Stacked Voltage Source Converter (VSC Stacked)

The stacked VSC is implemented as the name suggests by using two VSC, which are connected on the AC side.

See also

Voltage Source Converter (VSC)

The stacked Voltage Source Converter (VSC), is a power electronic device used to convert alternating current (AC) to direct current (DC) and vice versa. It connects an AC system to a dual DC system. Normally it is used to create multi terminal HVDC systems. For example for modelling wind park interconnects with a metallic return line. Currently this construct is not possible, due to a limitation in the underlying pypower modelling approach. Otherwise this model employs two VSC which are connected to a single AC bus. In pandapower the VSC model include a coupling transformer, therefore the input parameter are split to both VSC, so each have: r_ohm/2, x_ohm/2 and r_dc_ohm/2.

See also

Unit Systems and Conventions

Create Function

pandapower.create.create_vsc_stacked(net, bus, bus_dc_plus, bus_dc_minus, r_ohm, x_ohm, r_dc_ohm, pl_dc_mw=0.0, control_mode_ac='vm_pu', control_value_ac=1.0, control_mode_dc='p_mw', control_value_dc=0.0, name=None, controllable=True, in_service=True, index=None, **kwargs)

Creates an VSC converter element - a shunt element with adjustable VSC internal voltage used to connect the AC grid and the DC grid. The element implements several control modes.

Does not work if connected to “PV” bus (gen bus, ext_grid bus)

Parameters:

• net (pandapowerNet) – The pandapower network in which the element is created

• bus (int | integer) – AC connection of the B2B VSC

• bus_dc_plus (int | integer) – connection bus of the plus side of the B2B VSC

• bus_dc_minus (int | integer) – connection bus of the minus side of the B2B VSC

• r_ohm (float) – resistance of the coupling transformer component of B2B VSC

• x_ohm (float) – reactance of the coupling transformer component of B2B VSC

• r_dc_ohm (float) – resistance of the internal dc resistance component of B2B VSC

• pl_dc_mw (float) – no-load losses of the B2B VSC on the DC side for the shunt R representing the no load losses

• control_mode_ac (str) – the control mode of the ac side of the VSC. it could be “vm_pu”, “q_mvar” or “slack”

• control_value_ac (float) – the value of the controlled parameter at the ac bus in “p.u.” or “MVAr”

• control_mode_dc (str) – the control mode of the dc side of the B2B VSC. it could be “vm_pu” or “p_mw”

• control_value_dc (float) – the value of the controlled parameter at the dc bus in “p.u.” or “MW”

• name (str | None) – element name

• controllable (bool) – whether the element is considered as actively controlling or as a fixed voltage source connected via shunt impedance

• in_service (bool) – True for in_service or False for out of service

• index (int | integer | None) – Force a specified ID if it is available. If None, the index one higher than the highest already existing index is selected.

Returns:

The ID of the created ssc

Return type:

int | integer

Input Parameters

net.vsc_stacked

Parameter	Datatype	Value Range	Explanation
name	string		name of the B2B VSC
bus*	integer		index of ac bus of the ac side of the B2B VSC
bus_dc_plus*	integer		index of dc bus of the plus dc side of the B2B VSC
bus_dc_minus*	integer		index of dc bus of the minus dc side of the B2B VSC
r_ohm*	float	\(\geq\) 0	resistance of the coupling transformer
x_ohm*	float	\(\geq\) 0	reactance of the coupling transformer
r_dc_ohm*	float		resistance of the internal dc resistance component of VSC
pl_dc_mw	float		no-load losses of the VSC on the DC side for the shunt R representing the no load losses
control_mode_ac*	string	“vm_pu”, “q_mvar”, “slack”	the control mode of the AC side of the B2B VSC
control_value_ac*	float		the value of the controlled parameter at the ac bus
control_mode_dc*	string	“vm_pu”, “p_mw”,	the control mode of the dc side of the B2B VSC
control_value_dc*	float		the value of the controlled parameter at the dc bus
controllable*	boolean	True / False	whether the element is considered as actively controlling
in_service*	boolean	True / False	specifies if the B2B VSC is in service.

*necessary for executing a power flow calculation.

Electric Model

Image was created with https://www.circuit2tikz.tf.fau.de/designer/. Stacked Voltage Source Converters are self-commutated converters to connect HVAC and HVDC systems using devices suitable for high power electronic applications, such as IGBTs.

Limitations

Since the powerflow equations are modelled that every component is connected to the same ground, topologies employing a lifted or virtual ground are not currently supported. For example, one could attach two stacked VSC on the minus and plus side, and therefore “lift” one of the VSC to create a virtual ground for a metallic return line scenario. But in this case, the first lower VSC will be shorted by second upper VSC. Currently a workaround is employed by creating the topology, but setting the corresponding metallic return line out of service. Then a specialized controller needs to be employed, which calculates the resulting currents and updates the out-of-service line. See test_facts_vsc_stacked.py: test_hvdc_interconnect_with_dmr() for an example.

Result Parameters

net.res_vsc_stacked

Parameter	Datatype	Explanation
p_mw	float	total active power consumption of B2B VSC [MW]
q_mvar	float	total reactive power consumption of B2B VSC [MVAr]
vm_internal_pu	float	voltage magnitude at vsc internal bus [pu]
va_internal_degree	float	voltage angle at vsc internal bus [degree]
vm_pu	float	voltage magnitude at B2B VSC ac bus [pu]
va_degree	float	voltage angle at B2B VSC ac bus [degree]
p_dc_mw_p	float	active power of the plus side of the B2B VSC [MW]
p_dc_mw_m	float	active power of the minus side of B2B VSC [MW]
vm_internal_dc_pu_p	float	voltage angle at the plus B2B VSC ac bus [pu]
vm_internal_dc_pu_m	float	voltage angle at the minus B2B VSC ac bus [pu]
vm_dc_pu_p	float	voltage magnitude at the plus B2B VSC ac bus [pu]
vm_dc_pu_m	float	voltage magnitude at the minus B2B VSC ac bus [pu]