Method of setting-up steady state model of VSC-based multi-terminal HVDC transmission system

• US 20060282239A1
• Filed: 06/08/2005
• Published: 12/14/2006
• Est. Priority Date: 06/08/2005
• Status: Abandoned Application

• Current Assignee: Chang GUNG University
• Original Assignee: Chang GUNG University
• Inventors: Tsai, Hung-Chi, Lee, Sheng-Huei, Chu, Chia-Chi
• Application Number:
  US11/148,084
• Publication Number:
  US 20060282239A1
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: Y02E 40/10 Flexible AC transmission systems [FACTS]
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The power flow model of the multiterminal voltage-source converter-based high voltage DC (M-VSC-HVDC) transmission system for large-scale power systems is studied. The mathematical model is derived using the d-q axis decomposition of HVDC'"'"'s control parameter. The developed model can be applied to all existing shunt voltage-source converter (VSC) based controllers, including Static Synchronous Compensator (STATCOM), point-to-point HVDC system, back-to-back HVDC system and multiterminal HVDC system. A unified procedure is developed for incorporating the proposed model into the conventional Newton-Raphson power flow solver. The IEEE 300-bus test system embedded with multiple HVDC transmission systems under different configurations are investigated. Simulation results reveal that the proposed model is effective and accuracy in meeting various control objectives.

Claims

1. A method of setting-up steady state model of VSC-based Multi-terminal HVDC transmission system, which is used to induct M-VSC-HVDC model into Newton-Raphson Power Flow Algorithm through an integration process, which mathematical model can be applied to all controllers composed of parallel voltage source converters (VSC).

5. The model defined in claim 1, wherein if Newton-Raphson iteration method is used to calculate system flow solution, the steady state model of HVDC is expressed as a d-q axis component via Park Conversion using orthogonal projection technology, thus reducing the complexity of computational analysis.

6. The model defined in claim 1, wherein if the system is to calculate power flow solution, a little HVDC control parameters is added to iteration formula;

in despite of the amount of parallel voltage source converters (VSC) and control mode of reactive power compensation, the length of mismatch vector increases only by 1.

J′

=J+Δ

J_HVDC,

Where;

$\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>J_{\mathrm{HVDC}}=\left[\begin{array}{cccccc}0& \frac{\partial <br><br>P_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}{\partial <br><br>V_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}& 0& ❘<br><br>& \frac{\partial <br><br>P_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}{\partial <br><br>I_{\mathrm{sh}<br><br>\text{\hspace{1em}<br><br>}<br><br>1}^D}& 0\\ 0& \frac{\partial <br><br>Q_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}{\partial <br><br>V_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}& 0& ❘<br><br>& 0& 0\\ 0& 0& 0& ❘<br><br>& 0& 0\\ 0& 0& 0& ❘<br><br>& 0& \frac{\partial <br><br>Q_{\mathrm{sk}}}{\partial <br><br>I_{\mathrm{shk}}^Q}\\ -& -& -& +& -& -\\ 0& \frac{\partial <br><br>P_{\mathrm{dc}}}{\partial <br><br>V_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}& 0& ❘<br><br>& \frac{\partial <br><br>P_{\mathrm{dc}}}{\partial <br><br>I_{\mathrm{sh}<br><br>\text{\hspace{1em}<br><br>}<br><br>1}^D}& \frac{\partial <br><br>P_{\mathrm{dc}}}{\partial <br><br>I_{\mathrm{shk}}^Q}\end{array}\right],$

J is corresponding Jacobian matrix, J′

is mismatch vector, and only few elements in Jacobian shall be modified, thus, quadratic convergence of Newton-Raphson algorithm is still maintained, presenting a good convergence characteristic.

2. A steady state model of VSC-based Multi-terminal HVDC transmission system, whereby every HVDC terminal of equivalent circuit can be expressed as a current source;

the said current source includes two orthogonal components;

direct-axis and quadrature- axis component, of which direct-axis component controls the transfer of active power and loss of coupling transformer, and quadrature-axis component has the control capability of reactive power.

3. The model defined in claim 2, wherein the active/reactive power fed to AC power grid from VSC can be foully decoupled through d-q-axis decomposition, thus reducing status variables added into iteration formula and realizing accurately the expected control objectives.

4. The model defined in claim 2, wherein reactive power compensation modes of every terminal are taken into consideration, and integrated successfully into a single solving process.