JPH0496658A - Inverter control system - Google Patents

Abstract

PURPOSE:To suppress noise due to mutual interference and high frequency noise by switching between a first operation mode in which switching elements are turned ON or OFF continuously during half period of a sinusoidal wave and a second operation mode in which the switching elements are turned ON or OFF with a variable width signal having frequency higher than the audio frequency, every half period of the sinusoidal wave. CONSTITUTION:When positive half cycles of intervals A1, A2, A5, A6 are outputted, a switching element (SW)T1 is turned ON continuously and an SWT2 constituting a series circuit with the SWT1 is turned OFF continuously in a first operating mode, whereas an SWT4 is turned ON or OFF with a variable width signal having frequency higher than an audio frequency and an SWT3 constituting a series circuit therewith is turned OFF or ON in a second operation mode. When negative half cycles of intervals A3, A4, A7, A8 are outputted, the SWT3, T4 are operated in the first operating mode whereas the SWT1, T2 are operated in the second operating mode. Operating modes of the series circuit of two sets of switching elements are switched every half period of a sinusoidal wave.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an inverter control method, and more specifically, an inverter that can reduce inverter noise and high-frequency noise and prevent output waveforms from becoming asymmetrical between positive and negative. Conventional technology A circuit that obtains a sine wave at the output by switching DC voltage with a high frequency inverter is a control method using the direct [1iifi] method as shown in Figure 5.
1 of DC power is input to the inverse converter 2, and the diodes D1, D2, . D3 D4 and switching elements TI, T2, T3 . It is known that T4 is turned on and off to create a positive and negative pulse train, and this pulse train is converted into a sine wave by a filter circuit consisting of a reactor 3 and a capacitor 4, and is supplied to a load 5. Switching element T1 in a simple circuit. T2. T3.
Two known control systems for T4 are shown in FIG. 3 and FIG. 4.

That is, the one in FIG. 3 includes the series-connected switching elements T1. T2 is turned on or off every half cycle of the output sine wave, and the switching elements T3.T2 and T2 are connected in series. T
4 is turned on or off by a variable width signal with a frequency higher than the audible frequency, and when the switching element TI is turned on, the switching element T4 operates to create a positive pulse train,
When switching element T2 is turned on, switching element T3
is operating and creating a negative pulse train. To explain its operation with reference to FIG. 3, first, in period A1, the output voltage V is positive, the output current i is negative, and the switching elements TI, T
3 is turned on, a current flows through the path of the accelerator 3 - diode D1 -> switching element T3 - load 5 - reactor 3, and the current flows through the switching element TI.

When T4 is turned on, a current flows through the path consisting of the accelerator 3, the diode D1, the DC power source 1, the diode D4, the load 5, and the reactor 3. Next, in period A2, the output voltage V is positive;
When the output current 1 becomes positive and switching elements Tl and T4 are on, DC current fil - switching element T1 - reactor 3 - load 5 - switching element T4 - DC power supply 1
A current flows through the switching element T1. When T3 is turned on, a current flows through the path of the accelerator 3 - the load 5 -> the diode D3 - the switching element T1 - the reactor 3. Next, in period A3, the output voltage V is negative, the output current I is positive, and the switching elements T2. When T4 is turned on, a current flows through the following path: Accelerator 3 → Load 5 - Switching element T4 - Diode D2 - Reactor 3, and when switching element T2 and T3 are on, the current flows as follows: Accelerator 3 → Load 5 - Diode D3 → DC t'a1 → Diode D2→
Current flows through a path called reactor 3. Next, in period A4, the output voltage V becomes negative, the output current 1 becomes negative, and the switching element T2. When T3 is on, current flows through the path: DC power supply 1 - switching element T3 - load 5 - reactor 3 - switching element T2 - DC power supply 1, and the current flows through switching element T2. When T4 is turned on, a current flows through the path of the handle 3 - switching element T2 - diode D4 -> load 5 - reactor 3. In this way, a positive and negative pulse train as indicated by U in FIG. 3 is obtained.

On the other hand, the one shown in Fig. 4 turns on and off all switching elements using a variable width signal with a frequency higher than the audible frequency, and uses the same operation as the one shown in Fig. , creating a negative pulse train. To explain its operation with reference to FIG. 4, first, in period A1, the output voltage V is positive, the output current i is negative, and the switching element T
2. When T4 is turned on, ti flows through the following path: accelerator 3 -> switching element T2 -> diode D4 - load 5 -> reactor 3. In the next period A2, the output voltage V becomes positive, the output current i becomes positive, and the switching element T2. When T4 is turned on, the accelerator 3 - load 5 → switching element T4
A current flows through the path: - diode D2 - reactor 3. Next, in period A3, the output voltage V is negative and the output current i is positive, and when the switching elements TI and T3 are turned on, a current flows through the path of the accelerator 3 -> load 5 -> diode D3 - switching element T1 - reactor 3. Next, in period A4, the output voltage ■ becomes negative, the output current 1 becomes negative, and the switching element T1. When T3 is on, reactor 3-
Current flows through the diode D1-Switch, switching element T3-load 5-reactor 3 path. Note that, among the operations of the switching elements in each of the above-mentioned periods, descriptions of those that are common to those shown in FIG. 3 are omitted. Further, although each diagram shows the case of an inductive load, it goes without saying that the same applies to a resistive load and a capacitor input load.

Problems to be Solved by the Invention The above inverter control system shown in FIG. 3 includes two types of drive circuits and two types of switching elements, that is, a drive circuit that turns on or off every half cycle of the output sine wave. Since a circuit, a drive circuit for turning on or off with a variable width signal having a frequency higher than an audible frequency, a low-speed switching element, and a high-speed switching element are required.
The disadvantage was that the circuit became complicated.

Also, the one in Figure 4 can be configured with a single drive circuit, but
The difference in the voltage drop of the switching elements and the difference in the delay time of the drive circuit creates a difference between the positive side pulse train and the negative side pulse train, causing the reactor 3 to generate vibration noise and create an imbalance in the output waveform. In addition, since the operating frequency of the reactor 3 is twice the operating frequency of the switching element, noise and high-frequency noise are generated due to mutual interference and the operating frequency of the switching element.

Means for Solving the Problems The present invention solves the above-mentioned drawbacks by connecting two series circuits of switching elements to a DC power supply, and turning on and off the switching elements in each series circuit in opposite phases. In the method of supplying a sine wave output to the load, the operation mode of each of the series circuits is a first operation mode in which the series circuits are continuously on or off for a half period or one period of the sine wave, and a first operation mode in which the operation mode is continuously turned on or off for one half period or one period of the sine wave; It consists of a second operation mode in which the cycle period is turned on or off by a variable width signal with a frequency higher than the audible frequency, and the operation of each series circuit according to each operation mode is switched every half cycle or every cycle of the output sine wave. This is a characteristic feature.

Operation In the inverter control method as described above, all switching elements are turned on and off according to the first operation mode and the second operation mode, so it can be configured with a single drive circuit, and Even if there is a difference between the pulse train of Since the operating frequency of the second operating mode is the same as the operating frequency of the second operating mode, it is possible to prevent noise and high-frequency noise from occurring due to mutual interference.

Examples Below, the control method of the present invention shown in FIGS.
This will be explained by applying it to the circuit diagram of the inverter shown in the figure.

That is, the control method shown in FIG. 1 is based on the period AlA2. A5.
When outputting the positive half cycle of A6, the first operation mode is set in which the switching element Tl is continuously turned on, and the switching element T2 forming a series circuit with it is continuously turned off, and the switching element T4 is turned on in an audible manner. A second operation mode is set in which the switching element T3 forming a series circuit is turned on or off by a variable width signal having a frequency higher than or equal to the frequency, and the switching element T3 is turned on or off during the period A3. A4. A7. A
In order to output a negative half cycle of 8, the first operation mode is set in which the switching element T3 is continuously turned on and the switching element T4 is continuously turned off. The second operation mode is turned on or off by a variable width signal, and the operation mode of the series circuit of 2Mi switching elements is switched every half period of the sine wave. Therefore, it can be configured with a single drive circuit, and the operating frequency of the reactor 3 matches the operating frequency of the switching element.
The generation of noise and high frequency noise due to mutual interference can be prevented.

On the other hand, the control method shown in FIG. 2 applies when outputting the positive half cycle of the period AI, A2, and when outputting the positive half cycle of the period A3. When outputting the negative half cycle of A4, use the same method as shown in Figure 1.
The next positive half cycle, period A5. In A6, the first operation mode is set in which the switching element T4 is continuously turned on and the switching element T3 forming a series circuit with it is continuously turned off, and the switching element TI is turned on with a variable width signal having a frequency higher than the audio frequency. or OFF, a second operation mode in which the switching element T2 forming a series circuit with this is turned OFF or ON, and the period A7. When outputting the negative half cycle of A8, the first operation mode is set in which the switching element T2 is continuously turned on and the switching element T1 is continuously turned off.
3. This is a second operating mode in which T4 is turned on or off by a variable width signal with a frequency higher than the audible frequency, and the operating mode of the series circuit of two sets of switching elements is switched every cycle of the sine wave. .

That is, period A1. The series circuit of switching elements, which is in the first operating mode in the positive half cycle of A2, operates in the next period A5. a second operating mode in the positive half cycle of A6;
Period A3. The series circuit of switching elements, which is in the first operating mode in the negative half cycle of A4, operates in the next period A7. A
The negative half cycle of 8 is the second operating mode. Therefore, in addition to the effect of the method shown in Figure 1, even if there is a difference between the positive side pulse train and the negative side pulse train due to the difference in the voltage drop of the switching element or the difference in the delay time of the drive circuit, the next cycle A corrective action is taken.

Note that in each of the above embodiments, the operation of the switching element in each period is the same as that in FIGS. 3 and 4, and therefore a description thereof will be omitted. Further, although each diagram shows the case of an inductive load, it goes without saying that the same applies to a resistive load and a capacitor input load.

Effects of the Invention As described in detail in the embodiments, the inverter control method of the present invention can be configured with a single drive circuit, so the circuit can be simplified. In addition, since the operating frequency of the reactor matches the operating frequency of the switching element, it is possible to prevent the generation of noise and high-frequency noise due to mutual interference.The frequency band of high-frequency noise also becomes high, so it can be removed with a small filter. can.

Furthermore, since the series circuit of the two sets of switching elements switches the operation mode every half cycle or every cycle of the output sine wave, the loss of the switching elements can be equalized.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining the inverter control system of the present invention, Figures 3 and 4 are diagrams for explaining the conventional inverter control system, and Figure 5 is for each control system. FIG. 2 is a circuit diagram of an inverter in which a ■...DC power supply 2...Inverse conversion section 3...Reactor 4...Capacitor 5...Load Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A series circuit of two sets of switching elements is connected to a DC power supply, and a load is connected between the series connection points of each series circuit,
In an inverter control method that supplies a sine wave output to the load by turning on and off switching elements in each series circuit in opposite phases, the operation mode of each series circuit is continuous for a half period or one period of the sine wave. A first operation mode in which the signal is turned on or off by a sine wave, and a second operation mode in which the signal is turned on or off by a variable width signal having a frequency equal to or higher than the audible frequency for a half cycle or one cycle of a sine wave. An inverter control method characterized by switching circuit operation every half cycle or every cycle of an output sine wave.