Unified Constant-frequency Integration Research Articles

Cross-Connected Source Multilevel Inverter for Active Power Filtering Using Unified Constant-Frequency Integration Control

This paper proposes an Active Power Filter (APF) system which utilizes a five-level nonconventional Cross-Connected Source Multilevel Inverter (CCSMI) with a modified Unified Constant-Frequency Integration (UCI) control. The CCSMI consists of six power switches which can produce five output voltage levels. With the use of the CCSMI, the parts count is reduced with equivalent or better performance compared to the use of conventional multilevel inverters. The capability of the proposed system is tested using three types of nonlinear loads with different characteristics. The APF system is simulated under steady-state condition using MATLAB/Simulink. The results obtained show improvement in the supply current Total Harmonic Distortion (THD) with room for enhancement, using the proposed APF system.

Acoustic Noise Reduction of BLDC Motor Drive Using One-Cycle Current Control Strategy

Torque ripple and resulted acoustic noise and vibration are the main disadvantages of brushless DC (BLDC) motor drives. In this study, One-Cycle Control (OCC) is developed for current regulation of brushless DC (BLDC) motor drive as a unified constant-frequency integration control strategy. Employing one-cycle control strategy reduces high frequency torque ripple of conventional hysteresis current controllers leading to lower acoustic noise and vibration in the drive. To enhance reliability and reducing drive cost, an improved rotor position estimation technique is implemented. OCC strategy and sensorless method are realized using a low-cost general-purpose AVR microcontroller (Atmega8). It is shown that torque ripple, acoustic noise and vibration are reduced via OCC method comparing to conventional hysteresis control strategy. Computer simulations and experimental results with a 375W, 16 poles BLDC motor, demonstrate improved behavior of developed sensorless BLDC drive operation.

PLL-Less Active Power Filter Based on One-Cycle Control for Compensating Unbalanced Loads in Three-Phase Four-Wire System

In this paper, a shunt active power filter (APF) based on unified constant frequency integration or one-cycle control (Smedley et al., 2001) for compensating unbalanced loads in a three-phase four-wire system is explored. The APF provides compensation currents in such a way that the utility supplies only the balanced fundamental current at unity power factor, even if the load draws reactive and harmonic currents. The scheme neither requires the service of a phase-locked loop nor requires to sense the utility voltages. This makes the scheme insensitive to the distortions that are generally present in the utility voltages. First, the one-cycle control technique is applied to a topology involving a four-leg converter for the proof of concept. Then it is utilized to control a conventional three-leg converter having a split-capacitor dc link. The effectiveness and the viability of the schemes are demonstrated through detailed simulation and experimental verification.

Three-phase unity-power-factor star-connected switch (VIENNA) rectifier with unified constant-frequency integration control

A unified constant-frequency integration (UCI) controller for a three-phase star-connected switch three-level rectifier (VIENNA) with unity-power-factor-correction is proposed. One of advantages of this rectifier is that the switch voltage stress is one half of the total output voltage. The proposed control approach is based on one-cycle control and features great simplicity and reliability: all three phases will be power factor corrected using one or two integrators with reset along with several flips-flops, comparators and logic and linear components. It does not require multipliers to scale the current reference according to the output power level as used in many other control approaches. In addition, the input voltage sensor is eliminated. It employs constant switching frequency modulation that is desirable for industrial applications. The proposed controller can operate by sensing either the inductor currents or the switching currents. If the switching currents are sensed, the cost is further reduced because switching currents are easier to sense comparing with inductor currents. The proposed approach is supported by experimental results.

Unified constant-frequency integration control of three-phase standard bridge boost rectifiers with power-factor correction

In this paper, a three-phase six-switch standard boost rectifier with unity-power-factor correction is investigated. A general equation is derived that relates the input phase voltages, output DC voltage, and duty ratios of the switches in continuous conduction mode. Based on one of the solutions and using one-cycle control, a unified constant-frequency integration controller for PFC is proposed. For the standard bridge boost rectifier, a unity power factor and low total harmonic distortion can be realized in all three phases with a simple circuit that is composed of one integrator with reset along with several flips-flops, comparators, and some logic and linear components. It does not require multipliers and three-phase voltage sensors, which are required in many other control approaches. In addition, it employs constant-switching-frequency modulation that is desirable for industrial applications. The proposed control approach is simple and reliable. All findings are supported by experiments.

Three-phase bipolar mode active power filters

In this paper, a unified constant-frequency integration control method for a three-phase bipolar mode active power filter is proposed. The proposed control method eliminates the use of any multipliers, the need of sensing three-phase load current, and the nontrivial task of calculating the harmonies and reactive current components, as required by previously reported control methods. By applying one-cycle control and sensing the mains line current, unity power factor and low input current distortion can be realized by one integrator with reset along with a few linear components such as flip-flops, comparators, and clock. The proposed controller is simple, robust, and reliable. All findings are supported by simulation and experiments.

Unified constant-frequency integration control of active power filters-steady-state and dynamics

An active power filter (APF) is a device that is connected in parallel to and cancels the reactive and harmonic currents from a group of nonlinear loads so that the resulting total current drawn from the AC mains is sinusoidal. This paper presents a unified constant-frequency integration (UCI) APF control method based on one-cycle control. This method employs an integrator with reset as its core component to control the pulse width of an AC-DC converter so that its current draw is precisely opposite to the reactive and harmonic current draw of the nonlinear loads. In contrast to previously proposed methods, there is no need to generate a current reference for the control of the converter current, thus no need for a multiplier and no need to sense the AC line voltage, the APF current, or the nonlinear load current. Only one AC current sensor is used to sense the AC main current and one DC voltage sensor is used to sense the DC capacitor voltage. The control method features constant switching frequency operation, minimum reactive and harmonic current generation, and simple analog circuitry. It provides a low cost and high performance solution for power quality control. Steady-state and dynamic study is presented in this paper. Design example is given using a two-level AC-DC boost topology. A prototype was developed to demonstrate the performance of the proposed APF. This control method is generalized to control a family of converters that are suitable for APF applications. All findings are supported by experiments and simulation.