Ride-through of Medium Voltage Synchronous Machine compressor drives

Medium voltage (MV) synchronous machines (SMs) are used for large industrial compressor motor drives (>15 MW). Energy savings, process and other benefits can often be achieved with adjustable speed drives (ASDs). Process availability is of primary concern since production losses can potentially negate the benefits of ASDs. It is essential to ensure that SMs ride through ASD and system faults, disturbances and supply transfers. SM and excitation system models suitable for both on-line and ASD ride-through simulations are discussed. Case studies, simulation and test results are presented for the first 11 kV voltage source inverter for 17 MW synchronous motors. Further case studies are presented for a 55 MW synchronous motor. It is shown that line fed and ASD fed SMs can survive system faults and voltage dips without additional compensation or energy storage. ASD fed SMs have far better survivability characteristics than line fed SMs and can survive faults cleared by system back-up protection. It is shown how SMs can ride through ASD faults associated with fault tolerant schemes. Boundary parameters are investigated to eliminate unacceptable transient torques associated with ride-through operation. Recommendations are provided to improve availability of ASD driven machines.