Taotao Jin

One-cycle control of three-phase active power filter with vector operation

Active power filters (APFs) provides an effective measure to eliminate the power line harmonic/reactive currents generated by nonlinear loads or by distributed energy sources that are connected to the grid. Active power filters are typically connected in parallel to the harmonic/reactive current sources and cancel the harmonic/reactive components in the line current so that the current flow into and from the grid is sinusoidal and in phase with the grid voltage. Since the APFs process only the harmonic/reactive power, their power-handling capability can be much higher than that of the cascade power-factor-correction methods. In this paper, the one-cycle control method is extended to control three-phase APFs. The proposed control approach employs one integrator with reset along with several logic and linear components to control a voltage-source converter to achieve three-phase unity power factor for the current to and from the power grid. No multipliers or sensors for the load current and the APF inductor current are required. Furthermore, there is no need to calculate the reference for controlling APF inductor current so that complicated digital computation is eliminated. The operation switching frequency is constant that is desirable for industrial applications. The proposed control approach features great simplicity, excellent harmonic/reactive current cancellation, and solid stability. It is a cost-effective solution for power quality control for electronic equipment, buildings, industrial facilities, ships, airplanes, distributed power generation stations, etc. All findings are supported by experimental results.

Operation of One-Cycle Controlled Three-Phase Active Power Filter With Unbalanced Source and Load

The power quality of the ac electric system has become a great concern due to the rapidly increasing numbers of electronic equipment being connected to the grid. In order to reduce harmonic contamination in power lines and to improve its transmission efficiency, the research on active power filters (APF) has become a hot topic. Many control methods for APF were proposed in recent years. Among them, one-cycle control (OCC) has shown great promise featuring excellent harmonic suppression, simple circuitry, robust performance, and low cost for the control of three-phase APFs. Theory and experiments in previous papers have demonstrated the validity of OCC-controlled APFs working with balanced line voltages and balanced nonlinear loads. However, in reality, neither three-phase grid voltages nor three-phase nonlinear loads are balanced at all times; therefore, it is vital for an APF to be able to handle unbalanced sources and/or loads. In this paper, the OCC-controlled three-phase APF working with unbalanced three-phase line voltages and unbalanced loads are studied, respectively. Theoretical analyses and experimental results indicate that with OCC control, sinusoidal input currents can be realized, whether the input voltages and/or the nonlinear loads are balanced or unbalanced

A new interleaved isolated boost converter for high power applications

Isolated boost converter is desirable in the low-to-high dc/dc application where isolation is required or a large step up is in a need. The challenge of designing such a converter for high power applications is how to handle the high current at the input and high voltage at the output. An effective way is to parallel the inputs and series the outputs of the isolated boost converters. Based on this concept, a new interleaved and isolated boost converter is proposed in this paper that has two inductors in parallel at the input to share the current and two capacitors in series at the output to share the voltage. The current stresses and voltage stresses of the converter are both alleviated. The two boost converter cells realize demagnetizing by helping each other, which simplifies the transformer structures. With interleaved operation, the current ripple is smaller; therefore, it is possible to use smaller capacitors at the input and output of the converter. All these features make the new interleaved isolated boost converter desirable for high power low-to-high dc/dc applications. The proposed interleaved isolated boost converter is presented based on the basic isolated boost converter, but the interleaved structure is applicable to other isolated boost converters including the full-bridge converter, the push-pull converter, and the L-type half-bridge converter. The theoretical analysis is verified by a 200W prototype.

A Universal Vector Controller for Four-Quadrant Three-Phase Power Converters

Power factor corrected (PFC) rectifiers, active power filters (APFs), static VAR compensators (STATCOM), and grid-connected inverters (GCI) are indispensable elements in distributed generation power systems. PFC rectifiers are essential for load side harmonic and reactive power correction, APFs can suppress the harmonics generated by nonlinear loads or sources, STATCOMs can control the power flow in the grid, while GCIs are the key elements bridging the renewable energy sources and the power grid. Previous theory and experiments have demonstrated that one-cycle control is capable of controlling all above mentioned three-phase converters, featuring excellent performance, simple circuitry, and low cost. This paper further unifies the control key equations for the previously mentioned converters, which results in a universal solution that realizes all these functions with a same controller. The concept has been verified by a 1-kVA prototype and supported by a series of experimental results

Multiphase LLC Series Resonant Converter for Microprocessor Voltage Regulation

In order to further reduce the power loss, and increase the computation speed, future microprocessors desires lower voltage, higher current, tighter voltage regulation, and faster transient from their voltage regulators. In the last decade, interleaved buck converters have been studied and used extensively for powering microprocessors. Due to their inherent limitations in current sharing, capacitor size, step down ratio, and energy flow pattern, it becomes very difficult for interleaved buck converters to keep up with the demands of the future microprocessors. In this paper, a new candidate, a multiphase LLC resonant converter is proposed, which features zero voltage switching for both inverter and rectifier switches; wide load range; limited frequency range; fast dynamic response; high efficiency; and automatic current sharing. These features ensure the proposed multiphase LLC resonant converter a good voltage regulator candidate for the next generation microprocessors. All theoretical analyses are verified by a 1 V 50 W prototype and its experimental results

A universal vector controller for three-phase PFC, APF, STATCOM, and grid-connected inverter

Power factor corrected (PFC) rectifiers, active power filters (APF), STATCOMs, and grid-connected inverters are indispensable elements in distributed generation (DG) power systems. PFC rectifiers are essential for load side harmonic and reactive power correction, Active power filters can be used to suppress the harmonics generated by nonlinear loads or sources, STATCOMs can be used to control the power flow in the grid, while grid-connected inverters are the key elements bridging the renewable energy sources and power grid. The theory and experiments have demonstrated that one-cycle control is capable of controlling three-phase PFCs, APFs, STATCOMs, and grid connected inverters, featuring excellent performance, simple circuitry, and low cost. While the control principles for these DG applications are the same, the previously reported implementation circuits differ from each other in some degree, a fact which may results in several different control chips for the three-phase DG applications. In this paper, the control key equations and circuits for one-cycle controller controlled PFC, APF, STATCOM, and grid connected inverter are reviewed, then based on the observation a universal control circuit has been developed, further study indicates that the new control circuit can be easily integrated into one chip to control all above converters. Finally the concept was verified by experimental and simulation results.

Operation of unified constant-frequency integration controlled three-phase active power filter with unbalanced load

The theory and experiments have demonstrated that the unified constant-frequency integration (UCI) controller features excellent performance, simple circuitry, and low cost for the control of three-phase APF connected to either symmetrical or asymmetrical three-phase power systems. In reality, three-phase grid voltages and/or three-phase nonlinear loads may not be balanced all the time, therefore it is vital for an APF to be able to handle unbalanced source or load. Studies have shown that the UCI controlled APF performs satisfactorily in unbalanced systems. In continuation, the performance of a three-phase APF working in unbalanced load with a UCI controller is evaluated in this paper. Simulation and experiment results indicate that with UCI control, sinusoid input current can be realized, whether the loads are balanced or unbalanced.

Control and topologies for three-phase three-level active power filters

Active power filters have been reported effective in eliminating the reactive and harmonic current in the power lines. Most previously proposed methods are based on two level inverters and thus are suitable for low voltage use. In this paper, topologies and control are proposed for three-level three-phase active power filters that expend the voltage and power to the levels desirable for industrial applications. The proposed three-phase active power filter with one-cycle control features high voltage operation with reduced voltage stress on the semiconductor components and simple control circuitry that needs no reference calculation, dq conversion, nor multipliers. Laboratory experimental results based on a 1 kW prototype have demonstrated excellent harmonic suppression capability and rigid robustness.

New Three-phase Inverter for UPS application

This paper proposes a new three-phase inverter for UPS application. The control of the proposed inverter is based on circuit-level decoupling (Salmon, 1996 and Qiao and Smedley, 1999) instead of d/q conversion; its implemented by appropriate logic circuitry in combination with a control-core and a PID compensator. The control-core can be implemented by one-cycle controller (OCC), pulse-width modulation (PWM) controller, hysteresis controller and current-programmed mode (CPM) controller, etc. Superior performance such as low THD, fast dynamic response, as well as low switching loss has been demonstrated. The proposed concept is supported by simulation and experimental results from 1kW prototypes built and tested under all loading conditions i.e. zero load, full load and non-linear load. With OCC control-core, it has the added strength of full rejection of input voltage perturbations as well as the ability to track abrupt reference change

New Three-phase Inverter with Dual-Loop Compensator

This paper proposes a new three-phase inverter [11] for voltage generation. The control of the proposed inverter is based on circuit-level decoupling instead of d/q conversion; it is implemented by appropriate rotary logic circuitry in combination with control-core and dual-loop feedback compensator. Control-core can be implemented by One-Cycle Controller (OCC) and Pulse-Width Modulation (PWM) controller. Dual-loop feedback compensator is implemented with switching component of Ic as feedback variable. Superior performance such as low THD, fast dynamic response, as well as low switching loss has been demonstrated. Yet the implementation is simple and flexible. The proposed concept is supported by simulation and experimental results from a 1kW prototype. The prototype is tested under all loading conditions, i.e. no load, full load and non-linear load. With OCC control-core, it has the strength of full rejection of input voltage perturbations as well as the ability to track abrupt reference change. With dual-loop compensator, it can achieve satisfactory output voltage regulation at low switching frequency.