DC-link charging arrangement and method for charging a DC-link capacitor
A DC-link charging arrangement is described having a DC-link capacitor, rectifier means, and contactor means arranged between supply voltage ports and the rectifier means and having at least one contactor. Such a charging arrangement should enable charging of a DC-link capacitor in a simple way with low losses. To this end a charging capacitor is arranged bridging the at least one contactor.
1. A DC-link charging arrangement having a DC-link capacitor, rectifier means, and contactor means arranged between supply voltage ports and the rectifier means and having at least one contactor, wherein a charging capacitor is arranged bridging the at least one contactor, wherein the rectifier means is an active rectifier having a plurality of switches which are controlled by control means, the control means being configured to adjust a power angle between a voltage at the supply voltage ports and a charging voltage at active rectifier ports to be close to 90°, wherein the control means are configured to reduce the power angle to zero and voltage amplitude to be the same as grid voltage before the at least one contactor is closed, and wherein an auxiliary power unit is connected to a point between the charging capacitor and a supply voltage port of the supply voltage ports that is connected to the charging capacitor.
2. The DC-link charging arrangement according to claim 1 , wherein a filter arrangement having at least one filter capacitor connected between a phase and a mid-point of at least two phases is arranged between the at least one contactor and the rectifier means.
3. The DC-link charging arrangement according to claim 2 , wherein the charging capacitor has a capacitance value at least 25% of a capacitance value of the at least one filter capacitor.
4. The DC-link charging arrangement according to claim 3 , wherein an additional contactor is arranged in series with the charging capacitor.
5. The DC-link charging arrangement according to claim 2 , wherein an additional contactor is arranged in series with the charging capacitor.
6. The DC-link charging arrangement according to claim 1 , wherein an additional contactor is arranged in series with the charging capacitor.
7. The DC-link charging arrangement according to claim 1 , wherein the charging capacitor is arranged within an LCL filter arrangement.
8. The DC-link charging arrangement according to claim 7 , wherein the charging capacitor is arranged between a filter inductor and at least one filter capacitor.
9. A method for charging a DC-link capacitor connected to rectifier means, the method comprising supplying the rectifier means from supply voltage ports by means of a charging capacitor bridging an open contactor, controlling the rectifier means with control means, the rectifier means being an active rectifier having a plurality of switches, adjusting, by the control means, a power angle between a voltage at the supply voltage ports and a charging voltage at active rectifier ports to be close to 90°, and reducing, by the control means, the power angle to zero and voltage amplitude to be the same as grid voltage before the open contactor is closed, wherein an auxiliary power unit is connected to a point between the charging capacitor and a supply voltage port of the supply voltage ports that is connected to the charging capacitor.
10. The method according to claim 9 , wherein a voltage supplied to the rectifier means is filtered by means of an LCL filter.