JP6727093B2 - Auxiliary power supply - Google Patents

Description

The present invention relates to an auxiliary power supply device that converts a DC voltage supplied from a DC power supply into an AC voltage and supplies the AC voltage to a load circuit.

For an electric vehicle that operates by supplying power from an overhead wire, an auxiliary power supply device that converts a DC voltage (an overhead wire voltage) supplied from the overhead wire into an AC voltage and supplies it to a load circuit such as a cooling/heating device or a lighting device in the electric vehicle. Is mounted (for example, see Patent Document 1).

The auxiliary power supply device is provided with an inverter device to which the DC voltage supplied from the overhead wire is input and which converts the input DC voltage into an AC voltage and outputs the AC voltage. The input side of the inverter device is connected in parallel with a DC filter capacitor for suppressing harmonic current. The input voltage of the inverter device, that is, the overhead wire voltage, is constantly changing (is fluctuating), and the voltage of the DC filter capacitor (hereinafter, referred to as FC voltage) is always changing due to the change of the overhead wire voltage. As shown in FIG. 4, a control circuit for controlling the inverter device normally has a constant voltage (hereinafter, referred to as a constant voltage) within a predetermined period (control period) with respect to an actual FC voltage that constantly changes (is fluctuating). The FC voltage with a filter) is set, and the inverter device is controlled based on the set FC voltage with the filter.

The FC voltage with a filter is usually set based on the following equation (1). In equation (1), x _k represents the actual FC voltage, y _k represents the FC voltage with the filter, y _k−1 represents the FC voltage with the filter one cycle before, τ represents the control cycle, and T ₁ indicates a constant called a filter constant.

As can be seen from the equation (1), the FC voltage with a filter is a value obtained by multiplying the difference between the actual FC voltage and the FC voltage with a filter one cycle before by a value (τ/T ₁ ) according to the filter constant T _1. Is added to the FC voltage with a filter one cycle before. According to the equation (1), the FC voltage with filter can be made to follow the actual FC voltage at a speed corresponding to the filter constant T ₁ . By setting the FC voltage with a filter using such a filter constant T ₁ , it is possible to control the inverter device based on a stable voltage value.

JP, 2015-220890, A

The change in the overhead wire voltage includes a phenomenon called vibration in which the voltage increases and decreases in a small range, and a phenomenon called fluctuation in which the voltage increases and decreases in a larger range than the vibration.

As described above, the FC voltage with a filter follows the actual FC voltage at a speed according to the filter constant T ₁ . In the case of vibration, since the overhead wire voltage, that is, the range in which the FC voltage increases and decreases, the FC voltage with a filter can follow the FC voltage relatively quickly. On the other hand, in the case of a fluctuation, the overhead wire voltage (FC voltage) has a large variation range, so it takes time to follow the FC voltage with filter to the FC voltage, and the difference between the FC voltage with filter and the FC voltage becomes large. The large state lasts for a long time. In such a state, there arises a problem that the output of the auxiliary power supply device becomes unstable.

An object of the present invention is to solve the above-mentioned problems and to provide an auxiliary power supply device capable of stabilizing the output voltage.

In order to solve the above problems, an auxiliary power supply device according to the present invention is an auxiliary power supply device that converts a DC voltage supplied from a DC power supply into an AC voltage and supplies the AC voltage to a load circuit, and is supplied from the DC power supply. An inverter device for converting a DC voltage into an AC voltage, a filter capacitor connected in parallel to the inverter device on the input side of the inverter device, and a FC with a filter so as to follow the FC voltage which is the voltage of the filter capacitor. A control circuit that sets a voltage and controls the inverter device based on the set FC voltage with a filter, wherein the control circuit has a difference between the FC voltage with the filter and the FC voltage within a predetermined range. In the case of, the FC voltage with the filter is made to follow the FC voltage at a speed according to a predetermined filter constant, and when the difference is out of the predetermined range, the FC voltage at that time is Is set as the FC voltage with the filter.

According to the auxiliary power supply device of the present invention, it is possible to stabilize the output voltage.

It is a figure which shows the structure of the auxiliary power supply device which concerns on one Embodiment of this invention. FIG. 3 is a diagram for explaining PWM control by the control circuit shown in FIG. 1. FIG. 3 is a diagram for explaining PWM control by the control circuit shown in FIG. 1. FIG. 3 is a diagram showing an example of setting an FC voltage with a filter by the control circuit shown in FIG. 1. FIG. 3 is a diagram showing an example of setting an FC voltage with a filter by the control circuit shown in FIG. 1. It is a figure for demonstrating FC voltage and FC voltage with a filter.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a diagram showing a configuration of an auxiliary power supply device 10 according to an embodiment of the present invention. The auxiliary power supply device 10 according to the present embodiment is mounted on, for example, an electric vehicle that operates by supplying power from an overhead wire 1 that is a DC power supply, converts a DC voltage supplied from the overhead wire 1 into an AC voltage, and loads the load circuit. 2 (cooling and heating devices in electric cars, lighting devices, etc.).

The auxiliary power supply device 10 shown in FIG. 1 includes a DC filter reactor 11, a DC filter capacitor 12 (filter capacitor), a voltage measuring unit 13, an inverter device 14, an AC filter/transformer unit 15, and a control circuit 16. Prepare

The DC filter reactor 11 has one end connected to the overhead wire 1 and the other end connected to one end of the DC filter capacitor 12. The DC filter capacitor 12 has one end connected to the other end of the DC filter reactor 11 and the other end grounded. The DC filter capacitor 12 is connected to the input side of the inverter device 14 in parallel with the inverter device 14, as described later. The DC filter reactor 11 and the DC filter capacitor 12 operate as a filter that suppresses a harmonic current flowing from the overhead wire 1 to the ground via the inverter device 14.

The voltage measuring unit 13 measures the voltage (FC voltage) of the DC filter capacitor 12 and outputs the measurement result to the control circuit 16.

The inverter device 14 converts the DC voltage input from the overhead wire 1 via the DC filter reactor 11 and the DC filter capacitor 12 into an AC voltage, and outputs the AC voltage to the AC filter/transformer unit 15. The inverter device 14 includes semiconductor switches 141-1 to 144-4. Hereinafter, when the semiconductor switches 141-1 to 144-4 are not distinguished, they are referred to as the semiconductor switch 141. The semiconductor switch 141 is composed of a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a diode connected in antiparallel.

The semiconductor switch 141-1 and the semiconductor switch 141-2 are connected in series, and the semiconductor switch 141-3 and the semiconductor switch 141-4 are connected in series. The series body including the semiconductor switch 141-1 and the semiconductor switch 141-2 has one end connected to one end of the DC filter capacitor 12 and the other end connected to the other end of the DC filter capacitor 12. The series body including the semiconductor switch 141-3 and the semiconductor switch 141-4 has one end connected to one end of the DC filter capacitor 12 and the other end connected to the other end of the DC filter capacitor 12. As described above, the DC filter capacitor 12 is connected in parallel to the input side of the inverter device 14. Further, the connection point between the semiconductor switch 141-1 and the semiconductor switch 141-2 and the connection point between the semiconductor switch 141-3 and the semiconductor switch 141-4 are connected to the AC filter/transformer unit 15.

According to the inverter device 14 having such a configuration, by controlling the switching of each semiconductor switch 141, the DC voltage input from the overhead wire 1 via the DC filter reactor 11 and the DC filter capacitor 12 is converted into an AC voltage. However, it is possible to output from the connection point between the semiconductor switch 141-1 and the semiconductor switch 141-2 and the connection point between the semiconductor switch 141-3 and the semiconductor switch 141-4.

The AC filter/transformer unit 15 smoothes the AC voltage output from the inverter device 14, converts the AC voltage into a desired magnitude, and outputs the AC voltage to the load circuit 2.

The control circuit 16 sets the FC voltage with a filter based on the measurement result of the FC voltage by the voltage measuring unit 13, and controls ON/OFF of the semiconductor switch 141 of the inverter device 14 based on the set FC voltage with the filter ( A control signal (PWM signal) for PWM (Pulse Width Modulation) control is output to each semiconductor switch 141.

2A and 2B are diagrams for explaining PWM control based on the FC voltage with a filter by the control circuit 16, FIG. 2A shows a state in which the FC voltage with a filter is larger than the actual FC voltage, and FIG. , Shows a state in which the FC voltage with a filter is smaller than the actual FC voltage.

The control circuit 16 compares a command value that commands the output voltage of the inverter device 14 with a carrier wave (for example, a triangular wave) corresponding to the value of the FC voltage with filter, and if the carrier wave is smaller than the command value, the logical level is A PWM signal of High (H) is output, and if the carrier wave is equal to or higher than the command value, a PWM signal of Low (L) logic level is output.

As shown in FIG. 2A, when the FC voltage with a filter is higher than the actual FC voltage, the period of the logic level of the PWM signal being L (the period of the semiconductor switch 141 being off) becomes the actual FC voltage value. It becomes longer than when the corresponding carrier wave and the command value are compared. That is, the duty ratio becomes small. When the duty ratio decreases, the output voltage of the inverter device 14 decreases and the power outflow to the load circuit 2 decreases. As a result, the actual FC voltage is likely to rise.

On the other hand, as shown in FIG. 2B, when the FC voltage with a filter is smaller than the actual FC voltage, during the period when the logic level of the PWM signal is L, the carrier wave and the command value according to the value of the actual FC voltage Will be shorter than when compared. That is, the duty ratio becomes large. When the duty ratio increases, the output voltage of the inverter device 14 increases and the power outflow to the load circuit 2 increases. As a result, the actual FC voltage is likely to drop.

In this way, when there is a difference between the actual FC voltage and the FC voltage with filter, the FC voltage easily rises and falls due to this difference. Here, as described above, in the case of vibration in which the FC voltage increases and decreases in a small range, the FC voltage with a filter can be made to follow the actual FC voltage relatively quickly, but the FC voltage in a range larger than the vibration can be achieved. When the voltage fluctuates, it takes time for the FC voltage with filter to follow the FC voltage. In this case, the state in which the difference between the actual FC voltage and the FC voltage with a filter is large continues for a long time, and the output voltage of the inverter device 14 becomes unstable during that time.

Therefore, in the present embodiment, it is considered that when the vibration occurs, the control circuit 16 gradually causes the FC voltage with a filter to follow the FC voltage (follows the formula (1)) to cause a fluctuation. In this case, the FC voltage with a filter is made to immediately follow the FC voltage.

Specifically, the control circuit 16 determines whether the difference D between the FC voltage with a filter (FC voltage with a filter one sample before) and the actual FC voltage is within a predetermined range. Then, when the difference D is within the predetermined range, the control circuit 16 determines that vibration has occurred and causes the FC voltage with filter to follow the actual FC voltage according to the equation (1). On the other hand, when the difference D is not within the predetermined range, the control circuit 16 determines that the fluctuation has occurred. In this case, the control circuit 16 sets the FC voltage at the time when it is determined that the difference D is not within the predetermined range as the FC voltage with filter. Therefore, when fluctuation is considered to occur, the FC voltage with filter can immediately follow the FC voltage. Therefore, the difference D between the actual FC voltage and the FC voltage with filter is large, and it is possible to prevent the output of the inverter device 14 from being unstable for a long period of time.

3A and 3B are diagrams showing an example of setting the FC voltage with a filter by the control circuit 16, and FIG. 3A shows an example of setting the FC voltage with a filter when the FC voltage is oscillated in small increments. FIG. 3B is a diagram showing an example of setting the FC voltage with a filter when the FC voltage fluctuates greatly over a long period of time.

The control circuit 16 determines whether the difference D between the FC voltage with filter and the actual FC voltage is within a predetermined range. Specifically, the control circuit 16 determines whether or not −Th≦D≦Th, where Th is a preset limiter value. Note that the limiter value Th is such that vibration and fluctuation can be distinguished from each other, that is, in the case of vibration, −Th≦D≦Th, and in the case of fluctuation, if the difference D<0, then D< -Th, and if D>0, a value such that Th<D is set.

Therefore, in the case of vibration, as shown in FIG. 3A, −Th≦D≦Th. In this case, the control circuit 16 causes the FC voltage with filter to follow the actual FC voltage according to the equation (1).

On the other hand, it is assumed that fluctuations occur, and as shown in FIG. 3B, the FC voltage greatly increases from time T1 to time T3, and is maintained substantially at the same level after time T3.

In this case, in the conventional method in which the FC voltage with a filter follows the actual FC voltage according to the equation (1), the FC voltage with a filter is gradually increased from time T1 as shown in FIG. The FC voltage can be matched to the actual FC voltage.

On the other hand, in the system according to the present embodiment (this system), when D(<0)<−Th is satisfied at time T2 after time T1 and before time T3, the control circuit 16 As shown in 3B, the FC voltage at that time is set as a new FC voltage with a filter. Therefore, the difference D becomes zero. After that, the FC voltage gradually increases until time T3, but since −Th≦D≦Th, the control circuit 16 causes the FC voltage with filter to follow the actual FC voltage according to the equation (1).

Here, in this method, when the difference D is out of the predetermined range (time T2 in FIG. 3B), the FC voltage at that time is set as the FC voltage with filter. Therefore, in the present method, as compared with the conventional method, even if the FC voltage with a filter is made to follow the FC voltage according to the equation (1) after time T2 as in the conventional method, at time T4 before time T5. , FC voltage with a filter can be matched with FC voltage. Therefore, even when fluctuations occur, the difference D between the FC voltage and the FC voltage with a filter is large, and it is possible to prevent the output of the inverter device 14 from being unstable for a long period of time.

As described above, according to the present embodiment, the auxiliary power supply device 10 includes the inverter device 14 that converts the DC voltage supplied from the overhead wire 1 that is the DC power supply into the AC voltage, and the inverter device 14 on the input side of the inverter device 14. The DC filter capacitor 12 connected in parallel with the DC filter capacitor 12 and the FC voltage with the filter are set so as to follow the FC voltage which is the voltage of the DC filter capacitor 12, and the inverter device 14 is controlled based on the set FC voltage with the filter. And a control circuit 16. When the difference D between the FC voltage with a filter and the FC voltage is within a predetermined range, the control circuit 16 follows the FC voltage with a filter to the FC voltage at a speed according to a predetermined filter constant T _1. Then, when the difference D is outside the predetermined range, the FC voltage at that time is set as the FC voltage with filter.

Therefore, when the difference D deviates from the predetermined range and the variation is considered to occur, the FC voltage with the filter can be made to follow the FC voltage at that time, and the actual FC voltage and the FC voltage with the filter can be obtained. It is possible to prevent the state in which the output of the inverter device 14 is unstable for a long period of time due to the large difference in

Although the present invention has been described based on the drawings and the embodiments, it should be noted that those skilled in the art can easily make various variations or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, the functions included in each block can be rearranged so as not to logically contradict each other, and a plurality of blocks can be combined into one or divided.

1 Overhead Line 2 Load Circuit 10 Auxiliary Power Supply Device 11 DC Filter Reactor 12 DC Filter Capacitor 13 Voltage Measuring Unit 14 Inverter Device 141 Semiconductor Switch 15 AC Filter/Transformer Unit

Claims (1)

An auxiliary power supply device for converting a DC voltage supplied from a DC power supply into an AC voltage and supplying the AC voltage to a load circuit,
An inverter device for converting a DC voltage supplied from the DC power supply into an AC voltage,
On the input side of the inverter device, a filter capacitor connected in parallel to the inverter device,
A control circuit that sets a FC voltage with a filter so as to follow the FC voltage that is the voltage of the filter capacitor, and controls the inverter device based on the set FC voltage with the filter;
When the difference between the FC voltage with the filter and the FC voltage is within a predetermined range, the control circuit converts the FC voltage with the filter into the FC voltage at a speed according to a predetermined filter constant. An auxiliary power supply device characterized in that when the difference is out of the predetermined range, the FC voltage at that time is set as the FC voltage with the filter when the difference is made to follow.

Images