JP3877042B2 - Auxiliary resonance circuit - Google Patents

Description

よって、ｔ_１、ｔ_２は次のような条件を満たせばよい。

【００３３】
ここで、Ｉ_ｓ１、Ｉ_ｓ２、Ｖ_ｄｃは主変換器についているセンサ信号から求められるので、補助スイッチング回路の動作タイミングを決められることが分かる。
また、ｔ_１、ｔ_２タイミングを上記右辺計算値より大きめにとれば、ＺＶＳ動作の確実性を一段と上げることができる。
【００３４】
【発明の効果】
以上述べたように、本発明の補助共振回路を利用すれば、少ない部品点数、かつ、ローコストで信頼性の高いソフトスイッチング変換装置を構成することができる。
また、補助スイッチングタイミングの決定についても、共振回路動作用の追加センサを必要とせず、マージンも大きくとれ、さらに、共振形変換器本来の低スイッチング損失、低電磁ノイズ特性と合わせて、環境に優しい電力変換システムを実現でき、実用上きわめて有用である。
【図面の簡単な説明】
【図１】本発明の補助共振回路を用いた共振形電力変換器の主回路構成を示す図である。
【図２】従来技術を説明するための三相電力変換器の主回路図例である。
【図３】本発明の原理を説明するための主回路等価モデルである。
【図４】本発明の共振回路の転流時における信号波形と動作波形である。
【図５】本発明の共振変換器における転流時の動作遷移図である。
【符号の説明】
１ 多相交流電源
２ 多相コンバータ装置
３ 本発明の補助共振回路
４、５，６、１２ 半導体スイッチング素子
７ 共振用リアクトル
８ 電圧平滑用直流コンデンサ
９ 多相インバータ装置
１０ 多相交流負荷
１１ 直流電圧源
１３ 主変換器の等価モデル
１４ 共振用等価コンデンサ
１５ 等価クランプダイオード
１６ 等価電流源
Ｑ_０、Ｑ_１、Ｑ_２ 本発明の補助共振回路のスイッチング素子
Ｑｓ 主変換器の主スイッチング素子
Ｄ 等価クランプダイオード
Ｖ_ｄｃ 直流電圧源の電圧値
Ｉ_s1,Ｉ_s2 主変換器のスイッチング前と後の等価負荷電流
Ｌ_ｒ 共振用リアクトルのリアクタンス値
Ｃ_ｒ 共振用等価コンデンサの容量値
Ｖ_ｒ 直流リンク電圧値
Ｉ_ｒ 共振用リアクトル電流
ｔ_１ 転流開始時間
ｔ_２ 直流リンク電圧回復開始からＱ_０オンまでの時間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor power converter, and more particularly to a circuit system of a resonant power converter that performs a switching operation at zero voltage by utilizing a resonance phenomenon.
[0002]
[Prior art]
FIG. 2 shows a main circuit diagram of a conventional three-phase power converter most commonly used in the industry.
In FIG. 2, 11 is a DC power source, 8 is a DC capacitor for smoothing DC voltage, 10 is a three-phase AC load such as an AC motor, 9 is a main conversion bridge that plays the role of power conversion, and 12 is a conversion This is a semiconductor switching element constituting a bridge.
[0003]
As shown in the figure, the semiconductor switching element is generally composed of a semiconductor switch part (transistor part) that is turned on and off by a gate signal, and a free-wheeling diode part connected in reverse parallel to the semiconductor switch part.
In an actual semiconductor switch, a parasitic capacitance such as a storage capacitor always exists, and these are also shown in the drawing. In general, the parasitic capacitance may be regarded as a demerit of the switch. However, when configuring a resonant converter, the parasitic capacitance can be used as a part of the LC resonance circuit.
[0004]
The power conversion is performed by an on / off switching operation of the semiconductor switch element, and the conventional on / off switching operation is performed by a so-called hard switching method.
In the case of hard switching, during the switching operation period (commutation period), the terminal voltage applied to the switching element and the current flowing through the element overlap (both voltage and current are not zero), and the product of this voltage and current is the switching Switching loss is consumed by the element.
This switching loss is proportional to the switching frequency, and as the switching frequency is set higher, an excessive switching loss is generated and the efficiency of the conversion device is lowered.
Furthermore, during the switching operation, when the current passes through the diode part of the switching element in the direction of the phase current, if an ON signal is output to the switch element on the opposite side of the same pole, a short circuit is caused to the pole momentarily due to the parasitic capacitance. Since this phenomenon occurs, electromagnetic noise is generated due to an excessive current surge caused by a short circuit, which adversely affects the electromagnetic environment.
[0005]
In recent years, with the aim of creating a converter with high efficiency and excellent electromagnetic environment, research on a soft switching method using a resonance phenomenon has been conducted. The principle is that an auxiliary resonant circuit is provided in the main converter circuit. The switching operation of the converter is performed after the terminal voltage or current of the switching element is smoothly reduced to zero by the auxiliary resonance circuit.
In this case, either or both of the voltage and current are zero during the switching commutation period of the main converter, so that no switching loss occurs and the commutation is performed smoothly. Can be significantly reduced.
Hereinafter, for convenience of description, switching at zero voltage is abbreviated as ZVS, and switching at zero current is abbreviated as ZCS.
[0006]
Various circuit systems have been proposed for the auxiliary resonant circuit of the resonant converter, but can be roughly classified into two types. One is an auxiliary resonance pole type in which a resonance circuit for auxiliary switching is added to each pole, and the other is a direct current that collectively processes by one set of resonance circuits for all the poles of the main converter. Link resonance type.
Each of these circuit systems has advantages and disadvantages in terms of the number and life of the components to be used, the ease and certainty of the switching sequence, and the necessity of adding a sensor for operating the resonant circuit.
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and provides a circuit system that can realize soft switching operation with a small number of parts and without requiring an additional sensor in a DC link resonance type conversion system. It is.
[0008]
[Means for Solving the Problems]
In a DC link of a semiconductor power conversion device that converts power from single or multiple multiphase AC to DC, or from DC to single or multiple multiphase AC,
A first semiconductor switching element that electrically cuts off a DC link and a DC power supply or a DC capacitor having an equivalent function thereto, and a second semiconductor switch connected in series with each other and connected in parallel with the DC power supply or the DC capacitor And a third semiconductor switching element, and a resonance reactor inserted between the interconnection point of both the semiconductor switching elements and the DC link connection point of the first semiconductor switching element.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a main circuit configuration when the auxiliary resonant circuit according to the present invention is applied to a converter / inverter power conversion system.
In the figure, 1 is a polyphase AC power source, 2 is a converter for converting AC power to DC, 3 is an auxiliary resonance circuit in the present invention, 8 is a DC capacitor for smoothing the DC link voltage, and 9 is DC power. The multiphase inverter device 10 for converting to phase AC is a multiphase AC load such as an AC motor.
In the auxiliary resonance circuit 3 of the present invention, 4 is a semiconductor switching element Q ₀ for separating the DC link from the DC capacitor, 5 and 6 are semiconductor switching elements Q ₁ , Q ₂ and 7 for controlling the auxiliary resonance circuit. Reactor Lr.
In this embodiment, one converter and inverter are connected to the common DC link, but a plurality of converters and inverters can be connected.
[0010]
The auxiliary resonant circuit of the present invention only has two types of components, ie, a semiconductor switching element and a resonance reactor, and has a semi-permanent lifetime, so that it has excellent reliability.
Further, since the number of parts is small and can be used in common with a plurality of main converters, an increase in cost due to the addition of an auxiliary circuit can be minimized.
Furthermore, the snubber circuit can be omitted or used in common with the main converter in combination with the ZVS operation described later, so that the cost of the converter can be kept low.
[0011]
The operation of the auxiliary resonance circuit of the present invention is to start the resonance operation immediately before the switching element of the main conversion circuit performs the commutation operation, and once drop the DC link voltage to zero, then the main conversion circuit in the zero voltage state. The switching operation is performed (ZVS).
As a result, the switching loss generated during the switching operation is reduced to zero, thereby greatly improving the conversion efficiency of the system and greatly suppressing the generation of electromagnetic noise.
[0012]
In order to facilitate understanding of the operating principle of the auxiliary resonant circuit, first, the main circuit is modeled and described in detail using its equivalent circuit.
An equivalent circuit of the modeled main circuit is shown in FIG. In the figure, reference numeral 13 denotes a portion corresponding to 2 and 9 in FIG. 1, which is an equivalent circuit of the main converter. 8 'is a smoothing DC capacitor as in 8 of FIG. 1, and its voltage value Vdc is almost constant during the commutation operation, and can be regarded as a DC voltage source. 3 'is an auxiliary resonant circuit of the present invention.
[0013]
In 13 main converter equivalent circuits, 14 is an equivalent resonant capacitor _Cr , and the capacitance value is the sum of the additional snubber capacitor capacity and the parasitic capacitor capacity of the main converter switching element.
In each pole of the main converter, one of the upper and lower switching elements is short-circuited due to current conduction, so that the equivalent capacitance of this pole is equal to the parasitic capacitance (Cs) of one switching element. If the number of poles constituting the main converter is n, the equivalent capacitance value of the total parasitic capacitance can be estimated as n × Cs. It is clear that the equivalent resonant capacitor voltage Vr is equal to the DC link voltage.
[0014]
Reference numeral 15 is a representative of a diode connected in reverse parallel to the switching element of the main converter, and in resonance operation. It also serves as a clamp diode D.
16 is a load current flowing from the main converter to the DC link, but the value I _S is dependent on the on-off state of each switching element of the polyphase load current value and the primary transducer, during commutation period, alternating load current Since it is a substantially constant value, it can be regarded as a current source depending on the on / off state of the main switching element.
[0015]
Hereinafter, the principle of commutation operation of the main converter when the auxiliary resonance circuit of the present invention is used will be described in detail using the above-described equivalent model.
In the switching operation of the main switching element, the commutation operation when the current flowing in / out of the DC link changes from the state flowing into the DC link to the drawing state will be described as a representative.
[0016]
The commutation operation consists of 10 modes in total. FIG. 4 shows a switching signal given to each switching element, a DC link voltage Vr, and a current Ir waveform flowing through the resonance reactor Lr in each mode. FIG. 5 shows the operation transition from mode 1 to mode 10.
The operation principle will be described below with reference to the operation transition diagram of FIG.
[0017]
Mode 1:
This mode is a steady state before commutation operation. The auxiliary switches Q ₁ and Q ₂ are off and Q ₀ is on, and no current flows through the resonance reactor, that is, the auxiliary resonance circuit is in a resting state. The load current flows into the DC power source through the diode part of Q ₀ , and the link voltage is approximately the same Vdc as the DC power source.
[0018]
Mode 2:
This mode is a commutation start mode. By applying an off signal to Q ₀ and an on signal to Q ₁ , a commutation operation starts and a transition is made to this mode. In this case, the initial current is zero in the resonant reactor Lr, the change in the current is also suppressed to Lr, the on Q ₁ represents a zero-current switching (ZCS). Further, even give off signal to the _{Q 0,} because the link current flows through the reflux diode, ZCS, a ZVS.
When Q ₁ is turned on, the DC link voltage is applied to the resonant reactor, Ir current increases linearly. At the same time, the current flowing through the diode portion of the Q ₀ decreases linearly by Ir min.
[0019]
Mode 3:
This mode is a DC link resonance mode. In mode 2, when the resonant reactor current Ir increases and becomes equal to the load current I _S1 , Q ₀ is naturally turned off and transitions to this mode. In this case, since the DC link is disconnected from the DC power source, a resonance action occurs between the resonance reactor Lr and the capacitor Cr, and the DC link voltage Vr drops to zero due to resonance. At the same time, the Lr current rises to the maximum value due to resonance.
[0020]
Mode 4:
This mode is a DC voltage zero voltage clamp mode. When the voltage of the resonance capacitor Cr decreases and reaches zero, the mode is changed to this mode. Although the DC link voltage tends to drop further, the clamp diode D becomes conductive and the link voltage is clamped to zero. In this case, since the voltage across Lr is zero, the Lr current Ir is maintained at a constant value at the maximum value, the clamp diode D continues to conduct, and if not, the DC link voltage continues to be clamped to zero forever. If a switching signal is given to the switching element of the main converter during this period, it is clear that the switching is ZVS.
[0021]
Mode 5:
This mode is a mode in which Ir, which is an Lr current, decreases. After primary transducer has performed switching, by providing an OFF signal to Q _1, a transition to this mode. Off operation of the Q ₁ is a ZVS because of its parasitic capacitance. When Q ₁ is turned off, the current flowing through the transistor Q ₁ is moved to the return diode of Q _2, it flows into the DC power supply. When the Lr current is completely commutated to _{Q 2,} it gives an ON signal to the _{Q 2.} In this case, since the freewheeling diode of _{Q 2} is already conducting, the ON operation _{Q 2} is ZCS, a ZVS.
When Q ₂ is turned on, the terminal voltage in the resonant reactor Lr so the -Vdc, Lr current Ir decreases linearly. Until the current is reduced to zero, freewheeling diode of Q ₂ is continuously conductive.
[0022]
Mode 6:
This mode is a mode in which Ir, which is an Lr current, increases in the reverse direction. In the previous mode, when Ir decreases and reaches zero, a transition is made to this mode. In this case, the return diode is off Q _2, although current Ir decreases further, changes polarity, through the transistor of Q _2, increases linearly in the opposite direction. At the same time, the current flowing through the clamp diode D decreases linearly.
[0023]
Mode 7:
This mode is an Lr, Cr resonance mode. In the previous mode, when the Lr reverse current increases, the current of the clamp diode D decreases, and transitions to this mode when it reaches zero. In this case, since the clamp diode D is turned off, the continuously increasing Lr reverse current starts to flow through the resonance capacitor Cr, enters the Lr, Cr resonance state, and rises due to resonance until the DC link voltage reaches the DC power supply voltage Vdc. .
[0024]
Mode 8:
In this mode, the DC link voltage Vr is clamped to Vdc. When the DC link voltage rises due to resonance and reaches the DC power supply voltage Vdc, it is clamped by the freewheeling diode of Q ₀ and transitions to this mode. In this case, since the voltage across the Lr is zero and the Lr current is maintained by the conduction of the freewheeling diode of Q ₀ , the DC link voltage Vr continues to be clamped by the DC power supply voltage Vdc if nothing is done. During this time, if you give the on signal to the _{Q 0,} in the conducting state of the freewheeling diode of _{Q 0,} the ON operation ZVS, a ZCS.
[0025]
Mode 9:
This mode is an Lr current reduction mode. In the DC link voltage clamped state before mode, by providing an OFF signal to Q _2, a transition to this mode. In this case, the off operation of the _{Q 2} is the ZVS in the parasitic capacitor. When Q ₂ is turned off, the current flowing through the Q ₂ is moved to the return diode of Q _1, since Lr is the DC supply voltage Vdc of the current direction and the opposite direction is applied linearly in Lr current Ir towards zero direction To decrease. At the same time, the current flowing through the freewheeling diode of Q ₀ decreases linearly.
[0026]
Mode 10:
This mode is a mode in which Ir, which is an Lr current, decreases. In the previous mode, when Ir decreases and reaches zero, it transitions to this mode. In this case, the diode portion of the Q ₀ is turned off, current starts to flow in the transistor section increases linearly. This condition Lr current becomes zero, until Q ₀ current matches the load current. That is, the commutation operation is completed and continues until the next steady state is reached.
[0027]
The above is the principle of commutation operation when the auxiliary resonant circuit of the present invention is used, and it can be seen that the switching operations of the main converter and the auxiliary circuit are all ZVS or ZCS. By repeating the above auxiliary switching operation every time a request from the switching operation of the main converter comes, the occurrence of switching loss and electromagnetic noise can be suppressed to the maximum.
[0028]
In evaluating the performance of the ZVS circuit, it is natural that whether the terminal voltage of the switching element is zero or not is important during the switching operation, but this is specifically whether the terminal voltage can reach zero. It can be evaluated by whether or not the period of staying at zero is sufficient.
In the case of the present invention, this is zero when the main switching element is switched in the DC link voltage decreasing mode, or can the DC power supply voltage Vdc be reached when the auxiliary switching element Q0 is turned on in the recovery mode? How much and how much can stop.
As described above with respect to the commutation operation transition, in the DC link descending mode, if the ON signal is continuously supplied to the auxiliary switching element Q1 in the operation modes 3 and 4, the link voltage can surely reach zero, and semipermanently zero. Can be maintained.
In the DC link voltage recovery mode, the same result can be obtained if the ON signal is continuously supplied to the auxiliary switching element Q2 in the operation modes 7 and 8.
That is, in the resonance type conversion device of the present invention, it is clear that the zero voltage mode is a stable mode, and the ZVS operation can be performed reliably and with sufficient margin.
[0029]
Hereinafter, the determination of the output timing of the switching signal during the commutation operation will be described in detail.
As explained in the above-mentioned commutation principle, in the present invention, the zero voltage holding period for ZVS can be freely adjusted. Therefore, the output of the switching signal of the switching element of the auxiliary circuit is given a margin and the output timing can be easily determined. It is.
Since the switching timing of the main switching element (Q _s ) is determined from the system control process, it is necessary to determine the subsequent switching timing of each auxiliary element using this as a reference point.
[0030]
From the operation waveform diagram of FIG. 4, the timing for turning off Q ₁ (starting the DC link voltage recovery mode) may be after the switching timing of the main switching element Q _s , and turning on Q ₂ is appropriate after Q ₁ is reliably turned off. timing well, also, it is clear that the off Q ₂ 'is good if subsequent oN Q _0.
Therefore, the Q ₁ on Q ₀ off (commutation start) timing (t ₁ ) and the Q ₀ on timing (t ₂ ) from the DC link voltage recovery mode start timing before the Q _s switching timing may be determined.
[0031]
From the arbitrary nature of the period of mode 4 and mode 8 (zero voltage clamp period),
t _1> Mode 2 + mode 3 time _{t 2>} mode 5+ mode may it can be seen that satisfies the 6+ mode 7 times.
When the load current before Q _s switching is I _s1 and the load current after switching is I _s2 , the time of each mode is obtained as follows.
[0032]

Therefore, t ₁ and t ₂ may satisfy the following conditions.

[0033]
Here, since I _s1 , I _s2 , and V _dc are obtained from the sensor signal _attached to the main converter, it can be seen that the operation timing of the auxiliary switching circuit can be determined.
Further, if the timings t ₁ and t ₂ are set to be larger than the calculated value on the right side, the reliability of the ZVS operation can be further improved.
[0034]
【The invention's effect】
As described above, by using the auxiliary resonant circuit of the present invention, it is possible to configure a soft switching converter with a small number of parts, low cost, and high reliability.
In addition, the auxiliary switching timing is determined without the need for an additional sensor for operating the resonant circuit, allowing for a large margin. In addition to the low switching loss and low electromagnetic noise characteristics inherent in the resonant converter, it is environmentally friendly. A power conversion system can be realized and is extremely useful in practice.
[Brief description of the drawings]
FIG. 1 is a diagram showing a main circuit configuration of a resonance type power converter using an auxiliary resonance circuit of the present invention.
FIG. 2 is an example of a main circuit diagram of a three-phase power converter for explaining the prior art.
FIG. 3 is a main circuit equivalent model for explaining the principle of the present invention;
FIG. 4 shows signal waveforms and operation waveforms during commutation of the resonance circuit of the present invention.
FIG. 5 is an operation transition diagram at the time of commutation in the resonance converter of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Multiphase alternating current power supply 2 Multiphase converter apparatus 3 Auxiliary resonance circuit 4,5,6,12 of this invention Semiconductor switching element 7 Resonant reactor 8 Voltage smoothing DC capacitor 9 Multiphase inverter apparatus 10 Multiphase alternating current load 11 DC voltage Source 13 Equivalent model of main converter 14 Equivalent capacitor for resonance 15 Equivalent clamp diode 16 Equivalent current source Q ₀ , Q ₁ , Q ₂ Switching element Qs of auxiliary resonance circuit of the present invention Main switching element D of main converter Equivalent clamp diode V _dc DC voltage source voltage value I _s1 , I _s2 Equivalent load current before and after switching of main converter L _r Reactance value of resonance reactor C _r Resonance equivalent capacitor capacitance value V _r DC link voltage value I _r Resonant reactor current t ₁ Commutation start time t ₂ DC link voltage recovery start to Q ₀ on time

Claims (1)

In a DC link of a semiconductor power conversion device that converts power from single or multiple multiphase AC to DC, or from DC to single or multiple multiphase AC,
A first semiconductor switching element that electrically cuts off a DC link and a DC power supply or a DC capacitor having an equivalent function thereto, and a second semiconductor switch connected in series with each other and connected in parallel with the DC power supply or the DC capacitor And a third semiconductor switching element, and a resonance reactor inserted between the interconnection point of the two semiconductor switching elements and the DC link connection point of the first semiconductor switching element. Auxiliary resonant circuit.

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