Low-frequency operation control method for medium-voltage high-capacity FC-MMC type frequency converter

Figures & data

Figure 1. Topology of the FC-MMC converter.

Figure 2. FC-MMC simplified single-phase equivalent circuit diagram.

Figure 3. Low-frequency control block diagram of the FC-MMC: (a) Permanent magnet synchronous motor control $i_{\text{d}}^{\ast }=0$; (b) inter-phase capacitive-voltage control; (c) capacitive-voltage control between upper and lower bridge arms; (d) half-bridge arm capacitor voltage control; (e) independent control of the capacitance voltage of the SMs.

Table 1. Simulation parameters of FC-MMC drive rotary motor.

Parameters	Value
Number of upper (lower) bridge arm SMs N	6
DC side voltage level Udc/V	4000
SM capacitance Csm/F	4.5e-3
SM capacitance voltage Uc/V	666
Sub-bridge arm inductors L/H	2.5e-3
Fly span SM capacitors CF/F	2.6e-4
Carrier frequency fz/Hz	5000
Turntable motor fhigh/Hz	15
Turntable motor flow/Hz	5
Injection of HF fh/Hz	200
Number of pole pairs of turntable motor P	40
Rated speed/(r/min)	45
Turntable motor rated frequency fk/Hz	30
Stator resistance of turntable motor/Ω	0.08
Rotational inertia J/(kg·m^2)	4500
Motor speed outer ring Kp/Ki parameters	4.5;75
Motor current inner loop Kp/Ki parameters	1.5;30

Figure 4. Simulation results from start-up of the rotary motor to rated speed: (a) turntable motor speed; (b) turntable motor output torque; (c) turntable motor stator current.

Figure 5. Simulation results of FC-MMC start-up to rated speed: (a) FC-MMC upper and lower half-bridge arm current; (b) FC-MMC upper and lower bridge arm individual SM capacitance voltage; (c) FC-MMC fly span SM capacitor current waveform; (d) FC-MMC fly span SM capacitance voltage waveform.

Figure 6. Simulation results of the rotary motor under variable load and stuck drilling conditions: (a) turntable motor speed; (b) turntable motor output torque; (c) turntable motor stator current.

Figure 7. Simulation results of FC-MMC under variable load and stuck drilling conditions: (a) FC-MMC upper and lower half-bridge arm current; (b) FC-MMC upper and lower bridge arm individual SM capacitance voltage; (c) FC-MMC fly span SM capacitor current waveform; (d) FC-MMC fly span SM capacitance voltage waveform.

Figure 8. Simulation results of rotary motor inversion condition: (a) turntable motor speed; (b) turntable motor output torque; (c) turntable motor stator current.

Figure 9. Simulation results of FC-MMC inversion condition: (a) FC-MMC upper and lower half-bridge arm current; (b) FC-MMC upper and lower bridge arm individual SM capacitance voltage; (c) FC-MMC fly span SM capacitor current waveform; (d) FC-MMC fly span SM capacitance voltage waveform.

Figure 10. Simulation results comparing MMC with FC-MMC: (a) MMC motor side CMV waveform; (b) MMC upper and lower bridge arm individual SM capacitance voltages; (c) MMC bridge arm circulation; (d) FC-MMC AC side CMV waveform; (e) FC-MMC upper and lower bridge arm individual SM capacitance voltages; (f) FC-MMC bridge arm circulation.