电力电子负载拓扑控制

A a
b
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Fi g.3 Three phase PEL used in three phase three wire system
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b
B
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Fig.3(b) Tree phase PEL used in three phase four wire system
III.MODELING OF POWER ELECTRONIC LOAD As can be seen from discussion above, single phase PEL is the basic topology. The LIC tracks the current reference by current controller and offers the operation power of the whole system. The GCC is actually a rectifier which operates in recycling mode. It holds the system with high power factor and maintains the DC voltage constantly. With proper current reference and control scheme, the input power factor of the
Research on Power Electronic Load: Topology，
Modeling, and Control
Xu She,student member, IEEE, Yunping Zou, Chengzhi Wang, Lei Lin, Jian Tang, Jian Chen, senior member, IEEE Power Electronic Research Center, Huazhong University of Science and Technology Email: shexu8511211@gmail.com
I. INTRODUCTION The trend of power electronic is cost-effective and energy-efficient because the energy problem is crisis in the modern world. Most of the researches are emphasized on how to improve the efficiency of converter while less attention is paid to the energy consumption of the load. In 1990, Suresh Gupta proposed a method that uses a transformer to adjust the active and reactive power outputted by power source so as to test the equipment [1]. The disadvantages of this idea lies in that it is hard to get an accurate current for testing and it will feed the reactive power to grid. In the middle 1990s, Chu.C.L proposed an idea that uses a PWM rectifier which can run in four quadrants to recycle the energy to the grid [2]. However, an uncontrolled rectifier was adopted in this method, so it can only simulate limited load character. What is more, the DC bus voltage was not stabilized which is harmful to the stability of the whole system. In 2002, Huang.S.J proposed an advanced topology which adopts a controllable AC/DC rectifier as the former-stage converter [3]. Unfortunately, there is no deeply research about the whole system. In 2007, Chengzhi Wang introduced a novel power electronic load (PEL) and proposed a repetitive controller applied in it [4][5], a prototype of power electronic is designed which performs well for both linear load and non-linear load. Repetitive controller performs well when considering about steady state error, however, its dynamic performance is not good. In this paper, topology for three-phase AC PEL, singlephase AC PEL, and DC PEL are given for the first time. Then, a novel improved repetitive controller which composed of traditional repetitive controller paralleled with PI controller is proposed to improve the dynamic response of the system. Furthermore, when considering about the stability of DC
Bus voltage, a mean filter is adopted to eliminate the harmonics in DC voltage loop. Lastly, the efficiency diagram is given to show that this equipment can save as much as 80%-90% energy compared with traditional load. The topology and relative control method are verified with simulation and experiments.
B. Topology of DC PEL
Based on the basic topology of PEL, if S and S are off
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and S is on for all the time. When control switch S , the
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LIC is a boost converter and the system can be used as a DC PEL, as seen in Fig.2.
r L S11
1 1 i1
u1 S12
D11 S13 a1
D12 S14
idc1 idc2
D13
idc_c udc + S21
D21 a2
b1 C - S22
S23
D23 L2 r2 is T
i2 b2
us
D14
D22 S24
D24
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Fig.1 Basic topology of PEL
Due to the advantage of controllable quality of input current of the PWM rectifier, the phase difference between the output voltage of tested power source and input current of LIC can be various. Thus it can simulate characteristic of any load. Besides, this PWM converter can work both in the state of rectifier and inverter, GCC can feed the energy back in to the grid to realize the goal of energy feedback.
be tested under certain condition, for example, working with unbalanced load. Based on this basic topology, three-phase PEL which can be applied either in both three-phase threewire system or three-phase four-wire system can be composed as seen in Fig.3(a) and Fig.3(b). Because the system has been decoupled into single phase system, it can be controlled separately.
Abstract-A novel power electronic load (PEL) is introduced in this paper. This equipment can simulate R,L,C load as well as non-linear load. Furthermore, it can recycle the energy back to grid. Topology for single phase AC PEL, three-phase AC PEL, and DC PEL are presented firstly. Based on disadvantages of repetitive controller, an improved repetitive controller is presented to improve the dynamic performance of the system. Relative problems in back to back system are analyzed and mean filter is adopted to eliminate the harmonics in DC loop. The whole efficiency can be as high as 80%-90%. Simulation and experimental results are carried out to validate the effectiveness of the proposed control strategy.
II.TOPOLOGY OF POWER ELECTRONIC LOAD
A. Basic topology Fig.1 gives the basic topology of PEL which is used as a
single phase PEL. It is composed of five parts: 1. Tested power source 2. Load Imitation Converter(LIC) 3. DC bus capacitor 4. Grid Connected Converter(GCC) 5. Grid
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DC
udc_t
S12
idc1 idc2
idc _ c udc + S21
C - S22
D21 a2
S23
D23 L2 is
i2 b2
u2
D22 S24
D24
Fig.2 Topology of DC PEL
C. Topology of ห้องสมุดไป่ตู้hree phase PEL In many application areas, three-phase power source has to