Download A Zero-Sequence Voltage Injection-Based Control

A Zero-Sequence Voltage Injection-Based Control
Strategy for a Parallel Hybrid Modular Multilevel
HVDC Converter System
ABSTRACT
This paper proposes a zero-sequence voltage injection (ZSVI)-based model predictive
control (MPC) strategy to control the dc current/power flow and simultaneously minimize the dc
current ripple. The proposed strategy takes advantage of a cost function minimization technique
to determine and inject the optimal zero-sequence voltage components into the dc- bus voltage of
a PHMMC system. This paper derives a discrete-time dynamic model of the dc transmission-line
current and, correspondingly, develops a predictive model. The predictive model is used to inject
the appropriate amount of zero-sequence voltage components to the dc bus reference voltage
waveform. Compared with the existing triplen harmonics injection method, the proposed ZSVIMPC strategy improves the performance of a PHMMC system in terms of minimization of the dc
current/voltage ripple.
CIRCUIT DIAGRAM
Existing System
One of the main technical challenges associated with the control of a PHMMC-HVDC system is
to simultaneously control the dc current/power flow and the real and reactive power. The
existing method proposed to resolve this issue is based on third harmonic component injection
where a third harmonic component is introduced to the reference phase voltages. Although this
method controls the dc bus voltage, it cannot eliminate the magnitude of the sixth-order
harmonic component in the dc current. Further reduction of the dc current/voltage ripple
necessitates injection of higher order harmonics to the dc bus voltage, which will add to the
complexity in control.
Proposed System:
In this project, a zero-sequence voltage injection (ZSVI)-based model predictive control
(MPC) strategy is proposed to simultaneously regulate the dc current/power flow and reduce the
dc current/voltage ripple of a PHMMC-HVDC system. The MPC strategy is a promising control
strategy applied to power-electronic converter systems due to its fast dynamic response,
flexibility to include constraints and nonlinearities of the system, and ease in digital
implementation.
This project takes the advantages of the features of the MPC strategy and develops a
discrete-time predictive model of the dc current of a PHMMCHVDC station. Based on the
developed model, an MPC strategy is proposed to: 1) control the dc current/power flow through
the dc transmission lines by regulating the dc bus voltage and 2) minimize the dc current/voltage
ripple. The capability of the overall controller with the proposed MPC strategy in terms of dc
current/power flow control and real/reactive power control for a 21-level PHMMC-HVDC
station is presented.
TOOLS AND SOFTWARE USED:
 MP LAB
 ORCAD/PSPICE
 MATLAB/SIMULINK
OUTPUT:
 HARDWARE
 SIMULATION