Laddered Multilevel DCAC Inverters used in Solar Panel Energ

级联式的逆变思想

Laddered Multilevel DC/AC Inverters used in Solar Panel Energy Systemspresented by

Prof. Fang Lin Luo(Doctor of Camb. U) Nanyang Technological University, Singapore

级联式的逆变思想

AbstractMultilevel DC/AC Inverters have various structures. They have many advantages. Unfortunately, most existing inverters content too many components (batteries, diodes, Capacitors and switches). We introduce the "Laddered Multilevel DC/AC Inverters” in this speech that is a new approach of the development in this area. Their simple structure and clear operation are obviously different from the existing inverters. Its application in Solar Panel Energy Systems is successful. The simulation and experimental results strongly support our design. We believe that these inverters will draw much attention over the world, and be applied in other renewable energy

级联式的逆变思想

IntroductionMultilevel DC/AC Inverters have various structures. The existing inverters can be summarized and shown in Figure 1.

Figure 1. Family tree of multilevel DC/AC inverters

级联式的逆变思想

With comparison with PWM DC/AC Inverters, multilevel DC/AC Inverters have the advantages (1) the switching flying voltage is low (from one level to next level); (2) the di/dt and dv/dt is low; (3) The switching frequency is low; (4) THD is better. Unfortunately, most existing inverters content too many components (independent/floating batteries/sources, diodes, Capacitors and switches). For example, a diode-clamped inverter, also called the neutral-point clamped (NPC) inverter has n = (2b +1) levels and needs the components are [1 – 3]: 4b switches, 2b capacitors. (4b - 2) diodes

级联式的逆变思想

Another, a linear H-Bridged inverter has n = (2b +1) levels and needs the components are [4 -8]: b floating batteries, 4b switches, 4b diodes, where n is the level number that is always an odd number, b is the stage number (from the neutral point to the top point) or bridge number. Figure 2 shows the example: 5-level NPC inverter and three-bridge inverter.

级联式的逆变思想

(a) 5-level NPC inverter (b) threebridge inverter Figure 2. Example inverters

级联式的逆变思想

From Figure 2, we can see that a 5-level NPC inverter has contented a 4E battery (or 2 x 2E batteries), 8 switches, 14 diodes and 4 capacitors; a 7-level linear three-bridge inverter has contented three floating batteries (Vdc1 = Vdc2 = Vdc3 = E), 12 diodes and 12 switches.We introduce few new circuits of multilevel DC/AC Inverters in this paper that are different from the existing multilevel DC/AC Inverters. We call them Laddered Multilevel DC/AC Inverters. Their structure is simple, and its operation is clear that is new approach of the development in the DC/AC inverter area.

级联式的逆变思想

Progressions (Series)In Mathematics, a progression is a series of numbers or quantities in which there is always the same relation between each quantity and the one succeeding it. We introduce several progressions in this section. We assume all progressions have the value of their first item V1 is 1, the value of the general item

i is Vi.

级联式的逆变思想

A: Arithmetical ProgressionsArithmetical progressions are general series. We usually see them as: Unit progression; Natural number progression; Odd number progression.

级联式的逆变思想

All arithmetical progressions have the same deference value between the adjacent two items. We define the value of the first item is V1, the value of the general item is Vi, and the deference is d. therefore, the value of the general item Vi is,

V i V1 i 1) d

(1)

The sum of the items from the first item to ith i ( i 1) item is Si,

S i iV1

d

2

(2)

级联式的逆变思想

(1)The Unit progression is listed in Table 1. We assume the last item is b, and the value is Vb. The general item is item i, and the value is Vi. Since the d is 0, the sum of the items from 1 to the ith item is i.Item Table 1 1. No. Value, Vi. Sum, Si 1 1 2 3 4 Unit Progression 1 2 1 3 1 4 1 i 1 i 1 b 1 b

级联式的逆变思想

(2) The Natural number progression is listed in Table 2. Since the deference d is 1, the sum of the items from 1 toS the thi 1) ii ( i i 2 item isTable 2. Natural Number ProgressionItem No. 11 1

22 3

33 6

44

ii

bbb ( b 1) 2

Value, Vi. Sum, Si

10

i

i ( i 1) 2

b

级联式的逆变思想

(3) The odd-number progression is listed in Table 3. Since the deference d is 2, the 2 sum of the items from 1 to Sthe iith item i is

Table 13. Odd-Number progression i Item 2 3 4 No. Value, Vi. Sum, Si 1 1 3 4 5 9 7 16 2i - 1

b 2b - 1

i

2

b

2

级联式的逆变思想

B: Geometric ProgressionsGeometric progressions are general series. We usually see them as: Binary progression; Trinary progression.

级联式的逆变思想

All geometric progressions have the same proportion between the adjacent two items. We define the proportion is p. therefore, the value of the general item Vi is,V i V1 pi 1

(3)

The sum of the items from the first item to ith item is Si, i p 1 Si V1 p 1 (4)

级联式的逆变思想

(1)The Binary progression is listed in Table 4. Since the proportion p is 2, the sum of the items from 1 to the ith item isTable 1 4. Binary 3Progression Item 2 4 No. Value, Vi. Sum, Si 1 1 2 3 4 7 8 15

i

b

2i-1 2i-1

2b-1 2b-1