A PMU-Based State Estimator For Networks Containing VSC-HVDC links

Wei Li¹, and Luigi Vanfretti¹,²1. KTH Royal Institute of Technology, Sweden

2. Statnett SF, Norwaywei3@kth.se luigiv@kth.se

1

Paper No: 15PESGM0206

Background• PMU-based state estimation (SE) VS. conventional SE

• PMUs provide GPS time-synchronized measurements at a rate of 30-50 samples per second, compared to the rate of two to ten seconds per snapshot for SCADA system;

• A fast state estimator can trace the dynamic behavior of power electronic devices;

• PMU-based SE deals with far less nonlinearities, leading to a much lighter computation burden.

• VSC-based HVDC systems have to be properly modeled for SE.

2

In this paper:• a PMU-based state estimation algorithm is presented; • a comprehensive VSC-HVDC model with vector-current control scheme for SE

purpose is proposed;• to achieve a hybrid AC/DC network SE.

Results3

1 1.5 2 2.5 3 3.5 40.8

0.9

1

Time (s)

|V|(

p.u

.)

Vmag-true

Vmag-meas.

Vmag-est.

1 1.5 2 2.5 3 3.5 410

-5

100

Time (s)

|V|(

p.u

.)

Vmag-estimation-residual

1 1.5 2 2.5 3 3.5 4

0.95

1

1.05

Time (s)

Vrd

c(p

.u.)

Hvdc-true

HvdcmHvdc-est

1 1.5 2 2.5 3 3.5 4

10-5

100

Time (s)

Vrd

c(p

.u.)

Vrdc-residual-error

1 1.5 2 2.5 3 3.5 40.6

0.8

1

Time (s)

Idc

(p.u

.)

Hvdc-true

HvdcmHvdc-est

1 1.5 2 2.5 3 3.5 410

-4

10-2

Time (s)

Idc

(p.u

.)

Idc-residual-error

Conclusions• A PMU-based state estimator for networks containing VSC-HVDC links is

introduced. By applying Kirchhoff’s laws, the proposed network model simplifies the nonlinearities of the conventional network model.

• Network models for a VSC-HVDC station and a point-to-point VSC-HVDC link for the PMU-based SE are developed.

• All the AC and DC states are simultaneously considered to solve nonlinear WLS problem.

• Although estimation accuracy during system dynamic changes decreases compared to that for steady state, it is expected to be greatly improved as long as the network model performs real-time update within each measurement snapshot. Therefore, future work will focus on including network model update or topology processing into the state estimator.

4