JPS59178972A - Control system of voltage type pulse width modulation inverter - Google Patents

Abstract

PURPOSE:To stably control the output by performing a pulse width modulation by using an in-phase signal with a system proportional to the system voltage instantaneous value and a phase advance signal synchronized with the system voltage produced by an oscillator in a phase locked loop circuit. CONSTITUTION:A system voltage signal is converted by a waveform converter 1201 to a digital signal. A phase detector 1202, a low pass filter 1203, a voltage controlled oscillator 1206, and a frequency divider 1207 from a phase locked loop, and the output of the frequency divider 1207 is synchronized with the prescribed phase displacement with the system frequency. The signal returned to a sinusoidal wave by a waveform converter 1208 is divided by the output of a sample-holding circuit 1211, and used as a desired amplitude phase advance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides control of a voltage-type pulse width modulation inverter that is connected to an AC system via a filter in order to send power from a DC power source with large voltage fluctuations such as solar cells or wind power generation to an AC system. Regarding the method.

In such impark, it is important to open the amplitude, frequency and phase of the input voltage fundamental wave so that it corresponds to the amplitude, frequency and phase of the system voltage.
Moreover, in small-capacity equipment, a simple and inexpensive control device is desired.

Until now, control signals specifying the amplitude, frequency line, and phase of the input voltage fundamental wave are output from the sine wave oscillator, and a high frequency signal specifying the modulation frequency is extracted from the triangular wave oscillator. A modulation/loss signal is created by cutting the signals, and the inverter exchange valve is controlled according to this signal.The 07less width modulation method is well known.

Specifically, this is achieved by command-controlling the frequency, phase, and amplitude separately using phase-locked loop (PLL) technology or automatic voltage control (AVR) technology. , the latter has an open DC circuit for the AC voltage detector output, etc., so the circuit output has a certain delay with respect to the system voltage at that time. As a result, the follow-up operation is delayed in response to sudden changes in grid voltage, 4,! There is a drawback that if there is a sudden change in voltage during operation with a small output in J, control of the output voltage and reactive power tends to become unstable.

Therefore, in order to obtain control signals that command the frequency, phase, and amplitude of the inverter output voltage fundamental wave from the iF sinusoidal oscillator, by deriving them from the grid voltage itself, we ensure perfect followability and also provide power to the AC grid. A control system that can easily adjust the output of the feed/input/motor is conceivable.

First, the principle of a power supply system to which such a control force formula is applied will be explained, thereby clarifying the purpose of the present invention.

In FIG. 1, reference numeral 1 denotes a DC power source with significant voltage fluctuations, which is comprised of, for example, a solar cell. Electric power is sent from the DC power supply 1 to the AC system 4 via the voltage type/e pulse width modulation input 2 and the filter 3. 5 indicates load.

In this case, the amplitude, frequency and phase of the output voltage fundamental wave of the ear motor 2 are commanded by the control signal A introduced into the nomorus width modulator 16.

That is, if the switching time of the switching elements of the inverter 2 is ignored, the output voltage fundamental wave of the inverter 2 is proportional to the width of the j layer of the control signal A, and its phase matches that of the control signal A.

Further, harmonics included in the output voltage of the inverter 2 are attenuated by the filter 3.

The system voltage detected via the signal transformer 11 connected to the output side of the filter 3 is introduced into the adder 14, directly on the one hand and via a phase shifter 12 and a multiplier 13 on the other hand. Adder 14 introduces the control signal A into width modulator 16 .

This width modulator 16 uses the control number 48 A and the triangular wave signal B (triangular wave oscillator 15) that specifies the modulation frequency.
The signal C that drives the inverter 2 is generated based on the magnitude ratio of (generated by).

The phase shifter 12 functions to advance the phase of the system voltage detection signal by 90 degrees, and the multiplier 13 functions to multiply the output signal of the phase shifter 12 by a variable coefficient. Note that this variable coefficient is given by the output setting device 17.

First, we will describe the operation when the variable coefficient of the output setter 17 is zero. In this case, the control signal A given from the adder 14 to the . The output voltage fundamental wave of is in phase with the grid voltage. At this time, the circuit constants are selected so that the fundamental wave amplitude of the output voltage mentioned in "2" also matches the amplitude of the system voltage.

Therefore, the relationship between the inverter output voltage EO and the system voltage ES is E. -ES, and since both are in an equilibrium state, the inopert output sent to the system is zero.

Even with variations in the amplitude, phase and frequency of the grid voltage,
Since the control signal A directly follows the fluctuation, the state of zero output of the innoparter is maintained.

Next, the operation when a non-zero variable coefficient is set by the output setting device 17 will be described. In this case, active power corresponding to the above-mentioned coefficient is sent from Inno Mark to the grid.

That is, considering only the fundamental wave in the circuit configuration of the filter 3 shown in FIG. 2, the output voltage E of the inverter 2 is on the input side. is applied, and current flows through the filter reactor with impedance jXL. is filter 3
output (difference from i111 voltage Es, that is, Eo-E
Determined by s.

According to the configuration shown in FIG. 1, the signal voltage directly introduced into the adder 14 via the signal transformer 11 is Es
corresponds to The signal voltage still introduced into the adder 14 via the phase shifter 12 and the multiplier 13 is advanced in phase by 9o with respect to the grid voltage E8, and is given a coefficient of β by the output setter 17. Then, Jβ゛Es 〇 Therefore, the output voltage of inverter 2 is Eo-(1+Jβ
) ES becomes.

Therefore, electrician. is ES Io ”(Eo Es )/jχL−β・XL, which shows only the effective component for the grid voltage ES,
And it changes in proportion to the coefficient β.

In addition, the system current worker s is the above-mentioned effective current worker. In addition, it includes the leading reactive current of the filter capacitor with impedance -jxL, but when the inverter is in constant operation,
This ineffective amount is so small that it can be ignored.

Therefore, in this case, the operating power factor of the inverter is maintained high. If necessary, by suitably adjusting the coefficient for the component in phase with the system voltage included in the control signal A, it is also possible to compensate for the invalid component described in 2.

- If the resistance included in the reactor of the filter 3 is still taken into consideration and operation with a power factor of 1 is desired, the phase shifter 1
The desired result is obtained by setting the advance angle by 2 to a value less than 90°. By adjusting the advance angle by the phase shifter [2], operation with a desired power factor is also possible.

By the way, when an integrating circuit is used as the phase shifter 12, the output current of the inverter 2 is changed to the multiplier 13 as described above.
When the system voltage changes, the output of this integrating circuit also changes, and the output current and output power of the inverter 2 change.

In other words, in the signal calculation in FIG. 1, when the voltage ratio of the signal transformer 11 is 1:1, the output of the phase shifter 2 is /E3d t = j E with respect to the system voltage ES.
s and is proportional to the size of Es. Therefore, the output current ■o of the inverter 2 is ■. -β-22L, which is proportional to the grid voltage, and the output power also changes as the grid voltage changes.

1. If the system voltage is distorted, the output of the integrating circuit will also be distorted9, and the output current of the inverter 2 will also be distorted.

An object of the present invention is to eliminate such inconveniences and to provide a voltage-type pulse I fault modulation inverter control method (41 system) that can perform stable output control without being affected by sudden changes or distortions in the system voltage.

According to the present invention, in order to transfer power between a DC power supply and an AC system, a voltage-type pulse width modulation inverter connected to an AC system through a filter is connected to the frequency and phase of the fundamental wave of the inverter output voltage. As a control signal for specifying the pulse width, a signal obtained by vector-synthesizing a first AC signal directly corresponding to the grid voltage and a second signal corresponding to a voltage phase-shifted from the grid voltage at a variable ratio is used as a control signal to specify the pulse width. When performing modulation, the first signal is an in-phase signal with the grid that is proportional to the instantaneous grid voltage value, and the second signal is generated by an oscillator in the circuit via a phase rod loop circuit. This can be achieved by using a phase-advanced signal that is the same as the system voltage.

Examples of the present invention will be described in detail below.

FIG. 3 is a block diagram of a phase shifter used in the present invention, and the present invention is an improvement to the phase shifter 2312 in the system shown in FIG.

In the phase shifter circuit shown in FIG. 3, a system voltage signal is first converted into a digital signal by a waveform converter 1201. Phase detector] 2o2, low-pass filter 1203, voltage-controlled oscillator 1206, and frequency divider 1207 constitute a phase-locked loop (PLL), and the output of the frequency divider 1207 is the phase detector 12020 frequency, that is, the system frequency and a constant phase. They are synchronized with a difference. In order to adjust the width of this phase shift and obtain a phase advance signal of a desired angle, the output of the phase advance angle setter 1205 is added to the adder 1203.
It allows it to be added to the output. Tsu-! , 9 waveform converter]2o8 can be adjusted so that the output of the waveform converter 1201 has a desired leading phase with respect to the input of the waveform converter 1201.

The signal converted back to a sine wave by the waveform converter 2o8 is sent to a sample hold circuit 1211 by a divider 1209.
It is divisible by the output of , and is used as a phase-leading signal with the desired amplitude. Note that the sampling timing of the sample and hold circuit 12]1 is a short period of a constant phase such as the peak voltage phase of the grid voltage, and this is because the sample signal generator 1210 that receives the output signal of the PLL generates a sample signal corresponding to the peak voltage phase of the grid voltage. is determined by generating . By employing this sample bold circuit 12], it is expected that changes in the system voltage can be followed and calculated at a speed of one cycle or less.

When such a circuit is used as the phase shifter 12 shown in Fig. 1, its output is as follows: the actual value of the system voltage is Es1, and the rated value is 1.:r3n.
Then, it is +58, which is inversely proportional to the size of Es. Therefore, the output current of inverter 2. is inversely proportional to the system voltage Es. It can be seen that the output power is a constant value.

When this circuit failure configuration is adopted as described above, an integrating circuit is used to create a phase shifter (unlike when the phase shifter is configured by 1Q), when the grid voltage changes, the leading phase component of the control signal is inversely proportional to it. As the output current changes, the output current of the inverter 2 changes, and the output power becomes the same as the value before the change.

Furthermore, since the leading phase component of the open side 1st number is generated from the output of the PLL square wave oscillator, it only depends on the distortion and the characteristics of the waveform converter 12o8. Regardless of the state of distortion in the system voltage, an inverter output current with less distortion can be seen.

In another embodiment, a sample signal generator 1210. It is also possible to remove the sample bold circuit 1211 and the divider 12o9, and in this case, the inverter output current is always constant regardless of changes in the system voltage.

That is, the phase shifter output becomes jEsn, and the output current of the inverter 2 is constant at ■o2βESn''+.Therefore, the output power is proportional to.

In the following two examples, the control signal in phase with the grid is configured to correspond to the instantaneous value of the grid voltage, so the response of this component is the cause of distortion in the inverter output current. This will not cause any change in the output current.

In the circuits of these two embodiments, when it is desired to suppress fluctuations in DC power, the output power of the previous embodiment is connected to the end of the distribution line with a large circuit resistance, and the output current of the inverter is If a change in the system voltage is expected to occur due to a change in the voltage, the circuit can be used as a circuit with a constant output current as in the embodiment described later.

In addition, in the above description, if this is made negative or if the leading phase signal is switched to the slow phase signal, the same effect can be obtained even when performing a converter operation that takes power from the grid and sends it to the DC side.

As described above, in the sub-side 1 method of the present invention, in order to transfer power between a DC power source and an AC system, a voltage source/Gurus width modulation inverter connected to the AC system via a filter is connected to the inverter output. As a control signal that specifies the frequency and phase of the voltage fundamental wave, a first AC signal that directly corresponds to the grid voltage and a second signal that corresponds to a voltage that is phase-shifted from the grid voltage are synthesized in four vectors at a variable ratio. Using the signal obtained by
When performing pulse width modulation, the output operation of the inverter can be performed without being affected by system voltage fluctuations or voltage distortion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a power supply system to which the method of the present invention is applied, FIG. 2 is a circuit diagram of a filter, and FIG. 3 is a block diagram showing details of the phase shifter in FIG. 1. ■...DC power supply 2...t Globe Norse width modulation inverter 3...Filter 4...AC system 5...Load J
l... Signal transformer 2... Phase shifter 3.
... Multiplier 14 ... Adder 15 ... Triangular wave oscillator] 6 ... Pulse width modulator 17 ... Output setter 1201 ... Waveform converter 1202 ... Phase detector] 203 - Low pass Filter 1204... Adder 1205... Phase advance angle setter 1206... Voltage controlled oscillator 1207... Frequency divider 1208... Waveform converter 1209... Divider 1210... Sample signal generation Device 1211...Sample hold circuit Applicant Fuji Electric Manufacturing Co., Ltd. Agent Patent attorney Tsukasa Kubo

Claims (1)

[Claims] A voltage source/loose width modulation inverter connected to the AC system via a filter that transmits and receives power between the DC power supply and the AC system is used as a control signal that specifies the frequency and phase of the inverter output voltage fundamental wave. When performing pulse width modulation using a signal obtained by vector synthesis of a first AC signal directly corresponding to voltage and a second signal corresponding to a voltage phase-shifted from the grid voltage at a variable ratio, As the first signal, an in-phase signal with the grid proportional to the instantaneous value of the grid voltage is used, and as the second signal, it is synchronized with the grid voltage generated by the oscillator in the circuit via a phase-locked loop circuit. A control method for a voltage type) 4-pulse width modulation inverter characterized by using a phase-advanced signal such as