Research On Dual PWM Model Predictive Control Strategy Based On Improved Load Power Feedforward Control

The dual PWM converter has the characteristics of small current harmonics on the grid side,adjustable DC voltage and bi-directional energy flow.It is widely used in agriculture,industry,transportation,national defense and electric power.Compared with the traditional converter,the dual PWM converter has the superior performance such as high performance,high efficiency and high stability,which is more competitive and influential in the market.In this paper,the control performance analysis and algorithm design of independent control and coordinated control of double PWM converter are deeply studied.In this paper,the dual-PWM converter is taken as the research object.First of all,the mathematical model of PWM rectifier and permanent magnet synchronous motor are established.According to the shortcomings of direct power control(DPC)in rectifier and direct torque control(DTC)in inverter,for example power and torque ripple is large.Model predictive control is introduced into the control of rectifer and inverter sides to form model predict direct power control(MPDPC)and model predictive direct torque control(MPDTC),it reduce the power pulsation and torque ripple,and improve the system's steady-state performance.Both rectifier side MPDPC and inverter side MPDTC's steady state performance are improved by establishing the objective function to achieve online optimization.However,there are problems which the switching frequency is not fixed,the amount of online computation is large,and the system is delayed.In order to solve these problems,the constant frequency MPDPC is realized based on the space voltage vector modulation method and the constant frequency MPDTC is realized based on the duty cycle modulation method.In addition,an advanced two-step prediction control method is adopted for delay compensation.It can be seen that the improved control algorithm has the advantages of high control precision,fixed switching frequency and low current harmonic content by simulation.Finally,for the research of double PWM integrated coordinated control,power flow analysis is carried out on the basis of load power feedforward control.In order to obtain more accurate feedforward compensation power,the energy stored in the inductor and the capacitor is added to dynamic power compensation in feedforward power.In order to solve the dependence of the model predictive control on the accurate parameters,the voltage outer loop is improved.A new discrete sliding mode surface which takes the square error of the DC voltage as the state variable is designed instead of the traditional PI control.Combined with the dynamic compensation,the active power of the feedforward compensation is recalculated,which enhances the system's immunity and robustness,reduces the DC bus fluctuations and achieves better control performance.