Design method of single-phase inverters for UPS systems

This article presents the complete design of a low power voltage source inverter (VSI) dedicated for a UPS system. The analysis of the rectangular PWM-AC voltage spectrum allows for a choice of the basic architecture of the inverter. Output filter parameters were calculated to reduce the maximum amplitude of the output VSI voltage harmonics for the steady-state inverter mode. The choice of the feedback loop type was based on a discussion of the inverter output impedance using a continuous model of the inverter. The parameters of the inner loop digital control for the discrete inverter model were calculated using the Coefficient Diagram Method. The influence of the step load was modelled. The time constant of the inverter closed loop system was selected to ensure sufficient system robustness. An outer feedback loop with a plug-in repetitive controller, simplified owing to the properties of the PID/CDM inner loop control, was introduced to eliminate the periodic disturbances generated by the non-linear rectifier load and the deadtime influence. The experimental verification of the design method is presented.     

Improved control for high power static var compensator using novel vector product phase locked loop (VP-PLL)

This paper presents a new dual loop control using novel vector product phase locked loop (VP-PLL) for a high power static var compensator (SVC) with three-level GTO voltage source inverter (VSI). From a simple dq-axis equivalent circuit obtained by circuit DQ-transformation method, steady-state analysis is achieved for maximum controllable phase angle α_max per unit current between AC source and switching function of inverter. In addition, the system parameters L and C are designed and thus transient analysis is made for open-loop transfer function. This paper proposes software VP-PLL for more accurate α control than conventional hardware PLL because α_max becomes very small in high power SVC. Therefore, the overall controller has dual loop structure of inner VP-PLL for synchronizing the phase angle with AC source and outer Q-loop for compensating reactive power of load. Finally, the usability of the proposed control method is verified through the experiment of 100kvar power capacity with both stand alone and load linked operation.     

基于STM32F103ZET6的程控单相AC-DC变换电路设计

本设计以STM32F103ZET6微控制器和功率因数校正芯片UCC28019为核心,搭建了基于功率因数校正（PFC）的升压式（Boost）拓扑结构AC-DC变换电路,负载调整率和电压调整率均接近规定要求。芯片UCC28019内部采用电压外环和电流内环的双环控制策略,使输出电压稳定在36 V;单片机STM32F103ZET6通过功率因数测量电路实时测出功率因数并且测量误差绝对值不低于0.03。系统的功率因数大于0.98,电路效率接近95%,且具有过流保护和自动启动的功能。     

Finite control set predictive control of shunt hybrid power filter

This paper proposes a finite control set predictive control (FCS-PC) scheme for the shunt hybrid power filter (SHPF) to reduce the power loss while maintaining satisfactory power quality at the utility’s grid terminals. By means of the instantaneous power theory, the controller for the proposed method can generate the reference voltage for the SHPF voltage source inverter (VSI) for the future sampling time. Therefore, during a sampling time, the vector of the reference voltage is compared with the finite number of voltage vectors existent in the VSI to select the vector that best fits the cost function of the controller. The proposed method, compared with the conventional pulse width modulation (PWM) carrier method, has the capability of suppressing similarly the harmonic currents at grid terminals and controlling VSI DC-link voltage while maintaining low switching frequencies in the devices. This method shows simplicity in digital implementation because it does not need a PWM block to obtain the VSI gating signals. In addition, a comparison of the proposed FCS-PC method with the conventional carrier-based PWM method is presented and discussed. Parameter errors in the controller are studied and their effects on system performance are explained. The effectiveness of the proposed method is demonstrated with simulation and experimental results during steady-state operation and transient response of the system.     

Analysis and design of a multiple feedback loop control strategyfor single-phase voltage-source UPS inverters

This paper presents the analysis and design of a multiple feedback loop control scheme for single-phase voltage-source uninterruptible power supply (UPS) inverters with an L-C filter. The control scheme is based on sensing the current in the capacitor of the load filter and using it in an inner feedback loop. An outer voltage feedback loop is also incorporated to ensure that the load voltage is sinusoidal and well regulated. A general state-space averaged model of the UPS system is first derived and used to establish the steady-steady quiescent point. A linearized small signal dynamic model is then developed from the system general model using perturbation and small-signal approximation. The linearized system model is employed to examine the incremental dynamics of the power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS system. Experimental verification of a laboratory model of the UPS system under the proposed closed-loop operation is provided for both linear and nonlinear loads. It is shown that the control scheme offers improved performance measures over existing schemes, It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of filter parameters. Furthermore, the scheme has excellent dynamic response and high voltage utilization of the DC source     

3C strategy for inverters in parallel operation achieving an equalcurrent distribution

A circular chain control (3C) strategy for inverters in parallel operation is presented in the paper. In the proposed inverter system, all the modules have the same circuit configuration, and each module includes an inner current loop and an outer voltage loop control. A proportional-integral controller is adopted as the inner current loop controller to expedite the dynamic response, while an H^∞ robust controller is adopted to reach the robustness of the multimodule inverter system and to reduce possible interactive effects among inverters. With the 3C strategy, the modules are in circular chain connection and each module has an inner current loop control to track the inductor current of its previous module, achieving an equal current distribution. Simulation results of two-module and a three-module inverter systems with different kinds of loads and with modular discrepancy have demonstrated the feasibility of the proposed control scheme. Hardware measurements are also presented to verify the theoretical discussion     

高压断路器三相永磁无刷直流电机机构控制算法研究

针对高压断路器三相永磁无刷直流电机机构,研究了不同控制策略下电机操动机构的运动特性.考虑高压断路器的分、合闸操作过程,建立了永磁无刷直流电机操动机构运动控制系统的仿真模型,采用数字式双闲环控制,内环为电流环,采用PI控制,外环为速度环,基于传统PID控制器、单神经元PID控制两种不同控制策略控制.通过对伺服控制系统的仿真分析得到了电机操动机构速度跟踪控制特性.结果表明,单神经元PID控制器能够较好的实现触头速度的跟踪控制,使其按理想运动特性曲线运动,是一种较理想、有效的控制方法.     

Single-Loop Current Sensorless Control for Single-Phase Boost-Type SMR

In this paper, the first single-loop current sensorless control (SLCSC) in continuous current mode (CCM) for single-phase boost-type switching-mode rectifiers (SMRs) is developed and digitally implemented in a DSP-based system. Compared to the conventional multiloop control with one inner current loop and one outer voltage loop, there is only one voltage loop in the proposed SLCSC, where the voltage loop's output is used to shift the nominal duty ratio pattern generated from the sensed input and output voltages. Because of no current loop, the efforts of sampling and tracking inductor current can be saved. It implies that the proposed SLCSC is simple and very adaptable to the implementation with mixed-signal ICs. First, the effects of shifting nominal duty ratio pattern on the input current waveform are analyzed and modeled by considering the inductor resistance and conduction voltages. The result of analysis shows that the pure sinusoidal current can be inherently generated by the nominal duty ratio pattern where the current amplitude is roughly proportional to the controllable phase of nominal duty ratio pattern. Then, a voltage controller is included to regulate the dc output voltage by tuning this controllable phase. Finally, some simulated and experimental results have been given to demonstrate the performance of the proposed SLCSC.      

Implementation of a neural network tracking controller for a singleflexible link: comparison with PD and PID controllers

The objective of this paper is to show the results of the practical implementation of a neural network (NN) tracking controller on a single flexible link and compare its performance to that of proportional derivative (PD) and proportional integral derivative (PID) standard controllers. The NN controller is composed of an outer PD tracking loop, a singular perturbation inner loop for stabilization of the fast flexible-mode dynamics, and an NN inner loop used to feedback linearize the slow pointing dynamics. No off-line training or learning is needed for the NN. It is shown that the tracking performance of the NN controller is far better than that of the PD or PID standard controllers. An extra friction term was added in the tests to demonstrate the ability of the NN to learn unmodeled nonlinear dynamics     

A mixed-mode PWM controller

In this article, a mixed-mode (MM) PWM controller for dc–dc power converter topologies is presented and analysed. Compared to the conventional peak current-mode (PCM) controller, the proposed controller exhibits better results in terms of robustness towards load and reference voltage variations while maintaining better dynamic response. In the PCM controller, the control signal is a combination of inductor or, most often, switch current and a suitable compensation ramp which in the most common applications is constant. In the proposed controller, the constant compensation ramp has been replaced by a ramp voltage which is proportional to the output voltage taking into consideration the output voltage variations during load and reference transients. Consequently, the proposed controller, which exhibits the same advantages as with the PCM controller, additionally exhibits better load and reference performance for constant output voltage and output tracking applications without increasing the cost and the complexity of the control circuit. Finally, in order to verify the theoretical analysis and conclusions, both control schemes (i.e. PCM and MM) have been simulated and experimentally tested using a 75 W buck converter unit.     

Implementation of a New Linear Control Technique Based on Experimentally Validated Small-Signal Model of Three-Phase Three-Level Boost-Type Vienna Rectifier

In this paper, the design and implementation of a new multiple-input-multiple-output linear control technique based on a theoretically established and experimentally validated small- signal model for the three-phase three-level boost-type ac/dc Vienna converter are presented. Averaging and local linearization techniques are used to derive the dynamic model expressed in the dqo reference frame. The resulted transfer functions are discretized for the sake of a digital controller design. Multiple-loop control strategy is adopted and consists of inner current feedback loops, which are based on the straightforward looping technique that neglects interactions between the dq components of control inputs and currents, respectively, and of an outer voltage loop, which is designed to ensure dc voltage regulation by adjusting the magnitude of the references for the inner current loops. The output dc voltage unbalance is also controlled in the inner loops. The proposed modeling and control approaches are first simulated and then validated on a 1.5-kW laboratory prototype supported by the DS 1104 digital real-time controller board of dSPACE. The obtained results prove the accuracy of the proposed new small-signal model and, therefore, its reliability for dynamic analysis and control design purposes. It is also proved that a judicious choice of controller parameters, as well as an adequate rating of boost inductors, allows one to meet the IEEE standard requirements in terms of ac line-current total harmonic distortion and power factor. The efficiency of the proposed control technique is maintained in case of disturbances occurring on both source and load sides.     

PWM整流器的PI^λ D^μ控制策略

针对常规控制适用场所的局限性,提出了一种基于分数阶控制的PWM整流方法,该方法有别于以往的双闭环控制策略,电流内环控制使用分数阶控制器取代传统控制器。通过MATLAB/Simulink仿真与实验验证了该控制策略的控制效果明显好于传统控制方法。此外,其不仅可以应用在控制精度要求高、控制参数多的非线性系统中,而且具有较好的跟随性、鲁棒性和稳定性,能够准确的跟踪指令电流,并且得到的网测电流谐波很少,近似于正弦波。     

三相电压型PWM整流器控制新技术的研究

根据电压型PWM整流器在同步旋转dq坐标系中建立的整流器电流控制数学模型,基于电流前馈解耦,解决了有功电流和无功电流互为耦合问题。为克服直流电压响应较慢、抗扰性较差的不足,提出了采用电流内环、基于滑模控制的电压外环电压型PWM整流器的新控制策略。由于采用滑模控制的电压外环,提高了整流器直流电压跟踪和电流跟踪能力,使系统具有响应快、稳定性好、抗负载扰动能力强的优点。文中给出了系统控制器的设计方法。通过正常负载及负载扰动情况下的计算机仿真,证明了新控制策略的可行性。     

Boost DC-AC inverter: a new control strategy

Boost dc-ac inverter naturally generates in a single stage an ac voltage whose peak value can be lower or greater than the dc input voltage. The main drawback of this structure deals with its control. Boost inverter consists of Boost dc-dc converters that have to be controlled in a variable-operation point condition. The sliding mode control has been proposed as an option. However, it does not directly control the inductance averaged-current. This paper proposes a control strategy for the Boost inverter in which each Boost is controlled by means of a double-loop regulation scheme that consists of a new inductor current control inner loop and an also new output voltage control outer loop. These loops include compensations in order to cope with the Boost variable operation point condition and to achieve a high robustness to both input voltage and output current disturbances. As shown by simulation and prototype experimental results, the proposed control strategy achieves a very high reliable performance, even in difficult transient situations such as nonlinear loads, abrupt load changes, short circuits, etc., which sliding mode control cannot cope with.     

A New Control Technique for Three-Phase Shunt Hybrid Power Filter

This paper presents a nonlinear control technique for a three-phase shunt hybrid power filter (SHPF) to enhance its dynamic response when it is used to compensate for harmonic currents and reactive power. The dynamic model of the SHPF system is first elaborated in the stationary “abc” reference frame and then transformed into the synchronous orthogonal “dq” reference frame. The “dq” frame model is divided into two separate loops, namely, the two current dynamic inner loops and the dc-voltage dynamic outer loop. Proportional–integral (PI) controllers are utilized to control the SHPF input currents and dc-bus voltage. The currents track closely their references so that the SHPF behaves as a quasi-ideal current source connected in parallel with the load. It provides the reactive power and harmonic currents required by the nonlinear load, thereby achieving sinusoidal supply currents in phase with supply voltages under dynamic and steady-state conditions. The SHPF consists of a small-rating voltage-source inverter (VSI) in series with a fifth-harmonic tuned $LC$ passive filter. The rating of the VSI in the SHPF system is much smaller than that in the conventional shunt active power filter because the passive filter takes care of the major burden of compensation. The effectiveness of the control technique is demonstrated through simulation and experimentation under steady-state and dynamic operating conditions.      

Adaptive output voltage tracking controller for uncertain DC/DC boost converter

This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.     

三相并网逆变器的双环控制策略研究

由于对高频谐波的抑制效果明显好于L型滤波器,因此LCL滤波器在电流源控制的并网逆变器中应用越来越广泛。而针对该类型的并网逆变器的控制策略更为复杂,为了简化控制策略一种基于电流双环的并网控制方案被提出来。与电压电流的双环控制器设计方法不同,设计电流双环控制器参数时除了考虑内外环控制器的相互影响以外,还需要考虑双环控制器带来的降阶和少自由度问题。因此本文在介绍基于高阶极点配置的电流双环控制器设计方法的基础上,重点分析在电流双环控制带来的少自由度的情况下如何合理的设计控制器参数。实验结果表明,根据该方案设计的控制器参数能够使三相并网逆变器安全、可靠运行且具有较快的动态响应速度。     

A Voltage-sensorless control method to balance the input currents of a three-wire boost rectifier under unbalanced input Voltages condition

This paper proposes a control method that can balance the input currents of the three-phase three-wire boost rectifier under unbalanced input voltage condition. The control objective is to operate the rectifier in the high-power-factor mode under balanced input voltage condition but to give overriding priority to the current balance function in case of unbalance in the input voltage. The control structure has been divided into two major functional blocks. The inner loop current-mode controller implements resistor emulation to achieve high-power-factor operation on each of the two orthogonal axes of the stationary reference frame. The outer control loop performs magnitude scaling and phase-shifting operations on current of one of the axes to make it balanced with the current on the other axis. The coefficients of scaling and shifting functions are determined by two closed-loop proportional-integral (PI) controllers that impose the conditions of input current balance as PI references. The control algorithm is simple and high performing. It does not require input voltage sensing and transformation of the control variables into a rotating reference frame. The simulation results on a MATLAB-SIMULINK platform validate the proposed control strategy. In implementation Texas Instrument's digital signal processor TMS320F240F is used as the digital controller. The control algorithm for high-power-factor operation is tested on a prototype boost rectifier under nominal and unbalanced input voltage conditions.     

Electronic Ballast Control IC With Digital Phase Control and Lamp Current Regulation

A digital control architecture is presented for electronic ballasts that provides a phase sweep for reliable, soft lamp ignition and a smooth transition to lamp current regulation mode. The controller is based on an inner phase loop for fast regulation of the resonant tank operating point and an outer current loop for lamp current regulation. The inner loop operates on a simple digital control law that computes the required gate timing relative to the inductor current positive zero crossing. Phase control provides reliable drive of the resonant converter in the presence of large dynamic changes in the load impedance during lamp ignition and warm up and natural tracking of component variations with temperature and time. The primarily digital approach provides programmability for broad application, insensitivity to process and temperature variations, realization in low cost CMOS processes and few external components. Experimental results are presented for an integrated ballast controller fabricated in a 0.8 mum CMOS process used in a 400 W, 150 kHz HID electronic ballast.     

A New Multilevel Conversion Structure for Grid-Connected PV Applications

A novel scheme for three-phase grid-connected photovoltaic (PV) generation systems is presented in this paper. The scheme is based on two insulated strings of PV panels, each one feeding the dc bus of a standard two-level three-phase voltage-source inverter (VSI). The inverters are connected to the grid by a three-phase transformer having open-end windings on the inverter side. The resulting conversion structure performs as a multilevel power active filter (equivalent to a three-level inverter), doubling the power capability of a single VSI with given voltage and current ratings. The multilevel voltage waveforms are generated by an improved space-vector-modulation algorithm, suitable for the implementation in industrial digital signal processors. An original control method has been introduced to regulate the dc-link voltages of each VSI, according to the voltage reference given by a single maximum power point tracking controller. The proposed regulation system has been verified by numerical simulations and experimental tests with reference to different operating conditions.