Design a H-bridge low ripple and high bandwidth air core magnet corrector power supply in NSRRC

This paper is the study of a low-current-ripple and high-bandwidth corrector power supply. The main circuit of this power supply is using a full bridge (H-bridge) structure, and the output current through the high-precision direct current current transducers (DCCT) to transfer the reference voltage to the controller. Previous TPS corrector power supply had a 4.7 kHz current bandwidth, and its output current ripple was 100 μA. Such current ripple and bandwidth do not satisfy the requirements of a rapidly orbiting feedback system of air core loading. Therefore, our research team designed a novel prototype power supply with a high bandwidth (more than 10 kHz) and low output current ripple (less than 10 μA) which was developed via a novel topology circuit. The operation frequency of the main power switch's n-type metal-oxide-semiconductor logic of this novel circuit is increased to 245 kHz. Moreover, the output results of the filter inductor and filter capacitor are modified to 80 μH and 2.46 μF, respectively. The prototype power supply bandwidth reached 10.546 kHz and increase of 124% and its output current ripple was lowered below than 5 μA. The properties of this corrector power supply are very important for the beam correction in storage rings. Finally, A circuit with an input voltage of 48 V, a maximum output current of 10 A, and an output power of 400 W is tested in a laboratory to verify the performance of the developed corrector for the National Synchrotron Radiation Research Center.

New bidirectional step-up DC-DC converter derived from buck- boost DC-DC converter

<span lang="EN-US">This paper proposes a new bidirectional step-up DC-DC converter, namely modified buck-boost DC-DC converter. The proposed DC-DC converter was derived from the conventional buck-boost DC-DC converter. Output voltage expression of the proposed converter was derived by considering the voltage drops across inductors and switching devices. The results have shown that with the same parameter of input LC filter, proposed DC-DC converter has lower conduction losses. Moreover, the proposed DC-DC converter has lower rated voltage of filter capacitor than the conventional boost DC-DC converter which lead to cost efficiency. Finally, a scaled-down prototype of laboratory experiment was used to verify its theoretical analysis.</span>

Study of the operation of the output filter of a single-phase series active power filter

In the article is presented a single-phase series active power filter (SFSAPF) designed to compensate the total harmonic distortion (THD) factor of the supply network voltage. Particular attention is paid to the work of the output capacitor of the passive filter, and dependencies for the design of the filter at hysteresis voltage control are presented. The value of the higher harmonics of the current through the filter capacitor is determined. A mathematical relationship between the voltage ripple of the capacitor, its value and the switching frequency is derived. As a result of the advanced research a methodology for designing the output filter of a single-phase serial active power filter has been proposed. The results from computer simulation and experiment are also given.

A method for calculating the parameters of the sine filter of the frequency converter, taking into account the criterion of starting current limitation and pulse-width modulation frequency

An analysis of the method for ensuring the sinusoidality of the output voltage in power generation systems with self-commutated voltage inverters under the requirements of the international standard IEEE-519 is presented. In a number of programs, especially low-power generation systems, a low-cost solution is needed to provide the sinusoidal waveform of the output voltage with the total harmonic distortion of 5 %. This solution is to use two-level voltage inverters with an output sine LC filter. However, the feature of the sine filter with the frequency converter is that the PWM frequency affects the spectrum of higher harmonics of the output voltage. In addition, there is the starting current of the filter capacitor, which can disable the power switches of the voltage inverter. The developed method for calculating the values of the LC filter with the two-level voltage inverter in the PWM mode is presented meeting the requirements of the international standard IEEE-519, taking into account the modulation frequency and limitation of the starting current of the filter capacitor. To confirm the required quality of the output voltage of the two-level voltage inverter with the sine filter, an appropriate simulation model was created in the Matlab/Simulink computer simulation environment. The oscillograms and harmonic analysis of the input and output voltages of the sine filter, which showed the total harmonic distortion of 1.88 %, are presented. A physical prototype of the investigated system was created on the basis of a 5.5 kW OVEN PChV203-5K5-V frequency converter (Ukraine). Using the SIGLENT SDS1104X-E oscilloscope (China), the real waveform and the results of the harmonic analysis of the sine filter output voltage, confirming the implementation of the necessary sinusoidality criteria, were obtained

Control scheme based on capacitor voltage second-order complex-vector feedforward for LCL-filtered inverter

For an inverter with LCL filter, voltage at the point of common coupling (PCC) is equivalent to the filter capacitor voltage in practical applications. However, the PCC voltage background harmonics will cause the distortion of grid current. Some problems exist in the traditional methods for harmonics suppression, such as insufficient phase margin, increasing design complexity and computation burden. Thus, a scheme of second-order complex-vector feedforward (SOCVF) of capacitor voltage is proposed in this article. First, based on the vectorial principle, the active unit vectors of capacitor voltage were calculated. Then, its fundamental component was obtained by the SOCVF-function. Furthermore, the references of the grid current were obtained with the instantaneous power theory. Hence, the proposed scheme helps effectively dampen the LCL resonance to make the system stable, and works well at suppressing the injected grid current distortion simultaneously. Simulation and experimental results validated the effectiveness of the proposed scheme.