Space vector modulation applied to star, delta and bridge connected unidirectional PWM rectifiers

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.

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.

A Pulse Width Modulation (PWM) rectifier with strong DC disturbance rejection is presented based on Model Predictive Control (MPC). The design of outer voltage square loop and inner current loop using model predictive control is presented, where voltage square loop indicates the square of output DC voltage calculated to be linear with active current. A discrete-time model of the rectifier is constructed to predict the future current for all voltage vectors. Then, one voltage vector minimizing the current errors is selected by solving the cost function. Two weighting matrices, which affect the performance of the rectifier greatly, are used in the cost function to weight prediction error and control actions. This paper indicates the function of the two different weighting coefficients and the way to choose proper weighting factors on a typical three phase PWM rectifier under different conditions. The static, dynamic, pre-charging performance and anti-disturbance ability are discussed upon the proposed rectifier model. The results are proved by simulation that the proposed method can achieve strong DC immunity and a fast dynamic performance with pre-charging strategy compared to the traditional method.

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, a new virtual flux (VF) based predictive direct power control (VF_PDPC) applied for three-phase pulse width modulation (PWM) rectifier is proposed. The virtual flux estimation is performed using a pure integrator in series with a new adaptive algorithm in order to cancel dc offset and harmonic distortions in the estimated VF. The introduced structure is able to produce two virtual flux positive sequence components orthogonal output signals under unbalanced and distorted voltage conditions. The main features of the proposed virtual flux estimator are, it's simple structure, accuracy, and fast VF estimation over the excited integrators. Therefore, the estimated VF is then used for robust sensorless VF-PDPC with a constant switching frequency using space vector modulation (SVM) and tested through numerical simulations. The instantaneous active and reactive powers provided by orthogonal (VF) positive sequence components are directly controlled. More importantly, this configuration gives quasi-sinusoidal and balanced current under different input voltage conditions without using the power compensation methods. The results of the simulation confirmed the validity of the proposed virtual flux algorithm and demonstrated excellent performance under different input voltage conditions, complete rejection of disturbances.

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.

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

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.

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.

Pulse width modulation (PWM) rectifiers can be used to regulate the input power quality of variable frequency drives (VFDs). While current techniques like passive filtering and current injection networks suffer from bulkiness, complexity, and performance issues at light loads. PWM technique provides less load-dependent performance. This paper introduces a study of improving the input power quality of a single phase to three phase rectifier-inverter structured VFD by using bridgeless dual boost (BLDB) PWM converter. Design and simulation of the proposed AC-DC converter are provided.

Predictive direct power control (P-DPC) has been proposed as an effective solution to regulate the instantaneous power of pulse-width modulated (PWM) rectifiers without using the inner current controller and the phase lock loop (PLL). Deadbeat P-DPC is one category of P-DPC. It utilizes the predictive model of PWM converters to calculate the equivalent voltage reference that nullifies the power error in every control cycle. As compared with conventional table-based DPC (TB-DPC), the deadbeat approach guarantees a better tracking performance and operates at a fixed switching frequency. This paper further improves the performance of the deadbeat P-DPC by introducing a simple geometrical modulation as an alternative to the conventional space vector modulation (SVM). The proposed geometric method aims to reduce the control complexity whilst maintaining the good performance of the deadbeat P-DPC. Both simulation and experimental results are provided to demonstrate the validity of the improved deadbeat P-DPC with geometrical modulation.

This paper presents a power converter configuration interfaced with the distributed ac power generation system to regulate the dc bus voltage. It is composed of a pulsewidth modulation (PWM) rectifier directly tied to the generator's terminals without ac reactors. Hence terminal voltages are not useful due to the switched pulse of the PWM rectifier and also it is not the terminal voltages, but the generator's electromagnetic field voltages that are required for a synchronous angle of the PWM rectifier. This paper proposes a method for estimating the synchronous angle through only the measurement of the ac line currents, and is thus called the voltage sensorless control strategy. For a smooth startup of the PWM rectifier, a technique of setting the integrators' initial values in the proposed estimator is described. In this paper a commercial engine generator set is used as the distributed generation system. The feasibility of the overall system and algorithms has been verified by the experimental results

Modulation techniques for current source inverters (CSIs) have traditionally been derived from those used for voltage source inverters (VSIs), with space vector modulation (SVM) and pulse width modulation (PWM) being the most popular. Among these, PWM is the preferred choice due to its simplicity and ability to offer the same benefits as SVM, such as increased phase voltage. Ideally, PWM from VSIs could be directly applied to CSIs, but this is not feasible because CSIs require a holistic consideration of all switches on the upper (positive) and lower (negative) rails. In contrast, VSIs allow for per-phase modulation, which enables the straightforward use of a PWM modulator. In this paper, a PWM method tailored specifically for CSIs without any requirements typical for SVM, such as sector identification, is proposed. Using linear algebra, a technique for generating duty cycles averaged over a switching frequency period is derived. These duty cycles are then fed into a specially for CSIs proposed multi-threshold pulse width modulator, which finally produces the gate signals. To validate our method, both simulation and extensive experimental results are presented. The proposed approach is general and applicable to CSIs with any number of phases.