Zhaoyang Yan

A New Method of High Frequency Link Matrix Inverter in Parallel

Parallel inverter technology is the basis for distributed power generation system to achieve high reliability, high redundancy, high capacity and high scalability, at the same time, it is also the key to the stable operation of distributed generation system. Traditional inverter technology requires low frequency transformer to achieve electrical isolation and voltage matching, which results in the disadvantages of large volume and weight, low efficiency, dynamic response characteristics and big audio noise. In order to solve this problem, the parallel connection of three-phase high frequency link matrix inverter is studied in this paper. By using the high frequency transformer, the volume of the parallel system is reduced, the noise of the system is reduced, and the efficiency of the parallel system is improved. According to the filtering problem of traditional power inverter, this paper proposes an improved power filtering method. The second order generalized integrator(SOGI) is applied in this paper, after the coordinate transformation, the sampling voltage and current are filtered by the integrator, and the output power is calculated. As a result, the quality of the power is improved, and the stability of the system is improved.

A New Method of Double Fundamental Frequency Phase-Locked Loop Based on Two Integrators

In order to realize the grid connected converter to connect to the grid in unbalanced and distorted grid conditions, in this paper, based on the Sinusoidal Amplitude Integrators (Sinusoidal Amplitude Integrator, SAI), and combined with the cascaded integrators (Second Order Generalized Integrator, SOGI), a new type of double fundamental frequency PLL method is proposed. The method uses the excellent filter performance of cascaded SOGI and frequency characteristics of SAI, and under the negative rotation coordinate system, the 2 times harmonic components generated by the unbalanced grid are separated, extracted and successfully locked in. Solving the problem of the double fundamental frequency fluctuation, when the PLL method of synchronous rotating coordinate system(synchronous rotating fram-PLL, SRF-PLL) is applied on the dq axis under the unbalanced power grid. This paper introduces the basic principle of the cascaded SOGI and SAI, and the mathematical deduction is carried out. Under unbalanced and distorted conditions of the power system, the simulation results are compared with the SRF-PLL method. The results show that the proposed method is feasible, and compared with the traditional PLL method, and the method can detect and extract the synchronization signals more quickly and accurately.

A Novel SVM Control Strategy for a Single-Phase High Frequency Link Matrix Rectifier

The single-phase isolated high power factor PWM rectifier is studied as the research object. A novel space vector pulse width modulation (SVPWM) strategy is proposed pointing to the topology character of the single-phase high frequency link matrix rectifier (HFLMR). The SVPWM working principle is described, the specific working states are analyzed and the experiments based on DSP2812 are done. All of them results uniformly show that the novel SVPWM strategy for the single-phase HFLMR is feasible and effective.

A BLDCM Driver Based on High Frequency Link Matrix Converter

High-frequency link technology has the advantages of high power density, high reliability and electrical isolation. With the development of modern power electronic technology, highlighting its potential advantages, the development of new energy electric vehicle technology is also expanding its application field. A kind of brushless DC motor (BLDCM) driver for electric vehicle containing high frequency link, that is, high frequency link matrix converter is studied. Aiming at the character of bidirectional switch in the matrix converter, a new modulation strategy is proposed, namely decoupling modulation approach that based on square wave is suitable for BLDCM a three-phase six-state 120° turn-on mode, and the corresponding waveform logic synthesis is shown. Whats more, a thoroughly analysis of the high frequency link converter of BLDCM working modes in the new modulation strategy is given. System simulation and experimental results demonstrate the validity of the novel strategy and the feasibility of high-frequency link matrix converter with a BLDCM.

AC-DC Matrix Converter with Positive and Negative Output Capacity in Unbalanced Grid

The study of AC-DC matrix converter under unbalanced power grid is mostly focused on the suppression of the two harmonic of output voltage. In this paper, the voltage type AC-DC matrix converter under unbalanced power network is studied, focusing on the control of the three-phase current in the grid side and the predictive unbalance control strategy with negative sequence voltage compensation is proposed. The strategy can suppress the current harmonics of the grid side, realize the unit power factor and the effect of grid side current sine and high balance under unbalanced power grid, and eliminate the grid side current distortion, in order to reduce the pollution to the power grid. In this strategy, new voltage feedforward quantity is get by the negative sequence voltage compensation and the number of regulators in the current loop in the dq frame is reduced, so that the controller parameter design is greatly simplified. And a de-re-couple SVM modulation strategy with voltage command signal basing on the positive and negative switching is proposed, so that it can meet the requirements of the AC-DC matrix converter with positive and negative output capacity under unbalanced network.

An LLC Resonant AC-DC Converter with PFC Function Based on a Double Inductor Structure

The traditional AC-DC power switching supplies often use the diode rectifier, due to the presence of the large filter capacitor and the switching devices, the power factor of the circuit is usually low, and the harmonic pollution in the grid side is serious. To solve the problem, a method that cascades a PFC (power factor correction) circuit is generally used, however, this increases the circuit stages, which not only reduces the circuit efficiency, but also causes the circuit structure and the control strategy more complex. In this paper, we study a kind of LLC resonant AC-DC converter circuit with PFC function based on a double inductor structure circuit, which can realize the single-stage power conversion and improve the power transmission efficiency. The characteristics of the circuit can achieve the conventional LLC resonant conversion, which ensures the switching devices working in soft-switching mode. And the double inductor structure PFC circuit, using interleaving methods, can better overcome the harmonic distortion problem in the input current in the traditional single-stage PFC AC-DC circuit. In this paper, the theoretical analysis and simulation of the circuit topology are given out, and the experimental results verify the correctness of the theoretical analysis, it also proves that the circuit can both have a good PFC and a AC-DC transform function.

A New PI Algorithm for Single Stage Three-Phase Grid-Connected Photovoltaic Inverter Based on Power Feed-Forward

The single-stage photovoltaic grid-connected system uses only once energy conversion to complete two functions: Maximum power point tracking (MPPT)and grid connected, so it has a large advantage of cost and efficiency. This paper research the Single Stage Three-phase Grid-connected Photovoltaic Inverter. Against the slow response of the DC bus voltage for the control of the traditional double-loop, being not conducive to the quick search of MPPT, this article makes the power feed forward algorithm be applied to the outer ring of the system control, and comparison with the traditional double-loop PI control. In addition, Against the unreasonable of the regulator design and the issues of the Parameters trial, PI regulator parameter design for in-depth research, Through detailed theoretical derivation, we come up with a new design PI regulator approach. The experiment verificates the new design method of PI parameters and the effectiveness of power feed forward control algorithm.

Double Fundamental Frequency PLL Based on Dual Bandpass Filter Structure

In order to solve the problem of synchronization between grid inverter and grid voltage, and improve the detection speed and the precision for the positive-sequence component. Based on dual band pass filter structure, this paper puts forward a new type called double fundamental frequency phase locked loop (DFF-PLL) to measure the double fundamental frequency of positive-sequence component, this method can achieve fast and effectively synchronous with power grid. The principle of DFF-PLL is introduced in detail in this paper. Using a band pass filter eliminates the DC bias and harmonics of input voltage. The performance of DFF-PLL is verified by using simulation and experimental results. Compared with traditional PLL, this method improves the detection speed and accuracy under unbalanced grid voltages.

Study of Effective Vector Synthesis Sequence for Three-Phase Current Rectifier

In order to improve the efficiency and reliability of the phase conversion process of three-phase current source rectifier (CSR), in this paper, the traditional space vector pulse width modulation (SVPWM) strategy of the six sectors for three-phase CSR is changed into a novel SVPWM strategy of the twelve sectors. And by changing the synthesis sequence of effective vector, the power tube which is not in the natural commutation state is made to be do it. Moreover, zero-current switching can be achieved, thus switch loss and voltage stress can be decreased. The proposed space vector modulation technology achieves the expected goals. The simulation and selected experimental results are reported in order to validate the effectiveness of the proposed strategy.

Simulation Study of Single-Cycle Inner Loop Control to Single Phase High-Frequency Link Matrix Converter

Application of single-cycle control of the inverter can enhance the inverter DC input immunity. Controlling auxiliary voltage and current outer loop in a single cycle, the load capacity of a single-cycle control can be improved. In this paper, for single-phase voltage-type high frequency link matrix inverter, we study a new multi-loop SPWM control strategy based on single-cycle inner control. Simulation results show its effectiveness in restraining the DC side disturbance and carrying load capacity.