| In renewable energy power generation, distributed power supply system, electricvehicles and other applications, switching power converter plays an important role as aenergy conversion interface. However, in these applications system it often appears withsuch situations of the input voltage and the load current changing abrupt, for example inphotovoltaic (PV) generation appliacation and pulse load cases. In addition, it isdifficuilt for the traditional linear control schemes to gurratee the system stability andgood dynamic performance when a large range variation of system parameters.Therefore, it is a new challenge in theses systems to finish the stability design ofswitching power converter. For the stability limitation problem of the linear controlmethod, this paper takes the DC-DC switching converter and DC-AC inverter as theresearch objects and explores the large-range stability nonlinear control strategies. Atthe same time, the proposed control schemes also aims at improving the system’sdynamic performance. The achievments abtained in this paper can provide a feasiblesolution for a stable and reliable operation of power electronic system. The specificresearch work and achievements are listed as follows.Firstly, regarding to the stability limitation of traditional linear controller, animproved wide-range stability control strategy derived from the Lyapunov directmethod (LDM) is proposed. The improved Lyapunov control strategy I is obtainedthrough redisigning the Lyapunov energy function and outer voltage loop. A polynomialLyapunov energy function with a new integral term of current error is constructed andthe system convergence is analyzed. By the introduction of a simplified outer voltageloop structure and rational selection of control parameters, the equivalent analog controlcircuit is obtained implemented with the integral reset circuit. The given simulation andexperimental results confirm the validity of the proposed control scheme. On this basis,an improved Lyapunov control strategy II with a ripple current compensation isproposed. The ripple current compensation signal is introduced into inner current loopwith a matched control parameters and the system steady-state error is obtained in thisproposed scheme. Simulation and experimental results show that the proposed controlscheme has a better load dynamic over the previous uncompensated case. This part ofresearch work provides a feasible solution to the large-range stable control scheme.Secondly, a ripple-current modulation strategy with fast load dynamic performance is proposed. Taken the Buck converter as our example the corresponding controlequation is constructed in this section. A corresponding switching surface function isbuilt to verify the stability of the proposed control scheme. The proposed controlstrategy can promise the system stability for a wide range of load variation. Thesimulation and experimental results show the effectiveness of the proposed controlscheme. Overall, compared with the traditional PID control scheme the circuitimplementation of the proposed scheme is simpler and a better dynamic performance isachieved as well. This part work gives both stability and good dynamic performance ofthe non-linear modulation schemes.Finally, as for the problem of load stability limitation in the PI controlledvoltage-type single-phase inverter, this paper explores two kind stability schemes, anadditional filter-based compensation and LDM (Lyapunov derective method) basednonlinear control, respectively. A filter-based perturbation signal is adding to thetraditional linear control loop and hence the system stability can be broadened and theproblem of load stability is avoided. Moreover, a stability control strategy for thesingle-phase buck inverter is derived with the Lyapunov direct method. Theexperimental results of the two different control schemes are given respectively and itshows that the proposed schemes could improve the system stability well. This partwork provides the feasible way of improving load stability of switching powerconverters from the perspective of control strategy. |
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