Leong Soon Toh

A bidirectional high-frequency link inverter using center-tapped transformer

In this paper, a bidirectional high-frequency link inverter is proposed. The main feature of the inverter is that the electrical isolation is provided by a high-frequency center-tapped transformer. Furthermore, the sinusoidal pulse width modulation method is modified so that the transformer can be utilized near to its full potential. As a result, the power switches count is reduced, and the efficiency increased. A 1 kW prototype inverter is built and typical results are presented.

High-Frequency Transformer-Link Inverter with Regenerative Snubber

This work proposes a bidirectional high-frequency link inverter using center-tapped high-frequency transformer. The topology also incorporates a regenerative snubber to clamp the high voltage spikes due to the leakage inductance of the transformer. The closed-loop control method used is deadbeat control, which provides fast response and low harmonic distortion, even under nonlinear loads. A 1 kVA prototype inverter is built and the workability of the system is experimentally verified

A bidirectional inverter with high frequency isolated transformer

There is a growing interest to develop renewable energy, particularly the solar energy to meet the growing energy demand. In this paper, a bidirectional photovoltaic (PV) inverter using high frequency (HF) transformer is proposed. The HF transformer provides electrical isolation between the DC supply and AC output. Besides, by using minimum power switches at the active rectifier on the secondary side of HF transformer, the system has low switching losses. Therefore, the proposed inverter has advantages of reliable, lightweight, low cost and increased efficiency. A prototype inverter is implemented using a low cost microcontroller and laboratory experiments are carried out to verify the system viability.

AC Voltage Regulation of a Bidirectional High-Frequency Link Converter Using a Deadbeat Controller

This paper presents a digital controller for ac voltage regulation of a bidirectional high-frequency link (BHFL) inverter using deadbeat control. The proposed controller consists of inner current loop, outer voltage loop and a feed-forward controller, which imposes a gain scheduling effect according to the reference signal to compensate the steady-state error of the system. The main property of the proposed controller is that the current- and the voltage-loop controllers have the same structure, and use the same sampling period. This simplifies the design and implementation processes. To improve the overall performance of the system, additional disturbance decoupling networks are employed. This takes into account the model discretization effect. Therefore, accurate disturbance decoupling can be achieved, and the system robustness towards load variations is increased. To avoid transformer saturation due to low frequency voltage envelopes, an equalized pulse width modulation (PWM) technique has been introduced. The proposed controller has been realized using the DS1104 digital signal processor (DSP) from dSPACE. Its performances have been tested on a one kVA prototype inverter. Experimental results showed that the proposed controller has very fast dynamic and good steady-state responses even under highly nonlinear loads

Analysis and design of a closed loop controller for bidirectional high-frequency link inverter

This paper presents a closed loop controller for bidirectional high-frequency link inverter. Deadbeat control is adopted to achieve fast dynamic response. The controller consists of inner current loop and outer voltage loop. To improve overall performance of the system, additional decoupling networks are employed. Output voltage decoupling network is included to improve the response of current loop; while load current decoupling network is used to increase the robustness of the inverter towards load variation. Simulation results are presented for the closed loop system under linear and nonlinear loads. It is shown that the control method provides good dynamic response with low total harmonic distortion, even under full-bridge rectifier loads.