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 transmissionline 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 ZSVI-MPC 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 PHMMCHVDC 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 powerelectronic 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
REFERENCE:
Jiangchao Qin, Student Member, IEEE, and Maryam Saeedifard, Senior Member,
IEEE, “A Zero-Sequence Voltage Injection-Based Control Strategy for a Parallel
Hybrid Modular Multilevel HVDC Converter System”, IEEE TRANSACTIONS
ON POWER DELIVERY, VOL. 30, NO. 2, APRIL 2015