Energy Compression And Power Extension Methods For Spacecraft Power System

The mass of spacecraft power system is more than 30% of that of the whole spacecraft. Traditional PCU architectures based on S3 R.etc are all with low power density, and the integration performance is poor. For laser or communication applications, repetitive pulse load with high power is always required. This brings new problems: lifetime of battery will be shortening when unregulated architecture with battery bus used; If regulated bus architecture(for example S3R) is used, the battery and PV arrays of power system must be equipped according to the peak load power, which will incur high cost and low power density. On the other hand, modularity performance of power system is necessary for power capability increasing. Even power sharing is required among multiple po wer systems. So the research on the energy compression and extension method is important for improving the power density or performance of spacecraft.Traditionally, three different DC/DC converters(PV array power regulator, battery charge regulator and battery discharge regulator) would have been used. To improve the power density of the PCU, an integrated solution of three ports DC/DC converter is proposed in this paper. By proposing shunt regulator with high parasitic capacitance adaption and tracking maximum power point of PV, the number of PV arrays can be decreased, realizing the energy compression of power system. For repetitive pulse power load, the power is compress when load power requirement is small, and the compressed power is released when load power requirement is high. So the energy compression in time axis can be achieved, and the equipped PV array and battery cells can be reduced greatly. Power sharing method for multiple spacecraft power systems has also been researched, and the power can be extended in multi-system level. The detailed information is listed as follows:This paper deals with the influence produced by the solar array parasitic capacitance and it’s solving methods in the S3R(Sequential Switching Shunt Regulator). Nowadays, the usage of triple junction Ga/As solar cells with larger parasitic capacitance has prompted new problems about power losses, steady state and dynamic response in the S3 R especially for high section current, voltage applications. Effects of parasitic capacitance on voltage ripple, ―double sectioning‖, phase margin and output impedance are represented and analyzed. A novel shunt regulator topology with low switching losses, low mass and short turn off time delay is proposed. To further reduce the impact of delay, non-linear PD control is added in the control loop, achieving better performances in the stability margin, output impedance and dynamic performance.To reduce the cost and improve the power density of the power system, an integrated solution of PV isolated three ports DC/DC converter(TPC) is proposed in this paper. Zero current switching(ZCS) can be achieved for all main diodes and MOSFETs to improve the efficiency, and a continuous input current of solar array is maintained by adding a magnetic switch derived from a fourth winding of the half-bridge transformer. Based on the energy balancing part formed by boost, the control methods for the single module or for multi-modules in parallel are also derived.Further improving the power density of the power system, a novel non-isolated three-port DC/DC converter and its control method based on three domain control are proposed in this paper for power conditioning. The proposed converter features high integration and single-stage power conversion from both photovoltaic(PV) and battery ports to the load port, thus leading to high efficiency. The current of all the three port is continuous, so the electromagnetic noise can be reduced. Furthermore, the control and modulation method for B3 C has been proposed f or realizing Maximum Power Point Tracking(MPPT), battery management and bus voltage regulation simultaneously.Power magnetic components integration has been done in the proposed three-port converter. High side switch driver and current ripple cancellation network have also been integrated in it for realizing ―zero current ripple‖ and switch driver simultaneously. A novel repetitive pulse power conditioning method is presented for energy compression in time axis, which converts the DC power to the pulse power with steep pulse edge and specified amplitude flatness. Full regulated bus power system design for peak load power can be avoided.Finally, a simple, modular, highly stability margin and autonomous power sharing method is proposed for ―energy intranet‖ based on multiple S3 R power systems. The simulated analysis and experimental results demonstrated the effectiveness of the proposed control method. Thus power extension among multiple power systems can be achieved.