37results about How to "Eliminates DC bias" patented technology

The invention discloses a DC bias suppression method for a bidirectional full-bridge DC / DC converter, which belongs to the field of circuit control of a bidirectional full-bridge DC / DC converter. The suppression method includes: calculating the required phase shift angle after power change , in the first cycle after the required power change, quantitatively change the phase shift angle and duty cycle of the secondary side, and start to work with a steady-state phase shift angle in the second cycle after the required power change . The invention controls the voltage of the AC side of the secondary side in one cycle so that the current flowing through the transformer can quickly recover to the steady current after the power change, and eliminates the DC bias in the recovery process, thereby suppressing the bias magnetism. The application of bridge DC / DC converter circuit in the occasion of power change is of great significance.

The invention provides an impedance identification method of a power grid of a grid-connected inverter based on high-frequency signal injection. The method comprises the following steps: firstly, respectively measuring the voltage and bridge arm side current of the grid-connected inverter by using a voltage sensor and a current sensor, and converting the voltage and the bridge arm side current through a proportional integral controller to obtain a modulated voltage signal; then, injecting a three-phase high-frequency voltage signal into the modulated voltage signal to update the voltage of thegrid-connected inverter, measuring the power grid side current of the grid-connected inverter by using the current sensor, and respectively substituting the updated voltage and the power grid side current into a voltage extraction module and a current extraction module; and finally, extracting a high-frequency voltage signal and a high-frequency current signal of a grid of the grid-connected inverter by using an improved complex number filter so as to solve an impedance value of the power grid in real time. According to the impedance identification method provided by the invention, the three-phase high-frequency voltage signal is directly superimposed on the modulated voltage signal, thereby ensuring the effective injection of the high-frequency signal and being able to improve the signal-to-noise ratio of the power grid, so that the impedance identification accuracy of the power grid is improved.

The present invention provides a novel general-purpose four-phase-shift modulation method for improving the dynamic performance of dual active bridges. All carrier signals remain synchronized. The general-purpose four-phase-shift modulation method adjusts the corresponding parameters by changing the parameters of the comparison registers in each carrier. phase shift angle. The control method proposed by the present invention is based on the traditional phase-shift control method, and only needs to measure the input and output voltages without adding auxiliary circuits. Compared with other control methods, the method proposed by the present invention completes the dynamic response instantaneously, does not need a transition process, and does not need to detect the inductance current, and the whole control process has nothing to do with the inductance value. The method proposed in the present invention reduces the cost and computational complexity, realizes fast dynamic response of the circuit and eliminates the DC bias of the inductor current during the response process, and at the same time, the method proposed in the present invention can be applied to hard switching, soft switching, unidirectional power transmission, All application scenarios such as two-way power transmission are also applicable to all control methods such as single phase-shift modulation and triple phase-shift modulation.

The invention relates to an alternating current-direct current-alternating current power supply system with transformer power supply for a locomotive or a motor car, in particular to a transformer direct current bias suppression method for the alternating current-direct current-alternating current power supply system of the locomotive. The problems existing in an existing alternating current-direct current-alternating current power supply system of the locomotive in overcoming the transformer direct current bias are solved. When transformer direct current bias suppression method for the alternating current-direct current-alternating current power supply system of the locomotive works through four quadrants, positive accumulation processing and negative accumulation processing of a plurality of power grid cycles are carried out on the input voltage of the four quadrants in the positive and negative half cycle of the power grid voltage. According to the actual working conditions, after the positive and negative half cycle phase intervals of the fundamental wave of the input voltage are accurately calculated, positive accumulation processing and negative accumulation processing of thepower grid cycles are carried out on the input voltage of the four quadrants. Whether direct current bias occurs or not is judged through four quadrant input voltage and current, when the direct current bias occurs, PI regulation is carried out on the accumulated value of the positive and negative half cycle of the current to change the output result of a current loop so as to adjust the PWM pulse width and realize the compensation and suppression of the direct current bias.