Comparative Analysis of Two Modulation Strategies for an Active Buck–Boost Inverter

Abstract

The inverter used in new energy power generation system should have the ability to adapt a wide range of DC input voltage. Based on the active buck-boost inverter which consists of a full bridge and Boost AC/AC part, two modulation methods are compared: constant boost ratio modulation and dual mode modulation. Along with the relationship of the input DC voltage and the reference AC voltage, the converter completes buck or boost inversion with different equivalent circuits and there are fewer switches working at high frequency in dual mode modulation, which is in favor of the system with high efficiency. The current of the inductor and the current stress of the switches is analyzed in this paper. Experimental results are presented to verify the proposed topology can achieve dual mode operation with wide range of input voltage.Index terms-wide input, buck-boost inverter, constant boost ratio modulation, dual mode modulation I. INTRODUCTIONWith the development of the new energy, more and more attention is paid to inverters which can convert the DC voltage to AC voltage. According to whether there is isolation, the inverter can be divided into isolated and non-isolated type [1]-[3].The isolated type with a transformer has bigger volume and a higher cost, which is a disadvantage for new energy power generation system [4]-[5]. Influenced by the light, temperature and so on, the output voltage range of PV cell is very wide [6]-[7]. The output voltage of the single fuel cell is very low. If too many cells are in series, the voltage sharing is difficult to realize. So the inverters should have the ability to boost the input voltage [8].The non-isolated inverters also can be divided into single-stage inverters and multi-stage inverters [9]- [11].Boost cascaded inverters and buck-boost cascaded inverters are typical two-stage inverters [12]- [13]. The two-stage structure has many inductors and capacitors which are not suitable for integration. The DC bus needs big electrolytic capacitor which reduces the power density, is aging easily and has a short service life. On the other hand, 0885-8993 (c)

Investigation of single‐stage transformerless buck–boost microinverters

“…The topology can be split into DC-AC inverter and AC-AC unit, here former will accomplish buck operation and the latter will perform boost operation. The same configuration is tested using two control techniques such as: constant boost ratio modulation and dual mode modulation in [58]. Dual mode modulation achieves an improved result with high efficiency and reduced current stress over switches.…”

Robust feedback‐linearisation control of a boost converter feeding a grid‐tied inverter for PV applications

“…From (3) and (17), it follows that the disturbance estimation error e b = b^− b is governed by e˙b = − μB b e b − b˙ (22) Therefore, with assumption (6), the asymptotic stability of the DO can be guaranteed by an appropriate choice of the observer gain matrix μ. More specifically, by considering the structure of B b , it is clear that the DO can be made stable by choosing μ 1, 2 > 0, which makes the matrix − μB b Hurwitz.…”

“…For a gridconnected operation, either single or dual-stage inverter can be used in PV applications. The single-stage PV inverter is attractive and offers numerous advantages depending on the power converter topology [2][3][4][5]. A typical topology of the dual-stage inverter consists of a dc-dc boost converter and a dc-ac inverter, as shown in Fig.…”

A Family of Single-Stage, Buck-Boost Inverters for Photovoltaic Applications

“…It has only four switches; on the contrary, a rather complicated control method is needed. An active buck-boost inverter using an "AC/AC unit" to realize the buck-boost conversion was introduced in [15,16], as presented in Figure 1e. Yet, each unit consisted of four switches, and, thus, in total, eight switches are needed for the microinverter.…”

“…Doing so significantly increases the total number of switches (i.e., eight). Although the ideas of [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are very interesting, their attained voltage gain is comparable to the traditional buck-boost converter.…”