One characteristic factor is the ratio of the time the switch is in position 1, T. This means that the output power is the product of the energy processed in each cycle and the switching frequency.
UNREGULATED REGULATED
CHAPTER 2
The state of the system changes according to the variation of the inputs vg' d and the load. Consider the current nTs at the beginning of the nth cycle when the converter states are x(nTs).
The next step is perturbation and linearization of the model, all performed on the corresponding circuit. The other non-linear part of the system is the modulator, where the disturbances in the control voltage are converted into duty-ratio modulations.
CHAPTER 3
Similarly, u is the input vector for. the converter and ul are the optional reference voltages and reference currents of the loop. The input-to-output and input access transfer functions of the buck converter of Fig.
CHAPTER 4 CONCLUSION
Due to the special nature of the program, it can be implemented on small or even desktop computers. The high accuracy of the initial design reduces the number of cycles of prediction, measurement and refinement and makes the design process much faster.
PART II
AC UNINTERRUPTIBLE POWER SUPPLY
CHAPTER 5 INTRODUCTION
Sometimes the power supply must power the load just long enough to allow orderly shutdown of the various stages of the load (normally in small computer systems). When the power line recovers, various parts of the load return to normal operation according to a preset procedure, while the empty storage medium of the line is charged. In 11forward11 DC-to-AC operation this allows the use of reactive loads where, in some part of the AC cycle, the.
5.2, which relies on the amplifier's four-quadrant ability to allow bidirectional power processing. The battery bank is thus charged from the line, and the level of current flow depends only on the amplitude of the current, as its shape and phase are predetermined. When line current is restored, the control circuit matches the phase and amplitude of the inverter to that of the line.
This alternative UPS reduces the number of power stages in the conventional UPS to one unit, as only one function is required at any time. This is because the input impedance of the amplifier must be shaped to look ~e~L6Ltve at low frequencies.
CHAPTER 6
The output of the converter can be made to produce a full wave rectified sine wave which is 11folded out11 to obtain sine waves at the output. Finally, the push-pull method is introduced, which uses a single voltage source and two current bidirectional de-to-de converters to supply a load that is differentially connected to the converters' outputs. operation is achieved which is capable of driving general loads, including reactive loads. 6.lb illustrates the order of the couplings, which leads to an almost sinusoidal voltage across the load.
It is noticeable that each switch is activated and deactivated only once during each cycle of the output frequency. Also, improving the harmonic content of the output voltage requires a rapid increase in the number of steps and thus the number of switches. Each waveform (_average) can be generated on the output by pulse width modulation of the switch, as shown in Fig.
Usually a low pass filter is placed on the output port of the inverter to preserve the low frequency. The greater the separation between the switching frequency and the modulation frequency, the easier the filter's task.
LOAD I
CHAPTER 7
It also desensitizes the output to changes in input voltage, load, or other system parameters. If the duty ratio of one converter is D, the other converter is po. the complementary nature of the drive receives D'. However, in the case of the differential amplifiers described in Section 6.2, it has potential applications.
However, the main difference is the regular large variation of the operating point versus only occasionally. The only thing left to check is the sensitivity of the loop gain to the operating point. Calculation of the loop gain at a duty ratio of 0.6 (Dmax) shows a phase margin of 56 degrees.
Therefore, all the design steps are correct and the design of the inverter is complete. That is, the power bandwidth of the system is equal to its open-loop bandwidth.
CHAPTER 8
8.1, must then tightly regulate the AC QuJULent of the amplifier to make it follow a reference signal. 2 in the Cuk amplifier corresponds to the parasitic resistances of the two inductors in each converter. So far, the solution for the output current versus various parameters of the amplifier has been found.
As with the converter box, the amplifier must have enough bandwidth to allow large signal variations of the current. Therefore, all the transfer functions of the system's states must be calculated against duty ratio. So, the output impedance is satisfactory at the frequency of the line (up to almost 400 Hz).
Instead of load, AC lines are connected to the amplifier's AC port (now input). The dynamics of the amplifier, due to the effective short circuit (line) on the output, experiences a large change at a.
CHAPTER 9
The return of the current to the amplifier, however, does not have to be instantaneous, and a gradual change in the sign of the reference voltage in the charger mode can be used to solve the problem. The amplifier now has the correct initial conditions for charger mode, and the switching process will occur smoothly since the circuit inductors show no resistance to the instantaneous change in currents (zero current change!). The solution to this case, of course, is to set the correct starting voltage to the integrator of the charger control circuit.
During charger mode, the sine wave generator is phase locked to the line so that the output voltage produced by the combination of the generator and amplifier is exactly in phase with the line. In the worst case, in heavy charging mode, the power cuts out again at the peak of the current (voltage). The direction is reversed from the maximum level in one direction to the peak level in the other direction. The circuit's inductors prevent an instantaneous reversal of current, causing the output voltage to begin to drop.
The initial condition criterion is not met and the transition (in this case) is not smooth and will be dictated by the dynamics of the circuit. friend with the controller preset). If this power bandwidth is increased, the inherent speed of the system will also increase.
CHAPTER 10 CONCLUSION
This limitation is very realistic since high power bandwidth means smaller sizes of storage elements of the amplifier. The behavior of the converter can now be easily characterized by interaction of the two constituent converters of the amplifier with the load. Therefore, the analysis of large-signal variation of the system is approached by a series of small-signal analyzes for which powerful analytical.
It is shown that due to the perfect symmetry of the system, the dynamics of the system at the quiescent operating point can be analyzed by examining only one converter if the correct stationary and other conditions are met. The output impedance of the amplifier is very low at low frequencies, and current feedback is required to convert this open-loop impedance to the desired form. The control parameter is the output current, and the system dynamics undergoes a large change due to the replacement of the load with a voltage source.
It has been shown that with some precautions, at the quiet operating point, the dynamics of the amplifier can be. However, the requirements for equality of initial and final conditions suggest a circuit similar to the charger to pre-set the correct voltages in the compensation network of the inverter.
PART III
A NEW POLYPHASE SWITCHING POWER AMPLIFIER
CHAPTER 11 INTRODUCTION
One of the advantages of AC power distribution comes from the use of multiphase systems. Multiphase operation and transmission allows for significant savings in overall network costs due to the elimination of reverse currents and. Multiphase systems are mostly used in the high power range, and the limitations of power processors are generally dictated by the limitations of power switching devices.
Such extensions became possible by observing the behavior of the de-to-de converters and by appropriate modifications to extend their quacffLan.t capabilities. Again, the de-to-de converters and more advanced single-phase power amplifiers are used as modules of polyphase power processors. The excellent quality of the generated polyphase voltages makes this amplifier suitable for almost all line-related applications.
The drive uses three buck converters and its output is regulated to make it insensitive to variations in the input voltage, load and other parameters of the system. Finally, due to the general nature of the technique, a number of other interesting applications for the polyphase amplifier have also emerged.
CHAPTER 12
In the previous work, it was shown that the push-pull amplifier can be used as a single-phase converter. However, since the outputs of the converters may not be electrically isolated from the input, these connections are generally not possible and would result in uncontrolled currents between the converters. Electrical insulation is provided by the motor windings, which in this case are used separately.
However, the outputs of the converters are all paralleled through the outer loop and, unless prevented by very accurate feedback systems, a large current can be induced between the converters. If two equal voltages are applied to the modulator inputs, the outputs of the two converters will be at the same potential, resulting in zero voltage across the load. Consequently, a pure sine wave can be obtained and the previous push-pull output reproduced (fig. 6.9), but now with an arbitrary quiescent operating point and arbitrary th component.
However, a non-sinusoidal quantity when phase-shifted and subtracted from the original can result in the output changing its shape. the parts are still eliminated. Consider the case where the sine waves are 120° out of phase and the inverter nonlinearities are ignored.
LINE-TO-GROUND AND LINE-TO-LINE VOLTAGES
Note that the de potential present in the line-to-line voltage has automatically disappeared in the line-to-line voltage. However, any difference in de potentials of each phase, VDC' would directly lead to. In fact, in open-loop operation, special care must be taken to ensure that the phase potentials are equal.
Furthermore, its operation is not limited to three-phase systems and can be easily extended to N-phases.
