A control device of power converters that perform power conversion between two AC systems connected together via a DC line, the power converter operating as a rectifier, and the power converter operating as an inverter, the control device comprising: a constant power control circuit outputting a control angle so as to cause DC power to follow a DC power set value; a VDCOL control circuit having VDCOL characteristics limiting a DC current instruction value based on a DC voltage; a constant current control circuit outputting a control angle so as to cause a DC current at the DC line to follow the DC current set value set based on the VDCOL characteristics; a constant voltage control circuit outputting a control angle so as to cause the DC voltage of the DC line to follow a DC voltage set value; a constant margin angle control circuit outputting a control angle so as to make a margin angle for the power converter constant, and a minimum value selection circuit setting, as the control angle for the power converter, the minimum value of the control angles for the constant current control circuit, the constant voltage control circuit, and the constant margin angle control circuit, wherein: the VDCOL control circuit has different VDCOL characteristics at the rectifier side and the inverter side, respectively; and the each VDCOL characteristic has two break points of high and low for the DC voltage, an upper limit value of the DC current instruction value within a region between the high and low break points is set to be lower at the inverter side than the rectifier side, and the low break points of the respective VDCOL characteristics are consistent, the upper limit value of the DC current instruction value within the region equal to or smaller than the low break point is set to be lower at the inverter side than the rectifier side. a constant power control circuit outputting a control angle so as to cause DC power to follow a DC power set value; a VDCOL control circuit having VDCOL characteristics limiting a DC current instruction value based on a DC voltage; a constant current control circuit outputting a control angle so as to cause a DC current at the DC line to follow the DC current set value set based on the VDCOL characteristics; a constant voltage control circuit outputting a control angle so as to cause the DC voltage of the DC line to follow a DC voltage set value; a constant margin angle control circuit outputting a control angle so as to make a margin angle for the power converter constant, and a minimum value selection circuit setting, as the control angle for the power converter, the minimum value of the control angles for the constant current control circuit, the constant voltage control circuit, and the constant margin angle control circuit, wherein: the VDCOL control circuit has different VDCOL characteristics at the rectifier side and the inverter side, respectively; and the each VDCOL characteristic has two break points of high and low for the DC voltage, an upper limit value of the DC current instruction value within a region between the high and low break points is set to be lower at the inverter side than the rectifier side, and the low break points of the respective VDCOL characteristics are consistent, the upper limit value of the DC current instruction value within the region equal to or smaller than the low break point is set to be lower at the inverter side than the rectifier side. the VDCOL control circuit has different VDCOL characteristics at the rectifier side and the inverter side, respectively; and the each VDCOL characteristic has two break points of high and low for the DC voltage, an upper limit value of the DC current instruction value within a region between the high and low break points is set to be lower at the inverter side than the rectifier side, and the low break points of the respective VDCOL characteristics are consistent, the upper limit value of the DC current instruction value within the region equal to or smaller than the low break point is set to be lower at the inverter side than the rectifier side.