Docstoc

HPFC _Hybrid Power Flow Controller _

Document Sample
HPFC _Hybrid Power Flow Controller _ Powered By Docstoc
					HPFC (Hybrid Power Flow Controller )




Donsión                 Hybrid Power Flow Controller (HPFC) - Topology

                The Hybrid Power Flow Controller (HPFC) uses two equally rated
             voltage-sourced converters to upgrade the functionality of the existing
             switched capacitors or static VAR compensators (SVCs). Since static
             converters are used together with passive devices, the power flow controller
             can be considered hybrid

24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión                 Hybrid Power Flow Controller (HPFC) - Topology

                The HPFC is installed at some point along the transmission line
             connecting two electrical regions characterized by their Thevenin's
             equivalent voltage sources VS and VR. The line is thereby divided into two
             segments represented by the equivalent reactances XS and XR. Indices "S"
             and "R" identify "sending" and "receiving" end/segment of the line.

24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión                 Hybrid Power Flow Controller (HPFC) - Topology

                Central to the HPFC's topology is the shunt connected source of reactive
             power – shown as the variable capacitance, in the Figure. Next, there are
             two voltage–sourced converters (VSCs) connected to the associated line
             segments in series using coupling transformers. The converters share a
             common DC circuit, coupling each other's DC terminals.

24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión                 Hybrid Power Flow Controller (HPFC) - Topology

                By controlling the magnitudes and angles of voltages supplied by the
             converters, the flow of active power through the line and the amounts of
             reactive power supplied to the corresponding line segments can be
             simultaneously and independently controlled. The control of the shunt
             device is coordinated with the control of converters to supply the bulk of
             the total required reactive power.
24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión




             HPFC – Equivalent circuit and operating constraints

24/08/2007
HPFC (Hybrid Power Flow Controller )

                The variable capacitance, labelled BM, represents the controllable shunt
             connected variable susceptance. The range of values this parameter can
             assume depends on the installed power components; in general case it can be
             positive (capacitive), zero, or negative (inductive).

                Voltage sources VX and VY represent the high voltage equivalents of
             voltages generated by the VSCs. The common DC circuit of the VSCs is
             represented by the capacitor CDC, and this capacitor is charged or discharged
             based on the difference of active powers coupled by the converters.

                First, converters' voltage ratings impose magnitude limits on VX and VY.
Donsión      Additionally, magnitudes of IS and IR are limited, as these currents flow
             through the converters' switches. Then, line insulation requires that
             magnitudes of voltages V1 and V2 are limited, and voltage ratings of the shunt
             susceptance require limited magnitude of VM. And finally, in order to operate
             the converters, we require that VDC is maintained at a steady value, so in
             steady state PX has to be equal PY.
               This new FACT equipment is only a proposal by J. Bebic, "A Symmetrical Hybrid Power
               Flow Controller", Ph.D. Thesis, University of Toronto, 2003.

24/08/2007
HPFC (Hybrid Power Flow Controller )




 Donsión




             HPFC – Transformation of condition of converters'
                            power balance


24/08/2007
HPFC (Hybrid Power Flow Controller )




                                        Constant power line
Donsión
                It is advantageous to provide a geometric interpretation for the condition
             of converters' power balance. Power is proportional to scalar product of
             voltage and current. Hence, for a given vector VS, sending end power PS is
             proportional to the projection of IS onto VS. Therefore, as depicted in the
             Figure. Current vectors IS1 and IS2 transfer the same sending end power, as
             would any other current vector that has its tip on the same line perpendicular
             to VS. This line may be considered a "constant power line".
24/08/2007
HPFC (Hybrid Power Flow Controller )




                           a)                                      b)




Donsión




                           c)                                       d)
             A procedure for solving steady state operating points based on specified
                                      PR(=PS), QS, and QR
24/08/2007
HPFC (Hybrid Power Flow Controller )


                Voltage vectors VS and VR, and equal power lines corresponding
             to the desired power flow PR(=PS) are shown in Figure (a). Current
             vectors IS and IR are chosen so that their tips lie on these equal
             power lines. There is hence one degree of freedom in choosing the
             location for each vector. This degree of freedom can be viewed as
             freedom to select the amount of reactive power supplied from the
             corresponding line end. Specifying QS selects a unique IS, and
             specifying QR selects a unique IR.

               Voltages V1 and V2 are obtained by subtracting and adding
Donsión      voltage drops across the respective line segments, as shown in
             Figure (b).

               Next, IM and VM are obtained as shown in Figure (c).

               Finally, VX and VY are found as shown in Figure (d).



24/08/2007
HPFC (Hybrid Power Flow Controller )




                         HPFC used to reduce the power flow on a line
Donsión


                 Let us first discuss the operating point that we just found – we repeated
             it in the Figure. It corresponds to the power flow lower than the "naturally
             occurring" power flow. Notice that V1 and V2 are positioned in such way as
             to reduce the angular difference between the voltages VS and VR.



24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión      Maintaining the same line operating point using step changed value of BM

                   The diagram in Figure demonstrates a possibility to maintain the same
               line currents for a step changed value of BM. Now, if IS and IR are to be
               maintained at the same value, IM has to remain the same; hence VM must
               be increased. The Figure demonstrates that this can be accomplished by
               reconfiguring the converters' voltages.

24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión
                                    Decoupled control of QR

                The Figure demonstrates the decoupled control of reactive power
             supplied to the receiving end of the line. Converters' voltages are now
             configured so as to move IR along its constant power line and reduce the
             value of QR.


24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión

                                    Increased power flow

                Increased power flow is shown in the Figure. Notice that V1 is now
             "below" and V2 "above" VM – resulting in the increased combined angle. As
             expected, the magnitudes of IS and IR are increased.

24/08/2007
HPFC (Hybrid Power Flow Controller )




Donsión                          Power flow reversal


                Finally, we show the reversal of power flow in the Figure. Relative
             position of VM and IM indicates that BM is inductive in this case.




24/08/2007
HPFC (Hybrid Power Flow Controller )


                The steady state operating points presented by these vector
             diagrams show that the Hybrid Power Flow Controller has the
             qualitative characteristics of a UPFC.
                Specifically, it can control the flow of active power through the
             transmission line and supply the prescribed amounts of reactive
             power to sending and receiving segments of the line.
               But, while the UPFC uses a shunt connected converter, the
             HPFC needs only a shunt connected capacitor – a considerable
Donsión
             advantage considering the converter costs.




24/08/2007
HPFC (Hybrid Power Flow Controller )
                                                       The P–δ curves of the HPFC
                                                    and the P–δ curves of the UPFC
                                                    are compared in the Figure
                                                    Curves 1 and 2 correspond to
                                                    the line controlled by the HPFC
                                                    to maximize and minimize the
                                                    power flow, respectively; Curve
                                                    3 corresponds to the line
                                                    compensated by the underlying
                                                    SVC; Curve 4 corresponds to
                                                    the power flow on the
                                                    uncompensated line; Curves 5
Donsión                                             and 6 correspond to the line
                                                    controlled by the UPFC to
                                                    maximize and minimize the
                                                    power flow, respectively; and
                                                    curve 7 corresponds to the
                                                    power flow on the line
             Comparison of P–&delta curves – HPFC   compensated by the underlying
                           vs. UPFC                 STATCOM.
24/08/2007

				
DOCUMENT INFO
Shared By:
Tags: Hybrid, Power
Stats:
views:22
posted:11/12/2011
language:English
pages:17
Description: Hybrid Power technology is actually configured by the integrated chipset graphics card to support the technology in the drive and the operating system under the control of the time when the system load using only integrated graphics chip to reduce power consumption, and when full time work load by the integrated graphics with discrete graphics cards to further enhance the efficiency of this technique one can reduce system power consumption, especially those who can benefit from a system with discrete graphics, but can also enhance the system to some extent integrated graphics performance.