The Signal Processing and Application of Intelligent Power Module in Power Inverter for Switched

Reluctance Drive

Aide Xu,Yinhai Fan Hongyong Yu Department of Information Scientific Technology Department of Automation

Dalian Maritime University Jinan Institute of Railway TechnologyDalian, China Jinan, China

Abstract—This paper is to set forth the feasibility of applying Intelligent Power Module(IPM) to the Power Inverter of Switched Reluctance Drive(SRD) by analysing the characteristics of IPM. According to the characteristics of 5.5KW 12/8 pole Power Inverter of SRM, and on the basis of the research of Power Inverter composed of discrete elements, we proved by way of theoretic analysis, PSPICE simulation and practical test that Power Inverter with IPM not only can perform its function very well, but also has the merits of high reliability, strong anti-interference ability, and etc.

Keywords- Intelligent Power Module .Switched Reluctance Drive . Power Inverter . PSPICE Simulation.

Ⅰ. INTRODUCTION Power Inverter plays a significant role in the production

costs of entire system. It is the energy supplier of Switched Reluctance Motor(SRM) during the process of its running . To improve the performance of the system and at the same time reduce the price, rational selection and design of power inverter is one of the most important key factors. The selection of power inverter shall meet some basic requirements, such as structural matching, high efficiency, easy control, simple structure, low production cost, and etc [1].

IPM not only integrates the power switch IGBT and its drive circuit, but also has the function of protection from short circuit, out of current, under-voltage and over-heat of the module, and at the same time it can send the tested signal to processor. It is composed of high speed and low cost tube, optimized gate drive circuit and quick protection circuit. Even if being overload or misused, the IPM itself can be safely protected [2].

This paper, took the research process of 5.5KW 12/8 pole Switched Reluctance Drive as an example, mainly introduced the application of IPM in power inverter circuit of the system.

Ⅱ. POWER INVERTER FOR SRD WITH DISCRETE PARTS According to the characteristics of 5.5KW 12/8 pole SRM,

asymmetrical half-bridge three-phase SRD power inverter circuit was adopted in the purpose of simplifying the control

system. As is showed in Fig. 1, the main switch device adopts Insulated Gate Bipolar Transistor（IGBT）T1～T6, while continuous current diode D1~D6 adopts the free-wheeling diodes (FWD).

Fig.1 Power Inverter for SRD with discrete parts

Fig.2 The waveform for one phase

The principle of working process is as follows. The upper bridge switch T1 and the lower bridge switch T4 are drived simultaneously, wind A is in working condition, and then the upper bridge switch T1 is turned off according to the requirement of limiting current, wind current will flow through the lower bridge switch T4 and the FWD D4. While the upper and lower bridge switches are both turned off, the current will continue flowing through D1 and D4. The working process of

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wind B and wind C are similar to wind A. We can observe the current waveform of one of the three phases through oscillograph which is showed in Fig. 2 [3].

From the above described working process, we can know that the reliable turning on or turning off of switch is the basis of normal working of power inverter. In experiment , we adopted integrated drive module EXB841 as drive part of switch. At the same time we design protection circuit such as over-current ,over-voltage and etc.The actual drive circuit and main circuit are demonstrated in Fig 3 [4].

(1) EXB841 drive board

Judging from above analysis, we can draw a conclusion

that although the function of main circuit can be realized with discrete parts, too big volume of this system, the low reliability and the weak anti-interference ability altogether make it difficult to develop product. In order to improve the efficiency of the power converter and avoid the negative influence from separate parts, IPM is adopted to accomplish the function of switch components and drive circuit.

(2) IGBT main circuit

Fig.3 The actual circuit with discrete parts

Ⅲ. CHARACTERISTICS OF IPM The main title (on the first page) should begin 1-3/8 inches

(3.49 cm) from the top edge of the page, centered, and in Times 14-point, boldface type. Capitalize the first letter of nouns, pronouns, verbs, adjectives, and adverbs; do not capitalize articles, coordinate conjunctions, or prepositions (unless the title begins with such a word). Leave two 12-point blank lines after the title.

According to the structural Characteristics of the power inverter discussed above, PM75RLA060 is adopted, its inner schematic circuit and outer package are showed in Fig 4 and Fig 5.

Fig. 4 The inner schematic of IPM

Fig. 5 The outer package of IPM

Compared with power inverter with discrete elements, the characteristics of IPM are as follows.

・ Temperature protection provided by directly detecting the junction temperature of the IGBTS.

・ Low power loss and soft switching.

・ High performance and high reliability IGBT with overheating protection.

・ Higher reliability because of a big decrease in number of parts in built-in control circuit.

A. The drive circuit is built-in. ・ IGBT is drived under optimum condition.

・ Short connecting line between drive circuit and IGBT, low impedance and bias voltage source is not required.

B. Protection circuit is built-in. The inner circuit of IPM module is divided into two parts,

one is power part which consists of IGBT and FWD, the other is control part which is made up of many pieces of IC. The control part can offer functions like drive of IGBT, and the protection from short circuit, out of current, under-voltage of controlled power and over-heat of the module, and at the same time it can send the tested signal to processor.

・ Overcurrent protection(OC)

It can perform the overcurrent protection through detecting the collector current. Once the time of overcurrent exceeds the allowable valve, which is about 6～8us, a soft shutdown will happen. Because there is a delay of 6～8us, it can not mis-operate for momentary overcurrent and noise.

・ Short-circuit protection (SC)

When the overcurrent protection operates, the short-circuit protection will operate together to restrain the amplitude current for load short or upper-lower arm short. Because the current detect unit is built into the IPM, it needn’t add detect part in addition.

・ Under-voltage protection of controlled power(UV)

When the control power voltage drops to the lower limit, there will be a soft shut-down on IGBT and give an alarm once the input signal is on. When the Vcc recover to the upper limit, the alarm will be relieved.

・ Overheating protection for case and chip (OH)

The temperature detected parts which are built together with IGBT and FWD can detect the temperature of base board and IGBT. The over-heating protection will operate once the detected temperature exceeds the limit temperature for one milli-minutes, with IGBT turned off and working no more after two milli-minutes.

・ ALM function transmits alarm signal. While OH、OC、SC、UV are under protecting operation, it can transmit alarm signal to the computer that controls IPM, so that the system will stop working.[2]

Ⅳ. THE FEASIBILITY ANALYSIS OF POWER INVERTER WITH IPM

A．Theoretical Analysis According to the connecting condition of IGBT and FWD

in IPM, the design of main circuit of SRD is showed in Fig 6.

As can be seen from Fig 6, wind A is connected between U and V , wind B between V and W, and wind C between W and U. Meanwhile, in order to avoid another two winds mis-turned on while one wind is turned on, one FWD is series-wound on each one of the three winds. For example, when wind A is turned on, if there is not series FWD, current will flow through wind B and wind C, which is not permitted. As shown in Fig 7, take wind A as an example, the working process is showed

in Fig 8. When T1 and T5 is turned on, current flows through wind A, and when T1 is turned off, current of wind A continue flow through T5 and D4. If T5 is also turned off, current continue flow through D2 and D4. However, it is proved in experiment, current of wind A still can flow through wind B and wind C which will be harmful to the operation of motor. Therefore, in order to control this consequence, before the wind B is turned on, the turned on time of lower bridge switch of wind A should be extended, so as to prolong the time of flowing current through D4 and T5. Nevertheless, to avoid short circuit, ensure that T5 is turned off properly before the turned on of wind B. [5]

Fig. 6 Power Inverter for SRD with IPM

Fig.7 The sketch map of mis-turned on

Fig.8 The sketch map of flowing current for change phase

Therefore, a conclusion can be drew from all that we have discussed above that all the functions of power inverter

composed of discrete parts can be realized by way of adopting IPM and adding three additional FWD. However, much attention should be paid to the special requirement of drive control[6][7].

B. Pspice simulation In order to get further confirmation of the reliability of

circuit, we conducted an overall simulation by PSPICE software. The simulation circuit is showed in Fig 9. The on and off time of IGBT is achieved by setting switch parameter, see TABLE 1. Adding a pulse drive to the upper bridge switch of wind A, we can see the process of current chopping. Of course, because of different setting current, we can get different current chopping .Just for this, we can realize the timing.

Fig. 9 Simulation schematic

As can be seen from Fig 10, the current waveform of three phase winds is identically in accordance with theoretical analysis [8].

Fig. 10 Simulation waveform

TABLEⅠ

ON AND OFF TIME SETTING OF SWITCHES

Phase time

A up

A down

B up

B down

C up

C down

On time(ms) 0 0 4 4 8 8

Off time(ms) 3 4 6 8 10 12

C. Practical Test The practical circuit with IPM is showed in Fig 11, from

which we can see that three FWD were connected in the circuit. Compared with the circuit with discrete parts, it becomes simpler than before.

As can be seen from Fig 12 that the waveform of one wind is identically in accordance with the result used discrete parts. Of course it is also in accordance with the theoretic analysis.

Fig .11 Power inverter with IPM

Fig .12 One phase waveform with IPM

Ⅴ. CONCLUSION By the comparison of theoretical analysis, PSPICE

simulation, practical test and their waveform, we can safely draw a conclusion that adopting the IPM with three fast recovery diodes as the main circuit can not only realize the function of power inverter using separate parts, but also finish all kinds of protection which will considerably increase its reliability. On the other hand, we can also reduce its volume greatly, enhance the anti-interference ability, and lowered the cost, therefore, deserve to be popularized.

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Beijing,Machine industry publisher, 2000. [2] Applied technique data of IPM. Mitsubishi electrical engineering Inc. [3] Wang Honghua, The control technology of switched reluctance drive,

Beijing,Machine industry publisher, 1995. [4] Zhang Qing. Analyse Of EXB841 which drives IGBT, Electric Drive,

No.4 1994.. [5] Pollock C,et al ,Power converter circuits for switched reluctance motor

with the minimum number of switches . IEE Proc, 137 (6) :373238,1990.

[6] M.Bames,C.Pollock, Power electronic converters for Switched Reluctance Drives,IEEE Transactions on Power Electronics, vol. 13, no. 6, November 1998.

[7] M. Hiller, R. Murquardt,Performance enhancement of Switched Reluctance Drives by a new converter, Concept EPE ‘03, Toulouse, France, 2003.

[8] Zheng Guangqin, OrCAD Pspice A/D V9, China railway publisher,2000