Awang Jusoh

The instability effect of constant power loads

The sub-system interaction and instability phenomena is a common problem in the distributed power system (DPS). The interaction arises because each individual converter has internal control function such as to regulate the converter output voltage, which results in the converter tends to draw a constant power and therefore has a negative incremental input impedance. The constant power and negative input resistance characteristic potentially have a de-stabilizing effect on the electrical supply system. The paper presents the analysis, theoretical design and simulation of a simple DC DPS. The analysis of the LC filter and its damping parameters were given. The effect of the negative input resistance of the CPL on the filter was analysed using small-signal input resistance of the load. The passive damping method was used to reduce the system interaction between the converters. The results were verified by MATLAB Simulink simulation.

Trapezoidal PWM Scheme for Cascaded Multilevel Inverter

This paper proposes a new PWM switching strategy for the cascaded multilevel inverter (CMI). This scheme employs multiple trapezoidal modulation waveforms with a single triangular carrier. The main advantage of this technique is the ability to generate PWM waveform generation in real time using very simple algorithm. Furthermore it also results in higher fundamental component magnitude. Although it is known that trapezoidal modulation suffers from the presence of low-order harmonics, it can be minimized by appropriately selecting the slope angle of the trapezoidal, alpha. This paper carried out the simulation on a five level CMI to justify the merits of the proposed scheme. A low cost FPGA based single phase five-level CMI test-rig is also constructed to verify the simulation results.

A Single-Phase Hybrid Active Power Filter using Extension p-q Theorem for Photovoltaic Application

This paper presents a single-phase two-wire hybrid active power filter that is used in conjunction with photovoltaic system. The uniqueness of proposed scheme is the fact that it improves the filtering performance of the conventional active power filter, as well as simultaneously supplies the power from the photovoltaic array to the load and distribution system. The current commands derivation is based on the extension instantaneous-reactive power theorem. The proposed scheme is described in detail. It primarily focuses on the power circuit, the compensation current reference derivation, and the passive high-pass filter design. Experimental results obtained from a laboratory system that verifies the viability and effectiveness of the proposed scheme are presented

A New Hybrid Multilevel Inverter Topology with Harmonics profile improvement

A new hybrid multilevel inverter topology with harmonics profile improvement is presented in this paper. From the literature, it is agreed that hybrid multilevel inverter with its DC sources configured in trinary fashion presents the largest output levels and the lowest total harmonics distortion (THD) percentage. However the output contains low order harmonics due to the impossibility of modulating all adjacent voltage levels at high frequency. With this proposed topology, all adjacent voltage levels are possible to be modulated at high frequency. As a result, the output voltage waveform presents better harmonics profile. The proposed topology and its modulation scheme are presented and verified with simulation results

Performance study of series resonant converter using zero voltage switching

This paper describes the analysis and performance of the series resonant DC-DC converter using soft switching technique, which is a promising and convincing solution method for switched mode electronic power converter. The operating modes classifications are mentioned in this work. The converter behavior above the resonant frequency is also explained in detail. The validity of the analyzed converter parameters had been simulated and tested using MATLAB-SIMULINK software. It was found that the structure of the Series resonant converter circuit does not require complex control either to obtain the zero voltage switching (ZVS) or investigate the conduction modes.

Passive damping network for a Single Phase Matrix Converter (SPMC) operating as a rectifier

This paper presents the application of Single Phase Matrix Converter (SPMC) as an AC-DC controlled rectifier. SPMC used the multiple PWM technique as its basic switching operation for synthesizing the required output. Apart from converting AC input to DC output signal, the investigation also focused on the introduction of passive damping network at DC side to improve the total harmonic distortion (THD). Classical rectifier with LC filter at DC side of the rectifier will create non sinusoidal input current. As a result, it contributes to high THD supply current. Passive Damping Network at DC side was introduced to compensate this problem. The work will be started with some analysis on the relationship between the output and input voltages and the output impedance of filter system in designing the passive damping network using Matlab. A detail investigation on the rectifier performances related to input current THD was carried out using the Matlab/Simulink.

Improvement in ozone generation with low voltage high frequency power converters

This paper proposes a low voltage, high frequency power converters to produce ozone gas in atmospheric pressure. The ozone chamber is made of a dielectric barrier discharge (DBD) chamber using perforated electrodes sheet and insulation material which has lower dielectric breakdown. The power converter is an isolated high frequency inverter with resonance at the secondary of the transformer. This converter is expected to generate ozone gas with lower voltage and power consumption.

Simulation and experimental results of the bi-directional DC-DC converter operating as an active damping device in a simple system

This paper discusses the simulation and experimental results of the bi-directional DC-DC converter operating as an active damping device in a system, which comprises a DC source, L-C filter and constant power load (CPL). The analysis, control design and system simulation are presented. Frequency response measurements are shown to confirm the current controller design. The overall system performance as the input voltage imposed on the system is presented in both simulation and experimental results

AC-DC Single Phase Matrix Converter with a constant power load (CPL)

This paper presents a Single Phase Matrix Converter (SPMC) operated as an AC-DC controlled rectifier driving the non-linear load (constant power load). SPMC used the multiple PWM technique as its basic switching operation for synthesizing the required output. Modeling and analysis of CPL and passive damping network were conducted before implementing in the SPMC system. The usage of LC filter at the DC side of the rectifier to generate smooth DC output creates non sinusoidal input current containing a lot of harmonics. Passive damping network at the DC side was introduced to compensate this problem, however the system performances becomes worse when constant power load was connected. The combination of modified input LC filter at the input side with the passive damping network at the DC side reduced the harmonics content and the output voltage was almost DC. SPMC works well with this arrangement. A complete set of simulation results using MATLAB/Simulink to validate the analysis and design approach of SPMC were given.

Bidirectional high-frequency link inverter with regenerative snubber and deadbeat control

This article presents a bidirectional high frequency transformer link inverter with reduced power switches. On the secondary side of the transformer, two switches are used for rectification and four switches are used for the unfolding stage. The latter are switched at low frequency (50 Hz). Furthermore, a regenerative snubber is incorporated to reduce the voltage surge due to the leakage inductance of the transformers secondary. The proposed inverter is controlled by a deadbeat controller, which consists of the inner current loop, outer voltage loop and a feed forward controller. Additional disturbance decoupling networks are employed to improve the system robustness towards load variations. A 1-kVA prototype inverter is constructed and the deadbeat control algorithm is experimentally verified. The experimental results show that the inverter has high efficiency (86–94%) with low steady-state output voltage total harmonics distortion (1.5%).