Transient convergence problem

I am simulating a buck-boost converter of 1 V input and low power (50uW) with 100kHz switching frequency.

The transient is not converging. Following is the log file:

************************************************
Transient Analysis `tran': time = (0 s -> 20 ms)
************************************************

Opening the PSFXL file ../psf/tran.tran.tran ...
Important parameter values:
start = 0 s
outputstart = 0 s
stop = 20 ms
step = 20 us
maxstep = 200 us
ic = all
useprevic = no
skipdc = no
reltol = 1e-06
abstol(V) = 10 nV
abstol(I) = 10 fA
temp = 27 C
tnom = 27 C
tempeffects = all
errpreset = conservative
method = gear2only
lteratio = 10
relref = alllocal
cmin = 0 F
gmin = 1 pS

Output and IC/nodeset summary:
save 7 (current)
save 11 (voltage)

Notice from spectre at time = 345 us during transient analysis `tran'.
Newton iteration fails to converge at time = 345 us step = 20.0035 as.
Disaster recovery algorithm is enabled to search for a converged solution.
Notice from spectre at time = 355 us during transient analysis `tran'.
Newton iteration fails to converge at time = 355 us step = 20.0035 as.
Disaster recovery algorithm is enabled to search for a converged solution.
Notice from spectre at time = 365 us during transient analysis `tran'.
Newton iteration fails to converge at time = 365 us step = 20.0035 as.
Disaster recovery algorithm is enabled to search for a converged solution.
Notice from spectre at time = 375 us during transient analysis `tran'.
Newton iteration fails to converge at time = 375 us step = 20.0035 as.
Disaster recovery algorithm is enabled to search for a converged solution.
Notice from spectre at time = 385 us during transient analysis `tran'.
Newton iteration fails to converge at time = 385 us step = 20.0035 as.
Disaster recovery algorithm is enabled to search for a converged solution.
Further occurrences of this notice will be suppressed.

tran: time = 500 us (2.5 %), step = 1.471 ns (7.36 u%)
tran: time = 1.5 ms (7.5 %), step = 1.471 ns (7.36 u%)
tran: time = 2.5 ms (12.5 %), step = 692 ps (3.46 u%)
tran: time = 3.5 ms (17.5 %), step = 2.099 ns (10.5 u%)
tran: time = 4.5 ms (22.5 %), step = 1.891 ns (9.46 u%)
tran: time = 5.5 ms (27.5 %), step = 1 ps (5 n%)
tran: time = 6.5 ms (32.5 %), step = 1 ps (5 n%)
tran: time = 7.5 ms (37.5 %), step = 2.168 ns (10.8 u%)
tran: time = 8.5 ms (42.5 %), step = 1.891 ns (9.46 u%)
tran: time = 9.5 ms (47.5 %), step = 1.891 ns (9.46 u%)
tran: time = 10.5 ms (52.5 %), step = 1.891 ns (9.46 u%)
tran: time = 11.5 ms (57.5 %), step = 1.891 ns (9.46 u%)
tran: time = 12.5 ms (62.5 %), step = 1.891 ns (9.46 u%)
tran: time = 13.5 ms (67.5 %), step = 1 ps (5 n%)
tran: time = 14.5 ms (72.5 %), step = 1.891 ns (9.46 u%)
tran: time = 15.5 ms (77.5 %), step = 1.891 ns (9.46 u%)
tran: time = 16.5 ms (82.5 %), step = 1.891 ns (9.46 u%)
tran: time = 17.5 ms (87.5 %), step = 1.891 ns (9.46 u%)
tran: time = 18.5 ms (92.5 %), step = 1.325 ns (6.62 u%)
tran: time = 19.5 ms (97.5 %), step = 2.17 ns (10.8 u%)
Number of accepted tran steps = 217917

Maximum value achieved for any signal of each quantity:
V: V(VL) = 17.27 kV
I: I(V9:p) = 10 A

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Post-Transient Simulation Summary
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- To further speed up simulation, consider
add ++aps on command line
- Non-default settings that could significantly slow down simulation
errpreset = conservative, default moderate
reltol = 1e-06, default 100e-06 (conservative)
abstol(V) = 10 nV, default 1 uV
abstol(I) = 10 fA, default 1 pA
- The circuit contains signals of the voltage > 10V, consider to set highvoltage=yes to get better accuracy and convergence ability.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

During simulation, the CPU load for active processors is :
Spectre 0 (99.5 %) 1 (100.0 %) 2 (99.8 %) 3 (99.2 %)
Other
Initial condition solution time: CPU = 0 s, elapsed = 308.037 us.
Intrinsic tran analysis time: CPU = 9.93949 s, elapsed = 12.4201 s.
Total time required for tran analysis `tran': CPU = 9.94149 s, elapsed = 12.4381 s.
Time accumulated: CPU = 10.2974 s, elapsed = 13.7754 s.
Peak resident memory used = 129 Mbytes.

Notice from spectre.
516 notices suppressed.

finalTimeOP: writing operating point information to rawfile.

Opening the PSF file ../psf/finalTimeOP.info ...
modelParameter: writing model parameter values to rawfile.

Opening the PSF file ../psf/modelParameter.info ...
element: writing instance parameter values to rawfile.

Opening the PSF file ../psf/element.info ...
outputParameter: writing output parameter values to rawfile.

Opening the PSF file ../psf/outputParameter.info ...
designParamVals: writing netlist parameters to rawfile.

Opening the PSFASCII file ../psf/designParamVals.info ...
primitives: writing primitives to rawfile.

Opening the PSFASCII file ../psf/primitives.info.primitives ...
subckts: writing subcircuits to rawfile.

Opening the PSFASCII file ../psf/subckts.info.subckts ...