KR20200095952A - Voltage regulator of self-excited type permanent magnet synchronous generator - Google Patents

Abstract

According to an embodiment of the present invention, provided is a voltage regulator of a permanent magnet synchronous generator which can supply fixed voltage and fixed frequency power without a constant voltage constant frequency (CVCF). The voltage regulator of a permanent magnet synchronous generator comprises: 1) a voltage regulator consisting of a voltage detection unit which detects a voltage outputted from a three-phase self-excited permanent magnet synchronous generator and a control unit which sends a signal to a voltage controller in accordance with the detected voltage to regulate the output voltage; 2) a voltage controller composed of a power control element connected in parallel to an output terminal and capable of connecting or disconnecting an output of the generator with a capacitor in accordance with the signal commanded by the control unit; and 3) a capacitor connected in parallel with the generator output through the voltage controller.

Description

Voltage regulator of self-excited permanent magnet synchronous generator {VOLTAGE REGULATOR OF SELF-EXCITED TYPE PERMANENT MAGNET SYNCHRONOUS GENERATOR}

The present invention relates to a voltage regulating device of a self-excited permanent magnet synchronous generator, and more particularly, in a three-phase synchronous generator using a permanent magnet as a field, it is possible to adjust the voltage output from the generator without configuring a winding on the field. It relates to a device that is there.

If the generator is divided according to the excitation method, it can be divided into a self-excitation generator and a self-excitation generator. The former is a method of creating magnetic flux by using an electromagnet by winding a winding around a field, while the latter is different in that it creates a magnetic flux using a permanent magnet instead of an electromagnet. However, in the case of the other excitation type, the magnetic flux density can be increased or decreased by adjusting the voltage applied to the coil. However, in the case of using a permanent magnet, the magnetic flux density is fixed, so the magnetic flux density cannot be adjusted without additional means. Therefore, in the case of the other excitation type generator, since the voltage can be adjusted, a power generation system that maintains a constant output voltage by adjusting the magnetic flux density of the field according to load fluctuations while maintaining a constant frequency by maintaining a fixed speed of the prime mover driving the generator. Mainly used for On the other hand, in the case of a self-excited generator, since there is no function to adjust the voltage according to the load fluctuation, the speed of the prime mover driving the generator is fixed by applying a constant voltage constant frequency supply device (Constant Voltage Constant Frequency, hereinafter referred to as CVCF). Even if it is not maintained, constant voltage and constant frequency power can be output.

The other excitation type generator needs an exciter and a rectifier for excitation, and the coil must be wound around the field. Therefore, in the case of a rotating field method in which the field is connected to the prime mover and rotates, the coil is deformed by centrifugal force, causing rotational imbalance, etc. Due to this, high-speed rotation is difficult and manufacturing of the rotor is also difficult. In addition, there is a method to control the power generation voltage by winding a coil around a permanent magnet and controlling the magnetic flux by an electromagnet in addition to the basic magnetic flux of the permanent magnet, but this is basically the purpose of increasing the efficiency by adding a permanent magnet to the field of the other excitation method. Because of this, it has the characteristics and limitations of other excitation methods.

On the other hand, even in the prior art in which a CVCF is connected to a self-excited permanent magnet synchronous generator, there is a problem that it is difficult to increase the ratio of the maximum rotation speed to the minimum rotation speed of the prime mover during power generation. To explain this, a brief example of a general CVCF configuration and operation principle is as follows. CVCF is largely an AC-DC converter unit composed of power control elements such as DIODE or SCR and GTO to convert the alternating current made by the generator into direct current, a capacitor unit to smoothly store the converted direct current electricity, and converts direct current to alternating current again. However, it is composed of a DC-AC inverter unit consisting of power control elements such as IGBTs that control voltage and frequency through power switching. The voltage control method of CVCF is largely divided into methods such as PAM, PWM, and PPM, and all three methods have in common that a power control device must be used, and therefore, the voltage that can be applied to the CVCF must have a limited range. This is because the allowable range of the input voltage of the power control device constituting the CVCF is not so large.

The reason why it is difficult to increase the ratio of the maximum rotational speed to the minimum rotational speed of the prime mover during power generation in the prior art is as follows. For example, there is a self-excited permanent magnet synchronous generator that is attached to a vehicle engine and must be operated regardless of the driving state of the vehicle, i.e., stop, low speed, high speed, etc., and the engine is at least 800 RPM while the vehicle is stopped It can be rotated at a maximum of 4000RPM in the state of being, and it can be assumed that a power generation system composed of a generator and CVCF should output rated power at a voltage of 220V even at the lowest engine speed. Considering that the voltage of the self-excited permanent magnet synchronous generator is proportional to the number of revolutions, and the CVCF inverter output voltage cannot be higher than the inverter input voltage, the output at the minimum engine speed of 800 RPM of a general self-excited permanent magnet synchronous generator Assuming that the voltage is approximately 200V, the maximum rotational speed of 4000RPM varies depending on the generator configuration, but a high voltage of approximately 1000V is output from the generator to the CVCF.

In addition, in the case of 3-phase AC output from the generator, the voltage increases by twice the root while passing through the AC-DC converter, so the voltage applied to the DC-AC inverter at the highest engine speed reaches about 1400V. In addition, since the voltage can be increased up to 1.5 times or more due to the back electromotive force that can occur instantaneously during the CVCF internal power switching process, the power control device must have a withstand voltage of at least 2100V in consideration of the safety factor. As a result, in order to stably output 220V, which is a relatively low voltage, regardless of the engine rotation speed, the power control device should be selected as a device with about 2100V withstand voltage.

In the case of IGBTs among power control devices on the market, for example, the highest withstand voltage is divided into 600V class, 1200V class, 1700V class, and 3300V class based on the maximum withstand voltage, and the price increases sharply as the withstand voltage increases. If the ratio of the maximum rotational speed to the minimum rotational speed of the prime mover is small, a 600V class IGBT can also be applied to stably output 220V power from the CVCF, but as in the example above, the maximum rotational speed compared to the minimum rotational speed of the prime mover When the ratio of is large, for 220V output, 1700V or 3300V class IGBT should be used.Even if the 1700V class IGBT is used without considering the safety factor, low voltage electricity is mainly used in the low engine speed range for actual use. Because switching must be performed using a high-voltage device, the power conversion efficiency is lowered, and there is a problem in that the cost is greatly increased because the IGBT, which occupies the largest cost share among CVCF components, must be used for expensive high voltage.

An object of the present invention is to provide a voltage regulating device capable of controlling the voltage output from a self-excited permanent magnet synchronous generator within a certain range or constant by a simple method.

A voltage regulating device for a permanent magnet synchronous generator according to an embodiment of the present invention includes: 1) a voltage detector that detects a voltage output from a three-phase self-excited permanent magnet synchronous generator, and sends a signal to a voltage controller according to the detected voltage to output A voltage regulator consisting of a control unit that regulates voltage, 2) a voltage controller consisting of a power control element connected in parallel to the output terminal and capable of connecting or disconnecting the output of the generator with a capacitor according to a signal commanded by the control unit, 3) the voltage It includes a capacitor connected in parallel with the generator output through the controller.

According to an embodiment of the present invention, since the ratio of the maximum rotational speed to the minimum rotational speed of the prime mover driving the generator is large, it is difficult to operate a self-excited permanent magnet generator in the past, such as a self-excited permanent magnet generator in a prime mover such as a vehicle engine. CVCF can be used by applying and the withstand voltage of CVCF applied together can be kept relatively low, so the safety of CVCF can be secured. In addition, CVCF manufacturing cost is reduced by using a power control device that is a component of CVCF with a relatively low withstand voltage. Can be lowered. In addition, even in the case of a generator operated with a fixed rotational speed of the prime mover, if the power on the load side is used within a certain range, it can supply a fixed-voltage, fixed-frequency power without CVCF.

1 is a block diagram of a voltage regulating device of a permanent magnet synchronous generator according to an embodiment of the present invention.
2 is a block diagram of a voltage regulating device of a permanent magnet synchronous generator according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily practice. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

First, a brief description of the configuration and characteristics of a self-excited permanent magnet synchronous generator is as follows. Magnet-excited permanent magnet synchronous generators are largely composed of permanent magnets in the rotor to act as a field, and a stator formed by winding a coil on a laminated electrical steel sheet acts as an armature, and a fixed field and rotating It is divided into a rotating armature type self-excited permanent magnet synchronous generator composed of armatures. In the present invention, the description is based on a generally widely used rotating system type self-excited permanent magnet synchronous generator, and the principle can be applied in the same manner.

Looking at the characteristics of the voltage and current of the generator, the voltage curve produced by the generator corresponds to the change in the position of the field pole, and the current curve is determined according to the size of the load applied to the output terminal, and the phase of the current changes according to the type of load. do. These types of loads can be largely divided into resistive loads, inductive loads, capacitive loads, etc., and each causes phase difference in phase, ground, and phase currents. On the other hand, when the load applied to the output terminal increases, the load current in the armature winding increases, and when a current flows in the armature winding, the magnetic flux generated by the armature current affects the main magnetic flux emitted from the permanent magnet field. It leads to a change in the magnetic flux density, and as a result, the organic electromotive force increases or decreases, leading to an increase or decrease in the generator output voltage and current. That is, the output voltage of the synchronous generator is determined according to the total magnetic flux density in the air gap located between the armature and the field, and the magnetic flux density in the air gap when loaded is determined including the magnetic force of the armature as well as the magnetic force of the field.

However, as described above, the biggest disadvantage of the self-excited permanent magnet synchronous generator is that the magnetic flux density of the field cannot be adjusted, and there is a limit to the application of the power control element even when the generator output voltage is accepted by the CVCF. In the present invention, in order to solve this problem, a capacitor and a voltage controller for controlling power flowing through the capacitor are applied to adjust the voltage output from the generator, which will be described in more detail as follows.

Compared to other excitation generators that can increase the magnetic force of the field by adjusting the exciter voltage, the self-excited permanent magnet generator is fixed while the magnetic force of the permanent magnet is magnetized to the maximum value. Therefore, since the magnetic force of the field among the elements that can control the output voltage of the synchronous generator is fixed at the maximum value, the magnetic force of the armature must be adjusted to control the output voltage. As described above, the magnetomagnetic force of the armature is generated by the current flowing through the armature coil, and the magnetic flux density in the air gap can be increased or decreased by adjusting the phase difference of the current generated by the current.

In order to adjust the phase difference of the current flowing through the armature, a capacitor, which is a capacitive load that does not consume power, is used among load elements that use the power of the generator. As described above, as the capacitive load is increased, the current flowing through the generator armature becomes a leading current and the phase increases. On the other hand, the load connected to the output terminal of the generator may contain several types of loads, and the specific gravity of each type of load used may also change according to the power consumption behavior. If the capacitor, which is a capacitive load, is connected in parallel to the output terminal of the generator and adjusted by connecting or disconnecting the voltage, it affects the phase of the current flowing through the generator armature and increases or decreases the pore magnetic flux density due to the armature reaction. It can lead to an increase or decrease in voltage.

Therefore, based on the maximum rotational speed of the prime mover connected to the generator, the voltage output when the connection to the capacitor is disconnected does not exceed the maximum voltage required from the load side, and the connection to the capacitor is maximized based on the minimum rotational speed of the prime mover. The generator is designed so that the voltage output from the generator exceeds the minimum voltage required on the load side, but the capacity of the capacitor is set in consideration of the capacity of various types of loads that can be applied to the generator load side. If a power control element is installed between the flow of power to be controlled, the generator output voltage can be controlled.

Referring to FIG. 1, a configuration and operation of a voltage regulating device of a self-excited permanent magnet synchronous generator according to a first embodiment of the present invention will be described as follows. Although not shown, when power is produced in a three-phase self-excited permanent magnet synchronous generator connected to a prime mover having a variable rotational speed, a voltage output from a voltage detector of a voltage regulator connected to the generator output terminal is measured. If the measured voltage is lower than the minimum voltage required by the CVCF connected to the output terminal, the control unit of the voltage regulator instructs the voltage controller connected in parallel to the generator output terminal to connect the generator output voltage to the capacitor, and the power control element configured inside the voltage controller Connect the voltage of the generator to the capacitor. At this time, the power control device may be a device that can be used for AC power control such as SCR, TRAIC, GOT. The phase of the current flowing through the armature of the generator by the voltage connected by the capacitor increases, thereby increasing the pore magnetic flux density, and when the organic electromotive force increases accordingly, the voltage output from the generator increases. When the voltage measured by the voltage regulator voltage detector exceeds the minimum voltage required by CVCF and a certain level of voltage margin is secured according to the preset logic, the control unit of the voltage regulator instructs the voltage controller to disconnect the generator and the capacitor. The output voltage is maintained within a certain range. Since the voltage maintained within the preset range is connected to the CVCF, it is not necessary to apply a power control device for high voltage, and a power control device with an appropriate withstand voltage that does not cause a large deviation in proportion to the output voltage can be applied.

Referring to FIG. 2, in the voltage regulating device of the permanent magnet synchronous generator according to the second embodiment of the present invention, the number of revolutions of the prime mover driving the generator is kept fixed rather than variable, so that the output frequency of the generator is constant. It differs from the first embodiment in that it is configured to be able to adjust the output voltage in the same manner as in the embodiment, so that power of a constant voltage and constant frequency can be supplied without passing through the CVCF.

If the number of revolutions of the prime mover can be kept constant, like other excitation generators, it is possible to output constant frequency power without a separate device. If the prime mover keeps the rotational speed of the generator constant, the voltage fluctuates according to the load. As the load increases, the voltage decreases, and when the load decreases, the voltage increases. Therefore, also in this case, it is possible to adjust the phase of the current using the capacitor in the same manner as in the first embodiment, thereby increasing or decreasing the voltage. However, the minimum value of the output applied to the load may be limited.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims and detailed description of the invention and the accompanying drawings. It is natural to fall within the scope of.

Claims (1)

A voltage regulator including a voltage detector for detecting a voltage output from the three-phase self-excited permanent magnet synchronous generator, and a controller for controlling the output voltage by sending a signal to the voltage controller according to the detected voltage;
A voltage controller connected in parallel to the output terminal and including a power control element capable of connecting or disconnecting the output of the generator with a capacitor according to a signal commanded by the controller; And
A voltage regulating device of a self-excited permanent magnet synchronous generator comprising a capacitor connected in parallel with the generator output through the voltage controller.

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