cascaded H-Bridge Rectifiers

In the traditional control strategy for single-phase PWM converter applications, the proportional-integral (PI) controller has the role of voltage tracking in the outer loop voltage controller, which has limited capability to provide acceptable dynamic performance and disturbance rejection. With regard to this, this article proposes a voltage control strategy based on the active disturbance rejection control (ADRC) for single-phase cascaded H-bridge rectifiers, aiming at achieving satisfactory dynamic performance and strong robustness to the disturbances. First, the extended state observer is used for the state and disturbance estimations. Then, the nonlinear state error feedback deals with the system error and makes the dynamic compensation to the disturbances. More specifically, an improved continuous nonlinear function is adopted to mitigate the jitter behavior of the traditional ADRC and provide immunity to large disturbance errors. Furthermore, the performance and stability analysis of the proposed strategy are implemented. A parameter tuning guideline of the proposed strategy is detailed. The effectiveness of the proposed ADRC-based voltage control strategy is verified through extensive experimental tests and is compared to that of the conventional PI-based voltage control strategy.

불연속 변조 기법을 이용한 고속철도 추진제어장치용 단상 PWM 컨버터

본 논문에서는 불연속 변조 기법을 이용한 고속철도 추진제어장치용 단상 PWM 컨버터에 대해 연구하였다. 기존 PWM 컨버터는 대 전력 특성으로 인해 스위칭 손실을 줄이기 위해 주파수 변조지수를 10 이하로 낮게 사용함에 따라 제어의 대역폭이 감소하고, 안정적인 역률 제어를 위해 추가의 보상 기법을 필요로 하는 등의 문제점을 가지고 있다. 이를 해결하기 위해 3상 PWM 인버터에서 사용하는 불연속 변조 기법을 단상 PWM 컨버터에 적용하였다. 제안한 방식은 옵셋 전압 기법을 활용하여 간단히 구현될 수 있으며 동일 스위칭 손실 대비 주파수 변조 지수를 2배 증가시켜 제어 특성을 향상시키고 스위치 간의 동특성도 동일하게 가져갈 수 있다. 100 kW급 PWM 컨버터에 대한 시뮬레이션을 통해 제안한 불연속 변조 기법에 대한 타당성을 검증하였다. In this paper, for high speed railway propulsion systems, a single phase PWM Converter using discontinuous PWM (DPWM) was investigated. The conventional PWM Converter uses a low frequency modulation index of less than 10 to reduce switching losses due to high power characteristics, which results in low control frequency bandwidth and requires an additional compensation method. To solve these problems, the DPWM method, which is commonly used in three phase PWM Inverters, was adopted to a single phase PWM Converter. The proposed method was easily implemented using offset voltage techniques. Method can improve the control performance by doubling the frequency modulation index for the same switching loss, and can also bring the same dynamic characteristics among switches. Proposed DPWM method was verified by simulation of 100 kW PWM converter.

Ripple Analysis and Control of Electric Multiple Unit Traction Drives under a Fluctuating DC Link Voltage

The traction motors in electric multiple unit (EMU) trains are powered by AC-DC-AC converters, and the DC link voltage is generated by single phase PWM converters, with a fluctuation component under twice the frequency of the input catenary AC grid, which causes fluctuations in the motor torque and current. Traditionally, heavy and low-efficiency hardware LC resonant filters parallel in the DC side are adopted to reduce the ripple effect. In this paper, an analytical model of the ripple phenomenon is derived and analyzed in the frequency domain, and a ripple control scheme compensating the slip frequency of rotor vector control systems without a hardware filter is applied to reduce the torque and current ripple amplitude. Then a relatively simple discretization method is chosen to discretize the algorithm with a high discrete accuracy. Simulation and experimental results validate the proposed ripple control strategy.

전원 전압 왜곡과 주파수 변동 시 단상 PWM 컨버터의 전류 제어

This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.

A Simple Model Predictive Power Control Strategy for Single-phase PWM Converters with Modulation Function Optimization

This paper proposes a simple model predictive direct power control (MP-DPC) of single-phase pulsewidth-modulated rectifiers with constant switching frequency using modulation function optimization. The instantaneous active and reactive power theory for single-phase converters is discussed, on the basis of a second-order generalized integrator. The modulation function is resolved from the cost function of the MP-DPC scheme. The relationship between the instantaneous powers and ac-side inductance mismatch is discussed. The inductance mismatch has an effect on the reactive power, but not effect on active power. The quantitative expression of reactive power caused by inductance mismatch is shown and verified in the experimental test. An inductance parameter online estimation scheme is proposed to eliminate its effect on reactive power. Compared with the conventional proportional-integral-based instantaneous current control scheme and finite-control-set MP-DPC scheme, the proposed MP-DPC can provide these advantageous features: lower current harmonics and total harmonic distortion components, faster dynamic response, fewer adjusted parameters, and zero steady-state error. In addition, the proposed MP-DPC is free of the weighting factor selection in cost function. The effectiveness of the proposed MP-DPC scheme is verified by experimental results.

Novel Third Harmonic Current Injection Technique for Harmonic Reduction of Controlled Converters

Three-phase controlled converters have many applications in the utility interfacing of renewable energy sources and adjustable speed drives as a rectifier or inverter. The utility line currents of these converters have a high harmonic distortion, which is more than the harmonic standards. This paper introduces a new technique for circulating the third harmonic currents from the dc-link to the line currents to reduce their harmonic contents. The proposed system uses a single-phase PWM converter to control the angle and amplitude of the injection current for each of the firing angle of a three-phase converter. A detailed analysis is introduced to achieve a relationship between the firing angle of the three-phase controlled converter and the power angle of the PWM converter. In addition, a detailed design for the other injection path components is introduced. A simulation and experimental work is introduced to prove the mathematical derivations. Analysis, simulation and experimental results prove the superiority of the proposed technique.

Design of Leakage Inductance in Resonant DC-DC Converter for Electric Vehicle Charger

In this paper, the electric charger with single phase PWM converter and a bidirectional half-bridge converter is proposed. A transformer leakage inductance is used for making resonance at the resonant converter, which can make switched current to be sinusoidal without extra inductive component. Both operating principle and design guideline are described in detail. The feasibility for the proposed design is verified through hardware implementation and the experimental results. Detailed results have been obtained to show several advantages such as the compact design and reduced switching losses for different values and conditions of leakage inductance and resonance cases.

왜곡된 전원 전압하에서 Composite 관측기를 이용한단상 PWM 컨버터의 정현파 전류 제어

본 논문에서는 composite 관측기를 이용하여 전원전압 왜곡시 단상 PWM 컨버터의 고성능 전류제어를 제안한다. composite 관측기를 적용함으로써 전원 전압 및 전류의 기본파와 고조파 성분을 시간지연 없이 추출할 수 있다. 추출된 기본파 성분은 전원단의 페이저 각을 찾는 PLL시스템에 이용된다. 멀티 비례-공진 제어기로 단상 입력전류를 정현파로 제어하고 고조파 성분을 제거한다. 시뮬레이션과 실험 결과로 제안된 방법의 타당성을 검증한다. In this paper, a high-performance current control for the single-phase PWM converter under distorted source voltages is proposed using a composite observer. By applying the composite observer, the fundamental and high-order harmonic components of the source voltage and current are extracted without a delay. The extracted fundamental component is used for a phase-lock loop (PLL) system to detect the phase angle of the source voltage. A multi-PR (proportional-resonant) controller is employed to regulate the single-phase line current. The high-order harmonic components of the line current are easily eliminated, resulting in the sinusoidal line current. The simulation and experimental results have verified the validity of the proposed method.

New Controller for Single-Phase PWM Converter Without AC Source Voltage Sensor

In this paper, a new controller for single-phase PWM converter without the ac voltage sensor is described. The proposed controller requires only the dc voltage sensor and the ac current sensor to compensate the power factor and harmonics. Detail simulation model including power circuit and controller was developed to verify the operation of proposed controller. The application feasibility of the proposed controller was verified through experimental works with a prototype. The proposed controller has a simple structure in the point of hardware implementation, and shows excellent performance in normal operation as well as in sudden load change.

A Steady-State Analysis of Three-Phase Inverter-Induction Motor Drive System with a Model of Single-Phase PWM Converter.

A converter-inverter fed induction motor system is widely used for many industrial applications, and a PWM strategy is employed to obtain sinusoidal inputs and outputs. For a railway and a air-conditioner etc., a single-phase PWM converter is often utilized. In the single-phase system, the dc voltage and current are pulsated by the power variation with twice the ac power source frequency. In result, the output waveforms of the inverter are distorted and then a beat phenomenon of an induction motor. The theoretical examinations of this system necessitate complicating the calculations because of the PWM operations of the converter and the inverter.This paper proposes a model for the single-phase PWM converter and deals with the three-phase PWM inverter-induction motor drive system. The models for the voltage source type and the current source type PWM converters, first of all, are given. Next, the inverter-induction motor system is analyzed by employing the model, and the experimental and the calculated waveforms are shown. Finally, the results at the beat operation of the motor are given. A close agreement between the measured and the theoretical results prove the validity of the proposed models for the PWM converters.

Analytical solution to harmonic characteristics of traction PWM converters

The paper presents an analytical technique for calculating the AC input current harmonic spectrum of single-phase PWM converter drives used in railway traction. The technique is based on a 3-D modulation model and the double Fourier series (DFS) method. Formulas in the form of Bessel functions representing the harmonic spectra for several combinations of interlaced PWM converters are derived. These give a useful insight into the harmonic generation and cancellation process which occurs with interlaced configurations. They are also used in a theoretical explanation of the interlacing angle, system parameter symmetry and load balance between interlaced converters. The accuracy of this analytical technique is confirmed by comparing the results with those obtained from a frequency domain model (FDM) of the PWM converter drive.

Phasor-Based Instantaneous Current Control of Single-Phase PWM AC/DC Converter.

This paper presents a current control strategy for a single-phase PWM AC/DC converter. The input current is sinusoidal and an effective power factor is unity. Since the control variables of the single phase converter are sinusoidal, the conventional control strategy requires high control gains to achieve zero steady state error. However, the gains are limited because of sampling delay.To solve the problem, the authors propose a new current control scheme of a single-phase PWM converter which has two special features: One is that a fast response of current is achieved by introducing a converter model in the controller. Another one is that the steady-state AC current control error is canceled even if the parameter differences between the converter model and the actual converter exist. Moreover, the steady-state current error can be eliminated under low gains by a feedback loop of the fundamental component of current error.The experimental data show the proposed control to be effective.

Single-phase PWM converter using balanced two-phase rectification

Energy storage devices, such as inductors or capacitors, are needed in single-phase ac to dc converters because instantaneous power flow of input single-phase ac is inherently pulsating and output dc power must have as little ripple as possible. Energy storage devices (such as smoothing inductors or capacitors) are usually inserted on the dc side. In those converters, energy storage ability of the devices cannot be used effectively, especially when dc power ripple is required to be very small. To solve such a problem, this paper presents novel single-phase ac/dc conversion circuits, in which energy storage devices are used at the ac rather than at the dc side. That is, after converting single-phase ac into balanced (rectangular) two-phase ac using variable reactance element, reconversion of it into dc is carried out. This paper presents a control method for the converters and the variable reactance devices, and performance of the proposed circuits is confirmed using computer simulation.

Single-phase PWM converter using balanced two-phase recification.

Some energy storage devices, such as inductors or capacitors, are needed in single-phase AC to DC converter because instantaneous power flow of input single-phase AC is inherently pulsating and output DC power is required to have as little ripple as possible. Energy storage devices are usually used at the DC side, such as smoothing inductors or capacitors. In those converters, energy storage ability of the devices can not be used effectively, especially when DC power ripple is required to be very small.To solve such a problem, this paper presents novel single-phase AC/DC conversion circuits, in which the energy storage devices are used at the AC side rather than at the DC side. That is, after converting single-phase AC into balanced (rectangular) two-phase AC using variable reactance element, re-conversion of it into DC is carried out.This paper presents control method of the converters and the variable reactance devices, and performance of the proposed circuits are confirmed using computer simulation.

Simulation and Experimental Study of a Reactively Loaded PWM Converter as a Fast Source of Reactive Power

The question of eliminating distorted current waveforms from power networks by active power filters is investigated. If the active current is subtracted from the distorted current, the compensating equipment must be capable of generating the inverse of this difference. Addition of this compensating current to the distorted current then eliminates the distortion. This requires the capability to generate these currents with response times many times less than the fundamental power frequency cycle. This capability is presented by reactively loaded PWM converters. A system configuration with three single-phase PWM converters building a three-phase unit is investigated. The single-phase converter with PWM operation, inductive reactance as load, low-pass input filter, and representative system losses is simulated by state-space techniques. An experimental system of 1 kVA is also constructed for verification. Good correspondence between the simulation and experiment s shown. Starting up the system, compensating the system losses from the supply, and the influence of the control system on the compensating capabilities are investigated. It is concluded that a PWM converter with a reactive load can be used as a fast distortion compensator and that the present state of the art and future development of PWM converter technology will make this technique applicable at least up to 1 Mvar.