convergence problem while running load flows for ieee 37 node test feeder using simulink ?

I have referred matlab example IEEE 13 node distribution feeder for conducting loadflows for the research. Now, i have performed the simulink model for IEEE 37 distribution feeder using IEEE PES Test feeder data. But, while the data is having negative value of reactance X between mutual phases(Xab,Xbc,Xca) for some line configurations, MATLAB is throwing an error i.e. inductance values must be positive for distribution line. In case of IEEE 13 node simulink example, the positive sign is considered in place of negative sign of reactance X. Hence, i have changed the negative sign of X to positive sign value. But now, the simulink model is giving load flow error i.e. load flow did not converge. Is there any modification required for IEEE 37 data to getconvergence? Kindly help me for clearing this problem. Or anyone please provide the standard distribution load flows program(using forward backward sweep method) which will work for any unbalanced distribution test feeders like IEEE13, 37, and 123 systems.