A new single DC source five-level buck-boost inverter for single phase application

ABSTRACT


INTRODUCTION
In recent decades, inverters have advanced relatively quickly as a method of converting energy from DC to AC.The transmission and distribution of electrical energy employ this energy conversion technique extensively [1].Voltage source inverters (VSI) and current source inverters (CSI) are two broad categories for inverters [2]- [4].The most often used inverters are voltage source inverters, which have a few advantages including low cost and easy control [5].Due to the fluctuating input DC voltage, voltage source inverters are typically only able to function in step down voltage (buck mode) [6], making them unsuitable for use in photovoltaic (PV) systems [7].In order to this system to provide a greater output voltage, an inverter is typically needed [8].The buck-boost inverter was created as a solution to this problem since the inverter needs to be able to operate in both step-down and step-up voltage modes (buck-boost mode) [9], [10].
Although the output voltage range of a buck-boost inverter can vary widely, it is useful for applications with a fixed DC source because it can be used as either a buck or a boost [10].A boost type DC-DC converter followed by a conventional VSI inverter is another method for achieving a buck-boost mode of operation [5], [11].For the buck-boost mode of operation to be enabled by the combination of the two converters, the DC-DC converter will play the function of boosting voltage while the VSI inverter will play the duty of reducing voltage [12].Vazquez et al. [13] and Chang et al. [14] presented this application of the topology concept, but it has constraints on the construction because it calls for many inductors and capacitors.The intended topology is more appealing to build since it has fewer, more passive components.Tang et al. [15] introduced a buck-boost inverter in his research that combines a full bridge inverter and an AC-AC converter to reduce the number of passive components.Due to the application of a two-stage inverter in the buck-boost inverter test, the output has poor power quality [16]- [18] and requires a large filter size.A multilevel inverter can be used as a solution because this form of inverter also has significant switching losses and frequency.Multilevel inverters have waveforms that are more close to sinusoidal waves and reduced harmonic distortion, which improve output [19]- [21], necessitating smaller, more affordable filters [22].Danyali et al. [23] and Matiushkin et al. [24] investigated a single-phase inverter combined with a boost DC-DC converter, which was composed structurally of two converters, two separate controls for the boost DC-DC converter, and an H-type inverter.Moreover, multilevel inverters are more efficient because they operate at lower switching frequencies, which lowers switching losses and puts less strain on switching components [25], [26].The five-stage inverter in use is a result of research in [27] and work done in the research section on boost [15].Pujianto and Pratomo [27] employs many switches, resulting in a complex control scheme.However, some of the switches are controlled at the zero-crossing detector.An improved output buck-boost multilevel inverter is suggested based on the information provided above.In this study, a single voltage source in a single-phase system was used to evaluate a five-level buck-boost inverter.
A sinusoidal pulse width modulation-based control structure that derives an operating mode from the suggested inverter will be further discussed in section 2. The proposed new power circuit and control structure was initially verified through computational simulations.The last step is a hardware test in the lab to conduct additional verification.In section 3, a comparison between simulation and implementation is also covered in more detail.

RESEARCH METHOD
Three components make up the new five-level buck-boost inverter architecture that is being suggested, as shown in Figure 1.The first component is a five-level inverter with six level-setting switches (S1-S6).A boost converter circuit with two switches Q3 and Q4 that operate on positive and negative cycles is presented in the second component.The AC-AC converter, which is the third component, is made up of two Q1-Q2 power switches.These three converters will be combined to create a new five-level inverter with one voltage source that can operate in both buck mode and boost mode.

Buck operation
Switches Q1 and Q2 are always on while Q3 and Q4 are off in buck mode.A voltage level will be created by the interaction of the switches S1-S6.It has six operating modes in this buck operation mode, as depicted in Figure 2.

Operating mode 1
Switches S2, S6, and Q2 are turned on in operating mode 1 so that the DC supply and load can be connected.Figure 2(a) shows the direction of current flow in operating mode 1.The mathematical equation for operation mode 1 is presented in (1).

Operating mode 2
Switches S3, S6, and Q2 are turned on in operating mode 2 so that the DC supply and load can be connected.337

Operating mode 3 and 4
When switches S6 and Q2 are turned on in operating mode 3, the current rotates to the load during a positive cycle, as shown in Figure 2(c).When switches S5 and Q1 are turned on in operating mode 4, the current rotates to the load during a negative cycle, as shown in Figure 2(d).The mathematical equation for operation mode 3 and 4 is presented in (3).

Operating mode 5
Switches S1, S5, and Q1 are turned on in operating mode 1 so that the DC supply and load can be connected.Figure 2(e) shows the direction of current flow in operating mode 5.The mathematical equation for operation mode 5 is presented in (4).

Operating mode 6
Switches S5, and Q1 are turned on in operating mode 1 so that the DC supply and load can be connected.Figure 2(f) shows the direction of current flow in operating mode 6.The mathematical equation for operation mode 6 is presented in (5).

Boost operation
During boost operation, switches Q3 and Q4 that operate half on positive and half on negative cycles will short circuit the DC supply (Vin) and the inductor (L).The Q2 and Q1 switches, which are half positive and half negative cycles, will forward the voltage at the inductor during the source voltage cycle, which is the

The positive half cycle, operation mode 1
In operating mode 1, switches S2, S6, and Q3 are activated, causing the DC supply and inductor are connected.Figure 3(a) shows the direction of current flow in operating mode 1.The mathematical equation for operation mode 1 is presented in (6).

The positive half cycle, operation mode 2
In operating mode 2, switches S2, S6, and Q2 are activated, causing the DC supply and inductor to forward the voltage and produce the output voltage greater than the DC source.Figure 3(b) shows the direction of current flow in operating mode 2. The mathematical equation for operation mode 2 is presented in (7).

The positive half cycle, operation mode 3
In operating mode 3, switches S3, S6, and Q3 are activated, causing the DC supply and inductor are connected.Figure 3(c) shows the direction of current flow in operating mode 3. The mathematical equation for operation mode 3 is presented in (8).

The positive half cycle, operation mode 4
In operating mode 4, switches S3, S6, and Q2 are activated, causing the DC supply and inductor to forward the voltage and produce the output voltage greater than the DC source.Figure 3(d) shows the direction of current flow in operating mode 4. The mathematical equation for operation mode 4 is presented in (9).

The positive half cycle, operation mode 5
In operating mode 5, switches S6, and Q3 are activated, causing the current freewheeling around the inductor.Figure 3(e) shows the direction of current flow in operating mode 5.The mathematical equation for operation mode 5 is presented in (10).

The positive half cycle, operation mode 6
In operating mode 6, switches S6, and Q2 are activated, causing the inductor to forward the voltage and produce the output voltage as the same as inductor voltage.Figure 3(f) shows the direction of current flow in operating mode 6.The mathematical equation for operation mode 6 is presented in (11).
Thus, the buck inverter could be represented in an equation as follows for the total operation mode ( 1)-( 5), and boost inverter ( 6)-( 11) on a half of positive output.
Typically, combining ( 12) and ( 13) will result in (14), where M: modulation index for buck inverter and D: modulation index for boost inverter.

The proposed new control structure
Figure 4 shows the new control structure that has been suggested and is based on pulse width modulation.As shown in Figure 5, this control method will result in a switching pattern that can create a five-level output with buck-boost mode.shows the switching patterns used in the AC-AC converter part in buck mode and boost mode, respectively.Q1 and Q2 are always active in buck mode, while Q3 is active only during negative cycles and Q4 is active only during positive cycles as shown in Figures 6(a).In boost mode is shown in Figures 6(b), Q2 and Q4 will be active during the positive cycle, while Q1 and Q3 will be complimentary active at high frequency.The switching pattern performed during the negative cycle is the opposite of the positive cycle.

RESULTS AND DISCUSSION
A simulation using the power simulator software and laboratory hardware testing are used to verify the proposed new inverter.Table 1 displays the variables that were applied to the verification process during hardware testing and simulation, approximately 100 Watt.The hardware for the proposed inverter is shown in Figure 7.The STM32F407 type of microcontroller incorporates the intended control scheme.Using the B1212S-1W and TLP250 in the driver part.The power switch, meanwhile, makes use of IRFP250.The five-level inverter component of the first test was examined to determine the switching pattern, as shown in Figure 8.The switches S1-S4 function at high frequency based on sinusoidal pulse width modulation, whereas S5 and S6 operate at low frequency as a zero-crossing detector.The results of simulation and hardware testing are shown in Figures 8(a

CONCLUSION
The proposed new single DC source five-level buck-boost inverter for single phase applications has been demonstrated to be able to operate at five levels and as both a buck and a boost on the output voltage side.The power circuit under study utilizes a novel control structure and the idea of a multilevel inverter, which gives it a wide range of operation in terms of output voltage and makes it ideal for applications involving single phase systems.The experimental inverter proved to be more efficient than the typical inverter.With its wide variety of energy conversion capabilities, this novel inverter topology is highly helpful in new renewable energy applications.

Figure 1 .
Figure 1.Proposed new five-level buck-boost inverter Figure 2(b) shows the direction of current flow in operating mode 2. The mathematical equation for operation mode 2 is presented in (2).Int J Pow Elec & Dri Syst ISSN: 2088-8694  A new single DC source five-level buck-boost inverter for single phase … (Leonardus Heru Pratomo)

A
new single DC source five-level buck-boost inverter for single phase … (Leonardus HeruPratomo)

Figure 4 .
Figure 4.The new algorithm control structure

Table 1 .
Simulation parameters and prototype implementation A new single DC source five-level buck-boost inverter for single phase … (Leonardus HeruPratomo)341