There is no winding on the rotor of the switched reluctance motor (SRM), and the stator is concentrated on the winding. Its structure is simple, sturdy, and reliable, so it has gradually received widespread attention. In fact, Taylor proposed SRM as early as 1839, but after a long time it was almost unattractive. The main reason was that the SRM power converter was almost impossible to achieve at that time. In the past two or three decades, with the rapid development of power electronic devices, MCUs, and DSPs, power converters and controllers have also developed.

The SRM system is a typical mechatronic system, and its power converter and controller are inseparable. In the whole system, the proportion of the cost in the power converter is very large, and the SRM operating current voltage is not a sine wave, but is controlled by the system operating conditions and motor design parameters, it is difficult to accurately predict, these make the power converter design And the choice of switching devices is extremely important and complex.

This article mainly introduces various types of topology and applicable occasions of power converters, and also briefly introduces the performance of power conversion devices and their selection principles.

2 power converter design requirements () try to use the minimum number of switching devices; the best power converter is suitable for both even and odd phases; the main switching device voltage rating and the motor is close; has a rapid increase in phase winding current Ability; () can modulate, control the phase current through the switch device; (6) When the flux chain is reduced, can return the energy, try hard to improve the efficiency.

Of course, these requirements cannot be viewed in isolation. For example, in the case of high voltage and high power, if we only emphasize the use of the minimum number of switching devices, it is bound to increase the voltage of the switching devices, which may reduce the reliability of the system and increase the cost. Therefore, designing power converters should consider factors such as performance and cost.

3 The main circuit topology of various power converters 3.1 The half-bridge half-bridge power converter has flexible control modes, and there are many improvements. However, the total number of components is high and the cost is high.

Among the power converters of switched reluctance motors, the most flexible and most widely used is the asymmetric bridge converter shown in (a).

Each phase requires two switch tubes T1, T2 and two diodes D1, and simultaneously, phi feeds back the energy through D1 and D2. It is because of the energy feedback that this converter is very efficient. And if there are two situations of the same work, due to the independent structure of each phase, it does not affect each other. However, the number of required components is large, so the cost is high, and they are mainly used in high voltage, high power, and few phases.

In order to maintain the excellent performance of the asymmetrical bridge converter, and reduce the components as much as possible, a number of topological structures emerge. As in (b), the two phases use switches T3 and T4 in addition to the switches T1 and T2 for each phase to reduce the number of switches, but there are three switches in the loop of each phase, which increases the loss and reduces the voltage. Utilization rate. () Improvements to this problem introduced in La can be changed to damping resistors or chopping mode current limiting.

(b) A capacitor Cb1 is added on the basis of the asymmetrical half-bridge to allow Cb1 to store energy, which can increase the speed of current rise when the next phase is turned on. () is the improvement of (b), Cb2 is much lower than the voltage on Cb1 so you can choose the cheaper capacitor. Pul 3.2 capacitive energy storage device uses a series ((a)) or parallel capacitor ((b)) through a Buck (buck) DC-DC converter consisting of Cb, Ta, Da and La. Return energy to the DC bus. Cb is an additional energy storage capacitor. Some of these converters are also referred to as converters containing DC-DC circuits. In this way, energy is transferred from the additional capacitor Cb to the next winding, which ensures that the capacitor is not overcharged or overcharged, and that the shutdown voltage can be precisely controlled. The disadvantage is that the number of components increases and the control is more difficult. Moreover, the design requirements of the device reach the high frequency (tens of k or more) of the DC-DC converter, and only work when the motor winding is turned on or off, resulting in a certain waste. .

3.3 Inductive Energy Storage The two windings ph1a, ph1b are coupled to each other, and the auxiliary winding phlb serves to feed back the energy stored in the magnetic core to the DC. The biggest benefit of doing so is to increase the frequency. However, the auxiliary winding cannot be completely linked, so an additional buffer circuit is needed, and the production of the motor is more complicated (need special windings). The addition of the auxiliary winding also increases the volume of the winding and reduces the utility of the unit volume of copper.

3.4 Energy consumption The residual energy stored in the winding is not fed back, but is consumed. The benefit of doing so is to reduce the number of components, making the structure and control easier. However, this reduces the efficiency, and the heating of the energy-consuming resistors requires attention. This method is mostly used in low-power applications where the efficiency requirement is not high but the cost is low. (a) Apply a simple resistor R to absorb the remaining energy in the energy ph. (b) Dissipate the energy in the ph to the regulator diode D1. After T1 is disconnected, ph1 resonates to charge Cb, after which Ta closes, Cb and Lb resonate, Dr2 blocks reverse charging, and Lb finally returns energy to the power source through Vs. 3.6 Comparison of various types of power converters Table 1 shows various types of power. Comparison of inverters, the numbers in the table are all m types of switches number of diodes number of applicable phase number supply voltage utilization whether there is energy feedback can quickly increase the open current half-bridge type.

3Vt cannot. The cmm even number Vs-3Vt cannot. 2mm+1 even Vs/2-Vt has energy storage capacitor type. A2m odd-even Vs+Vt has inductive energy storage type mm parity Vs-Vt has energy consumption type. Amm parity Vs-Vt can not. The bmm parity Vs-Vt-Vd cannot be resonated. There is a power of multiple of amm3 (Vs-V)/2. The multiple of bmm4 Vs-Vt cannot. The cm+1m+2 parity Vs-2Vt can not compare the power converter of Table 1 Table 4 The main switching device SRM system in the power converter According to different output characteristics, the current waveform is different and the high-performance speed regulation characteristics, to the power conversion The device also proposes more stringent requirements relative to the induction motor drive system. Reasonable choices related to motor power class, supply voltage, peak current, cost, etc., and also the switching speed of the main switching device itself, difficulty in triggering, switching loss, impact resistance, durability, ease of operation in parallel, peak value The current rated rms (or average) ratio of the current rating and the extent of market penetration. The following are the main features and applications of several major application switching devices. Micromotor, 2(1) 0 University of Electrical Automation, is currently a graduate student in the Institute of Electrical Engineering of South China University of Technology, majoring in power electronics and electrical transmission. The research direction is the control of switched reluctance motors.

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