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This paper focused on the research on one-step-delay effect of the stability of digital control PWM Inverter. Discrete stability criterion is used to research the stability of discrete system with/without one-step-delay control respectively. The research results are shown that the one-step-delay control degrades the stability system in the high sample frequency while it may increase the stability range compared with no one-step-delay control in some low frequency band. The unique phenomenon in the low sample frequency is explained by the analysis of frequency domain and root locus. So it is deduced that the introduction of predictive control can not improve the performance of inverter in any sampling frequency. Predictive control can upgrade the performance of inverter only in the high sample frequency.

This paper focused on for the stability of spwm inverter affected by digital control. The stability of analog control inverter system, discrete system with no-step-delay control and discrete system with one-step-delay control are analyzed respectively so as to determine the relation of the inverter's sampling period vs. controller parameters with critical stability. Then the essential reason was analyzed why the stability of digital control inverter was degraded compared with analog control inverter even if the sample frequency is ten times greater than the closed-loop bandwidth. The conclusion with realistic instructive significance had been drown clearly that one-step-delay control makes stable range of controller parameter larger than no-step-delay control in some low sample frequency.

Compared with analog control, digital control adopted in PWM inverter possesses the evident advantages but the traditional PID control strategy which is realized in digital method often can't achieve better performance than in analog control. In past references, there is hardly quantitative analysis on the effect of digital process on the performance of PWM inverter. This paper did a creative research about the zero-order-hold process and one-step-delay control effect on the performance of PWM inverter. The process of zero-order-hold and one-step-delay control were analyzed why the digital process influences PWM inverter's performance in this paper. The process of zero-order-hold and one-step-delay control varies the system's stability with sample time. Zero-order-hold reduces the stable scope to a large extent compared with analog control, and limits the performance improvement of digital control system. One-step-delay with different sample time brings different influence on the system stability. Finally relevant experiments in a single phase inverter verify the theoretical analysis on the effect of digital process on the performance of PWM inverter.

The traditional PID control strategy which is realized in digital method canpsilat achieve better performance than that in analog control. The reason was analyzed why the digital process influences the digital controlled PWM inverterpsilas performance in this paper. One is the process of the zero-order hold. Another one is one-step-delay control which is usually adopted in digital control. Three aspects were analyzed in which influence the digital controlled PWM inverterpsilas performance: (1) how the process of zero-order-hold effects the open-loop frequency property of the digital controlled inverter system (2) how the process of zero-order-hold effects the systempsilas stability (3) how the one-step-delay control effects the systempsilas stability. On the base of setting up discrete mathematical model of the digital controlled inverter system, theory deduction and simulations were done in the condition of P regulator Relevant experiments verify the rightness of the analysis and direction for the design of the digital controlled PWM inverter were given. Finally relevant experiments verify the theoretical analysis.

A superconducting magnetic energy storage (SMES) unit consisting of a voltage source converter (VSC) and a chopper is used to damp the oscillation of a synchronous generator. The state feedforward decoupling method based on synchronous frame is used to improve the dynamic response of the VSC. The work modes of the chopper are discussed, and a small signal model of the chopper is established for the regulator design. Simulations and experimental results demonstrate the dynamic performance of the SMES unit.

A prototype, double-DSPs controlled power conditioning system (PCS) for super-conducting magnetic energy storage (SMES), is used for experimental study in dynamic simulation test of power system. The function of SMES is to improve the dynamic performance of a single-machine infinite bus for power system. The experimental results show that the transfer of SMES energy is done almost immediately depending on the system requirement, and SMES is able to restore system stability for short circuit. The control algorithms for the SMES are simple and implementation has required very a little hardware.

This paper gives a survey of the topologies of three phase inverters common in use. Models of decoupled and coupled systems are obtained. The symmetrical component decomposition method is adopted to model and analyze the strongly coupled topologies. Simulations verify its feasibility and exactness

CVCF inverters are usually applied in critical situations, whose quality of output waveform is one of the most important aspects in evaluating its performance. This paper analyses the feasibility of the three-phase inverters' output waveform control scheme based on internal model theory in rotating frame. One scheme is present which is the combination of instantaneous feedback control internal model restraining fundamental component disturbance and repetitive control internal model restraining harmonic component disturbance and asymmetrical disturbance. The experiments verify the scheme can work well. Fast response, highly accurate steady output and less distorted waveform is gained.

One problem with microprocessor-based high-frequency PWM power converters is resolution limitation caused by the hardware timer. In this paper, a novel PWM technique-double PWM-is proposed. DPWM combines the advantages of low frequency modulating and high frequency switching in power conversion, and effectively increases the resolution in digital control. Theoretical analysis and features are verified on a boost-buck converter with an improved control scheme.

This paper introduces a double-DSP controlled power-conditioning-system (PCs) for experimental SMES. Voltage-source-converter (VSC) with a chopper is employed in the experimental sample. The VSC is a four-quadrant-AC/DC converter and chopper is a two-quadrant-DC/DC converter, they can perform charging to or discharging from the coil. The proposed system is feasible by results of experiment.

This paper introduces a double-DSPs controlled power conditioning system (PCS) for superconducting magnetic energy storage (SMES), which is used for experimental study in dynamic simulation tests of power system. Considering of realization, voltage source converter (VSC) with a chopper is adopted in the experimental sample. The VSC in the PCS is a four-quadrant AC/DC converter and chopper is a two-quadrant DC/DC converter, they can perform the functions of charge to or discharge from the coil. In this paper, a kind of configuration of PCS and synchronous frame based control method for SMES has been presented for seeking a better control algorithm in improving stability and damping low-frequency-osciliation. The experimental results are verified to agree well with analysis.