A three-phase voltage source PWM rectifier with strong DC immunity based on model predictive control

This paper presents a novel Model Predictive Direct Power Control (MPDPC) approach for the pulse width modulation (PWM) rectifiers in the Aircraft Alternating Current Variable Frequency (ACVF) power system. The control performance of rectifiers may be largely affected by variations in the AC side impedance, especially for systems with limited power volume system. A novel idea for estimating the impedance variation based on the Bayesian estimation, using an algorithm embedded in MPDPC is presented in this paper. The input filter inductance and its equivalent series resistance (ESR) of PWM rectifiers are estimated in this algorithm by measuring the input current and input voltage in each cycle with the probability Bayesian estimation theory. This novel estimation method can overcome the shortcomings of traditional data based estimation methods such as least square estimation (LSE), which achieves poor estimation results with the small samples data set. In ACVF systems, the effect on the parameters estimation accuracy caused by the number of sampling points in one cycle is also analyzed in detail by simulation. The validity of this method is verified by the digital and Hard-in-loop simulation compared with other estimation methods such as the least square estimation method. The experimental testing results show that the proposed estimation algorithm can improve the robustness and the control performance of the MPDPC under the condition of the uncertainty of the AC side parameters of the three-phase PWM rectifiers in aircraft electrical power system.

In this paper, an adaptive voltage-oriented control (VOC) for three-phase grid-connected pulse-width modulation (PWM) rectifier is developed. As the control loop behavior is affected by the PWM rectifier operating conditions, the effects associated to the PWM rectifier losses and uncertainty in the inductance should be inserted in the model. Thus, equivalent resistance and inductance are estimated online by means of an adaptive linear neuron (ADALINE). The proposed ADALINE estimator is inserted in the current control loop to perform an adaptive VOC scheme. Hence, an online updating of the decoupling terms and the current controller gains is achieved. The ADALINE capability to estimate accurately the equivalent inductance and resistance as well as the adaptive VOC scheme performances are finally evaluated by experiments. Experimental results show improved performances and accurate estimation.

In this paper, a dual-converter three-phase pulse width modulation (PWM) rectifier based on unbalanced one-cycle control (OCC) strategy is proposed. The proposed rectifier is used to eliminate the second harmonic waves of DC voltage and distortion of line currents under unbalanced input grid voltage conditions. The dual-converter PWM rectifier employs two converters, which are called positive-sequence converter and negative-sequence converter. The unbalanced OCC system compensates feedback currents of positive-sequence converter via grid negative-sequence voltages, as well as compensates feedback currents of negative-sequence converter via grid positive-sequence voltages. The AC currents of positive- and negative-sequence converter are controlled to be symmetrical. Thus, the workload of every switching device of converter is balanced. Only one conventional PI controller is adopted to achieve invariant power control. Then, the parameter tuning is simplified, and the extraction for positive- and negative-sequence currents is not needed anymore. The effectiveness and the viability of the control strategy are demonstrated through detailed experimental verification.

In this paper, the mathematical model and work principle of the three-phase voltage source pulse width modulation (PWM) rectifier (VSR) are analyzed. Then, the control strategies without feed-forward and with feed-forward are compared, which based on the power factor, the total harmonic distortion (THD) and DC voltage stability. Voltage-Oriented Control (VOC) and direct current control method were adopted to obtain current tracking control. Meanwhile, a simplified algorithm was presented for space vector PWM (SVPWM), which simplifies the arithmetic process. Contrastive analysis of two control strategy results show that without feed-forward control strategy exits the faults of low power factor, high THD and so on, although its model is simple. While feed-forward control strategy has been proved more effective.

In this paper, a modified one-cycle-control (OCC) scheme is proposed for regulating three-phase pulsewidth-modulated (PWM) rectifiers operating under unbalanced and distorted supply conditions. Mathematical analysis is first presented to show the dominant harmonic-voltage components appearing across the dc link of the PWM rectifier when it is controlled by an existing OCC scheme. Such dc-link harmonics when produced may aggravate harmonic currents flowing into the input terminals of the three-phase rectifier. To address these interrelated unbalance and harmonic concerns, the concept of reconstructing the appropriate reference signals in the OCC control core is introduced, before modifications are recommended for altering the key control equation. The improved OCC controller eventually developed is proven to exhibit minimal input-current distortion and a smoother dc-link voltage without using large capacitance. Other advantages exhibited by the traditional OCC scheme, such as no phase-locked loop, no frame transformation, and constant switching frequency, are also retained by the improved controller, whose theoretical findings are fully verified by experimental results obtained from a 1.2-kW three-phase PWM rectifier built in the laboratory.

This paper proposes a modified one-cycle-control (OCC) scheme for regulation of three-phase pulsewidth-modulated (PWM) rectifiers under unbalanced and distorted supply conditions. Mathematical analysis is presented to show the dominant harmonic voltage across the dc-link of PWM rectifier when controlled by the existing OCC scheme. Such ripple voltage may aggravate the harmonic distortion in input currents. To address these problems, the concept concerning with the reconstruction of reference signals in OCC core is introduced. With minor modifications made into the OCC control equation, the overall proposed control scheme can effectively minimize the harmonic components found in the input currents and smoothen output ripple imposed on the dc-link voltage without using large capacitance. Furthermore, previously identified advantages of OCC can all be preserved by the new control scheme. Finally, all the theoretical findings are supported by the experimental results obtained from a 1.2 kW three-phase PWM rectifier developed in the laboratory.

This work proposes a very fast phase angle estimation algorithm for a single-phase system under a sudden phase angle jump condition. When a source voltage changes in a step manner, the normal phase angle detector, such as a phase locked loop (PLL) and a (low pass) filter, typically generates phase delay and results in a sluggish response, and causes some time-critical machine to malfunction. This work proposes a method of estimating the fundamental component, the phase angle and the frequency of a single-phase line voltage without a significant delay, even when the amplitude and the phase angle of the line voltage changes in a step manner, by using the weighted least-squares estimation (WLSE) method with the covariance resetting technique. An example application of a single-phase pulse width modulation (PWM) rectifier for a traction is presented in an appendix. This method can be applied to uninterruptable power supply (UPS), PWM rectifier, active filters, etc.

The model predictive control (MPC) of voltage source pulse width modulation (PWM) rectififier is extremely dependent on system model in control process. System model mismatch will make the prediction results deviate from the actual value, seriously affect the system control results, even caused the system to be unstable. In addition, MPC is a control method based on state space model and predictive state of controlled system. In each control cycle, it performs an ergodic optimization to solve the online optimization, and thus determines optimal driving signal of the switching device. However, to obtain the optimal control variables online usually leads to a high amount of computation, which is one of the difficulties in the implementation of MPC on PWM rectifier. To solve these problems, neural network is used to approximate the unknown functions in system model. A finite set model predictive path integral control (FCS-MPPIC) based on neural network is proposed to effectively decrease computational complexity of control algorithm under premise of ensuring the distortion rate of the grid side current. At the same time, dynamic response speed of the system is improved. Finally, the availability of this method is verified through the simulation results.

In three-phase PWM rectifiers, variations in the dc voltage reference or load can affect the stability and dynamics of the system. Traditional proportional-integral (PI) control has weak adaptability, as its parameters cannot be adjusted in real-time according to the operating state, potentially leading to poor system stability and slow dynamic response. To address these challenges and the complexity of existing PI self-tuning methods, this article proposes a PI self-tuning method based on stability-and-dynamics-constrained fuzzy backpropagation neural network (SDC-FBPNN) for three-phase pulsewidth modulation (PWM) rectifiers. The effect of the right-half-plane zero is considered, and a series compensation method is adopted to convert the non-minimum phase system into a minimum phase system. On this basis, the phase margin and crossover frequency are used as constraints for stability and dynamic performance, respectively. Consequently, PI parameters can be adjusted by the SDC-FBPNN in real-time according to the operation conditions. Under abrupt variations in voltage reference and load, the proposed method significantly reduces voltage fluctuations and shortens the settling time while ensuring system stability. Finally, a 2 kW prototype was built to validate the feasibility and effectiveness of the proposed PI self-tuning method.

This paper discusses reduction of capacitances of dc capacitors in the previously proposed smart charger (SC) with a sinusoidal charging-discharging lithium-ion battery for electric vehicles in single-phase three-wire distribution feeders. The dc-capacitor current of the three-leg pulse-width modulated (PWM) rectifier, which is included in the SC, is detected, and then added to the reference value of the battery-charging or — discharging current for a bidirectional dc-dc converter. Addition of the detected dc-capacitor current to the reference value for the dc-dc converter sinks the voltage ripples in the dc capacitors of both the PWM rectifier and bidirectional converter. This results in a substantial reduction in the capacitances of the dc capacitors. Simulation results demonstrate that balanced source currents with a unity power factor are achieved, reducing the capacitances of the dc capacitors in the previously proposed SC.

This work presents a methodology to apply space vector modulation to unidirectional pulse width modulation (PWM) rectifiers and applied in three different groups of rectifiers. Converter switching stages are analyzed for each group of rectifiers to determine switch control signals for space vector modulation. A switching sequence is proposed to minimize the number of switch commutations and reduce the switching losses. Duty cycle functions are determined and the desired switching sequences are performed by a simple PWM, with no need to determine the present sector of the vector. For this purpose, it is necessary to impose the desired current sectors from input voltage references. Simulation results of proposed modulation techniques are also presented.

Principle and control strategy of pulse width modulation rectifier for hydraulic power generation system

The voltage-regulated pulsewidth-modulated (PWM) rectifier is prone to instability. The system can be stabilized by proportional-plus-integral feedback control, but its transient response is slow. This paper describes results of a study of digital control to improve the system dynamic response by pole placement through state feedback. The control algorithm is implemented for real-time operation by using a custom designed system of three high-speed microprocessors. Results from an experimental study with a 1 kW hardware laboratory model of the PWM rectifier shows that the dynamic response can be significantly improved even when the DC link capacitor is substantially reduced.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New regulation imposes more limits on harmonics injected by Power converters that are achieved with Pulse width Modulation (PWM) Rectifiers. Therefore this paper presents the analysis and control of the three phase Voltage Source PWM rectifiers using Hysteresis Band Current Control technique. The proposed rectifier achieved unity power factor, DC voltage regulation, Line current harmonic mitigation and Bi-directional Power flow. The work is done in Matlab/Simulink environment.

Non-linear loads increase harmonic current of power supply, depress its power factor, and enhance power loss. In order to solve this problem, different kinds of active filtering technologies presently have been widely used in the various power circuits. Because of its complicated control structure and high cost, general active power filter is difficult to apply and popularize. Based on the control strategy of fuzzy proportional and integral (fuzzy-PI), a kind of pulse width modulation (PWM) rectifier with the type of voltage source current control (VSCC) was proposed to act as an active power filter to realize current filtering, ddc link voltage controlling and power factor compensating. The structure of the control system was given and a fuzzy-PI controller was designed, also the devised system was tested and evaluated by real time in an experimental device based on Digital Signal Processor (DSP). The experimental results show that fuzzy-PI control has better dynamic and static performances than traditional PI control, also it has the merits such as simple structure and low cost.