Three-phase diode clamping three-level double-sampling single immediate refreshing method

Abstract

The invention discloses a three-phase diode clamping three-level double-sampling single immediate refreshing method which is applied to a voltage quality adjusting device with a three-phase diode clamping three-level topological structure. The three-phase diode clamping three-level topological structure comprises an incoming and outgoing line circuit breaker, a three-phase full-control inverter / rectifier bridge, a direct current side electrolytic filter capacitor, a rectification side LCL filter circuit, an inversion side LCL filter circuit, a coupling series transformer and an inversion side electronic and mechanical bypass part, the controller DSP generates a modulation wave through operation, generates a pulse width modulation signal after PWM modulation, and outputs the pulse width modulation signal to the inverter side. The pulse width modulation signal is converted through the hardware driving circuit to control the on-off state of the three-phase rectifier / inverter. According to the method, the amplitude of the modulation wave can be updated before the modulation wave and the carrier wave intersect in a switching period, the modulation wave updating delay is eliminated, the robustness of a control system is improved, and the steady-state and dynamic performance of grid-connected current is improved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a three-phase diode-clamped three-level dual-sampling single-immediate refresh method. Background technique [0002] The three-phase diode-clamped three-level grid-connected inverter has the advantages of low device withstand voltage, high efficiency, low output distortion rate, and is suitable for high-power applications. It is used in new energy grid-connected, traction loads and industrial power transmission and distribution fields. widely. With the economic development, a large number of various power terminals are connected, resulting in the increase of parasitic parameters of the power grid system, and the power grid system puts forward higher requirements for the safety, economy and adaptability of grid-connected inverters. The three-phase three-level grid-connected inverter adopts digital control with small delay, but the sampling and calculation delay of the c...

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Problems solved by technology

The three-phase three-level grid-connected inverter adopts digital control with small delay, but the sampling calculation delay of the control loop will change the characteristics of active damping, reduce the robustness of the control system under weak grid, and The phase lag factor is introduced into the grid-connected current loop, which makes the system tracking effect worse

The "sampling time is close to the refresh time" method can effectively reduce the control delay, but the working state of the main power tube of the grid-connected inverter is a hard switching state, and there are high di / dt and dv / dt at the switching time, which is easy The parasitic parameters are coupled to the output signal of the voltage or current sensor to form high-frequency noise, resulting in signal distortion and affecting system stability.

"Multiple refresh times" is similar to "sampling close to the refresh time", and there is also the problem of signal distortion. In addition, there are switching ripples in the "multiple refresh times" method, so that the control system cannot accurately obtain the data in each cycle. Current average value, introducing low-order harmonic components, further reducing system stability

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