Abstract-Keep things simple when controlling bidirectional pulsewidth modulation rectifiers by considering the utility grid as a virtual electric machine. The advantage is that the air-gap flux of this big machine can be directly measured in a straightforward way. Therefore, as shown in this paper, principles of field orientation can be applied to control the power flow, yielding high-dynamic performance.

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Fig. 1: Autonomous system structure with bidirectional interleaved flyback converter and invertersuppress the voltage ripple on the DC-bus, however, the resultant more cost and larger component volume are not preferable in the present power electronics trend. Reference [1] proposed an active control method to reduce the low frequency current ripple in the power source (fuel cell) without more unnecessary passive storage components. Its closed voltage control loop of the DC-DC converter only possesses a bandwidth of2 Hz such that the voltage ripple of 100 Hz on the DC-bus in the steady state could be ignored and nearly decoupled with the current in the fuel cell source, therefore, the fuel current ripple is significantly reduced. However, the transient response will obviously be suffered. Williams [5] proposed a nonlinear regulation-band method in which the closed voltage control loop gain K is flexible such that the DC-bus voltage is controlled in a given range in steady state and regulated back into this range and stabilized quickly when load transients occur. This paper presents a novel dual-band controller using average current mode control (ACMC) scheme. Besides the ACMC current loop for controlling the average current of the power stage, two voltage-loop branches with two different bandwidths (2 Hz and 641 Hz) are implemented for steady state and load transients. The slow loop branch significantly reduces the battery current ripple in the steady state by decoupling the 100 Hz DC-bus voltage ripples in the allowed range with the battery current. The fast loop branch pulls the DC-bus voltage back into the allowed voltage range rapidly and the temporarily huge current peaks in the battery can be smoothed rapidly with benefit of negligible harm to the battery life. The core part of this controller is the dual-band selector. The bus voltage is divided with two bands: outer band and inner band. Outer band determines when the fast voltage loop branch is activated and inner band decides when the slow branch is switched on without pushing the bus voltage out of the outer band. Simulations demonstrate this new control method. The current ripple in the battery is only 5 % in the steady state and the response time in the transients is less than one grid cycle. Abstract-Autonomous system with DC-AC converter as an interface from the battery source to the inverter load easily suffers from voltage ripples on the DC-bus at the twice load frequency (100 Hz). A fast voltage controller for tightly regulating the DC-bus voltage with the inevitable 100 Hz ripples bears a rapid transient response, however always contaminating battery current with large ripples at 100 Hz, which do harm to the battery life span.In the paper, an average current mode controller with a novel dual-band selector is introduced. This controller has two voltage-loop branches with 5 Hz and 641 Hz bandwidths, for smoothing the battery current in the steady state and regulating the deviating bus voltage in the transients, respectively. Dual-band selector det...