For the two-stage single-phase power factor correction (PFC) converter, its instantaneous input power pulsates at twice the line frequency, generating the second harmonic current (SHC) at the dc-bus port. The dc–dc stage is used to regulate the output voltage or the dc bus voltage in different applications, and the SHC reduction schemes for the dc–dc stage with different control objectives are discussed in this article. When the dc–dc stage regulates the output voltage, it is pointed out that the control bandwidth of the dc–dc stage is required to be high enough and the dc bus capacitor should be large enough to suppress the SHC, and the design of the dc bus capacitor is given. When the dc–dc stage regulates the dc bus voltage, a virtual impedance is added in series with the input/output of the dc–dc stage to suppress the SHC, and a virtual impedance is added in parallel with the dc bus to improve the dynamic performance. The selection and design of the virtual impedances are also given. Based on that, three specific control schemes are proposed for the dc–dc stage to suppress the SHC, and the parameters design method is also presented. Finally, a 3.3-kW two-stage single-phase PFC converter is fabricated and tested in the lab to verify the effectiveness of the proposed SHC reduction schemes. 

Second Harmonic Current Reduction Schemes for DC–DC Converter in Two-Stage PFC Converters

A magnetic linked multiport fractional converter (MLMFC) is proposed in this article for application to doubly fed induction generator-based variable speed wind power generating systems. With the proposed MLMFC topology, no back-to-back converter and heavy step-up line-frequency transformer are needed.Moreover, the proposed MLMFC ensures isolation between the rotor-side and grid-side of the system. An improved current sensorless dual-loop individual voltage balance controller (DIVBC) is proposed at the grid-side for individual dc-link voltage balancing for the MLMFC with an interstage controller decoupling technique. The proposed DIVBC shows improved dc-link voltage tracking and dc-link disturbance rejection capabilities. Moreover, an improved current sensorless dual-loop proportional-integral resonant voltage controller (DPIRVC) is proposed at the rotor-side for the strict regulation of the dc-link voltage, the suppression of the dc-link voltage ripples, and the achievement of low controller sensitivity to the load disturbances. Hence, with the combination of the proposed DIVBC with the DPIRVC, the controller architecture requires a low dc-link capacitance without the need to utilize any dc-link current sensors to feedforward any disturbances to the controller. Moreover, the proposed controller architecture shows high stability and robustness under capacitance mismatches, load disturbances, voltage sag and swell, grid fault, and different wind speeds. The superior performance of the proposed control strategy is demonstrated through simulation and laboratory experiments.

A Magnetic Linked Multiport Fractional Converter for Application to Variable Speed Wind Power Generating Systems

The invention provides a two-way AC (alternating-current)-DC (direct-current)-DC single-phase convertor and a control method thereof and relates to the technical field of power supply of electrified railways with an aim to effectively solve the problem about secondary voltage ripples. Control on the secondary voltage ripples of converter output voltage is realized by designing a controller using the feedback linearization ideology, and the control method includes the steps of 1), performing modeling analysis through the AC-DC-DC single-phase convertor and establishing a large-signal-state space equation; 2), structuring intermediate auxiliary variables; 3), designing a decoupled linearization controller. A two-way DC-DC isolation system high in coupled nonlinear characteristics is decoupled prior to being subjected to linear processing, and finally the novel controller of the two-way AC-DC-DC single-phase convertor is designed under the linearized system condition; the two-way AC-DC-DC single-phase convertor and the control method thereof are mainly used for converting alternating-current voltage into direct-current voltage, and meanwhile, electric isolation is realized.

Two-way AC (alternating-current)-DC (direct-current)-DC single-phase convertor and control method thereof

The invention relates to a control strategy for a super capacitor energy storage system current transformer. The control strategy is characterized by comprising steps of analyzing energy distribution states of a super capacitor energy storage system in different work modes, establishing a system mathematics model, designing a control strategy of a bidirectional DC/DC current transformer and designing a control strategy of a DC/AC voltage source type current transformer, the bidirectional DC/DC current transformer and the DC/AC voltage source type current transformer are taken as power adjusting devices, and power throughput of the super capacitor energy storage system and DC side voltage control are realized. A simulation system is established based on PSCAD/EMTDC software, accurate and rapid response to designated charging and discharging powers can be realized by the super capacitor energy storage system, DC side voltage work is stable, and work efficiency is high.

Control strategy for super capacitor energy storage system current transformer

Harmonics destructively impact the performance and stability of power systems. This paper proposes the development of a stable shunt active power filter (SAPF) for harmonics mitigation. The proper and stable operation of the SAPF control system requires the determination of the current reference, phase angle synchronization, and DC-link voltage regulation. This paper uses an artificial neural network (ANN) and one of its sub-methods, the adaptive linear neuron (ADALINE), to determine the current reference. However, determining the current reference requires providing a stable phase angle, which is a fundamental challenge in distorted grids because harmonics created in the grid cause phase angle synchronization problems, due to malfunction of the conventional phase-locked loop (PLL). These things considered, the weak grid connection imposes an instability issue due to the poor performance of the conventional PLL when the grid impedance is high. In this paper, a robust synchronous filter (RSF) is adopted, which separates the harmonic from the main component to provide harmonics-free signals for the PLL. Using RSF, a robust synchronizer quasi-static filter (RSQSF) PLL model is designed, which is effective in dealing with harmonics in weak-grid conditions. MATLAB Simulink was used to check the validation and effectiveness of the proposed control structure. The results show a reduction in harmonics generated in the grid by 86.7% for nonlinear load with a balanced source, 84% for nonlinear load with an unbalanced source under grid impedance, and 80.46% for the nonlinear load with an unbalanced source under weak-grid conditions.

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Adaptive Neural Network for a Stabilizing Shunt Active Power Filter in Distorted Weak Grids

A single-phase isolated ac–dc–dc converter with low total harmonic distortion and high power factor usually suffers from a significant ripple power at double line frequency. The inherent ripple power brings a significant low-frequency voltage ripple on the dc-link capacitor. To reduce the voltage ripple, bulky electrolytic capacitors and hardware low-pass filter are widely adopted. However, the converter becomes bulky because of large capacitor. In order to reduce the dc-link capacitance, optimal control strategies are proposed for ac–dc and dc–dc converter, respectively, in this article. First, the notch filter with current disturbance feedforward strategy (NF-CDFS) are proposed to minimize input harmonic current of ac–dc converter. Second, the feedback linearization with voltage disturbance feedforward strategy (FLVDFS) is designed to suppress the output voltage ripple of dc–dc converter based on generalized state space averaging model. With the proposed NF-CDFS plus FLVDFS control strategy, low input harmonic current and low output voltage ripple are achieved. In addition, more than about 85% of dc-link capacitance is reduced compared to conventional methods.

Optimal Input and Output Power Quality Control of Single-Phase AC–DC–DC Converter With Significant DC-Link Voltage Ripple

The utility model provides a two -way AC DC single -phase converter of DC relates to electric Railway power supply technical field. It can solve the problem of secondary voltage ripple effectively. Output voltage v2 inserts band pass filter BP, band pass filter BP's output and subtracter sigma's 1 input connection, this subtracter sigma's 1 output and proportion resonance controller PR's input connection, the ware was set for to trapper notch's output and output voltage reference value output (img file='DDA0001111691380000011. TIF'wi='40'he='67' /) respectively with two input connections of subtracter sigma 2, this subtracter sigma's 2 output and pi controller PI's input connection, output current io inserts the proportional controller P that a proportion is 1C2, with the input to adder sigma 3 of proportion resonance controller PR, pi controller PI and proportional controller P's output connection, this adder sigma's 3 output and two -way isolation DC the input voltage v1 of DC converter is connected to divider DIV, last modulator PWM output two -way AC DC single -phase converter of DC's switching element drive signal respectively. Mainly used hands over, direct current voltage conversion.

Two -way AC DC single -phase converter of DC

The invention discloses a multi-isolation-transformer series power supply device. An input power source Vi1 is connected with an input end a1 and an input end b1 and is transformed into a voltage level required by a control module through a transformer T1 to supply power to a power supply module of a control circuit. The output end of the transformer T1 is the input end of a transformer T2. The turns ratio of the transformer T2 to each level of transformer Ti (i=1, 2, 3, 4...) behind is 1:1. In sequence, the input end of each level of transformer is connected with the output end of the front level of transformer, the output end of each level of transformer is connected with the input end of the next level of transformer, and therefore a series transformer set is formed. The positive electrode of a busbar between every two adjacent levels of transformers is connected with the positive electrode end of the power supply module, and the negative electrode of the busbar is connected with the negative electrode of the power supply module, so that power is supplied to the control module. The power supply device is simple in structure, only one power source supplies power to the power supply module, the insulation voltage level of the power supply module and the insulation voltage level of the control module are lowered, the power supply module is isolated from the control module, and the power supply device is long in service life and convenient to use and maintain.

Multi-isolation-transformer series power supply device

The utility model discloses a device for many isolation transformer series power supply, input power vi1 links to each other with input a1, b1, alternaties through transformer T1 to be the required electric pressure of control module, supplies power for control circuit power module, transformer T1's output is transformer T2's input, transformer T2 and each grade transformer ti (i=1, 2, 3, 4 at the back... ) the ratioturn is 1: 1. In order, the transformer input of each grade is all continuous with the output of previous level transformer, and each grade transformer output end is continuous with the input of next stage transformer, constitutes the transformer bank of a series connection. The positive pole of the generating line of adjacent two-stage transformer room links to each other with power module's positive terminal, and the negative pole of generating line is connected with power module's negative pole, supplies power for control module. This kind of device simple structure, the utility model discloses only a power is supplied power for power module, and power module, control module isolation voltage grade reduce, the mutual isolation, and be longe-lived, uses and maintain the convenience.

Yin Xiaodong

Papers

Optimal Input and Output Power Quality Control of Single-Phase AC–DC–DC Converter With Significant DC-Link Voltage Ripple

Two-way AC (alternating-current)-DC (direct-current)-DC single-phase convertor and control method thereof

Two -way AC DC single -phase converter of DC

Multi-isolation-transformer series power supply device

Device for many isolation transformer series power supply