In the near future, many distributed power systems will be connected to the utility line in the local area, the demand of the control accuracy to the utility interactive inverter will also become strict more than the present ability. The utility interactive inverter required FRT capability in the case of utility voltage fluctuation. Deadbeat control and PLL control with quasi dq transformation based on a 1MHz sampling were applied to the utility interactive inverter using FPGA based hardware controller. The FRT characteristics were verified through simulations and experiments. The superior characteristics of the proposed method was verified. The FPGA based hardware controller for the 100kHz career PWM inverter was designed and evaluated with experiments.

In the utility interactive system, the inverter output voltage has to synchronize to the a utility grid. In the case of a single phase system, it is difficult to detect the instantaneous phase angle of the utility voltage. A new high speed single phase PLL control for the single phase utility interactive inverter system is proposed. Quasi d-q trans formation and LPF function are applied to construct the PLL control with IMHz multi sampling parallel processing method based on FPGA based hardware controller. Evalua tions were carried out with simulations. Very fast detection response was achieved with stable transient operations. I. INTRODU CTIONAs the progress of the information society and the concerns to the global environmental problem, the dis tributed power system like PV generation, wind power generation and fuel cells generation has much attention in the worldwide. In these generation systems, the utility interactive inverter is necessary to connect the DC power source to the utility line.As for the single phase utility system, the internal phase of the controller has to synchronize to the utility grid. Differ from the three phase system, it is not easy to detect the instantaneous phase angle of the utility voltage. Authors proposed a high speed PLL control based on a quasi d-q transformation with a multi sampling parallel processing method [1]. The progress of FPGA technology makes it possible to realize very fast sampling while the control sampling intervals, so IMHz sampling and calculation can be applied continuously while the sampling interval. In this paper, a new IMHz sampling based quasi d q transformation is applied to construct the PLL control with multi sampling parallel processing method. In the case of the distorted utility voltage, the affection of the distortion was not negligible to detect the utility frequency. To avoid this affection, 1 st order LPF was also combined to suppress the affection of the distortion. Verifications were carried out through simulations. II. THE SINGLE-PHASE PLL CONTROL WI TH QUASI DQ TRANSFORMATION Fig.l shows a block diagram of the proposed method.Input wavefOim Vs is assumed as the utility voltage, which is sampled in ever y sampling period Ts, so the present sampled data Vs (k) can be described as equation (1). Also Vs (k -1) and Vs(k -2) can be expressed as (2) and (3). Here, VL is the maximum peak value of Vs, and Vs(k -l)is defined as V re 620 Vs Fig. 1. Block diagram of proposed method Vs(k) Vs(k-l) Vs(k-2) Vm cos(wt) Vm cos(w(t -Ts)) = Vre vm cos(w(t -2Ts)) (1) (2) (3) Differentiate (I) and (3), adapting the formula of trigonometric function (4), (5) can be derived.cos u -cos v Vs(k -2) -Vs(k) Vs(k -2) -Vs(k) 2wTs -2 sin u + v sin u -v (4) 2 2 Vm{cos(w(t -2Ts)) -coswt} Vm {2 sin(wTs) sin(w(t -Ts m v,--"'-{sin(wTs) sin(w(t -Tsm wTs Vm sin(w(t -Ts)) = V Im ( 5 ) It is obvious that the phase of Vim delays 90° than the phase of V re , so using only the single phase voltage with 3 sampled data. V re and Vim form the rectangular coordinates system same as the a-...

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SUMMARYIn the near future, many distributed power systems will be connected to utility lines in the local area. The demand for control accuracy of utility interactive inverters will likely increase beyond present capabilities. The utility interactive inverter requires FRT capability to compensate for utility voltage fluctuations. A deadbeat control with disturbance compensation and 1 MHz-PLL control with quasi-dq transformation were applied to a utility interactive inverter using an FPGA based hardware controller. The FRT characteristics were verified through simulations and experiments, and the superior characteristics of the proposed method were verified.