H.-G. Zhang’s scientific contributions

Based on the mathematical model of the surface PMSM, a backstepping controller with sliding mode variable structure is proposed. Sliding mode variable structure based on exponential reaching law enhances the quick response and anti-disturbance ability of the control system. The integral action contained in the sliding surface can ensure the steady state error of tracking velocity zero. At the same time, extended state observer is used to evaluate the load torque of the system online, so the control process can be adjusted timely, which leads to the parameters of exponential reaching law being more smaller. Theoretical analysis and Matlab simulation results show the effectiveness of the proposed method.

With the goal of producing a soft switching boost converter having a simple structure, high efficiency, high frequency, low voltage stress, and ease of control, a new zero-current soft-switching pulse frequency modulation (PFM) converter was described herein. The operation principle of this converter is explained using the boost converter as an example. The soft switching and other design aspects are also outlined in detail. Simulation and experimental results show that the converter can produce a steady zero current swith under a relatively broad range of changes in output and input voltage, load, and control frequency. This new soft switching cell can also be used in other basic DC-DC converters.

Based on the energy-shaping and the interconnection and damping assignment passivity-based control method, the model of the port-controlled Hamiltonian(PCH) control system for the surface permanent magnet synchronous motor(SPMSM) was designed. On this basis, a new double loop speed control PCH system was proposed for PMSM. The outer loop control was employed by sliding mode controller to determine anticipant q axis current. In the ineer loop, passivity-based control was designed to produce the ud and uq. A novel speed sensorless method was put forward by using a sliding mode control based adaptive speed estimator, which could reduced cost and system's reliability was enhanced. The simulation results show that the method is effective and the system has a satisfactory performance.

A novel surface permanent magnet synchronous motor(SPMSM) speed control system is designed by using nonlinear syncretized control method. Adaptive sliding mode speed controller is presented based on the extended state observer(ESO) which observes the part of disturbance, and then compensates it to the system. The derivative of adaptive control estimates the unknown uncertainty upper boundary. Active disturbance rejection-passivity-based current controller is proposed, which simplifies the controller's design, and strengthens the system's robustness and the rapidity in the stable foundation. The simulation results show that the advantages of adaptivity, strong robustness against parameter variations and load disturbance are achieved by using this method, and the system has a satisfactory dynamic and static performance.

In order to realize a simple topology, high efficiency, high frequency, low voltage stress, easy to control soft switching three phase inverter, A novel Passive Assisted Soft Switching Converter is presented in the paper. Soft Switching of the switch can be achieved by using Passive Assisted Resonant network. It is very attractive for high power application where IGBT is predominantly used as the power switch. Its operation principle is analyzed through its application to the boost converter. The condition of soft switching and the design considerations are analyzed in detail. The novel soft switching cell can be also used in other basic dc-dc converter. A 5 kW~20 kHz prototype which uses IGBT (insulated gate bipolar transistor) is made. The effectiveness of the proposed converter is confirmed by the experimental results.

A control scheme based on three-phase integrated compensation is proposed for four-leg inverter. The functions of four legs are analyzed in the power conversion process, and the integrated compensation strategy for three-phase voltages is formed. In the proposed compensation strategy, unbalanced factor is compensated by the fourth leg, and phase voltages are synthetically compensated by the fourth leg and every phase legs, so that the advantage of the four-leg topology is exerted and the control ability is increased under the resistance and inductance unbalance loads. Based on the integrated compensation strategy, an integral algorithm is proposed to approach inductor voltage according to the property that inductor current is sine-wave, a closed-loop control structure is constructed, and an integrated control scheme is proposed for four legs. The proposed control scheme avoids high frequency interference introduced by the differential algorithm and the phase difference made by additional filters, and makes output voltages converge on the ideal waveform. The effectiveness of the proposed control scheme is verified by simulation results.

In view of the speed regulation and estimation problem of permanent magnet synchronous motor(PMSM), a speed modulation system based on speed sensorless for PMSM is proposed. The adaptive fuzzy sliding mode soft switch controller is designed by using the replacement of sgn(x) function by tanh(x) function, which realizes the soft switch control and reduces chatting. A robust passivity-based control algorithm is constructed to obtain the ud and uq based on the passivity-based control principle. An adaptive sliding mode observer is established and a speed identification law is proposed, and the gain matrix of the observer is obtained by solving linear matrix inequalities. The simulation results show that the proposed strategy is effective, and the system has a satisfactory performance.

A novel resonant DC link soft-switching inverter was proposed to improve the efficiency and performance of inverter. Auxiliary resonant unit was added to DC link of conventional inverter to make DC-bus voltage decrease to zero periodically, which realized zero-voltage and zero-current operation of all switching devices in inverter and reduced switching losses and reverse recovery losses of diodes. Furthermore, switching devices in the auxiliary resonant unit worked on and off under zero current switching. In addition, the control is simple and less dependant on load current, and the time of transition is freely selected. The equivalent circuits at different operation modes, the analysis of the circuit and parameter design method were presented. A 10 kW laboratory prototype has been built. Experimental results were proposed to confirm validity of soft-switching inverter presented.

A novel interleaving double switch forward zero-voltage and zero-current soft-switching pulse width modulation (PWM) DC-DC converter was presented. Compared with conventional interleaving double switch forward PWM DC-DC converter, this converter doesn't include auxiliary resonant circuit. It can achieve soft-switching for the active power switches by the tapped-inductor type smoothing filter, lossless snubber capacitors and transformer parasitic inductors. This converter can reduce the voltage of the switch, current peak and circulating current loss of the circuit without transformer saturation effect. The principle of new type converter and soft-switching implementation condition according to the different equivalent circuits was analyzed. The practical effectiveness of the proposed converter was illustrated by the simulation results and experimental results via 500W-100 kHz prototype using the fast switching insulated gate bipolar transistor (IGBTs).

In order to realize a simple topology, high efficiency, high frequency, low voltage stress, easy to control soft switching three phase inverter, a novel resonant pole three phase soft switching PWM inverter is presented in the paper. It avoids the bulk capacitor of the auxiliary resonant commutated pole inverter (ARCPI) and no center tap potential variation problem of ARCPI, the inverter possessed the advantages of the decoupled resonation of each phase, and it was easy to implement the various control schemes. The operation principle of one phase circuit has been analyzed and the equivalent circuits at different and optimum circuit were designed. The simulation and experimental results prove that it realizes soft switching of the main switches and the auxiliary switches and possesses the small power auxiliary circuit and full PWM capability. It is of great significance to reduce electro management interference (EMI) and improve efficiency.