DC Capacitor-Less Inverter for Single-Phase Power Conversion With Minimum Voltage and Current Stress

Abstract

Single-phase power conversion such as PWM rectifier, grid connected PV inverter system, static synchronous compensator ( STATCOM ) all can be implemented by an H-bridge inverter and a large electrolytic dc capacitor to absorb the ripple power pulsating at twice the line frequency (2ω ripple power). This paper proposed a dc capacitor-less inverter for H-bridge with minimum voltage and current stress. By adding another phase leg to control an ac capacitor, the 2ω ripple power can be absorbed by the capacitor and theoretically 2ω ripples to the dc capacitor can be eliminated completely. The H-bridge and the addition phase leg can be analyzed together as an unbalanced three phase system. By adopting SVPWM control and choosing the optimum ac capacitance and the voltage reference, the voltage and current stress of the switches can be minimized to the same as the conventional H-bridge. The size of capacitor is reduced by 10 times compared to the conventional H-bridge system. Simulation and experimental results are shown to prove the effectiveness of the proposed dc capacitor-less inverter and active power decoupling method.PR controller parameters are as follows: k p =8, k r =11,  c =25, and the bode plot is shown in Fig. 8 (b).Accordingly, the transfer function from ac capacitor current reference to ac capacitor current is:0885-8993 (c)

An Enhanced DC-Bus Voltage-Control Loop for Single-Phase Grid-Connected DC/AC Converters

“…where 1 and 1 are defined in (9). On the other hand, due to the fact that 1 and 1 are the amplitudes of the stationary quantities of bus ( ), and also considering the magnitude of the bus-voltage ripple given by (8), they can be represented by This concludes that 1 and 2 contain the dynamics of d and q through a simple low-pass filter:…”

“…16(c) by means of the Fast Fourier Transform (FFT) of s before and after applying the proposed method. Figure 17(a) shows the system`s operation during load switching from 3 kW to 1 kW, that changes ripple from 25 V to 8.4 V respectively (according to (8)). As shown, when the proposed method is used, the bus voltage exhibits lower fluctuation during such a disturbance.…”

“…This compromises the lifetime, size and cost of the converter [1,3,6,7]. Another solution is to use an auxiliary circuit that draws constant current from the source and creates a high dc voltage to provide the needed pulsation [7][8][9][10]. However, this increases the complexity of both the hardware and the control system and decreases the efficiency.…”

A new active power‐decoupling topology and control mechanism to extend the lifespan and reduce the number of passive components

“…V b is the root mean square (RMS) value of v b . At steady-state conditions and neglecting circuit loss, the power of each stage in the proposed converter can be derived as follows [20], P in_avg + P in_r = P out + P b_r + P b_avg (7) Assuming that ripple power is removed by the decoupling circuit, we can eliminate P in_r and P b_r in (7) to give If the proposed converter works in DCM, I m can be rewritten as…”

“…The advantage of this approach is that the use of film capacitors ensures a long lifespan and high reliability, and it can be applied to existing converter circuits with a few modifications [5]. The APD method has been applied to many applications that need to increase the lifespan and reliability of power converters [6][7][8][9][10].…”