On the DSP-based switch-mode rectifier with robust varying-band hysteresis PWM scheme

This paper presents the development of digital signal processor (DSP) based switch-mode rectifier (SMR) with robust varying-band hysteresis current-controlled (HCC) pulse width modulated (PWM) schemes. First, a robust fixed-frequency HCC PWM control scheme is developed. Through robust harmonic spectrum shaping, the constant frequency control performance is insensitive to the changes of system parameters and operating condition, and the low frequency harmonics possess smaller magnitudes. Next, the robust HCC PWM schemes of SMR with linearly and randomly varying hysteresis bands are proposed. The harmonic spectra of the SMR are shaped to be uniformly distributed. As to the output voltage regulation control, the dynamic plant model is first estimated. Then accordingly, the controller is quantitatively designed to meet the prescribed control requirements. Significant power quality improvement in line drawn current for the SMR is achieved by using the developed HCC PWM schemes.     

Random vibration test control of inverter-fed electrodynamic shaker

The random vibration control of an inverter-fed electrodynamic shaker is presented in this paper. First, the dynamic model of the shaker is found and a current-controlled pulsewidth modulation inverter is designed and implemented. The feedback controller is augmented with a command feedforward controller and a disturbance feedforward controller to let the armature exciting current have low harmonic content and possess excellent waveform tracking performance. Then, an acceleration controller and its random vibration command are arranged. In the proposed acceleration control scheme, a command feedforward controller and a robust disturbance feedforward controller are also employed to let the shaker have close random acceleration command waveform tracking control performance, and the performance be insensitive to the system parameter variations. It follows that the acceleration control with desired frequency response in a vibration test could be achieved through properly setting the command signal. The effectiveness of the proposed control scheme is verified by simulation and measured results     

Novel space vector based current controllers for PWM-inverters

Two novel, simple control strategies for current-controlled pulse-width modulated (PWM) transistor inverters are presented. Both methods are based on the three-level hysteresis comparators which select appropriate inverter output voltage vectors via a switching electrically programmable read-only memory (EPROM) table. The first controller works with current components represented in a stationary coordinate system (AC components) and the second with components represented in a rotated (field-oriented) coordinate system (DC components). The theoretical principles of these methods are discussed. The results of a comparative study, which illustrates the performance of the proposed controller in comparison to the most popular scheme (based on three independent two-level hysteresis comparators), are presented     

A new single-phase five-level PWM inverter employing a deadbeat control scheme

A single-phase five-level PWM inverter is presented to alleviate harmonic components of the output voltage and the load current. Operational principles with switching functions are analyzed. To keep the output voltage sinusoidal and to have the high dynamic performances even in the cases of load variations and the partial magnetization in filter inductor, the deadbeat controller is designed and implemented on a prototype. The validity of the proposed inverter is verified through simulation and experiments. To assess the proposed inverter, it is compared with the conventional single-phase three-level PWM inverter under the conditions of identical supply DC voltage and switching frequency. In addition, it is compared with the five-level cascaded PWM inverter.     

A three-phase active power filter operating with fixed switchingfrequency for reactive power and current harmonic compensation

The performance and dynamic characteristics of a three-phase active power filter operating with fixed switching frequency is presented and analyzed in this paper. The proposed scheme employs a PWM voltage-source inverter and has two important characteristics. First, it operates with fixed switching frequency, and second, it can compensate the reactive power and the current harmonic components of nonlinear loads. Reactive power compensation is achieved without sensing and computing the reactive component of the load current, thus simplifying the control system. Current harmonic compensation is done in time domain. The principles of operation of the proposed active power filter along with the design criteria of the power and control circuit components are discussed in detail. Finally, experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed system     

Vibration acceleration control of an inverter-fed electrodynamicshaker

Concerns control of an electrodynamic shaker for vibration-proof testing of electronic products. An acceleration controller for such a shaker fed by a switching-mode power amplifier is presented in this paper. First, the dynamic model of the shaker system is found and a high-performance current-controlled pulsewidth modulated inverter is designed and implemented. Then, a sophisticated acceleration control scheme being capable of waveform and magnitude regulation controls is proposed to lessen the undesired harmonic vibration caused by switching-mode driven power. In acceleration waveform control, the feedback controller is augmented with a feedforward controller and robust controller for obtaining excellent waveform tracking performance over a wide frequency range. As to the magnitude regulation control, the amplitude of the sinusoidal acceleration is accurately controlled to be equal to the setting value. Theoretical basis, practical consideration, and implementation of the proposed controllers are described in detail. Good current and acceleration control characteristics of the designed shaker are demonstrated by some measured results     

A fully digital hysteresis current controller for an active power filter

An active power filter is used to eliminate current harmonics produced by nonlinear loads. This paper discusses a fully digital method of controlling a power inverter used to inject the active filter compensating currents into the power system. A digital signal processor performs the harmonic isolation and generates a digital reference current. A hysteresis current controller has been implemented in a field programmable gate array that generates the inverter switching signals using this reference. This reduces the analogue circuitry and enhances the system's immunity to electromagnetic interference. The performance of a small-scale inverter under completely digital control is presented and discussed.     

High-performance programmable AC power source with low harmonicdistortion using DSP-based repetitive control technique

This paper proposes a new control scheme based on a two-layer control structure to improve both the transient and steady-state responses of a closed-loop regulated pulse-width-modulated (PWM) inverter for high-quality sinusoidal AC voltage regulation. The proposed two-layer controller consists of a tracking controller and a repetitive controller. Pole assignment with state feedback has been employed in designing the tracking controller for transient response improvement, and a repetitive control scheme was developed in synthesizing the repetitive controller for steady-state response improvement. A design procedure is given for synthesizing the repetitive controller for PWM inverters to minimize periodic errors induced by rectifier-type nonlinear loads. The proposed control scheme has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. A 2-kVA PWM inverter has been constructed to verify the proposed control scheme. Total harmonic distortion (THD) below 1.4% for a 60-Hz output voltage under a bridge-rectifier RC load with a current crest factor of 3 has been obtained. Simulation and experimental results show that the DSP-based fully digital-controlled PWM inverter can achieve both good dynamic response and low harmonics distortion     

Paralleled DSP-based soft switching-mode rectifiers with robust voltage regulation control

This paper presents the current sharing and robust voltage regulation controls for paralleled digital signal processor-based soft switching-mode rectifiers (SSMRs). First, the design and implementation of single-module SSMRs are made. In dealing with the current control loop design of each SSMR module, the small-signal model is derived and used to design the current-controlled pulse-width modulation (PWM) scheme. As to the common voltage control loop, its dynamic model is estimated from measurements. Then, a quantitative design procedure is developed to find the parameters of the voltage controller according to the prescribed control specifications. As the changes of parallel number and operating condition occur, the robust control is added to reduce the voltage regulation control performance degradation. The proposed multimodule operation control scheme consists of a master controller and N slave controllers. The former further consists of a common voltage controller and a current distribution unit, and the latter are the current-controlled PWM schemes of all SSMRs. Each slave controller receives the weighted sinusoidal current command from the master controller and regulates the feedback current of SSMR. The results confirm that the designed parallel SSMR system possesses good line drawn current power quality, module current sharing and voltage regulation control performances.     

A constantly sampled current controller with switch status dependent inner bound

In this paper, a constantly sampled current-controlled pulsewidth-modulation (PWM) strategy is proposed such that the controlled current can follow the command within a specified error bound to guarantee the desired good power quality. According to different previous switch statuses, a different inner bound is proposed for current error comparison to add the zero-mode control at the proper time to further reduce the switching frequency. Moreover, an analytic expression of the upper bound of the constant sampling period for the current controller to guarantee the desired performance is derived and some design criteria are given for proper coordination among the circuit parameters. Finally, some simulation and experimental results are given to demonstrate the validity of the proposed current-controlled PWM scheme.     

Adaptive repetitive control of PWM inverters for very low THDAC-voltage regulation with unknown loads

An adaptive repetitive control scheme is proposed and applied to the control of a pulsewidth-modulated (PWM) inverter used in a high-performance AC power supply. The proposed control scheme can adaptively eliminate periodic distortions caused by unknown periodic load disturbances in an AC power supply. The proposed adaptive repetitive controller consists of a voltage regulator using state feedback control, a repetitive controller with tuning parameters and an adaptive controller with a recursive least-squares estimator (LSE). This adaptive repetitive controller designed for AC voltage regulation has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. Experimental verification has been carried out on a 2 kVA PWM inverter. Simulation and experimental results show that the DSP-based adaptive repetitive controller can achieve both good dynamic response and low total harmonic distortion (THD) under large-load disturbances and uncertainties     

Design and implementation of an FPGA-based control IC forAC-voltage regulation

This paper presents a field-programmable gate army (FPGA)-based control integrated circuit (IC) for controlling the pulsewidth modulation (PWM) inverters used in power conditioning systems for AC-voltage regulation. We also propose a multiple-loop control scheme for this PWM inverter control IC to achieve sinusoidal voltage regulation under large load variations. The control scheme is simple in architecture and thus facilitates realization of the proposed digital controller for the PWM inverter using the FPGA-based circuit design approach. Bit-length effect of the digital PWM inverter controller has also been examined in this paper. The designed PWM inverter control IC has been realized using a single FPGA XC4005 from Xilinx Inc., which can be used as a coprocessor with a general-purpose microprocessor in application of AC-voltage regulation. Owing to the high-speed nature of FPGA, the sampling frequency of the constructed IC can be raised up to the range that cannot be reached using a conventional digital controller based merely on microcontrollers or a digital signal processor (DSP). Experimental results show the designed PWM inverter control IC using the proposed control scheme can achieve good voltage regulation against large load variations     

An adaptive hysteresis-band current control technique of avoltage-fed PWM inverter for machine drive system

An adaptive hysteresis-band control method where the band is modulated with the system parameters to maintain the modulation frequency to be nearly constant is described. Although the technique is applicable to general AC motor drives and other types of load, an interior permanent magnet (IPM) synchronous machine load is considered. Systematic analytical expressions of the hysteresis band are derived as functions of system parameters. An IPM machine drive system with a voltage-fed current-controlled PWM (pulse width modulation) inverter has been computer simulated to study the performance of the proposed method     

Three-Level Inverter-Based Shunt Active Power Filter in Three-Phase Three-Wire and Four-Wire Systems

This paper presents a direct current-space-vector control of an active power filter (APF) based on a three-level neutral-point-clamped (NPC) voltage-source inverter. The proposed method indirectly generates the compensation current reference by using an equivalent conductance of the fundamental component using APF's dc-link voltage control. The proposed control can selectively choose harmonic current components by real-time fast Fourier transform to generate the compensation current. The compensation current is represented in a rotating coordinate system with chosen switching states from a switching table implemented in a field-programmable gate array. In addition, a three-phase four-wire APF based on a three-level neutral-point-clamped inverter is also presented. The proposed APF eliminates harmonics in all three phases as well as the neutral current. A three-phase three-wire NPC inverter system can be used as a three-phase four-wire system since the split dc capacitors provide a neutral connection. To regulate and balance the split dc-capacitor voltages, a new control method using a sign cubical hysteresis controller is proposed. The characteristics of the APF system with an LCL-ripple filter are investigated and compared with traditional current control strategies to evaluate the inherent advantages. The simulation and experimental results validated the feasibility of the proposed APF.      

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 of a series resonant converter pulse width-modulated orcurrent-controlled for low switching loss

Pulse width modulation (PWM) and current-controlled switching are applied to a full-bridge series resonant converter to regulate the output from no load to full load with low switching loss and with a narrow range of frequency variation. Drive strategies, control law, component stress, and other steady-state functions are analyzed for both switching modes. The range of frequency variation of the resulting switching scheme is narrower than that of a normal square-wave drive. It is noted that the advantages of low switching stress and narrow band frequency variation can be extended over the entire range of voltage gain or load by combining PWM with current-controlled switching     

A novel space-vector current regulation scheme for afield-oriented-controlled induction motor drive

The system performance of an AC variable-speed drive directly depends on the current regulation. In this paper, a novel space-vector current regulation scheme for a field-oriented controller (FOC) is developed. Motor currents are regulated by generating appropriate inverter output voltage vectors via software-implemented comparators and a switching table. A switching table based on the angular coordinate enables the inverter to generate optimal voltage vectors. By introducing an additional triangular carrier signal to the output of original hysteresis comparators, a user-selectable high and fixed switching frequency can be obtained, further improving the driver performance. Experiments are made to verify the effectiveness and correctness of this proposed method. According to the experimental results, both simple hardware design and good current response can be attained     

Two-level switching pattern deadbeat DSP controlled PWM inverter

A two-level switching algorithm of the deadbeat controlled PWM inverter is presented. Two levels, instead of three levels, are used in the pulse pattern. This scheme allows the use of higher switching frequency for a given computation time delay, which results in lower total harmonic distortion (THD) at the output. Control algorithms are derived. The proposed control scheme is implemented using a TI TMS320C14 DSP controlling an inverter to produce a very low THD sinusoidal output voltage. Simulation and experimental results are presented to verify the performance     

Sliding-mode control of boost-type unity-power-factor PWMrectifiers

A robust sliding-mode controller, suitable for the output voltage control of voltage-sourced unity-power-factor three-phase pulsewidth modulation (PWM) rectifiers, presenting no steady-state errors, is described. This “just-in-time” switching controller controls the output voltage and the line input currents, while providing bidirectional power flow, near-unity-power-factor operation, low harmonic content, fast dynamic response of the output voltage, and minimum switching frequency due to a new α-β space-vector current regulator. The voltage controller performance is compared with the behavior of the conventional proportional integral output voltage control, aided by PWM current-mode modulators, and with the nonrobust fast and slow manifold sliding-mode approach. The comparison shows that the proposed controller confers faster dynamics and does not present steady-state errors. Test results confirm that the performance of the controller is independent of system parameters and load and exceeds the performance of existing hysteretic current-mode control systems     

一种新型恒频滞环电流控制策略研究

并联型有源电力滤波器的变环宽滞环电流控制方法是根据电流幅值的变化适时调整滞环宽度,可有效保证滤波器的补偿性能,控制开关器件的开关频率。在传统的变环宽滞环电流控制算法的基础上,加入了电流限幅和频率PI反馈控制环节,限制了较大电流的波动,提高了频率的控制精度,以及有源电力滤波器的电流补偿性能。Matlab仿真结果表明,采用新型恒频滞环电流控制算法进行电流跟踪补偿时,系统的电流总畸变率小于采用传统变环宽滞环电流控制算法时的总谐波畸变率。