An improved bidirectional DC transformer connected with switched capacitors and its control method
A bidirectional DC, switched capacitor technology, applied in the direction of converting DC power input to DC power output, adjusting electrical variables, control/regulating systems, etc., can solve the problem of reducing the modularity of conversion units, reducing efficiency and power density, and increasing switching costs. and other problems, to achieve the effect of reducing loss, reducing circulating current, and improving power density
Active Publication Date: 2018-04-10
TSINGHUA UNIV
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Problems solved by technology
However, the addition of three semiconductor switches increases the cost of the switch by 37.5%, and the semiconductor switches S1 and S2 flow a current equivalent to the load current, resulting in increased loss, which reduces efficiency and power density to a certain extent
In addition, two and one semiconductor switches are added to the full bridge on the high and low voltage sides respectively, which reduces the modularity of the conversion unit to a certain extent.
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[0037] In the system embodiment of the present invention, the high-voltage DC side of the bidirectional DC transformer is connected to a 10kV DC voltage, and the low-voltage DC side is connected to a 400V DC voltage; each bidirectional DC transformer is composed of 15 identical DC converter units, that is, n=15; A maximum of 3 bypasses can be allowed, that is, k=3; then the rated voltage of the high-voltage side in the DC conversion unit is 10kV / 12=830V, and the rated voltage of the low-voltage side is 400V, and the DC auxiliary inductance L1 in each DC converter unit can be set as 2mH, the switching frequency of semiconductor switches S1-S8 is 20kHz, the high-frequency inductor L is 0.1mH, the transformation ratio of high-frequency transformer T is 830V:400V, and the two DC capacitors C1 and C2 are both 3300uF, then:
[0038] (1) Under normal circumstances, the second auxiliary semiconductor switches Q2 of all the DC conversion units are in the conduction state, and the contro...
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The invention discloses an improved bidirectional DC transformer connected with switched capacitors and a control method thereof, belonging to the technical field of electric power; the transformer is composed of n completely identical DC conversion units connected in series at one port and in parallel at the other port; each The DC conversion units are composed of eight semiconductor switches, two auxiliary semiconductor switches, two DC capacitors, a high-frequency inductor and a high-frequency transformer; the method includes that under normal circumstances, after the high-voltage sides of n DC conversion units are connected in series, Connect to the high-voltage DC side through a DC reactance, and connect the low-voltage side directly to the low-voltage DC side after being connected in parallel. When an internal failure of less than k DC conversion units occurs, the faulty DC conversion unit can be directly bypassed; when a high-voltage or low-voltage DC When an external fault occurs on the side, the semiconductor switches and auxiliary semiconductor switches of all DC conversion units are turned off to keep the capacitor voltage unchanged. The invention improves the economy and reliability of device operation.
Description
technical field [0001] The invention belongs to the technical field of electric power and relates to a solid-state transformer, in particular to an improved double-active full-bridge high-frequency link bidirectional DC transformer. Background technique [0002] With the development of power electronic control technology and device manufacturing technology, flexible DC transmission based on fully controlled voltage source converter (VSC) has achieved rapid development. Compared with the traditional DC transmission technology, flexible DC transmission does not have the problem of commutation failure, and can be applied to supply power to passive loads; using pulse width modulation (PWM) technology, the harmonic content of voltage and current is less, and the filtering link can be omitted. It makes the footprint smaller; the control is flexible, and the independent decoupling control of active power and reactive power can be quickly realized, and the fast reversal regulation o...
Claims
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IPC IPC(8): H02M3/335
CPCH02M3/33584H02M1/0074H02M1/0077H02M1/325
Inventor 赵彪李建国宋强刘文华刘文辉
Owner TSINGHUA UNIV